Patent Publication Number: US-7708372-B2

Title: Inkjet nozzle with ink feed channels etched from back of wafer

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This Application is a Continuation-in-Part of U.S. Ser. No. 10/407,212, filed on Apr. 7, 2003, now issued U.S. Pat. No. 7,416,280, which is a Continuation Application of U.S. Ser. No. 09/113,122, filed on Jul. 10, 1998, now issued U.S. Pat. No. 6,557,997. The following Australian provisional patent applications are hereby incorporated by reference. For the purposes of location and identification, US patents/patent applications identified by their US patent/patent application serial numbers are listed alongside the Australian applications from which the US patents/patent applications claim the right of priority. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Cross-Referenced 
                 U.S. Pat. No./U.S. patent application 
               
               
                   
                 Australian 
                 (Claiming Right of 
               
               
                   
                 Provisional Patent 
                 Priority from Australian 
               
               
                   
                 Application No. 
                 Provisional Application) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 PO7991 
                 6,750,901 
               
               
                   
                 PO8505 
                 6,476,863 
               
               
                   
                 PO7988 
                 6,788,336 
               
               
                   
                 PO9395 
                 6,322,181 
               
               
                   
                 PO8017 
                 6,597,817 
               
               
                   
                 PO8014 
                 6,227,648 
               
               
                   
                 PO8025 
                 6,727,948 
               
               
                   
                 PO8032 
                 6,690,419 
               
               
                   
                 PO7999 
                 6,727,951 
               
               
                   
                 PO8030 
                 6,196,541 
               
               
                   
                 PO7997 
                 6,195,150 
               
               
                   
                 PO7979 
                 6,362,868 
               
               
                   
                 PO7978 
                 6,831,681 
               
               
                   
                 PO7982 
                 6,431,669 
               
               
                   
                 PO7989 
                 6,362,869 
               
               
                   
                 PO8019 
                 6,472,052 
               
               
                   
                 PO7980 
                 6,356,715 
               
               
                   
                 PO8018 
                 6,894,694 
               
               
                   
                 PO7938 
                 6,636,216 
               
               
                   
                 PO8016 
                 6,366,693 
               
               
                   
                 PO8024 
                 6,329,990 
               
               
                   
                 PO7939 
                 6,459,495 
               
               
                   
                 PO8501 
                 6,137,500 
               
               
                   
                 PO8500 
                 6,690,416 
               
               
                   
                 PO7987 
                 7,050,143 
               
               
                   
                 PO8022 
                 6,398,328 
               
               
                   
                 PO8497 
                 7,110,024 
               
               
                   
                 PO8020 
                 6,431,704 
               
               
                   
                 PO8504 
                 6,879,341 
               
               
                   
                 PO8000 
                 6,415,054 
               
               
                   
                 PO7934 
                 6,665,454 
               
               
                   
                 PO7990 
                 6,542,645 
               
               
                   
                 PO8499 
                 6,486,886 
               
               
                   
                 PO8502 
                 6,381,361 
               
               
                   
                 PO7981 
                 6,317,192 
               
               
                   
                 PO7986 
                 6,850,274 
               
               
                   
                 PO7983 
                 09/113,054 
               
               
                   
                 PO8026 
                 6,646,757 
               
               
                   
                 PO8028 
                 6,624,848 
               
               
                   
                 PO9394 
                 6,357,135 
               
               
                   
                 PO9397 
                 6,271,931 
               
               
                   
                 PO9398 
                 6,353,772 
               
               
                   
                 PO9399 
                 6,106,147 
               
               
                   
                 PO9400 
                 6,665,008 
               
               
                   
                 PO9401 
                 6,304,291 
               
               
                   
                 PO9403 
                 6,305,770 
               
               
                   
                 PO9405 
                 6,289,262 
               
               
                   
                 PP0959 
                 6,315,200 
               
               
                   
                 PP1397 
                 6,217,165 
               
               
                   
                 PP2370 
                 6,786,420 
               
               
                   
                 PO8003 
                 6,350,023 
               
               
                   
                 PO8005 
                 6,318,849 
               
               
                   
                 PO8066 
                 6,227,652 
               
               
                   
                 PO8072 
                 6,213,588 
               
               
                   
                 PO8040 
                 6,213,589 
               
               
                   
                 PO8071 
                 6,231,163 
               
               
                   
                 PO8047 
                 6,247,795 
               
               
                   
                 PO8035 
                 6,394,581 
               
               
                   
                 PO8044 
                 6,244,691 
               
               
                   
                 PO8063 
                 6,257,704 
               
               
                   
                 PO8057 
                 6,416,168 
               
               
                   
                 PO8056 
                 6,220,694 
               
               
                   
                 PO8069 
                 6,257,705 
               
               
                   
                 PO8049 
                 6,247,794 
               
               
                   
                 PO8036 
                 6,234,610 
               
               
                   
                 PO8048 
                 6,247,793 
               
               
                   
                 PO8070 
                 6,264,306 
               
               
                   
                 PO8067 
                 6,241,342 
               
               
                   
                 PO8001 
                 6,247,792 
               
               
                   
                 PO8038 
                 6,264,307 
               
               
                   
                 PO8033 
                 6,254,220 
               
               
                   
                 PO8002 
                 6,234,611 
               
               
                   
                 PO8068 
                 6,302,528 
               
               
                   
                 PO8062 
                 6,283,582 
               
               
                   
                 PO8034 
                 6,239,821 
               
               
                   
                 PO8039 
                 6,338,547 
               
               
                   
                 PO8041 
                 6,247,796 
               
               
                   
                 PO8004 
                 6,557,977 
               
               
                   
                 PO8037 
                 6,390,603 
               
               
                   
                 PO8043 
                 6,362,843 
               
               
                   
                 PO8042 
                 6,293,653 
               
               
                   
                 PO8064 
                 6,312,107 
               
               
                   
                 PO9389 
                 6,227,653 
               
               
                   
                 PO9391 
                 6,234,609 
               
               
                   
                 PP0888 
                 6,238,040 
               
               
                   
                 PP0891 
                 6,188,415 
               
               
                   
                 PP0890 
                 6,227,654 
               
               
                   
                 PP0873 
                 6,209,989 
               
               
                   
                 PP0993 
                 6,247,791 
               
               
                   
                 PP0890 
                 6,336,710 
               
               
                   
                 PP1398 
                 6,217,153 
               
               
                   
                 PP2592 
                 6,416,167 
               
               
                   
                 PP2593 
                 6,243,113 
               
               
                   
                 PP3991 
                 6,283,581 
               
               
                   
                 PP3987 
                 6,247,790 
               
               
                   
                 PP3985 
                 6,260,953 
               
               
                   
                 PP3983 
                 6,267,469 
               
               
                   
                 PO7935 
                 6,224,780 
               
               
                   
                 PO7936 
                 6,235,212 
               
               
                   
                 PO7937 
                 6,280,643 
               
               
                   
                 PO8061 
                 6,284,147 
               
               
                   
                 PO8054 
                 6,214,244 
               
               
                   
                 PO8065 
                 6,071,750 
               
               
                   
                 PO8055 
                 6,267,905 
               
               
                   
                 PO8053 
                 6,251,298 
               
               
                   
                 PO8078 
                 6,258,285 
               
               
                   
                 PO7933 
                 6,225,138 
               
               
                   
                 PO7950 
                 6,241,904 
               
               
                   
                 PO7949 
                 6,299,786 
               
               
                   
                 PO8060 
                 6,866,789 
               
               
                   
                 PO8059 
                 6,231,773 
               
               
                   
                 PO8073 
                 6,190,931 
               
               
                   
                 PO8076 
                 6,248,249 
               
               
                   
                 PO8075 
                 6,290,862 
               
               
                   
                 PO8079 
                 6,241,906 
               
               
                   
                 PO8050 
                 6,565,762 
               
               
                   
                 PO8052 
                 6,241,905 
               
               
                   
                 PO7948 
                 6,451,216 
               
               
                   
                 PO7951 
                 6,231,772 
               
               
                   
                 PO8074 
                 6,274,056 
               
               
                   
                 PO7941 
                 6,290,861 
               
               
                   
                 PO8077 
                 6,248,248 
               
               
                   
                 PO8058 
                 6,306,671 
               
               
                   
                 PO8051 
                 6,331,258 
               
               
                   
                 PO8045 
                 6,110,754 
               
               
                   
                 PO7952 
                 6,294,101 
               
               
                   
                 PO8046 
                 6,416,679 
               
               
                   
                 PO9390 
                 6,264,849 
               
               
                   
                 PO9392 
                 6,254,793 
               
               
                   
                 PP0889 
                 6,235,211 
               
               
                   
                 PP0887 
                 6,491,833 
               
               
                   
                 PP0882 
                 6,264,850 
               
               
                   
                 PP0874 
                 6,258,284 
               
               
                   
                 PP1396 
                 6,312,615 
               
               
                   
                 PP3989 
                 6,228,668 
               
               
                   
                 PP2591 
                 6,180,427 
               
               
                   
                 PP3990 
                 6,171,875 
               
               
                   
                 PP3986 
                 6,267,904 
               
               
                   
                 PP3984 
                 6,245,247 
               
               
                   
                 PP3982 
                 6,315,914 
               
               
                   
                 PP0895 
                 6,231,148 
               
               
                   
                 PP0869 
                 6,293,658 
               
               
                   
                 PP0887 
                 6,614,560 
               
               
                   
                 PP0885 
                 6,238,033 
               
               
                   
                 PP0884 
                 6,312,070 
               
               
                   
                 PP0886 
                 6,238,111 
               
               
                   
                 PP0877 
                 6,378,970 
               
               
                   
                 PP0878 
                 6,196,739 
               
               
                   
                 PP0883 
                 6,270,182 
               
               
                   
                 PP0880 
                 6,152,619 
               
               
                   
                 PO8006 
                 6,087,638 
               
               
                   
                 PO8007 
                 6,340,222 
               
               
                   
                 PO8010 
                 6,041,600 
               
               
                   
                 PO8011 
                 6,299,300 
               
               
                   
                 PO7947 
                 6,067,797 
               
               
                   
                 PO7944 
                 6,286,935 
               
               
                   
                 PO7946 
                 6,044,646 
               
               
                   
                 PP0894 
                 6,382,769 
               
               
                   
                   
               
            
           
         
       
     
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE INVENTION 
     The present invention relates to the operation and construction of an ink jet printer device. 
     BACKGROUND OF THE INVENTION 
     Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc. 
     In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature. 
     Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988). 
     Ink Jet printers themselves come in many different forms. The utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing. 
     U.S. Pat. No. 3,596,275 by Sweet also discloses a process of continuous ink jet printing including a step wherein the ink jet stream is modulated by a high frequency electrostatic field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al). 
     Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element. 
     Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclose ink jet printing techniques which rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electrothermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard. 
     As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables. 
     A compact design requires close nozzle spacing. One complication with high nozzle density on a printhead is the ink, power and print data supply to each and every nozzle. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention provides an inkjet drop ejection apparatus comprising: 
     a wafer substrate having a front side and a back side opposite the front side; 
     an array of ink ejection nozzles formed on the front side by lithographic etching and deposition techniques; and, 
     a plurality elongate ink feed channels etched from the back side for supplying ink to the nozzles. 
     Etching the ink feed channels from the back surface of the wafer removes the need for ink feed channels beside the chambers. This provides more room for the power and print data connections to each nozzle along the front surface of the wafer. Individual ink feed channels for each nozzle eliminates fluidic cross talk between adjacent nozzles. An ink feed channel that supplies several nozzles from the side of each chamber needs to incorporate special features such as pinch points to deal with fluidic cross talk. However, a back etched ink feed channel can supply several nozzles without fluidic cross talk (e.g. IJ37 discussed below). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment of the present invention; 
         FIG. 2  is a ting diagram illustrating the operation of a preferred embodiment; 
         FIG. 3  is a cross-sectional top view of a single ink nozzle constructed in accordance with a preferred embodiment of the present invention; 
         FIG. 4  provides a legend of the materials indicated in  FIGS. 5 to 21 ; 
         FIG. 5  to  FIG. 21  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 22  is a perspective cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 23  is a close-up perspective cross-sectional view (portion A of  FIG. 22 ), of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 24  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 25  provides a legend of the materials indicated in  FIGS. 26 to 36 ; 
         FIG. 26  to  FIG. 36  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 37  is cross-sectional view, partly in section, of a single ink jet nozzle constructed in accordance with an embodiment of the present invention; 
         FIG. 38  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with an embodiment of the present invention; 
         FIG. 39  provides a legend of the materials indicated in  FIGS. 40 to 55 ; 
         FIG. 40  to  FIG. 55  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 56  is a perspective view through a single ink jet nozzle constructed in accordance with a preferred embodiment of the present invention; 
         FIG. 57  is a schematic cross-sectional view of the ink nozzle constructed in accordance with a preferred embodiment of the present invention, with the actuator in its quiescent state; 
         FIG. 58  is a schematic cross-sectional view of the ink nozzle immediately after activation of the actuator, 
         FIG. 59  is a schematic cross-sectional view illustrating the ink jet nozzle ready for firing; 
         FIG. 60  is a schematic cross-sectional view of the ink nozzle immediately after deactivation of the actuator; 
         FIG. 61  is a perspective view, in part exploded, of the actuator of a single ink jet nozzle constructed in accordance with a preferred embodiment of the present invention; 
         FIG. 62  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment of the present invention; 
         FIG. 63  provides a legend of the materials indicated in  FIGS. 64 to 77 ; 
         FIG. 64  to  FIG. 77  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 78  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 79  is a perspective view, in part in section, of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 80  provides a legend of the materials indicated in  FIG. 81 to 97 ; 
         FIG. 81  to  FIG. 97  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 98  is a cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment in its quiescent state; 
         FIG. 99  is a cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment, illustrating the state upon activation of the actuator; 
         FIG. 100  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 101  provides a legend of the materials indicated in  FIGS. 102 to 112 ; 
         FIG. 102  to  FIG. 112  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 113  is a perspective cross-sectional view of a single ink jet nozzle apparatus constructed in accordance with a preferred embodiment; 
         FIG. 114  is an exploded perspective view illustrating the construction of the ink jet nozzle apparatus in accordance with a preferred embodiment; 
         FIG. 115  provides a legend of the materials indicated in  FIG. 116 to 130 ; 
         FIG. 116  to  FIG. 130  illustrate sectional views of the manufacturing steps in one form of construction of the ink jet nozzle apparatus; 
         FIG. 131  is a perspective view of a single ink jet nozzle constructed in accordance with a preferred embodiment, with the shutter means in its closed position; 
         FIG. 132  is a perspective view of a single ink jet nozzle constructed in accordance with a preferred embodiment, with the shutter means in its open position; 
         FIG. 133  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 134  provides a legend of the materials indicated in  FIG. 135 to 156 ; 
         FIG. 135  to  FIG. 156  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 157  is a cross-sectional schematic diagram of the inkjet nozzle chamber in its quiescent state; 
         FIG. 158  is a cross-sectional schematic diagram of the inkjet nozzle chamber during activation of the first actuator to eject ink; 
         FIG. 159  is a cross-sectional schematic diagram of the inkjet nozzle chamber after deactivation of the first actuator; 
         FIG. 160  is a cross-sectional schematic diagram of the inkjet nozzle chamber during activation of the second actuator to refill the chamber; 
         FIG. 161  is a cross-sectional schematic diagram of the inkjet nozzle chamber after deactivation of the actuator to refill the chamber; 
         FIG. 162  is a cross-sectional schematic diagram of the inkjet nozzle chamber during simultaneous activation of the ejection actuator whilst deactivation of the pump actuator; 
         FIG. 163  is a top view cross-sectional diagram of the inkjet nozzle chamber; and 
         FIG. 164  is an exploded perspective view illustrating the construction of the inkjet nozzle chamber in accordance with a preferred embodiment. 
         FIG. 165  provides a legend of the materials indicated in  FIG. 166 to 178 ; 
         FIG. 166  to  FIG. 178  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 179  is a perspective, partly sectional view of a single nozzle arrangement for an ink jet printhead in its quiescent position constructed in accordance with a preferred embodiment; 
         FIG. 180  is a perspective, partly sectional view of the nozzle arrangement in its firing position constructed in accordance with a preferred embodiment; 
         FIG. 181  is an exploded perspective illustrating the construction of the nozzle arrangement in accordance with a preferred embodiment; 
         FIG. 182  provides a legend of the materials indicated in  FIG. 183 to 197 ; 
         FIG. 183  to  FIG. 197  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 198  is a cross sectional view of a single ink jet nozzle as constructed in accordance with a preferred embodiment in its quiescent state; 
         FIG. 199  is a cross sectional view of a single ink jet nozzle as constructed in accordance with a preferred embodiment after reaching its stop position; 
         FIG. 200  is a cross sectional view of a single ink jet nozzle as constructed in accordance with a preferred embodiment in the keeper face position; 
         FIG. 201  is a cross sectional view of a single ink jet nozzle as constructed in accordance with a preferred embodiment after de-energising from the keeper level. 
         FIG. 202  is an exploded perspective view illustrating the construction of a preferred embodiment; 
         FIG. 203  is the cut out topside view of a single ink jet nozzle constructed in accordance with a preferred embodiment in the keeper level; 
         FIG. 204  provides a legend of the materials indicated in  FIGS. 205 to 224 ; 
         FIG. 205  to  FIG. 224  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 225  is a cut-out top view of an ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 226  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 227  provides a legend of the materials indicated in  FIG. 228 to 248 ; 
         FIG. 228  to  FIG. 248  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 249  is a cut-out top perspective view of the ink nozzle in accordance with a preferred embodiment of the present invention; 
         FIG. 250  is an exploded perspective view illustrating the shutter mechanism in accordance with a preferred embodiment of the present invention; 
         FIG. 251  is a top cross-sectional perspective view of the ink nozzle constructed in accordance with a preferred embodiment of the present invention; 
         FIG. 252  provides a legend of the materials indicated in  FIGS. 253 to 266 ; 
         FIG. 253  to  FIG. 267  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 268  is a perspective cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 269  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 270  provides a legend of the materials indicated in  FIG. 271 to 289 ; 
         FIG. 271  to  FIG. 289  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 290  is a perspective view of a single ink jet nozzle constructed in accordance with a preferred embodiment, in its closed position; 
         FIG. 291  is a perspective view of a single ink jet nozzle constructed in accordance with a preferred embodiment, in its open position; 
         FIG. 292  is a perspective, cross-sectional view taken along the line I-I of  FIG. 291 , of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 293  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 294  provides a legend of the materials indicated in  FIGS. 295 to 316 ; 
         FIG. 295  to  FIG. 316  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 317  is a schematic top view of a single ink jet nozzle chamber apparatus constructed in accordance with a preferred embodiment; 
         FIG. 318  is a top cross-sectional view of a single ink jet nozzle chamber apparatus with the diaphragm in its activated stage; 
         FIG. 319  is a schematic cross-sectional view illustrating the exposure of a resist layer through a halftone mask; 
         FIG. 320  is a schematic cross-sectional view illustrating the resist layer after development exhibiting a corrugated pattern; 
         FIG. 321  is a schematic cross-sectional view illustrating the transfer of the corugated pattern onto the substrate by etching; 
         FIG. 322  is a schematic cross-sectional view illustrating the construction of an embedded, corrugated, conduction layer; and 
         FIG. 323  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment. 
         FIG. 324  is a perspective view of the heater traces used in a single ink jet nozzle constructed in accordance with a preferred embodiment. 
         FIG. 325  provides a legend of the materials indicated in  FIG. 326 to 336 ; 
         FIG. 326  to  FIG. 337  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 338  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 339  is a perspective view, partly in section, of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 340  provides a legend of the materials indicated in  FIG. 341 to 353 ; 
         FIG. 341  to  FIG. 353  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 354  is a top view of a single ink nozzle chamber constructed in accordance with the principals of a preferred embodiment, with the shutter in a close state; 
         FIG. 355  is a top view of a single ink nozzle chamber as constructed in accordance with a preferred embodiment with the shutter in an open state; 
         FIG. 356  is an exploded perspective view illustrating the construction of a single ink nozzle chamber in accordance with a preferred embodiment of the present invention; 
         FIG. 357  provides a legend of the materials indicated in  FIGS. 358 to 370 ; 
         FIG. 358  to  FIG. 370  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 371  is a perspective view of the top of a print nozzle pair; 
         FIG. 372  illustrates a partial, cross-sectional view of one shutter and one arm of the thermocouple utilized in a preferred embodiment; 
         FIG. 373  is a timing diagram illustrating the operation of a preferred embodiment; 
         FIG. 374  illustrates an exploded perspective view of a pair of print nozzles constructed in accordance with a preferred embodiment. 
         FIG. 375  provides a legend of the materials indicated in  FIGS. 376 to 390 ; 
         FIG. 376  to  FIG. 390  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 391  is a cross-sectional perspective view of a single ink nozzle arrangement constructed in accordance with a preferred embodiment, with the actuator in its quiescent state; 
         FIG. 392  is a cross-sectional perspective view of a single ink nozzle arrangement constructed in accordance with a preferred embodiment, in its activated state; 
         FIG. 393  is an exploded perspective view illustrating the construction of a single ink nozzle in accordance with a preferred embodiment of the present invention; 
         FIG. 394  provides a legend of the materials indicated in  FIG. 395 to 408 ; 
         FIG. 395  to  FIG. 408  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 409  is a schematic cross-sectional view illustrating an ink jet printing mechanism constructed in accordance with a preferred embodiment; 
         FIG. 410  is a perspective view of a single nozzle arrangement constructed in accordance with a preferred embodiment; 
         FIG. 411  is a timing diagram illustrating the various phases of the ink jet printing mechanism; 
         FIG. 412  is a cross-sectional schematic diagram illustrating the nozzle arrangement in its idle phase; 
         FIG. 413  is a cross-sectional schematic diagram illustrating the nozzle arrangement in its ejection phase; 
         FIG. 414  is a cross-sectional schematic diagram of the nozzle arrangement in its separation phase; 
         FIG. 415  is a schematic cross-sectional diagram illustrating the nozzle arrangement in its refilling phase; 
         FIG. 416  is a cross-sectional schematic diagram illustrating the nozzle arrangement after returning to its idle phase; 
         FIG. 417  is an exploded perspective view illustrating the construction of the nozzle arrangement in accordance with a preferred embodiment of the present invention; 
         FIG. 418  provides a legend of the materials indicated in  FIGS. 419 to 430 ; 
         FIG. 419  to  FIG. 430  illustrate sectional views of the manufacturing steps in one form of construction of the nozzle arrangement; 
         FIG. 431  is a perspective view of the actuator portions of a single ink jet nozzle in a quiescent position, constructed in accordance with a preferred embodiment; 
         FIG. 432  is a perspective view of the actuator portions of a single ink jet nozzle in a quiescent position constructed in accordance with a preferred embodiment; 
         FIG. 433  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 434  provides a legend of the materials indicated in  FIG. 435 to 446 ; 
         FIG. 435  to  FIG. 446  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 447  is a cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment, in its quiescent state; 
         FIG. 448  is a cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment, in its activated state; 
         FIG. 449  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 450  is a cross-sectional schematic diagram illustrating the construction of a corrugated conductive layer in accordance with a preferred embodiment of the present invention; 
         FIG. 451  is a schematic cross-sectional diagram illustrating the development of a resist material through a half-toned mask utilized in the fabrication of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 452  is a top view of the conductive layer only of the thermal actuator of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 453  provides a legend of the materials indicated in  FIG. 454 to 465 ; 
         FIG. 454  to  FIG. 465  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 466  is a cut out topside view illustrating two adjoining inject nozzles constructed in accordance with a preferred embodiment; 
         FIG. 467  is an exploded perspective view illustrating the construction of a single inject nozzle in accordance with a preferred embodiment; 
         FIG. 468  is a sectional view through the nozzles of  FIG. 466 ; 
         FIG. 469  is a sectional view through the line IV-IV′ of  FIG. 468 ; 
         FIG. 470  provides a legend of the materials indicated in  FIG. 471 to 484 ; 
         FIG. 471  to  FIG. 484  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 485  is a perspective cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 486  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 487  provides a legend of the materials indicated in  FIGS. 488 to 499 ; 
         FIGS. 488  to  FIG. 499  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 500  is an exploded perspective view of a single ink jet nozzle as constructed in accordance with a preferred embodiment; 
         FIG. 501  is a top cross sectional view of a single ink jet nozzle in its quiescent state taken along line A-A in  FIG. 500 ; 
         FIG. 502  is a top cross sectional view of a single ink jet nozzle in its actuated state taken along line A-A in  FIG. 500 ; 
         FIG. 503  provides a legend of the materials indicated in  FIG. 504 to 514 ; 
         FIG. 504  to  FIG. 514  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 515  is a perspective view partly in sections of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 516  is an exploded perspective view partly in section illustrating the construction of a single ink nozzle in accordance with a preferred embodiment of the present invention; 
         FIG. 517  provides a legend of the materials indicated in  FIG. 518 to 530 ; 
         FIG. 518  to  FIG. 530  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 531  is an exploded perspective view illustrating the construction of a single inkjet nozzle arrangement in accordance with a preferred embodiment of the present invention; 
         FIG. 532  is a plan view taken from above of relevant portions of an ink jet nozzle arrangement in accordance with a preferred embodiment; 
         FIG. 533  is a cross-sectional view through a single nozzle arrangement, illustrating a drop being ejected out of the nozzle aperture; 
         FIG. 534  provides a legend of the materials indicated in  FIG. 345 to 547 ; 
         FIG. 535  to  FIG. 547  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet nozzle arrangement; 
         FIG. 548  is a schematic cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment, in its quiescent state; 
         FIG. 549  is a cross-sectional schematic diagram of a single ink jet nozzle constructed in accordance with a preferred embodiment, illustrating the activated state; 
         FIG. 550  is a schematic cross-sectional diagram of a single ink jet nozzle illustrating the deactivation state; 
         FIG. 551  is a schematic cross-sectional diagram of a single ink jet nozzle constructed in accordance with a preferred embodiment, after returning into its quiescent state; 
         FIG. 552  is a schematic, cross-sectional perspective diagram of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 553  is a perspective view of a group of ink jet nozzles; 
         FIG. 554  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 555  provides a legend of the materials indicated in  FIG. 556 to 567 ; 
         FIG. 556  to  FIG. 567  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 568  is a schematic cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 569  is a schematic cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment, with the thermal actuator in its activated state; 
         FIG. 570  is a schematic diagram of the conductive layer utilized in the thermal actuator of the ink jet nozzle constructed in accordance with a preferred embodiment; 
         FIG. 571  is a close-up perspective view of portion A of  FIG. 570 ; 
         FIG. 572  is a cross-sectional schematic diagram illustrating the construction of a corrugated conductive layer in accordance with a preferred embodiment of the present invention; 
         FIG. 573  is a schematic cross-sectional diagram illustrating the development of a resist material through a half-toned mask utilized in the fabrication of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 574  is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment; 
         FIG. 575  is a perspective view of a section of an ink jet printhead configuration utilizing ink jet nozzles constructed in accordance with a preferred embodiment. 
         FIG. 576  provides a legend of the materials indicated in  FIGS. 577 to 590 ; 
         FIG. 577  to  FIG. 590  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIGS. 591-593  illustrate basic operation of a preferred embodiments of nozzle arrangements of the invention; 
         FIG. 594  is a sectional view of a preferred embodiment of a nozzle arrangement of the invention; 
         FIG. 595  is an exploded perspective view of a preferred embodiment; 
         FIGS. 596-605  are cross-sectional views illustrating various steps in the construction of a preferred embodiment of the nozzle arrangement; 
         FIG. 606  illustrates a top view of an array of ink jet nozzle arrangements constructed in accordance with the principles of the present invention; 
         FIG. 607  provides a legend of the materials indicated in  FIG. 608 to 619 ; 
         FIG. 608  to  FIG. 619  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead having nozzle arrangements of the invention; 
         FIG. 620  illustrates a nozzle arrangement in accordance with the invention; 
         FIG. 621  is an exploded perspective view of the nozzle arrangement of  FIG. 1 ; 
         FIG. 622 to 624  illustrate the operation of the nozzle arrangement 
         FIG. 625  illustrates an array of nozzle arrangements for use with an inkjet printhead. 
         FIG. 626  provides a legend of the materials indicated in  FIG. 627 to 638 ; 
         FIG. 627  to  FIG. 638  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 639  illustrates a perspective view of an ink jet nozzle arrangement in accordance with a preferred embodiment; 
         FIG. 640  illustrates the arrangement of  FIG. 639  when the actuator is in an activated position; 
         FIG. 641  illustrates an exploded perspective view of the major components of a preferred embodiment; 
         FIG. 642  provides a legend of the materials indicated in  FIGS. 643 to 654 ; 
         FIG. 643  to  FIG. 654  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 655  illustrates a single ink ejection mechanism as constructed in accordance with the principles of a preferred embodiment; 
         FIG. 656  is a section through the line II-II of the actuator arm of  FIG. 655 ; 
         FIGS. 657-659  illustrate the basic operation of the ink ejection mechanism of a preferred embodiment; 
         FIG. 660  is an exploded perspective view of an ink ejection mechanism. 
         FIG. 661  provides a legend of the materials indicated in  FIGS. 662 to 676 ; 
         FIG. 662  to  FIG. 676  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 677  is a descriptive view of an ink ejection arrangement when in a quiescent state; 
         FIG. 678  is a descriptive view of an ejection arrangement when in an activated state; 
         FIG. 679  is an exploded perspective view of the different components of an ink ejection arrangement; 
         FIG. 680  illustrates a cross section through the line IV-IV of  FIG. 677 ; 
         FIGS. 681 to 700  illustrate the various manufacturing steps in the construction of a preferred embodiment; 
         FIG. 701  illustrates a portion of an array of ink ejection arrangements as constructed in accordance with a preferred embodiment. 
         FIG. 702  provides a legend of the materials indicated in  FIGS. 27 to 38 ; 
         FIGS. 703 to 714  illustrate sectional views of manufacturing steps of one form of construction of the ink ejection arrangement; 
         FIGS. 715-719  comprise schematic illustrations of the operation of a preferred embodiment; 
         FIG. 720  illustrates a side perspective view, of a single nozzle arrangement of a preferred embodiment. 
         FIG. 721  illustrates a perspective view, partly in section of a single nozzle arrangement of a preferred embodiment; 
         FIGS. 722-741  are cross sectional views of the processing steps in the construction of a preferred embodiment; 
         FIG. 742  illustrates a part of an array view of a portion of a printhead as constructed in accordance with the principles of the present invention; 
         FIG. 743  provides a legend of the materials indicated in  FIGS. 744 to 756 ; 
         FIG. 744  to  FIG. 758  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 759-763  illustrate schematically the principles operation of a preferred embodiment; 
         FIG. 764  is a perspective view, partly in section of one form of construction of a preferred embodiment; 
         FIGS. 765-782  illustrate various steps in the construction of a preferred embodiment; and 
         FIG. 783  illustrates an array view illustrating a portion of a printhead constructed in accordance with a preferred embodiment. 
         FIG. 784  provides a legend of the materials indicated in  FIGS. 785 to 800 ; 
         FIG. 785  to  FIG. 801  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 802-806  comprise schematic illustrations showing the operation of a preferred embodiment of a nozzle arrangement of this invention; 
         FIG. 807  illustrates a perspective view, of a single nozzle arrangement of a preferred embodiment; 
         FIG. 808  illustrates a perspective view, partly in section of a single nozzle arrangement of a preferred embodiment; 
         FIG. 809-827  are cross sectional views of the processing steps in the construction of a preferred embodiment; 
         FIG. 828  illustrates a part of an array view of a printhead as constructed in accordance with the principles of the present invention; 
         FIG. 829  provides a legend of the materials indicated in  FIG. 830 to 848 ; 
         FIG. 830  to  FIG. 848  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead including nozzle arrangements of this invention; 
         FIGS. 849-851  are schematic illustrations of the operational principles of a preferred embodiment; 
         FIG. 852  illustrates a perspective view, partly in section of a single inkjet nozzle of a preferred embodiment; 
         FIG. 853  is a side perspective view of a single ink jet nozzle of a preferred embodiment; 
         FIGS. 854-863  illustrate the various manufacturing processing steps in the construction of a preferred embodiment; 
         FIG. 864  illustrates a portion of an array view of a printhead having a large number of nozzles, each constructed in accordance with the principles of the present invention. 
         FIG. 865  provides a legend of the materials indicated in  FIGS. 866 to 876 ; 
         FIG. 866  to  FIG. 876  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIGS. 877-879  illustrate the basic operational principles of a preferred embodiment; 
         FIG. 880  illustrates a three dimensional view of a single ink jet nozzle arrangement constructed in accordance with a preferred embodiment; 
         FIG. 881  illustrates an array of the nozzle arrangements of  FIG. 880 ; 
         FIG. 882  shows a table to be used with reference to  FIGS. 883 to 892 ; 
         FIGS. 883 to 892  show various stages in the manufacture of the ink jet nozzle arrangement of  FIG. 880 ; 
         FIGS. 893-895  illustrate the operational principles of a preferred embodiment; 
         FIG. 896  is a side perspective view of a single nozzle arrangement of a preferred embodiment; 
         FIG. 897  illustrates a sectional side view of a single nozzle arrangement; 
         FIGS. 898 and 898  illustrate operational principles of a preferred embodiment; 
         FIGS. 900-907  illustrate the manufacturing steps in the construction of a preferred embodiment; 
         FIG. 908  illustrates a top plan view of a single nozzle; 
         FIG. 909  illustrates a portion of a single color printhead device; 
         FIG. 910  illustrates a portion of a three color printhead device; 
         FIG. 911  provides a legend of the materials indicated in  FIGS. 912 to 921 ; 
         FIG. 912  to  FIG. 921  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIGS. 922-924  are schematic sectional views illustrating the operational principles of a preferred embodiment; 
         FIG. 925(   a ) and  FIG. 925(   b ) are again schematic sections illustrating the operational principles of the thermal actuator device; 
         FIG. 926  is a side perspective view, partly in section, of a single nozzle arrangement constructed in accordance with a preferred embodiments; 
         FIGS. 927-934  illustrate side perspective views, partly in section, illustrating the manufacturing steps of a preferred embodiments; and 
         FIG. 935  illustrates an array of ink jet nozzles formed in accordance with the manufacturing procedures of a preferred embodiment; 
         FIG. 936  provides a legend of the materials indicated in  FIGS. 937 to 944 ; 
         FIG. 937  to  FIG. 944  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIGS. 945-947  are schematic sectional views illustrating the operational principles of a preferred embodiment; 
         FIG. 948(   a ) and  FIG. 948(   b ) are again schematic sections illustrating the operational principles of the thermal actuator device; 
         FIG. 949  is a side perspective view, partly in section, of a single nozzle arrangement constructed in accordance with a preferred embodiments; 
         FIGS. 950-957  are side perspective views, partly in section, illustrating the manufacturing steps of a preferred embodiments; 
         FIG. 958  illustrates an array of ink jet nozzles formed in accordance with the manufacturing procedures of a preferred embodiment; 
         FIG. 959  provides a legend of the materials indicated in  FIG. 960 to 967 ; 
         FIG. 960  to  FIG. 967  illustrate sectional views of the manufacturing steps in one form of construction of a nozzle arrangement in accordance with the invention; 
         FIG. 968  to  FIG. 970  are schematic sectional views illustrating the operational principles of a preferred embodiment; 
         FIG. 971   a  and  FIG. 971   b  illustrate the operational principles of the thermal actuator of a preferred embodiment; 
         FIG. 972  is a side perspective view of a single nozzle arrangement of a preferred embodiment; 
         FIG. 973  illustrates an array view of a portion of a printhead constructed in accordance with the principles of a preferred embodiment. 
         FIG. 974  provides a legend of the materials indicated in  FIGS. 975 to 983 ; 
         FIG. 975  to  FIG. 984  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 985  to  FIG. 987  are schematic illustrations of the operation of an ink jet nozzle arrangement of an embodiment. 
         FIG. 988  illustrates a side perspective view, partly in section, of a single ink jet nozzle arrangement of an embodiment; 
         FIG. 989  provides a legend of the materials indicated in  FIG. 990 to 1005 ; 
         FIG. 990  to  FIG. 1005  illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle; 
         FIG. 1006  schematically illustrates a preferred embodiment of a single ink jet nozzle in a quiescent position; 
         FIG. 1007  schematically illustrates a preferred embodiment of a single inkjet nozzle in a firing position; 
         FIG. 1008  schematically illustrates a preferred embodiment of a single ink jet nozzle in a refilling position; 
         FIG. 1009  illustrates a bi-layer cooling process; 
         FIG. 1010  illustrates a single-layer cooling process; 
         FIG. 1011  is a top view of an aligned nozzle; 
         FIG. 1012  is a sectional view of an aligned nozzle; 
         FIG. 1013  is a top view of an aligned nozzle; 
         FIG. 1014  is a sectional view of an aligned nozzle; 
         FIG. 1015  is a sectional view of a process on constructing an ink jet nozzle; 
         FIG. 1016  is a sectional view of a process on constructing an ink jet nozzle after Chemical Mechanical Planarization; 
         FIG. 1017  illustrates the steps involved in the preferred embodiment in preheating the ink; 
         FIG. 1018  illustrates the normal printing clocking cycle; 
         FIG. 1019  illustrates the utilization of a preheating cycle; 
         FIG. 1020  illustrates a graph of likely print head operation temperature; 
         FIG. 1021  illustrates a graph of likely print head operation temperature; 
         FIG. 1022  illustrates one form of driving a print head for preheating 
         FIG. 1023  illustrates a sectional view of a portion of an initial wafer on which an ink jet nozzle structure is to be formed; 
         FIG. 1024  illustrates the mask for N-well processing; 
         FIG. 1025  illustrates a sectional view of a portion of the wafer after N-well processing; 
         FIG. 1026  illustrates a side perspective view partly in section of a single nozzle after N-well processing; 
         FIG. 1027  illustrates the active channel mask; 
         FIG. 1028  illustrates a sectional view of the field oxide; 
         FIG. 1029  illustrates a side perspective view partly in section of a single nozzle after field oxide deposition; 
         FIG. 1030  illustrates the poly mask; 
         FIG. 1031  illustrates a sectional view of the deposited poly; 
         FIG. 1032  illustrates a side perspective view partly in section of a single nozzle after poly deposition; 
         FIG. 1033  illustrates the n+ mask; 
         FIG. 1034  illustrates a sectional view of the n+ implant; 
         FIG. 1035  illustrates a side perspective view partly in section of a single nozzle after n+ implant; 
         FIG. 1036  illustrates the p+ mask; 
         FIG. 1037  illustrates a sectional view showing the effect of the p+ implant; 
         FIG. 1038  illustrates a side perspective view partly in section of a single nozzle after p+ implant; 
         FIG. 1039  illustrates the contacts mask; 
         FIG. 1040  illustrates a sectional view showing the effects of depositing ILD  1  and etching contact vias; 
         FIG. 1041  illustrates a side perspective view partly in section of a single nozzle after depositing ILD  1  and etching contact vias; 
         FIG. 1042  illustrates the Metal  1  mask; 
         FIG. 1043  illustrates a sectional view showing the effect of the metal deposition of the Metal  1  layer, 
         FIG. 1044  illustrates a side perspective view partly in section of a single nozzle after metal  1  deposition; 
         FIG. 1045  illustrates the Via  1  mask; 
         FIG. 1046  illustrates a sectional view showing the effects of depositing ILD  2  and etching contact vias; 
         FIG. 1047  illustrates the Metal  2  mask; 
         FIG. 1048  illustrates a sectional view showing the effects of depositing the Metal  2  layer; 
         FIG. 1049  illustrates a side perspective view partly in section of a single nozzle after metal  2  deposition; 
         FIG. 1050  illustrates the Via  2  mask; 
         FIG. 1051  illustrates a sectional view showing the effects of depositing ILD  3  and etching contact vias; 
         FIG. 1052  illustrates the Metal  3  mask; 
         FIG. 1053  illustrates a sectional view showing the effects of depositing the Metal  3  layer; 
         FIG. 1054  illustrates a side perspective view partly in section of a single nozzle after metal  3  deposition; 
         FIG. 1055  illustrates the Via  3  mask; 
         FIG. 1056  illustrates a sectional view showing the effects of depositing passivation oxide and nitride and etching vias; 
         FIG. 1057  illustrates a side perspective view partly in section of a single nozzle after depositing passivation oxide and nitride and etching vias; 
         FIG. 1058  illustrates the heater mask; 
         FIG. 1059  illustrates a sectional view showing the effect of depositing the heater titanium nitride layer; 
         FIG. 1060  illustrates a side perspective view partly in section of a single nozzle after depositing the heater titanium nitride layer; 
         FIG. 1061  illustrates the actuator/bend compensator mask; 
         FIG. 1062  illustrates a sectional view showing the effect of depositing the actuator glass and bend compensator titanium nitride after etching; 
         FIG. 1063  illustrates a side perspective view partly in section of a single nozzle after depositing and etching the actuator glass and bend compensator titanium nitride layers; 
         FIG. 1064  illustrates the nozzle mask; 
         FIG. 1065  illustrates a sectional view showing the effect of the depositing of the sacrificial layer and etching the nozzles; 
         FIG. 1066  illustrates a side perspective view partly in section of a single nozzle after depositing and initial etching the sacrificial layer; 
         FIG. 1067  illustrates the nozzle chamber mask; 
         FIG. 1068  illustrates a sectional view showing the etched chambers in the sacrificial layer; 
         FIG. 1069  illustrates a side perspective view partly in section of a single nozzle after further etching of the sacrificial layer; 
         FIG. 1070  illustrates a sectional view showing the deposited layer of the nozzle chamber walls; 
         FIG. 1071  illustrates a side perspective view partly in section of a single nozzle after further deposition of the nozzle chamber walls; 
         FIG. 1072  illustrates a sectional view showing the process of creating self aligned nozzles using Chemical Mechanical Planarization (CMP); 
         FIG. 1073  illustrates a side perspective view partly in section of a single nozzle after CMP of the nozzle chamber walls; 
         FIG. 1074  illustrates a sectional view showing the nozzle mounted on a wafer blank; 
         FIG. 1075  illustrates the back etch inlet mask; 
         FIG. 1076  illustrates a sectional view showing the etching away of the sacrificial layers; 
         FIG. 1077  illustrates a side perspective view partly in section of a single nozzle after etching away of the sacrificial layers; 
         FIG. 1078  illustrates a side perspective view partly in section of a single nozzle after etching away of the sacrificial layers taken along a different section line; 
         FIG. 1079  illustrates a sectional view showing a nozzle filled with ink; 
         FIG. 1080  illustrates a side perspective view partly in section of a single nozzle ejecting ink; 
         FIG. 1081  illustrates a schematic of the control logic for a single nozzle; 
         FIG. 1082  illustrates a CMOS implementation of the control logic of a single nozzle; 
         FIG. 1083  illustrates a legend or key of the various layers utilized in the described CMOS/MEMS implementation; 
         FIG. 1084  illustrates the CMOS levels up to the poly level; 
         FIG. 1085  illustrates the CMOS levels up to the metal  1  level; 
         FIG. 1086  illustrates the CMOS levels up to the metal  2  level; 
         FIG. 1087  illustrates the CMOS levels up to the metal  3  level; 
         FIG. 1088  illustrates the CMOS and MEMS levels up to the MEMS heater level; 
         FIG. 1089  illustrates the Actuator Shroud Level; 
         FIG. 1090  illustrates a side perspective partly in section of a portion of an ink jet head; 
         FIG. 1091  illustrates an enlarged view of a side perspective partly in section of a portion of an inkjet head; 
         FIG. 1092  illustrates a number of layers formed in the construction of a series of actuators; 
         FIG. 1093  illustrates a portion of the back surface of a wafer showing the through wafer ink supply channels; 
         FIG. 1094  illustrates the arrangement of segments in a print head; 
         FIG. 1095  illustrates schematically a single pod numbered by firing order, 
         FIG. 1096  illustrates schematically a single pod numbered by logical order, 
         FIG. 1097  illustrates schematically a single tripod containing one pod of each color, 
         FIG. 1098  illustrates schematically a single podgroup containing 10 tripods; 
         FIG. 1099  illustrates schematically, the relationship between segments, firegroups and tripods; 
         FIG. 1100  illustrates clocking for AEnable and BEnable during a typical print cycle; 
         FIG. 1101  illustrates an exploded perspective view of the incorporation of a print head into an ink channel molding support structure; 
         FIG. 1102  illustrates a side perspective view partly in section of the ink channel molding support structure; 
         FIG. 1103  illustrates a side perspective view partly in section of a print roll unit, print head and platen; and 
         FIG. 1104  illustrates a side perspective view of a print roll unit, print head and platen; 
         FIG. 1105  illustrates a side exploded perspective view of a print roll unit, print head and platen; 
         FIG. 1106  is an enlarged perspective part view illustrating the attachment of a print head to an ink distribution manifold as shown in  FIGS. 1101 and 1102 ; 
         FIG. 1107  illustrates an opened out plan view of the outermost side of the tape automated bonded film shown in  FIG. 1102 ; and 
         FIG. 1108  illustrates the reverse side of the opened out tape automated bonded film shown in  FIG. 1107 . 
     
    
    
     DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS 
     The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems For ease of manufacture using standard process equipment, the print head is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For a general introduction to micro-electric mechanical systems (MEMS) reference is made to standard proceedings in this field including the proceedings of the SPIE (International Society for Optical Engineering), volumes 2642 and 2882 which contain the proceedings for recent advances and conferences in this field. 
     For color photographic applications, the print head is 100 mm long, with a width which depends upon the ink jet type. The smallest print head designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The print heads each contain 19,200 nozzles plus data and control circuitry. 
     Tables of Drop-on-Demand Ink Jets 
     Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee. 
     The following tables form the axes of an eleven dimensional table of ink jet types.
     Actuator mechanism (18 types)   Basic operation mode (7 types)   Auxiliary mechanism (8 types)   Actuator amplification or modification method (17 types)   Actuator motion (19 types)   Nozzle refill method (4 types)   Method of restricting back-flow through inlet (10 types)   Nozzle clearing method (9 types)   Nozzle plate construction (9 types)   Drop ejection direction (5 types)   Ink type (7 types)   

     The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ46. 
     Other ink jet configurations can readily be derived from these 46 examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ46 examples can be made into ink jet print heads with characteristics superior to any currently available ink jet technology. 
     Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ46 series are also listed in the examples column. In some cases, a printer may be listed more than once in a table, where it shares characteristics with more than one entry. 
     Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc. 
     The information associated with the aforementioned 11 dimensional matrix are set out in the following tables. 
     
       
         
           
               
            
               
                   
               
               
                 Actuator mechanism (applied only to selected ink drops) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Thermal bubble 
                 An electrothermal 
                 Large force generated 
                 High power 
                 Canon Bubblejet 1979 
               
               
                   
                 heater heats the ink to 
                 Simple construction 
                 Ink carrier limited to 
                 Endo et al GB patent 
               
               
                   
                 above boiling point, 
                 No moving parts 
                 water 
                 2,007,162 
               
               
                   
                 transferring significant 
                 Fast operation 
                 Low efficiency 
                 Xerox heater-in-pit 
               
               
                   
                 heat to the aqueous ink. 
                 Small chip area 
                 High temperatures 
                 1990 Hawkins et al 
               
               
                   
                 A bubble nucleates and 
                 required for actuator 
                 required 
                 U.S. Pat. No. 4,899,181 
               
               
                   
                 quickly forms, 
                   
                 High mechanical stress 
                 Hewlett-Packard TIJ 
               
               
                   
                 expelling the ink. 
                   
                 Unusual materials 
                 1982 Vaught et al U.S. Pat. No. 
               
               
                   
                 The efficiency of the 
                   
                 required 
                 4,490,728 
               
               
                   
                 process is low, with 
                   
                 Large drive transistors 
               
               
                   
                 typically less than 
                   
                 Cavitation causes 
               
               
                   
                 0.05% of the electrical 
                   
                 actuator failure 
               
               
                   
                 energy being 
                   
                 Kogation reduces 
               
               
                   
                 transformed into kinetic 
                   
                 bubble formation 
               
               
                   
                 energy of the drop. 
                   
                 Large print heads are 
               
               
                   
                   
                   
                 difficult to fabricate 
               
               
                 Piezo-electric 
                 A piezoelectric crystal 
                 Low power 
                 Very large area 
                 Kyser et al U.S. Pat. No. 
               
               
                   
                 such as lead lanthanum 
                 consumption 
                 required for actuator 
                 3,946,398 
               
               
                   
                 zirconate (PZT) is 
                 Many ink types can be 
                 Difficult to integrate 
                 Zoltan U.S. Pat. No. 3,683,212 
               
               
                   
                 electrically activated, 
                 used 
                 with electronics 
                 1973 Stemme U.S. Pat. No. 
               
               
                   
                 and either expands, 
                 Fast operation 
                 High voltage drive 
                 3,747,120 
               
               
                   
                 shears, or bends to 
                 High efficiency 
                 transistors required 
                 Epson Stylus 
               
               
                   
                 apply pressure to the 
                   
                 Full pagewidth print 
                 Tektronix 
               
               
                   
                 ink, ejecting drops. 
                   
                 heads impractical due 
                 IJ04 
               
               
                   
                   
                   
                 to actuator size 
               
               
                   
                   
                   
                 Requires electrical 
               
               
                   
                   
                   
                 poling in high field 
               
               
                   
                   
                   
                 strengths during 
               
               
                   
                   
                   
                 manufacture 
               
               
                 Electro-strictive 
                 An electric field is used 
                 Low power 
                 Low maximum strain 
                 Seiko Epson, Usui et 
               
               
                   
                 to activate 
                 consumption 
                 (approx. 0.01%) 
                 all JP 253401/96 
               
               
                   
                 electrostriction in 
                 Many ink types can be 
                 Large area required for 
                 IJ04 
               
               
                   
                 relaxor materials such 
                 used 
                 actuator due to low 
               
               
                   
                 as lead lanthanum 
                 Low thermal expansion 
                 strain 
               
               
                   
                 zirconate titanate 
                 Electric field strength 
                 Response speed is 
               
               
                   
                 (PLZT) or lead 
                 required (approx. 3.5 
                 marginal (~10 
               
               
                   
                 magnesium niobate 
                 V/micrometer) can be 
                 microseconds) 
               
               
                   
                 (PMN). 
                 generated without 
                 High voltage drive 
               
               
                   
                   
                 difficulty 
                 transistors required 
               
               
                   
                   
                 Does not require 
                 Full pagewidth print 
               
               
                   
                   
                 electrical poling 
                 heads impractical due 
               
               
                   
                   
                   
                 to actuator size 
               
               
                 Ferro-electric 
                 An electric field is used 
                 Low power 
                 Difficult to integrate 
                 IJ04 
               
               
                   
                 to induce a phase 
                 consumption 
                 with electronics 
               
               
                   
                 transition between the 
                 Many ink types can be 
                 Unusual materials such 
               
               
                   
                 antiferroelectric (AFE) 
                 used 
                 as PLZSnT are required 
               
               
                   
                 and ferroelectric (FE) 
                 Fast operation (&lt;1 
                 Actuators require a 
               
               
                   
                 phase. Perovskite 
                 microsecond) 
                 large area 
               
               
                   
                 materials such as tin 
                 Relatively high 
               
               
                   
                 modified lead 
                 longitudinal strain 
               
               
                   
                 lanthanum zirconate 
                 High efficiency 
               
               
                   
                 titanate (PLZSnT) 
                 Electric field strength 
               
               
                   
                 exhibit large strains of 
                 of around 3 V/micron 
               
               
                   
                 up to 1% associated 
                 can be readily provided 
               
               
                   
                 with the AFE to FE 
               
               
                   
                 phase transition. 
               
               
                 Electro-static 
                 Conductive plates are 
                 Low power 
                 Difficult to operate 
                 IJ02, IJ04 
               
               
                 plates 
                 separated by a 
                 consumption 
                 electrostatic devices in 
               
               
                   
                 compressible or fluid 
                 Many ink types can be 
                 an aqueous 
               
               
                   
                 dielectric (usually air). 
                 used 
                 environment 
               
               
                   
                 Upon application of a 
                 Fast operation 
                 The electrostatic 
               
               
                   
                 voltage, the plates 
                   
                 actuator will normally 
               
               
                   
                 attract each other and 
                   
                 need to be separated 
               
               
                   
                 displace ink, causing 
                   
                 from the ink 
               
               
                   
                 drop ejection. The 
                   
                 Very large area 
               
               
                   
                 conductive plates may 
                   
                 required to achieve 
               
               
                   
                 be in a comb or 
                   
                 high forces 
               
               
                   
                 honeycomb structure, 
                   
                 High voltage drive 
               
               
                   
                 or stacked to increase 
                   
                 transistors may be 
               
               
                   
                 the surface area and 
                   
                 required 
               
               
                   
                 therefore the force. 
                   
                 Full pagewidth print 
               
               
                   
                   
                   
                 heads are not 
               
               
                   
                   
                   
                 competitive due to 
               
               
                   
                   
                   
                 actuator size 
               
               
                 Electro-static 
                 A strong electric field 
                 Low current 
                 High voltage required 
                 1989 Saito et al, U.S. Pat. No. 
               
               
                 pull on ink 
                 is applied to the ink, 
                 consumption 
                 May be damaged by 
                 4,799,068 
               
               
                   
                 whereupon electrostatic 
                 Low temperature 
                 sparks due to air 
                 1989 Miura et al, U.S. Pat. No. 
               
               
                   
                 attraction accelerates 
                   
                 breakdown 
                 4,810,954 
               
               
                   
                 the ink towards the 
                   
                 Required field strength 
                 Tone-jet 
               
               
                   
                 print medium. 
                   
                 increases as the drop 
               
               
                   
                   
                   
                 size decreases 
               
               
                   
                   
                   
                 High voltage drive 
               
               
                   
                   
                   
                 transistors required 
               
               
                   
                   
                   
                 Electrostatic field 
               
               
                   
                   
                   
                 attracts dust 
               
               
                 Permanent magnet 
                 An electromagnet 
                 Low power 
                 Complex fabrication 
                 IJ07, IJ10 
               
               
                 electro-magnetic 
                 directly attracts a 
                 consumption 
                 Permanent magnetic 
               
               
                   
                 permanent magnet, 
                 Many ink types can be 
                 material such as 
               
               
                   
                 displacing ink and 
                 used 
                 Neodymium Iron 
               
               
                   
                 causing drop ejection. 
                 Fast operation 
                 Boron (NdFeB) 
               
               
                   
                 Rare earth magnets 
                 High efficiency 
                 required. 
               
               
                   
                 with a field strength 
                 Easy extension from 
                 High local currents 
               
               
                   
                 around 1 Tesla can be 
                 single nozzles to 
                 required 
               
               
                   
                 used. Examples are: 
                 pagewidth print heads 
                 Copper metalization 
               
               
                   
                 Samarium Cobalt 
                   
                 should be used for long 
               
               
                   
                 (SaCo) and magnetic 
                   
                 electromigration 
               
               
                   
                 materials in the 
                   
                 lifetime and low 
               
               
                   
                 neodymium iron boron 
                   
                 resistivity 
               
               
                   
                 family (NdFeB, 
                   
                 Pigmented inks are 
               
               
                   
                 NdDyFeBNb, 
                   
                 usually infeasible 
               
               
                   
                 NdDyFeB, etc) 
                   
                 Operating temperature 
               
               
                   
                   
                   
                 limited to the Curie 
               
               
                   
                   
                   
                 temperature (around 
               
               
                   
                   
                   
                 540 K) 
               
               
                 Soft magnetic core 
                 A solenoid induced a 
                 Low power 
                 Complex fabrication 
                 IJ01, IJ05, IJ08, IJ10, 
               
               
                 electro-magnetic 
                 magnetic field in a soft 
                 consumption 
                 Materials not usually 
                 IJ12, IJ14, IJ15, IJ17 
               
               
                   
                 magnetic core or yoke 
                 Many ink types can be 
                 present in a CMOS fab 
               
               
                   
                 fabricated from a 
                 used 
                 such as NiFe, CoNiFe, 
               
               
                   
                 ferrous material such as 
                 Fast operation 
                 or CoFe are required 
               
               
                   
                 electroplated iron 
                 High efficiency 
                 High local currents 
               
               
                   
                 alloys such as CoNiFe 
                 Easy extension from 
                 required 
               
               
                   
                 [1], CoFe, or NiFe 
                 single nozzles to 
                 Copper metalization 
               
               
                   
                 alloys. Typically, the 
                 pagewidth print heads 
                 should be used for long 
               
               
                   
                 soft magnetic material 
                   
                 electromigration 
               
               
                   
                 is in two parts, which 
                   
                 lifetime and low 
               
               
                   
                 are normally held apart 
                   
                 resistivity 
               
               
                   
                 by a spring. When the 
                   
                 Electroplating is 
               
               
                   
                 solenoid is actuated, the 
                   
                 required 
               
               
                   
                 two parts attract, 
                   
                 High saturation flux 
               
               
                   
                 displacing the ink. 
                   
                 density is required (2.0- 
               
               
                   
                   
                   
                 2.1 T is achievable with 
               
               
                   
                   
                   
                 CoNiFe [1]) 
               
               
                 Lorenz force 
                 The Lorenz force 
                 Low power 
                 Force acts as a twisting 
                 IJ06, IJ11, IJ13, IJ16 
               
               
                   
                 acting on a current 
                 consumption 
                 motion 
               
               
                   
                 carrying wire in a 
                 Many ink types can be 
                 Typically, only a 
               
               
                   
                 magnetic field is 
                 used 
                 quarter of the solenoid 
               
               
                   
                 utilized. 
                 Fast operation 
                 length provides force in 
               
               
                   
                 This allows the 
                 High efficiency 
                 a useful direction 
               
               
                   
                 magnetic field to be 
                 Easy extension from 
                 High local currents 
               
               
                   
                 supplied externally to 
                 single nozzles to 
                 required 
               
               
                   
                 the print head, for 
                 pagewidth print heads 
                 Copper metalization 
               
               
                   
                 example with rare earth 
                   
                 should be used for long 
               
               
                   
                 permanent magnets. 
                   
                 electromigration 
               
               
                   
                 Only the current 
                   
                 lifetime and low 
               
               
                   
                 carrying wire need be 
                   
                 resistivity 
               
               
                   
                 fabricated on the print- 
                   
                 Pigmented inks are 
               
               
                   
                 head, simplifying 
                   
                 usually infeasible 
               
               
                   
                 materials requirements. 
               
               
                 Magneto-striction 
                 The actuator uses the 
                 Many ink types can be 
                 Force acts as a twisting 
                 Fischenbeck, U.S. Pat. No. 
               
               
                   
                 giant magnetostrictive 
                 used 
                 motion 
                 4,032,929 
               
               
                   
                 effect of materials such 
                 Fast operation 
                 Unusual materials such 
                 IJ25 
               
               
                   
                 as Terfenol-D (an alloy 
                 Easy extension from 
                 as Terfenol-D are 
               
               
                   
                 of terbium, dysprosium 
                 single nozzles to 
                 required 
               
               
                   
                 and iron developed at 
                 pagewidth print heads 
                 High local currents 
               
               
                   
                 the Naval Ordnance 
                 High force is available 
                 required 
               
               
                   
                 Laboratory, hence Ter- 
                   
                 Copper metalization 
               
               
                   
                 Fe-NOL). For best 
                   
                 should be used for long 
               
               
                   
                 efficiency, the actuator 
                   
                 electronugration 
               
               
                   
                 should be pre-stressed 
                   
                 lifetime and low 
               
               
                   
                 to approx. 8 MPa. 
                   
                 resistivity 
               
               
                   
                   
                   
                 Pre-stressing may be 
               
               
                   
                   
                   
                 required 
               
               
                 Surface tension 
                 Ink under positive 
                 Low power 
                 Requires 
                 Silverbrook, EP 0771 
               
               
                 reduction 
                 pressure is held in a 
                 consumption 
                 supplementary force to 
                 658 A2 and related 
               
               
                   
                 nozzle by surface 
                 Simple construction 
                 effect drop separation 
                 patent applications 
               
               
                   
                 tension. The surface 
                 No unusual materials 
                 Requires special ink 
               
               
                   
                 tension of the ink is 
                 required in fabrication 
                 surfactants 
               
               
                   
                 reduced below the 
                 High efficiency 
                 Speed may be limited 
               
               
                   
                 bubble threshold, 
                 Easy extension from 
                 by surfactant properties 
               
               
                   
                 causing the ink to 
                 single nozzles to 
               
               
                   
                 egress from the nozzle. 
                 pagewidth print heads 
               
               
                 Viscosity reduction 
                 The ink viscosity is 
                 Simple construction 
                 Requires 
                 Silverbrook, EP 0771 
               
               
                   
                 locally reduced to 
                 No unusual materials 
                 supplementary force to 
                 658 A2 and related 
               
               
                   
                 select which drops are 
                 required in fabrication 
                 effect drop separation 
                 patent applications 
               
               
                   
                 to be ejected. A 
                 Easy extension from 
                 Requires special ink 
               
               
                   
                 viscosity reduction can 
                 single nozzles to 
                 viscosity properties 
               
               
                   
                 be achieved 
                 pagewidth print heads 
                 High speed is difficult 
               
               
                   
                 electrothermally with 
                   
                 to achieve 
               
               
                   
                 most inks, but special 
                   
                 Requires oscillating ink 
               
               
                   
                 inks can be engineered 
                   
                 pressure 
               
               
                   
                 for a 100:1 viscosity 
                   
                 A high temperature 
               
               
                   
                 reduction. 
                   
                 difference (typically 80 
               
               
                   
                   
                   
                 degrees) is required 
               
               
                 Acoustic 
                 An acoustic wave is 
                 Can operate without a 
                 Complex drive circuitry 
                 1993 Hadimioglu et al, 
               
               
                   
                 generated and focussed 
                 nozzle plate 
                 Complex fabrication 
                 EUP 550,192 
               
               
                   
                 upon the drop ejection 
                   
                 Low efficiency 
                 1993 Elrod et al, EUP 
               
               
                   
                 region. 
                   
                 Poor control of drop 
                 572,220 
               
               
                   
                   
                   
                 position 
               
               
                   
                   
                   
                 Poor control of drop 
               
               
                   
                   
                   
                 volume 
               
               
                 Thermo-elastic 
                 An actuator which 
                 Low power 
                 Efficient aqueous 
                 IJ03, IJ09, IJ17, IJ18, 
               
               
                 bend actuator 
                 relies upon differential 
                 consumption 
                 operation requires a 
                 IJ19, IJ20, IJ21, IJ22, 
               
               
                   
                 thermal expansion 
                 Many ink types can be 
                 thermal insulator on the 
                 IJ23, IJ24, IJ27, IJ28, 
               
               
                   
                 upon Joule heating is 
                 used 
                 hot side 
                 IJ29, IJ30, IJ31, IJ32, 
               
               
                   
                 used. 
                 Simple planar 
                 Corrosion prevention 
                 IJ33, IJ34, IJ35, IJ36, 
               
               
                   
                   
                 fabrication 
                 can be difficult 
                 IJ37, IJ38 ,IJ39, IJ40, 
               
               
                   
                   
                 Small chip area 
                 Pigmented inks may be 
                 IJ41 
               
               
                   
                   
                 required for each 
                 infeasible, as pigment 
               
               
                   
                   
                 actuator 
                 particles may jam the 
               
               
                   
                   
                 Fast operation 
                 bend actuator 
               
               
                   
                   
                 High efficiency 
               
               
                   
                   
                 CMOS compatible 
               
               
                   
                   
                 voltages and currents 
               
               
                   
                   
                 Standard MEMS 
               
               
                   
                   
                 processes can be used 
               
               
                   
                   
                 Easy extension from 
               
               
                   
                   
                 single nozzles to 
               
               
                   
                   
                 pagewidth print heads 
               
               
                 High CTE 
                 A material with a very 
                 High force can be 
                 Requires special 
                 IJ09, IJ17, IJ18, IJ20, 
               
               
                 thermo- 
                 high coefficient of 
                 generated 
                 material (e.g. PTFE) 
                 IJ21, IJ22, IJ23, IJ24, 
               
               
                 elastic 
                 thermal expansion 
                 Three methods of 
                 Requires a PTFE 
                 IJ27, IJ28, IJ29, IJ30, 
               
               
                 actuator 
                 (CTE) such as 
                 PTFE deposition are 
                 deposition process, 
                 IJ31, IJ42, IJ43, IJ44 
               
               
                   
                 polytetrafluoroethylene 
                 under development: 
                 which is not yet 
               
               
                   
                 (PTFE) is used. As 
                 chemical vapor 
                 standard in ULSI fabs 
               
               
                   
                 high CTE materials are 
                 deposition (CVD), spin 
                 PTFE deposition 
               
               
                   
                 usually non-conductive, 
                 coating, and 
                 cannot be followed 
               
               
                   
                 a heater fabricated from 
                 evaporation 
                 with high temperature 
               
               
                   
                 a conductive material is 
                 PTFE is a candidate for 
                 (above 350° C.) 
               
               
                   
                 incorporated. A 50 
                 low dielectric constant 
                 processing 
               
               
                   
                 micron long PTFE 
                 insulation in ULSI 
                 Pigmented inks may be 
               
               
                   
                 bend actuator with 
                 Very low power 
                 infeasible, as pigment 
               
               
                   
                 polysilicon heater and 
                 consumption 
                 particles may jam the 
               
               
                   
                 15 mW power input 
                 Many ink types can be 
                 bend actuator 
               
               
                   
                 can provide 180 
                 used 
               
               
                   
                 microNewton force and 
                 Simple planar 
               
               
                   
                 10 micron deflection, 
                 fabrication 
               
               
                   
                 Actuator motions 
                 Small chip area 
               
               
                   
                 include: 
                 required for each 
               
               
                   
                 Bend 
                 actuator 
               
               
                   
                 Push 
                 Fast operation 
               
               
                   
                 Buckle 
                 High efficiency 
               
               
                   
                 Rotate 
                 CMOS compatible 
               
               
                   
                   
                 voltages and currents 
               
               
                   
                   
                 Easy extension from 
               
               
                   
                   
                 single nozzles to 
               
               
                   
                   
                 pagewidth print heads 
               
               
                 Conductive 
                 A polymer with a high 
                 High force can be 
                 Requires special 
                 IJ24 
               
               
                 polymer 
                 coefficient of thermal 
                 generated 
                 materials development 
               
               
                 thermo- 
                 expansion (such as 
                 Very low power 
                 (High CTE conductive 
               
               
                 elastic 
                 PTFE) is doped with 
                 consumption 
                 polymer) 
               
               
                 actuator 
                 conducting substances 
                 Many ink types can be 
                 Requires a PTFE 
               
               
                   
                 to increase its 
                 used 
                 deposition process, 
               
               
                   
                 conductivity to about 3 
                 Simple planar 
                 which is not yet 
               
               
                   
                 orders of magnitude 
                 fabrication 
                 standard in ULSI fabs 
               
               
                   
                 below that of copper. 
                 Small chip area 
                 PTFE deposition 
               
               
                   
                 The conducting 
                 required for each 
                 cannot be followed 
               
               
                   
                 polymer expands when 
                 actuator 
                 with high temperature 
               
               
                   
                 resistively heated. 
                 Fast operation 
                 (above 350° C.) 
               
               
                   
                 Examples of 
                 High efficiency 
                 processing 
               
               
                   
                 conducting dopants 
                 CMOS compatible 
                 Evaporation and CVD 
               
               
                   
                 include: 
                 voltages and currents 
                 deposition techniques 
               
               
                   
                 Carbon nanotubes 
                 Easy extension from 
                 cannot be used 
               
               
                   
                 Metal fibers 
                 single nozzles to 
                 Pigmented inks may be 
               
               
                   
                 Conductive polymers 
                 pagewidth print heads 
                 infeasible, as pigment 
               
               
                   
                 such as doped 
                   
                 particles may jam the 
               
               
                   
                 polythiophene 
                   
                 bend actuator 
               
               
                   
                 Carbon granules 
               
               
                 Shape memory 
                 A shape memory alloy 
                 High force is available 
                 Fatigue limits 
                 IJ26 
               
               
                 alloy 
                 such as TiNi (also 
                 (stresses of hundreds of 
                 maximum number of 
               
               
                   
                 known as Nitinol - 
                 MPa) 
                 cycles 
               
               
                   
                 Nickel Titanium alloy 
                 Large strain is available 
                 Low strain (1%) is 
               
               
                   
                 developed at the Naval 
                 (more than 3%) 
                 required to extend 
               
               
                   
                 Ordnance Laboratory) 
                 High corrosion 
                 fatigue resistance 
               
               
                   
                 is thermally switched 
                 resistance 
                 Cycle rate limited by 
               
               
                   
                 between its weak 
                 Simple construction 
                 heat removal 
               
               
                   
                 martensitic state and its 
                 Easy extension from 
                 Requires unusual 
               
               
                   
                 high stiffness austenic 
                 single nozzles to 
                 materials (TiNi) 
               
               
                   
                 state. The shape of the 
                 pagewidth print heads 
                 The latent heat of 
               
               
                   
                 actuator in its 
                 Low voltage operation 
                 transformation must be 
               
               
                   
                 martensitic state is 
                   
                 provided 
               
               
                   
                 deformed relative to the 
                   
                 High current operation 
               
               
                   
                 austenic shape. The 
                   
                 Requires pre-stressing 
               
               
                   
                 shape change causes 
                   
                 to distort the 
               
               
                   
                 ejection of a drop. 
                   
                 martensitic state 
               
               
                 Linear Magnetic 
                 Linear magnetic 
                 Linear Magnetic 
                 Requires unusual 
                 IJ12 
               
               
                 Actuator 
                 actuators include the 
                 actuators can be 
                 semiconductor 
               
               
                   
                 Linear Induction 
                 constructed with high 
                 materials such as soft 
               
               
                   
                 Actuator (LIA), Linear 
                 thrust, long travel, and 
                 magnetic alloys (e.g. 
               
               
                   
                 Permanent Magnet 
                 high efficiency using 
                 CoNiFe) 
               
               
                   
                 Synchronous Actuator 
                 planar semiconductor 
                 Some varieties also 
               
               
                   
                 (LPMSA), Linear 
                 fabrication techniques 
                 require permanent 
               
               
                   
                 Reluctance 
                 Long actuator travel is 
                 magnetic materials 
               
               
                   
                 Synchronous Actuator 
                 available 
                 such as Neodymium 
               
               
                   
                 (LRSA), Linear 
                 Medium force is 
                 iron boron (NdFeB) 
               
               
                   
                 Switched Reluctance 
                 available 
                 Requires complex 
               
               
                   
                 Actuator (LSRA), and 
                 Low voltage operation 
                 multi-phase drive 
               
               
                   
                 the Linear Stepper 
                   
                 circuitry 
               
               
                   
                 Actuator (LSA). 
                   
                 High current operation 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 Basic operation mode 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Actuator 
                 This is the simplest 
                 Simple operation 
                 Drop repetition rate is 
                 Thermal ink jet 
               
               
                 directly 
                 mode of operation: the 
                 No external fields 
                 usually limited to 
                 Piezoelectric ink jet 
               
               
                 pushes ink 
                 actuator directly 
                 required 
                 around 10 kHz. 
                 IJ01, IJ02, IJ03, IJ04, 
               
               
                   
                 supplies sufficient 
                 Satellite drops can be 
                 However, this is not 
                 IJ05, IJ06, IJ07, IJ09, 
               
               
                   
                 kinetic energy to expel 
                 avoided if drop velocity 
                 fundamental to the 
                 IJ11, IJ12, IJ14, IJ16, 
               
               
                   
                 the drop. The drop 
                 is less than 4 m/s 
                 method, but is related 
                 IJ20, IJ22, IJ23, IJ24, 
               
               
                   
                 must have a sufficient 
                 Can be efficient, 
                 to the refill method 
                 IJ25, IJ26, IJ27, IJ28, 
               
               
                   
                 velocity to overcome 
                 depending upon the 
                 normally used 
                 IJ29, IJ30, IJ31, IJ32, 
               
               
                   
                 the surface tension. 
                 actuator used 
                 All of the drop kinetic 
                 IJ33, IJ34, IJ35, IJ36, 
               
               
                   
                   
                   
                 energy must be 
                 IJ37, IJ38, IJ39, IJ40, 
               
               
                   
                   
                   
                 provided by the 
                 IJ41, IJ42, IJ43, IJ44 
               
               
                   
                   
                   
                 actuator 
               
               
                   
                   
                   
                 Satellite drops usually 
               
               
                   
                   
                   
                 form if drop velocity is 
               
               
                   
                   
                   
                 greater than 4.5 m/s 
               
               
                 Proximity 
                 The drops to be printed 
                 Very simple print head 
                 Requires close 
                 Silverbrook, EP 0771 
               
               
                   
                 are selected by some 
                 fabrication can be used 
                 proximity between the 
                 658 A2 and related 
               
               
                   
                 manner (e.g. thermally 
                 The drop selection 
                 print head and the print 
                 patent applications 
               
               
                   
                 induced surface tension 
                 means does not need to 
                 media or transfer roller 
               
               
                   
                 reduction of 
                 provide the energy 
                 May require two print 
               
               
                   
                 pressurized ink). 
                 required to separate the 
                 heads printing alternate 
               
               
                   
                 Selected drops are 
                 drop from the nozzle 
                 rows of the image 
               
               
                   
                 separated from the ink 
                   
                 Monolithic color print 
               
               
                   
                 in the nozzle by contact 
                   
                 heads are difficult 
               
               
                   
                 with the print medium 
               
               
                   
                 or a transfer roller. 
               
               
                 Electro-static 
                 The drops to be printed 
                 Very simple print head 
                 Requires very high 
                 Silverbrook, EP 0771 
               
               
                 pull on ink 
                 are selected by some 
                 fabrication can be used 
                 electrostatic field 
                 658 A2 and related 
               
               
                   
                 manner (e.g. thermally 
                 The drop selection 
                 Electrostatic field for 
                 patent applications 
               
               
                   
                 induced surface tension 
                 means does not need to 
                 small nozzle sizes is 
                 Tone-Jet 
               
               
                   
                 reduction of 
                 provide the energy 
                 above air breakdown 
               
               
                   
                 pressurized ink). 
                 required to separate the 
                 Electrostatic field may 
               
               
                   
                 Selected drops are 
                 drop from the nozzle 
                 attract dust 
               
               
                   
                 separated from the ink 
               
               
                   
                 in the nozzle by a 
               
               
                   
                 strong electric field. 
               
               
                 Magnetic 
                 The drops to be printed 
                 Very simple print head 
                 Requires magnetic ink 
                 Silverbrook, EP 0771 
               
               
                 pull on ink 
                 are selected by some 
                 fabrication can be used 
                 Ink colors other than 
                 658 A2 and related 
               
               
                   
                 manner (e.g. thermally 
                 The drop selection 
                 black are difficult 
                 patent applications 
               
               
                   
                 induced surface tension 
                 means does not need to 
                 Requires very high 
               
               
                   
                 reduction of 
                 provide the energy 
                 magnetic fields 
               
               
                   
                 pressurized ink). 
                 required to separate the 
               
               
                   
                 Selected drops are 
                 drop from the nozzle 
               
               
                   
                 separated from the ink 
               
               
                   
                 in the nozzle by a 
               
               
                   
                 strong magnetic field 
               
               
                   
                 acting on the magnetic 
               
               
                   
                 ink. 
               
               
                 Shutter 
                 The actuator moves a 
                 High speed (&gt;50 kHz) 
                 Moving parts are 
                 IJ13, IJ17, IJ21 
               
               
                   
                 shutter to block ink 
                 operation can be 
                 required 
               
               
                   
                 flow to the nozzle. The 
                 achieved due to 
                 Requires ink pressure 
               
               
                   
                 ink pressure is pulsed at 
                 reduced refill time 
                 modulator 
               
               
                   
                 a multiple of the drop 
                 Drop timing can be 
                 Friction and wear must 
               
               
                   
                 ejection frequency. 
                 very accurate 
                 be considered 
               
               
                   
                   
                 The actuator energy 
                 Stiction is possible 
               
               
                   
                   
                 can be very low 
               
               
                 Shuttered 
                 The actuator moves a 
                 Actuators with small 
                 Moving parts are 
                 IJ08, IJ15, IJ18, IJ19 
               
               
                 grill 
                 shutter to block ink 
                 travel can be used 
                 required 
               
               
                   
                 flow through a grill to 
                 Actuators with small 
                 Requires ink pressure 
               
               
                   
                 the nozzle. The shutter 
                 force can be used 
                 modulator 
               
               
                   
                 movement need only be 
                 High speed (&gt;50 kHz) 
                 Friction and wear must 
               
               
                   
                 equal to the width of 
                 operation can be 
                 be considered 
               
               
                   
                 the grill holes. 
                 achieved 
                 Stiction is possible 
               
               
                 Pulsed 
                 A pulsed magnetic field 
                 Extremely low energy 
                 Requires an external 
                 IJ10 
               
               
                 magnetic pull 
                 attracts an ‘ink pusher’ 
                 operation is possible 
                 pulsed magnetic field 
               
               
                 on ink pusher 
                 at the drop ejection 
                 No heat dissipation 
                 Requires special 
               
               
                   
                 frequency. An actuator 
                 problems 
                 materials for both the 
               
               
                   
                 controls a catch, which 
                   
                 actuator and the ink 
               
               
                   
                 prevents the ink pusher 
                   
                 pusher 
               
               
                   
                 from moving when a 
                   
                 Complex construction 
               
               
                   
                 drop is not to be 
               
               
                   
                 ejected. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 Auxiliary mechanism (applied to all nozzles) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 None 
                 The actuator directly 
                 Simplicity of 
                 Drop ejection energy 
                 Most ink jets, including 
               
               
                   
                 fires the ink drop, and 
                 construction 
                 must be supplied by 
                 piezoelectric and 
               
               
                   
                 there is no external 
                 Simplicity of operation 
                 individual nozzle 
                 thermal bubble. 
               
               
                   
                 field or other 
                 Small physical size 
                 actuator 
                 IJ01, IJ02, IJ03, IJ04, 
               
               
                   
                 mechanism required. 
                   
                   
                 IJ05, IJ07, IJ09, IJ11, 
               
               
                   
                   
                   
                   
                 IJ12, IJ14, IJ20, IJ22, 
               
               
                   
                   
                   
                   
                 IJ23, IJ24, IJ25, IJ26, 
               
               
                   
                   
                   
                   
                 IJ27, IJ28, IJ29, IJ30, 
               
               
                   
                   
                   
                   
                 IJ31, IJ32, IJ33, IJ34, 
               
               
                   
                   
                   
                   
                 IJ35, IJ36, IJ37, IJ38, 
               
               
                   
                   
                   
                   
                 IJ39, IJ40, IJ41, IJ42, 
               
               
                   
                   
                   
                   
                 IJ43, IJ44 
               
               
                 Oscillating 
                 The ink pressure 
                 Oscillating ink pressure 
                 Requires external ink 
                 Silverbrook, EP 0771 
               
               
                 ink pressure 
                 oscillates, providing 
                 can provide a refill 
                 pressure oscillator 
                 658 A2 and related 
               
               
                 (including 
                 much of the drop 
                 pulse, allowing higher 
                 Ink pressure phase and 
                 patent applications 
               
               
                 acoustic 
                 ejection energy. The 
                 operating speed 
                 amplitude must be 
                 IJ08, IJ13, IJ15, IJ17, 
               
               
                 stimul-ation) 
                 actuator selects which 
                 The actuators may 
                 carefully controlled 
                 IJ18, IJ19, IJ21 
               
               
                   
                 drops are to be fired by 
                 operate with much 
                 Acoustic reflections in 
               
               
                   
                 selectively blocking or 
                 lower energy 
                 the ink chamber must 
               
               
                   
                 enabling nozzles. The 
                 Acoustic lenses can be 
                 be designed for 
               
               
                   
                 ink pressure oscillation 
                 used to focus the sound 
               
               
                   
                 may be achieved by 
                 on the nozzles 
               
               
                   
                 vibrating the print head, 
               
               
                   
                 or preferably by an 
               
               
                   
                 actuator in the ink 
               
               
                   
                 supply. 
               
               
                 Media 
                 The print head is placed 
                 Low power 
                 Precision assembly 
                 Silverbrook, EP 0771 
               
               
                 proximity 
                 in close proximity to 
                 High accuracy 
                 required 
                 658 A2 and related 
               
               
                   
                 the print medium. 
                 Simple print head 
                 Paper fibers may cause 
                 patent applications 
               
               
                   
                 Selected drops protrude 
                 construction 
                 problems 
               
               
                   
                 from the print head 
                   
                 Cannot print on rough 
               
               
                   
                 further than unselected 
                   
                 substrates 
               
               
                   
                 drops, and contact the 
               
               
                   
                 print medium. The drop 
               
               
                   
                 soaks into the medium 
               
               
                   
                 fast enough to cause 
               
               
                   
                 drop separation. 
               
               
                 Transfer 
                 Drops are printed to a 
                 High accuracy 
                 Bulky 
                 Silverbrook, EP 0771 
               
               
                 roller 
                 transfer roller instead of 
                 Wide range of print 
                 Expensive 
                 658 A2 and related 
               
               
                   
                 straight to the print 
                 substrates can be used 
                 Complex construction 
                 patent applications 
               
               
                   
                 medium. A transfer 
                 Ink can be dried on the 
                   
                 Tektronix hot melt 
               
               
                   
                 roller can also be used 
                 transfer roller 
                   
                 piezoelectric ink jet 
               
               
                   
                 for proximity drop 
                   
                   
                 Any of the IJ series 
               
               
                   
                 separation. 
               
               
                 Electro-static 
                 An electric field is used 
                 Low power 
                 Field strength required 
                 Silverbrook, EP 0771 
               
               
                   
                 to accelerate selected 
                 Simple print head 
                 for separation of small 
                 658 A2 and related 
               
               
                   
                 drops towards the print 
                 construction 
                 drops is near or above 
                 patent applications 
               
               
                   
                 medium. 
                   
                 air breakdown 
                 Tone-Jet 
               
               
                 Direct 
                 A magnetic field is 
                 Low power 
                 Requires magnetic ink 
                 Silverbrook, EP 0771 
               
               
                 magnetic 
                 used to accelerate 
                 Simple print head 
                 Requires strong 
                 658 A2 and related 
               
               
                 field 
                 selected drops of 
                 construction 
                 magnetic field 
                 patent applications 
               
               
                   
                 magnetic ink towards 
               
               
                   
                 the print medium. 
               
               
                 Cross 
                 The print head is placed 
                 Does not require 
                 Requires external 
                 IJ06, IJ16 
               
               
                 magnetic 
                 in a constant magnetic 
                 magnetic materials to 
                 magnet 
               
               
                 field 
                 field. The Lorenz force 
                 be integrated in the 
                 Current densities may 
               
               
                   
                 in a current carrying 
                 print head 
                 be high, resulting in 
               
               
                   
                 wire is used to move 
                 manufacturing process 
                 electromigration 
               
               
                   
                 the actuator. 
                   
                 problems 
               
               
                 Pulsed 
                 A pulsed magnetic field 
                 Very low power 
                 Complex print head 
                 IJ10 
               
               
                 magnetic 
                 is used to cyclically 
                 operation is possible 
                 construction 
               
               
                 field 
                 attract a paddle, which 
                 Small print head size 
                 Magnetic materials 
               
               
                   
                 pushes on the ink. A 
                   
                 required in print head 
               
               
                   
                 small actuator moves a 
               
               
                   
                 catch, which selectively 
               
               
                   
                 prevents the paddle 
               
               
                   
                 from moving. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 Actuator amplification or modification method 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 None 
                 No actuator mechanical 
                 Operational simplicity 
                 Many actuator 
                 Thermal Bubble Ink jet 
               
               
                   
                 amplification is used. 
                   
                 mechanisms have 
                 IJ01, IJ02, IJ06, IJ07, 
               
               
                   
                 The actuator directly 
                   
                 insufficient travel, or 
                 IJ16, IJ25, IJ26 
               
               
                   
                 drives the drop ejection 
                   
                 insufficient force, to 
               
               
                   
                 process. 
                   
                 efficiently drive the 
               
               
                   
                   
                   
                 drop ejection process 
               
               
                 Differential 
                 An actuator material 
                 Provides greater travel 
                 High stresses are 
                 Piezoelectric 
               
               
                 expansion 
                 expands more on one 
                 in a reduced print head 
                 involved 
                 IJ03, IJ09, IJ17, IJ18, 
               
               
                 bend actuator 
                 side than on the other. 
                 area 
                 Care must be taken that 
                 IJ19, IJ20, IJ21, IJ22, 
               
               
                   
                 The expansion may be 
                   
                 the materials do not 
                 IJ23, IJ24, IJ27, IJ29, 
               
               
                   
                 thermal, piezoelectric, 
                   
                 delaminate 
                 IJ30, IJ31, IJ32, IJ33, 
               
               
                   
                 magnetostrictive, or 
                   
                 Residual bend resulting 
                 IJ34, IJ35, IJ36, IJ37, 
               
               
                   
                 other mechanism. The 
                   
                 from high temperature 
                 IJ38, IJ39, IJ42, IJ43, 
               
               
                   
                 bend actuator converts 
                   
                 or high stress during 
                 IJ44 
               
               
                   
                 a high force low travel 
                   
                 formation 
               
               
                   
                 actuator mechanism to 
               
               
                   
                 high travel, lower force 
               
               
                   
                 mechanism. 
               
               
                 Transient 
                 A trilayer bend actuator 
                 Very good temperature 
                 High stresses are 
                 IJ40, IJ41 
               
               
                 bend actuator 
                 where the two outside 
                 stability 
                 involved 
               
               
                   
                 layers are identical. 
                 High speed, as a new 
                 Care must be taken that 
               
               
                   
                 This cancels bend due 
                 drop can be fired before 
                 the materials do not 
               
               
                   
                 to ambient temperature 
                 heat dissipates 
                 delaminate 
               
               
                   
                 and residual stress. The 
                 Cancels residual stress 
               
               
                   
                 actuator only responds 
                 of formation 
               
               
                   
                 to transient heating of 
               
               
                   
                 one side or the other. 
               
               
                 Reverse 
                 The actuator loads a 
                 Better coupling to the 
                 Fabrication complexity 
                 IJ05, IJ11 
               
               
                 spring 
                 spring. When the 
                 ink 
                 High stress in the 
               
               
                   
                 actuator is turned off, 
                   
                 spring 
               
               
                   
                 the spring releases. 
               
               
                   
                 This can reverse the 
               
               
                   
                 force/distance curve of 
               
               
                   
                 the actuator to make it 
               
               
                   
                 compatible with the 
               
               
                   
                 force/time requirements 
               
               
                   
                 of the drop ejection. 
               
               
                 Actuator 
                 A series of thin 
                 Increased travel 
                 Increased fabrication 
                 Some piezoelectric ink 
               
               
                 stack 
                 actuators are stacked. 
                 Reduced drive voltage 
                 complexity 
                 jets 
               
               
                   
                 This can be appropriate 
                   
                 Increased possibility of 
                 IJ04 
               
               
                   
                 where actuators require 
                   
                 short circuits due to 
               
               
                   
                 high electric field 
                   
                 pinholes 
               
               
                   
                 strength, such as 
               
               
                   
                 electrostatic and 
               
               
                   
                 piezoelectric actuators. 
               
               
                 Multiple 
                 Multiple smaller 
                 Increases the force 
                 Actuator forces may 
                 IJ12, IJ13, IJ18, IJ20, 
               
               
                 actuators 
                 actuators are used 
                 available from an 
                 not add linearly, 
                 IJ22, IJ28, IJ42, IJ43 
               
               
                   
                 simultaneously to move 
                 actuator 
                 reducing efficiency 
               
               
                   
                 the ink. Each actuator 
                 Multiple actuators can 
               
               
                   
                 need provide only a 
                 be positioned to control 
               
               
                   
                 portion of the force 
                 ink flow accurately 
               
               
                   
                 required. 
               
               
                 Linear 
                 A linear spring is used 
                 Matches low travel 
                 Requires print head 
                 IJ15 
               
               
                 Spring 
                 to transform a motion 
                 actuator with higher 
                 area for the spring 
               
               
                   
                 with small travel and 
                 travel requirements 
               
               
                   
                 high force into a longer 
                 Non-contact method of 
               
               
                   
                 travel, lower force 
                 motion transformation 
               
               
                   
                 motion. 
               
               
                 Coiled 
                 A bend actuator is 
                 Increases travel 
                 Generally restricted to 
                 IJ17, IJ21, IJ34, IJ35 
               
               
                 actuator 
                 coiled to provide 
                 Reduces chip area 
                 planar implementations 
               
               
                   
                 greater travel in a 
                 Planar implementations 
                 due to extreme 
               
               
                   
                 reduced chip area. 
                 are relatively easy to 
                 fabrication difficulty in 
               
               
                   
                   
                 fabricate. 
                 other orientations. 
               
               
                 Flexure bend 
                 A bend actuator has a 
                 Simple means of 
                 Care must be taken not 
                 IJ10, IJ19, IJ33 
               
               
                 actuator 
                 small region near the 
                 increasing travel of a 
                 to exceed the elastic 
               
               
                   
                 fixture point, which 
                 bend actuator 
                 limit in the flexure area 
               
               
                   
                 flexes much more 
                   
                 Stress distribution is 
               
               
                   
                 readily than the 
                   
                 very uneven 
               
               
                   
                 remainder of the 
                   
                 Difficult to accurately 
               
               
                   
                 actuator. The actuator 
                   
                 model with finite 
               
               
                   
                 flexing is effectively 
                   
                 element analysis 
               
               
                   
                 converted from an even 
               
               
                   
                 coiling to an angular 
               
               
                   
                 bend, resulting in 
               
               
                   
                 greater travel of the 
               
               
                   
                 actuator tip. 
               
               
                 Catch 
                 The actuator controls a 
                 Very low actuator 
                 Complex construction 
                 IJ10 
               
               
                   
                 small catch. The catch 
                 energy 
                 Requires external force 
               
               
                   
                 either enables or 
                 Very small actuator 
                 Unsuitable for 
               
               
                   
                 disables movement of 
                 size 
                 pigmented inks 
               
               
                   
                 an ink pusher that is 
               
               
                   
                 controlled in a bulk 
               
               
                   
                 manner. 
               
               
                 Gears 
                 Gears can be used to 
                 Low force, low travel 
                 Moving parts are 
                 IJ13 
               
               
                   
                 increase travel at the 
                 actuators can be used 
                 required 
               
               
                   
                 expense of duration. 
                 Can be fabricated using 
                 Several actuator cycles 
               
               
                   
                 Circular gears, rack and 
                 standard surface 
                 are required 
               
               
                   
                 pinion, ratchets, and 
                 MEMS processes 
                 More complex drive 
               
               
                   
                 other gearing methods 
                   
                 electronics 
               
               
                   
                 can be used. 
                   
                 Complex construction 
               
               
                   
                   
                   
                 Friction, friction, and 
               
               
                   
                   
                   
                 wear are possible 
               
               
                 Buckle plate 
                 A buckle plate can be 
                 Very fast movement 
                 Must stay within elastic 
                 S. Hirata et al, “An Ink- 
               
               
                   
                 used to change a slow 
                 achievable 
                 limits of the materials 
                 jet Head Using 
               
               
                   
                 actuator into a fast 
                   
                 for long device life 
                 Diaphragm 
               
               
                   
                 motion. It can also 
                   
                 High stresses involved 
                 Microactuator”, Proc. 
               
               
                   
                 convert a high force, 
                   
                 Generally high power 
                 IEEE MEMS, February 
               
               
                   
                 low travel actuator into 
                   
                 requirement 
                 1996, pp 418-423. 
               
               
                   
                 a high travel, medium 
                   
                   
                 IJ18, IJ27 
               
               
                   
                 force motion. 
               
               
                 Tapered 
                 A tapered magnetic 
                 Linearizes the magnetic 
                 Complex construction 
                 IJ14 
               
               
                 magnetic 
                 pole can increase travel 
                 force/distance curve 
               
               
                 pole 
                 at the expense of force. 
               
               
                 Lever 
                 A lever and fulcrum is 
                 Matches low travel 
                 High stress around the 
                 IJ32, IJ36, IJ37 
               
               
                   
                 used to transform a 
                 actuator with higher 
                 fulcrum 
               
               
                   
                 motion with small 
                 travel requirements 
               
               
                   
                 travel and high force 
                 Fulcrum area has no 
               
               
                   
                 into a motion with 
                 linear movement, and 
               
               
                   
                 longer travel and lower 
                 can be used for a fluid 
               
               
                   
                 force. The lever can 
                 seal 
               
               
                   
                 also reverse the 
               
               
                   
                 direction of travel. 
               
               
                 Rotary 
                 The actuator is 
                 High mechanical 
                 Complex construction 
                 IJ28 
               
               
                 impeller 
                 connected to a rotary 
                 advantage 
                 Unsuitable for 
               
               
                   
                 impeller. A small 
                 The ratio of force to 
                 pigmented inks 
               
               
                   
                 angular deflection of 
                 travel of the actuator 
               
               
                   
                 the actuator results in a 
                 can be matched to the 
               
               
                   
                 rotation of the impeller 
                 nozzle requirements by 
               
               
                   
                 vanes, which push the 
                 varying the number of 
               
               
                   
                 ink against stationary 
                 impeller vanes 
               
               
                   
                 vanes and out of the 
               
               
                   
                 nozzle. 
               
               
                 Acoustic lens 
                 A refractive or 
                 No moving parts 
                 Large area required 
                 1993 Hadimioglu et al, 
               
               
                   
                 diffractive (e.g. zone 
                   
                 Only relevant for 
                 EUP 550,192 
               
               
                   
                 plate) acoustic lens is 
                   
                 acoustic ink jets 
                 1993 Elrod et al, EUP 
               
               
                   
                 used to concentrate 
                   
                   
                 572,220 
               
               
                   
                 sound waves. 
               
               
                 Sharp 
                 A sharp point is used to 
                 Simple construction 
                 Difficult to fabricate 
                 Tone-jet 
               
               
                 conductive 
                 concentrate an 
                   
                 using standard VLSI 
               
               
                 point 
                 electrostatic field. 
                   
                 processes for a surface 
               
               
                   
                   
                   
                 ejecting ink-jet 
               
               
                   
                   
                   
                 Only relevant for 
               
               
                   
                   
                   
                 electrostatic ink jets 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 Actuator motion 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Volume 
                 The volume of the 
                 Simple construction in 
                 High energy is 
                 Hewlett-Packard 
               
               
                 expansion 
                 actuator changes, 
                 the case of thermal ink 
                 typically required to 
                 Thermal Ink jet 
               
               
                   
                 pushing the ink in all 
                 jet 
                 achieve volume 
                 Canon Bubblejet 
               
               
                   
                 directions. 
                   
                 expansion. This leads 
               
               
                   
                   
                   
                 to thermal stress, 
               
               
                   
                   
                   
                 cavitation, and 
               
               
                   
                   
                   
                 kogation in thermal ink 
               
               
                   
                   
                   
                 jet implementations 
               
               
                 Linear, 
                 The actuator moves in a 
                 Efficient coupling to 
                 High fabrication 
                 IJ01, IJ02, IJ04, IJ07, 
               
               
                 normal to 
                 direction normal to the 
                 ink drops ejected 
                 complexity may be 
                 IJ11, IJ14 
               
               
                 chip surface 
                 print head surface. The 
                 normal to the surface 
                 required to achieve 
               
               
                   
                 nozzle is typically in 
                   
                 perpendicular motion 
               
               
                   
                 the line of movement. 
               
               
                 Parallel to 
                 The actuator moves 
                 Suitable for planar 
                 Fabrication complexity 
                 IJ12, IJ13, IJ15, IJ33, , 
               
               
                 chip surface 
                 parallel to the print 
                 fabrication 
                 Friction 
                 IJ34, IJ35, IJ36 
               
               
                   
                 head surface. Drop 
                   
                 Stiction 
               
               
                   
                 ejection may still be 
               
               
                   
                 normal to the surface. 
               
               
                 Membrane 
                 An actuator with a high 
                 The effective area of 
                 Fabrication complexity 
                 1982 Howkins U.S. 
               
               
                 push 
                 force but small area is 
                 the actuator becomes 
                 Actuator size 
                 Pat. No. 4,459,601 
               
               
                   
                 used to push a stiff 
                 the membrane area 
                 Difficulty of integration 
               
               
                   
                 membrane that is in 
                   
                 in a VLSI process 
               
               
                   
                 contact with the ink. 
               
               
                 Rotary 
                 The actuator causes the 
                 Rotary levers may be 
                 Device complexity 
                 IJ05, IJ08, IJ13, IJ28 
               
               
                   
                 rotation of some 
                 used to increase travel 
                 May have friction at a 
               
               
                   
                 element, such a grill or 
                 Small chip area 
                 pivot point 
               
               
                   
                 impeller 
                 requirements 
               
               
                 Bend 
                 The actuator bends 
                 A very small change in 
                 Requires the actuator to 
                 1970 Kyser et al U.S. 
               
               
                   
                 when energized. This 
                 dimensions can be 
                 be made from at least 
                 Pat. No. 3,946,398 
               
               
                   
                 may be due to 
                 converted to a large 
                 two distinct layers, or 
                 1973 Stemme U.S. 
               
               
                   
                 differential thermal 
                 motion. 
                 to have a thermal 
                 Pat. No. 3,747,120 
               
               
                   
                 expansion, 
                   
                 difference across the 
                 IJ03, IJ09, IJ10, IJ19, 
               
               
                   
                 piezoelectric 
                   
                 actuator 
                 IJ23, IJ24, IJ25, IJ29, 
               
               
                   
                 expansion, 
                   
                   
                 IJ30, IJ31, IJ33, IJ34, 
               
               
                   
                 magnetostriction, or 
                   
                   
                 IJ35 
               
               
                   
                 other form of relative 
               
               
                   
                 dimensional change. 
               
               
                 Swivel 
                 The actuator swivels 
                 Allows operation 
                 Inefficient coupling to 
                 IJ06 
               
               
                   
                 around a central pivot. 
                 where the net linear 
                 the ink motion 
               
               
                   
                 This motion is suitable 
                 force on the paddle is 
               
               
                   
                 where there are 
                 zero 
               
               
                   
                 opposite forces applied 
                 Small chip area 
               
               
                   
                 to opposite sides of the 
                 requirements 
               
               
                   
                 paddle, e.g. Lorenz 
               
               
                   
                 force. 
               
               
                 Straighten 
                 The actuator is 
                 Can be used with shape 
                 Requires careful 
                 IJ26, IJ32 
               
               
                   
                 normally bent, and 
                 memory alloys where 
                 balance of stresses to 
               
               
                   
                 straightens when 
                 the austenic phase is 
                 ensure that the 
               
               
                   
                 energized. 
                 planar 
                 quiescent bend is 
               
               
                   
                   
                   
                 accurate 
               
               
                 Double bend 
                 The actuator bends in 
                 One actuator can be 
                 Difficult to make the 
                 IJ36, IJ37, IJ38 
               
               
                   
                 one direction when one 
                 used to power two 
                 drops ejected by both 
               
               
                   
                 element is energized, 
                 nozzles. 
                 bend directions 
               
               
                   
                 and bends the other 
                 Reduced chip size. 
                 identical. 
               
               
                   
                 way when another 
                 Not sensitive to 
                 A small efficiency loss 
               
               
                   
                 element is energized. 
                 ambient temperature 
                 compared to equivalent 
               
               
                   
                   
                   
                 single bend actuators. 
               
               
                 Shear 
                 Energizing the actuator 
                 Can increase the 
                 Not readily applicable 
                 1985 Fishbeck U.S. 
               
               
                   
                 causes a shear motion 
                 effective travel of 
                 to other actuator 
                 Pat. No. 4,584,590 
               
               
                   
                 in the actuator material. 
                 piezoelectric actuators 
                 mechanisms 
               
               
                 Radial 
                 The actuator squeezes 
                 Relatively easy to 
                 High force required 
                 1970 Zoltan U.S. 
               
               
                 constriction 
                 an ink reservoir, 
                 fabricate single nozzles 
                 Inefficient 
                 Pat. No. 3,683,212 
               
               
                   
                 forcing ink from a 
                 from glass tubing as 
                 Difficult to integrate 
               
               
                   
                 constricted nozzle. 
                 macroscopic structures 
                 with VLSI processes 
               
               
                 Coil/uncoil 
                 A coiled actuator 
                 Easy to fabricate as a 
                 Difficult to fabricate for 
                 IJ17, IJ21, IJ34, IJ35 
               
               
                   
                 uncoils or coils more 
                 planar VLSI process 
                 non-planar devices 
               
               
                   
                 tightly. The motion of 
                 Small area required, 
                 Poor out-of-plane 
               
               
                   
                 the free end of the 
                 therefore low cost 
                 stiffness 
               
               
                   
                 actuator ejects the ink. 
               
               
                 Bow 
                 The actuator bows (or 
                 Can increase the speed 
                 Maximum travel is 
                 IJ16, IJ18, IJ27 
               
               
                   
                 buckles) in the middle 
                 of travel 
                 constrained 
               
               
                   
                 when energized. 
                 Mechanically rigid 
                 High force required 
               
               
                 Push-Pull 
                 Two actuators control a 
                 The structure is pinned 
                 Not readily suitable for 
                 IJ18 
               
               
                   
                 shutter. One actuator 
                 at both ends, so has a 
                 ink jets which directly 
               
               
                   
                 pulls the shutter, and 
                 high out-of-plane 
                 push the ink 
               
               
                   
                 the other pushes it. 
                 rigidity 
               
               
                 Curl inwards 
                 A set of actuators curl 
                 Good fluid flow to the 
                 Design complexity 
                 IJ20, IJ42 
               
               
                   
                 inwards to reduce the 
                 region behind the 
               
               
                   
                 volume of ink that they 
                 actuator increases 
               
               
                   
                 enclose. 
                 efficiency 
               
               
                 Curl 
                 A set of actuators curl 
                 Relatively simple 
                 Relatively large chip 
                 IJ43 
               
               
                 outwards 
                 outwards, pressurizing 
                 construction 
                 area 
               
               
                   
                 ink in a chamber 
               
               
                   
                 surrounding the 
               
               
                   
                 actuators, and expelling 
               
               
                   
                 ink from a nozzle in the 
               
               
                   
                 chamber. 
               
               
                 Iris 
                 Multiple vanes enclose 
                 High efficiency 
                 High fabrication 
                 IJ22 
               
               
                   
                 a volume of ink. These 
                 Small chip area 
                 complexity 
               
               
                   
                 simultaneously rotate, 
                   
                 Not suitable for 
               
               
                   
                 reducing the volume 
                   
                 pigmented inks 
               
               
                   
                 between the vanes. 
               
               
                 Acoustic 
                 The actuator vibrates at 
                 The actuator can be 
                 Large area required for 
                 1993 Hadimioglu et al, 
               
               
                 vibration 
                 a high frequency. 
                 physically distant from 
                 efficient operation at 
                 EUP 550,192 
               
               
                   
                   
                 the ink 
                 useful frequencies 
                 1993 Elrod et al, EUP 
               
               
                   
                   
                   
                 Acoustic coupling and 
                 572,220 
               
               
                   
                   
                   
                 crosstalk 
               
               
                   
                   
                   
                 Complex drive circuitry 
               
               
                   
                   
                   
                 Poor control of drop 
               
               
                   
                   
                   
                 volume and position 
               
               
                 None 
                 In various ink jet 
                 No moving parts 
                 Various other tradeoffs 
                 Silverbrook, EP 0771 
               
               
                   
                 designs the actuator 
                   
                 are required to 
                 658 A2 and related 
               
               
                   
                 does not move. 
                   
                 eliminate moving parts 
                 patent applications 
               
               
                   
                   
                   
                   
                 Tone-jet 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 Nozzle refill method 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Surface 
                 This is the normal way 
                 Fabrication simplicity 
                 Low speed 
                 Thermal ink jet 
               
               
                 tension 
                 that ink jets are refilled. 
                 Operational simplicity 
                 Surface tension force 
                 Piezoelectric ink jet 
               
               
                   
                 After the actuator is 
                   
                 relatively small 
                 IJ01-IJ07, IJ10-IJ14, 
               
               
                   
                 energized, it typically 
                   
                 compared to actuator 
                 IJ16, IJ20, IJ22-IJ45 
               
               
                   
                 returns rapidly to its 
                   
                 force 
               
               
                   
                 normal position. This 
                   
                 Long refill time usually 
               
               
                   
                 rapid return sucks in air 
                   
                 dominates the total 
               
               
                   
                 through the nozzle 
                   
                 repetition rate 
               
               
                   
                 opening. The ink 
               
               
                   
                 surface tension at the 
               
               
                   
                 nozzle then exerts a 
               
               
                   
                 small force restoring 
               
               
                   
                 the meniscus to a 
               
               
                   
                 minimum area. This 
               
               
                   
                 force refills the nozzle. 
               
               
                 Shuttered 
                 Ink to the nozzle 
                 High speed 
                 Requires common ink 
                 IJ08, IJ13, IJ15, IJ17, 
               
               
                 oscillating 
                 chamber is provided at 
                 Low actuator energy, as 
                 pressure oscillator 
                 IJ18, IJ19, IJ21 
               
               
                 ink pressure 
                 a pressure that 
                 the actuator need only 
                 May not be suitable for 
               
               
                   
                 oscillates at twice the 
                 open or close the 
                 pigmented inks 
               
               
                   
                 drop ejection 
                 shutter, instead of 
               
               
                   
                 frequency. When a 
                 ejecting the ink drop 
               
               
                   
                 drop is to be ejected, 
               
               
                   
                 the shutter is opened 
               
               
                   
                 for 3 half cycles: drop 
               
               
                   
                 ejection, actuator 
               
               
                   
                 return, and refill. The 
               
               
                   
                 shutter is then closed to 
               
               
                   
                 prevent the nozzle 
               
               
                   
                 chamber emptying 
               
               
                   
                 during the next 
               
               
                   
                 negative pressure cycle. 
               
               
                 Refill 
                 After the main actuator 
                 High speed, as the 
                 Requires two 
                 IJ09 
               
               
                 actuator 
                 has ejected a drop a 
                 nozzle is actively 
                 independent actuators 
               
               
                   
                 second (refill) actuator 
                 refilled 
                 per nozzle 
               
               
                   
                 is energized. The refill 
               
               
                   
                 actuator pushes ink into 
               
               
                   
                 the nozzle chamber. 
               
               
                   
                 The refill actuator 
               
               
                   
                 returns slowly, to 
               
               
                   
                 prevent its return from 
               
               
                   
                 emptying the chamber 
               
               
                   
                 again. 
               
               
                 Positive ink 
                 The ink is held a slight 
                 High refill rate, 
                 Surface spill must be 
                 Silverbrook, EP 0771 
               
               
                 pressure 
                 positive pressure. After 
                 therefore a high drop 
                 prevented 
                 658 A2 and related 
               
               
                   
                 the ink drop is ejected, 
                 repetition rate is 
                 Highly hydrophobic 
                 patent applications 
               
               
                   
                 the nozzle chamber fills 
                 possible 
                 print head surfaces are 
                 Alternative for:, IJ01- 
               
               
                   
                 quickly as surface 
                   
                 required 
                 IJ07, IJ10-IJ14, IJ16, 
               
               
                   
                 tension and ink 
                   
                   
                 IJ20, IJ22-IJ45 
               
               
                   
                 pressure both operate to 
               
               
                   
                 refill the nozzle. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 Method of restricting back-flow through inlet 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Long inlet 
                 The ink inlet channel to 
                 Design simplicity 
                 Restricts refill rate 
                 Thermal ink jet 
               
               
                 channel 
                 the nozzle chamber is 
                 Operational simplicity 
                 May result in a 
                 Piezoelectric ink jet 
               
               
                   
                 made long and 
                 Reduces crosstalk 
                 relatively large chip 
                 IJ42, IJ43 
               
               
                   
                 relatively narrow, 
                   
                 area 
               
               
                   
                 relying on viscous drag 
                   
                 Only partially effective 
               
               
                   
                 to reduce inlet back- 
               
               
                   
                 flow. 
               
               
                 Positive ink 
                 The ink is under a 
                 Drop selection and 
                 Requires a method 
                 Silverbrook, EP 0771 
               
               
                 pressure 
                 positive pressure, so 
                 separation forces can 
                 (such as a nozzle rim or 
                 658 A2 and related 
               
               
                   
                 that in the quiescent 
                 be reduced 
                 effective 
                 patent applications 
               
               
                   
                 state some of the ink 
                 Fast refill time 
                 hydrophobizing, or 
                 Possible operation of 
               
               
                   
                 drop already protrudes 
                   
                 both) to prevent 
                 the following: IJ01- 
               
               
                   
                 from the nozzle. 
                   
                 flooding of the ejection 
                 IJ07, IJ09-IJ12, IJ14, 
               
               
                   
                 This reduces the 
                   
                 surface of the print 
                 IJ16, IJ20, IJ22, , IJ23- 
               
               
                   
                 pressure in the nozzle 
                   
                 head. 
                 IJ34, IJ36-IJ41, IJ44 
               
               
                   
                 chamber which is 
               
               
                   
                 required to eject a 
               
               
                   
                 certain volume of ink. 
               
               
                   
                 The reduction in 
               
               
                   
                 chamber pressure 
               
               
                   
                 results in a reduction in 
               
               
                   
                 ink pushed out through 
               
               
                   
                 the inlet. 
               
               
                 Baffle 
                 One or more baffles are 
                 The refill rate is not as 
                 Design complexity 
                 HP Thermal Ink Jet 
               
               
                   
                 placed in the inlet ink 
                 restricted as the long 
                 May increase 
                 Tektronix piezoelectric 
               
               
                   
                 flow. When the 
                 inlet method. 
                 fabrication complexity 
                 ink jet 
               
               
                   
                 actuator is energized, 
                 Reduces crosstalk 
                 (e.g. Tektronix hot melt 
               
               
                   
                 the rapid ink movement 
                   
                 Piezoelectric print 
               
               
                   
                 creates eddies which 
                   
                 heads). 
               
               
                   
                 restrict the flow 
               
               
                   
                 through the inlet. The 
               
               
                   
                 slower refill process is 
               
               
                   
                 unrestricted, and does 
               
               
                   
                 not result in eddies. 
               
               
                 Flexible flap 
                 In this method recently 
                 Significantly reduces 
                 Not applicable to most 
                 Canon 
               
               
                 restricts inlet 
                 disclosed by Canon, the 
                 back-flow for edge- 
                 ink jet configurations 
               
               
                   
                 expanding actuator 
                 shooter thermal ink jet 
                 Increased fabrication 
               
               
                   
                 (bubble) pushes on a 
                 devices 
                 complexity 
               
               
                   
                 flexible flap that 
                   
                 Inelastic deformation of 
               
               
                   
                 restricts the inlet. 
                   
                 polymer flap results in 
               
               
                   
                   
                   
                 creep over extended 
               
               
                   
                   
                   
                 use 
               
               
                 Inlet filter 
                 A filter is located 
                 Additional advantage 
                 Restricts refill rate 
                 IJ04, IJ12, IJ24, IJ27, 
               
               
                   
                 between the ink inlet 
                 of ink filtration 
                 May result in complex 
                 IJ29, IJ30 
               
               
                   
                 and the nozzle 
                 Ink filter may be 
                 construction 
               
               
                   
                 chamber. The filter has 
                 fabricated with no 
               
               
                   
                 a multitude of small 
                 additional process steps 
               
               
                   
                 holes or slots, 
               
               
                   
                 restricting ink flow. 
               
               
                   
                 The filter also removes 
               
               
                   
                 particles which may 
               
               
                   
                 block the nozzle. 
               
               
                 Small inlet 
                 The ink inlet channel to 
                 Design simplicity 
                 Restricts refill rate 
                 IJ02, IJ37, IJ44 
               
               
                 compared to 
                 the nozzle chamber has 
                   
                 May result in a 
               
               
                 nozzle 
                 a substantially smaller 
                   
                 relatively large chip 
               
               
                   
                 cross section than that 
                   
                 area 
               
               
                   
                 of the nozzle, resulting 
                   
                 Only partially effective 
               
               
                   
                 in easier ink egress out 
               
               
                   
                 of the nozzle than out 
               
               
                   
                 of the inlet. 
               
               
                 Inlet shutter 
                 A secondary actuator 
                 Increases speed of the 
                 Requires separate refill 
                 IJ09 
               
               
                   
                 controls the position of 
                 ink-jet print head 
                 actuator and drive 
               
               
                   
                 a shutter, closing off 
                 operation 
                 circuit 
               
               
                   
                 the ink inlet when the 
               
               
                   
                 main actuator is 
               
               
                   
                 energized. 
               
               
                 The inlet is 
                 The method avoids the 
                 Back-flow problem is 
                 Requires careful design 
                 IJ01, IJ03, IJ05, IJ06, 
               
               
                 located 
                 problem of inlet back- 
                 eliminated 
                 to minimize the 
                 IJ07, IJ10, IJ11, IJ14, 
               
               
                 behind the 
                 flow by arranging the 
                   
                 negative pressure 
                 IJ16, IJ22, IJ23, IJ25, 
               
               
                 ink-pushing 
                 ink-pushing surface of 
                   
                 behind the paddle 
                 IJ28, IJ31, IJ32, IJ33, 
               
               
                 surface 
                 the actuator between 
                   
                   
                 IJ34, IJ35, IJ36, IJ39, 
               
               
                   
                 the inlet and the nozzle. 
                   
                   
                 IJ40, IJ41 
               
               
                 Part of the 
                 The actuator and a wall 
                 Significant reductions 
                 Small increase in 
                 IJ07, IJ20, IJ26, IJ38 
               
               
                 actuator 
                 of the ink chamber are 
                 in back-flow can be 
                 fabrication complexity 
               
               
                 moves to 
                 arranged so that the 
                 achieved 
               
               
                 shut off the 
                 motion of the actuator 
                 Compact designs 
               
               
                 inlet 
                 closes off the inlet. 
                 possible 
               
               
                 Nozzle 
                 In some configurations 
                 Ink back-flow problem 
                 None related to ink 
                 Silverbrook, EP 0771 
               
               
                 actuator does 
                 of ink jet, there is no 
                 is eliminated 
                 back-flow on actuation 
                 658 A2 and related 
               
               
                 not result in 
                 expansion or 
                   
                   
                 patent applications 
               
               
                 ink back- 
                 movement of an 
                   
                   
                 Valve-jet 
               
               
                 flow 
                 actuator which may 
                   
                   
                 Tone-jet 
               
               
                   
                 cause ink back-flow 
               
               
                   
                 through the inlet. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 Nozzle Clearing Method 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Normal 
                 All of the nozzles are 
                 No added complexity 
                 May not be sufficient to 
                 Most ink jet systems 
               
               
                 nozzle firing 
                 fired periodically, 
                 on the print head 
                 displace dried ink 
                 IJ01, IJ02, IJ03, IJ04, 
               
               
                   
                 before the ink has a 
                   
                   
                 IJ05, IJ06, IJ07, IJ09, 
               
               
                   
                 chance to dry. When 
                   
                   
                 IJ10, IJ11, IJ12, IJ14, 
               
               
                   
                 not in use the nozzles 
                   
                   
                 IJ16, IJ20, IJ22, IJ23, 
               
               
                   
                 are sealed (capped) 
                   
                   
                 IJ24, IJ25, IJ26, IJ27, 
               
               
                   
                 against air. 
                   
                   
                 IJ28, IJ29, IJ30, IJ31, 
               
               
                   
                 The nozzle firing is 
                   
                   
                 IJ32, IJ33, IJ34, IJ36, 
               
               
                   
                 usually performed 
                   
                   
                 IJ37, IJ38, IJ39, IJ40,, 
               
               
                   
                 during a special 
                   
                   
                 IJ41, IJ42, IJ43, IJ44,, 
               
               
                   
                 clearing cycle, after 
                   
                   
                 IJ45 
               
               
                   
                 first moving the print 
               
               
                   
                 head to a cleaning 
               
               
                   
                 station. 
               
               
                 Extra power 
                 In systems which heat 
                 Can be highly effective 
                 Requires higher drive 
                 Silverbrook, EP 0771 
               
               
                 to ink heater 
                 the ink, but do not boil 
                 if the heater is adjacent 
                 voltage for clearing 
                 658 A2 and related 
               
               
                   
                 it under normal 
                 to the nozzle 
                 May require larger 
                 patent applications 
               
               
                   
                 situations, nozzle 
                   
                 drive transistors 
               
               
                   
                 clearing can be 
               
               
                   
                 achieved by over- 
               
               
                   
                 powering the heater 
               
               
                   
                 and boiling ink at the 
               
               
                   
                 nozzle. 
               
               
                 Rapid 
                 The actuator is fired in 
                 Does not require extra 
                 Effectiveness depends 
                 May be used with: 
               
               
                 success-ion 
                 rapid succession. In 
                 drive circuits on the 
                 substantially upon the 
                 IJ01, IJ02, IJ03, IJ04, 
               
               
                 of actuator 
                 some configurations, 
                 print head 
                 configuration of the ink 
                 IJ05, IJ06, IJ07, IJ09, 
               
               
                 pulses 
                 this may cause heat 
                 Can be readily 
                 jet nozzle 
                 IJ10, IJ11, IJ14, IJ16, 
               
               
                   
                 build-up at the nozzle 
                 controlled and initiated 
                   
                 IJ20, IJ22, IJ23, IJ24, 
               
               
                   
                 which boils the ink, 
                 by digital logic 
                   
                 IJ25, IJ27, IJ28, IJ29, 
               
               
                   
                 clearing the nozzle. In 
                   
                   
                 IJ30, IJ31, IJ32, IJ33, 
               
               
                   
                 other situations, it may 
                   
                   
                 IJ34, IJ36, IJ37, IJ38, 
               
               
                   
                 cause sufficient 
                   
                   
                 IJ39, IJ40, IJ41, IJ42, 
               
               
                   
                 vibrations to dislodge 
                   
                   
                 IJ43, IJ44, IJ45 
               
               
                   
                 clogged nozzles. 
               
               
                 Extra power 
                 Where an actuator is 
                 A simple solution 
                 Not suitable where 
                 May be used with: 
               
               
                 to ink 
                 not normally driven to 
                 where applicable 
                 there is a hard limit to 
                 IJ03, IJ09, IJ16, IJ20, 
               
               
                 pushing 
                 the limit of its motion, 
                   
                 actuator movement 
                 IJ23, IJ24, IJ25, IJ27, 
               
               
                 actuator 
                 nozzle clearing may be 
                   
                   
                 IJ29, IJ30, IJ31, IJ32, 
               
               
                   
                 assisted by providing 
                   
                   
                 IJ39, IJ40, IJ41, IJ42, 
               
               
                   
                 an enhanced drive 
                   
                   
                 IJ43, IJ44, IJ45 
               
               
                   
                 signal to the actuator. 
               
               
                 Acoustic 
                 An ultrasonic wave is 
                 A high nozzle clearing 
                 High implementation 
                 IJ08, IJ13, IJ15, IJ17, 
               
               
                 resonance 
                 applied to the ink 
                 capability can be 
                 cost if system does not 
                 IJ18, IJ19, IJ21 
               
               
                   
                 chamber. This wave is 
                 achieved 
                 already include an 
               
               
                   
                 of an appropriate 
                 May be implemented at 
                 acoustic actuator 
               
               
                   
                 amplitude and 
                 very low cost in 
               
               
                   
                 frequency to cause 
                 systems which already 
               
               
                   
                 sufficient force at the 
                 include acoustic 
               
               
                   
                 nozzle to clear 
                 actuators 
               
               
                   
                 blockages. This is 
               
               
                   
                 easiest to achieve if the 
               
               
                   
                 ultrasonic wave is at a 
               
               
                   
                 resonant frequency of 
               
               
                   
                 the ink cavity. 
               
               
                 Nozzle 
                 A microfabricated plate 
                 Can clear severely 
                 Accurate mechanical 
                 Silverbrook, EP 0771 
               
               
                 clearing plate 
                 is pushed against the 
                 clogged nozzles 
                 alignment is required 
                 658 A2 and related 
               
               
                   
                 nozzles. The plate has a 
                   
                 Moving parts are 
                 patent applications 
               
               
                   
                 post for every nozzle. 
                   
                 required 
               
               
                   
                 A post moves through 
                   
                 There is risk of damage 
               
               
                   
                 each nozzle, displacing 
                   
                 to the nozzles 
               
               
                   
                 dried ink. 
                   
                 Accurate fabrication is 
               
               
                   
                   
                   
                 required 
               
               
                 Ink pressure 
                 The pressure of the ink 
                 May be effective where 
                 Requires pressure 
                 May be used with all IJ 
               
               
                 pulse 
                 is temporarily increased 
                 other methods cannot 
                 pump or other pressure 
                 series ink jets 
               
               
                   
                 so that ink streams 
                 be used 
                 actuator 
               
               
                   
                 from all of the nozzles. 
                   
                 Expensive 
               
               
                   
                 This may be used in 
                   
                 Wasteful of ink 
               
               
                   
                 conjunction with 
               
               
                   
                 actuator energizing. 
               
               
                 Print head 
                 A flexible ‘blade’ is 
                 Effective for planar 
                 Difficult to use if print 
                 Many ink jet systems 
               
               
                 wiper 
                 wiped across the print 
                 print head surfaces 
                 head surface is non- 
               
               
                   
                 head surface. The blade 
                 Low cost 
                 planar or very fragile 
               
               
                   
                 is usually fabricated 
                   
                 Requires mechanical 
               
               
                   
                 from a flexible 
                   
                 parts 
               
               
                   
                 polymer, e.g. rubber or 
                   
                 Blade can wear out in 
               
               
                   
                 synthetic elastomer. 
                   
                 high volume print 
               
               
                   
                   
                   
                 systems 
               
               
                 Separate ink 
                 A separate heater is 
                 Can be effective where 
                 Fabrication complexity 
                 Can be used with many 
               
               
                 boiling 
                 provided at the nozzle 
                 other nozzle clearing 
                   
                 IJ series ink jets 
               
               
                 heater 
                 although the normal 
                 methods cannot be used 
               
               
                   
                 drop ejection 
                 Can be implemented at 
               
               
                   
                 mechanism does not 
                 no additional cost in 
               
               
                   
                 require it. The heaters 
                 some ink jet 
               
               
                   
                 do not require 
                 configurations 
               
               
                   
                 individual drive 
               
               
                   
                 circuits, as many 
               
               
                   
                 nozzles can be cleared 
               
               
                   
                 simultaneously, and no 
               
               
                   
                 imaging is required. 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 Nozzle plate construction 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Electro- 
                 A nozzle plate is 
                 Fabrication simplicity 
                 High temperatures and 
                 Hewlett Packard 
               
               
                 formed 
                 separately fabricated 
                   
                 pressures are required 
                 Thermal Ink jet 
               
               
                 nickel 
                 from electroformed 
                   
                 to bond nozzle plate 
               
               
                   
                 nickel, and bonded to 
                   
                 Minimum thickness 
               
               
                   
                 the print head chip. 
                   
                 constraints 
               
               
                   
                   
                   
                 Differential thermal 
               
               
                   
                   
                   
                 expansion 
               
               
                 Laser ablated 
                 Individual nozzle holes 
                 No masks required 
                 Each hole must be 
                 Canon Bubblejet 
               
               
                 or drilled 
                 are ablated by an 
                 Can be quite fast 
                 individually formed 
                 1988 Sercel et al., 
               
               
                 polymer 
                 intense UV laser in a 
                 Some control over 
                 Special equipment 
                 SPIE, Vol. 998 
               
               
                   
                 nozzle plate, which is 
                 nozzle profile is 
                 required 
                 Excimer Beam 
               
               
                   
                 typically a polymer 
                 possible 
                 Slow where there are 
                 Applications, pp. 76-83 
               
               
                   
                 such as polyimide or 
                 Equipment required is 
                 many thousands of 
                 1993 Watanabe et al., 
               
               
                   
                 polysulphone 
                 relatively low cost 
                 nozzles per print head 
                 U.S. Pat. No. 5,208,604 
               
               
                   
                   
                   
                 May produce thin burrs 
               
               
                   
                   
                   
                 at exit holes 
               
               
                 Silicon 
                 A separate nozzle plate 
                 High accuracy is 
                 Two part construction 
                 K. Bean, IEEE 
               
               
                 micro- 
                 is micromachined from 
                 attainable 
                 High cost 
                 Transactions on 
               
               
                 machined 
                 single crystal silicon, 
                   
                 Requires precision 
                 Electron Devices, Vol. 
               
               
                   
                 and bonded to the print 
                   
                 alignment 
                 ED-25, No. 10, 1978, 
               
               
                   
                 head wafer. 
                   
                 Nozzles may be 
                 pp 1185-1195 
               
               
                   
                   
                   
                 clogged by adhesive 
                 Xerox 1990 Hawkins et 
               
               
                   
                   
                   
                   
                 al., U.S. Pat. No. 4,899,181 
               
               
                 Glass 
                 Fine glass capillaries 
                 No expensive 
                 Very small nozzle sizes 
                 1970 Zoltan U.S. 
               
               
                 capillaries 
                 are drawn from glass 
                 equipment required 
                 are difficult to form 
                 Pat. No. 3,683,212 
               
               
                   
                 tubing. This method 
                 Simple to make single 
                 Not suited for mass 
               
               
                   
                 has been used for 
                 nozzles 
                 production 
               
               
                   
                 making individual 
               
               
                   
                 nozzles, but is difficult 
               
               
                   
                 to use for bulk 
               
               
                   
                 manufacturing of print 
               
               
                   
                 heads with thousands 
               
               
                   
                 of nozzles. 
               
               
                 Monolithic, 
                 The nozzle plate is 
                 High accuracy (&lt;1 
                 Requires sacrificial 
                 Silverbrook, EP 0771 
               
               
                 surface 
                 deposited as a layer 
                 micron) 
                 layer under the nozzle 
                 658 A2 and related 
               
               
                 micro- 
                 using standard VLSI 
                 Monolithic 
                 plate to form the nozzle 
                 patent applications 
               
               
                 machined 
                 deposition techniques. 
                 Low cost 
                 chamber 
                 IJ01, IJ02, IJ04, IJ11, 
               
               
                 using VLSI 
                 Nozzles are etched in 
                 Existing processes can 
                 Surface may be fragile 
                 IJ12, IJ17, IJ18, IJ20, 
               
               
                 litho-graphic 
                 the nozzle plate using 
                 be used 
                 to the touch 
                 IJ22, IJ24, IJ27, IJ28, 
               
               
                 processes 
                 VLSI lithography and 
                   
                   
                 IJ29, IJ30, IJ31, IJ32, 
               
               
                   
                 etching. 
                   
                   
                 IJ33, IJ34, IJ36, IJ37, 
               
               
                   
                   
                   
                   
                 IJ38, IJ39, IJ40, IJ41, 
               
               
                   
                   
                   
                   
                 IJ42, IJ43, IJ44 
               
               
                 Monolithic, 
                 The nozzle plate is a 
                 High accuracy (&lt;1 
                 Requires long etch 
                 IJ03, IJ05, IJ06, IJ07, 
               
               
                 etched 
                 buried etch stop in the 
                 micron) 
                 times 
                 IJ08, IJ09, IJ10, IJ13, 
               
               
                 through 
                 wafer. Nozzle 
                 Monolithic 
                 Requires a support 
                 IJ14, IJ15, IJ16, IJ19, 
               
               
                 substrate 
                 chambers are etched in 
                 Low cost 
                 wafer 
                 IJ21, IJ23, IJ25, IJ26 
               
               
                   
                 the front of the wafer, 
                 No differential 
               
               
                   
                 and the wafer is thinned 
                 expansion 
               
               
                   
                 from the back side. 
               
               
                   
                 Nozzles are then etched 
               
               
                   
                 in the etch stop layer. 
               
               
                 No nozzle 
                 Various methods have 
                 No nozzles to become 
                 Difficult to control drop 
                 Ricoh 1995 Sekiya et al 
               
               
                 plate 
                 been tried to eliminate 
                 clogged 
                 position accurately 
                 U.S. Pat. No. 5,412,413 
               
               
                   
                 the nozzles entirely, to 
                   
                 Crosstalk problems 
                 1993 Hadimioglu et al 
               
               
                   
                 prevent nozzle 
                   
                   
                 EUP 550,192 
               
               
                   
                 clogging. These include 
                   
                   
                 1993 Elrod et al EUP 
               
               
                   
                 thermal bubble 
                   
                   
                 572,220 
               
               
                   
                 mechanisms and 
               
               
                   
                 acoustic lens 
               
               
                   
                 mechanisms 
               
               
                 Trough 
                 Each drop ejector has a 
                 Reduced manufacturing 
                 Drop firing direction is 
                 IJ35 
               
               
                   
                 trough through which a 
                 complexity 
                 sensitive to wicking. 
               
               
                   
                 paddle moves. There is 
                 Monolithic 
               
               
                   
                 no nozzle plate. 
               
               
                 Nozzle slit 
                 The elimination of 
                 No nozzles to become 
                 Difficult to control drop 
                 1989 Saito et al U.S. 
               
               
                 instead of 
                 nozzle holes and 
                 clogged 
                 position accurately 
                 Pat. No. 4,799,068 
               
               
                 individual 
                 replacement by a slit 
                   
                 Crosstalk problems 
               
               
                 nozzles 
                 encompassing many 
               
               
                   
                 actuator positions 
               
               
                   
                 reduces nozzle 
               
               
                   
                 clogging, but increases 
               
               
                   
                 crosstalk due to ink 
               
               
                   
                 surface waves 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 Drop ejection direction 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Description 
                 Advantages 
                 Disadvantages 
                 Examples 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Edge 
                 Ink flow is along the 
                 Simple construction 
                 Nozzles limited to edge 
                 Canon Bubblejet 1979 
               
               
                 (‘edge 
                 surface of the chip, and 
                 No silicon etching 
                 High resolution is 
                 Endo et al GB patent 
               
               
                 shooter’) 
                 ink drops are ejected 
                 required 
                 difficult 
                 2,007,162 
               
               
                   
                 from the chip edge. 
                 Good heat sinking via 
                 Fast color printing 
                 Xerox heater-in-pit 
               
               
                   
                   
                 substrate 
                 requires one print head 
                 1990 Hawkins et al 
               
               
                   
                   
                 Mechanically strong 
                 per color 
                 U.S. Pat. No. 4,899,181 
               
               
                   
                   
                 Ease of chip handing 
                   
                 Tone-jet 
               
               
                 Surface 
                 Ink flow is along the 
                 No bulk silicon etching 
                 Maximum ink flow is 
                 Hewlett-Packard TIJ 
               
               
                 (‘roof 
                 surface of the chip, and 
                 required 
                 severely restricted 
                 1982 Vaught et al U.S. 
               
               
                 shooter’) 
                 ink drops are ejected 
                 Silicon can make an 
                   
                 Pat. No. 4,490,728 
               
               
                   
                 from the chip surface, 
                 effective heat sink 
                   
                 IJ02, IJ11, IJ12, IJ20, 
               
               
                   
                 normal to the plane of 
                 Mechanical strength 
                   
                 IJ22 
               
               
                   
                 the chip. 
               
               
                 Through 
                 Ink flow is through the 
                 High ink flow 
                 Requires bulk silicon 
                 Silverbrook, EP 0771 
               
               
                 chip, forward 
                 chip, and ink drops are 
                 Suitable for pagewidth 
                 etching 
                 658 A2 and related 
               
               
                 (‘up 
                 ejected from the front 
                 print heads 
                   
                 patent applications 
               
               
                 shooter’) 
                 surface of the chip. 
                 High nozzle packing 
                   
                 IJ04, IJ17, IJ18, IJ24, 
               
               
                   
                   
                 density therefore low 
                   
                 IJ27-IJ45 
               
               
                   
                   
                 manufacturing cost 
               
               
                 Through 
                 Ink flow is through the 
                 High ink flow 
                 Requires wafer 
                 IJ01, IJ03, IJ05, IJ06, 
               
               
                 chip, reverse 
                 chip, and ink drops are 
                 Suitable for pagewidth 
                 thinning 
                 IJ07, IJ08, IJ09, IJ10, 
               
               
                 (‘down 
                 ejected from the rear 
                 print heads 
                 Requires special 
                 IJ13, IJ14, IJ15, IJ16, 
               
               
                 shooter’) 
                 surface of the chip. 
                 High nozzle packing 
                 handling during 
                 IJ19, IJ21, IJ23, IJ25, 
               
               
                   
                   
                 density therefore low 
                 manufacture 
                 IJ26 
               
               
                   
                   
                 manufacturing cost 
               
               
                 Through 
                 Ink flow is through the 
                 Suitable for 
                 Pagewidth print heads 
                 Epson Stylus 
               
               
                 actuator 
                 actuator, which is not 
                 piezoelectric print 
                 require several 
                 Tektronix hot melt 
               
               
                   
                 fabricated as part of the 
                 heads 
                 thousand connections 
                 piezoelectric ink jets 
               
               
                   
                 same substrate as the 
                   
                 to drive circuits 
               
               
                   
                 drive transistors. 
                   
                 Cannot be 
               
               
                   
                   
                   
                 manufactured in 
               
               
                   
                   
                   
                 standard CMOS fabs 
               
               
                   
                   
                   
                 Complex assembly 
               
               
                   
                   
                   
                 required 
               
               
                   
               
            
           
         
       
     
                            Ink type                                     Description   Advantages   Disadvantages   Examples                                             Aqueous,   Water based ink which   Environmentally   Slow drying   Most existing ink jets       dye   typically contains:   friendly   Corrosive   All IJ series ink jets           water, dye, surfactant,   No odor   Bleeds on paper   Silverbrook, EP 0771           humectant, and biocide.       May strikethrough   658 A2 and related           Modern ink dyes have       Cockles paper   patent applications           high water-fastness,           light fastness       Aqueous,   Water based ink which   Environmentally   Slow drying   IJ02, IJ04, IJ21, IJ26,       pigment   typically contains:   friendly   Corrosive   IJ27, IJ30           water, pigment,   No odor   Pigment may clog   Silverbrook, EP 0771           surfactant, humectant,   Reduced bleed   nozzles   658 A2 and related           and biocide.   Reduced wicking   Pigment may clog   patent applications           Pigments have an   Reduced strikethrough   actuator mechanisms   Piezoelectric ink-jets           advantage in reduced       Cockles paper   Thermal ink jets (with           bleed, wicking and           significant restrictions)           strikethrough.       Methyl Ethyl   MEK is a highly   Very fast drying   Odorous   All IJ series ink jets       Ketone   volatile solvent used for   Prints on various   Flammable       (MEK)   industrial printing on   substrates such as           difficult surfaces such   metals and plastics           as aluminum cans.       Alcohol   Alcohol based inks can   Fast drying   Slight odor   All IJ series ink jets       (ethanol, 2-   be used where the   Operates at sub-   Flammable       butanol, and   printer must operate at   freezing temperatures       others)   temperatures below the   Reduced paper cockle           freezing point of water.   Low cost           An example of this is           in-camera consumer           photographic printing.       Phase change   The ink is solid at room   No drying time—ink   High viscosity   Tektronix hot melt       (hot melt)   temperature, and is   instantly freezes on the   Printed ink typically   piezoelectric ink jets           melted in the print head   print medium   has a ‘waxy’ feel   1989 Nowak U.S.           before jetting. Hot melt   Almost any print   Printed pages may   Pat. No. 4,820,346           inks are usually wax   medium can be used   ‘block’   All IJ series ink jets           based, with a melting   No paper cockle occurs   Ink temperature may be           point around 80° C.   No wicking occurs   above the curie point of           After jetting the ink   No bleed occurs   permanent magnets           freezes almost instantly   No strikethrough   Ink heaters consume           upon contacting the   occurs   power           print medium or a       Long warm-up time           transfer roller.       Oil   Oil based inks are   High solubility medium   High viscosity: this is a   All IJ series ink jets           extensively used in   for some dyes   significant limitation           offset printing. They   Does not cockle paper   for use in ink jets,           have advantages in   Does not wick through   which usually require a           improved   paper   low viscosity. Some           characteristics on paper       short chain and multi-           (especially no wicking       branched oils have a           or cockle). Oil soluble       sufficiently low           dies and pigments are       viscosity.           required.       Slow drying       Micro-   A microemulsion is a   Stops ink bleed   Viscosity higher than   All IJ series ink jets       emulsion   stable, self forming   High dye solubility   water           emulsion of oil, water,   Water, oil, and   Cost is slightly higher           and surfactant. The   amphiphilic soluble   than water based ink           characteristic drop size   dies can be used   High surfactant           is less than 100 nm, and   Can stabilize pigment   concentration required           is determined by the   suspensions   (around 5%)           preferred curvature of           the surfactant.                    
IJ01
 
     In  FIG. 1 , there is illustrated an exploded perspective view illustrating the construction of a single ink jet nozzle  104  in accordance with the principles of the present invention. 
     The nozzle  104  operates on the principle of electromechanical energy conversion and comprises a solenoid  111  which is connected electrically at a first end  112  to a magnetic plate  113  which is in turn connected to a current source e.g.  114  utilized to activate the ink nozzle  104 . The magnetic plate  113  can be constructed from electrically conductive iron. 
     A second magnetic plunger  115  is also provided, again being constructed from soft magnetic iron. Upon energising the solenoid  111 , the plunger  115  is attracted to the fixed magnetic plate  113 . The plunger thereby pushes against the ink within the nozzle  104  creating a high pressure zone in the nozzle chamber  117 . This causes a movement of the ink in the nozzle chamber  117  and in a first design, subsequent ejection of an ink drop. A series of apertures e.g.  120  is provided so that ink in the region of solenoid  111  is squirted out of the holes  120  in the top of the plunger  115  as it moves towards lower plate  113 . This prevents ink trapped in the area of solenoid  111  from increasing the pressure on the plunger  115  and thereby increasing the magnetic forces needed to move the plunger  115 . 
     Referring now to  FIG. 2 , there is illustrated a timing diagram  130  of the plunger current control signal. Initially, a solenoid current pulse  131  is activated for the movement of the plunger and ejection of a drop from the ink nozzle. After approximately 2 micro-seconds, the current to the solenoid is turned off. At the same time or at a slightly later time, a reverse current pulse  132  is applied having approximately half the magnitude of the forward current. As the plunger has a residual magnetism, the reverse current pulse  132  causes the plunger to move backwards towards its original position. A series of torsional springs  122 ,  123  ( FIG. 1 ) also assists in the return of the plunger to its original position. The reverse current pulse  132  is turned off before the magnetism of the plunger  115  is reversed which would otherwise result in the plunger being attracted to the fixed plate  113  again. Returning to  FIG. 1 , the forced return of the plunger  115  to its quiescent position results in a low pressure in the chamber  117 . This can cause ink to begin flowing from the outlet nozzle  124  inwards and also ingests air to the chamber  117 . The forward velocity of the drop and the backward velocity of the ink in the chamber  117  are resolved by the ink drop breaking off around the nozzle  124 . The ink drop then continues to travel toward the recording medium under its own momentum. The nozzle refills due to the surface tension of the ink at the nozzle tip  124 . Shortly after the time of drop break off, a meniscus at the nozzle tip is formed with an approximately concave hemispherical surface. The surface tension will exert a net forward force on the ink which will result in nozzle refilling. The repetition rate of the nozzle  104  is therefore principally determined by the nozzle refill time which will be  100  microseconds, depending on the device geometry, ink surface tension and the volume of the ejected drop. 
     Turning now to  FIG. 3 , an important aspect of the operation of the electromagnetically driven print nozzle will now be described. Upon a current flowing through the coil  111 , the plate  115  becomes strongly attracted to the plate  113 . The plate  115  experiences a downward force and begins movement towards the plate  113 . This movement imparts a momentum to the ink within the nozzle chamber  117 . The ink is subsequently ejected as hereinbefore described. Unfortunately, the movement of the plate  115  causes a build-up of pressure in the area  164  between the plate  115  and the coil  111 . This build-up would normally result in a reduced effectiveness of the plate  115  in ejecting ink. 
     However, in a first design the plate  115  preferably includes a series of apertures e.g.  120  which allow for the flow of ink from the area  164  back into the ink chamber and thereby allow a reduction in the pressure in area  164 . This results in an increased effectiveness in the operation of the plate  115 . 
     Preferably, the apertures  120  are of a teardrop shape increasing in width with increasing radial distance from a centre of the plunger. The aperture profile thereby provides minimal disturbance of the magnetic flux through the plunger while maintaining structural integrity of plunger  115 . 
     After the plunger  115  has reached its end position, the current through coil  111  is reversed resulting in a repulsion of the two plates  113 ,  115 . Additionally, the torsional spring e.g.  123  acts to return the plate  115  to its initial position. 
     The use of a torsional spring e.g.  123  has a number of substantial benefits including a compact layout. The construction of the torsional spring from the same material and same processing steps as that of the plate  115  simplifies the manufacturing process. 
     In an alternative design, the top surface of plate  115  does not include a series of apertures. Rather, the inner radial surface  125  (see  FIG. 3 ) of plate  115  comprises slots of substantially constant cross-sectional profile in fluid communication between the nozzle chamber  117  and the area  164  between plate  115  and the solenoid  111 . Upon activation of the coil  111 , the plate  115  is attracted to the armature plate  113  and experiences a force directed towards plate  113 . As a result of the movement, fluid in the area  164  is compressed and experiences a higher pressure than its surrounds. As a result, the flow of fluid takes place out of the slots in the inner radial surface  125  plate  115  into the nozzle chamber  117 . The flow of fluid into chamber  117 , in addition to the movement of the plate  115 , causes the ejection of ink out of the ink nozzle port  124 . Again, the movement of the plate  115  causes the torsional springs, for example  123 , to be resiliently deformed. Upon completion of the movement of the plate  115 , the coil  111  is deactivated and a slight reverse current is applied. The reverse current acts to repel the plate  115  from the armature plate  113 . The torsional springs, for example  123 , act as additional means to return the plate  115  to its initial or quiescent position. 
     Fabrication 
     Returning now to  FIG. 1 , the nozzle apparatus is constructed from the following main parts including a nozzle surface  140  having an aperture  124  which can be constructed from boron doped silicon  150 . The radius of the aperture  124  of the nozzle is an important determinant of drop velocity and drop size. 
     Next, a CMOS silicon layer  142  is provided upon which is fabricated all the data storage and driving circuitry  141  necessary for the operation of the nozzle  4 . In this layer a nozzle chamber  117  is also constructed. The nozzle chamber  117  should be wide enough so that viscous drag from the chamber walls does not significantly increase the force required of the plunger. It should also be deep enough so that any air ingested through the nozzle port  124  when the plunger returns to its quiescent state does not extend to the plunger device. If it does, the ingested bubble may form a cylindrical surface instead of a hemispherical surface resulting in the nozzle not refilling properly. A CMOS dielectric and insulating layer  144  containing various current paths for the current connection to the plunger device is also provided. 
     Next, a fixed plate of ferroelectric material is provided having two parts  113 ,  146 . The two parts  113 ,  146  are electrically insulated from one another. 
     Next, a solenoid  111  is provided. This can comprise a spiral coil of deposited copper. Preferably a single spiral layer is utilized to avoid fabrication difficulty and copper is used for a low resistivity and high electro-migration resistance. 
     Next, a plunger  115  of ferromagnetic material is provided to maximise the magnetic force generated. The plunger  115  and fixed magnetic plate  113 ,  146  surround the solenoid  111  as a torus. Thus, little magnetic flux is lost and the flux is concentrated around the gap between the plunger  115  and the fixed plate  113 ,  146 . 
     The gap between the fixed plate  113 ,  146  and the plunger  115  is one of the most important “parts” of the print nozzle  104 . The size of the gap will strongly affect the magnetic force generated, and also limits the travel of the plunger  115 . A small gap is desirable to achieve a strong magnetic force, but a large gap is desirable to allow longer plunger  115  travel, and therefore allow a smaller plunger radius to be utilised. 
     Next, the springs, e.g.  122 ,  123  for returning to the plunger  115  to its quiescent position after a drop has been ejected are provided. The springs, e.g.  122 ,  123  can be fabricated from the same material, and in the same processing steps, as the plunger  115 . Preferably the springs, e.g.  122 ,  123  act as torsional springs in their interaction with the plunger  115 . 
     Finally, all surfaces are coated with passivation layers, which may be silicon nitride (Si 3 N 4 ), diamond like carbon (DLC), or other chemically inert, highly impermeable layer. The passivation layers are especially important for device lifetime, as the active device will be immersed in the ink. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer deposit 3 microns of epitaxial silicon heavily doped with boron  150 . 
     2. Deposit 10 microns of epitaxial silicon  142 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete a 0.5 micron, one poly, 2 metal CMOS process. This step is shown at  141  in  FIG. 5 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 4  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers  141  down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber, the edges of the print heads chips, and the vias for the contacts from the aluminum electrodes to the two halves of the split fixed magnetic plate. 
     5. Plasma etch the silicon  142  down to the boron doped buried layer  150 , using oxide from step 4 as a mask. This etch does not substantially etch the aluminum. This step is shown in  FIG. 6 . 
     6. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosen due to a high saturation flux density of 2 Tesla, and a low coercivity. [Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturation magnetic flux density, Nature 392, 796-798 (1998)]. 
     7. Spin on 4 microns of resist  151 , expose with Mask  2 , and develop. This mask defines the split fixed magnetic plate, for which the resist acts as an electroplating mold. This step is shown in  FIG. 7 . 
     8. Electroplate 3 microns of CoNiFe  152 . This step is shown in  FIG. 8 . 
     9. Strip the resist  151  and etch the exposed seed layer. This step is shown in  FIG. 9 . 
     10. Deposit 0.1 microns of silicon nitride (Si 3 N 4 ). 
     11. Etch the nitride layer using Mask  3 . This mask defines the contact vias from each end of the solenoid coil to the two halves of the split fixed magnetic plate. 
     12. Deposit a seed layer of copper. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     13. Spin on 5 microns of resist  153 , expose with Mask  4 , and develop. This mask defines the solenoid spiral coil and the spring posts, for which the resist acts as an electroplating mold. This step is shown in  FIG. 10 . 
     14. Electroplate 4 microns of copper  154 . 
     15. Strip the resist  153  and etch the exposed copper seed layer. This step is shown in  FIG. 11 . 
     16. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     17. Deposit 0.1 microns of silicon nitride. 
     18. Deposit 1 micron of sacrificial material  156 . This layer  156  determines the magnetic gap. 
     19. Etch the sacrificial material  156  using Mask  5 . This mask defines the spring posts. This step is shown in  FIG. 12 . 
     20. Deposit a seed layer of CoNiFe. 
     21. Spin on 4.5 microns of resist  157 , expose with Mask  6 , and develop. This mask defines the walls of the magnetic plunger, plus the spring posts. The resist forms an electroplating mold for these parts. This step is shown in  FIG. 13 . 
     22. Electroplate 4 microns of CoNiFe  158 . This step is shown in  FIG. 14 . 
     23. Deposit a seed layer of CoNiFe. 
     24. Spin on 4 microns of resist  159 , expose with Mask  7 , and develop. This mask defines the roof of the magnetic plunger, the springs, and the spring posts. The resist forms an electroplating mold for these parts. This step is shown in  FIG. 15 . 
     25. Electroplate 3 microns of CoNiFe  160 . This step is shown in  FIG. 16 . 
     26. Mount the wafer on a glass blank  161  and back-etch the wafer using KOH, with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer  150 . This step is shown in  FIG. 17 . 
     27. Plasma back-etch the boron doped silicon layer  150  to a depth of (approx.) 1 micron using Mask  8 . This mask defines the nozzle rim  162 . This step is shown in  FIG. 18 . 
     28. Plasma back-etch through the boron doped layer using Mask  9 . This mask defines the nozzle, and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in  FIG. 19 . 
     29. Detach the chips from the glass blank. Strip all adhesive, resist, sacrificial, and exposed seed layers. This step is shown in  FIG. 20 . 
     30. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     31. Connect the print heads to their interconnect systems. 
     32. Hydrophobize the front surface of the printheads. 
     33. Fill the completed print heads with ink  163  and test them. A filled nozzle is shown in  FIG. 21 . 
     IJ02 
     In a preferred embodiment, an ink jet print head is made up of a plurality of nozzle chambers each having an ink ejection port. Ink is ejected from the ink ejection port through the utilization of attraction between two parallel plates. 
     Turning initially to  FIG. 22 , there is illustrated a cross-sectional view of a single nozzle arrangement  210  as constructed in accordance with a preferred embodiment. The nozzle arrangement  210  includes a nozzle chamber  211  in which is stored ink to be ejected out of an ink ejection port  212 . The nozzle arrangement  210  can be constructed on the top of a silicon wafer utilizing micro electromechanical systems construction techniques as will become more apparent hereinafter. The top of the nozzle plate also includes a series of regular spaced etchant holes, e.g.  213  which are provided for efficient sacrificial etching of lower layers of the nozzle arrangement  210  during construction. The size of the etchant holes  213  is small enough that surface tension characteristics inhibit ejection from the holes  213  during operation. 
     Ink is supplied to the nozzle chamber  211  via an ink supply channel, e.g.  215 . 
     Turning now to  FIG. 23 , there is illustrated a cross-sectional view of one side of the nozzle arrangement  210 . A nozzle arrangement  210  is constructed on a silicon wafer base  217  on top of which is first constructed a standard CMOS two level metal layer  218  which includes the required drive and control circuitry for each nozzle arrangement. The layer  218 , which includes two levels of aluminum, includes one level of aluminum  219  being utilized as a bottom electrode plate. Other portions  220  of this layer can comprise nitride passivation. On top of the layer  219  there is provided a thin polytetrafluoroethylene (PTFE) layer  221 . 
     Next, an air gap  227  is provided between the top and bottom layers. This is followed by a further PTFE layer  228  which forms part of the top plate  222 . The two PTFE layers  221 ,  228  are provided so as to reduce possible stiction effects between the upper and lower plates. Next, a top aluminum electrode layer  230  is provided followed by a nitride layer (not shown) which provides structural integrity to the top electro plate. The layers  228  -  230  are fabricated so as to include a corrugated portion  223  which concertinas upon movement of the top plate  222 . 
     By placing a potential difference across the two aluminum layers  219  and  230 , the top plate  222  is attracted to bottom aluminum layer  219  thereby resulting in a movement of the top plate  222  towards the bottom plate  219 . This results in energy being stored in the concertinaed spring arrangement  223  in addition to air passing out of the side air holes, e.g.  233  and the ink being sucked into the nozzle chamber as a result of the distortion of the meniscus over the ink ejection port  212  ( FIG. 22 ). Subsequently, the potential across the plates is eliminated thereby causing the concertinaed spring portion  223  to rapidly return the plate  222  to its rest position. The rapid movement of the plate  222  causes the consequential ejection of ink from the nozzle chamber via the ink ejection port  212  ( FIG. 22 ). Additionally, air flows in via air gap  233  underneath the plate  222 . 
     The ink jet nozzles of a preferred embodiment can be formed from utilization of semi-conductor fabrication and MEMS techniques. Turning to  FIG. 24 , there is illustrated an exploded perspective view of the various layers in the final construction of a nozzle arrangement  210 . At the lowest layer is the silicon wafer  217  upon which all other processing steps take place. On top of the silicon layer  217  is the CMOS circuitry layer  218  which primarily comprises glass. On top of this layer is a nitride passivation layer  220  which is primarily utilized to passivate and protect the lower glass layer from any sacrificial process that may be utilized in the building up of subsequent layers. Next there is provided the aluminum layer  219  which, in the alternative, can form part of the lower CMOS glass layer  218 . This layer  219  forms the bottom plate. Next, two PTFE layers  226 ,  228  are provided between which is laid down a sacrificial layer, such as glass, which is subsequently etched away so as to release the plate  222  ( FIG. 23 ). On top of the PTFE layer  228  is laid down the aluminum layer  230  and a subsequent thicker nitride layer (not shown) which provides structural support to the top electrode stopping it from sagging or deforming. After this comes the top nitride nozzle chamber layer  235  which forms the rest of the nozzle chamber and ink supply channel. The layer  235  can be formed from the depositing and etching of a sacrificial layer and then depositing the nitride layer, etching the nozzle and etchant holes utilizing an appropriate mask before etching away the sacrificial material. 
     Obviously, print heads can be formed from large arrays of nozzle arrangements  210  on a single wafer which is subsequently diced into separate print heads. Ink supply can be either from the side of the wafer or through the wafer utilizing deep anisotropic etching systems such as high density low pressure plasma etching systems available from surface technology systems. Further, the corrugated portion  223  can be formed through the utilisation of a half tone mask process. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  240 , complete a 0.5 micron, one poly, 2 metal CMOS process  242 . This step is shown in  FIG. 26 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 25  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch the passivation layers  246  to expose the bottom electrode  244 , formed of second level metal. This etch is performed using Mask  1 . This step is shown in  FIG. 27 . 
     3. Deposit 50 nm of PTFE or other highly hydrophobic material. 
     4. Deposit 0.5 microns of sacrificial material, e.g. polyimide  248 . 
     5. Deposit 0.5 microns of (sacrificial) photosensitive polyimide. 
     6. Expose and develop the photosensitive polyimide using Mask  2 . This mask is a gray-scale mask which defines the concertina edge  250  of the upper electrode. The result of the etch is a series of triangular ridges at the circumference of the electrode. This concertina edge is used to convert tensile stress into bend strain, and thereby allow the upper electrode to move when a voltage is applied across the electrodes. This step is shown in  FIG. 28 . 
     7. Etch the polyimide and passivation layers using Mask  3 , which exposes the contacts for the upper electrode which are formed in second level metal. 
     8. Deposit 0.1 microns of tantalum  252 , forming the upper electrode. 
     9. Deposit 0.5 microns of silicon nitride (Si 3 N 4 ), which forms the movable membrane of the upper electrode. 
     10. Etch the nitride and tantalum using Mask  4 . This mask defines the upper electrode, as well as the contacts to the upper electrode. This step is shown in  FIG. 29 . 
     11. Deposit 12 microns of (sacrificial) photosensitive polyimide  254 . 
     12. Expose and develop the photosensitive polyimide using Mask  5 . A proximity aligner can be used to obtain a large depth of focus, as the line-width for this step is greater than 2 microns, and can be 5 microns or more. This mask defines the nozzle chamber walls. This step is shown in  FIG. 30 . 
     13. Deposit 3 microns of PECVD glass  256 . This step is shown in  FIG. 31 . 
     14. Etch to a depth of  1  micron using Mask  6 . This mask defines the nozzle rim  258 . This step is shown in  FIG. 32 . 
     15. Etch down to the sacrificial layer  254  using Mask  7 . This mask defines the roof of the nozzle chamber, and the nozzle  260  itself. This step is shown in  FIG. 33 . 
     16. Back-etch completely through the silicon wafer  246  (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  8 . This mask defines the ink inlets  262  which are etched through the wafer  240 . The wafer  240  is also diced by this etch. 
     17. Back-etch through the CMOS oxide layer through the holes in the wafer  240 . This step is shown in  FIG. 34 . 
     18. Etch the sacrificial polyimide  254 . The nozzle chambers  264  are cleared, a gap is formed between the electrodes and the chips are separated by this etch. To avoid stiction, a final rinse using supercooled carbon dioxide can be used. This step is shown in  FIG. 35 . 
     19. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     20. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     21. Hydrophobize the front surface of the print heads. 
     22. Fill the completed print heads with ink  266  and test them. A filled nozzle is shown in  FIG. 36 . 
     IJ03 
     In a preferred embodiment, there is provided an ink jet printer having nozzle chambers. Each nozzle chamber includes a thermoelastic bend actuator that utilizes a planar resistive material in the construction of the bend actuator. The bend actuator is activated when it is required to eject ink from a chamber. 
     Turning now to  FIG. 37 , there is illustrated a cross-sectional view, partly in section of a nozzle arrangement  310  as constructed in accordance with a preferred embodiment. The nozzle arrangement  310  can be formed as part of an array of nozzles fabricated on a semi-conductor wafer utilizing techniques known in the production of micro-electromechanical systems (MEMS). The nozzle arrangement  310  includes a boron doped silicon wafer layer  312  which can be constructed by a back etching a silicon wafer  318  which has a buried boron doped epitaxial layer. The boron doped layer can be further etched so as to define a nozzle hole  313  and rim  314 . 
     The nozzle arrangement  310  includes a nozzle chamber  316  which can be constructed by utilization of an anisotropic crystallographic etch of the silicon portions  318  of the wafer. 
     On top of the silicon portions  318  is included a glass layer  320  which can comprise CMOS drive circuitry including a two level metal layer (not shown) so as to provide control and drive circuitry for the thermal actuator. On top of the CMOS glass layer  320  is provided a nitride layer  321  which includes side portions  322  which act to passivate lower layers from etching that is utilized in construction of the nozzle arrangement  310 . The nozzle arrangement  310  includes a paddle actuator  324  which is constructed on a nitride base  325  which acts to form a rigid paddle for the overall actuator  324 . Next, an aluminum layer  327  is provided with the aluminum layer  327  being interconnected by vias  328  with the lower CMOS circuitry so as to form a first portion of a circuit. The aluminum layer  327  is interconnected at a point  330  to an Indium Tin Oxide (ITO) layer  329  which provides for resistive heating on demand. The ITO layer  329  includes a number of etch holes  331  for allowing the etching away of a lower level sacrificial layer which is formed between the layers  327 ,  329 . The ITO layer is further connected to the lower glass CMOS circuitry layer by via  332 . On top of the ITO layer  329  is optionally provided a polytetrafluoroethylene layer (not shown) which provides for insulation and further rapid expansion of the top layer  329  upon heating as a result of passing a current through the bottom layer  327  and ITO layer  329 . 
     The back surface of the nozzle arrangement  310  is placed in an ink reservoir so as to allow ink to flow into nozzle chamber  316 . When it is desired to eject a drop of ink, a current is passed through the aluminum layer  327  and ITO layer  329 . The aluminum layer  327  provides a very low resistance path to the current whereas the ITO layer  329  provides a high resistance path to the current. Each of the layers  327 ,  329  are passivated by means of coating by a thin nitride layer (not shown) so as to insulate and passivate the layers from the surrounding ink. Upon heating of the ITO layer  329  and optionally PTFE layer, the top of the actuator  324  expands more rapidly than the bottom portions of the actuator  324 . This results in a rapid bending of the actuator  324 , particularly around the point  335  due to the utilization of the rigid nitride paddle arrangement  325 . This accentuates the downward movement of the actuator  324  which results in the ejection of ink from ink ejection nozzle  313 . 
     Between the two layers  327 ,  329  is provided a gap  360  which can be constructed via utilization of etching of sacrificial layers so as to dissolve away sacrificial material between the two layers. Hence, in operation ink is allowed to enter this area and thereby provides a further cooling of the lower surface of the actuator  324  so as to assist in accentuating the bending. Upon de-activation of the actuator  324 , it returns to its quiescent position above the nozzle chamber  316 . The nozzle chamber  316  refills due to the surface tension of the ink through the gaps between the actuator  324  and the nozzle chamber  316 . 
     The PTFE layer has a high coefficient of thermal expansion and therefore further assists in accentuating any bending of the actuator  324 . Therefore, in order to eject ink from the nozzle chamber  316 , a current is passed through the planar layers  327 ,  329  resulting in resistive heating of the top layer  329  which further results in a general bending down of the actuator  324  resulting in the ejection of ink. 
     The nozzle arrangement  310  is mounted on a second silicon chip wafer which defines an ink reservoir channel to the back of the nozzle arrangement  310  for resupply of ink. 
     Turning now to  FIG. 38 , there is illustrated an exploded perspective view illustrating the various layers of a nozzle arrangement  310 . The arrangement  310  can, as noted previously, be constructed from back etching to the boron doped layer. The actuator  324  can further be constructed through the utilization of a sacrificial layer filling the nozzle chamber  316  and the depositing of the various layers  325 ,  327 ,  329  and optional PTFE layer before sacrificially etching the nozzle chamber  316  in addition to the sacrificial material in area  360  (See  FIG. 37 ). To this end, the nitride layer  321  includes side portions  322  which act to passivate the portions of the lower glass layer  320  which would otherwise be attacked as a result of sacrificial etching. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer deposit 3 microns of epitaxial silicon heavily doped with boron  312 . 
     2. Deposit 10 microns of epitaxial silicon  318 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete a 0.5 micron, one poly, 2 metal CMOS process  320 . This step is shown in  FIG. 40 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 39  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers down to silicon  318  or second level metal using Mask  1 . This mask defines the nozzle cavity and the bend actuator electrode contact vias  328 ,  332 . This step is shown in  FIG. 41 . 
     5. Crystallographically etch the exposed silicon  318  using KOH as shown at  340 . This etch stops on &lt;111&gt; crystallographic planes  361 , and on the boron doped silicon buried layer  312 . This step is shown in  FIG. 42 . 
     6. Deposit 0.5 microns of low stress PECVD silicon nitride  341  (Si 3 N 4 ). The nitride  341  acts as an ion diffusion barrier. This step is shown in  FIG. 43 . 
     7. Deposit a thick sacrificial layer  342  (e.g. low stress glass), filling the nozzle cavity. Planarize the sacrificial layer  342  down to the nitride  341  surface. This step is shown in  FIG. 44 . 
     8. Deposit 1 micron of tantalum  343 . This layer acts as a stiffener for the bend actuator. 
     9. Etch the tantalum  343  using Mask  2 . This step is shown in  FIG. 45 . This mask defines the space around the stiffener section of the bend actuator, and the electrode contact vias. 
     10. Etch nitride  341  still using Mask  2 . This clears the nitride from the electrode contact vias  328 ,  332 . This step is shown in  FIG. 46 . 
     11. Deposit one micron of gold  344 , patterned using Mask  3 . This may be deposited in a lift-off process. Gold is used for its corrosion resistance and low Young&#39;s modulus. This mask defines the lower conductor of the bend actuator. This step is shown in  FIG. 47 . 
     12. Deposit 1 micron of thermal blanket  345 . This material should be a non-conductive material with a very low Young&#39;s modulus and a low thermal conductivity, such as an elastomer or foamed polymer. 
     13. Pattern the thermal blanket  345  using Mask  4 . This mask defines the contacts between the upper and lower conductors, and the upper conductor and the drive circuitry. This step is shown in  FIG. 48 . 
     14. Deposit 1 micron of a material  346  with a very high resistivity (but still conductive), a high Young&#39;s modulus, a low heat capacity, and a high coefficient of thermal expansion. A material such as indium tin oxide (ITO) may be used, depending upon the dimensions of the bend actuator. 
     15. Pattern the ITO  346  using Mask  5 . This mask defines the upper conductor of the bend actuator. This step is shown in  FIG. 49 . 
     16. Deposit a further 1 micron of thermal blanket  347 . 
     17. Pattern the thermal blanket  347  using Mask  6 . This mask defines the bend actuator, and allows ink to flow around the actuator into the nozzle cavity. This step is shown in  FIG. 50 . 
     18. Mount the wafer on a glass blank  348  and back-etch the wafer using KOH, with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer  312 . This step is shown in  FIG. 51 . 
     19. Plasma back-etch the boron doped silicon layer  312  to a depth of  1  micron using Mask  7 . This mask defines the nozzle rim  314 . This step is shown in  FIG. 52 . 
     20. Plasma back-etch through the boron doped layer  312  using Mask  8 . This mask defines the nozzle  313 , and the edge of the chips. 
     21. Plasma back-etch nitride  341  up to the glass sacrificial layer  342  through the holes in the boron doped silicon layer  312 . At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in  FIG. 53 . 
     22. Strip the adhesive layer to detach the chips from the glass blank  348 . 
     23. Etch the sacrificial glass layer  342  in buffered HF. This step is shown in  FIG. 54 . 
     24. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     25. Connect the printheads to their interconnect systems. 
     26. Hydrophobize the front surface of the printheads. 
     27. Fill the completed printheads with ink  350  and test them. A filled nozzle is shown in  FIG. 55 . 
     IJ04 
     In a preferred embodiment, a stacked capacitive actuator is provided which has alternative electrode layers sandwiched between a compressible polymer. Hence, on activation of the stacked capacitor the plates are drawn together compressing the polymer thereby storing energy in the compressed polymer. The capacitor is then de-activated or drained with the result that the compressed polymer acts to return the actuator to its original position and thereby causes the ejection of ink from an ink ejection port. 
     Turning now to  FIG. 56 , there is illustrated a single nozzle arrangement  410  as constructed in accordance with a preferred embodiment. The nozzle arrangement  410  includes an ink ejection portal  411  for the ejection of ink on demand. The ink is ejected from a nozzle chamber  412  by means of a stacked capacitor-type device  413 . In a first design, the stacked capacitor device  413  consists of capacitive plates sandwiched between a compressible polymer. Upon charging of the capacitive plates, the polymer is compressed thereby resulting in a general “accordion” or “concertinaing” of the actuator  413  so that its top surface moves away from the ink ejection portal  411 . The compression of the polymer sandwich stores energy in the compressed polymer. The capacitors are subsequently rapidly discharged resulting in the energy in the compressed polymer being released upon the polymer&#39;s return to quiescent position. The return of the actuator to its quiescent position results in the ejection of ink from the nozzle chamber  412 . The process is illustrated schematically in  FIGS. 57-60  with  FIG. 57  illustrating the nozzle chamber  412  in its quiescent or idle state, having an ink meniscus  414  around the nozzle ejection portal  411 . Subsequently, the electrostatic actuator  413  is activated resulting in its contraction as indicated in  FIG. 58 . The contraction results in the meniscus  414  changing shape as indicated with the resulting surface tension effects resulting in the drawing in of ink around the meniscus and consequently ink  416  flows into nozzle chamber  412 . 
     After sufficient time, the meniscus  414  returns to its quiescent position with the capacitor  413  being loaded ready for firing ( FIG. 59 ). The capacitor plates  413  are then rapidly discharged resulting, as illustrated in  FIG. 60 , in the rapid return of the actuator  413  to its original position. The rapid return imparts a momentum to the ink within the nozzle chamber  412  so as to cause the expansion of the ink meniscus  414  and the subsequent ejection of ink from the nozzle chamber  412 . 
     Turning now to  FIG. 61 , there is illustrated a perspective view of a portion of the actuator  413  exploded in part. The actuator  413  consists of a series of interleaved plates  420 ,  421  between which is sandwiched a compressive material  422 , for example styrene-ethylene-butylene-styrene block copolymer. One group of electrodes, e.g.  420 ,  423 ,  425  jut out at one side of the stacked capacitor layout A second series of electrodes, e.g.  421 ,  424  jut out a second side of the capacitive actuator. The electrodes are connected at one side to a first conductive material  427  and the other series of electrodes, e.g.  421 ,  424  are connected to second conductive material  428  ( FIG. 56 ). The two conductive materials  427 ,  428  are electrically isolated from one another and are in turn interconnected to lower signal and drive layers as will become more readily apparent hereinafter. 
     In alternative designs, the stacked capacitor device  413  consists of other thin film materials in place of the styrene-ethylene-butylene-styrene block copolymer. Such materials may include: 
     1) Piezoelectric materials such as PZT 
     2) Electrostrictive materials such as PLZT 
     3) Materials, that can be electrically switched between a ferro-electric and an anti-ferro-electric phase such as PLZSnT. 
     Importantly, the electrode actuator  413  can be rapidly constructed utilizing chemical vapor deposition (CVD) techniques. The various layers,  420 ,  421 ,  422  can be laid down on a planar wafer one after another covering the whole surface of the wafer. A stack can be built up rapidly utilizing CVD techniques. The two sets of electrodes are preferably deposited utilizing separate metals. For example, aluminum and tantalum could be utilized as materials for the metal layers. The utilization of different metal layers allows for selective etching utilizing a mask layer so as to form the structure as indicated in  FIG. 61 . For example, the CVD sandwich can be first laid down and then a series of selective etchings utilizing appropriate masks can be utilized to produce the overall stacked capacitor structure. The utilization of the CVD process substantially enhances the efficiency of production of the stacked capacitor devices. Construction of the Ink Nozzle Arrangement 
     Turning now to  FIG. 62  there is shown an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment The ink jet nozzle arrangement  410  is constructed on a standard silicon wafer  430  on top of which is constructed data drive circuitry which can be constructed in the usual manner such as a two-level metal CMOS layer  431 . On top of the CMOS layer  431  is constructed a nitride passivation layer  432  which provides passivation protection for the lower layers during operation and also should an etchant be utilized which would normally dissolve the lower layers. The various layers of the stacked device  413 , for example  420 ,  421 ,  422 , can be laid down utilizing CVD techniques. The stacked device  413  is constructed utilizing the, aforementioned production steps including utilizing appropriate masks for selective etchings to produce the overall stacked capacitor structure. Further, interconnection can be provided between the electrodes  427 ,  428  and the circuitry in the CMOS layer  431 . Finally, a nitride layer  433  is provided so as to form the walls of the nozzle chamber, e.g.  434 , and posts, e.g.  435 , in one open wall  436  of the nozzle chamber. The surface layer  437  of the layer  433  can be deposited onto a sacrificial material. The sacrificial material is subsequently etched so as to form the nozzle chamber  412  ( FIG. 56 ). To this end, the top layer  437  includes etchant holes, e.g.  438 , so as to speed up the etching process in addition to the ink ejection portal  411 . The diameter of the etchant holes, e.g.  438 , is significantly smaller than that of the ink ejection portal  411 . If required an additional nitride layer may be provided on top of the layer  420  to protect the stacked device  413  during the etching of the sacrificial material to form the nozzle chamber  412  ( FIG. 56 ) and during operation of the ink jet nozzle. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  430 , complete a 0.5 micron, one poly, 2 metal CMOS layer  431  process. This step is shown in  FIG. 64 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 63  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch the CMOS oxide layers  431  to second level metal using Mask  1 . This mask defines the contact vias from the electrostatic stack to the drive circuitry. 
     3. Deposit 0.1 microns of aluminum. 
     4. Deposit 0.1 microns of elastomer. 
     5. Deposit 0.1 microns of tantalum. 
     6. Deposit 0.1 microns of elastomer. 
     7. Repeat steps 2 to 5 twenty times to create a stack  440  of alternating metal and elastomer which is 8 microns high, with 40 metal layers and 40 elastomer layers. This step is shown in  FIG. 65 . 
     8. Etch the stack  440  using Mask  2 . This leaves a separate rectangular multi-layer stack  413  for each nozzle. This step is shown in  FIG. 66 . 
     9. Spin on resist  441 , expose with Mask  3 , and develop. This mask defines one side of the stack  413 . This step is shown in  FIG. 67 . 
     10. Etch the exposed elastomer layers to a horizontal depth of 1 micron. 
     11. Wet etch the exposed aluminum layers to a horizontal depth of 3 microns. 
     12. Foam the exposed elastomer layers by 50 nm to close the 0.1 micron gap left by the etched aluminum. 
     13. Strip the resist  441 . This step is shown in  FIG. 68 . 
     14. Spin on resist  442 , expose with Mask  4 , and develop. This mask defines the opposite side of the stack  413 . This step is shown in  FIG. 69 . 
     15. Etch the exposed elastomer layers to a horizontal depth of 1 micron. 
     16. Wet etch the exposed tantalum layers to a horizontal depth of 3 microns. 
     17. Foam the exposed elastomer layers by 50 nm to close the 0.1 micron gap left by the etched aluminum. 
     18. Strip the resist  442 . This step is shown in  FIG. 70 . 
     19. Deposit 1.5 microns of tantalum  443 . This metal contacts all of the aluminum layers on one side of the stack  413 , and all of the tantalum layers on the other side of the stack  413 . 
     20. Etch the tantalum  443  using Mask  5 . This mask defines the electrodes at both edges of the stack  413 . This step is shown in  FIG. 71 . 
     21. Deposit  18  microns of sacrificial material  444  (e.g. photosensitive polyimide). 
     22. Expose and develop the sacrificial layer  444  using Mask  6  using a proximity aligner. This mask defines the nozzle chamber walls  434  and inlet filter. This step is shown in  FIG. 72 . 
     23. Deposit 3 microns of PECVD glass  445 . 
     24. Etch to a depth of 1 micron using Mask  7 . This mask defines the nozzle rim  450 . This step is shown in  FIG. 73 . 
     25. Etch down to the sacrificial layer  444  using Mask  8 . This mask defines the roof  437  of the nozzle chamber, and the nozzle  411  itself. This step is shown in  FIG. 74 . 
     26. Back-etch completely through the silicon wafer  430  (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  9 . This mask defines the ink inlets  447  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 75 . 
     27. Back-etch through the CMOS oxide layer  431  through the holes in the wafer. 
     28. Etch the sacrificial material  444 . The nozzle chambers  412  are cleared, and the chips are separated by this etch. This step is shown in  FIG. 76 . 
     29. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     30. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     31. Hydrophobize the front surface of the printheads. 
     32. Fill the completed printheads with ink  448  and test them. A filled nozzle is shown in  FIG. 77 . 
     IJ05 
     A preferred embodiment of the present invention relies upon a magnetic actuator to “load” a spring, such that, upon deactivation of the magnetic actuator the resultant movement of the spring causes ejection of a drop of ink as the spring returns to its original position. 
     Turning to  FIG. 78 , there is illustrated an exploded perspective view of an ink nozzle arrangement  501  constructed in accordance with a preferred embodiment It would be understood that a preferred embodiment can be constructed as an array of nozzle arrangements  501  so as to together form a line for printing. 
     The operation of the ink nozzle arrangement  501  of  FIG. 78  proceeds by a solenoid  502  being energized by way of a driving circuit  503  when it is desired to print out a ink drop. The energized solenoid  502  induces a magnetic field in a fixed soft magnetic pole  504  and a moveable soft magnetic pole  505 . The solenoid power is turned on to a maximum current for long enough to move the moveable pole  505  from its rest position to a stopped position close to the fixed magnetic pole  504 . The ink nozzle arrangement  501  of  FIG. 78  sits within an ink chamber filled with ink. Therefore, holes  506  are provided in the moveable soft magnetic pole  505  for “squirting” out of ink from around the coil  502  when the pole  505  undergoes movement. 
     The moveable soft magnetic pole is balanced by a fulcrum  508  with a piston head  509 . Movement of the magnetic pole  505  closer to the stationary pole  504  causes the piston head  509  to move away from a nozzle chamber  511  drawing air into the chamber  511  via an ink ejection port  513 . The piston  509  is then held open above the nozzle chamber  511  by means of maintaining a low “keeper” current through solenoid  502 . The keeper level current through solenoid  502  being sufficient to maintain the moveable pole  505  against the fixed soft magnetic pole  504 . The level of current will be substantially less than the maximum current level because the gap between the two poles  504  and  505  is at a minimum. For example, a keeper level current of 10% of the maximum current level may be suitable. During this phase of operation, the meniscus of ink at the nozzle tip or ink ejection port  513  is a concave hemisphere due to the in flow of air. The surface tension on the meniscus exerts a net force on the ink which results in ink flow from the ink chamber into the nozzle chamber  511 . This results in the nozzle chamber refilling, replacing the volume taken up by the piston head  509  which has been withdrawn. This process takes approximately 100 microseconds. 
     The current within solenoid  502  is then reversed to half that of the maximum current The reversal demagnetises the magnetic poles and initiates a return of the piston  509  to its rest position. The piston  509  is moved to its normal rest position by both the magnetic repulsion and by the energy stored in a stressed tortional spring  516 ,  519  which was put in a state of torsion upon the movement of moveable pole  505 . 
     The forces applied to the piston  509  as a result of the reverse current and spring  516 ,  519  will be greatest at the beginning of the movement of the piston  509  and will decrease as the spring elastic stress falls to zero. As a result, the acceleration of piston  509  is high at the beginning of a reverse stroke and the resultant ink velocity within the chamber  511  becomes uniform during the stroke. This results in an increased operating tolerance before ink flow over the printhead surface will occur. 
     At a predetermined time during the return stroke, the solenoid reverse current is turned off. The current is turned off when the residual magnetism of the movable pole is at a minimum. The piston  509  continues to move towards its original rest position. 
     The piston  509  will overshoot the quiescent or rest position due to its inertia. Overshoot in the piston movement achieves two things: greater ejected drop volume and velocity, and improved drop break off as the piston returns from overshoot to its quiescent position. 
     The piston  509  will eventually return from overshoot to the quiescent position. This return is caused by the springs  516 ,  519  which are now stressed in the opposite direction. The piston return “sucks” some-of the ink back into the nozzle chamber  511 , causing the ink ligament connecting the ink drop to the ink in the nozzle chamber  511  to thin. The forward velocity of the drop and the backward velocity of the ink in the nozzle chamber  511  are resolved by the ink drop breaking off from the ink in the nozzle chamber  511 . 
     The piston  509  stays in the quiescent position until the next drop ejection cycle. 
     A liquid ink printhead has one ink nozzle arrangement  501  associated with each of the multitude of nozzles. The arrangement  501  has the following major parts: 
     (1) Drive circuitry  503  for driving the solenoid  502 . 
     (2) An ejection port  513 . The radius of the ejection port  513  is an important determinant of drop velocity and drop size. 
     (3) A piston  509 . This is a cylinder which moves through the nozzle chamber  511  to expel the ink. The piston  509  is connected to one end of the lever arm  517 . The piston radius is approximately 1.5 to 2 times the radius of the ejection port  513 . The ink drop volume output is mostly determined by the volume of ink displaced by the piston  509  during the piston return stroke. 
     (4) A nozzle chamber  511 . The nozzle chamber  511  is slightly wider than the piston  509 . The gap between the piston  509  and the nozzle chamber walls is as small as is required to ensure that the piston does not contact the nozzle chamber during actuation or return. If the printheads are fabricated using 0.5 micron semiconductor lithography, then a 1 micron gap will usually be sufficient The nozzle chamber is also deep enough so that air ingested through the ejection port  513  when the plunger  509  returns to its quiescent state does not extend to the piston  509 . If it does, the ingested bubble may form a cylindrical surface instead of a hemispherical surface. If this happens, the nozzle will not refill properly. 
     (5) A solenoid  502 . This is a spiral coil of copper. Copper is used for its low resistivity, and high electro-migration resistance. 
     (6) A fixed magnetic pole of ferromagnetic material  504 . 
     (7) A moveable magnetic pole of ferromagnetic material  505 . To maximise the magnetic force generated, the moveable magnetic pole  505  and fixed magnetic pole  504  surround the solenoid  502  as a torus. Thus little magnetic flux is lost, and the flux is concentrated across the gap between the moveable magnetic pole  505  and the fixed pole  504 . The moveable magnetic pole  505  has holes in the surface  506  ( FIG. 78 ) above the solenoid to allow trapped ink to escape. These holes are arranged and shaped so as to minimise their effect on the magnetic force generated between the moveable magnetic pole  505  and the fixed magnetic pole  504 . 
     (8) A magnetic gap. The gap between the fixed plate  504  and the moveable magnetic pole  505  is one of the most important “parts” of the print actuator. The size of the gap strongly affects the magnetic force generated, and also limits the travel of the moveable magnetic pole  505 . A small gap is desirable to achieve a strong magnetic force. The travel of the piston  509  is related to the travel of the moveable magnetic pole  505  (and therefore the gap) by the lever arm  517 . 
     (9) Length of the lever arm  517 . The lever arm  517  allows the travel of the piston  509  and the moveable magnetic pole  505  to be independently optimised. At the short end of the lever arm  517  is the moveable magnetic pole  505 . At the long end of the lever arm  517  is the piston  509 . The spring  516  is at the fulcrum  508 . optimum travel for the moveable magnetic pole  505  is less than 1 micron, so as to minimise the magnetic gap. The optimum travel for the piston  509  is approximately 5 micron for a 1200 dpi printer. The difference in optimum travel is resolved by a lever  517  with a 5:1 or greater ratio in arm length. 
     (10) Springs  516 ,  519  ( FIG. 78 ). The springs e.g.  516  return the piston to its quiescent position after a deactivation of the actuator. The springs  516  are at the fulcrum  508  of the lever arm. 
     (11) Passivation layers (not shown). All surfaces are preferably coated with passivation layers, which may be silicon nitride (Si 3 N 4 ), diamond like carbon (DLC), or other chemically inert, highly impermeable layer. The passivation layers are especially important for device lifetime, as the active device is immersed in the ink. As will be evident from the foregoing description there is an advantage in ejecting the drop on deactivation of the solenoid  502 . This advantage comes from the rate of acceleration of the moving magnetic pole  505  which is used as a piston or plunger. 
     The force produced by a moveable magnetic pole by an electromagnetic induced field is approximately proportional to the inverse square of the gap between the moveable  505  and static magnetic poles  504 . When the solenoid  502  is off, this gap is at a maximum. When the solenoid  502  is turned on, the moving pole  505  is attracted to the static pole  504 . As the gap decreases, the force increases, accelerating the movable pole  505  faster. The velocity increases in a highly non-linear fashion, approximately with the square of time. During the reverse movement of the moving pole  505  upon deactivation the acceleration of the moving pole  505  is greatest at the beginning and then slows as the spring elastic stress falls to zero. As a result, the velocity of the moving pole  505  is more uniform during the reverse stroke movement. 
     (1) The velocity of piston or plunger  509  is much more constant over the duration of the drop ejection stroke. 
     (2) The piston or plunger  509  can readily be entirely removed from the ink chamber during the ink fill stage, and thereby the nozzle filling time can be reduced, allowing faster printhead operation. 
     However, this approach does have some disadvantages over a direct firing type of actuator: 
     (1) The stresses on the spring  516  are relatively large. Careful design is required to ensure that the springs operate at below the yield strength of the materials used. 
     (2) The solenoid  502  must be provided with a “keeper” current for the nozzle fill duration. The keeper current will typically be less than  10 % of the solenoid actuation current. However, the nozzle fill duration is typically around 50 times the drop firing duration, so the keeper energy will typically exceed the solenoid actuation energy. 
     (3) The operation of the actuator is more complex due to the requirement for a “keeper” phase. 
     The printhead is fabricated from two silicon wafers. A first wafer is used to fabricate the print nozzles (the printhead wafer) and a second wafer (the Ink Channel Wafer) is utilized to fabricate the various ink channels in addition to providing a support means for the first channel. The fabrication process then proceeds as follows: 
     (1) Start with a single crystal silicon wafer  520 , which has a buried epitaxial layer  522  of silicon which is heavily doped with boron. The boron should be doped to preferably 10 20  atoms per cm 3  of boron or more, and be approximately 3 micron thick, and be doped in a manner suitable for the active semiconductor device technology chosen. The wafer diameter of the printhead wafer should be the same as the ink channel wafer. 
     (2) Fabricate the drive transistors and data distribution circuitry  503  according to the process chosen (eg. CMOS). 
     (3) Planarise the wafer  520  using chemical Mechanical Planarisation (CMP). 
     (4) Deposit 5 micron of glass (SiO 2 ) over the second level metal. 
     (5) Using a dual damascene process, etch two levels into the top oxide layer. Level  1  is 4 micron deep, and level  2  is 5 micron deep. Level  2  contacts the second level metal. The masks for the static magnetic pole are used. 
     (6) Deposit 5 micron of nickel iron alloy (NiFe). 
     (7) Planarise the wafer using CMP, until the level of the SiO 2  is reached forming the magnetic pole  504 . 
     (8) Deposit 0.1 micron of silicon nitride (Si 3 N 4 ). 
     (9) Etch the Si 3 N 4  for via holes for the connections to the solenoids, and for the nozzle chamber region  511 . 
     (10) Deposit 4 micron of SiO 2 . 
     (11) Plasma etch the SiO 2  in using the solenoid and support post mask. 
     (12) Deposit a thin diffusion barrier, such as Ti, TiN, or TiW, and an adhesion layer if the diffusion layer chosen has insufficient adhesion. 
     (13) Deposit 4 micron of copper for forming the solenoid  502  and spring posts  524 . The deposition may be by sputtering, CVD, or electroless plating. As well as lower resistivity than aluminum, copper has significantly higher resistance to electro-migration. The electro-migration resistance is significant, as current densities in the order of 3×10 6  Amps/cm 2  may be required. Copper films deposited by low energy kinetic ion bias sputtering have been found to have 1,000 to 100,000 times larger electro-migration lifetimes larger than aluminum silicon alloy. The deposited copper should be alloyed and layered for maximum electro-migration lifetimes than aluminum silicon alloy. The deposited copper should be alloyed and layered for maximum electro-migration resistance, while maintaining high electrical conductivity. 
     (14) Planarise the wafer using CMP, until the level of the SiO 2  is reached. A damascene process is used for the copper layer due to the difficulty involved in etching copper. However, since the damascene dielectric layer is subsequently removed, processing is actually simpler if a standard deposit/etch cycle is used instead of damascene. However, it should be noted that the aspect ratio of the copper etch would be 8:1 for this design, compared to only 4:1 for a damascene oxide etch This difference occurs because the copper is 1 micron wide and 4 micron thick, but has only 0.5 micron spacing. Damascene processing also reduces the lithographic difficultly, as the resist is on oxide, not metal. 
     (15) Plasma etch the nozzle chamber  511 , stopping at the boron doped epitaxial silicon layer  521 . This etch will be through around 13 micron of SiO 2 , and 8 micron of silicon. The etch should be highly anisotropic, with near vertical sidewalls. The etch stop detection can be on boron in the exhaust gasses. If this etch is selective against NiFe, the masks for this step and the following step can be combined, and the following step can be eliminated. This step also etches the edge of the printhead wafer down to the boron layer, for later separation. 
     (16) Etch the SiO 2  layer. This need only be removed in the regions above the NiFe fixed magnetic poles, so it can be removed in the previous step if an Si and SiO 2  etch selective against NiFe is used 
     (17) Conformably deposit 0.5 micron of high density Si 3 N 4 . This forms a corrosion barrier, so should be free of pin-holes, and be impermeable to OH ions. 
     (18) Deposit a thick sacrificial layer  540 . This layer should entirely fill the nozzle chambers, and coat the entire wafer to an added thickness of 8 microns. The sacrificial layer may be SiO 2 . 
     (19) Etch two depths in the sacrificial layer for a dual damascene process. The deep etch is 8 microns, and the shallow etch is 3 microns. The masks defines the piston  509 , the lever arm  517 , the springs  516  and the moveable magnetic pole  505 . 
     (20) Conformably deposit 0.1 micron of high density Si 3 N 4 . This forms a corrosion barrier, so should be free of pin-holes, and be impermeable to OH ions. 
     (21) Deposit 8 micron of nickel iron alloy (NiFe). 
     (22) Planarise the wafer using CMP, until the level of the SiO 2  is reached. 
     (23) Deposit 0.1 micron of silicon nitride (Si 3 N 4 ). 
     (24) Etch the Si 3 N 4  everywhere except the top of the plungers. 
     (25) Open the bond pads. 
     (26) Permanently bond the wafer onto a pre-fabricated ink channel wafer. The active side of the printhead wafer faces the ink channel wafer. The ink channel wafer is attached to a backing plate, as it has already been etched into separate ink channel chips. 
     (27) Etch the printhead wafer to entirely remove the backside silicon to the level of the boron doped epitaxial layer  522 . This etch can be a batch wet etch in ethylenediamine pyrocatechol (EDP). 
     (28) Mask the nozzle rim  514  from the underside of the printhead wafer. This mask also includes the chip edges. 
     (31) Etch through the boron doped silicon layer  522 , thereby creating the nozzle holes. This etch should also etch fairly deeply into the sacrificial material in the nozzle chambers to reduce time required to remove the sacrificial layer. 
     (32) Completely etch the sacrificial material. If this material is SiO 2  then a HF etch can be used. The nitride coating on the various layers protects the other glass dielectric layers and other materials in the device from HF etching. Access of the HF to the sacrificial layer material is through the nozzle, and simultaneously through the ink channel chip. The effective depth of the etch is 21 microns. 
     (33) Separate the chips from the backing plate. Each chip is now a full printhead including ink channels. The two wafers have already been etched through, so the printheads do not need to be diced. 
     (34) Test the printheads and TAB bond the good printheads. 
     (35) Hydrophobize the front surface of the printheads. 
     (36) Perform final testing on the TAB bonded printheads. 
       FIG. 79  shows a perspective view, in part in section, of a single inkjet nozzle arrangement  501  constructed in accordance with a preferred embodiment. 
     One alternative form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer deposit 3 microns of epitaxial silicon heavily doped with boron. 
     2. Deposit 10 microns of epitaxial silicon, either p-type or n-type, depending upon the CMOS process used. 
     3. Complete a 0.5 micron, one poly, 2 metal CMOS process. This step is shown in  FIG. 81 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 80  is a key to representations of various materials in these manufacturing diagrams. 
     4. Etch the CMOS oxide layers down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber, the edges of the printheads chips, and the vias for the contacts from the aluminum electrodes to the two halves of the split fixed magnetic plate. 
     5. Plasma etch the silicon down to the boron doped buried layer, using oxide from step 4 as a mask. This etch does not substantially etch the aluminum. This step is shown in  FIG. 82 . 
     6. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosen due to a high saturation flux density of 2 Tesla, and a low coercivity. [Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturation magnetic flux density, Nature 392, 796-798 (1998)]. 
     7. Spin on 4 microns of resist, expose with Mask  2 , and develop. This mask defines the split fixed magnetic plate and the nozzle chamber wall, for which the resist acts as an electroplating mold. This step is shown in  FIG. 83 . 
     8. Electroplate 3 microns of CoNiFe. This step is shown in  FIG. 84 . 
     9. Strip the resist and etch the exposed seed layer. This step is shown in  FIG. 85 . 
     10. Deposit 0.1 microns of silicon nitride (Si 3 N 4 ). 
     11. Etch the nitride layer using Mask  3 . This mask defines the contact vias from each end of the solenoid coil to the two halves of the split fixed magnetic plate. 
     12. Deposit a seed layer of copper. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     13. Spin on 5 microns of resist, expose with Mask  4 , and develop. This mask defines the solenoid spiral coil, the nozzle chamber wall and the spring posts, for which the resist acts as an electroplating mold. This step is shown in  FIG. 86 . 
     14. Electroplate 4 microns of copper. 
     15. Strip the resist and etch the exposed copper seed layer. This step is shown in  FIG. 87 . 
     16. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     17. Deposit 0.1 microns of silicon nitride. 
     18. Deposit 1 micron of sacrificial material. This layer determines the magnetic gap. 
     19. Etch the sacrificial material using Mask  5 . This mask defines the spring posts and the nozzle chamber wall. This step is shown in  FIG. 88 . 
     20. Deposit a seed layer of CoNiFe. 
     21. Spin on 4.5 microns of resist, expose with Mask  6 , and develop. This mask defines the walls of the magnetic plunger, the lever arm, the nozzle chamber wall and the spring posts. The resist forms an electroplating mold for these parts. This step is shown in  FIG. 89 . 
     22. Electroplate 4 microns of CoNiFe. This step is shown in  FIG. 90 . 
     23. Deposit a seed layer of CoNiFe. 
     24. Spin on 4 microns of resist, expose with Mask  7 , and develop. This mask defines the roof of the magnetic plunger, the nozzle chamber wall, the lever arm, the springs, and the spring posts. The resist forms an electroplating mold for these parts. This step is shown in  FIG. 91 . 
     25. Electroplate 3 microns of CoNiFe. This step is shown in  FIG. 92 . 
     26. Mount the wafer on a glass blank and back-etch the wafer using KOH, with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in  FIG. 93 . 
     27. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask  8 . This mask defines the nozzle rim. This step is shown in  FIG. 94 . 
     28. Plasma back-etch through the boron doped layer using Mask  9 . This mask defines the nozzle, and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in  FIG. 95 . 
     29. Detach the chips from the glass blank. Strip all adhesive, resist, sacrificial, and exposed seed layers. This step is shown in  FIG. 96 . 
     30. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     31. Connect the printheads to their interconnect systems. 
     32. Hydrophobize the front surface of the printheads. 
     33. Fill the completed printheads with ink and test them. A filled nozzle is shown in  FIG. 97 . 
     IJ06 
     Referring now to  FIG. 98 , there is illustrated a cross-sectional view of a single ink nozzle unit  610  constructed in accordance with a preferred embodiment. The ink nozzle unit  610  includes an ink ejection nozzle  611  for the ejection of ink which resides in a nozzle chamber  613 . The ink is ejected from the nozzle chamber  613  by means of movement of paddle  615 . The paddle  615  operates in a magnetic field  616  which runs along the plane of the paddle  615 . The paddle  615  includes at least one solenoid coil  617  which operates under the control of nozzle activation signal. The paddle  615  operates in accordance with the well known principal of the force experienced by a moving electric charge in a magnetic field. Hence, when it is desired to activate the paddle  615  to eject an ink drop out of ink ejection nozzle  611 , the solenoid coil  617  is activated. As a result of the activation, one end of the paddle will experience a downward force  619  (See  FIG. 99 ) while the other end of the paddle will experience an upward force  620 . The downward force  619  results in a corresponding movement of the paddle and the resultant ejection of ink. 
     As can be seen from the cross section of  FIG. 98 , the paddle  615  can comprise multiple layers of solenoid wires with the solenoid wires, e.g.  621 , forming a complete circuit having the current flow in a counter clockwise direction around a centre of the paddle  615 . This results in paddle  615  experiencing a rotation about an axis through (as illustrated in  FIG. 99 ) the centre point the rotation being assisted by means of a torsional spring, e.g.  622 , which acts to return the paddle  615  to its quiescent state after deactivation of the current paddle  615 . Whilst a torsional spring  622  is to be preferred it is envisaged that other forms of springs may be possible such as a leaf spring or the like. 
     The nozzle chamber  613  refills due to the surface tension of the ink at the ejection nozzle  611  after the ejection of ink. 
     Manufacturing Construction Process 
     The construction of the inkjet nozzles can proceed by way of utilisation of microelectronic fabrication techniques commonly known to those skilled in the field of semi-conductor fabrication. 
     In accordance with one form of construction, two wafers are utilized upon which the active circuitry and ink jet print nozzles are fabricated and a further wafer in which the ink channels are fabricated. 
     Turning now to  FIG. 100 , there is illustrated an exploded perspective view of a single ink jet nozzle constructed in accordance with a preferred embodiment. Construction begins which a silicon wafer (see  FIG. 102 ) upon which has been fabricated an epitaxial boron doped layer  641  and an epitaxial silicon layer  642 . The boron layer is doped to a concentration of preferably 10 20 /cm 3  of boron or more and is approximately 2 microns thick. The silicon epitaxial layer is constructed to be approximately 8 microns thick and is doped in a manner suitable for the active semi conductor device technology. 
     Next, the drive transistors and distribution circuitry are constructed in accordance with the fabrication process chosen resulting in a CMOS logic and drive transistor level  643 . A silicon nitride layer (not shown) is then deposited. 
     The paddle metal layers are constructed utilizing a damascene process which is a well known process utilizing chemical mechanical polishing techniques (CMP) well known for utilization as a multi-level metal application. The solenoid coils in paddle  615  ( FIG. 98 ) can be constructed from a double layer which for a first layer  645 , is produced utilizing a single damascene process. 
     Next, a second layer  646  is deposited utilizing this time a dual damascene process. The copper layers  645 ,  646  include contact posts  647 ,  648 , for interconnection of the electromagnetic coil to the CMOS layer  643  through vias in the silicon nitride layer (not shown). However, the metal post portion also includes a via interconnecting it with the lower copper level. The damascene process is finished with a planarized glass layer. The glass layers produced during utilisation of the damascene processes utilized for the deposition of layers  645 ,  646 , are shown as one layer  675  in  FIG. 100 . 
     Subsequently, the paddle is formed and separated from the adjacent glass layer by means of a plasma etch as the etch being down to the position of silicon layer  642 . Further, the nozzle chamber  613  underneath the panel is removed by means of a silicon anisotropic wet etch which will edge down to the boron layer  641 . A passivation layer is then applied. The passivation layer can comprise a conformable diamond like carbon layer or a high density Si 3 N 4  coating, this coating provides a protective layer for the paddle and its surrounds as the paddle must exist in the highly corrosive environment water and ink. 
     Next, the silicon wafer can be back-etched through the boron doped layer and the ejection port  611  and an ejection port rim  650  ( FIG. 98 ) can also be formed utilizing etching procedures. 
     One form of alternative detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  640  deposit 3 microns of epitaxial silicon heavily doped with boron  641 . 
     2. Deposit 10 microns of epitaxial silicon  642 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete a 0.5 micron, one poly, 2 metal CMOS process to form layers  643 . This step is shown in  FIG. 102 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 101  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Deposit 0.1 microns of silicon nitride (Si 3 N 4 ) (not shown). 
     5. Etch the nitride layer using Mask  1 . This mask defines the contact vias from the solenoid coil to the second-level metal contacts. 
     6. Deposit a seed layer of copper. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     7. Spin on 3 microns of resist  690 , expose with Mask  2 , and develop. This mask defines the first level coil of the solenoid. The resist acts as an electroplating mold. This step is shown in  FIG. 103 . 
     8. Electroplate  2  microns of copper  645 . 
     9. Strip the resist and etch the exposed copper seed layer. This step is shown in  FIG. 104 . 
     10. Deposit 0.1 microns of silicon nitride (Si 3 N 4 )  691 . 
     11. Etch the nitride layer using Mask  3 . This mask defines the contact vias  647 ,  648  between the first level and the second level of the solenoid. 
     12. Deposit a seed layer of copper. 
     13. Spin on 3 microns of resist  692 , expose with Mask  4 , and develop. This mask defines the second level coil of the solenoid. The resist acts as an electroplating mold. This step is shown in  FIG. 105 . 
     14. Electroplate 2 microns of copper  646 . 
     15. Strip the resist and etch the exposed copper seed layer. This step is shown in  FIG. 106 . 
     16. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     17. Deposit 0.1 microns of silicon nitride  693 . 
     18. Etch the nitride and CMOS oxide layers down to silicon using Mask  5 . This mask defines the nozzle chamber mask and the edges  670  of the print heads chips for crystallographic wet etching. This step is shown in FIG.  107 . 
     19. Crystallographically etch the exposed silicon using KOH. This etch stops on &lt;111&gt; crystallographic planes  694 , and on the boron doped silicon buried layer. Due to the design of Mask  5 , this etch undercuts the silicon, providing clearance for the paddle to rotate downwards. 
     20. Mount the wafer on a glass blank  695  and back-etch the wafer using KOH, with no mask This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in  FIG. 108 . 
     21. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask  6 . This mask defines the nozzle rim  650 . This step is shown in  FIG. 109 . 
     22. Plasma back-etch through the boron doped layer using Mask  7 . This mask defines the ink ejection nozzle  611 , and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in  FIG. 110 . 
     23. Strip the adhesive layer to detach the chips from the glass blank. This step is shown in  FIG. 111 . 
     24. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     25. Connect the print heads to their interconnect systems. 
     26. Hydrophobize the front surface of the print heads. 
     27. Fill with ink  696 , apply a strong magnetic field in the plane of the chip surface, and test the completed print heads. A filled nozzle is shown in  FIG. 112 . 
     IJ07 
     Turning initially to  FIG. 113 , there is illustrated a perspective view in section of a single nozzle apparatus  701  constructed in accordance with the techniques of a preferred embodiment. 
     Each nozzle apparatus  701  includes a nozzle outlet port  702  for the ejection of ink from a nozzle chamber  704  as a result of activation of an electromagnetic piston  705 . The electromagnetic piston  705  is activated via a solenoid coil  706  which is positioned about the piston  705 . When a current passes through the solenoid coil  706 , the piston  705  experiences a force in the direction as indicated by an arrow  713 . As a result, the piston  705  begins moving towards the outlet port  702  and thus imparts momentum to ink within the nozzle chamber  704 . The piston  705  is mounted on torsional springs  708 ,  709  so that the springs  708 ,  709  act against the movement of the piston  705 . The torsional springs  708  are configured so that they do not fully stop the movement of the piston  705 . 
     Upon completion of an ejection cycle, the current to the coil  706  is turned off. As a result, the torsional springs  708 ,  709  act to return the piston  705  to its rest position as initially shown in  FIG. 113 . Subsequently, surface tension forces cause the chamber  704  to refill with ink and to return ready for “re-firing”. 
     Current to the coil  706  is provided via aluminum connectors (not shown) which interconnect the coil  706  with a semi-conductor drive transistor and logic layer  718 . 
     Construction 
     A liquid ink jet print head has one nozzle apparatus  701  associated with a respective one of each of a multitude of nozzle apparatus  701 . It will be evident that each nozzle apparatus  701  has the following major parts, which are constructed using standard semi-conductor and micromechanical construction techniques: 
     1. Drive circuitry within the logic layer  718 . 
     2. The nozzle outlet port  702 . The radius of the nozzle outlet port  702  is an important determinant of drop velocity and drop size. 
     3. The magnetic piston  705 . This can be manufactured from a rare earth magnetic material such as neodymium iron boron (NdFeB) or samarium cobalt (SaCo). The pistons  705  are magnetised after a last high temperature step in the fabrication of the print heads, to ensure that the Curie temperature is not exceeded after magnetisation. A typical print head may include many thousands of pistons  705  all of which can be magnetised simultaneously and in the same direction. 
     4. The nozzle chamber  704 . The nozzle chamber  704  is slightly wider than the piston  705 . The gap  750  between the piston  705  and the nozzle chamber  704  can be as small as is required to ensure that the piston  705  does not contact the nozzle chamber  704  during actuation or return of the piston  705 . If the print heads are fabricated using a standard 0.5 μm lithography process, then a 1 μm gap will usually be sufficient. The nozzle chamber  704  should also be deep enough so that air ingested through the outlet port  702  when the piston  705  returns to its quiescent state does not extend to the piston  705 . If it does, the ingested air bubble may form a cylindrical surface instead of a hemispherical surface. If this happens, the nozzle chamber  704  may not refill properly. 
     5. The solenoid coil  706 . This is a spiral coil of copper. A double layer spiral is used to obtain a high field strength with a small device radius. Copper is used for its low resistivity, and high electro-migration resistance. 
     6. Springs  708 . The springs  708  return the piston  705  to its quiescent position after a drop of ink has been ejected. The springs  708  can be fabricated from silicon nitride. 
     7. Passivation layers. All surfaces are coated with passivation layers, which may be silicon nitride (Si 3 N 4 ), diamond like carbon (DLC), or other chemically inert, highly impermeable layer. The passivation layers are especially important for device lifetime, as the active device is immersed in the ink. 
     Example Method of Fabrication 
     The print head is fabricated from two silicon apparatus wafers. A first wafer is used to fabricate the nozzle apparatus (the print head wafer) and a second wafer is utilized to fabricate the various ink channels in addition to providing a support means for the first channel (the Ink Channel Wafer).  FIG. 114  is an exploded perspective view illustrating the construction of the ink jet nozzle apparatus  701  on a print head wafer. The fabrication process proceeds as follows: 
     Start with a single silicon wafer, which has a buried epitaxial layer  721  of silicon which is heavily doped with boron. The boron should be doped to preferably 10 20  atoms per cm 3  of boron or more, and be approximately 3 μm thick. A lightly doped silicon epitaxial layer  722  on top of the boron doped layer  721  should be approximately 8 μm thick, and be doped in a manner suitable for the active semiconductor device technology chosen. This is the starting point for the print head wafer. The wafer diameter should be the same as that of the ink channel wafer. 
     Next, fabricate the drive transistors and data distribution circuitry required for each nozzle according to the process chosen, in a standard CMOS layer  718  up until oxide over the first level metal. On top of the CMOS layer  718  is deposited a silicon nitride passivation layer  725 . Next, a silicon oxide layer  727  is deposited. The silicon oxide layer  727  is etched utilizing a mask for a copper coil layer. Subsequently, a copper layer  730  is deposited through the mask for the copper coil. The layers  727 ,  725  also include vias (not shown) for the interconnection of the copper coil layer  730  to the underlying CMOS layer  718 . Next, the nozzle chamber  704  ( FIG. 113 ) is etched. Subsequently, a sacrificial material is deposited to fill the etched volume (not shown) entirely. On top of the sacrificial material a silicon nitride layer  731  is deposited, including site portions  732 . Next, the magnetic material layer  733  is deposited utilizing the magnetic piston mask This layer also includes posts,  734 . 
     A final silicon nitride layer  735  is then deposited onto an additional sacrificial layer (not shown) to cover the bare portions of nitride layer  731  to the height of the magnetic material layer  733 , utilizing a mask for the magnetic piston and the torsional springs  708 . The torsional springs  708 , and the magnetic piston  705  (see  FIG. 113 ) are liberated by etching the aforementioned sacrificial material. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  751  deposit 3 microns of epitaxial silicon heavily doped with boron  721 . 
     2. Deposit  10  microns of epitaxial silicon  722 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete a 0.5 micron, one poly, 2 metal CMOS process  718 . The metal layers are copper instead of aluminum, due to high current densities and subsequent high temperature processing. This step is shown in  FIG. 116 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 115  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Deposit 0.5 microns of low stress PECVD silicon nitride (Si 3 N 4 )  752 . The nitride acts as a dielectric, and etch stop, a copper diffusion barrier, and an ion diffusion barrier. As the speed of operation of the print head is low, the high dielectric constant of silicon nitride is not important, so the nitride layer can be thick compared to sub-micron CMOS back-end processes. 
     5. Etch the nitride layer using Mask  1 . This mask defines the contact vias  753  from the solenoid coil to the second-level metal contacts, as well as the nozzle chamber. This step is shown in  FIG. 117 . 
     6. Deposit 4 microns of PECVD glass  754 . 
     7. Etch the glass down to nitride or second level metal using Mask  2 . This mask defines the solenoid. This step is shown in  FIG. 118 . 
     8. Deposit a thin barrier layer of Ta or TaN. 
     9. Deposit a seed layer of copper. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     10. Electroplate 4 microns of copper  755 . 
     11. Planarize using CMP. Steps 4 to 11 represent a copper dual damascene process, with a 4:1 copper aspect ratio (4 microns high, 1 micron wide). This step is shown in  FIG. 119 . 
     12. Etch down to silicon using Mask  3 . This mask defines the nozzle cavity. This step is shown in  FIG. 120 . 
     13. Crystallographically etch the exposed silicon using KOH. This etch stops on &lt;111&gt; crystallographic planes  756 , and on the boron doped silicon buried layer. This step is shown in  FIG. 121 . 
     14. Deposit 0.5 microns of low stress PECVD silicon nitride  757 . 
     15. Open the bond pads using Mask  4 . 
     16. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     17. Deposit a thick sacrificial layer  758  (e.g. low stress glass), filling the nozzle cavity. Planarize the sacrificial layer to a depth of 5 microns over the nitride surface. This step is shown in  FIG. 122 . 
     18. Etch the sacrificial layer to a depth of 6 microns using Mask  5 . This mask defines the permanent magnet of the pistons plus the magnet support posts. This step is shown in  FIG. 123 . 
     19. Deposit 6 microns of permanent magnet material such as neodymium iron boron (NdFeB)  759 . Planarize. This step is shown in  FIG. 124 . 
     20. Deposit 0.5 microns of low stress PECVD silicon nitride  760 . 
     21. Etch the nitride using Mask  6 , which defines the spring. This step is shown in  FIG. 125 . 
     22. Anneal the permanent magnet material at a temperature which is dependant upon the material. 
     23. Place the wafer in a uniform magnetic field of 2 Tesla (20,000 Gauss) with the field normal to the chip surface. This magnetizes the permanent magnet. 
     24. Mount the wafer on a glass blank and back-etch the wafer using KOH, with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in  FIG. 126 . 
     25. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask  7 . This mask defines the nozzle rim  762 . This step is shown in  FIG. 127 . 
     26. Plasma back-etch through the boron doped layer using Mask  8 . This mask defines the nozzle  702 , and the edge of the chips. 
     27. Plasma back-etch nitride up to the glass sacrificial layer through the holes in the boron doped silicon layer. At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in  FIG. 128 . 
     28. Strip the adhesive layer to detach the chips from the glass blank. 
     29. Etch the sacrificial glass layer in buffered HF. This step is shown in  FIG. 129 . 
     30. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     31. Connect the print heads to their interconnect systems. 
     32. Hydrophobize the front surface of the print heads. 
     33. Fill the completed print heads with ink  763  and test them. A filled nozzle is shown in  FIG. 130 . 
     IJ08 
     In a preferred embodiment, a shutter is actuated by means of a magnetic coil, the coil being used to move the shutter to thereby cause the shutter to open or close. The shutter is disposed between an ink reservoir having an oscillating ink pressure and a nozzle chamber having an ink ejection port defined therein for the ejection of ink. When the shutter is open, ink is allowed to flow from the ink reservoir through to the nozzle chamber and thereby cause an ejection of ink from the ink ejection port When the shutter is closed, the nozzle chamber remains in a stable state such that no ink is ejected from the chamber. 
     Turning now to  FIG. 131 , there is illustrated a single ink jet nozzle arrangement  810  in a closed position. The arrangement  810  includes a series of shutters  811  which are located above corresponding apertures to a nozzle chamber. In  FIG. 132 , the ink jet nozzle  810  is illustrated in an open position which also illustrates the apertures  812  providing a fluid interconnection to a nozzle chamber  813  and an ink ejection port  814 . The shutters e.g.  811  as shown in  FIGS. 131 and 132  are interconnected and further connected to an arm  816  which is pivotally mounted about a pivot point  817  about which the shutters e.g.  811  rotate. The shutter  811  and arm  816  are constructed from nickel iron (NiFe) so as to be magnetically attracted to an electromagnetic device  819 . The electromagnetic device  819  comprises a NiFe core  820  around which is constructed a copper coil  821 . The copper coil  821  is connected to a lower drive layer via vias  823 ,  824 . The coil  819  is activated by sending a current through the coil  821  which results in its magnification and corresponding attraction in the areas  826 ,  827 . The high levels of attraction are due to its close proximity to the ends of the electromagnet  819 . This results in a general rotation of the surfaces  826 ,  827  around the pivot point  817  which in turn results in a corresponding rotation of the shutter  811  from a closed to an open position. 
     A number of coiled springs  830 - 832  are also provided. The coiled springs store energy as a consequence of the rotation of the shutter  811 . Hence, upon deactivation of the electromagnet  819  the coil springs  830 - 832  act to return the shutter  811  to its closed position. As mentioned previously, the opening and closing of the shutter  811  allows for the flow of ink to the ink nozzle chamber for a subsequent ejection. The coil  819  is activated rotating the arm  816  bringing the surfaces  826 ,  827  into close contact with the electromagnet  819 . The surfaces  826 ,  827  are kept in contact with the electromagnet  819  by means of utilisation of a keeper current which, due the close proximity between the surfaces  826 ,  827  is substantially less than that required to initially move the arm  816 . 
     The shutter  811  is maintained in the plane by means of a guide  834  which overlaps slightly with an end portion of the shutter  811 . 
     Turning now to  FIG. 133 , there is illustrated an exploded perspective of one form of construction of a nozzle arrangement  810  in accordance with a preferred embodiment The bottom level consists of a boron doped silicon layer  840  which can be formed from constructing a buried epitaxial layer within a selected wafer and then back etching using the boron doped layer as an etch stop. Subsequently, there is provided a silicon layer  841  which includes a crystallographically etched pit forming the nozzle chamber  813 . On top of the silicon layer  841  there is constructed a 2 micron silicon dioxide layer  842  which includes the nozzle chamber pit opening whose side walls are passivated by a subsequent nitride layer. On top of the silicon dioxide layer  842  is constructed a nitride layer  844  which provides passivation of the lower silicon dioxide layer and also provides a base on which to construct the electromagnetic portions and the shutter. The nitride layer  844  and lower silicon dioxide layer having suitable vias for the interconnection to the ends of the electromagnetic circuit for the purposes of supplying power on demand to the electromagnetic circuit. 
     Next, a copper layer  845  is provided. The copper layer providing a base wiring layer for the electromagnetic array in addition to a lower portion of the pivot  817  and a lower portion of the copper layer being used to form a part of the construction of the guide  834 . 
     Next, a NiFe layer  847  is provided which is used for the formation of the internal portions  820  of the electromagnet, in addition to the pivot, aperture arm and shutter  811  in addition to a portion of the guide  834 , in addition to the various spiral springs. On top of the NiFe layer  847  is provided a copper layer  849  for providing the top and side windings of the coil  821  in addition to providing the formation of the top portion of guide  834 . Each of the layers  845 ,  847  can be conductively insulated from its surroundings where required through the use of a nitride passivation layer (not shown). Further, a top passivation layer can be provided to cover the various top layers which will be exposed to the ink within the ink reservoir and nozzle chamber. The various levels  845 ,  849  can be formed through the use of supporting sacrificial structures which are subsequently sacrificially etched away to leave the operable device. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed using the following steps: 
     1. Using a double sided polished wafer  850  deposit 3 microns of epitaxial silicon heavily doped with boron  840 . 
     2. Deposit 10 microns of epitaxial silicon  841 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete a 0.5 micron, one poly, 2 metal CMOS process  842 . This step is shown in  FIG. 135 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 134  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber, and the edges of the printheads chips. This step is shown in  FIG. 136 . 
     5. Crystallographically etch the exposed silicon using KOH. This etch stops on &lt;111&gt; crystallographic planes  851 , and on the boron doped silicon buried layer. This step is shown in  FIG. 137 . 
     6. Deposit 10 microns of sacrificial material  852 . Planarize down to oxide using CMP. The sacrificial material temporarily fills the nozzle cavity. This step is shown in  FIG. 138 . 
     7. Deposit 0.5 microns of silicon nitride (Si 3 N 4 )  844 . 
     8. Etch nitride  844  and oxide down to aluminum or sacrificial material using Mask  3 . This mask defines the contact vias  823 ,  824  from the aluminum electrodes to the solenoid, as well as the fixed grill over the nozzle cavity. This step is shown in  FIG. 139 . 
     9. Deposit a seed layer of copper. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     10. Spin on 2 microns of resist  853 , expose with Mask  4 , and develop. This mask defines the lower side of the solenoid square helix, as well as the lowest layer of the shutter grill vertical stop. The resist acts as an electroplating mold. This step is shown in  FIG. 140 . 
     11. Electroplate 1 micron of copper  854 . This step is shown in  FIG. 141 . 
     12. Strip the resist and etch the exposed copper seed layer. This step is shown in  FIG. 142 . 
     13. Deposit 0.1 microns of silicon nitride. 
     14. Deposit 0.5 microns of sacrificial material  855 . 
     15. Etch the sacrificial material down to nitride using Mask  5 . This mask defines the solenoid, the fixed magnetic pole, the pivot  817  ( FIG. 131 ), the spring posts, and the middle layer of the shutter grill vertical stop. This step is shown in  FIG. 143 . 
     16. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosen due to a high saturation flux density of 2 Tesla, and a low coercivity. [Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturation magnetic flux density, Nature 392, 796-798 (1998)]. 
     17. Spin on 3 microns of resist  856 , expose with Mask  6 , and develop. This mask defines all of the soft magnetic parts, being the fixed magnetic pole, the pivot  817 , the shutter grill, the lever arm  816 , the spring posts, and the middle layer of the shutter grill vertical stop. The resist acts as an electroplating mold. This step is shown in  FIG. 144 . 
     18. Electroplate 2 microns of CoNiFe  857 . This step is shown in  FIG. 145 . 
     19. Strip the resist and etch the exposed seed layer. This step is shown in  FIG. 146 . 
     20. Deposit 0.1 microns of silicon nitride (Si 3 N 4 ). 
     21. Spin on 2 microns of resist  858 , expose with Mask  7 , and develop. This mask defines the solenoid vertical wire segments, for which the resist acts as an electroplating mold. This step is shown in  FIG. 147 . 
     22. Etch the nitride down to copper using the Mask  7  resist. 
     23. Electroplate 2 microns of copper  859 . This step is shown in  FIG. 148 . 
     24. Deposit a seed layer of copper. 
     25. Spin on 2 microns of resist  860 , expose with Mask  8 , and develop. This mask defines the upper side of the solenoid square helix, as well as the upper layer of the shutter grill vertical stop. The resist acts as an electroplating mold. This step is shown in  FIG. 149 . 
     26. Electroplate 1 micron of copper  861 . This step is shown in  FIG. 150 . 
     27. Strip the resist and etch the exposed copper seed layer, and strip the newly exposed resist This step is shown in  FIG. 151 . 
     28. Deposit 0.1 microns of conformal silicon nitride as a corrosion barrier. 
     29. Open the bond pads using Mask  9 . 
     30. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     31. Mount the wafer on a glass blank  862  and back-etch the wafer using KOH, with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer  840 . This step is shown in  FIG. 152 . 
     32. Plasma back-etch the boron doped silicon layer  840  to a depth of  1  micron using Mask  9 . This mask defines the nozzle rim  863 . This step is shown in  FIG. 153 . 
     33. Plasma back-etch through the boron doped layer  840  using Mask  10 . This mask defines the nozzle  814 , and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in  FIG. 154 . 
     34. Detach the chips from the glass blank  862 . Strip all adhesive, resist, sacrificial, and exposed seed layers. This step is shown in  FIG. 155 . 
     35. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. The package also includes a piezoelectric actuator attached to the rear of the ink channels. The piezoelectric actuator provides the oscillating ink pressure required for the ink jet operation. 
     36. Connect the printheads to their interconnect systems. 
     37. Hydrophobize the front surface of the printheads. 
     38. Fill the completed printheads with ink  864  and test them. A filled nozzle is shown in  FIG. 156 . 
     IJ09 
     In a preferred embodiment, each nozzle chamber having a nozzle ejection portal further includes two thermal actuators. The first thermal actuator is utilized for the ejection of ink from the nozzle chamber while a second thermal actuator is utilized for pumping ink into the nozzle chamber for rapid ejection of subsequent drops. 
     Normally, ink chamber refill is a result of surface tension effects of drawing ink into a nozzle chamber. In a preferred embodiment, the nozzle chamber refill is assisted by an actuator which pumps ink into the nozzle chamber so as to allow for a rapid refill of the chamber and therefore a more rapid operation of the nozzle chamber in ejecting ink drops. 
     Turning to  FIGS. 157-162  which represent various schematic cross sectional views of the operation of a single nozzle chamber, the operation of a preferred embodiment will now be discussed. In  FIG. 157 , a single nozzle chamber is schematically illustrated in section. The nozzle arrangement  910  includes a nozzle chamber  911  filled with ink and a nozzle ink ejection port  912  having an ink meniscus  913  in a quiescent position. The nozzle chamber  911  is interconnected to an ink reservoir  915  for the supply of ink to the nozzle chamber. Two paddle-type thermal actuators  916 ,  917  are provided for the control of the ejection of ink from nozzle port  912  and the refilling of chamber  911 . Both of the thermal actuators  916 ,  917  are controlled by means of passing an electrical current through a resistor so as to actuate the actuator. The structure of the thermal actuators  916 ,  917  will be discussed further herein after. The arrangement of  FIG. 157  illustrates the nozzle arrangement when it is in its quiescent or idle position. 
     When it is desired to eject a drop of ink via the port  912 , the actuator  916  is activated, as shown in  FIG. 158 . The activation of activator  916  results in it bending downwards forcing the ink within the nozzle chamber out of the port  912 , thereby resulting in a rapid growth of the ink meniscus  913 . Further, ink flows into the nozzle chamber  911  as indicated by arrow  919 . 
     The main actuator  916  is then retracted as illustrated in  FIG. 159 , which results in a collapse of the ink meniscus so as to form ink drop  920 . The ink drop  920  eventually breaks off from the main body of ink within the nozzle chamber  911 . 
     Next, as illustrated in  FIG. 160 , the actuator  917  is activated so as to cause rapid refill in the area around the nozzle portal  912 . The refill comes generally from ink flows  921 ,  922 . 
     Next, two alternative procedures are utilized depending on whether the nozzle chamber is to be fired in a next ink ejection cycle or whether no drop is to be fired. The case where no drop is to be fired is illustrated in  FIG. 161  and basically comprises the return of actuator  917  to its quiescent position with the nozzle port area refilling by means of surface tension effects drawing ink into the nozzle chamber  911 . 
     Where it is desired to fire another drop in the next ink drop ejection cycle, the actuator  916  is activated simultaneously which is illustrated in  FIG. 162  with the return of the actuator  917  to its quiescent position. This results in more rapid refilling of the nozzle chamber  911  in addition to simultaneous drop ejection from the ejection nozzle  912 . 
     Hence, it can be seen that the arrangement as illustrated in  FIGS. 157 to 162  results in a rapid refilling of the nozzle chamber  911  and therefore the more rapid cycling of ejecting drops from the nozzle chamber  911 . This leads to higher speed and improved operation of a preferred embodiment. 
     Turning now to  FIG. 163 , there is a illustrated a sectional perspective view of a single nozzle arrangement  910  of a preferred embodiment A preferred embodiment can be constructed on a silicon wafer with a large number of nozzles  910  being constructed at any one time. The nozzle chambers can be constructed through back etching a silicon wafer to a boron doped epitaxial layer  930  using the boron doping as an etchant stop. The boron doped layer is then further etched utilizing the relevant masks to form the nozzle port  912  and nozzle rim  931 . The nozzle chamber proper is formed from a crystallographic etch of the portion of the silicon wafer  932 . The silicon wafer can include a two level metal standard CMOS layer  933  which includes the interconnect and drive circuitry for the actuator devices. The CMOS layer  933  is interconnected to the actuators via appropriate vias. On top of the CMOS layer  933  is placed a nitride layer  934 . The nitride layer is provided to passivate the lower CMOS layer  933  from any sacrificial etchant which is utilized to etch sacrificial material in construction of the actuators  916 ,  917 . The actuators  916 ,  917  can be constructed by filling the nozzle chamber  911  with a sacrificial material, such as sacrificial glass and depositing the actuator layers utilizing standard micro-electro-mechanical systems (MEMS) processing techniques. 
     On top of the nitride layer  934  is deposited a first PTFE layer  935  followed by a copper layer  936  and a second PTFE layer  937 . These layers are utilized with appropriate masks so as to form the actuators  916 ,  917 . The copper layer  936  is formed near the top surface of the corresponding actuators and is in a serpentine shape. Upon passing a current through the copper layer  936 , the copper layer is heated. The copper layer  936  is encased in the PTFE layers  935 ,  937 . PTFE has a much greater coefficient of thermal expansion than copper (770×10 4 ) and hence is caused to expand more rapidly than the copper layer  936 , such that, upon heating, the copper serpentine shaped layer  936  expands via concertinaing at the same rate as the surrounding Teflon layers. Further, the copper layer  936  is formed near the top of each actuator and hence, upon heating of the copper element, the lower PTFE layer  935  remains cooler than the upper PTFE layer  937 . This results in a bending of the actuator so as to achieve its actuation effects. The copper layer  936  is interconnected to the lower CMOS layer  934  by means of vias eg  939 . Further, the PTFE layers  935 / 937 , which are normally hydrophobic, undergo treatment so as to be hydrophilic. Many suitable treatments exist such as plasma damaging in an ammonia atmosphere. In addition, other materials having considerable properties can be utilized. 
     Turning to  FIG. 164 , there is illustrated an exploded perspective of the various layers of an ink jet nozzle  910  as constructed in accordance with a single nozzle arrangement  910  of a preferred embodiment The layers include the lower boron layer  930 , the silicon and anisotropically etched layer  932 , CMOS glass layer  933 , nitride passivation layer  934 , copper heater layer  936  and PTFE layers  935 ,  937 , which are illustrated in one layer but formed with an upper and lower Teflon layer embedding copper layer  936 . 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  950  deposit 3 microns of epitaxial silicon heavily doped with boron  930 . 
     2. Deposit  10  microns of epitaxial silicon  932 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete a 0.5 micron, one poly, 2 metal CMOS process  933 . The metal layers are copper instead of aluminum, due to high current densities and subsequent high temperature processing. This step is shown in  FIG. 166 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 165  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers  933  down to silicon or second level metal using Mask  1 . This mask defines the nozzle cavity and the bend actuator electrode contact vias  939 . This step is shown in  FIG. 167 . 
     5. Crystallographically etch the exposed silicon using KOH. This etch stops on (111) crystallographic planes  951 , and on the boron doped silicon buried layer. This step is shown in  FIG. 168 . 
     6. Deposit 0.5 microns of low stress PECVD silicon nitride  934  (Si 3 N 4 ). The nitride acts as an ion diffusion barrier. This step is shown in  FIG. 169 . 
     7. Deposit a thick sacrificial layer  952  (e.g. low stress glass), filling the nozzle cavity. Planarize the sacrificial layer down to the nitride surface. This step is shown in  FIG. 170 . 
     8. Deposit 1.5 microns of polytetrafluoroethylene  935  (PTFE). 
     9. Etch the PTFE using Mask  2 . This mask defines the contact vias  939  for the heater electrodes. 
     10. Using the same mask, etch down through the nitride and CMOS oxide layers to second level metal. This step is shown in  FIG. 171 . 
     11. Deposit and pattern 0.5 microns of gold  953  using a lift-off process using Mask  3 . This mask defines the heater pattern. This step is shown in  FIG. 172 . 
     12. Deposit 0.5 microns of PTFE  937 . 
     13. Etch both layers of PTFE down to sacrificial glass using Mask  4 . This mask defines the gap  954  at the edges of the main actuator paddle and the refill actuator paddle. This step is shown in  FIG. 173 . 
     14. Mount the wafer on a glass blank  955  and back-etch the wafer using KOH, with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in  FIG. 174 . 
     15. Plasma back-etch the boron doped silicon layer to a depth of  1  micron using Mask  5 . This mask defines the nozzle rim  931 . This step is shown in  FIG. 175 . 
     16. Plasma back-etch through the boron doped layer using Mask  6 . This mask defines the nozzle  912 , and the edge of the chips. 
     17. Plasma back-etch nitride up to the glass sacrificial layer through the holes in the boron doped silicon layer. At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in  FIG. 176 . 
     18. Strip the adhesive layer to detach the chips from the glass blank. 
     19. Etch the sacrificial glass layer in buffered HF. This step is shown in  FIG. 177 . 
     20. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     21. Connect the print heads to their interconnect systems. 
     22. Hydrophobize the front surface of the print heads. 
     23. Fill the completed print heads with ink  956  and test them. A filled nozzle is shown in  FIG. 178 . 
     IJ10 
     In a preferred embodiment, an array of the nozzle arrangements is provided with each of the nozzles being under the influence of a outside pulsed magnetic field. The outside pulsed magnetic field causes selected nozzle arrangements to eject ink from their ink nozzle chambers. 
     Turning initially to  FIG. 179  and  FIG. 180 , there is illustrated a side perspective view, partly in section, of a single ink jet nozzle arrangement  1010 .  FIG. 179  illustrates the nozzle arrangement  1010  in a quiescent position and  FIG. 180  illustrates the nozzle arrangement  1010  in an ink ejection position. The nozzle arrangement  1010  has an ink ejection port  1011  for the ejection of ink on demand. The ink ejection port  1011  is connected to an ink nozzle chamber  1012  which is usually filled with ink and supplied from an ink reservoir  1013  via holes e.g.  1015 . 
     A magnetic actuation device  1025  is included and comprises a magnetic soft core  1017  which is surrounded by a nitride coating e.g.  1018 . The nitride coating  1018  includes an end protuberance  1027 . 
     The magnetic core  1017 , operates under the influence of an external pulsed magnetic field. Hence, when the external magnetic field is very high, the actuator  1025  is caused to move rapidly downwards and to thereby cause the ejection of ink from the ink ejection port  1011 . Adjacent the actuator  1025  is provided a blocking mechanism  1020  which comprises a thermal actuator which includes a copper resistive circuit having two arms  1022 ,  1024 . A current is passed through the connected arms  1022 ,  1024  thereby causing them to be heated. The arm  1022 , being of a thinner construction undergoes more resistive heating than the arm  1024  which has a much thicker structure. The arm  1022  is also of a serpentine nature and is encased in polytetrafluoroethylene (PTFE) which has a high coefficient of thermal expansion, thereby increasing the degree of expansion upon heating. The copper portions expand with the PTFE portions by means of a concertina-like movement The arm  1024  has a thinned portion  1029  ( FIG. 181 ) which becomes the concentrated bending region in the resolution of the various forces activated upon heating. Hence, any bending of the arm  1024  is accentuated in the portion  1029  and upon heating, the region  1029  bends so that end portion  1026  ( FIG. 181 ) moves out to block any downward movement of the edge  1027  of the actuator  1025 . Hence, when it is desired to eject an ink drop from a particular nozzle chamber  1012 , the blocking mechanism  1020  is not activated and as a result ink is ejected from the ink ejection port  1011  during the next external magnetic pulse phase. When the nozzle arrangement  1010  is not to eject ink, the locking mechanism  1020  is activated to block any movement of the actuator  1025  and therefore stop the ejection of ink from the port  1011 . Movement of the blocking mechanism is indicated at  1021  in  FIG. 181 . 
     Importantly, the actuator  1020  is located within a cavity  1028  such that the volume of ink flowing past the arm  1022  is extremely low whereas the arm  1024  receives a much larger volume of ink flow during operation. 
     Turning now to  FIG. 181 , there is illustrated an exploded perspective view of a single nozzle arrangement  1010  illustrating the various layers which make up the nozzle arrangement  1010 . The nozzle arrangement  1010  can be constructed on a semiconductor wafer utilizing standard semiconductor processing techniques in addition to those techniques commonly used for the construction of micro-electromechanical systems (MEMS). At the bottom level  1030  is constructed a nozzle plate  1030  including the ink ejection port  1011 . The nozzle plate  1030  can be constructed from a buried boron doped epitaxial layer of a silicon wafer which has been back etched to the point of the epitaxial layer. The epitaxial layer itself is then etched utilizing a mask so as to form a nozzle rim  1031  (See  FIG. 179 ) and the ejection port  1011 . 
     Next, the silicon wafer layer  1032  is etched to define the nozzle chamber  1012 . The silicon layer  1032  is etched to contain substantially vertical side walls by using high density, low pressure plasma etching such as that available from Surface Technology Systems and subsequently filled with sacrificial material which is later etched away. 
     On top of the silicon layer  1032  is deposited a two level CMOS circuitry layer  1033  which comprises substantially glass in addition to the usual metal and poly layers. A layer  1033  includes the formation of the heater element contacts which can be constructed from copper. The PTFE layer  1035  can be provided as a departure from normal construction with a bottom PTFE layer being first deposited followed by a copper layer  1034  and a second PTFE layer to cover the copper layer  1034 . 
     Next, a nitride passivation layer  1036  is provided which acts to provide a passivation surface for the lower layers in addition to providing a base for a soft magnetic Nickel Ferrous layer  1017  which forms the magnetic actuator portion of the actuator  1025 . The nitride layer  1036  includes bending portions  1040  ( FIG. 180 ) utilized in the bending of the actuator. 
     Next a nitride passivation layer  1039  is provided so as to passivate the top and side surfaces of the nickel iron (NiFe) layer  1017 . 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:
     Using a double sided polished wafer  1050  deposit 3 microns of epitaxial silicon heavily doped with boron  1030 .   Deposit 10 microns of epitaxial silicon  1032  either p-type or n-type, depending upon the CMOS process used.   Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  1033 . Relevant features of the wafer at this step are shown in  FIG. 183 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 182  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.   Etch the CMOS oxide layers down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber, and the edges of the print head chips. This step is shown in  FIG. 184 .   Crystallographically etch the exposed silicon using, for example, KOH or EDP (ethylenediamine pyrocatechol). This etch stops on &lt;111&gt; crystallographic planes  1051 , and on the boron doped silicon buried layer. This step is shown in  FIG. 185 .   Deposit 0.5 microns of silicon nitride (Si 3 N 4 )  1052 .   Deposit 10 microns of sacrificial material  1053 . Planarize down to one micron over nitride using CMP. The sacrificial material temporarily fills the nozzle cavity. This step is shown in  FIG. 186 .   Deposit 0.5 microns of polytetrafluoroethylene (PTFE)  1054 .   Etch contact vias in the PTFE, the sacrificial material, nitride, and CMOS oxide layers down to second level metal using Mask  2 . This step is shown in  FIG. 187 .   Deposit 1 micron of titanium nitride (TiN)  1055 .   Etch the TiN using Mask  3 . This mask defines the heater pattern for the hot arm of the catch actuator, the cold arm of the catch actuator, and the catch. This step is shown in  FIG. 188 .   Deposit 1 micron of PTFE  1056 .   Etch both layers of PTFE using Mask  4 . This mask defines the sleeve of the hot arm of the catch actuator. This step is shown in  FIG. 189 .   Deposit a seed layer for electroplating.   Spin on 11 microns of resist  1057 , and expose and develop the resist using Mask  5 . This mask defines the magnetic paddle. This step in shown in  FIG. 190 .   Electroplate 10 microns of ferromagnetic material  1058  such as nickel iron (NiFe). This step is shown in  FIG. 191 .   Strip the resist and etch the seed layer.   Deposit 0.5 microns of low stress PECVD silicon nitride  1059 .   Etch the nitride using Mask  6 , which defines the spring. This step is shown in  FIG. 192 .   Mount the wafer on a glass blank  1060  and back-etch the wafer using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in  FIG. 193 .   Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask  7 . This mask defines the nozzle rim  1031 . This step is shown in  FIG. 194 .   Plasma back-etch through the boron doped layer using Mask  8 . This mask defines the nozzle  1011 , and the edge of the chips.   Plasma back-etch nitride up to the glass sacrificial layer through the holes in the boron doped silicon layer. At this stage, the chips are separate , but are still mounted on the glass blank. This step is shown in  FIG. 195 .   Strip the adhesive layer to detach the chips from the glass blank.   Etch the sacrificial layer. This step is shown in  FIG. 196 .   Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer.   Connect the printheads to their interconnect systems.   Hydrophobize the front surface to the printheads.   Fill the completed print heads with ink  1061 , apply an oscillating magnetic field, and test the printheads. This step is shown in  FIG. 197 .
 
IJ11
   

     In a preferred embodiment, there is provided an ink jet nozzle and chamber filled with ink. Within said jet nozzle chamber is located a static coil and a movable coil. When energized, the static and movable coils are attracted towards one another, loading a spring. The ink drop is ejected from the nozzle when the coils are de-energized. Turn now to  FIGS. 198-201 , there is illustrated schematically the operation of a preferred embodiment In  FIG. 198 , there is shown a single ink jet nozzle chamber  1110  having an ink ejection port  1111  and ink meniscus in this position  1112 . Inside the nozzle chamber  1110  are located a fixed or static coil  1114  and a movable coil  1115 . The arrangement of  FIG. 198  illustrates the quiescent state in the ink jet nozzle chamber. 
     The two coils are then energized resulting in an attraction to one another. This results in the movable plate  1115  moving towards the static or fixed plate  1114  as illustrated in  FIG. 199 . As a result of the movement, springs  1118 ,  1119  are loaded. Additionally, the movement of coil  1115  may cause ink to flow out of the chamber  10  in addition to a change in the shape of the meniscus  1112 . The coils are energized for long enough for the moving coil  1115  to reach its position (approximate two microseconds). The coil currents are then turned to a lower “level” while the nozzle fills. The keeper power can be substantially less than the maximum current level used to move the plate  1115  because the magnetic gap between the plates  1114  and  1115  is at a minimum when the moving coil  1115  is at its stop position. The surface tension on the meniscus  1112  inserts a net force on the ink which results in nozzle refilling as illustrated in  FIG. 200 . The nozzle refilling replaces the volume of the piston withdrawal with ink in a process which should take approximately 100 microseconds. 
     Turning to  FIG. 201 , the coil current is then turned off and the movable coil  1115  acts as a plunger which is accelerated to its normal position by the springs  1118 ,  1119  as illustrated in  FIG. 201 . The spring force on the plunger coil  1115  will be greatest at the beginning of its stroke and slows as the spring elastic stress falls to zero. As a result, the acceleration of plunger plate  1115  is high at the beginning of the stroke but decreases during the stroke resulting in a more uniform ink velocity during the stroke. The movement plate  1115  causes the meniscus to bulge and break off performing ink drop  1120 . The plunger coil  1115  in turn settles in its quiescent position until the next drop ejection cycle. 
     Turning now to  FIG. 202 , there is illustrated a perspective view of one form of construction of an ink jet nozzle  1110 . The ink jet nozzle  1110  can be constructed on a silicon wafer base  1122  as part of a large array of nozzles  1110  which can be formed for the purposes of providing a printhead having a certain dpi, for example, a 1600 dpi printhead. The printhead  1110  can be constructed using advanced silicon semi-conductor fabrication and micro machining and micro fabrication process technology. The wafer is first processed to include lower level drive circuitry (not shown) before being finished off with a two microns thick layer  1150  with appropriate vias for interconnection. Preferably, the CMOS layer can include one level of metal for providing basic interconnects. On top of the layer  1150  is constructed a nitride layer  1123  in which is embedded two coil layers  1125  and  1126 . The coil layers  1125 ,  1126  can be embedded within the nitride layer  1123  through the utilisation of the well-known dual damascene process and chemical mechanical planarization techniques (“Chemical Mechanical Planarisation of Micro Electronic Materials” by Sterger Wald et al published 1997 by John Wiley and Sons Inc., New York, N.Y.). The two coils  1125 ,  1126  are interconnected using a fire at their central point and are further connected, by appropriate vias at ends  1128 ,  1129  to the end points  1128 ,  1129 . Similarly, the movable coil can be formed from two copper coils  1131 ,  1132  which are encased within a further nitride layer  1133 . The copper coil  1131 ,  1132  and nitride layer  1133  also include torsional springs  1136 - 1139  which are formed so that the top moveable coil has a stable state away from the bottom fixed coil. Upon passing a current through the various copper coils, the top copper coils  1131 ,  1132  are attracted to the bottom copper coils  1125 ,  1126  thereby resulting in a loading being placed on the torsional springs  1136 - 1139  such that, when the current is turned off, the springs  1136 - 1139  act to move the top moveable coil to its original position. The nozzle chamber can be formed via nitride wall portions e.g.  1140 ,  1141  having slots e.g.  1151  between adjacent wall portions. The slots  1151  allow for the flow of ink into the chamber as required. A top nitride plate  1144  is provided to cap the top of the internals of  1110  and to provide in flow channel support. The nozzle plate  1144  includes a series of holes  1145  provided to assist in sacrificial etching of lower level layers. Also provided is the ink injection nozzle  1111  having a ridge around its side so as to assist in resisting any in flow on to the outside surface of the nozzle  1110 . The etched through holes  1145  are of much smaller diameter than the nozzle hole  1111  and, as such, surface tension will act to retain the ink within the through holes of  1145  whilst simultaneously the injection of ink from nozzle  1111 . 
     As mentioned previously, the various layers of the nozzle  1110  can be constructed in accordance with standard semi-conductor and micro mechanical techniques. These techniques utilise the dual damascene process as mentioned earlier in addition to the utilisation of sacrificial etch layers to provide support for structures which are later released by means of etching the sacrificial layer. 
     The ink can be supplied within the nozzle  1110  by standard techniques such as providing ink channels along the side of the wafer so as to allow the flow of ink into the area under the surface of nozzle plate  1144 . Alternatively, ink channel portals can be provided through the wafer by a high density low pressure plasma etch processing system such as that available from surface technology system and known as their Advanced Silicon Etch (ASE) process. The etched portals  1145  being so small that surface tension affects not allow the ink to leak out of the small portal holes. In  FIG. 203 , there is shown a final assembled ink jet nozzle ready for the ejection of ink. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed by the following steps: 
     1. Using a double sided polished wafer  1122 , Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  1150 . This step is shown in  FIG. 205 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 204  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Deposit 0.5 microns of low stress PECVD silicon nitride (Si 3 N 4 )  1123 . The nitride acts as a dielectric, and etch stop, a copper diffusion barrier, and an ion diffusion barrier. As the speed of operation of the print head is low, the high dielectric constant of silicon nitride is not important, so the nitride layer can be thick compared to sub-micron CMOS back-end processes. 
     3. Etch the nitride layer using Mask  1 . This mask defines the contact vias  1128 ,  1129  from the solenoid coil to the second-level metal contacts. This step is shown in  FIG. 206 . 
     4. Deposit 1 micron of PECVD glass  1152 . 
     5. Etch the glass down to nitride or second level metal using Mask  2 . This mask defines first layer of the fixed solenoid  1114  (See  FIGS. 198-201 ). This step is shown in  FIG. 207 . 
     6. Deposit a thin barrier layer of Ta or TaN. 
     7. Deposit a seed layer of copper. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     8. Electroplate 1 micron of copper  1153   
     9. Planarize using CMP. Steps 2 to 9 represent a copper dual damascene process. This step is shown in  FIG. 208 . 
     10. Deposit 0.5 microns of low stress PECVD silicon nitride  1154 . 
     11. Etch the nitride layer using Mask  3 . This mask defines the defines the vias from the second layer to the first layer of the fixed solenoid  1114 . This step is shown in  FIG. 209 . 
     12. Deposit 1 micron of PECVD glass  1155 . 
     13. Etch the glass down to nitride or copper using Mask  4 . This mask defines second layer of the fixed solenoid  1114 . This step is shown in  FIG. 210 . 
     14. Deposit a thin barrier layer and seed layer. 
     15. Electroplate 1 micron of copper  1156 . 
     16. Planarize using CMP. Steps 10 to 16 represent a second copper dual damascene process. This step is shown in  FIG. 211 . 
     17. Deposit 0.5 microns of low stress PECVD silicon nitride  1157 . 
     18. Deposit 0.1 microns of PTFE. This is to hydrophobize the space between the two solenoids  1114 ,  1115  (See  FIGS. 198-201 ), so that when the nozzle  1110  fills with ink, this space forms an air bubble. The allows the upper solenoid  1115  to move more freely. 
     19. Deposit 4 microns of sacrificial material  1158 . This forms the space between the two solenoids  1114 ,  1115 . 
     20. Deposit 0.1 microns of low stress PECVD silicon nitride (Not shown). 
     21. Etch the nitride layer, the sacrificial layer, the PTFE layer, and the nitride layer of step 17 using Mask  5 . This mask defines the vias from the first layer of the moving solenoid  1115  to the second layer the fixed solenoid  1114 . This step is shown in  FIG. 212 . 
     22. Deposit 1 micron of PECVD glass  1159 . 
     23. Etch the glass down to nitride or copper using Mask  6 . This mask defines first layer of the moving solenoid. This step is shown in  FIG. 213 . 
     24. Deposit a thin barrier layer and seed layer. 
     25. Electroplate 1 micron of copper  1160 . 
     26. Planarize using CMP. Steps 20 to 26 represent a third copper dual damascene process. This step is shown in  FIG. 214 . 
     27. Deposit 0.1 microns of low stress PECVD silicon nitride  1161 . 
     28. Etch the nitride layer using Mask  7 . This mask defines the vias from the second layer the moving solenoid  1115  to the first layer of the moving solenoid. This step is shown in  FIG. 215 . 
     29. Deposit 1 micron of PECVD glass  1162 . 
     30. Etch the glass down to nitride or copper using Mask  8 . This mask defines the second layer of the moving solenoid  1115 . This step is shown in  FIG. 216 . 
     31. Deposit a thin barrier layer and seed layer. 
     32. Electroplate 1 micron of copper  1163 . 
     33. Planarize using CMP. Steps 27 to 33 represent a fourth copper dual damascene process. This step is shown in  FIG. 217 . 
     34. Deposit 0.1 microns of low stress PECVD silicon nitride  1164 . 
     35. Etch the nitride using Mask  9 . This mask defines the moving solenoid  1115 , including its springs  1136 - 1139 , and allows the sacrificial material in the space between the solenoids  1114 ,  1115  to be etched. It also defines the bond pads. This step is shown in  FIG. 218 . 
     36. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     37. Deposit 10 microns of sacrificial material  1165 . 
     38. Etch the sacrificial material using Mask  10 . This mask defines the nozzle chamber wall  1140 ,  1141 . This step is shown in  FIG. 219 . 
     39. Deposit 3 microns of PECVD glass  1166 . 
     40. Etch to a depth of 1 micron using Mask  11 . This mask defines the nozzle rim  1167 . This step is shown in  FIG. 220 . 
     41. Etch down to the sacrificial layer using Mask  12 . This mask defines the roof  1144  of the nozzle  1110  chamber, and the nozzle itself  1111 . This step is shown in  FIG. 221 . 
     42. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  7 . This mask defines the ink inlets  1168  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 222 . 
     43. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 223 . 
     44. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     45. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     46. Hydrophobize the front surface of the printheads. 
     47. Fill the completed printheads with ink  1169  and test them. A filled nozzle is shown in  FIG. 224 . 
     IJ12 
     In a preferred embodiment, a linear stepper motor is utilized to control a plunger device. The plunger device compressing ink within a nozzle chamber so as to thereby cause the ejection of ink from the chamber on demand. 
     Turning to  FIG. 225 , there is illustrated a single nozzle arrangement  1210  as constructed in accordance with a preferred embodiment. The nozzle arrangement  1210  includes a nozzle chamber  1211  into which ink flows via a nozzle chamber filter portion  1214  which includes a series of posts which filter out foreign bodies in the ink in flow. The nozzle chamber  1211  includes an ink ejection port  1215  for the ejection of ink on demand. Normally, the nozzle chamber  1211  is filled with ink. 
     A linear actuator  1216  is provided for rapidly compressing a nickel ferrous plunger  1218  into the nozzle chamber  1211  so as to compress the volume of ink within chamber  1211  to thereby cause ejection of drops from the ink ejection port  1215 . The plunger  1218  is connected to the stepper moving pole device  1216  which is actuated by means of a three phase arrangement of electromagnets  1220  to  1231 . The electromagnets are driven in three phases with electro magnets  1220 ,  1226 ,  1223  and  1229  being driven in a first phase, electromagnets  1221 ,  1227 ,  1224 ,  1230  being driven in a second phase and electromagnets  1222 ,  1228 ,  1225 ,  1231  being driven in a third phase. The electromagnets are driven in a reversible manner so as to de-actuate plunger  1218  via actuator  1216 . The actuator  1216  is guided at one end by a means of guide  1233 ,  1234 . At the other end, the plunger  1218  is coated with a hydrophobic material such as polytetrafluoroethylene (PTFE) which can form a major part of the plunger  1218 . The PTFE acts to repel the ink from the nozzle chamber  1211  resulting in the creation of a membrane e.g.  1238 ,  1239  (See  FIG. 248   a ) between the plunger  1218  and side walls e.g.  1236 ,  1237 . The surface tension characteristics of the membranes  1238 ,  1239  act to balanced one another thereby guiding the plunger  1218  within the nozzle chamber. The meniscus e.g.  1238 ,  1239  further stops ink from flowing out of the chamber  1211  and hence the electromagnets  1220  to  1231  can be operated in normal air. 
     The nozzle arrangement  1210  is therefore operated to eject drops on demand by means of activating the actuator  1216  by appropriately synchronised driving of electromagnets  1220  to  1231 . The actuation of the actuator  1216  results in the plunger  1218  moving towards the nozzle ink ejection port  1215  thereby causing ink to be ejected from the port  1215 . 
     Subsequently, the electromagnets are driven in reverse thereby moving the plunger in an opposite direction resulting in the in flow of ink from an ink supply connected to the ink inlet port  1214 . 
     Preferably, multiple ink nozzle arrangements  1210  can be constructed adjacent to one another to form a multiple nozzle ink ejection mechanism. The nozzle arrangements  1210  are preferably constructed in an array print head constructed on a single silicon wafer which is subsequently diced in accordance with requirements. The diced print heads can then be interconnected to an ink supply which can comprise a through chip ink flow or ink flow from the side of a chip. 
     Turning now to  FIG. 226 , there is shown an exploded perspective of the various layers of the nozzle arrangement  1210 . The nozzle arrangement can be constructed on top of a silicon wafer  1240  which has a standard electronic circuitry layer such as a two level metal CMOS layer  1241 . The two metal CMOS provides the drive and control circuitry for the ejection of ink from the nozzles by interconnection of the electromagnets to the CMOS layer. On top of the CMOS layer  1241  is a nitride passivation layer  1242  which passivates the lower layers against any ink erosion in addition to any etching of the lower CMOS glass layer should a sacrificial etching process be used in the construction of the nozzle arrangement  1210 . 
     On top of the nitride layer  1242  is constructed various other layers. The wafer layer  1240 , the CMOS layer  1241  and the nitride passivation layer  1242  are constructed with the appropriate fires for interconnecting to the above layers. On top of the nitride layer  1242  is constructed a bottom copper layer  1243  which interconnects with the CMOS layer  1241  as appropriate. Next, a nickel ferrous layer  1245  is constructed which includes portions for the core of the electromagnets and the actuator  1216  and guides  1231 ,  1232 . On top of the NiFe layer  1245  is constructed a second copper layer  1246  which forms the rest of the electromagnetic device. The copper layer  1246  can be constructed using a dual damascene process. Next a PTFE layer  1247  is laid down followed by a nitride layer  1248  which includes the side filter portions and side wall portions of the nozzle chamber. In the top of the nitride layer  1248 , the ejection port  1215  and the rim  1251  are constructed by means of etching. In the top of the nitride layer  1248  is also provided a number of apertures  1250  which are provided for the sacrificial etching of any sacrificial material used in the construction of the various lower layers including the nitride layer  1248 . 
     It will be understood by those skilled in the art of construction of micro-electro-mechanical systems (MEMS) that the various layers  1243 ,  1245  to  1248  can be constructed by means of utilizing a sacrificial material to deposit the structure of various layers and subsequent etching away of the sacrificial material as to release the structure of the nozzle arrangement  1210 . 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  1240 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  1241 . This step is shown in  FIG. 228 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 227  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Deposit 1 micron of sacrificial material  1260 . 
     3. Etch the sacrificial material and the CMOS oxide layers down to second level metal using Mask  1 . This mask defines the contact vias  1261  from the second level metal electrodes to the solenoids. This step is shown in  FIG. 229 . 
     4. Deposit a barrier layer of titanium nitride (TiN) and a seed layer of copper. 
     5. Spin on 2 microns of resist  1262 , expose with Mask  2 , and develop. This mask defines the lower side of the solenoid square helix. The resist acts as an electroplating mold. This step is shown in  FIG. 230 . 
     6. Electroplate 1 micron of copper  1263 . Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     7. Strip the resist and etch the exposed barrier and seed layers. This step is shown in  FIG. 231 . 
     8. Deposit 0.1 microns of silicon nitride. 
     9. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosen due to a high saturation flux density of 2 Tesla, and a low coercivity. [Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturation magnetic flux density, Nature 392, 796-798 (1998)]. 
     10. Spin on 3 microns of resist  1264 , expose with Mask  3 , and develop. This mask defines all of the soft magnetic parts, being the fixed magnetic pole of the solenoids, the moving poles of the linear actuator, the horizontal guides, and the core of the ink plunger. The resist acts as an electroplating mold. This step is shown in  FIG. 232 . 
     11. Electroplate 2 microns of CoNiFe  1265 . This step is shown in  FIG. 233 . 
     12. Strip the resist and etch the exposed seed layer. This step is shown in  FIG. 234 . 
     13. Deposit 0.1 microns of silicon nitride (Si 3 N 4 ) (not shown). 
     14. Spin on 2 microns of resist  1266 , expose with Mask  4 , and develop. This mask defines the solenoid vertical wire segments  1267 , for which the resist acts as an electroplating mold. This step is shown in  FIG. 235 . 
     15. Etch the nitride down to copper using the Mask  4  resist. 
     16. Electroplate 2 microns of copper  1268 . This step is shown in  FIG. 236 . 
     17. Deposit a seed layer of copper. 
     18. Spin on 2 microns of resist  1270 , expose with Mask  5 , and develop. This mask defines the upper side of the solenoid square helix. The resist acts as an electroplating mold. This step is shown in  FIG. 237 . 
     19. Electroplate 1 micron of copper  1271 . This step is shown in  FIG. 238 . 
     20. Strip the resist and etch the exposed copper seed layer, and strip the newly exposed resist This step is shown in  FIG. 239 . 
     21. Open the bond pads using Mask  6 . 
     22. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     23. Deposit 5 microns of PTFE  1272 . 
     24. Etch the PTFE down to the sacrificial layer using Mask  7 . This mask defines the ink plunger. This step is shown in  FIG. 240 . 
     25. Deposit 8 microns of sacrificial material  1273 . Planarize using CMP to the top of the PTFE ink pusher. This step is shown in  FIG. 241 . 
     26. Deposit 0.5 microns of sacrificial material  1275 . This step is shown in  FIG. 242 . 
     27. Etch all layers of sacrificial material using Mask  8 . This mask defines the nozzle chamber wall  1236 ,  1237 . This step is shown in  FIG. 243 . 
     28. Deposit 3 microns of PECVD glass  1276 . 
     29. Etch to a depth of (approx.) 1 micron using Mask  9 . This mask defines the nozzle rim  1251 . This step is shown in  FIG. 244 . 
     30. Etch down to the sacrificial layer using Mask  10 . This mask defines the roof of the nozzle chamber, the nozzle  1215 , and the sacrificial etch access holes  1250 . This step is shown in  FIG. 245 . 
     31. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  11 . Continue the back-etch through the CMOS glass layers until the sacrificial layer is reached. This mask defines the ink inlets  1280  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 246 . 
     32. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch This step is shown in  FIG. 247 . 
     33. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. The package also includes a piezoelectric actuator attached to the rear of the ink channels. The piezoelectric actuator provides the oscillating ink pressure required for the ink jet operation. 
     34. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     35. Hydrophobize the front surface of the printheads. 
     36. Fill the completed printheads with ink  1281  and test them. A filled nozzle is shown in  FIG. 248 . 
     IJ13 
     In a preferred embodiment, an ink jet nozzle chamber is provided having a shutter mechanism which open and closes over a nozzle chamber. The shutter mechanism includes a ratchet drive which slides open and close. The ratchet drive is driven by a gearing mechanism which in turn is driven by a drive actuator which is activated by passing an electric current through the drive actuator in a magnetic field. The actuator force is “geared down” so as to drive a ratchet and pawl mechanism to thereby open and shut the shutter over a nozzle chamber. 
     Turning to  FIG. 249 , there is illustrated a single nozzle arrangement  1310  as shown in an open position The nozzle arrangement  1310  includes a nozzle chamber  1312  having an anisotropic ( 111 ) crystallographic etched pit which is etched down to what is originally a boron doped buried epitaxial layer  1313  which includes a nozzle rim  1314  ( FIG. 251 ) and a nozzle ejection port  1315  which ejects ink. The ink flows in through a fluid passage  1316  when the aperture  1316  is open. The ink flowing through passage  1316  flows from an ink reservoir which operates under an oscillating ink pressure. When the shutter is open, ink is ejected from the ink ejection port  1315 . The shutter mechanism includes a plate  1317  which is driven via means of guide slots  1318 ,  1319  to a closed position. The driving of the nozzle plate is via a latch mechanism  1320  with the plate structure being kept in a correct path by means of retainers  1322  to  1325 . 
     The nozzle arrangement  1310  can be constructed using a two level poly process which can be a standard micro-electro mechanical system production technique (MEMS). The plate  1317  can be constructed from a first level polysilicon and the retainers  1322  to  1325  can be constructed from a lower first level poly portion and a second level poly portion, as it is more apparent from the exploded perspective view illustrated in  FIG. 250 . 
     The bottom circuit of plate  1317  includes a number of pits which are provided on the bottom surface of plate  1317  so as to reduce stiction effects. 
     The ratchet mechanism  1320  is driven by a gearing arrangement which includes first gear wheel  1330 , second gear wheel  1331  and third gear wheel  1332 . These gear wheels  1330  to  1332  are constructed using two level poly with each gear wheel being constructed around a corresponding central pivot  1335  to  1337 . The gears  1330  to  1332  operate to gear down the ratchet speed with the gears being driven by a gear actuator mechanism  1340 . 
     Turning to  FIG. 250  there is illustrated on exploded perspective a single nozzle chamber  1310 . The actuator  1340  comprises mainly a copper circuit having a drive end  1342  which engages and drives the cogs  1343  of the gear wheel  1332 . The copper portion includes serpentine sections  1345 ,  1346  which concertina upon movement of the end  1342 . The end  1342  is actuated by means of passing an electric current through the copper portions in the presence of a magnetic field perpendicular to the surface of the wafer such that the interaction of the magnetic field and circuit result in a Lorenz force acting on the actuator  1340  so as to move the end  1342  to drive the cogs  1343 . The copper portions are mounted on aluminum disks  1348 ,  1349  which are connected to lower levels of circuitry on the wafer upon which actuator  1340  is mounted. 
     Returning to  FIG. 249 , the actuator  1340  can be driven at a high speed with the gear wheels  1330  to  1332  acting to gear down the high speed driving of actuator  1340  so as to drive ratchet mechanism  1320  open and closed on demand. Hence, when it is desired to eject a drop of ink from nozzle  1315 , the shutter is opened by means of driving actuator  1340 . Upon the next high pressure part of the oscillating pressure cycle, ink will be ejected from the nozzle  1315 . If no ink is to be ejected from a subsequent cycle, a second actuator  1350  is utilized to drive the gear wheel in the opposite direction thereby resulting in the closing of the shutter plate  1317  over the nozzle chamber  1312  resulting in no ink being ejected in subsequent pressure cycles. The pits act to reduce the forces required for driving the shutter plate  1317  to an open and closed position. 
     Turning to  FIG. 251 , there is illustrated a top cross-sectional view illustrating the various layers making up a single nozzle chamber  1310 . The nozzle chambers can be formed as part of an array of nozzle chambers making up a single print head which in turn forms part of an array of print head fabricated on a semiconductor wafer in accordance with in accordance with the semiconductor wafer fabrication techniques well known to those skilled in the art of MEMS fabrication and construction. 
     The bottom boron layer  1313  can be formed from the processing step of back etching a silicon wafer utilizing a buried epitaxial boron doped layer as the etch stop. Further processing of the boron layer can be undertaken so as to define the nozzle hole  1315  which can include a nozzle rim  1314 . 
     The next layer is a silicon layer  1352  which normally sits on top of the boron doped layer  1313 . The silicon layer  1352  includes an anisotropically etched pit  1312  so as to define the structure of the nozzle chamber. On top of the silicon layer  1352  is provided a glass layer  1354  which includes the various electrical circuitry (not shown) for driving the actuators. The layer  1354  is passivated by means of a nitride layer  1356  which includes trenches  1357  for passivating the side walls of glass layer  1354 . 
     On top of the passivation layer  1356  is provided a first level polysilicon layer  1358  which defines the shutter and various cog wheels. The second poly layer  1359  includes the various retainer mechanisms and gear wheel  1331 . Next, a copper layer  1360  is provided for defining the copper circuit actuator. The copper  1360  is interconnected with lower portions of glass layer  1354  for forming the circuit for driving the copper actuator. 
     The nozzle chamber  1310  can be constructed using the standard MEMS processes including forming the various layers using the sacrificial material such as silicon dioxide and subsequently sacrificially etching the lower layers away. 
     Subsequently, wafers that contain a series of print heads can be diced into separate printheads mounted on a wall of an ink supply chamber having a piezo electric oscillator actuator for the control of pressure in the ink supply chamber. Ink is then ejected on demand by opening the shutter plate  1317  during periods of high oscillation pressure so as to eject ink. The nozzles being actuated by means of placing the printhead in a strong magnetic field using permanent magnets or electromagnetic devices and driving current through the actuators e.g.  1340 ,  1350  as required to open and close the shutter and thereby eject drops of ink on demand. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer deposit 3 microns of epitaxial silicon heavily doped with boron  1313 . 
     2. Deposit 10 microns of n/n+ epitaxial silicon  1352 . Note that the epitaxial layer is substantially thicker than required for CMOS. This is because the nozzle chambers are crystallographically etched from this layer. This step is shown in  FIG. 253 .  FIG. 252  is a key to representations of various materials in these manufacturing diagrams. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. 
     3. Crystallographically etch the epitaxial silicon using, for example, KOH or EDP (ethylenediamine pyrocatechol)  1370  using MEMS Mask  1 . This mask defines the nozzle cavity. This etch stops on ( 111 ) crystallographic planes, and on the boron doped silicon buried layer. This step is shown in  FIG. 254 . 
     4. Deposit 12 microns of low stress sacrificial oxide  1371 . Planarize down to silicon using CMP. The sacrificial material temporarily fills the nozzle cavity. This step is shown in  FIG. 255 . 
     5. Begin fabrication of the drive transistors, data distribution, and timing circuits using a CMOS process. The MEMS processes which form the mechanical components of the inkjet are interleaved with the CMOS device fabrication steps. The example given here is of a 1 micron, 2 poly, 2 metal retrograde P-well process. The mechanical components are formed from the CMOS polysilicon layers. For clarity, the CMOS active components are omitted. 
     6. Grow the field oxide using standard LOCOS techniques to a thickness of 0.5 microns. As well as the isolation between transistors, the field oxide is used as a MEMS sacrificial layer, so inkjet mechanical details are incorporated in the active area mask. The MEMS features of this step are shown in  FIG. 256 . 
     7. Perform the PMOS field threshold implant. The MEMS fabrication has no effect on this step except in calculation of the total thermal budget 
     8. Perform the retrograde P-well and NMOS threshold adjust implants using the P-well mask. The MEMS fabrication has no effect on this step except in calculation of the total thermal budget. 
     9. Perform the PMOS N-tub deep phosphorus punchthrough control implant and shallow boron implant. The MEMS fabrication has no effect on this step except in calculation of the total thermal budget. 
     10. Deposit and etch the first polysilicon layer  1358 . As well as gates and local connections, this layer includes the lower layer of MEMS components. This includes the lower layer of gears, the shutter, and the shutter guide. It is preferable that this layer be thicker than the normal CMOS thickness. A polysilicon thickness of 1 micron can be used. The MEMS features of this step are shown in  FIG. 256 . 
     11. Perform the NMOS lightly doped drain (LDD) implant This process is unaltered by the inclusion of MEMS in the process flow. 
     12. Perform the oxide deposition and RIE etch for polysilicon gate sidewall spacers. This process is unaltered by the inclusion of MEMS in the process flow. 
     13. Perform the NMOS source/drain implant The extended high temperature anneal time to reduce stress in the two polysilicon layers must be taken into account in the thermal budget for diffusion of this implant. Otherwise, there is no effect from the MEMS portion of the chip. 
     14. Perform the PMOS source/drain implant As with the NMOS source/drain implant, the only effect from the MEMS portion of the chip is on thermal budget for diffusion of this implant. 
     15. Deposit 1 micron of glass  1372  as the first interlevel dielectric and etch using the CMOS contacts mask. The CMOS mask for this level also contains the pattern for the MEMS inter-poly sacrificial oxide. The MEMS features of this step are shown in  FIG. 257 . 
     16. Deposit and etch the second polysilicon layer  1359 . As well as CMOS local connections, this layer includes the upper layer of MEMS components. This includes the upper layer of gears and the shutter guides. A polysilicon thickness of 1 micron can be used. The MEMS features of this step are shown in  FIG. 258 . 
     17. Deposit 1 micron of glass  1373  as the second interlevel dielectric and etch using the CMOS via 1 mask. The CMOS mask for this level also contains the pattern for the MEMS actuator contacts. 
     18. Metal 1  1374  deposition and etch. Metal 1 should be non-corrosive in water, such as gold or platinum, if it is to be used as the Lorenz actuator. The MEMS features of this step are shown in  FIG. 259 . 
     19. Third interlevel dielectric deposition  1375  and etch as shown in  FIG. 260 . This is the standard CMOS third interlevel dielectric. The mask pattern includes complete coverage of the MEMS area. 
     20. Metal 2  1379  deposition and etch. This is the standard CMOS metal 2. The mask pattern includes no metal 2 in the MEMS area. 
     21. Deposit 0.5 microns of silicon nitride (Si 3 N 4 )  1376  and etch using MEMS Mask  2 . This mask defines the region of sacrificial oxide etch performed in step  26 . The silicon nitride aperture is substantially undersized, as the sacrificial oxide etch is isotropic. The CMOS devices must be located sufficiently far from the MEMS devices that they are not affected by the sacrificial oxide etch. The MEMS features of this step are shown in  FIG. 261 . 
     22. Mount the wafer on a glass blank  1377  and back-etch the wafer using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. The MEMS features of this step are shown in  FIG. 262 . 
     23. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using MEMS Mask  3 . This mask defines the nozzle rim  1314 . The MEMS features of this step are shown in  FIG. 263 . 
     24. Plasma back-etch through the boron doped layer using MEMS Mask  4 . This mask defines the nozzle, and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank. The MEMS features of this step are shown in  FIG. 264 . 
     25. Detach the chips from the glass blank. Strip the adhesive. This step is shown in  FIG. 265 . 
     26. Etch the sacrificial oxide using vapor phase etching (VPE) using an anhydrous HF/methanol vapor mixture. The use of a dry etch avoids problems with stiction. This step is shown in  FIG. 266 . 
     27. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. The package also includes a piezoelectric actuator attached to the rear of the ink channels. The piezoelectric actuator provides the oscillating ink pressure required for the ink jet operation. The package also contains the permanent magnets which provide the 1 Tesla magnetic field for the Lorenz actuators formed of metal 1. 
     28. Connect the printheads to their interconnect systems. 
     29. Hydrophobize the front surface of the print heads. 
     30. Fill the completed printheads with ink  1378  and test them. A filled nozzle is shown in  FIG. 267 . 
     IJ14 
     In a preferred embodiment, there is provided an ink jet nozzle which incorporates a plunger that is surrounded by an electromagnetic device. The plunger is made from a magnetic material such that upon activation of the magnetic device, the plunger is forced towards a nozzle outlet port thereby resulting in the ejection of ink from the outlet port Upon deactivation of the electromagnet, the plunger returns to its rest position due to of a series springs constructed to return the electromagnet to its rest position. 
       FIG. 268  illustrates a sectional view through a single ink jet nozzle  1410  as constructed with a preferred embodiment The ink jet nozzle  1410  includes a nozzle chamber  1411  which is connected to a nozzle output port  1412  for the ejection of ink. The ink is ejected by means of a tapered plunger device  1414  which is made of a soft magnetic material such as nickel-ferrous material (NiFe). The plunger  1414  includes tapered end portions, e.g.  1416 , in addition to interconnecting nitride springs, e.g.  1417 . 
     An electromagnetic device is constructed around the plunger  1414  and includes outer soft magnetic material  1419  which surrounds a copper current carrying wire core  1420  with a first end of the copper coil  1420  connected to a first portion of a nickel-ferrous material and a second end of the copper coil is connected to a second portion of the nickel-ferrous material. The circuit being further formed by means of vias (not shown) connecting the current carrying wire to lower layers which can take the structure of standard CMOS fabrication layers. 
     Upon activation of the electromagnet, the tapered plunger portions  1416  are attracted to the electromagnet. The tapering allows for the forces to be resolved by means of downward movement of the overall plunger  1414 , the downward movement thereby causing the ejection of ink from ink ejection port  1412 . In due of course, the plunger will move to a stable state having its top surface substantially flush with the electromagnet Upon turning the power off, the plunger  1414  will return to its original position as a result of energy stored within that nitride springs  1417 . The nozzle chamber  1411  is refilled by inlet holes  1422  from the ink reservoir  1423 . 
     Turning now to  FIG. 269 , there is illustrated in exploded perspective the various layers used in construction of a single nozzle  1410 . The bottom layer  1430  can be formed by back etching a silicon wafer which has a boron dope epitaxial layer as the etch stop. The boron dope layer  1430  can be further individually masked and etched so as to form nozzle rim  1431  and the nozzle ejection port  1412 . Next, a silicon layer  1432  is formed. The silicon layer  1432  can be formed as part of the original wafer having the buried boron doped layer  1430 . The nozzle chamber proper can be formed substantially from high density low pressure plasma etching of the silicon layer  1432  so as to produce substantially vertical side walls thereby forming the nozzle chamber. On top of the silicon layer  1432  is formed a glass layered  1433  which can include the drive and control circuitry required for driving an array of nozzles  1410 . The drive and control circuitry can comprise standard two level metal CMOS circuitry intra-connected to form the copper coil circuit by means of vias though upper layers (not shown). Next, a nitride passivation layer  1434  is provided so as to passivate any lower glass layers, e.g.  1433 , from sacrificial etches should a sacrificial etching be used in the formation of portions of the nozzle. On top of the nitride layer  1434  is formed a first nickel-ferrous layer  1436  followed by a copper layer  1437 , and further nickel-ferrous layer  1438  which can be formed via a dual damascene process. On top of the layer  1438  is formed the final nitride spring layer  1440  with the springs being formed by means of semiconductor treatment of the nitride layer  1440  so as to release the springs in tension so as to thereby cause a slight rating of the plunger  1414 . A number of techniques not disclosed in  FIG. 269  can be used in the construction of various portions of the arrangement  1410 . For example, the nozzle chamber can be formed by using the aforementioned plasma etch and then subsequently filling the nozzle chamber with sacrificial material such as glass so as to provide a support for the plunger  1414  with the plunger  1414  being subsequently released via sacrificial etching of the sacrificial layers. 
     Further, the tapered end portions of the nickel-ferrous material can be formed so that the use of a half-tone mask having an intensity pattern corresponding to the desired bottom tapered profile of plunger  1414 . The half-tone mask can be used to half-tone a resist so that the shape is transferred to the resist and subsequently to a lower layer, such as sacrificial glass on top of which is laid the nickel-ferrous material which can be finally planarized using chemical mechanical planarization techniques. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed using the following steps: 
     1. Using a double sided polished wafer  1450  deposit 3 microns of epitaxial silicon heavily doped with boron  1430 . 
     2. Deposit 10 microns of epitaxial silicon  1432 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  1433 . This step is shown in  FIG. 271 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 270  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers  1433  down to silicon  1432  or aluminum using Mask  1 . This mask defines the nozzle chamber  1411  and the edges of the print heads chips. 
     5. Plasma etch the silicon  1432  down to the boron doped buried layer, using oxide from step  4  as a mask. This etch does not substantially etch the aluminum. This step is shown in  FIG. 272 . 
     6. Deposit 0.5 microns of silicon nitride  1434  (Si 3 N 4 ). 
     7. Deposit 12 microns of sacrificial material  1451 . 
     8. Planarize down to nitride using CMP. This fills the nozzle chamber level to the chip surface. This step is shown in  FIG. 273 . 
     9. Etch nitride  1434  and CMOS oxide layers down to second level metal using Mask  2 . This mask defines the vias for the contacts from the second level metal electrodes to the two halves of the split fixed magnetic pole. This step is shown in  FIG. 274 . 
     10. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosen due to high saturation flux density of 2 Tesla, and a low coercivity. [Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturation magnetic flux density, Nature 392, 796-798 (1998)]. 
     11. Spin on 5 microns of resist  1452 , expose with Mask  3 , and develop. This mask defines the lowest layer of the split fixed magnetic pole, and the thinnest rim of the magnetic plunger. The resist acts as an electroplating mold. This step is shown in  FIG. 275 . 
     12. Electroplate 4 microns of CoNiFe  1436 . This step is shown in  FIG. 276 . 
     13. Deposit 0.1 microns of silicon nitride (Si 3 N 4 ). 
     14. Etch the nitride layer using Mask  4 . This mask defines the contact vias from each end of the solenoid coil to the two halves of the split fixed magnetic pole. 
     15. Deposit a seed layer of copper. 
     16. Spin on 5 microns of resist  1454 , expose with Mask  5 , and develop. This mask defines the solenoid spiral coil and the spring posts, for which the resist acts as an electroplating mold. This step is shown in  FIG. 277 . 
     17. Electroplate 4 microns of copper  1437 . Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     18. Strip the resist  1454  and etch the exposed copper seed layer. This step is shown in  FIG. 278 . 
     19. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     20. Deposit 0.1 microns of silicon nitride. This layer of nitride provides corrosion protection and electrical insulation to the copper coil. 
     21. Etch the nitride layer using Mask  6 . This mask defines the regions of continuity between the lower and the middle layers of CoNiFe. 
     22. Spin on 4.5 microns of resist  1455 , expose with Mask  6 , and develop. This mask defines the middle layer of the split fixed magnetic pole, and the middle rim of the magnetic plunger. The resist forms an electroplating mold for these parts. This step is shown in  FIG. 279 . 
     23. Electroplate 4 microns of CoNiFe  1456 . The lowest layer of CoNiFe acts as the seed layer. This step is shown in  FIG. 280 . 
     24. Deposit a seed layer of CoNiFe. 
     25. Spin on 4.5 microns of resist  1457 , expose with Mask  7 , and develop. This mask defines the highest layer of the split fixed magnetic pole and the roof of the magnetic plunger. The resist forms electroplating mold for these parts. This step is shown in  FIG. 281 . 
     26. Electroplate 4 microns of CoNiFe  1458 . This step is shown in  FIG. 282 . 
     27. Deposit 1 micron of sacrificial material  1459 . 
     28. Etch the sacrificial material  1459  using Mask  8 . This mask defines the contact points of the nitride springs to the split fixed magnetic poles and the magnetic plunger. This step is shown in  FIG. 283 . 
     29. Deposit 0.1 microns of low stress silicon nitride  1460 . 
     30. Deposit 0.1 microns of high stress silicon nitride  1461 . These two layers  1460 ,  1461  of nitride form pre-stressed spring which lifts the magnetic plunger  1414  out of core space of the fixed magnetic pole. 
     31. Etch the two layers  1460 ,  1461  of nitride using Mask  9 . This mask defines the nitride spring  1440 . This step is shown in  FIG. 284 . 
     32. Mount the wafer on a glass blank  1462  and back-etch the wafer using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer  1430 . This step is shown in  FIG. 285 . 
     33. Plasma back-etch the boron doped silicon layer to a depth of (approx.) 1 micron using Mask  10 . This mask defines the nozzle rim  1431 . This step is shown in  FIG. 286 . 
     34. Plasma back-etch through the boron doped layer using Mask  11 . This mask defines the nozzle  1412 , and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank This step is shown in  FIG. 287 . 
     35. Detach the chips from the glass blank Strip all adhesive, resist, sacrificial, and exposed seed layers. The nitride spring  1440  is released in this step, lifting the magnetic plunger out of the fixed magnetic pole by 3 microns. This step is shown in  FIG. 288 . 
     36. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     37. Connect the printheads to their interconnect systems. 
     38. Hydrophobize the front surface of the printheads. 
     39. Fill the completed printheads with ink  1463  and test them. 
     A filled nozzle is shown in  FIG. 289 . 
     IJ15 
     In the present invention, a magnetically actuated ink jet print nozzle is provided for the ejection of ink from an ink chamber. The magnetically actuated ink jet utilises utilizes a linear spring to increase the travel of a shutter grill which blocks any ink pressure variations in a nozzle when in a closed position. However when the shutter is open, pressure variations are directly transmitted to the nozzle chamber and can result in the ejection of ink from the chamber. An oscillating ink pressure within an ink reservoir is used therefore to eject ink from nozzles having an open shutter grill. 
     In  FIG. 290 , there is illustrated a single nozzle mechanism  1510  of a preferred embodiment when in a closed or rest position. The arrangement  1510  includes a shutter mechanism  1511  having shutters  1512 ,  1513  which are interconnected together by part  1515  at one end for providing structural stability. The two shutters  1512 ,  1513  are interconnected at another end to a moveable bar  1516  which is further connected to a stationary positioned bar  1518  via leaf springs  1520 ,  1521 . The moveable bar  1516  can be made of a soft magnetic (NiFe) material. 
     An electromagnetic actuator is utilized to attract the moveable bar  1516  generally in the direction of arrow  1525 . The electromagnetic actuator consists of a series of soft iron claws  1524  around which is formed a copper coil wire  1526 . The electromagnetic actuators can comprise a series of actuators  1528 - 1530  interconnected via the copper coil windings. Hence, when it is desired to open the shutters  1512 - 1513  the coil  1526  is activated resulting in an attraction of bar  1516  towards the electromagnets  1528 - 1530 . The attraction results in a corresponding interaction with linear springs  1520 ,  1521  and a movement of shutters  1512 ,  1513  to an open position as illustrated in  FIG. 291 . The result of the actuation being to open portals  1532 ,  1533  into a nozzle chamber  1534  thereby allowing the ejection of ink through an ink ejection nozzle  1536 . 
     The linear springs  1520 ,  1521  are designed to increase the movement of the shutter as a result of actuation by a factor of eight. A one micron motion of the bar towards the electromagnets will result in an eight micron sideways movement. This dramatically improves the efficiency of the system, as any magnetic field falls off strongly with distance, while the linear springs have a linear relationship between motion in one axis and the other. The use of the linear springs  1520 ,  1521  therefore allows the relatively large motion required to be easily achieved. 
     The surface of the wafer is directly immersed in an ink reservoir or in relatively large ink channels. An ultrasonic transducer (for example, a piezoelectric transducer), not shown, is positioned in the reservoir. The transducer oscillates the ink pressure at approximately 100 KHz. The ink pressure oscillation is sufficient that ink drops would be ejected from the nozzle when it is not blocked by the shutters  1512 ,  1513 . When data signals distributed on the print head indicate that a particular nozzle is to eject a drop of ink, the drive transistor for that nozzle is turned on. This energises energizes the actuators  1528 - 1530 , which moves the shutters  1512 ,  1513  so that they are not blocking the ink chamber. The peak of the ink pressure variation causes the ink to be squirted out of the nozzle. As the ink pressure goes negative, ink is drawn back into the nozzle, causing drop break-off. The shutters  1512 ,  1513  are kept open until the nozzle is refilled on the next positive pressure cycle. They are then shut to prevent the ink from being withdrawn from the nozzle on the next negative pressure cycle. 
     Each drop ejection takes two ink pressure cycles. Preferably half of the nozzles should eject drops in one phase, and the other half of the nozzles should eject drops in the other phase. This minimizes the pressure variations which occur due to a large number of nozzles being actuated. 
     The amplitude of the ultrasonic transducer can be further altered in response to the viscosity of the ink (which is typically affected by temperature), and the number of drops which are to be ejected in a current cycle. This amplitude adjustment can be used to maintain consistent drop size in varying environmental conditions. 
     In  FIG. 292 , there is illustrated a section taken through the line I-I of  FIG. 291  so as to illustrate the nozzle chamber  1534  which can be formed utilizing an anisotropic crystallographic etch of the silicon substrate. The etch access through the substrate can be via the slots  1532 ,  1533  ( FIG. 290 ) in the shutter grill. 
     The device is manufactured on &lt;100&gt; silicon with a buried boron etch stop layer  1540 , but rotated 45° in relation to the &lt;010&gt; and &lt;001&gt; planes. Therefore, the &lt;111&gt; planes which stop the crystallographic etch of nozzle chamber form a 45° rectangle which superscribes the slots in the fixed grill. This etch will proceed quite slowly, due to limited access of etchant to the silicon. However, the etch can be performed at the same time as the bulk silicon etch which thins the bottom of the wafer. 
     In  FIG. 293 , there is illustrated an exploded perspective view of the various layers formed in the construction of an ink jet print head  1510 . The layers include the boron doped layer  1540  which acts as an etch stop and can be derived from back etching a silicon wafer having a buried epitaxial layer as is well known in Micro Electro Mechanical Systems (MEMS). The nozzle chamber side walls are formed from a crystallographic graphic etch of the wafer  1541  with the boron doped layer  1540  being utilized as an etch stop. 
     A subsequent layer  1542  is constructed for the provision of drive transistors and printer logic and can comprise a two level metal CMOS processing layer  1542 . The CMOS processing layer is covered by a nitride layer  1543  which includes portions  1544  which cover and protect the side walls of the CMOS layer  1542 . The copper layer  1545  can be constructed utilizing a dual damascene process. Finally, a soft metal (NiFe) layer  1546  is provided for forming the rest of the actuator. Each of the layers  1544 ,  1545  are separately coated by a nitride insulating layer (not shown) which provides passivation and insulation and can be a standard 0.1 micron process. 
     The arrangement of  FIG. 290  therefore provides an ink jet nozzle having a high speed firing rate (approximately 50 KHz) which is suitable for fabrication in arrays of ink jet nozzles, one along side another, for fabrication as a monolithic page width print head. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  1550  deposit 3 microns of epitaxial silicon heavily doped with boron  1540 . 
     2. Deposit 10 microns of epitaxial silicon  1541 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process. Relevant features of the wafer  1550  at this step are shown in  FIG. 295 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 294  is a key to representations of various materials in these manufacturing diagrams, and those of other cross-referenced, ink jet configurations. 
     4. Etch the CMOS oxide layers  1541  down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber  1534 , and the edges of the print head chips. This step is shown in  FIG. 296 . 
     5. Crystallographically etch the exposed silicon using, for example, KOH or EDP (ethylenediamine pyrocatechol). This etch stops on &lt;111&gt; crystallographic planes, and on the boron doped silicon buried layer. This step is shown in  FIG. 297 . 
     6. Deposit 12 microns of sacrificial material  1551 . Planarize down to oxide using CMP. The sacrificial material temporarily fills the nozzle cavity. This step is shown in  FIG. 298 . 
     7. Deposit 0.5 microns of silicon nitride (Si 3 N 4 )  1552 . 
     8. Etch nitride  1552  and oxide down to aluminum  1542  or sacrificial material  1551  using Mask  3 . This mask defines the contact vias from the aluminum electrodes to the solenoid, as well as the fixed grill over the nozzle cavity. This step is shown in  FIG. 299 . 
     9. Deposit a seed layer of copper. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     10. Spin on 2 microns of resist  1553 , expose with Mask  4 , and develop. This mask defines the lower side of the solenoid square helix. The resist acts as an electroplating mold. This step is shown in  FIG. 300 . 
     11. Electroplate 1 micron of copper  1554 . This step is shown in  FIG. 301 . 
     12. Strip the resist  1553  and etch the exposed copper seed layer. This step is shown in  FIG. 302 . 
     13. Deposit 0.1 microns of silicon nitride. 
     14. Deposit 0.5 microns of sacrificial material  1556 . 
     15. Etch the sacrificial material  1556  down to nitride  1552  using Mask  5 . This mask defines the solenoid, the fixed magnetic pole, and the linear spring anchor. This step is shown in  FIG. 303 . 
     16. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosen due to a high saturation flux density of 2 Tesla, and a low coercivity. [Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturation magnetic flux density, Nature 392, 796-798 (1998)]. 
     17. Spin on 3 microns of resist  1557 , expose with Mask  6 , and develop. This mask defines all of the soft magnetic parts, being the U shaped fixed magnetic poles, the linear spring, the linear spring anchor, and the shutter grill. The resist acts as the electroplating mold. This step is shown in  FIG. 304 . 
     18. Electroplate 2 microns of CoNiFe  1558 . This step is shown in  FIG. 305 . 
     19. Strip the resist  1557  and etch the exposed seed layer. This step is shown in  FIG. 306 . 
     20. Deposit 0.1 microns of silicon nitride (Si 3 N 4 ). 
     21. Spin on 2 microns of resist  1559 , expose with Mask  7 , and develop. This mask defines the solenoid vertical wire segments, for which the resist acts as an electroplating mold. This step is shown in  FIG. 307 . 
     22. Etch the nitride down to copper using the Mask  7  resist. 
     23. Electroplate 2 microns of copper  1560 . This step is shown in  FIG. 308 . 
     24. Deposit a seed layer of copper. 
     25. Spin on 2 microns of resist  1561 , expose with Mask  8 , and develop. This mask defines the upper side of the solenoid square helix. The resist acts as an electroplating mold. This step is shown in  FIG. 309 . 
     26. Electroplate 1 micron of copper  1562 . This step is shown in  FIG. 310 . 
     27. Strip the resist  1559  and  1561  and etch the exposed copper seed layer, and strip the newly exposed resist. This step is shown in  FIG. 311 . 
     28. Deposit 0.1 microns of conformal silicon nitride as a corrosion barrier. 
     29. Open the bond pads using Mask  9 . 
     30. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     31. Mount the wafer on a glass blank  1563  and back-etch the wafer  1550  using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer  1540 . This step is shown in  FIG. 312 . 
     32. Plasma back-etch the boron doped silicon layer  1540  to a depth of 1 micron using Mask  9 . This mask defines the nozzle rim  1564 . This step is shown in  FIG. 313 . 
     33. Plasma back-etch through the boron doped layer using Mask  10 . This mask defines the nozzle  1536 , and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in  FIG. 314 . 
     34. Detach the chips from the glass blank  1563 . Strip all adhesive, resist, sacrificial, and exposed seed layers. 
     This step is shown in  FIG. 315 . 
     35. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. The package also includes a piezoelectric actuator attached to the rear of the ink channels. The piezoelectric actuator provides the oscillating ink pressure required for the ink jet operation. 
     36. Connect the print heads to their interconnect systems. 
     37. Hydrophobize the front surface of the print heads. 
     38. Fill the completed print heads with ink  1565  and test them. A filled nozzle is shown in  FIG. 316 . 
     IJ16 
     A preferred embodiment uses a Lorenz force on a current carrying wire in a magnetic field to actuate a diaphragm for the injection of ink from a nozzle chamber via a nozzle hole. The magnetic field is static and is provided by a permanent magnetic yoke around the nozzles of an ink jet head. 
     Referring initially to  FIG. 317 , there is illustrated a single ink jet nozzle chamber apparatus  1610  as constructed in accordance with a preferred embodiment. Each ink jet nozzle  1610  includes a diaphragm  1611  of a corrugated form which is suspended over a nozzle chamber having a ink port  1613  for the injection of ink. The diaphragm  1611  is constructed from a number of layers including a plane copper coil layer which consists of a large number of copper coils which form a circuit for the flow of electric current across the diaphragm  1611 . The electric current in the wires of the diaphragm coil section  1611  all flowing in the same direction.  FIG. 324  is a perspective view of the current circuit utilized in the construction of a single ink jet nozzle, illustrating the corrugated structure of the traces in the diaphragm  1611  of  FIG. 317 . A permanent magnetic yoke (not shown) is arranged so that the magnetic field β,  1616 , is in the plane of the chip&#39;s surface, perpendicular to the direction of current flow across the diaphragm coil  1611 . 
     In  FIG. 318 , there is illustrated a sectional view of the ink jet nozzle  1610  taken along the line A-A 1  of  FIG. 317  when the diaphragm  1611  has been activated by current flowing through coil wires  1614 . The diaphragm  1611  is forced generally in the direction of nozzle  1613  thereby resulting in ink within chamber  1618  being ejected out of port  1613 . The diaphragm  1611  and chamber  1618  are connected to an ink reservoir  1619  which, after the ejection of ink via port  1613 , results in a refilling of chamber  1618  from ink reservoir  1619 . 
     The movement of the diaphragm  1611  results from a Lorenz interaction between the coil current and the magnetic field. 
     The diaphragm  1611  is corrugated so that the diaphragm motion occurs as an elastic bending motion. This is important as a flat diaphragm may be prevented from flexing by tensile stress. 
     When data signals distributed on the printhead indicate that a particular nozzle is to eject a drop of ink, the drive transistor for that nozzle is turned on. This energizes the coil  1614 , causing elastic deformation of the diaphragm  1611  downwards, ejecting ink. After approximately 3 μs, the coil current is turned off, and the diaphragm  1611  returns to its quiescent position The diaphragm return ‘sucks’ some of the ink back into the nozzle, causing the ink ligament connecting the ink drop to the ink in the nozzle to thin. The forward velocity of the drop and backward velocity of the ink in the chamber  1618  are resolved by the ink drop breaking off from the ink in the nozzle. The ink drop then continues towards the recording medium. Ink refill of the nozzle chamber  1618  is via the two slots  1622 ,  1623  at either side of the diaphragm. The ink refill is caused by the surface tension of the ink meniscus at the nozzle. 
     Turning to  FIG. 319 , the corrugated diaphragm can be formed by depositing a resist layer  1630  on top of a sacrificial glass layer  1631 . The resist layer  1630  is exposed using a mask  1632  having a halftone pattern delineating the corrugations. 
     After development, as is illustrated in  FIG. 320 , the resist  1630  contains the corrugation pattern. The resist layer  1630  and the sacrificial glass layer are then etched using an etchant that erodes the resist  1630  at substantially the same rate as the sacrificial glass  1631 . This transfers the corrugated pattern into the sacrificial glass layer  1631  as illustrated in  FIG. 321 . As illustrated in  FIG. 322 , subsequently, a nitride passivation layer  1634  is deposited followed a copper layer  1635  which is patterned using a coil mask. A further nitride passivation layer  1636  follows on top of the copper layer  1635 . Slots  1622 ,  1623  in the nitride layer at the side of the diaphragm can be etched ( FIG. 317 ) and subsequently, the sacrificial glass layer can be etched away leaving the corrugated diaphragm. 
     In  FIG. 323 , there is illustrated an exploded perspective view of the various layers of an ink jet nozzle  1610  which is constructed on a silicon wafer having a buried boron doped epitaxial layer  1640  which is back etched in a final processing step, including the etching of ink port  1613 . The silicon substrate  1641 , as will be discussed below, is an anisotropically crystallographically etched so as to form the nozzle chamber structure. On top of the silicon substrate layer  1641  is a CMOS layer  1642  which can comprise standard CMOS processing to form two level metal drive and control circuitry. On top of the CMOS layer  1642  is a first passivation layer  1643  which can comprise silicon nitride which protects the lower layers from any subsequent etching processes. On top of this layer is formed the copper layer  1645  having through holes e.g.  1646  to the CMOS layer  1642  for the supply of current. On top of the copper layer  1645  is a second nitrate passivation layer  1647  which provides for protection of the copper layer from ink and provides insulation. 
     The nozzle  1610  can be formed as part of an array of nozzles formed on a single wafer. After construction, the wafer creating nozzles  1610  can be bonded to a second ink supply wafer having ink channels for the supply of ink such that the nozzle  1610  is effectively supplied with an ink reservoir on one side and ejects ink through the hole  1613  onto print media or the like on demand as required. 
     The nozzle chamber  1618  is formed using an anisotropic crystallographic etch of the silicon substrate. Etchant access to the substrate is via the slots  1622 ,  1623  at the sides of the diaphragm. The device is manufactured on &lt;100&gt; silicon (with a buried boron etch stop layer), but rotated 45° in relation to the &lt;010&gt; and &lt;001&gt; planes. Therefore, the &lt;111&gt; planes which stop the crystallographic etch of the nozzle chamber form a 45° rectangle which superscribes the slot in the nitride layer. This etch will proceed quite slowly, due to limited access of etchant to the silicon. However, the etch can be performed at the same time as the bulk silicon etch which thins the wafer. The drop firing rate is around 7 KHz. The ink jet head is suitable for fabrication as a monolithic page wide print head. The illustration shows a single nozzle of a 1600 dpi print head in ‘down shooter’ configuration. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  1650  deposit 3 microns of epitaxial silicon heavily doped with boron  1640 . 
     2. Deposit 10 microns of epitaxial silicon  1641 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  1642 . This step is shown in  FIG. 326 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 325  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber, and the edges of the print heads chips. This step is shown in  FIG. 327 . 
     5. Crystallographically etch the exposed silicon using, for example, KOH or EDP (ethylenediamine pyrocatechol). This etch stops on &lt;111&gt; crystallographic planes  1651 , and on the boron doped silicon buried layer. This step is shown in  FIG. 328 . 
     6. Deposit 12 microns of sacrificial material (polyimide)  1652 . Planarize down to oxide using CMP. The sacrificial material temporarily fills the nozzle cavity. This step is shown in  FIG. 329 . 
     7. Deposit 1 micron of (sacrificial) photosensitive polyimide. 
     8. Expose and develop the photosensitive polyimide using Mask  2 . This mask is a gray-scale mask which defines the concertina ridges of the flexible membrane containing the central part of the solenoid. The result of the etch is a series of triangular ridges  1653  across the whole length of the ink pushing membrane. This step is shown in  FIG. 330 . 
     9. Deposit 0.1 microns of PECVD silicon nitride (Si 3 N 4 ) (Not shown). 
     10. Etch the nitride layer using Mask  3 . This mask defines the contact vias  1654  from the solenoid coil to the second-level metal contacts. 
     11. Deposit a seed layer of copper. 
     12. on 2 microns of resist  1656 , expose with Mask  4 , and develop. This mask defines the coil of the solenoid. The resist acts as an electroplating mold. This step is shown in  FIG. 331 . 
     13. Electroplate 1 micron of copper  1655 . Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     14. Strip the resist and etch the exposed copper seed layer  1657 . This step is shown in  FIG. 332 . 
     15. Deposit 0.1 microns of silicon nitride (Si 3 N 4 ) (Not shown). 
     16. Etch the nitride layer using Mask  5 . This mask defines the edges of the ink pushing membrane and the bond pads. 
     17. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     18. Mount the wafer on a glass blank  1658  and back-etch the wafer using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in  FIG. 333 . 
     19. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask  6 . This mask defines the nozzle rim  1659 . This step is shown in  FIG. 334 . 
     20. Plasma back-etch through the boron doped layer using Mask  7 . This mask defines the nozzle  1613 , and the edge of the chips. At this stage, the chips are still mounted on the glass blank. This step is shown in  FIG. 335 . 
     21. Strip the adhesive layer to detach the chips from the glass blank. Etch the sacrificial layer. This process completely separates the chips. This step is shown in  FIG. 336 . 
     22. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     23. Connect the printheads to their interconnect systems. 
     24. Hydrophobize the front surface of the printheads. 
     25. Fill with ink  1660 , apply a strong magnetic field in the plane of the chip surface, and test the completed printheads. A filled nozzle is shown in  FIG. 337 . 
     IJ17 
     In a preferred embodiment, an oscillating ink reservoir pressure is used to eject ink from ejection nozzles. Each nozzle has an associated shutter which normally blocks the nozzle. The shutter is moved away from the nozzle by an actuator whenever an ink drop is to be fired. 
     Turning initially to  FIG. 338 , there is illustrated in exploded perspective a single ink jet nozzle  1710  as constructed in accordance with the principles of the present invention. The exploded perspective illustrates a single ink jet nozzle  1710 . Ideally, the nozzles are formed as an array at a time on a bottom silicon wafer  1712 . The silicon wafer  1712  is processed so as to have two level metal CMOS circuitry which includes metal layers and glass layers  1713  and which are planarized after construction. The CMOS metal layer has a reduced aperture  1714  for the access of ink from the back of silicon wafer  1712  via the larger radius portal  1715 . 
     A bottom nitride layer  1716  is constructed on top of the CMOS layer  1713  so as to cover, protect and passivate the CMOS layer  1713  from subsequent etching processes. Subsequently, there is provided a copper heater layer  1718  which is sandwiched between two polytetrafluoroethylene (PTFE) layers  1719 ,  1720 . The copper layer  1718  is connected to lower CMOS layer  1713  through vias  1725 ,  1726 . The copper layer  1718  and PTFE layers  1719 ,  1720  are encapsulated within nitride borders e.g.  1728  and nitride top layer  1729  which includes an ink ejection portal  1730  in addition to a number of sacrificial etched access holes  1732  which are of a smaller dimension than the ejection portal  1730  and are provided for allowing access of a etchant to lower sacrificial layers thereby allowing the use of a etchant in the construction of layers,  1718 ,  1719 ,  1720  and  1728 . 
     Turning now to  FIG. 339 , there is shown a cut-out perspective view of a fully constructed ink jet nozzle  1710 . The ink jet nozzle uses an oscillating ink pressure to eject ink from ejection port  1730 . Each nozzle has an associated shutter  1731  which normally blocks it. The shutter  1731  is moved away from the ejection port  1730  opening by an actuator  1735  whenever an ink drop is to be fired. 
     The nozzles  1730  are in connected to ink chambers which contain the actuators  1735 . These chambers are connected to ink supply channels  1736  which are etched through the silicon wafer. The ink supply channels  1736  are substantially wider than the nozzles  1730 , to reduce the fluidic resistance to the ink pressure wave. The ink channels  1736  are connected to an ink reservoir. An ultrasonic transducer (for example, a piezoelectric transducer) is positioned in the reservoir. The transducer oscillates the ink pressure at approximately 100 KHz. The ink pressure oscillation is sufficient that ink drops would be ejected from the nozzle were it not blocked by the shutter  1731 . 
     The shutters are moved by a thermoelastic actuator  1735 . The actuators are formed as a coiled serpentine copper heater  1723  embedded in polytetrafluoroethylene (PTFE)  1719 ,  1720 . PTFE has a very high coefficient of thermal expansion (approximately 770×10 −6 ). The current return trace  1722  from the heater  1723  is also embedded in the PTFE actuator  1735 , the current return trace  1722  is made wider than the heater trace  1723  and is not serpentine. Therefore, it does not heat the PTFE as much as the serpentine heater  1723  does. The serpentine heater  1723  is positioned along the inside edge of the PTFE coil, and the return trace is positioned on the outside edge. When actuated, the inside edge becomes hotter than the outside edge, and expands more. This results in the actuator  1735  uncoiling. 
     The heater layer  1723  is etched in a serpentine manner both to increase its resistance, and to reduce its effective tensile strength along the length of the actuator. This is so that the low thermal expansion of the copper does not prevent the actuator from expanding according to the high thermal expansion characteristics of the PTFE. 
     By varying the power applied to the actuator  1735 , the shutter  1731  can be positioned between the fully on and fully off positions. This may be used to vary the volume of the ejected drop. Drop volume control may be used either to implement a degree of continuous tone operation, to regulate the drop volume, or both. 
     When data signals distributed on the printhead indicate that a particular nozzle is turned on, the actuator  1735  is energized, which moves the shutter  1731  so that it is not blocking the ink chamber. The peak of the ink pressure variation causes the ink to be squirted out of the nozzle  1730 . As the ink pressure goes negative, ink is drawn back into the nozzle, causing drop break-off. The shutter  1731  is kept open until the nozzle is refilled on the next positive pressure cycle. It is then shut to prevent the ink from being withdrawn from the nozzle on the next negative pressure cycle. 
     Each drop ejection takes two ink pressure cycles. Preferably half of the nozzles  1710  should eject drops in one phase, and the other half of the nozzles should eject drops in the other phase. This minimises the pressure variations which occur due to a large number of nozzles being actuated. 
     The amplitude of the ultrasonic transducer can be altered in response to the viscosity of the ink (which is typically affected by temperature), and the number of drops which are to be ejected in the current cycle. This amplitude adjustment can be used to maintain consistent drop size in varying environmental conditions. 
     The drop firing rate can be around 50 KHz. The ink jet head is suitable for fabrication as a monolithic page wide printhead.  FIG. 339  shows a single nozzle of a 1600 dpi printhead in “up shooter” configuration. 
     Return again to  FIG. 338 , one method of construction of the ink jet print nozzles  1710  will now be described. Starting with the bottom wafer layer  1712 , the wafer is processed so as to add CMOS layers  1713  with an aperture  1714  being inserted. The nitride layer  1716  is laid down on top of the CMOS layers so as to protect them from subsequent etchings. 
     A thin sacrificial glass layer is then laid down on top of nitride layers  1716  followed by a first PTFE layer  1719 , the copper layer  1718  and a second PTFE layer  1720 . Then a sacrificial glass layer is formed on top of the PTFE layer and etched to a depth of a few microns to form the nitride border regions  1728 . Next the top layer  1729  is laid down over the sacrificial layer using the mask for forming the various holes including the processing step of forming the rim  1740  on nozzle  1730 . The sacrificial glass is then dissolved away and the channel  1715  formed through the wafer by means of utilisation of high density low pressure plasma etching such as that available from Surface Technology Systems. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed using the following steps: 
     1. Using a double sided polished wafer  1712 , Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  1713 . The wafer is passivated with 0.1 microns of silicon nitride  1716 . This step is shown in  FIG. 341 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 340  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch nitride and oxide down to silicon using Mask  1 . This mask defines the nozzle inlet below the shutter. This step is shown in  FIG. 342 . 
     3. Deposit 3 microns of sacrificial material  1750  (e.g. aluminum or photosensitive polyimide) 
     4. Planarize the sacrificial layer to a thickness of 1 micron over nitride. This step is shown in  FIG. 343 . 
     5. Etch the sacrificial layer using Mask  2 . This mask defines the actuator anchor point  1751 . This step is shown in  FIG. 344 . 
     6. Deposit 1 micron of PTFE  1752 . 
     7. Etch the PTFE, nitride, and oxide down to second level metal using Mask  3 . This mask defines the heater vias  1725 ,  1726 . This step is shown in  FIG. 345 . 
     8. Deposit the heater  1753 , which is a 1 micron layer of a conductor with a low Young&#39;s modulus, for example aluminum or gold. 
     9. Pattern the conductor using Mask  4 . This step is shown in  FIG. 346 . 
     10. Deposit 1 micron of PTFE  1754 . 
     11. Etch the PTFE down to the sacrificial layer using Mask  5 . This mask defines the actuator and shutter This step is shown in  FIG. 347 . 
     12. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     13. Deposit 3 microns of sacrificial material  1755 . Planarize using CMP 
     14. Etch the sacrificial material using Mask  6 . This mask defines the nozzle chamber wall  1728 . This step is shown in  FIG. 348 . 
     15. Deposit 3 microns of PECVD glass  1756 . 
     16. Etch to a depth of (approx.) 1 micron using Mask  7 . This mask defines the nozzle rim  1740 . This step is shown in  FIG. 349 . 
     17. Etch down to the sacrificial layer using Mask  6 . This mask defines the roof of the nozzle chamber, the nozzle  1730 , and the sacrificial etch access holes  1732 . This step is shown in  FIG. 350 . 
     18. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  7 . This mask defines the ink inlets  1715  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 351 . 
     19. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch This step is shown in  FIG. 352 . 
     20. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. The package also includes a piezoelectric actuator attached to the rear of the ink channels. The piezoelectric actuator provides the oscillating ink pressure required for the ink jet operation. 
     21. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     22. Hydrophobize the front surface of the printheads. 
     23. Fill the completed printheads with ink  1757  and test them. A filled nozzle is shown in  FIG. 353 . 
     IJ18 
     In a preferred embodiment, an inkjet printhead includes a shutter mechanism which interconnects the nozzle chamber with an ink supply reservoir, the reservoir being under an oscillating ink pressure. Hence, when the shutter is open, ink is forced through the shutter mechanism and out of the nozzle chamber. Closing the shutter mechanism results in the nozzle chamber remaining in a stable state and not ejecting any ink from the chamber. 
     Turning initially to  FIG. 354 , there is illustrated a single nozzle chamber  1810  as constructed in accordance with the principles of a preferred embodiment. The nozzle chamber  1810  can be constructed on a silicon wafer  1811 , having an electrical circuitry layer  1812  which contains the control circuitry and drive transistors. The layer  1812  can comprise a two level metal CMOS layer or another suitable form of semi conductor processing layer. On top of the layer  1812  is deposited a nitride passivation layer  1813 .  FIG. 354  illustrates the shutter in a closed state while  FIG. 355  illustrates the shutter when in an open state. 
       FIG. 356  illustrates an exploded perspective view of the various layers of the inkjet nozzle when the shutters are in an open state as illustrated in  FIG. 355 . The nitride layer  1813  includes a series of slots e.g.  1815 ,  1816  and  1817  which allow for the flow of ink from an ink channel  1819  etched through the silicon wafer  1811 . The nitride layer  1813  also preferably includes bottom portion  1820  which acts to passivate those exposed portions of lower layer  1812  which may be attacked in any sacrificial etch utilized in the construction of the nozzle chamber  1810 . The next layers include a polytetrafluoroethylene (PTFE) layer  1822  having an internal copper structure  1823 . The PTFE layers  1822  and internal copper portions  1823  comprise the operational core of the nozzle chamber  1810 . The copper layer  1823  includes copper end posts, e.g.  1825 - 1827 , interconnecting serpentine copper portions  1830 ,  1831 . The serpentine copper portions  1830 ,  1831  are designed for greatly expanding like a concertina upon heating. The heating circuit is provided by means of interconnecting vias (not shown) between the end portions, e.g.  1825 - 1827 , and lower level CMOS circuitry at CMOS level  1812 . Hence when it is desired to open the shutter, a current is passed through the two portions  1830 ,  1831  thereby heating up portions  1834 ,  1835  of the PTFE layer  1822 . The PTFE layer has a very high co-efficient of the thermal expansion (approximately 770×10 −6 ) and hence expands more rapidly than the copper portions  1830 ,  1831 . However, the copper portions  1830 ,  1831  are constructed in a serpentine manner which allows the serpentine structure to expand like a concertina to accommodate the expansion of the PTFE layer. This results in a buckling of the PTFE layer portions  1834 ,  1835  which in turn results in a movement of the shutter portions e.g.  1837  generally in the direction  1838 . The movement of the shutter  1837  in direction  1838  in turn results in an opening of the nozzle chamber  1810  to the ink supply. As stated previously, in  FIG. 354  there is illustrated the shutter in a closed position whereas in  FIG. 355 , there is illustrated an open shutter after activation by means of passing a current through the two copper portions  1830 ,  1831 . The portions  1830 ,  1831  are positioned along one side within the portions  1833 ,  1835  so as to ensure buckling in the correct direction. 
     Nitride layers, including side walls  1840  and top portion  1841 , are constructed to form the rest of a nozzle chamber  1810 . The top surface includes an ink ejection nozzle  1842  in addition to a number of smaller nozzles  1843  which are provided for sacrificial etching purposes. The nozzles  1843  are much smaller than the nozzle  1842  such that, during operation, surface tension effects restrict any ejection of ink from the nozzles  1843 . 
     In operation, the ink supply channel  1819  is driven with an oscillating ink pressure. The oscillating ink pressure can be induced by means of driving a piezoelectric actuator in an ink chamber. When it is desired to eject a drop from the nozzle  1842 , the shutter is opened forcing the drop of ink out of the nozzle  1842  during the next high pressure cycle of the oscillating ink pressure. The ejected ink is separated from the main body of ink within the nozzle chamber  1810  when the pressure is reduced. The separated ink continues to the paper. Preferably, the shutter is kept open so that the ink channel may refill during the next high pressure cycle. Afterwards it is rapidly shut so that the nozzle chamber remains full during subsequent low cycles of the oscillating ink pressure. The nozzle chamber is then ready for subsequent refiring on demand. 
     The inkjet nozzle chamber  1810  can be constructed as part of an array of inkjet nozzles through MEMS depositing of the various layers utilizing the required masks, starting with a CMOS layer  1812  on top of which the nitride layer  1813  is deposited having the requisite slots. A sacrificial glass layer can then be deposited followed by a bottom portion of the PTFE layer  1822 , followed by the copper layer  1823  with the lower layers having suitable vias for interconnecting with the copper layer. Next, an upper PTFE layer is deposited so as to encase to the copper layer  1823  within the PTFE layer  1822 . A further sacrificial glass layer is then deposited and etched, before a nitride layer is deposited forming side walls  1840  and nozzle plate  1841 . The nozzle plate  1841  is etched to have suitable nozzle hole  1842  and sacrificial etching nozzles  1843  with the plate also being etched to form a rim around the nozzle hole  1842 . Subsequently, the sacrificial glass layers can be etched away, thereby releasing the structure of the actuator of the PTFE and copper layers. Additionally, the wafer can be through etched utilizing a high density low pressure plasma etching process such as that available from Surface Technology Systems. 
     As noted previously many nozzles can be formed on a single wafer with the nozzles grouped into their desired width heads and the wafer diced in accordance with requirements. The diced printheads can then be interconnected to a printhead ink supply reservoir on the back portion thereof, for operation, producing a drop on demand ink jet printer. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  1811 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process. Relevant features of the wafer at this step are shown in  FIG. 358 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 357  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch the oxide layers down to silicon using Mask  1 . This mask defines the lower fixed grill  1850 . This step is shown in  FIG. 359 . 
     3. Deposit 3 microns of sacrificial material  1851  (e.g. aluminum or photosensitive polyimide) 
     4. Planarize the sacrificial layer to a thickness of 0.5 micron over glass. This step is shown in  FIG. 360 . 
     5. Etch the sacrificial layer using Mask  2 . This mask defines the nozzle chamber walls and the actuator anchor points. This step is shown in  FIG. 361 . 
     6. Deposit 1 micron of PTFE  1852 . 
     7. Etch the PTFE and oxide down to second level metal using Mask  3 . This mask defines the heater vias. This step is shown in  FIG. 362 . 
     8. Deposit 1 micron of a conductor with a low Young&#39;s modulus  1853 , for example aluminum or gold. 
     9. Pattern the conductor using Mask  4 . This step is shown in  FIG. 363 . 
     10. Deposit 1 micron of PTFE  1855 . 
     11. Etch the PTFE down to the sacrificial layer using Mask  5 . This mask defines the actuator and shutter This step is shown in  FIG. 364 . 
     12. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     13. Deposit 6 microns of sacrificial material  1856 . 
     14. Etch the sacrificial material using Mask  6 . This mask defines the nozzle chamber wall  1840 . This step is shown in  FIG. 365 . 
     15. Deposit 3 microns of PECVD glass  1857 . 
     16. Etch to a depth of (approx.) 1 micron using Mask  7 . This mask defines the nozzle rim  1844 . This step is shown in  FIG. 366 . 
     17. Etch down to the sacrificial layer using Mask  6 . This mask defines the roof  1841  of the nozzle chamber, the nozzle  1842 , and the sacrificial etch access holes  1843 . This step is shown in  FIG. 367 . 
     18. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  7 . This mask defines the ink inlets  1819  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 368 . 
     19. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 369 . 
     20. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. The package also includes a piezoelectric actuator attached to the rear of the ink channels. The piezoelectric actuator provides the oscillating ink pressure required for the ink jet operation. 
     21. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     22. Hydrophobize the front surface of the printheads. 
     23. Fill the completed printheads with ink  1860  and test them. A filled nozzle is shown in  FIG. 370 . 
     IJ19 
     A preferred embodiment utilises an ink reservoir with oscillating ink pressure and a shutter activated by a thermal actuator to eject drops of ink. 
     Turning now to  FIG. 371 , there is illustrated two ink nozzle arrangements  1920 ,  1921  as constructed in accordance with a preferred embodiment The ink nozzle arrangement  1920  is shown in an open position with the ink nozzle arrangement  1921  shown in a closed position. The ink nozzle arrangement of  FIG. 371  can be constructed as part of a large array of nozzles or print heads on a silicon wafer utilizing micro-electro mechanical technologies (MEMS). 
     In  FIG. 371 , each of the ink nozzle arrangements  1920 ,  1921  covers an ink nozzle e.g.  1922  from which ejection of ink occurs when the ink nozzle arrangement is in an open state and the pressure wave is at a maximum. 
     Each of the ink nozzle arrangements of  FIG. 371  utilizes a thermocouple actuator device  1909  having two arms. The ink nozzle arrangement  1920  utilizes arms  1924 ,  1925  and the ink nozzle arrangement  1921  uses thermocouple arms  1926 ,  1927 . The thermocouple arms  1924 ,  1925  are responsible for movement of a grated shutter device within a shutter cage  1929 . 
     Referring now to  FIG. 372 , there is illustrated the thermocouple arms  1924 ,  1925  and shutter  1930  of  FIG. 371  without the cage. The shutter  1930  includes a number of apertures  1931  for the passage of ink through the shutter  1930  when the shutter is in an open state. The thermocouple arms  1924 ,  1925  are responsible for movement of the shutter  1930  upon activation of the thermocouple by means of an electric current flowing through bonding pads  1932 ,  1933  ( FIG. 371 ). The thermal actuator of  FIG. 372  operates along similar principles to that disclosed in the aforementioned proceedings by the authors J. Robert Reid, Victor M. Bright and John. H. Comtois with a number of significant differences in operation which will now be discussed. The arm  1924  can comprise an inner core  1940  of poly-silicon surrounded by an outer jacket  1941  of thermally insulating material. The cross-section of the arm  1924  is illustrated in  FIG. 372  and includes the inner core  1940  and the outer jacket  1941 . 
     A current is passed through the two arms  1924 ,  1925  via bonding pads  1932 ,  1933 . The arm  1924  includes the inner core  1940  which is an inner resistive element, preferably comprising polysilicon or the like which heats up upon a current being passed through it The thermal jacket  1941  is provided to isolate the inner core  1940  from the ink chamber  1911  in which the arms  1924 ,  1925  are immersed 
     It should be noted that the arm  1924  contains a thermal jacket  1941  whereas the arm  1925  does not include a thermal jacket Hence, the arm  1925  will be generally cooler than the arm  1924  and undergoes a different rate of thermal expansion. The two arms act together to form a thermal actuator. The thermocouple comprising arms  1924 ,  1925  results in movement of the shutter  1930  generally in the direction  1934  upon a current being passed through the two arms. Importantly, the arm  1925  includes a thinned portion  1936  (in  FIG. 371 ) which amplifies the radial movement of shutter  1930  around a central axis near the bonding pads  1932 ,  1933  (in  FIG. 371 ). This results in a “magnification” of the rotational effects of activation of the thermocouple, resulting in an increased movement of the shutter  1930 . The thermocouples  1924 ,  1925  can be activated to move the shutter  1930  from the closed position as illustrated generally at  1921  in  FIG. 371  to an open position as illustrated at  1920  in  FIG. 371 . 
     Returning now to  FIG. 371  a second thermocouple actuator  1950  is also provided having first and second arms  1951 ,  1952 . The actuator  1950  operates on the same physical principles as the arm associated with the shutter system  1930 . The actuator  1950  is designed to be operated so as to lock the shutter  1930  in an open or closed position. The actuator  1950  locking the shutter  1930  in an open position is illustrated in  FIG. 371 . When in a closed position, the arm  1950  locks the shutter by means of engagement of knob with a cavity on shutter  1930  (not shown). After a short period, the shutter  1930  is deactivated, and the hot arm  1924  ( FIG. 372 ) of the actuator  1909  begins to cool. 
     An example timing diagram of operation of each ink nozzle arrangement will now be described. In  FIG. 373  there is illustrated generally at  1955  a first pressure plot which illustrates the pressure fluctuation around an ambient pressure within the ink chamber ( 1911  of  FIG. 372 ) as a result of the driving of a piezoelectric actuator in a substantially sinusoidal manner. The pressure fluctuation  1970  is also substantially sinusoidal in nature and the printing cycle is divided into four phases being a drop formation phase  1971 , a drop separation phase  1972 , a drop refill phase  1973  and a drop settling phase  1974 . 
     Also shown in  FIG. 373  are clock timing diagrams  1956  and  1957 . The first diagram  1956  illustrates the control pulses received by the shutter thermal actuator of a single ink nozzle so as to open and close the shutter. The second clock timing diagram  1957  is directed to the operation of the second thermal actuator (eg.  1950  of  FIG. 371 ). 
     At the start of the drop formation phase  1971  when the pressure  1970  within the ink chamber is going from a negative pressure to a positive pressure, the actuator  1950  is actuated at  1959  to an open state. Subsequently, the shutter  1930  is also actuated at  1960  so that it also moves from a closed to an open position. Next, the actuator  1950  is deactivated at  1961  thereby locking the shutter  1930  in an open position with the head  1963  ( FIG. 371 ) of the actuator  1950  locking against one side of the shutter  1930 . Simultaneously, the shutter  1930  is deactivated at  1962  to reduce the power consumption in the nozzle. 
     As the ink chamber and ink nozzle are in a positive pressure state at this time, the ink meniscus will be expanding out of the ink nozzle. 
     Subsequently, the drop separation phase  1972  is entered wherein the chamber undergoes a negative pressure causing a portion of the ink flowing out of the ink nozzle back into the chamber. This rapid flow causes ink bubble separation from the main body of ink. The ink bubble or jet then passes to the print media while the surface meniscus of the ink collapses back into the ink nozzle. Subsequently, the pressure cycle enters the drop refill stage  1973  with the shutter  1930  still open with a positive pressure cycle experienced. This causes rapid refilling of the ink chamber. At the end of the drop re-filling stage, the actuator  1950  is opened at  1997  causing the now cold shutter  1930  to spring back to a closed position. Subsequently, the actuator  1950  is closed at  1964  locking the shutter  1930  in the closed position, thereby completing one cycle of printing. The closed shutter  1930  allows a drop settling stage  1974  to be entered which allows for the dissipation of any resultant ringing or transient in the ink meniscus position while the shutter  1930  is closed. At the end of the drop settling stage, the state has returned to the start of the drop formation stage  1971  and another drop can be ejected from the ink nozzle. 
     Of course, a number of refinements of operation are possible. In a first refinement, the pressure wave oscillation which is shown to be a constant oscillation in magnitude and frequency can be altered in both respects. The size and period of each cycle can be scaled in accordance with such pre-calculated factors such as the number of nozzles ejecting ink and the tuned pressure requirements for nozzle refill with different inks. Further, the clock periods of operation can be scaled to take into account differing effects such as actuation speeds etc. 
     Turning now to  FIG. 374 , there is illustrated at  1980  an exploded perspective view of one form of construction of the ink nozzle pair  1920 ,  1921  of  FIG. 371 . 
     The ink jet nozzles are constructed on a buried boron-doped layer  1981  of a silicon wafer  1982  which includes fabricated nozzle rims, e.g.  1983  which form part of the layer  1981  and limit any hydrophilic spreading of the meniscus on the bottom end of the layer  1981 . The nozzle rim, e.g.  1983  can be dispensed with when the bottom surface of layer  1981  is suitably treated with a hydrophobizing process. 
     On top of the wafer  1982  is constructed a CMOS layer  1985  which contains all the relevant circuitry required for driving of the two nozzles. This CMOS layer is finished with a silicon dioxide layer  1986 . Both the CMOS layer  1985  and the silicon dioxide  1986  include triangular apertures  1987  and  1988  allowing for fluid communication with the nozzle ports, e.g.  1984 . 
     On top of the SiO 2  layer  1986  are constructed the various shutter layers  1990  to  1992 . A first shutter layer  1990  is constructed from a first layer of polysilicon and comprises the shutter and actuator mechanisms. A second shutter layer  1991  can be constructed from a polymer, for example, polyamide and acts as a thermal insulator on one arm of each of the thermocouple devices. A final covering cage layer  1992  is constructed from a second layer of polysilicon. 
     The construction of the nozzles  1980  relies upon standard semi-conductor fabrication processes and MEMS process known to those skilled in the art. 
     One form of construction of nozzle arrangement  1980  would be to utilize a silicon wafer containing a boron doped epitaxial layer which forms the final layer  1981 . The silicon wafer layer  1982  is formed naturally above the boron doped epitaxial  1981 . On top of this layer is formed the layer  1985  with the relevant CMOS circuitry etc. being constructed in this layer. The apertures  1987 ,  1988  can be formed within the layers by means of plasma etching utilizing an appropriate mask. Subsequently, these layers can be passivated by means of a nitride covering and then filled with a sacrificial material such as glass which will be subsequently etched. A sacrificial material with an appropriate mask can also be utilized as a base for the moveable portions of the layer  1990  which are again deposited utilizing appropriate masks. Similar procedures can be carried out for the layers  1991 ,  1992 . Next, the wafer can be thinned by means of back etching of the wafer to the boron doped epitaxial layer  1991  which is utilized as an etchant stop. Subsequently, the nozzle rims and nozzle apertures can be formed and the internal portions of the nozzle chamber and other layers can be sacrificially etched away releasing the shutter structure. Subsequently, the wafer can be diced into appropriate print heads attached to an ink chamber wafer and tested for operational yield. 
     Of course, many other materials can be utilized to form the construction of each layer. For example, the shutter and actuators could be constructed from tantalum or a number of other substances known to those skilled in the art of construction of MEMS devices. 
     It will be evident to the person skilled in the art, that large arrays of ink jet nozzle pairs can be constructed on a single wafer and ink jet print heads can be attached to a corresponding ink chamber for driving of ink through the print head, on demand, to the required print media. Further, normal aspects of (MEMS) construction such as the utilization of dimples to reduce the opportunity for stiction, while not specifically disclosed in the current embodiment could be used as means to improve yield and operation of the shutter device as constructed in accordance with a preferred embodiment. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  1975  deposit 3 microns of epitaxial silicon heavily doped with boron  1981 . 
     2. Deposit 10 microns of n/n+ epitaxial silicon  1982 . Note that the epitaxial layer is substantially thicker than required for CMOS. This is because the nozzle chambers are crystallographically etched from this layer. This step is shown in  FIG. 376 .  FIG. 375  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. 
     3. Plasma etch the epitaxial silicon  1982  with approximately 90 degree sidewalls using MEMS Mask  1 . This mask defines the nozzle cavity  1922 . The etch is timed for a depth approximately equal to the epitaxial silicon  1982  (10 microns), to reach the boron doped silicon buried layer  1981 . This step is shown in  FIG. 377 . 
     4. Deposit 10 microns of low stress sacrificial oxide  1976 . Planarize down to silicon  1982  using CMP. The sacrificial material  1976  temporarily fills the nozzle cavity. This step is shown in  FIG. 378 . 
     5. Begin fabrication of the drive transistors, data distribution, and timing circuits using a CMOS process. The MEMS processes which form the mechanical components of the inkjet are interleaved with the CMOS device fabrication steps. The example given here is of a 1 micron, 2 poly, 1 metal retrograde P-well process. The mechanical components are formed from the CMOS polysilicon layers  1985 . For clarity, the CMOS active components are omitted. 
     6. Grow the field oxide using standard LOCOS techniques to a thickness of 0.5 microns. As well as the isolation between transistors, the field oxide is used as a MEMS sacrificial layer, so inkjet mechanical details are incorporated in the active area mask. The MEMS features of this step are shown in  FIG. 379 . 
     7. Perform the PMOS field threshold implant. The MEMS fabrication has no effect on this step except in calculation of the total thermal budget 
     8. Perform the retrograde P-well and NMOS threshold adjust implants. The MEMS fabrication has no effect on this step except in calculation of the total thermal budget. 
     9. Perform the PMOS N-tub deep phosphorus punchthrough control implant and shallow boron implant The MEMS fabrication has no effect on this step except in calculation of the total thermal budget. 
     10. Deposit and etch the first polysilicon layer  1994 . As well as gates and local connections, this layer  1994  includes the lower layer of MEMS components. This includes the shutter, the shutter actuator, and the catch actuator. It is preferable that this layer  1994  be thicker than the normal CMOS thickness. A polysilicon thickness of 1 micron can be used. The MEMS features of this step are shown in  FIG. 380 . 
     11. Perform the NMOS lightly doped drain (LDD) implant This process is unaltered by the inclusion of MEMS in the process flow. 
     12. Perform the oxide deposition and RIE etch for polysilicon gate sidewall spacers. This process is unaltered by the inclusion of MEMS in the process flow. 
     13. Perform the NMOS source/drain implant The extended high temperature anneal time to reduce stress in the two polysilicon layers must be taken into account in the thermal budget for diffusion of this implant. Otherwise, there is no effect from the MEMS portion of the chip. 
     14. Perform the PMOS source/drain implant. As with the NMOS source/drain implant, the only effect from the MEMS portion of the chip is on thermal budget for diffusion of this implant. 
     15. Deposit 1.3 micron of glass  1977  as the first interlevel dielectric and etch using the CMOS contacts mask. The CMOS mask for this level also contains the pattern for the MEMS inter-poly sacrificial oxide. The MEMS features of this step are shown in  FIG. 381 . 
     16. Deposit and etch the second polysilicon layer  1978 . As well as CMOS local connections, this layer  1978  includes the upper layer of MEMS components. This includes the grill and the catch second layer (which exists to ensure that the catch does not ‘slip off’ the shutter. A polysilicon thickness of 1 micron can be used. The MEMS features of this step are shown in  FIG. 382 . 
     17. Deposit 1 micron of glass  1979  as the second interlevel dielectric and etch using the CMOS via  1  mask. The CMOS mask for this level also contains the pattern for the MEMS actuator contacts. 
     18. Deposit and etch the metal layer. None of the metal appears in the MEMS area, so this step is unaffected by the MEMS process additions. However, all required annealing of the polysilicon should be completed before this step. The MEMS features of this step are shown in  FIG. 383 . 
     19. Deposit 0.5 microns of silicon nitride (Si 3 N 4 )  1993  and etch using MEMS Mask  2 . This mask defines the region of sacrificial oxide etch performed in step 24. The silicon nitride aperture is substantially undersized, as the sacrificial oxide etch is isotropic. The CMOS devices must be located sufficiently far from the MEMS devices that they are not affected by the sacrificial oxide etch. The MEMS features of this step are shown in  FIG. 384 . 
     20. Mount the wafer on a glass blank  1995  and back-etch the wafer  1981  using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. The MEMS features of this step are shown in  FIG. 385 . 
     21. Plasma back-etch the boron doped silicon layer  1981  to a depth of 1 micron using MEMS Mask  3 . This mask defines the nozzle rim  1983 . The MEMS features of this step are shown in  FIG. 386 . 
     22. Plasma back-etch through the boron doped layer  1981  using MEMS Mask  4 . This mask defines the nozzle  1984 , and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank. The MEMS features of this step are shown in  FIG. 387 . 
     23. Detach the chips from the glass blank  1995 . Strip the adhesive. This step is shown in  FIG. 388 . 
     24. Etch the sacrificial oxide  1976  using vapor phase etching (VPE) using an anhydrous HF/methanol vapor mixture. The use of a dry etch avoids problems with stiction. This step is shown in  FIG. 389 . 
     25. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. The package also includes a piezoelectric actuator attached to the rear of the ink channels. The piezoelectric actuator provides the oscillating ink pressure required for the ink jet operation. 
     26. Connect the print heads to their interconnect systems. 
     27. Hydrophobize the front surface of the print heads. 
     28. Fill the completed print heads with ink  1996  and test them. A filled nozzle is shown in  FIG. 390 . 
     IJ20 
     In a preferred embodiment, an ink jet printhead is constructed from an array of ink nozzle chambers which utilize a thermal actuator for the ejection of ink having a shape reminiscent of the calyx arrangement of a flower. The thermal actuator is activated so as to close the flower arrangement and thereby cause the ejection of ink from a nozzle chamber formed in the space above the calyx arrangement. The calyx arrangement has particular advantages in allowing for rapid refill of the nozzle chamber in addition to efficient operation of the thermal actuator. 
     Turning to  FIG. 391 , there is shown a perspective-sectional view of a single nozzle chamber of a printhead  2010  as constructed in accordance with a preferred embodiment. The printhead arrangement  2010  is based around a calyx type structure  2011  which includes a plurality of petals e.g.  2013  which are constructed from polytetrafluoroethylene (PTFE). The petals  2013  include an internal resistive element  2014  which can comprise a copper heater. The resistive element  2014  is generally of a serpentine structure, such that, upon heating, the resistive element  2014  can concertina and thereby expand at the rate of expansion of the PTFE petals, e.g.  2013 . The PTFE petal  2013  has a much higher coefficient thermal expansion (770×10 −6 ) and therefore undergoes substantial expansion upon heating. The resistive elements  2014  are constructed nearer to the lower surface of the PTFE petal  2013  and as a result, the bottom surface of PTFE petal  2013  is heated more rapidly than the top surface. The difference in thermal grading results in a bending upwards of the petals  2013  upon heating. Each petal e.g.  2013  is heated together which results in a combined upward movement of all the petals at the same time which in turn results in the imparting of momentum to the ink within chamber  2016  such that ink is forced out of the ink nozzle  2017 . The forcing out of ink out of ink nozzle  2017  results in an expansion of the meniscus  2018  and subsequently results in the ejection of drops of ink from the nozzle  2017 . 
     An important advantageous feature of a preferred embodiment is that PTFE is normally hydrophobic. In a preferred embodiment the bottom surface of petals  2013  comprises untreated PTFE and is therefore hydrophobic. This results in an air bubble  2020  forming under the surface of the petals. The air bubble contracts on upward movement of petals  2013  as illustrated in  FIG. 392  which illustrates a cross-sectional perspective view of the form of the nozzle after activation of the petal heater arrangement. 
     The top of the petals is treated so as to reduce its hydrophobic nature. This can take many forms, including plasma damaging in an ammonia atmosphere. The top of the petals  2013  is treated so as to generally make it hydrophilic and thereby attract ink into nozzle chamber  2016 . 
     Returning now to  FIG. 391 , the nozzle chamber  2016  is constructed from a circular rim  2021  of an inert material such as nitride as is the top nozzle plate  2022 . The top nozzle plate  2022  can include a series of the small etchant holes  2023  which are provided to allow for the rapid etching of sacrificial material used in the construction of the nozzle chamber  2010 . The etchant holes  2023  are large enough to allow the flow of etchant into the nozzle chamber  2016  however, they are small enough so that surface tension effects retain any ink within the nozzle chamber  2016 . A series of posts  2024  are further provided for support of the nozzle plate  2022  on a wafer  2025 . 
     The wafer  2025  can comprise a standard silicon wafer on top of which is constructed data drive circuitry which can be constructed in the usual manner such as two level metal CMOS with portions  2026  of one level of metal (aluminium) being used for providing interconnection with the copper circuitry portions  2027 . 
     The arrangement  2010  of  FIG. 391  has a number of significant advantages in that, in the petal open position, the nozzle chamber  2016  can experience rapid refill, especially where a slight positive ink pressure is utilised. Further, the petal arrangement provides a degree of fault tolerance in that, if one or more of the petals is non-functional, the remaining petals can operate so as to eject drops of ink on demand. 
     Turning now to  FIG. 393 , there is illustrated an exploded perspective of the various layers of a nozzle arrangement  2010 . The nozzle arrangement  2010  is constructed on a base wafer  2025  which can comprise a silicon wafer suitably diced in accordance with requirements. On the silicon wafer  2025  is constructed a silicon glass layer which can include the usual CMOS processing steps to construct a two level metal CMOS drive and control circuitry layer. Part of this layer will include portions  2027  which are provided for interconnection with the drive transistors. On top of the CMOS layer  2026 ,  2027  is constructed a nitride passivation layer  2029  which provides passivation protection for the lower layers during operation and also should an etchant be utilized which would normally dissolve the lower layers. The PTFE layer  2030  really comprises a bottom PTFE layer below a copper metal layer  2031  and a top PTFE layer above it, however, they are shown as one layer in  FIG. 393 . Effectively, the copper layer  2031  is encased in the PTFE layer  2030  as a result. Finally, a nitride layer  2032  is provided so as to form the rim  2021  of the nozzle chamber and nozzle posts  2024  in addition to the nozzle plate. 
     The arrangement  2010  can be constructed on a silicon wafer using micro-electro-mechanical systems techniques. The PTFE layer  2030  can be constructed on a sacrificial material base such as glass, wherein a via for stem  2033  of layer  2030  is provided. 
     The layer  2032  is constructed on a second sacrificial etchant material base so as to form the nitride layer  2032 . The sacrificial material is then etched away using a suitable etchant which does not attack the other material layers so as to release the internal calyx structure. To this end, the nozzle plate  2032  includes the aforementioned etchant holes e.g.  2023  so as to speed up the etching process, in addition to the nozzle  2017  and the nozzle rim  2034 . 
     The nozzles  2010  can be formed on a wafer of printheads as required. Further, the printheads can include supply means either in the form of a “through the wafer” ink supply means which uses high density low pressure plasma etching such as that available from Surface Technology Systems or via means of side ink channels attached to the side of the printhead. Further, areas can be provided for the interconnection of circuitry to the wafer in the normal fashion as is normally utilized with MEMS processes. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  2025 , Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2026 . This step is shown in  FIG. 395 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 394  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch through the silicon dioxide layers of the CMOS process down to silicon using mask  1 . This mask defines the ink inlet channels and the heater contact vias  2050 . This step is shown in  FIG. 396 . 
     3. Deposit 1 micron of low stress nitride  2029 . This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface. This step is shown in  FIG. 397 . 
     4. Deposit 3 micron of sacrificial material  2051  (e.g. photosensitive polyimide) 
     5. Etch the sacrificial layer using mask  2 . This mask defines the actuator anchor point This step is shown in  FIG. 398 . 
     6. Deposit 0.5 micron of PTFE  2052 . 
     7. Etch the PTFE, nitride, and oxide down to second level metal using mask  3 . This mask defines the heater vias. This step is shown in  FIG. 399 . 
     8. Deposit 0.5 micron of heater material  2031  with a low Young&#39;s modulus, for example aluminum or gold. 
     9. Pattern the heater using mask  4 . This step is shown in  FIG. 400 . 
     10. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated. 
     11. Deposit 1.5 microns of PTFE  2053 . 
     12. Etch the PTFE down to the sacrificial layer using mask  5 . This mask defines the actuator petals. This step is shown in  FIG. 401 . 
     13. Plasma process the PTFE to make the top surface hydrophilic. 
     14. Deposit 6 microns of sacrificial material  2054 . 
     15. Etch the sacrificial material to a depth of 5 microns using mask  6 . This mask defines the suspended walls  2021  of the nozzle chamber. 
     16. Etch the sacrificial material down to nitride using mask  7 . This mask defines the nozzle plate supporting posts  2024  and the walls surrounding each ink color (not shown). This step is shown in  FIG. 402 . 
     17. Deposit 3 microns of PECVD glass  2055 . This step is shown in  FIG. 403 . 
     18. Etch to a depth of 1 micron using mask  8 . This mask defines the nozzle rim  2034 . This step is shown in  FIG. 404 . 
     19. Etch down to the sacrificial layer using mask  9 . This mask defines the nozzle  2017  and the sacrificial etch access holes  2023 . This step is shown in  FIG. 405 . 
     20. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using mask  10 . This mask defines the ink inlets  2056  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 406 . 
     21. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch This step is shown in  FIG. 407 . 
     22. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     23. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     24. Hydrophobize the front surface of the printheads. 
     25. Fill the completed printheads with ink  2057  and test them. A filled nozzle is shown in  FIG. 408 . 
     IJ21 
     Turning initially to  FIG. 409 , in a preferred embodiment of a printing mechanism  2101 , there is provided an ink reservoir  2102  which is supplied from an ink supply conduit  2103 . A piezoelectric actuator  2104  is driven in a substantially sine wave form so as to set up pressure waves  2106  within the reservoir  2102 . The ultrasonic transducer  2104  typically comprises a piezoelectric transducer positioned within the reservoir  2102 . The transducer  2104  oscillates the ink pressure within the reservoir  2102  at approximately 100 KHz. The pressure is sufficient to eject the ink drops from each of a number of nozzle arrangements  2112  when required. Each nozzle arrangement  2112  is provided with a shutter  2110  which is opened and closed on demand. 
     Turning now to  FIG. 410 , there is illustrated the nozzle arrangement  2112  in further detail. 
     Each nozzle arrangement  2112  includes an ink ejection port  2113  for the output of ink and a nozzle chamber  2114  which is normally filled with ink. Further, each nozzle arrangement  2112  is provided with a shutter  2110  which is designed to open and close the nozzle chamber  2114  on demand. The shutter  2110  is actuated by a coiled thermal actuator  2115 . 
     The coiled actuator  2115  is constructed from laminated conductors of either differing resistivities, different cross-sectional areas, different indices of thermal expansion, different thermal conductivities to the ink, different length, or some combination thereof. A coiled radius of the actuator  2115  changes when a current is passed through the conductors, as one side of the coiled actuator  2115  expands differently to the other. One method, as illustrated in  FIG. 410 , can be to utilize two current paths  2135 ,  2136 , which are made of electrically conductive material. The current paths  2135 ,  2136  are connected at the shutter end  2117  of the thermal actuator  2115 . One current path  2136  is etched in a serpentine manner to increase its resistance. When a current is passed through paths  2135 ,  2136 , the side of the coiled actuator  2115  that comprises the serpentine path expands more than the side that comprises the paths  2135 . This results in the actuator  2115  uncoiling. 
     The thermal actuator  2115  controls the position of the shutter  2110  so that it can cover none, all or part of the nozzle chamber  2114 . If the shutter  2110  does not cover any of the nozzle chamber  2114  then the oscillating ink pressure will be transmitted to the nozzle chamber  2114  and the ink will be ejected out of the ejection port  2113 . When the shutter  2110  covers the ink chamber  2114 , then the oscillating ink pressure of the chamber is significantly attenuated at the ejection port  2113 . The ink pressure within the chamber  2114  will not be entirely stopped, due to leakage around the shutter  2110  when in a closed position and fixing of the shutter  2110  under varying pressures. 
     The shutter  2110  may also be driven to be partly across the nozzle chamber  2114 , resulting in a partial attenuation of the ink pressure variation. This can be used to vary the volume of the ejected drop. This can be utilized to implement a degree of continuation tone operation of the printing mechanism  2101  ( FIG. 409 ), to regulate the drop volume, or both. The shutter is normally shut, and is opened on demand. 
     The operation of the ink jet nozzle arrangement  2112  will now be explained in further detail. 
     Referring to  FIG. 411 , the piezoelectric device is driven in a sinusoidal manner which in turn causes a sinusoidal variation  2170  in the pressure within the ink reservoir  2102  ( FIG. 409 ) with respect to time. 
     The operation of the printing mechanism  2101  utilizes four phases being an ink ejection phase  2171 , an ink separation phase  2172 , an ink refill phase  2173  and an idle phase  2174 . 
     Referring now to  FIG. 412 , before the ink ejection phase  2171  of  FIG. 411 , the shutter  2110  is located over the ink chamber  2114  and the ink forms a meniscus  2181  over the ejection port  2113 . 
     At the start of the ejection phase  2171  the actuator coil is activated and the shutter  2110  moves away from its position over the chamber  2114  as illustrated in  FIG. 413 . As the chamber undergoes positive pressure, the meniscus  2181  grows and the volume of ink  2191  outside the ejection port  2113  increases due to an ink flow  2182 . Subsequently, the separation phase  2172  of  FIG. 411  is entered. In this phase, the pressure within the chamber  2114  becomes less than the ambient pressure. This causes a back flow  2183  ( FIG. 414 ) within the chamber  2114  and results in the separation of a body of ink  2184  from the ejection port  2113 . The meniscus  2185  moves up into the ink chamber  2114 . 
     Subsequently, the ink chamber  2114  enters the refill phase  2173  of  FIG. 411  wherein positive pressure is again experienced. This results in the condition indicated by  2186  in  FIG. 415  wherein the meniscus  2181  is positioned at  2187  to return to that of  FIG. 412 . Subsequently, as illustrated in  FIG. 416 , the actuator is turned off and the shutter  2110  returns to its original position ready for reactivation (idle phase  2174  of  FIG. 411 ). 
     The cyclic operation as illustrated in  FIG. 411  has a number of advantages. In particular, the level and duration of each sinusoidal cycle can be closely controlled by means of controlling the signal to the piezo electric actuator  2104  ( FIG. 409 ). Of course, a number of further variations are possible. For example, as each drop ejection takes two ink pressure cycles, half the nozzle arrangements  2112  of  FIG. 409  could be ejected in one phase and the other half of the nozzle arrangements  2112  could be ejected during a second phase. This allows for minimization of the pressure variations which would occur if a large number of nozzle arrangements were actuated simultaneously. 
     Further, the amplitude of the driving signal to the actuator  2104  can be altered in response to the viscosity of the ink which will typically be effected by such factors as temperature and the number of drops which are to be ejected in the current cycle. 
     Construction and Fabrication 
     Each nozzle arrangement  2112  further includes drive circuitry which activates the actuator coil when the shutter  2110  is to be opened. The nozzle chamber  2114  should be carefully dimensioned and a radius of the ejection port  2113  carefully selected to control the drop velocity and drop size. Further, the nozzle chamber  2114  of  FIG. 410  should be wide enough so that viscous drag from the chamber walls dots not significantly increase the force required from the ultrasonic oscillator. 
     Preferably, the shutter  2110  is of a disk form which covers the nozzle chamber  2114 . The disk preferably has a honeycomb-like structure to maximize strength while minimizing its inertial mass. 
     Preferably, all surfaces are coated with a passivation layer so as to reduce the possibility of corrosion from the ink flow. A suitable passivation layer can include silicon nitride (Si 3 N 4 ), diamond like carbon (DLC), or any other chemically inert, highly impermeable layer. The passivation layer is especially important for device lifetime, as the active device will be immersed in ink. 
     Fabrication Sequence 
       FIG. 417  is an exploded perspective view illustrating the construction of a single inkjet nozzle arrangement in accordance with a preferred embodiment. 
     1) Start with a single crystal silicon wafer  2140 , which has a buried epitaxial layer  2141  of silicon which is heavily doped with boron. The boron should be doped to preferably 10 20  atoms per cm 3  of boron or more, and be approximately 2 micron thick. The lightly doped silicon epitaxial layer on top of the boron doped layer should be approximately 8 micron thick, and be doped in a manner suitable for the active semiconductor device technology chosen. This is hereinafter called the “Sopij” wafer. The wafer diameter should be the same as the ink channel wafer. 
     2) Fabricate the drive transistors and data distribution circuitry according to the process chosen in the CMOS layer  2142 , up until the oxide extends over second level metal. 
     3) Planarize the wafer using Chemical Mechanical Planarization (CMP). 
     4) Plasma etch the nozzle chamber, stopping at the boron doped epitaxial silicon layer. This etch will be through around 8 micron of silicon. The etch should be highly anisotropic, with near vertical sidewalls. The etch stop determination can be the detection of boron in the exhaust gases. This step also etches the edge of printhead chips down to the boron layer  2141 , for later separation. 
     5) Conformally deposit 0.2 microns of high density Si 3 N 4    2143 . This forms a corrosion barrier, so should be free of pinholes and be impermeable to OH ions. 
     6) Deposit a thick sacrificial layer. This layer should entirely fill the nozzle chambers  2114 , and coat the entire wafer to an added thickness of 2 microns. The sacrificial layer may be SiO 2 , for example, spin or glass (SOG). 
     7) Mask and etch the sacrificial layer using the coil post mask. 
     8) Deposit 0.2 micron of silicon nitride (Si 3 N 4 ). 
     9) Mask and etch the Si 3 N 4  layer using the coil electric contacts mask, a first layer of PTFE layer  2144  using the coil mask. 
     10) Deposit 4 micron of nichrome alloy (NiCr). 
     11) Deposit the copper conductive layer  2145  and etch using the conductive layer mask. 
     12) Deposit a second layer of PTFE using the coil mask. 
     13) Deposit 0.2 micron of silicon nitride (Si 3 N 4 ) (not shown). 
     14) Mask and etch the Si 3 N 4 , layer using the spring passivation and bond pad mask. 
     15) Permanently bond the wafer onto a pre-fabricated ink channel wafer. The active side of the Sopij wafer faces the ink channel wafer. 
     16) Etch the Sopij wafer to entirely remove the backside silicon to the level of the boron doped epitaxial layer. This etch can be a batch wet etch in ethylene-diamine pyrocatechol (EPD). 
     17) Mask the ejection ports  2113  from the underside of the Sopij wafer. This mask also includes the chip edges. 
     18) Etch through the boron doped silicon layer  2141 . This etch should also etch fairly deeply into the sacrificial material in the nozzle chambers  2114  to reduce time required to remove the sacrificial layer. 
     19) Completely etch the sacrificial material. If this material is SiO 2 , then an HF etch can be used. Access of the HF to the sacrificial layer material is through the ejection port  2113 , and simultaneously through an ink channel in the chip. 
     20) Separate the chips from the backing plate. The two wafers have already been etched through, so the printheads do not need to be diced. 
     21) TAB bond the good chips. 
     22) Perform final testing on the TAB bonded printheads. 
     One alternative form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double-sided polished wafer  2150  deposit 3 microns of epitaxial silicon  2141  heavily doped with boron. 
     2. Deposit 10 microns of epitaxial silicon  2140 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2142 . The wafer is passivated with 0.1 microns of silicon nitride  2143 . This step is shown in  FIG. 419 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle arrangement  2112 .  FIG. 418  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers down to silicon using Mask  1 . This mask defines the nozzle chamber  2114  below the shutter  2110 , and the edges of the printhead chips. 
     5. Plasma etch the silicon down to the boron doped buried layer  2141 , using oxide from step  4  as a mask. This step is shown in  FIG. 420 . 
     6. Deposit 6 microns of sacrificial material  2151  (e.g. aluminum or photosensitive polyimide) 
     7. Planarize the sacrificial layer  2151  to a thickness of 1 micron over nitride  2143 . This step is shown in FIG.  421 . 
     8. Etch the sacrificial layer  2151  using Mask  2 . This mask defines the actuator anchor point  2152 . This step is shown in  FIG. 422 . 
     9. Deposit 1 micron of PTFE  2144 . 
     10. Etch the PTFE, nitride, and oxide down to second level metal using Mask  3 . This mask defines the heater vias. This step is shown in  FIG. 423 . 
     11. Deposit 1 micron of a conductor  2145  with a low Young&#39;s modulus, for example aluminum or gold. 
     12. Pattern the conductor using Mask  4 . This step is shown in  FIG. 424 . 
     13. Deposit 1 micron of PTFE. 
     14. Etch the PTFE down to the sacrificial layer using Mask  5 . This mask defines the actuator  2115  and shutter  2110  ( FIG. 410 ). This step is shown in  FIG. 425 . 
     15. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     16. Mount the wafer on a glass blank  2153  and back-etch the wafer using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer  2141 . This step is shown in  FIG. 426 . 
     17. Plasma back-etch the boron doped silicon layer  2141  to a depth of (approx.) 1 micron using Mask  6 . This mask defines the nozzle rim  2154 . This step is shown in  FIG. 427 . 
     18. Plasma back-etch through the boron doped layer using Mask  7 . This mask defines the nozzle  2113 , and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank  2153 . This step is shown in  FIG. 428 . 
     19. Detach the chips from the glass blank  2153  and etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 429 . 
     20. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     21. Connect the printheads to their interconnect systems. 
     22. Hydrophobize the front surface of the printheads. 
     23. Fill the completed printheads with ink  2155  and test them. A filled nozzle is shown in  FIG. 430 . 
     IJ22 
     In a preferred embodiment, there is a provided an ink jet printhead which includes a series of nozzle arrangements, each nozzle arrangement including an actuator device comprising a plurality of actuators which actuate a series of paddles that operate in an iris type motion so as to cause the ejection of ink from a nozzle chamber. 
     Turning initially to  FIG. 431  to  FIG. 433 , there is illustrated a single nozzle arrangement  2210  ( FIG. 433 ) for the ejection of ink from an ink ejection port  2211 . The ink is ejected out of the port  2211  from a nozzle chamber  2212  which is formed from substantially identical iris vanes  2214 . Each iris vane  2214  is operated simultaneously to cause the ink within the nozzle chamber  2212  to be squeezed out of the nozzle chamber  2212 , thereby ejecting the ink from the ink ejection port  2211 . 
     Each nozzle vane  2214  is actuated by means of a thermal actuator  2215  positioned at its base. Each thermal actuator  2115  has two arms namely, an expanding, flexible arm  2225  and a rigid arm  2226 . Each actuator is fixed at one end  2227  and is displaceable at an opposed end  2228 . Each expanding arm  2225  can be constructed from a polytetrafluoroethylene (PTFE) layer  2229 , inside of which is constructed a serpentine copper heater  2216 . The rigid arm  2226  of the thermal actuator  2215  comprises return trays of the copper heater  2216  and the vane  2214 . The result of the heating of the expandable arms  2225  of the thermal actuators  2215  is that the outer PTFE layer  2229  of each actuator  2215  is caused to bend around thereby causing the vanes  2214  to push ink towards the centre of the nozzle chamber  2212 . The serpentine trays of the copper layer  2216  concertina in response to the high thermal expansion of the PTFE layer  2229 . The other vanes  2218 - 2220  are operated simultaneously. The four vanes therefore cause a general compression of the ink within the nozzle chamber  2212  resulting in a subsequent ejection of ink from the ink ejection port  2211 . 
     A roof  2222  of the nozzle arrangement  2210  is formed from a nitride layer and is supported by posts  2223 . The roof  2222  includes a series of holes  2224  which are provided in order to facilitate rapid etching of sacrificial materials within lower layers during construction. The holes  2224  are provided of a small diameter such that surface tension effects are sufficient to stop any ink being ejected from the nitride holes  2224  as opposed to the ink ejection port  2211  upon activation of the iris vanes  2214 . 
     The arrangement of  FIG. 431  can be constructed on a silicon wafer utilizing standard semi-conductor fabrication and micro-electro-mechanical systems (MEMS) techniques. The nozzle arrangement  2210  can be constructed on a silicon wafer and built up by utilizing various sacrificial materials where necessary as is common practice with MEMS constructions. Turning to  FIG. 433 , there is illustrated an exploded perspective view of a single nozzle arrangement  2210  illustrating the various layers utilized in the construction of a single nozzle. The lowest layer of the construction comprises a silicon wafer base  2230 . A large number of printheads each having a large number of print nozzles in accordance with requirements can be constructed on a single large wafer which is appropriately diced into separate printheads in accordance with requirements. On top of the silicon wafer layer  2230  is first constructed a CMOS circuitry/glass layer  2231  which provides all the necessary interconnections and driving control circuitry for the various heater circuits. On top of the CMOS layer  2231  is constructed a nitride passivation layer  2232  which is provided for passivating the lower CMOS layer  2231  against any etchants which may be utilized. A layer  2232  having the appropriate vias (not shown) for connection of the heater  2216  to the relevant portion of the lower CMOS layer  2231  is provided. 
     On top of the nitride layer  2232  is constructed the aluminum layer  2233  which includes various heater circuits in addition to vias to the lower CMOS layer. 
     Next a PTFE layer  2234  is provided with the PTFE layer  2234  comprising layers which encase a lower copper layer  2233 . Next, a first nitride layer  2236  is constructed for the iris vanes  2214 ,  2218 - 2220  of  FIG. 431 . On top of this is a second nitride layer  2237  which forms the posts and nozzle roof of the nozzle chamber  2212 . 
     The various layers  2233 ,  2234 ,  2236  and  2237  can be constructed utilizing intermediate sacrificial layers which are, as standard with MEMS processes, subsequently etched away so as to release the functional device. Suitable sacrificial materials include glass. When necessary, such as in the construction of nitride layer  2237 , various other semi-conductor processes such as dual damascene processing can be utilized. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  2230 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2231 . The wafer is passivated with 0.1 microns of silicon nitride  2232 . Relevant features of the wafer at this step are shown in  FIG. 435 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 434  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Deposit 1 micron of sacrificial material  2241  (e.g. aluminum or photosensitive polyimide) 
     3. Etch the sacrificial layer using Mask  1 . This mask defines the nozzle chamber posts  2223  and the actuator anchor point This step is shown in  FIG. 436 . 
     4. Deposit 1 micron of PTFE  2242 . 
     5. Etch the PTFE, nitride, and oxide down to second level metal using Mask  2 . This mask defines the heater vias. This step is shown in  FIG. 437 . 
     6. Deposit 1 micron of a conductor  2216  with a low Young&#39;s modulus, for example aluminum or gold. 
     7. Pattern the conductor using Mask  3 . This step is shown in  FIG. 438 . 
     8. Deposit 1 micron of PTFE. 
     9. Etch the PTFE down to the sacrificial layer using Mask  4 . This mask defines the actuators  2215 . This step is shown in  FIG. 439 . 
     10. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     11. Deposit 6 microns of sacrificial material  2243 . 
     12. Etch the sacrificial material using Mask  5 . This mask defines the iris paddle vanes  2214 ,  2218 - 2220  and the nozzle chamber posts  2223 . This step is shown in  FIG. 440 . 
     13. Deposit 3 microns of PECVD glass and planarize down to the sacrificial layer using CMP. 
     14. Deposit 0.5 micron of sacrificial material. 
     15. Etch the sacrificial material down to glass using Mask  6 . This mask defines the nozzle chamber posts  2223 . This step is shown in  FIG. 441 . 
     16. Deposit 3 microns of PECVD glass  2244 . 
     17. Etch to a depth of (approx.) 1 micron using Mask  7 . This mask defines a nozzle rim. This step is shown in  FIG. 442 . 
     18. Etch down to the sacrificial layer using Mask  8 . This mask defines the roof  2222  of the nozzle chamber  2212 , the port  2211 , and the sacrificial etch access holes  2224 . This step is shown in  FIG. 443 . 
     19. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  9 . This mask defines the ink inlets  2245  which are etched through the wafer. When the silicon layer is etched, change the etch chemistry to etch the glass and nitride using the silicon as a mask. The wafer is also diced by this etch. This step is shown in  FIG. 444 . 
     20. Etch the sacrificial material. The nozzle chambers  2212  are cleared, the actuators  2215  freed, and the chips are separated by this etch. This step is shown in  FIG. 445 . 
     21. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     22. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     23. Hydrophobize the front surface of the printheads. 
     24. Fill the completed printheads with ink  2246  and test them. A filled nozzle is shown in  FIG. 446 . 
     IJ23 
     In a preferred embodiment, ink is ejected from a nozzle arrangement by bending of a thermal actuator so as to eject t ink. 
     Turning now to  FIG. 447 , there is illustrated a single nozzle arrangement  2301  of a preferred embodiment. The nozzle arrangement  2301  includes a thermal actuator  2302  located above a nozzle chamber  2303  and an ink ejection port  2304 . The thermal actuator  2302  includes an electrical circuit comprising leads  2306 ,  2307  connected to a serpentine resistive element  2308 . The resistive element  8  can comprise the copper layer in this respect, a copper stiffener  2309  is provided to provide support for one end of the thermal actuator  2302 . 
     The copper resistive element  2308  is constructed in a serpentine manner to provide very little tensile strength along the length of the thermal actuator panel  2302 . 
     The copper resistive element  2308  is embedded in a polytetrafluoroethylene (PTFE) layer  2312 . The PTFE layer  2312  has a very high coefficient of thermal expansion (approximately 770×10 −6 ). This layer undergoes rapid expansion when heated by the copper heater  2308 . The copper heater  2308  is positioned closer to a top surface of the PTFE layer  2312 , thereby heating an upper layer of the PTFE layer  2312  faster than the bottom layer, resulting in a bending down of the thermal actuator  2302  towards the ejection port  2304 . 
     The operation of the nozzle arrangement  2301  is as follows: 
     1) When data signals distributed on the printhead indicate that the nozzle arrangement is to eject a drop of ink, a drive transistor for the nozzle arrangement is turned on. This energizes the leads  2306 ,  2307 , and the heater  2308  in the actuator  2302  of the nozzle arrangement. The heater  2308  is energized for approximately 3 microseconds, with the actual duration depending upon the design chosen for the nozzle arrangement. 
     2) The heater heats the PTFE layer  2312 , with the top layer of the PTFE layer  2312  being heated more rapidly than the bottom layer. This causes the actuator to bend generally towards the ejection port  2304 , in to the nozzle chamber  2303 , as illustrated in  FIG. 448 . The bending of the actuator  2302  pushes ink from the ink chamber  2303  out of the ejection  2304 . 
     3) When the heater current is turned off, the actuator  2302  begins to return to its quiescent position The return of the actuator  2302  ‘sucks’ some of the ink back into the nozzle chamber  2303 , causing an ink ligament connecting the ink drop to the ink in the chamber  2303  to thin. The forward velocity of the drop and backward velocity of the ink in the chamber are resolved by the ink drop breaking off from the ink in the chamber  2303 . The ink drop then continues towards the recording medium. 
     4) The actuator  2302  remains at the quiescent position until the next drop ejection cycle. 
     Construction 
     In order to construct a series of the nozzle arrangement  2301  the following major parts need to be constructed: 
     1) Drive circuitry to drive the nozzle arrangement  2301 . 
     2) The ejection port  2304 . The radius of the ejection port  2304  is an important determinant of drop velocity and drop size. 
     3) The actuator  2302  is constructed of a heater layer embedded in the PTFE layer  2312 . The actuator  2302  is fixed at one side of the ink chamber  2303 , and the other end is suspended ‘over’ the ejection port  2304 . Approximately half of the actuator  2302  contains the copper element  2308 . A heater section of the element  2308  is proximate the fixed end of the actuator  2302 . 
     4) The nozzle chamber  2303 . The nozzle chamber  2303  is slightly wider than the actuator  2302 . The gap between the actuator  2302  and the nozzle chamber  2303  is determined by the fluid dynamics of the ink ejection and refill process. If the gap is too large, much of the actuator force will be wasted on pushing ink around the edges of the actuator. If the gap is too small, the ink refill time will be too long. Also, if the gap is too small, the crystallographic etch of the nozzle chamber will take too long to complete. A 2 micron gap will usually be sufficient. The nozzle chamber is also deep enough so that air ingested through the ejection port  2304  when the actuator returns to its quiescent state does not extend to the actuator. If it does, the ingested bubble may form a cylindrical surface instead of a hemispherical surface. If this happens, the chamber  2303  will not refill properly. A depth of approximately 20 micron is suitable. 
     5) Nozzle chamber ledges  2313 . As the actuator  2302  moves approximately 10 microns, and a crystallographic etch angle of chamber surface  2314  is 54.74 degrees, a gap of around 7 micron is required between the edge of the paddle  2302  and the outermost edge of the nozzle chamber  2303 . The walls of the nozzle chamber  2303  must also clear the ejection port  2304 . This requires that the nozzle chamber  2303  be approximately 52 micron wide, whereas the actuator  2302  is only 30 micron wide. Were there to be an 11 micron gap around the actuator  2302 , too much ink would flow around to the sides of the actuator  2302  when the actuator  2302  is energized. To prevent this, the nozzle chamber  2303  is undercut 9 micron into the silicon surrounding the paddle, leaving a 9 micron wide ledge  2313  to prevent ink flow around the actuator  2302 . 
     EXAMPLE 
     Basic Fabrication Sequence 
     Two wafers are required: a wafer upon which the active circuitry and nozzles are fabricated (the print head wafer) and a further wafer in which the ink channels are fabricated. This is the ink channel wafer. One form of construction of printhead wafer will now be discussed with reference to  FIG. 449  which illustrates an exploded perspective view of a single inkjet nozzle constructed in accordance with a preferred embodiment. 
     1) Starting with a single crystal silicon wafer, which has a buried epitaxial layer  2316  of silicon which is heavily doped with boron. The boron should be doped to preferably 10 20  atoms per cm 3  of boron or more, and be approximately 3 micron thick The lightly doped silicon epitaxial layer  2315  on top of the boron doped layer should be approximately 8 micron thick, and be doped in a manner suitable for the active semiconductor device technology chosen. This is the printhead wafer. The wafer diameter should preferably be the same as the ink channel wafer. 
     2) The drive transistors and data distribution circuitry layer  2317  is fabricated according to the process chosen, up until the oxide layer over second level metal. 
     3) Next, a silicon nitride passivation layer  2318  is deposited. 
     4) Next, the actuator  2302  ( FIG. 447 ) is constructed. The actuator  2302  comprises one copper layer  2319  embedded in a PTFE layer  2320 . The copper layer  2319  comprises both the heater element  2308  and planar portion  2309  (of  FIG. 447 ). Turning now to  FIG. 450 , the corrugated resistive element can be formed by depositing a resist layer  2350  on top of the first PTFE layer  2351 . The resist layer  2350  is exposed utilizing a mask  2352  having a half-tone pattern delineating the corrugations. After development the resist  2350  contains the corrugation pattern. The resist layer  2350  and the PTFE layer  2351  are then etched utilizing an etchant that erodes the resist layer  2350  at substantially the same rate as the PTFE layer  2351 . This transfers the corrugated pattern into the PTFE layer  2351 . Turning to  FIG. 451 , on top of the corrugated PTFE layer  2351  is deposited the copper heater layer  2319  which takes on a corrugated form in accordance with its under layer. The copper heater layer  2319  is then etched in a serpentine or concertina form. In  FIG. 452  there is illustrated a top view of the copper layer  2319  only, comprising the serpentine heater element  2308  and the portion  2309 . Subsequently, a further PTFE layer  2353  is deposited on top of layer  2319  so as to form the top layer of the thermal actuator  2302 . Finally, the second PTFE layer  2352  is planarized to form the top surface of the thermal actuator  2302  ( FIG. 447 ). 
     5) Etch through the PTFE, and all the way down to silicon in the region around the three sides of the paddle. The etched region should be etched on all previous lithographic steps, so that the etch to silicon does not require strong selectivity against PTFE. 
     6) Etch the wafers in an anisotropic wet etch, which stops on &lt;111&gt; crystallographic planes or on heavily boron doped silicon. The etch can be a batch wet etch in ethylenediamine pyrocatechol (EDP). The etch proceeds until the paddles are entirely undercut thereby forming the nozzle chamber  2303 . The backside of the wafer need not be protected against this etch, as the wafer is to be subsequently thinned. Approximately 60 micron of silicon will be etched from the wafer backside during this process. 
     7) Permanently bond the printhead wafer onto a pre-fabricated ink channel wafer. The active side of the printhead wafer faces the ink channel wafer. The ink channel wafer is attached to a backing plate, as it has already been etched into separate ink channel chips. 
     8) Etch the printhead wafer to entirely remove the backside silicon to the level of the boron doped epitaxial layer  2316 . This etch can be a batch wet etch in ethylenediamine pyrocatechol (EDP). 
     9) Mask an ejection port rim  2311  ( FIG. 447 ) from the underside of the print head wafer. This mask is a series of circles approximately 0.5 micron to 1 micron larger in radius than the nozzles. The purpose of this step is to leave a raised rim  2311  around the ejection port  2304 , to help prevent ink spreading on the front surface of the wafer. This step can be eliminated if the front surface is made sufficiently hydrophobic to reliably prevent front surface wetting. 
     10) Etch the boron doped silicon layer  2316  to a depth of 1 micron. 
     11) Mask the ejection ports from the underside of the printhead wafer. This mask can also include the chip edges. 
     12) Etch through the boron doped silicon layer to form the ink ejection ports  2304 . 
     13) Separate the chips from their backing plate. Each chip is now a full printhead including ink channels. The two wafers have already been etched through, so the printheads do not need to be diced. 
     14) Test the printheads and TAB bond the good printheads. 
     15) Hydrophobize the front surface of the printheads. 
     17) Perform final testing on the TAB bonded printheads. 
     It would be evident to persons skilled in the relevant arts that the arrangement described by way of example in a preferred embodiments will result in a nozzle arrangement able to eject ink on demand and be suitable for incorporation in a drop on demand ink jet printer device having an array of nozzles for the ejection of ink on demand. 
     Of course, alternative embodiments will also be self-evident to the person skilled in the art. For example, the thermal actuator could be operated in a reverse mode wherein passing current through the actuator results in movement of the actuator to an ink loading position when the subsequent cooling of the paddle results in the ink being ejected. However, this has a number of disadvantages in that cooling is likely to take a substantially longer time than heating and this arrangement would require a constant current to be passed through the nozzle arrangement when not in use. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  2360  deposit 3 microns of epitaxial silicon heavily doped with boron  2316 . 
     2. Deposit 10 microns of epitaxial silicon  2315 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2317 . This step is shown in  FIG. 454 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 453  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber, and the edges of the printheads chips. This step is shown in  FIG. 455 . 
     5. Crystallographically etch the exposed silicon using, for example, KOH or EDP (ethylenediamine pyrocatechol). This etch stops on &lt;111&gt; crystallographic planes  2361 , and on the boron doped silicon buried layer. This step is shown in  FIG. 456 . 
     6. Deposit 0.5 microns of low stress silicon nitride  2362 . 
     7. Deposit 12 microns of sacrificial material (polyimide)  2363 . Planarize down to nitride using CMP. The sacrificial material temporarily fills the nozzle cavity. This step is shown in  FIG. 457 . 
     8. Deposit 1 micron of PTFE  2364 . 
     9. Deposit, expose and develop 1 micron of resist  2365  using Mask  2 . This mask is a gray-scale mask which defines the heater vias as well as the corrugated PTFE surface that the heater is subsequently deposited on. 
     10. Etch the PTFE and resist at substantially the same rate. The corrugated resist thickness is transferred to the PTFE, and the PTFE is completely etched in the heater via positions. In the corrugated regions, the resultant PTFE thickness nominally varies between 0.25 micron and 0.75 micron, though exact values are not critical. This step is shown in  FIG. 458 . 
     11. Etch the nitride and CMOS passivation down to second level metal using the resist and PTFE as a mask. 
     12. Deposit and pattern resist using Mask  3 . This mask defines the heater. 
     13. Deposit 0.5 microns of gold  2366  (or other heater material with a low Young&#39;s modulus) and strip the resist Steps 11 and 12 form a lift-off process. This step is shown in  FIG. 459 . 
     14. Deposit 1.5 microns of PTFE  2367 . 
     15. Etch the PTFE down to the nitride or sacrificial layer using Mask  4 . This mask defines the actuator  2302  and the bond pads. This step is shown in  FIG. 460 . 
     16. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated 
     17. Plasma process the PTFE to make the top and side surfaces of the paddle hydrophilic. This allows the nozzle chamber to fill by capillarity. 
     18. Mount the wafer on a glass blank  2368  and back-etch the wafer using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in  FIG. 461 . 
     19. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask  5 . This mask defines the nozzle rim  2311 . This step is shown in  FIG. 462 . 
     20. Plasma back-etch through the boron doped layer and sacrificial layer using Mask  6 . This mask defines the nozzle  2304 , and the edge of the chips. At this stage, the chips are still mounted on the glass blank. This step is shown in  FIG. 463 . 
     21. Etch the remaining sacrificial material while the wafer is still attached to the glass blank. 
     22. Plasma process the PTFE through the nozzle holes to render the PTFE surface hydrophilic. 
     23. Strip the adhesive layer to detach the chips from the glass blank. This process completely separates the chips. This step is shown in  FIG. 464 . 
     24. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     25. Connect the printheads to their interconnect systems. 
     26. Hydrophobize the front surface of the printheads. 
     27. Fill with ink  2369  and test the completed printheads. A filled nozzle is shown in  FIG. 465 . 
     IJ24 
     In a preferred embodiment, an inkjet nozzle is provided having a thermally based actuator which is highly energy efficient. The thermal actuator is located within a chamber filled with ink and relies upon the thermal expansion of materials when an electric current is being passed through them to activate the actuator thereby causing the ejection of ink out of a nozzle provided in the nozzle chamber. 
     Turning to the Figures, in  FIG. 466 , there are illustrated two adjoining inkjet nozzles  2401  constructed in accordance with a preferred embodiment, with  FIG. 467  showing an exploded perspective and  FIG. 469  showing various sectional views. Each nozzle  2401 , can be constructed as part of an array of nozzles on a silicon wafer device and can be constructed utilizing semiconductor processing techniques in addition to micro machining and micro fabrication process technology (MEMS) and a full familiarity with these technologies is hereinafter assumed. 
     A nozzle chamber  2410  includes a ink ejection port  2411  for the ejection of ink from within the nozzle chamber. Ink is supplied via an inlet port  2412  which has a grill structure fabricated from a series of posts  2414 , the grill acting to filter out foreign bodies within the ink supply and also to provide stability to the nozzle chamber structure. Inside the nozzle chamber is constructed a thermal actuator device  2416  which is interconnected to an electric circuit (not shown) which, when thermally actuated, acts as a paddle bending upwards so as to cause the ejection of ink from each ink ejection port  2411 . A series of etchant holes e.g.  2418  are also provided in the top of nozzle chamber  2410 , the holes  2418  being provided for manufacturing purposes only so to allow a sacrificial etchant to easily etch away the internal portions of nozzle chamber  2410 . The etchant ports  2418  are of a sufficiently small diameter so that the resulting surface tension holds the ink within chamber  2410  such that no ink leaks out via ports  2418 . 
     The thermal actuator  2416  is composed primarily of polytetrafluoroethylene (PTFE) which is a generally hydrophobic material. The top layer of the actuator  2416  is treated or coated so as to make it hydrophilic and thereby attract water/ink via inlet port  2412 . Suitable treatments include plasma exposure in an ammonia atmosphere. The bottom surface remains hydrophobic and repels the water from the underneath surface of the actuator  2416 . Underneath the actuator  2416  is provided a further surface  2419  also composed of a hydrophobic material such as PTFE. The surface  2419  has a series of holes  2420  in it which allow for the flow of air into the nozzle chamber  2410 . The diameter of the nozzle holes  2420  again being of such a size so as to restrict the flow of fluid out of the nozzle chamber via surface tension interactions out of the nozzle chamber. 
     The surface  2419  is separated from a lower level  2423  by means of a series of spaced apart posts e.g.  2422  which can be constructed when constructing the layer  2419  utilizing an appropriate mask. The nozzle chamber  2410 , but for grill inlet port  2412 , is walled on its sides by silicon nitride walls e.g.  2425 ,  2426 . An air inlet port is formed between adjacent nozzle chambers such that air is free to flow between the walls  2425 ,  2428 . Hence, air is able to flow down channel  2429  and along channel  2430  and through holes e.g.  2420  in accordance with any fluctuating pressure influences. 
     The air flow acts to reduce the vacuum on the back surface of actuator  2416  during operation. As a result, less energy is required for the movement of the actuator  2416 . In operation, the actuator  2416  is thermally actuated so as to move upwards and cause ink ejection. As a result, air flows in along channels  2429 ,  2430  and through the holes e.g.  2420  into the bottom area of actuator  2416 . Upon deactivation of the actuator  2416 , the actuator lowers with a corresponding airflow out of port  2420  along channel  2430  and out of channel  2429 . Any fluid within nozzle chamber  2410  is firstly repelled by the hydrophobic nature of the bottom side of the surface of actuator  2416  in addition to the top of the surface  2419  which is again hydrophobic. As noted previously the limited size holes e.g.  2420  further stop the fluid from passing the holes  2420  as a result of surface tension characteristics. 
     A further preferable feature of nozzle chamber  2410  is the utilisation of the nitride posts  2414  to also clamp one end of the surfaces  2416  and  2419  firmly to bottom surface  2420  thereby reducing the likelihood delaminating during operation. 
     In  FIG. 467 , there is illustrated an exploded perspective view of a single nozzle  2401 . The exploded perspective view illustrates the form of construction of each layer of a simple nozzle  2401 . The nozzle arrangement can be constructed on a base silicon wafer  2434  having a top glass layer which includes the various drive and control circuitry and which, for example, can comprise a two level metal CMOS layer  2435  with the various interconnects (not shown). On top of the layer  2435  is first laid out a nitride passivation layer  2423  of approximately one micron thickness which includes a number of vias (not shown) for the interconnection of the subsequent layers to the CMOS layer  2435 . The nitride layer is provided primarily to protect lower layers from corrosion or etching, especially where sacrificial etchants are utilized. Next, a one micron PTFE layer  2419  is constructed having the aforementioned holes e.g.  2420  and posts  2422 . The structure of the PTFE layer  2419  can be formed by first laying down a sacrificial glass layer (not shown) onto which the PTFE layer  2419  is deposited. The PTFE layer  2419  includes various features, for example, a lower ridge portion  2438  in addition to a hole  2439  which acts as a via for the subsequent material layers. 
     The actuator proper is formed from two PTFE layers  2440 ,  2441 . The lower PTFE layer  2440  is made conductive. The PTFE layer  2440  can be made conductive utilizing a number of different techniques including: 
     (i) Doping the PTFE layer with another material so as to make it conductive. 
     (ii) Embedding within the PTFE layer a series of quantum wires constructed from such a material as carbon nanotubes created in a mesh form. (“Individual single-wall carbon nano-tubes as quantum wires” by Tans et al Nature, Volume 386, Apr. 3, 1997 at pages 474-477). The PTFE layer  2440  includes certain cut out portions e.g.  2443  so that a complete circuit is formed around the PTFE actuator  2440 . The cut out portions can be optimised so as to regulate the resistive heating of the layer  2440  by means of providing constricted portions so as to thereby increase the heat generated in various “hot spots” as required. A space is provided between the PTFE layer  2419  and the PTFE layer  2440  through the utilisation of an intermediate sacrificial glass layer (not shown). 
     On top of the PTFE layer  2440  is deposited a second PTFE layer  2441  which can be a standard non conductive PTFE layer and can include filling in those areas in the lower PTFE layer e.g.  2443  which are not conductive. The top of the PTFE layer is further treated or coated to make it hydrophilic. 
     Next, a nitride layer can be deposited to form the nozzle chamber proper. The nitride layer can be formed by first laying down a sacrificial glass layer and etching the glass layer to form walls e.g.  2425 ,  2426  and grilled portion e.g.  2414 . Preferably, the mask utilized results a first anchor portion  2445  which mates with the hole  2439  in layer  2419  so as to fix the layer  2419  to the nitride layer  2423 . Additionally, the bottom surface of the grill  2414  meets with a corresponding step  2447  (See  FIG. 468 ) in the PTFE layer  2441  so as to clamp the end portion of the PTFE layers  2441 ,  2440  and  2439  to the wafer surface so as to guard against delamination. Next, a top nitride layer  2450  can be formed having a number of holes e.g.  2418  and nozzle hole  2411  around which a rim can be etched through etching of the nitride layer  2450 . Subsequently, the various sacrificial layers can be etched away so as to release the structure of the thermal actuator. 
     Obviously, large arrays of inkjet nozzles  2401  can be created side by side on a single wafer. The ink can be supplied via ink channels etched through the wafer utilizing a high density low pressure plasma etching system such as that supplied by Surface Technology Systems of the United Kingdom. 
     The foregoing describes only one embodiment of the invention and many variations of the embodiment will be obvious for a person skilled in the art of semi conductor, micro mechanical fabrication. Certainly, various other materials can be utilized in the construction of the various layers. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  2434 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2435 . Relevant features of the wafer at this step are shown in  FIG. 471 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 470  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Deposit 1 micron of low stress nitride  2423 . This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface. 
     3. Deposit 2 microns of sacrificial material  2460  (e.g. polyimide). 
     4. Etch the sacrificial layer using Mask  1 . This mask defines the PTFE venting layer support pillars and anchor point This step is shown in  FIG. 472 . 
     5. Deposit 2 microns of PTFE  2419 . 
     6. Etch the PTFE using Mask  2 . This mask defines the edges of the PTFE venting layer, and the holes in this layer. This step is shown in  FIG. 473 . 
     7. Deposit 3 micron of sacrificial material  2461  (e.g. polyimide). 
     8. Etch the sacrificial layer and CMOS passivation layer using Mask  3 . This mask defines the actuator contacts. This step is shown in  FIG. 474 . 
     9. Deposit 1 micron of conductive PTFE  2440 . Conductive PTFE can be formed by doping the PTFE with a conductive material, such as extremely fine metal or graphitic filaments, or fine metal particles, and so forth. The PTFE should be doped so that the resistance of the PTFE conductive heater is sufficiently low so that the correct amount of power is dissipated by the heater when the drive voltage is applied. However, the conductive material should be a small percentage of the PTFE volume, so that the coefficient of thermal expansion is not significantly reduced. Carbon nanotubes can provide significant conductivity at low concentrations. This step is shown in  FIG. 475 . 
     10. Etch the conductive PTFE using Mask  4 . This mask defines the actuator conductive regions. This step is shown in  FIG. 476 . 
     11. Deposit 1 micron of PTFE  2441 . 
     12. Etch the PTFE down to the sacrificial layer using Mask  5 . This mask defines the actuator paddle. This step is shown in  FIG. 477 . 
     13. Wafer probe. All electrical connections are complete at this point and the chips are not yet separated. 
     14. Plasma process the PTFE to make the top and side surfaces of the paddle hydrophilic. This allows the nozzle chamber to fill by capillarity. 
     15. Deposit 10 microns of sacrificial material  2462 . 
     16. Etch the sacrificial material down to nitride using Mask  6 . This mask defines the nozzle chamber and inlet filter. This step is shown in  FIG. 478 . 
     17. Deposit 3 microns of PECVD glass  2450 . This step is shown in  FIG. 479 . 
     18. Etch to a depth of 1 micron using Mask  7 . This mask defines the nozzle rim  2463 . This step is shown in  FIG. 480 . 
     19. Etch down to the sacrificial layer using Mask  8 . This mask defines the nozzle  2411  and the sacrificial etch access holes  2418 . This step is shown in  FIG. 481 . 
     20. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  9 . This mask defines the ink inlets  2461  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 482 . 
     21. Back-etch the CMOS oxide layers and subsequently deposited nitride layers through to the sacrificial layer using the back-etched silicon as a mask. 
     22. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch This step is shown in  FIG. 483 . 
     23. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     24. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     25. Hydrophobize the front surface of the printheads. 
     26. Fill the completed printheads with ink  2465  and test them. A filled nozzle is shown in  FIG. 484 . 
     IJ25 
     In a preferred embodiment, there is provided a nozzle chamber having an ink ejection port and a magnetostrictive actuator surrounded by an electrical coil such that, upon activation of the coil, a magnetic field is produced which affects the actuator to the extent that it causes the ejection of ink from the nozzle chamber. 
     Turning now to  FIG. 485 , there is illustrated a perspective cross-sectional view, of a single ink jet nozzle arrangement  2510 . The nozzle arrangement includes a nozzle chamber  2511  which opens to a nozzle ejection port  2512  for the ejection of ink. 
     The nozzle  2510  can be formed on a large silicon wafer with multiple printheads being formed from nozzle groups at the same time. The ejection port  2512  can be formed from back etching the silicon wafer to the level of a boron doped epitaxial layer  2513  which is subsequently etched using an appropriate mask to form the nozzle portal  2512  including a rim  2515 . The nozzle chamber  2511  is further formed from a crystallographic etch of the remaining portions of the silicon wafer  2516 , the crystallographic etching process being well known in the field of micro-electro-mechanical systems (MEMS). 
     Tuning now to  FIG. 486  there is illustrated an exploded perspective view illustrating the construction of a single inkjet nozzle arrangement  2510  in accordance with a preferred embodiment. 
     On top of the silicon wafer  2516  there is previously constructed a two level metal CMOS layer  2517 ,  2518  which includes an aluminum layer (not shown). The CMOS layer  2517 ,  2518  is constructed to provide data and control circuitry for the ink jet nozzle  2510 . On top of the CMOS layer  2517 ,  2518  is constructed a nitride passivation layer  2520  which includes nitride paddle portion  2521 . The nitride layer  2521  can be constructed by using a sacrificial material such as glass to first fill the crystallographic etched nozzle chamber  2511  then depositing the nitride layer  2520 ,  2521  before etching the sacrificial layer away to release the nitride layer  2521 . On top of the nitride layer  2521  is formed a Terfenol-D layer  2522 . Terfenol-D is a material having high magnetostrictive properties (for further information on the properties of Terfenol-D, reference is made to “magnetostriction, theory and applications of magnetoelasticity” by Etienne du Trémolett de Lachiesserie published 1993 by CRC Press). Upon it being subject to a magnetic field, the Terfenol-D substance expands. The Terfenol-D layer  2522  is attached to a lower nitride layer  2521  which does not undergo expansion. As a result the forces are resolved by a bending of the nitride layer  2521  towards the nozzle ejection hole  2512  thereby causing the ejection of ink from the ink ejection portal  2512 . 
     The Terfenol-D layer  2522  is passivated by a top nitride layer  2523  on top of which is a copper coil layer  2524  which is interconnected to the lower CMOS layer  2517  via a series of vias so that copper coil layer  2524  can be activated upon demand. The activation of the copper coil layer  2524  induces a magnetic field across the Terfenol-D layer  2522  thereby causing the Terfenol-D layer  2522  to undergo phase change on demand. Therefore, in order to eject ink from the nozzle chamber  2511 , the Terfenol-D layer  2522  is activated to undergo phase change causing the bending of actuator  2526  ( FIG. 485 ) in the direction of the ink ejection port  2512  thereby causing the ejection of ink drops. Upon deactivation of the upper coil layer  2524  the actuator  2526  ( FIG. 485 ) returns to its quiescent position drawing some of the ink back into the nozzle chamber causing an ink ligament connecting the ink drop to the ink in the nozzle chamber to thin. The forward velocity of the drop and backward velocity of the ink in the nozzle chamber  2511  are resolved by the ink drop breaking off from the ink in the nozzle chamber  2511 . Ink refill of the nozzle chamber  2511  is via the sides of actuator  2526  ( FIG. 485 ) as a result of the surface tension of the ink meniscus at the ejection port  2512 . 
     The copper layer  2524  is passivated by a nitride layer (not shown) and the nozzle arrangement  2510  abuts an ink supply reservoir  2528  ( FIG. 485 ). 
     A method of ejecting ink from the nozzle chamber  2511  comprises providing the actuator  2526  formed of magnetostrictive material as a wall of the chamber  2511  and then effecting a phase transformation of the magnetostrictive material in the magnetic field by activating the copper coil layer  2524  (or vice versa). This in turn causes the ejection of ink from nozzle chamber  2511  via ejection port  2512 . 
     The actuator  2526  comprises a magnetostrictive paddle which transfers from the quiescent state as shown in  FIG. 485  to an ink ejection state upon application of the magnetic field. The actuator  2526  moves downwardly in the direction of the arrow shown in  FIG. 485  toward the ejection port  2512 . 
     The magnetic field is applied by passing a current through the copper coil layer  2524  adjacent to the actuator  2526 . The actuator  2526  as shown in  FIG. 485  forms one wall of the chamber  2511  opposite the ink ejection port  2512  from which ink is ejected. 
     The ink ejection port  2512  is formed by back etching a silicon wafer to an epitaxial layer and etching a nozzle portal in the epitaxial layer. The crystallographic etch provides side wall slots of non-etched layers of a processed silicon wafer so as to extend dimensionally chamber  2511  as a result of the crystallographic etch process. As a result, side walls of the chamber  2511  as shown in  FIG. 485  have an upwardly, outwardly tapered profile. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  2530  deposit 3 microns of epitaxial silicon  2513  heavily doped with boron. 
     2. Deposit 20 microns of epitaxial silicon  2516 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2517 ,  2518 . The metal layers are copper instead of aluminum, due to high current densities and subsequent high temperature processing. Relevant features of the wafer at this step are shown in  FIG. 488 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 487  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers down to silicon using Mask  1 . This mask defines the nozzle chamber  2511 . This step is shown in  FIG. 489 . 
     5. Deposit 1 micron of low stress PECVD silicon nitride (Si 3 N 4 )  2520 . 
     6. Deposit a seed layer of Terfenol-D. 
     7. Deposit 3 microns of resist  2531  and expose using Mask  2 . This mask defines the actuator beams. The resist forms a mold for electroplating of the Terfenol-D. This step is shown in  FIG. 490 . 
     8. Electroplate 2 microns of Terfenol-D  2522 . 
     9. Strip the resist and etch the seed layer. This step is shown in  FIG. 491 . 
     10. Etch the nitride layer  2520  using Mask  3 . This mask defines the actuator beams and the nozzle chamber  2511 , as well as the contact vias from the solenoid coil  2524  to the second-level metal contacts. This step is shown in  FIG. 492 . 
     11. Deposit a seed layer of copper. 
     12. Deposit 22 microns of resist  2532  and expose using Mask  4 . This mask defines the solenoid, and should be exposed using an x-ray proximity mask, as the aspect ratio is very large. The resist forms a mold for electroplating of the copper. This step is shown in  FIG. 493 . 
     13. Electroplate 20 microns of copper  2533 . 
     14. Strip the resist and etch the copper seed layer. Steps 10 to 13 form a LIGA process. This step is shown in  FIG. 494 . 
     15. Crystallographically etch the exposed silicon using, for example, KOH or EDP (ethylenediamine pyrocatechol). This etch stops on &lt;111&gt; crystallographic planes, and on the boron doped silicon buried layer  2513 . This step is shown in  FIG. 495 . 
     16. Deposit 0.1 microns of ECR diamond like carbon (DLC) as a corrosion barrier (not shown). 
     17. Open the bond pads using Mask  5 . 
     18. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     19. Mount the wafer  2516  on a glass blank  2534  and back-etch the wafer  2516  using KOH with no mask. This etch tins the wafer  2516  and stops at the buried boron doped silicon layer  2513 . This step is shown in  FIG. 496 . 
     20. Plasma back-etch the boron doped silicon layer  2513  to a depth of 1 micron using Mask  6 . This mask defines the nozzle rim  2515 . This step is shown in  FIG. 497 . 
     21. Plasma back-etch through the boron doped layer  2513  using Mask  6 . This mask defines the nozzle  2512 , and the edge of the chips. Etch the thin ECR DLC layer through the nozzle hole  2512 . This step is shown in  FIG. 498 . 
     22. Strip the adhesive layer to detach the chips from the glass blank  2534 . 
     23. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     24. Connect the printheads to their interconnect systems. 
     25. Hydrophobize the front surface of the printheads. 
     26. Fill the completed printheads with ink  2535  and test them. A filled nozzle is shown in  FIG. 499 . 
     IJ26 
     In a preferred embodiment, shape memory materials are utilized to construct an actuator suitable for injecting ink from the nozzle of an ink chamber. 
     Turning to  FIG. 500 , there is illustrated an exploded perspective view of a single ink jet nozzle  2610  as constructed in accordance with a preferred embodiment. The ink jet nozzle  2610  is constructed from a silicon wafer base utilizing back etching of the wafer to a boron doped epitaxial layer. Hence, the ink jet nozzle  2610  comprises a lower layer  2611  which is constructed from boron doped silicon. The boron doped silicon layer is also utilized a crystallographic etch stop layer. The next layer comprises the silicon layer  2612  that includes a crystallographic pit  2613  having side walls etch at the usual angle of 54.74 degrees. The layer  2612  also includes the various required circuitry and transistors for example, CMOS layer (not shown). After this, a 0.5 micron thick thermal silicon oxide layer  2615  is grown on top of the silicon wafer  2612 . 
     After this, comes various layers which can comprise a two level metal CMOS process layers which provide the metal interconnect for the CMOS transistors formed within the layer  2612 . The various metal pathways etc. are not shown in  FIG. 500  but for two metal interconnects  2618 ,  2619  which provide interconnection between a shape memory alloy layer  2620  and the CMOS metal layers  2616 . The shape memory metal layer is next and is shaped in the form of a serpentine coil to be heated by end interconnect/via portions  2621 ,  2623 . A top nitride layer  2622  is provided for overall passivation and protection of lower layers in addition to providing a means of inducing tensile stress to curl upwards the shape memory alloy layer  2620  in its quiescent state. 
     A preferred embodiment relies upon the thermal transition of a shape memory alloy  2620  (SMA) from its martensitic phase to its austenitic phase. The basis of a shape memory effect is a martensitic transformation which creates a polydemane phase upon cooling. This polydemane phase accommodates finite reversible mechanical deformations without significant changes in the mechanical self energy of the system. Hence, upon re-transformation to the austenitic state the system returns to its former macroscopic state to displaying the well known mechanical memory. The thermal transition is achieved by passing an electrical current through the SMA. The actuator layer  2620  is suspended at the entrance to a nozzle chamber connected via leads  2618 ,  2619  to the lower layers. 
     In  FIG. 501 , there is shown a cross-section of a single nozzle  2610  when in its actuated state, the section basically being taken through the line A-A of  FIG. 500 . The actuator  2630  is bent away from the nozzle when in its actuated state. In  FIG. 502 , there is shown a corresponding cross-section for a single nozzle  2610  when in a quiescent state. When energized, the actuator  2630  straightens, with the corresponding result that the ink is pushed out of the nozzle. The process of energizing the actuator  2630  requires supplying enough energy to raise the SMA above its transition temperature, and to provide the latent heat of transformation to the SMA  2620 . 
     Obviously, the SMA martensitic phase must be pre-stressed to achieve a different shape from the austenitic phase. For printheads with many thousands of nozzles, it is important to achieve this pre-stressing in a bulk manner. This is achieved by depositing the layer of silicon nitride  2622  using Plasma Enhanced Chemical Vapour Deposition (PECVD) at around 300° C. over the SMA layer. The deposition occurs while the SMA is in the austenitic shape. After the printhead cools to room temperature the substrate under the SMA bend actuator is removed by chemical etching of a sacrificial substance. The silicon nitride layer  2622  is under tensile stress, and causes the actuator to curl upwards. The weak martensitic phase of the SMA provides little resistance to this curl. When the SMA is heated to its austenitic phase, it returns to the flat shape into which it was annealed during the nitride deposition. The transformation being rapid enough to result in the ejection of ink from the nozzle chamber. 
     There is one SMA bend actuator  2630  for each nozzle. One end  2631  of the SMA bend actuator is mechanically connected to the substrate. The other end is free to move under the stresses inherent in the layers. 
     Returning to  FIG. 500  the actuator layer is therefore composed of three layers: 
     1. An SiO 2  lower layer  2615 . This layer acts as a stress ‘reference’ for the nitride tensile layer. It also protects the SMA from the crystallographic silicon etch that forms the nozzle chamber. This layer can be formed as part of the standard CMOS process for the active electronics of the printhead. 
     2. A SMA heater layer  2620 . A SMA such as nickel titanium (NiTi) alloy is deposited and etched into a serpentine form to increase the electrical resistance. 
     3. A silicon nitride top layer  2622 . This is a thin layer of high stiffness which is deposited using PECVD. The nitride stoichiometry is adjusted to achieve a layer with significant tensile stress at room temperature relative to the SiO 2  lower layer. Its purpose is to bend the actuator at the low temperature martensitic phase. 
     As noted previously the ink jet nozzle of  FIG. 500  can be constructed by utilizing a silicon wafer having a buried boron epitaxial layer. The 0.5 micron thick dioxide layer  2615  is then formed having side slots  2645  which are utilized in a subsequent crystallographic etch. Next, the various CMOS layers  2616  are formed including drive and control circuitry (not shown). The SMA layer  2620  is then created on top of layers  2615 / 2616  and being interconnected with the drive circuitry. Subsequently, a silicon nitride layer  2622  is formed on top. Each of the layers  2615 ,  2616 ,  2622  include the various slots e.g.  2645  which are utilized in a subsequent crystallographic etch. The silicon wafer is subsequently thinned by means of back etching with the etch stop being the boron layer  2611 . Subsequent boron etching forms the nozzle hole e.g.  2647  and rim  2646  ( FIG. 502 ). Subsequently, the chamber proper is formed by means of a crystallographic etch with the slots  2645  defining the extent of the etch within the silicon oxide layer  2612 . 
     A large array of nozzles can be formed on the same wafer which in turn is attached to an ink chamber for filling the nozzle chambers. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  2650  deposit 3 microns of epitaxial silicon heavily doped with boron  2611 . 
     2. Deposit 10 microns of epitaxial silicon  2612 , either p-type or n-type, depending upon the CMOS process used. 
     3. Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2616 . This step is shown in  FIG. 504 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 503  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     4. Etch the CMOS oxide layers down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber, and the edges of the printheads chips. This step is shown in  FIG. 505 . 
     5. Crystallographically etch the exposed silicon using, for example, KOH or EDP (ethylenediamine pyrocatechol). This etch stops on &lt;111&gt; crystallographic planes  2651 , and on the boron doped silicon buried layer. This step is shown in  FIG. 506 . 
     6. Deposit 12 microns of sacrificial material  2652 . Planarize down to oxide using CMP. The sacrificial material temporarily fills the nozzle cavity. This step is shown in  FIG. 507 . 
     7. Deposit 0.1 microns of high stress silicon nitride (Si 3 N 4 ). 
     8. Etch the nitride layer using Mask  2 . This mask defines the contact vias from the shape memory heater to the second-level metal contacts. 
     9. Deposit a seed layer. 
     10. Spin on 2 microns of resist  2653 , expose with Mask  3 , and develop. This mask defines the shape memory wire embedded in the paddle. The resist acts as an electroplating mold. This step is shown in  FIG. 508 . 
     11. Electroplate 1 micron of Nitinol  2655 . Nitinol is a ‘shape memory’ alloy of nickel and titanium, developed at the Naval Ordnance Laboratory in the US (hence Ni—Ti—NOL). A shape memory alloy can be thermally switched between its weak martensitic state and its high stiffness austenic state. 
     12. Strip the resist and etch the exposed seed layer. This step is shown in  FIG. 509 . 
     13. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     14. Deposit 0.1 microns of high stress silicon nitride. High stress nitride is used so that once the sacrificial material is etched, and the paddle is released, the stress in the nitride layer will bend the relatively weak martensitic phase of the shape memory alloy. As the shape memory alloy—in its austenic phase—is flat when it is annealed by the relatively high temperature deposition of this silicon nitride layer, it will return to this flat state when electrothermally heated. 
     15. Mount the wafer on a glass blank  2656  and back-etch the wafer using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in  FIG. 510 . 
     16. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask  4 . This mask defines the nozzle rim  2646 . This step is shown in  FIG. 511 . 
     17. Plasma back-etch through the boron doped layer using Mask  5 . This mask defines the nozzle  2647 , and the edge of the chips. At this stage, the chips are still mounted on the glass blank. This step is shown in  FIG. 512 . 
     18. Strip the adhesive layer to detach the chips from the glass blank. Etch the sacrificial layer. This process completely separates the chips. This step is shown in  FIG. 513 . 
     19. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer. 
     20. Connect the printheads to their interconnect systems. 
     21. Hydrophobize the front surface of the printheads. 
     22. Fill with ink  2658  and test the completed printheads. A filled nozzle is shown in  FIG. 514 . 
     IJ27 
     In a preferred embodiment, a “roof shooting” ink jet printhead is constructed utilizing a buckle plate actuator for the ejection of ink. In a preferred embodiment, the buckle plate actuator is constructed from polytetrafluoroethylene (PTFE) which provides superior thermal expansion characteristics. The PTFE is heated by an integral, serpentine shaped heater, which preferably is constructed from a resistive material, such as copper. 
     Turning now to  FIG. 515  there is shown a sectional perspective view of an ink jet printhead  2701  of a preferred embodiment. The ink jet printhead includes a nozzle chamber  2702  in which ink is stored to be ejected. The chamber  2702  can be independently connected to an ink supply (not shown) for the supply and refilling of the chamber. At the base of the chamber  2702  is a buckle plate  2703  which comprises a heater element  2704  which can be of an electrically resistive material such as copper. The heater element  2704  is encased in a polytetrafluoroethylene layer  2705 . The utilization of the PTFE layer  2705  allows for high rates of thermal expansion and therefore more effective operation of the buckle plate  2703 . PTFE has a high coefficient of thermal expansion (770×10 −6 ) with the copper having a much lower degree of thermal expansion. The copper heater element  2704  is therefore fabricated in a serpentine pattern so as to allow the expansion of the PTFE layer to proceed unhindered. The serpentine fabrication of the heater element  2704  means that the two coefficients of thermal expansion of the PTFE and the heater material need not be closely matched. The PTFE is primarily chosen for its high thermal expansion properties. 
     Current can be supplied to the buckle plate  2703  by means of connectors  2707 ,  2708  which inter-connect the buckle plate  2703  with a lower drive circuitry and logic layer  2726 . Hence, to operate the ink jet head  2701 , the heater coil  2704  is energized thereby heating the PTFE  2705 . The PTFE  2705  expands and buckles between end portions  2712 ,  2713 . The buckle causes initial ejection of ink out of a nozzle  2715  located at the top of the nozzle chamber  2702 . There is an air bubble between the buckle plate  2703  and the adjacent wall of the chamber which forms due to the hydrophobic nature of the PTFE on the back surface of the buckle plate  2703 . An air vent  2717  connects the air bubble to the ambient air through a channel  2718  formed between a nitride layer  2719  and an additional PTFE layer  2720 , separated by posts, e.g.  2721 , and through holes, e.g.  2722 , in the PTFE layer  2720 . The air vent  2717  alloy buckle plate  2703  to move without being held back by a reduction in air pressure as the buckle plate  2703  expands. Subsequently, power is turned off to the buckle plate  2703  resulting in a collapse of the buckle plate and the sucking back of some of the ejected ink. The forward motion of the ejected ink and the sucking back is resolved by an ink drop breaking off from the main volume of ink and continuing onto a page. Ink refill is then achieved by surface tension effects across the nozzle part  2715  and a resultant inflow of ink into the nozzle chamber  2702  through the grilled supply channel  2716 . 
     Subsequently the nozzle chamber  2702  is ready for refiring. 
     It has been found in simulations of a preferred embodiment that the utilization of the PTFE layer and serpentine heater arrangement allows for a substantial reduction in energy requirements of operation in addition to a more compact design. 
     Turning now to  FIG. 516 , there is provided an exploded perspective view partly in section illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment. The nozzle arrangement  2701  is fabricated on top of a silicon wafer  2725 . The nozzle arrangement  2701  can be constructed on the silicon wafer  2725  utilizing standard semi-conductor processing techniques in addition to those techniques commonly used for the construction of micro-electro-mechanical systems (MEMS). 
     On top of the silicon layer  2725  is deposited a two level CMOS circuitry layer  2726  which substantially comprises glass, in addition to the usual metal layers. Next a nitride layer  2719  is deposited to protect and passivate the underlying layer  2726 . The nitride layer  2719  also includes vias for the interconnection of the heater element  2704  to the CMOS layer  2726 . Next, a PTFE layer  2720  is constructed having the aforementioned holes, e.g.  2722 , and posts, e.g.  2721 . The structure of the PTFE layer  2720  can be formed by first laying down a sacrificial glass layer (not shown) onto which the PTFE layer  2720  is deposited. The PTFE layer  2720  includes various features, for example, a lower ridge portion  2727  in addition to a hole  2728  which acts as a via for the subsequent material layers. The buckle plate  2703  ( FIG. 515 ) comprises a conductive layer  2731  and a PTFE layer  2732 . A first, thicker PTFE layer is deposited onto a sacrificial layer (not shown). Next, a conductive layer  2731  is deposited including contacts  2729 ,  2730 . The conductive layer  2731  is then etched to form a serpentine pattern. Next, a thinner, second PTFE layer is deposited to complete the buckle plate  2703  ( FIG. 515 ) structure. 
     Finally, a nitride layer can be deposited to form the nozzle chamber proper. The nitride layer can be formed by first laying down a sacrificial glass layer and etching this to form walls, e.g.  2733 , and grilled portions, e.g.  2734 . Preferably, the mask utilized results in a first anchor portion  2735  which mates with the hole  2728  in layer  2720 . Additionally, the bottom surface of the grill, for example  2734  meets with a corresponding step  2736  in the PTFE layer  2732 . Next, a top nitride layer  2737  can be formed having a number of holes, e.g.  2738 , and nozzle port  2715  around which a rim  2739  can be etched through etching of the nitride layer  2737 . Subsequently the various sacrificial layers can be etched away so as to release the structure of the thermal actuator and the air vent channel  2718  ( FIG. 515 ). 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  2725 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2726 . Relevant features of the wafer  2725  at this step are shown in  FIG. 518 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 517  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Deposit 1 micron of low stress nitride  2719 . This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface. 
     3. Deposit 2 microns of sacrificial material  2750  (e.g. polyimide). 
     4. Etch the sacrificial layer  2750  using Mask  1 . This mask defines the PTFE venting layer support pillars  2721  ( FIG. 515 ) and anchor point. This step is shown in  FIG. 519 . 
     5. Deposit 2 microns of PTFE  2720 . 
     6. Etch the PTFE  2720  using Mask  2 . This mask defines the edges of the PTFE venting layer, and the holes  2722  in this layer  2720 . This step is shown in  FIG. 520 . 
     7. Deposit 3 microns of sacrificial material  2751 . 
     8. Etch the sacrificial layer  2751  using Mask  3 . This mask defines the anchor points  2712 ,  2713  at both ends of the buckle actuator. This step is shown in  FIG. 521 . 
     9. Deposit 1.5 microns of PTFE  2731 . 
     10. Deposit and pattern resist using Mask  4 . This mask defines the heater. 
     11. Deposit 0.5 microns of gold  2704  (or other heater material with a low Young&#39;s modulus) and strip the resist. Steps 10 and 11 form a lift-off process. This step is shown in  FIG. 522 . 
     12. Deposit 0.5 microns of PTFE  2732 . 
     13. Etch the PTFE  2732  down to the sacrificial layer  2751  using Mask  5 . This mask defines the actuator paddle  2703  (See  FIG. 515 ) and the bond pads. This step is shown in  FIG. 523 . 
     14. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated. 
     15. Plasma process the PTFE to make the top and side surfaces of the buckle actuator hydrophilic. This allows the nozzle chamber to fill by capillarity. 
     16. Deposit 10 microns of sacrificial material  2752 . 
     17. Etch the sacrificial material  2752  down to nitride  2719  using Mask  6 . This mask defines the nozzle chamber  2702 . This step is shown in  FIG. 524 . 
     18. Deposit 3 microns of PECVD glass  2737 . This step is shown in  FIG. 525 . 
     19. Etch to a depth of 1 micron using Mask  7 . This mask defines the nozzle rim  2739 . This step is shown in  FIG. 526 . 
     20. Etch down to the sacrificial layer  2752  using Mask  8 . This mask defines the nozzle  2715  and the sacrificial etch access holes  2738 . This step is shown in  FIG. 527 . 
     21. Back-etch completely through the silicon wafer  2725  (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  9 . This mask defines the ink inlets  2753  which are etched through the wafer  2725 . The wafer  2725  is also diced by this etch. This step is shown in  FIG. 528 . 
     22. Back-etch the CMOS oxide layers  2726  and subsequently deposited nitride layers  2719  and sacrificial layer  2750 ,  2751  through to PTFE  2720 ,  2732  using the back-etched silicon as a mask. 
     23. Etch the sacrificial material  2752 . The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 529 . 
     24. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     25. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     26. Hydrophobize the front surface of the printheads. 
     27. Fill the completed printheads with ink  2754  and test them. A filled nozzle is shown in  FIG. 530 . 
     IJ28 
     In a preferred embodiment, a thermal actuator is utilized to activate a set of “vanes” so as to compress a volume of ink and thereby force ink out of an ink nozzle. 
     Turning to  FIG. 531 , there is illustrated an exploded perspective view of a single inkjet nozzle  2801 . A preferred embodiment fundamentally comprises a series of vane chambers  2802  which are normally filled with ink. The vane chambers  2802  include side walls which define static vanes  2803  each having a first radial wall  2805  and a second circumferential wall  2806 . A set of “impeller vanes”  2807  is also provided which each have a radially aligned surface and are attached to rings  2809 ,  2810  with the inner ring  2809  being pivotally mounted around a pivot unit  2812 . The outer ring  2810  is also rotatable about the pivot point  2812  and is interconnected with thermal actuators  2813 ,  2822 . The thermal actuators  2813 ,  2822  are of a circumferential form and undergo expansion and contraction thereby rotating the impeller vanes  2807  towards the radial wall  2805  of the static vanes  2803 . As a consequence the vane chamber  2802  undergoes a rapid reduction in volume thereby resulting in a substantial increase in pressure resulting in the expulsion of ink from the chamber  2802 . 
     The static vane  2803  is attached to a nozzle plate  2815 . The nozzle plate  2815  includes a nozzle rim  2816  defining an aperture  2814  into the vane chambers  2802 . The aperture  2814  defined by rim  2816  allows for the injection of ink from the vane chambers  2802  onto the relevant print media. 
       FIG. 532  shows a perspective view taken from above of relevant portions of an ink jet nozzle arrangement  2801 , constructed in accordance with a preferred embodiment. The outer ring  2810  is interconnected at points  2820 ,  2821  to thermal actuators  2813 ,  2822 . The thermal actuators  2813 ,  2822  include inner resistive elements  2824 ,  2825  which are constructed from copper or the like. Copper has a low coefficient of thermal expansion and is therefore constructed in a serpentine manner, so as to allow for greater expansion in the radial direction  2828 . The inner resistive elements  2824 ,  2825  are each encased in an outer jacket  2826  of a material having a high coefficient of thermal expansion. Suitable material includes polytetrafluoroethylene (PTFE) which has a high coefficient of thermal expansion (770×10 −6 ). The thermal actuators  2813 ,  2822  is anchored at the points  2827  to a lower layer of the wafer. The anchor points  2827  also form an electrical connection with a relevant drive line of the lower layer. The resistive elements  2824 ,  2825  are also electronically connected at  2820 ,  2821  to the outer ring  2810 . Upon activation of the resistive element  2824 ,  2825 , the outer jacket  2826  undergoes rapid expansion which includes the expansion of the serpentine resistive elements  2824 ,  2825 . The rapid expansion and subsequent contraction on de-energizing the resistive elements  2824 ,  2825  results in a rotational force in the direction  2828  being induced in the ring  2810 . The rotation of the ring  2810  causes a corresponding rotation in the relevant impeller vanes  2807  ( FIG. 531 ). Hence, by the activation of the thermal actuators  2813 ,  2822 , ink can be ejected out of the nozzle aperture  2814  ( FIG. 531 ). 
     Turning now to  FIG. 533 , there is illustrated a cross-sectional view through a single nozzle arrangement. The illustration of  FIG. 533  shows a drop  2831  being ejected out of the nozzle aperture  2814  as a result of displacement of the impeller vanes  2807  ( FIG. 531 ). The nozzle arrangement  2801  is constructed on a silicon wafer  2833 . Electronic drive circuitry  2834  is first constructed for control and driving of the thermal actuators  2813 ,  2822 . A silicon dioxide layer  2835  is provided for defining the nozzle chamber which includes channel walls separating ink of one color from an adjacent ink reservoirs (not shown). The nozzle plate  2815 , is also interconnected to the wafer  2833  via nozzle plate posts,  2837  so as to provide for stable separation from the wafer  2833 . The static vanes  2803  are constructed from silicon nitrate as is the nozzle plate  2815 . The static vanes  2803  and nozzle plate  2815  can be constructed utilizing a dual damascene process utilizing a sacrificial layer as discussed further hereinafter. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads including a plane of the nozzle arrangement  2801  can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  2833 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2834 . Relevant features of the wafer at this step are shown in  FIG. 535 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle arrangement  2801 .  FIG. 534  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Deposit 1 micron of low stress nitride  2835 . This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface. 
     3. Deposit 2 microns of sacrificial material  2850 . 
     4. Etch the sacrificial layer using Mask  1 . This mask defines the axis pivot  2812  and the anchor points  2827  of the actuators. This step is shown in  FIG. 536 . 
     5. Deposit 1 micron of PTFE  2851 . 
     6. Etch the PTFE down to top level metal using Mask  2 . This mask defines the heater contact vias. This step is shown in  FIG. 537 . 
     7. Deposit and pattern resist using Mask  3 . This mask defines the heater, the vane support wheel, and the axis pivot. 
     8. Deposit 0.5 microns of gold  2852  (or other heater material with a low Young&#39;s modulus) and strip the resist Steps 7 and 8 form a lift-off process. This step is shown in  FIG. 538 . 
     9. Deposit 1 micron of PTFE  2853 . 
     10. Etch both layers of PTFE down to the sacrificial material using Mask  4 . This mask defines the actuators and the bond pads. This step is shown in  FIG. 539 . 
     11. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated. 
     12. Deposit 10 microns of sacrificial material  2855 . 
     13. Etch the sacrificial material down to heater material or nitride using Mask  5 . This mask defines the nozzle plate support posts and the moving vanes, and the walls surrounding each ink color. This step is shown in  FIG. 540 . 
     14. Deposit a conformal layer of a mechanical material and planarize to the level of the sacrificial layer. This material may be PECVD glass, titanium nitride, or any other material which is chemically inert, has reasonable strength, and has suitable deposition and adhesion characteristics. This step is shown in  FIG. 541 . 
     15. Deposit 0.5 microns of sacrificial material  2856 . 
     16. Etch the sacrificial material to a depth of approximately 1 micron above the heater material using Mask  6 . This mask defines the fixed vanes  2803  and the nozzle plate support posts, and the walls surrounding each ink color. As the depth of the etch is not critical, it may be a simple timed etch. 
     17. Deposit 3 microns of PECVD glass  2858 . This step is shown in  FIG. 542 . 
     18. Etch to a depth of 1 micron using Mask  7 . This mask defines the nozzle rim  2816 . This step is shown in  FIG. 543 . 
     19. Etch down to the sacrificial layer using Mask  8 . This mask defines the nozzle  2814  and the sacrificial etch access holes  2817 . This step is shown in  FIG. 544 . 
     20. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  9 . This mask defines the ink inlets  2860  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 545 . 
     21. Back-etch the CMOS oxide Jayers and subsequently deposited nitride layers through to the sacrificial layer using the back-etched silicon as a mask. 
     22. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 546 . 
     23. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     24. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     25. Hydrophobize the front surface of the printheads. 
     26. Fill the completed printheads with ink  2861  and test them. A filled nozzle is shown in  FIG. 547 . 
     IJ29 
     In a preferred embodiment, a new form of thermal actuator is utilized for the ejection of drops of ink on demand from an ink nozzle. Turning now to  FIGS. 548 to 551 , there will be illustrated the basis of operation of the inkjet printing device utilizing the actuator. Turning initially to  FIG. 548 , there is illustrated  2901 , the quiescent position of a thermal actuator  2902  in a nozzle chamber  2903  filled with ink and having a nozzle  2904  for the ejection of ink. The nozzle  2904  has an ink meniscus  2905  in a state of surface tension ready for the ejection of ink. The thermal actuator  2902  is coated on a first surface  2906 , facing the chamber  2903 , with a hydrophilic material. A second surface  2907  is coated with a hydrophobic material which causes an air bubble  2908  having a meniscus  2909  underneath the actuator  2902 . The air bubble  2908  is formed over time by outgassing from the ink within chamber  2903  and the meniscus  2909  is shown in an equilibrium position between the hydrophobic  2907  and hydrophilic  2906  surfaces. The actuator  2902  is fixed at one end  2911  to a substrate  2912  from which it also derives an electrical connection. 
     When it is desired to eject a drop from the nozzle  2904 , the actuator  2902  is activated as shown in  FIG. 549 , resulting in a movement in direction  2914 , the movement in direction  2914  causes a substantial increase in the pressure of the ink around the nozzle  2904 . This results in a general expansion of the meniscus  2905  and the passing of momentum to the ink so as to form a partial drop  2915 . Upon movement of the actuator  2902  in the direction  2914 , the ink meniscus  2909  collapses generally in the indicated direction  2916 . 
     Subsequently, the thermal actuator  2902  is deactivated as illustrated in  FIG. 550 , resulting in a return of the actuator  2902  in the direction generally indicated by the arrow  2917 . The movement back of the actuator  2917  results in a low pressure region being experienced by the ink within the nozzle area  2904 . The forward momentum of the drop  2915  and the low pressure around the nozzle  2904  results in the ink drop  2915  being broken off from the main body of the ink. The drop  2915  continues to the print media as required. The movement of the actuator  2902  in the direction  2917  further causes ink to flow in the direction  2919  around the actuator  2902  in addition to causing the meniscus  2909  to move as a result of the ink flow  2919 . Further, further ink  2920  is sucked into the chamber  2903  to refill the ejected ink  2915 . 
     Finally, as illustrated in  FIG. 551 , the actuator  2902  returns to its quiescent position with the meniscus  2905  also returning to a state of having a slight bulge. The actuator  2902  is then in a state for refiring of another drop on demand as required. 
     In one form of implementation of an inkjet printer utilizing the method illustrated in  FIGS. 548 to 551 , standard semi-conductive fabrication techniques are utilized in addition to standard micro-electro-mechanical (MEMS) techniques construct a suitable print device having a polarity of the chambers as illustrated in  FIG. 548  with corresponding actuators  2902 . 
     Turning now to  FIG. 552 , there is illustrated a cross-section through one form of suitable nozzle chamber. A group of such ink jet nozzles is shown in  FIG. 553 . One end  2911  of the actuator  2902  is connected to the substrate  2912  and the other end includes a stiff paddle  2925  for use in ejecting ink. The actuator itself is constructed from a four layer MEMS processing technique. The layers are as follows: 
     1. A polytetrafluoroethylene (PTFE) lower layer  2926 . PTFE has a very high coefficient of thermal expansion (approximately 770×10 −6 , or around 380 times that of silicon). This layer expands when heated by a heater layer. 
     2. A heater layer  2927 . A serpentine heater  2927  is etched in this layer, which may be formed from nichrome, copper or other suitable material with a resistivity such that the drive voltage for the heater is compatible with the drive transistors utilized. The serpentine heater  2927  is arranged to have very little tensile strength in the direction  2929  along the length of the actuator. 
     3. A PTFE upper layer  2930 . This layer  2930  expands when heated by the heater layer. 
     4. A silicon nitride layer  2932 . This is a thin layer  2932  is of high stiffness and low coefficient of thermal expansion. Its purpose is to ensure that the actuator bends, instead of simply elongating as a result of thermal expansion of the PTFE layers. Silicon nitride can be used simply because it is a standard semi-conductor material, and SiO 2  cannot easily be used if it is also the sacrificial material used when constructing the device. 
     Operation of the ink jet actuator  2902  will then be as follows: 
     1. When data signals distributed on the print-head indicate that a particular nozzle is to eject a drop of ink the drive transistor for that nozzle is turned on. This energises the heater  2927  in the paddle for that nozzle. The heater is energised for approximately 2 microseconds, with the actual duration depending upon the exact design chosen for the actuator nozzle and the inks utilized. 
     2. The heater  2927  heats the PTFE layers  2926 ,  2930  which expand at a rate many times that of the Si 3 N 4  layer  2932 . This expansion causes the actuator  2902  to bend, with the PTFE layer  2926  being the convex side. The bending of the actuator moves the paddle, pushing ink out of the nozzle. The air bubble  2908  ( FIG. 548 ) between the paddle and the substrate, forms due to the hydrophobic nature of the PTFE on the back surface of the paddle. This air bubble reduces the thermal coupling to the hot side of the actuator, achieving a higher temperature with lower power. The cold side of the actuator including SiN layer  2932  will still be water cooled. The air bubble will also expand slightly when heated, helping to move the paddle. The presence of the air bubble also means that less ink is required to move under the paddle when the actuator is energised. These three factors lead to a lower power consumption of the actuator. 
     3. When the heater current is turned off, as noted previously, the paddle  2925  begins to return to its quiescent position. The paddle return ‘sucks’ some of the ink back into the nozzle, causing the ink ligament connecting the ink drop to the ink in the nozzle to thin. The forward velocity of the drop and the backward velocity of the ink in the chamber are resolved by the ink drop breaking off from the ink in the nozzle. The ink drop then continues towards the recording medium. 
     4. The actuator  2902  is finally at rest in the quiescent position until the next drop ejection cycle. 
     Basic Fabrications Sequence 
     One form of print-head fabrication sequence utilizing MEMS technology will now be described. The description assumes that the reader is familiar with surface and micromachining techniques utilized for the construction of MEMS devices, including the latest proceedings in these areas. Turning now to  FIG. 554 , there is illustrated an exploded perspective view of a single ink jet nozzle as constructed in accordance with a preferred embodiment. The construction of a print-head can proceed as follows: 
     1. Start with a standard single crystal silicon wafer  2980  suitable for the desired manufacturing process of the active semiconductor device technology chosen. Here the manufacturing process is assumed to be 0.5 microns CMOS. 
     2. Complete fabrication the CMOS circuitry layer  2983 , including an oxide layer (not shown) and passivation layer  2982  for passivation of the wafer. As the chip will be immersed in water based ink, the passivation layer must be highly impervious. A layer of high density silicon nitride (Si 3 N 4 ) is suitable. Another alternative is diamond-like carbon (DLC). 
     3. Deposit 2 micron of phosphosilicate glass (PSG). This will be a sacrificial layer which raises the actuator and paddle from the substrate. This thickness is not critical. 
     4. Etch the PSG to leave islands under the actuator positions on which the actuators will be formed. 
     5. Deposit 1.0 micron of polytetrafluoroethylene (PTFE) layer  2984 . The PTFE may be roughened to promote adhesion. The PTFE may be deposited as a spin-on nanoemulsion. [T. Rosenmayer, H. Wu, “PTFE nanoemulsions as spin-on, low dielectric constant materials for ULSI applications”, PP463-468, Advanced Metallisation for Future ULSI, MRS vol. 427, 1996]. 
     6. Mask and etch via holes through to the top level metal of the CMOS circuitry for connection of a power supply to the actuator (not shown). Suitable etching procedures for PTFE are discussed in “Thermally assisted Ian Beam Etching of polytetrafluoroethylene: A new technique for High Aspect Ratio Etching of MEMS” by Berenschot et al in the Proceedings of the Ninth Annual International Workshop on Micro Electro Mechanical Systems, San Diego, February 1996. 
     7. Deposit the heater material layer  2985 . This may be Nichrome (an alloy of 80% nickel and 20% chromium) which may be deposited by sputtering. Many other heater materials may be used. The principal requirements are a resistivity which results in a drive voltage which is suitable for the CMOS drive circuitry layer, a melting point above the temperature of subsequent process steps, electromigration resistance, and appropriate mechanical properties. 
     8. Etch the heater material using a mask pattern of the heater and the paddle stiffener. 
     9. Deposit 2.0 micron of PTFE. As with step  5 , the PTFE may be spun on as a nanoemulsion, and may be roughened to promote adhesion. (This layer forms part of layer  2984  in  FIG. 554 .) 
     10. Deposit via a mask 0.25 of silicon nitride for the top of the layer  2986  of the actuator, or any of a wide variety of other materials having suitable properties as previously described. The major materials requirements are: a low coefficient of thermal expansion compared to PTFE; a relatively high Young&#39;s modulus, does not corrode in water, and a low etch rate in hydrofluoric acid (HF). The last of these requirements is due to the subsequent use of HF to etch the sacrificial glass layers. If a different sacrificial layer is chosen, then this layer should obviously have resistance to the process used to remove the sacrificial material. 
     11. Using the silicon nitride as a mask, etch the PTFE, PTFE can be etched with very high selectivity (&gt;1,000 to one) with ion beam etching. The wafer may be tilted slightly and rotated during etching to prevent the formation of microglass. Both layers of PTFE can be etched simultaneously. 
     12. Deposit 20 micron of SiO 2 . This may be deposited as spin-on glass (SOG) and will be used as a sacrificial layer (not shown). 
     13. Etch through the glass layer using a mask defining the nozzle chamber and ink channel walls, e.g.  2951 , and filter posts, e.g.  2952 . This etch is through around 20 micron of glass, so should be highly anisotropic to minimise the chip area required. The minimum line width is around 6 microns, so coarse lithography may be used. Overlay alignment error should preferably be less than 0.5 microns. The etched areas are subsequently filled by depositing silicon nitride through the mask. 
     14. Deposit 2 micron of silicon nitride layer  2987 . This forms the front surface of the print-head. Many other materials could be used. A suitable material should have a relatively high Young&#39;s modulus, not corrode in water, and have a low etch rate in hydrofluoric acid (HF). It should also be hydrophilic. 
     15. Mask and etch nozzle rims (not shown). These are 1 micron annular protrusions above the print-head surface around the nozzles, e.g.  2904 , which help to prevent ink flooding the surface of the print-head. They work in conjunction with the hydrophobizing of the print-head front surface. 
     16. Mask and etch the nozzle holes  2904 . This mask also includes smaller holes, e.g.  2947 , which are placed to allow the ingress of the etchant for the sacrificial layers. These holes should be small enough to that the ink surface tension ensures that ink is not ejected from the holes when the ink pressure waves from nearby actuated nozzles is at a maximum. Also, the holes should be small enough to ensure that air bubbles are not ingested at times of low ink pressure. These holes are spaced close enough so that etchant can easily remove all of the sacrificial material even though the paddle and actuator are fairly large and flexible, stiction should not be a problem for this design. This is because the paddle is made from PTFE. 
     17. Etch ink access holes (not shown) through the wafer  2980 . This can be done as an anisotropic crystallographic silicon etch, or an anisotropic dry etch. A dry etch system capable of high aspect ratio deep silicon trench etching such as the Surface Technology Systems (STS) Advance Silicon Etch (ASE) system is recommended for volume production, as the chip size can be reduced over wet etch. The wet etch is suitable for small volume production, as the chip size can be reduced over wet etch. The wet etch is suitable for small volume production where a suitable plasma etch system is not available. Alternatively, but undesirably, ink access can be around the sides of the print-head chips. If ink access is through the wafer higher ink flow is possible, and there is less requirement for high accuracy assembly. If ink access is around the edge of the chip, ink flow is severely limited, and the print-head chips must be carefully assembled onto ink channel chips. This latter process is difficult due to the possibility of damaging the fragile nozzle plate. If plasma etching is used, the chips can be effectively diced at the same time. Separating the chips by plasma etching allows them to be spaced as little as 35 micron apart, increasing the number of chips on a wafer. At this stage, the chips must be handled carefully, as each chip is a beam of silicon 100 mm long by 0.5 mm wide and 0.7 mm thick. 
     18. Mount the print-head chips into print-head carriers. These are mechanical support and ink connection mouldings. The print-head carriers can be moulded from plastic, as the minimum dimensions are 0.5 mm. 
     19. Probe test the print-heads and bond the good print-heads. Bonding may be by wire bonding or TAB bonding. 
     20. Etch the sacrificial layers. This can be done with an isotropic wet etch, such as buffered HF. This stage is performed after the mounting of the print-heads into moulded print-head carriers, and after bonding, as the front surface of the print-heads is very fragile after the sacrificial etch has been completed. There should be no direct handling of the print-head chips after the sacrificial etch 
     21. Hydrophobize the front surface of the printheads. 
     22. Fill with ink and perform final testing on the completed printheads. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  2980 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  2983 . Relevant features of the wafer at this step are shown in  FIG. 556 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 555  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Deposit 1 micron of low stress nitride  2982 . This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface. 
     3. Deposit 3 micron of sacrificial material  2990  (e.g. polyimide). 
     4. Etch the sacrificial layer using Mask  1 . This mask defines the actuator anchor point. This step is shown in  FIG. 557 . 
     5. Deposit 0.5 microns of PTFE  2991 . 
     6. Etch the PTFE, nitride, and CMOS passivation down to second level metal using Mask  2 . This mask defines the heater vias  2911 . This step is shown in  FIG. 558 . 
     7. Deposit and pattern resist using Mask  3 . This mask defines the heater. 
     8. Deposit 0.5 microns of gold  2992 . (or other heater material with a low Young&#39;s modulus) and strip the resist Steps 7 and 8 form a lift-off process. This step is shown in  FIG. 559 . 
     9. Deposit 1.5 microns of PTFE  2993 . 
     10. Etch the PTFE down to the sacrificial layer using Mask  4 . This mask defines the actuator paddle and the bond pads. This step is shown in  FIG. 560 . 
     11. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated. 
     12. Plasma process the PTFE to make the top surface hydrophilic. This allows the nozzle chamber to fill by capillarity, but maintains a hydrophobic layer underneath the paddle, which traps an air bubble. The air bubble reduces the negative pressure on the back of the paddle, and increases the temperature achieved by the heater. 
     13. Deposit 10 microns of sacrificial material  2994 . 
     14. Etch the sacrificial material down to nitride using Mask  5 . This mask defines the nozzle chamber  2951  and the nozzle inlet filter  2952 . This step is shown in  FIG. 561 . 
     15. Deposit 3 microns of PECVD glass  2995 . This step is shown in  FIG. 562 . 
     16. Etch to a depth of 1 micron using Mask  6 . This mask defines the nozzle rim  2996 . This step is shown in  FIG. 563 . 
     17. Etch down to the sacrificial layer using Mask  7 . This mask defines the nozzle  2904  and the sacrificial etch access holes  2947 . This step is shown in  FIG. 564 . 
     18. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  8 . This mask defines the ink inlets  2998  which are etched through the wafer. The wafer is also diced by this etch This step is shown in  FIG. 565 . 
     19. Back-etch the CMOS oxide layers and subsequently deposited nitride layers through to the sacrificial layer using the back-etched silicon as a mask. 
     20. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch This step is shown in  FIG. 566 . 
     21. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     22. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     23. Hydrophobize the front surface of the printheads. 
     24. Fill the completed printheads with ink  2999  and test them. A filled nozzle is shown in  FIG. 567 . 
     IJ30 
     In a preferred embodiment, there is provided an ink jet printer having ink ejection nozzles from which ink is ejected with the ink ejection being actuated by means of a thermal actuator which includes a “corrugated” copper heating element encased in a polytetrafluoroethylene (PTFE) layer. 
     Turning now to  FIG. 568 , there is illustrated a cross-sectional view of a single inkjet nozzle  3010  as constructed in accordance with the present embodiment. The inkjet nozzle  3010  includes an ink ejection port  3011  for the ejection of ink from a chamber  3012  by means of actuation of a thermal paddle actuator  3013 . The thermal paddle actuator  3013  comprises an inner copper heating portion  3014  and paddle  3015  which are encased in an outer PTFE layer  3016 . The outer PTFE layer  3016  has an extremely high coefficient of thermal expansion (approximately 770×10 −6 , or around 380 times that of silicon). The PTFE layer  3016  is also highly hydrophobic which results in an a bubble  3017  being formed under the actuator  3013  due to out-gassing etc. The top PTFE layer is treated so as to make it hydrophilic. The heater  3014  is also formed within the lower portion of the actuator  3013 . 
     The heater  3014  is connected at ends  3020 ,  3021  (see also  FIG. 574 ) to a lower CMOS drive layer  3018  containing drive circuitry (not shown). For the purposes of actuation of actuator  3013 , a current is passed through the copper heater element  3014  which heats the bottom surface of actuator  3013 . Turning now to  FIG. 569 , the bottom surface of actuator  3013 , in contact with air bubble  3017  remains heated while any top surface heating is carried away by the exposure of the top surface of actuator  3013  to the ink within chamber  3012 . Hence, the bottom PTFE layer expands more rapidly resulting in a general rapid bending upwards of actuator  3013  (as illustrated in  FIG. 569 ) which consequentially causes the ejection of ink from ink ejection port  3011 . An air inlet channel  3028  is formed between two nitride layers  3042 ,  3026  such that air is free to flow  3029  along channel  3028  and through holes, e.g.  3025 , in accordance with any fluctuating pressure influences. The air flow  3029  acts to reduce the vacuum on the back surface of actuator  3013  during operation. As a result less energy is required for the movement of the actuator  3013 . 
     The actuator  3013  can be deactivated by turning off the current to heater element  3014 . This will result in a return of the actuator  3013  to its rest position. 
     The actuator  3013  includes a number of significant features. In  FIG. 570  there is illustrated a schematic diagram of the conductive layer of the thermal actuator  3013 . The conductive layer includes paddle  3015 , which can be constructed from the same material as heater  3014 , i.e. copper, and which contains a series of holes e.g.  3023 . The holes are provided for interconnecting layers of PTFE both above and below panel  3015  so as to resist any movement of the PTFE layers past the panel  3015  and thereby reducing any opportunities for the delamination of the PTFE and copper layers. 
     Turning to  FIG. 571 , there is illustrated a close up view of a portion of the actuator  3013  of  FIG. 568  illustrating the corrugated nature  3022  of the heater element  3014  within the PTFE nature of actuator  3013  of  FIG. 568 . The corrugated nature  3022  of the heater  3014  allows for a more rapid heating of the portions of the bottom layer surrounding the corrugated heater. Any resistive heater which is based upon applying a current to heat an object will result in a rapid, substantially uniform elevation in temperature of the outer surface of the current carrying conductor. The surrounding PTFE volume is therefore heated by means of thermal conduction from the resistive element. This thermal conduction is known to proceed, to a first approximation, at a substantially linear rate with respect to distance from a resistive element By utilizing a corrugated resistive element the bottom surface of actuator  3013  is more rapidly heated as, on average, a greater volume of the bottom PTFE surface is closer to a portion of the resistive element. Therefore, the utilisation of a corrugated resistive element results in a more rapid heating of the bottom surface layer and therefore a more rapid actuation of the actuator  3013 . Further, a corrugated heater also assists in resisting any delamination of the copper and PTFE layer. 
     Turning now to  FIG. 572 , the corrugated resistive element can be formed by depositing a resist layer  3050  on top of the first PTFE layer  3051 . The resist layer  3050  is exposed utilizing a mask  3052  having a half-tone pattern delineating the corrugations. After development the resist  3050  contains the corrugation pattern. The resist layer  3050  and the PTFE layer  3051  are then etched utilizing an etchant that erodes the resist layer  3050  at substantially the same rate as the PTFE layer  3051 . This transfers the corrugated pattern into the PTFE layer  3051 . Turning to  FIG. 573 , on top of the corrugated PTFE layer  3051  is deposited the copper heater layer  3014  which takes on a corrugated form in accordance with its under layer. The copper heater layer  3014  is then etched in a serpentine or concertina form. Subsequently, a further PTFE layer  3053  is deposited on top of layer  3014  so as to form the top layer of the thermal actuator  3013 . Finally, the second PTFE layer  3052  is planarized to form the top surface of the thermal actuator  3013  ( FIG. 568 ). 
     Returning again now to  FIG. 568 , it is noted that an ink supply can be supplied through a throughway for channel  3038  which can be constructed by means of deep anisotropic silicon trench etching such as that available from STS Limited (“Advanced Silicon Etching Using High Density Plasmas” by J. K. Bhardwaj, H. Ashraf, page 224 of Volume 2639 of the SPIE Proceedings in Micro Machining and Micro Fabrication Process Technology). The ink supply flows from channel  3038  through the side grill portions e.g.  3040  (see also  FIG. 574 ) into chamber  3012 . Importantly, the grill portions e.g.  3040  which can comprise silicon nitride or similar insulating material acts to remove foreign bodies from the ink flow. The grill  3040  also helps to pinch the PTFE actuator  3013  to a base CMOS layer  3018 , the pinching providing an important assistance for the thermal actuator  3013  so as to ensure a substantially decreased likelihood of the thermal actuator layer  3013  separating from a base CMOS layer  3018 . 
     A series of sacrificial etchant holes, e.g.  3019 , are provided in the top wall  3048  of the chamber  3012  to allow sacrificial etchant to enter the chamber  3012  during fabrication so as to increase the rate of etching. The small size of the holes, e.g.  3019 , does not affect the operation of the device  3010  substantially as the surface tension across holes, e.g.  3019 , stops ink being ejected from these holes, whereas, the larger size hole  3011  allows for the ejection of ink. 
     Turning now to  FIG. 574 , there is illustrated an exploded perspective view of a single nozzle  3010 . The nozzles  3010  can be formed in layers starting with a silicon wafer device  3041  having a CMOS layer  3018  on top thereof as required. The CMOS layer  3018  provides the various drive circuitry for driving the copper heater elements  3014 . 
     On top of the CMOS layer  3018  a nitride layer  3042  is deposited, providing primarily protection for lower layers from corrosion or etching. Next a nitride layer  3026  is constructed having the aforementioned holes, e.g.  3025 , and posts, e.g.  3027 . The structure of the nitride layer  3026  can be formed by first laying down a sacrificial glass layer (not shown) onto which the nitride layer  3026  is deposited. The nitride layer  3026  includes various features, for example, a lower ridge portion  3030  in addition to vias for the subsequent material layers. 
     In construction of the actuator  3013  ( FIG. 568 ), the process of creating a first PTFE layer proceeds by laying down a sacrificial layer on top of layer  3026  in which the air bubble underneath actuator  3013  ( FIG. 568 ) subsequently forms. On top of this is formed a first PTFE layer utilizing the relevant mask. Preferably, the PTFE layer includes vias for the subsequent copper interconnections. Next, a copper layer  3043  is deposited on top of the first PTFE layer  3051  and a subsequent PTFE layer is deposited on top of the copper layer  3043 , in each case, utilizing the required mask. 
     The nitride layer  3046  can be formed by the utilisation of a sacrificial glass layer which is masked and etched as required to form the side walls and the grill  3040 . Subsequently, the top nitride layer  3048  is deposited again utilizing the appropriate mask having considerable holes as required. Subsequently, the various sacrificial layers can be etched away so as to release the structure of the thermal actuator. 
     In  FIG. 575  there is illustrated a section of an ink jet printhead configuration  3090  utilizing ink jet nozzles constructed in accordance with a preferred embodiment, e.g.  3091 . The configuration  3090  can be utilized in a three color process 1600 dpi printhead utilizing 3 sets of 2 rows of nozzle chambers, e.g.  3092 ,  3093 , which are interconnected to one ink supply channel, e.g.  3094 , for each set. The 3 supply channels  3094 ,  3095 ,  3096  are interconnected to cyan, magenta and yellow ink reservoirs respectively. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  3041 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  3018 . Relevant features of the wafer at this step are shown in  FIG. 577 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 576  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Deposit 1 micron of low stress nitride  3042 . This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface. 
     3. Deposit 2 microns of sacrificial material  3060  (e.g. polyimide). 
     4. Etch the sacrificial layer using Mask  1 . This mask defines the PTFE venting layer support pillars e.g.  3027  and anchor point. This step is shown in  FIG. 578 . 
     5. Deposit 2 microns of PTFE  3026 . 
     6. Etch the PTFE using Mask  2 . This mask defines the edges of the PTFE venting layer, and the holes in this layer. This step is shown in  FIG. 579 . 
     7. Deposit 3 micron of sacrificial material  3061  (e.g. polyimide). 
     8. Etch the sacrificial layer using Mask  3 . This mask defines the actuator anchor point This step is shown in  FIG. 580 . 
     9. Deposit 1 micron of PTFE. 
     10. Deposit, expose and develop 1 micron of resist using Mask  4 . This mask is a gray-scale mask which defines the heater vias as well as the corrugated PTFE surface  3062  that the heater is subsequently deposited on. 
     11. Etch the PTFE and resist at substantially the same rate. The corrugated resist thickness is transferred to the PTFE, and the PTFE is completely etched in the heater via positions. In the corrugated regions, the resultant PTFE thickness nominally varies between 0.25 micron and 0.75 micron, though exact values are not critical. This step is shown in  FIG. 581 . 
     12. Deposit and pattern resist using Mask  5 . This mask defines the heater. 
     13. Deposit 0.5 microns of gold  3063  (or other heater material with a low Young&#39;s modulus) and strip the resist. Steps  12  and  13  form a lift-off process. This step is shown in  FIG. 582 . 
     14. Deposit 1.5 microns of PTFE  3016 . 
     15. Etch the P TFE down to the sacrificial layer using Mask  6 . This mask defines the actuator paddle and the bond pads. This step is shown in  FIG. 583 . 
     16. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated. 
     17. Plasma process the PTFE to make the top and side surfaces of the paddle hydrophilic. This allows the nozzle chamber to fill by capillarity. 
     18. Deposit 10 microns of sacrificial material  3064 . 
     19. Etch the sacrificial material down to nitride using Mask  7 . This mask defines the nozzle chamber. This step is shown in  FIG. 584 . 
     20. Deposit 3 microns of PECVD glass  3046 . This step is shown in  FIG. 585 . 
     21. Etch to a depth of 1 micron using Mask  8 . This mask defines the nozzle rim  3065 . This step is shown in  FIG. 586 . 
     22. Etch down to the sacrificial layer using Mask  9 . This mask defines the nozzle and the sacrificial etch access holes e.g.  3019 . This step is shown in  FIG. 587 . 
     23. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  10 . This mask defines the ink inlets  3038  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 588 . 
     24. Back-etch the CMOS oxide layers and subsequently deposited nitride layers and sacrificial layer through to PTFE using the back-etched silicon as a mask 
     25. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch This step is shown in  FIG. 589 . 
     26. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     27. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     28. Hydrophobize the front surface of the printheads. 
     29. Fill the completed printheads with ink  3066  and test them. A filled nozzle is shown in  FIG. 590 . 
     IJ31 
     In a preferred embodiment, a drop on demand ink jet nozzle arrangement is provided which allows for the ejection of ink on demand by means of a thermal actuator which operates to eject the ink from a nozzle chamber. The nozzle chamber is formed directly over an ink supply channel thereby allowing for an extremely compact form of nozzle arrangement The extremely compact form of nozzle arrangement allows for minimal area to be taken up by a printing mechanism thereby resulting in improved economics of fabrication. 
     Turning initially to  FIGS. 591-593 , the operation of a preferred embodiment of the nozzle arrangement is now described. In  FIG. 591 , there is illustrated a sectional view of two ink jet nozzle arrangements  3110 ,  3111  which are formed on a silicon wafer  3112  which includes a series of through-wafer ink supply channels  3113 . 
     Located over a portion of the wafer  3112  and over the ink supply channel  3113  is a thermal actuator  3114  which is actuated so as to eject ink from a corresponding nozzle chamber. The actuator  3114  is placed substantially over the ink supply channel  3113 . In the quiescent position, the ink fills the nozzle chamber and an ink meniscus  3115  forms across an ink ejection port  3135  ( FIG. 594 ) of the chamber. 
     When it is desired to eject a drop from the chamber, the thermal actuator  3114  is activated by passing a current through the actuator  3114 . The actuation causes the actuator  3114  to rapidly bend upwards as indicated in  FIG. 592 . The movement of the actuator  3114  results in an increase in the ink pressure around the ejection port  3135  of the chamber which in turn causes a significant bulging of the meniscus  3115  and the flow of ink out of the nozzle chamber. The actuator  3114  can be constructed so as to impart sufficient momentum to the ink to cause the direct ejection of a drop. 
     Alternatively, as indicated in  FIG. 593 , the activation of actuator  3114  can be timed so as to turn the actuation current off at a predetermined point This causes the return of the actuator  3114  to its original position thereby resulting in a consequential backflow of ink in the direction of an arrow  3117  into the chamber. This causes a necking and separation of a body of ink  3118  which has a continuing momentum and continues towards the output media, such as paper, for printing thereof. The actuator  3114  then returns to its quiescent position and surface tension effects result in a refilling of the nozzle chamber via the ink supply channel  3113  as a consequence of surface tension effects on the meniscus  3115 . In time, the condition of the ink returns to that depicted in  FIG. 591 . 
     Turning now to  FIGS. 594 and 595 , there is illustrated the structure of a single nozzle arrangement  3110  in more detail.  FIG. 594  is a part sectional view while  FIG. 595  shows a corresponding exploded perspective view. Many ink jet nozzles can be formed at a time, on a selected wafer base  3112  utilizing standard semi-conductor processing techniques in addition to micro-machining and microfabrication process technology (MEMS) and a full familiarity with these technologies is hereinafter assumed. 
     On top of the silicon wafer layer  3112  is formed a CMOS layer  3120 . The CMOS layer  3120  can, in accordance with standard techniques, include multi-level metal layers sandwiched between oxide layers and preferably at least a two level metal process is utilized. In order to reduce the number of necessary processing steps, the masks utilized include areas which provide for a build up of an aluminum barrier  3121  which can be constructed from a first level  3122  of aluminum and second level  3123  of aluminum layer. Additionally, aluminum portions  3124  are provided which define electrical contacts to a subsequent heater layer. The aluminum barrier portion  3121  is important for providing an effective barrier to the possible subsequent etching of the oxide within the CMOS layer  3120  when a sacrificial etchant is utilized in the construction of the nozzle arrangement  3110  with the etchable material preferably being glass layers. 
     On top of the CMOS layer  3120  is formed a nitride passivation layer  3126  to protect the lower CMOS layers from sacrificial etchants and ink erosion. Above the nitride layer  3126  there is formed a gap  3128  in which an air bubble forms during operation. The gap  3128  can be constructed by laying down a sacrificial layer and subsequently etching the gap  3128  as will be explained hereinafter. 
     On top of the air gap  3128  is constructed a polytetrafluoroethylene (PTFE) layer  3129  which comprises a gold serpentine heater layer  3130  sandwiched between two PTFE layers. The gold heater layer  3130  is constructed in a serpentine form to allow it to expand on heating. The heater layer  3130  and PTFE layer  3129  together comprise the thermal actuator  3114  of  FIG. 591 . 
     The outer PTFE layer  3129  has an extremely high coefficient of thermal expansion (approximately 770×10 −6 , or around 380 times that of silicon). The PTFE layer  3129  is also normally highly hydrophobic which results in an air bubble being formed under the actuator in the gap  3128  due to out-gassing etc. The top PTFE surface layer is treated so as to make it hydrophilic in addition to those areas around ink supply channel  3113 . This can be achieved with a plasma etch in an ammonia atmosphere. The heater layer  3130  is also formed within the lower portion of the PTFE layer. 
     The heater layer  3130  is connected at ends e.g.  3131  to the lower CMOS drive layer  3120  which contains the drive circuitry (not shown). For operation of the actuator  3114 , a current is passed through the gold heater element  3130  which heats the bottom surface of the actuator  3114 . The bottom surface of actuator  3114 , in contact with the air bubble remains heated while any top surface heating is carried away by the exposure of the top surface of actuator  3114  to the ink within a chamber  3132 . Hence, the bottom PTFE layer expands more rapidly resulting in a general rapid upward bending of actuator  3114  (as illustrated in  FIG. 592 ) which consequentially causes the ejection of ink from the ink ejection port  3135 . 
     The actuator  3114  can be deactivated by turning off the current to the heater layer  3130 . This will result in a return of the actuator  3114  to its rest position. 
     On top of the actuator  3114  are formed nitride side wall portions  3133  and a top wall portion  3134 . The wall portions  3133  and the top portions  3134  can be formed via a dual damascene process utilizing a sacrificial layer. The top wall portion  3134  is etched to define the ink ejection port  3135  in addition to a series of etchant holes  3136  which are of a relatively small diameter and allow for effective etching of lower sacrificial layers when utilizing a sacrificial etchant. The etchant holes  3136  are made small enough such that surface tension effects restrict the possibilities of ink being ejected from the chamber  3132  via the etchant holes  3136  rather than the ejection port  3135 . 
     Turning now to  FIGS. 596-605 , there will now be explained the various steps involved in the construction of an array of ink jet nozzle arrangements: 
     1. Turning initially to  FIG. 596 , the starting position comprises a silicon wafer  3112  including a CMOS layer  3120  which has nitride passivation layer  3126  and which is surface finished with a chemical-mechanical planarization process. 
     2. The nitride layer is masked and etched as illustrated in  FIG. 597  so as to define portions of the nozzle arrangement and areas for interconnection between any subsequent heater layer and a lower CMOS layer. 
     3. Next, a sacrificial oxide layer  3140  is deposited, masked and etched as indicated in  FIG. 598  with the oxide layer being etched in those areas that a subsequent heater layer electronically contacts the lower layers. 
     4. As illustrated in  FIG. 599 , next a 1 micron layer of PTFE  3141  is deposited and first masked and etched for the heater contacts to the lower CMOS layer and then masked and etched for the heater shape. 
     5. Next, as illustrated in  FIG. 600 , the gold heater layer  3130 ,  3131  is deposited. Due to the fact that it is difficult to etch gold, the layer can be conformally deposited and subsequently portions removed utilizing chemical mechanical planarization so as to leave those portions associated with the heater element. The processing steps 4 and 5 basically comprise a dual damascene process. 
     6. Next, a top PTFE layer  3142  is deposited and masked and etched down to the sacrificial layer as illustrated in  FIG. 601  so as to define the heater shape. Subsequently, the surface of the PTFE layer is plasma processed so as to make it hydrophilic. Suitable processing can including plasma damage in an ammonia atmosphere. Alternatively, the surface could be coated with a hydrophilic material. 
     7. A further sacrificial layer  3143  is then deposited and etched as illustrated in  FIG. 602  so as to form the structure for the nozzle chamber. The sacrificial oxide being is masked and etched in order to define the nozzle chamber walls. 
     8. Next, as illustrated in  FIG. 603 , the nozzle chamber is formed by conformally depositing three microns of nitride and etching a mask nozzle rim to a depth of one micron for the nozzle rim (the etched depth not being overly time critical). Subsequently, a mask is utilized to etch the ink ejection port  3135  in addition to the sacrificial layer etchant holes  3136 . 
     9. Next, as illustrated in  FIG. 604 , the backside of the wafer is masked for the ink channels  3113  and plasma etched through the wafer. A suitable plasma etching process can include a deep anisotropic trench etching system such as that available from SDS Systems Limited (See) “Advanced Silicon Etching Using High Density Plasmas” by J. K. Bhardwaj, H. Ashraf, page 224 of Volume 2639 of the SPIE Proceedings in Micro Machining and Micro Fabrication Process Technology). 
     10. Next, as illustrated in  FIG. 605 , the sacrificial layers are etched away utilizing a sacrificial etchant such as hydrochloric acid. Subsequently, the portion underneath the actuator which is around the ink channel is plasma processed through the backside of the wafer to make the panel end hydrophilic. 
     Subsequently, the wafer can be separated into separate printheads and each printhead is bonded into an injection molded ink supply channel and the electrical signals to the chip can be tape automated bonded (TAB) to the printhead for subsequent testing.  FIG. 606  illustrates a top view of nozzle arrangement constructed on a wafer so as to provide for pagewidth multicolor output. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  3112 , Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  3120 . This step is shown in  FIG. 608 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 607  is a key to representations of various materials in these manufacturing diagrams, and those of other cross-referenced ink jet configurations. 
     2. Deposit 1 micron of low stress nitride  3150 . This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface. 
     3. Deposit 3 microns of sacrificial material  3151  (e.g. polyimide). 
     4. Etch the sacrificial layer using Mask  1 . This mask defines the actuator anchor point This step is shown in  FIG. 609 . 
     5. Deposit 0.5 microns of PTFE  3152 . 
     6. Etch the PTFE, nitride, and CMOS passivation down to second level metal using Mask  2 . This mask defines the heater vias  3131 . This step is shown in  FIG. 610 . 
     7. Deposit and pattern resist using Mask  3 . This mask defines the heater. 
     8. Deposit 0.5 microns of gold  3130  (or other heater material with a low Young&#39;s modulus) and strip the resist. Steps 7 and 8 form a lift-off process. This step is shown in  FIG. 611 . 
     9. Deposit 1.5 microns of PTFE  3153 . 
     10. Etch the PTFE down to the sacrificial layer using Mask  4 . This mask defines the actuator  3114  and the bond pads. This step is shown in  FIG. 612 . 
     11. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated 
     12. Plasma process the PTFE to make the top and side surfaces of the actuator hydrophilic. This allows the nozzle chamber to fill by capillarity. 
     13. Deposit 10 microns of sacrificial material  3154 . 
     14. Etch the sacrificial material down to nitride using Mask  5 . This mask defines the nozzle chamber. This step is shown in  FIG. 613 . 
     15. Deposit 3 microns of PECVD glass  3155 . This step is shown in  FIG. 614 . 
     16. Etch to a depth of 1 micron using Mask  6 . This mask defines a rim  3156  of the ejection port. This step is shown in  FIG. 615 . 
     17. Etch down to the sacrificial layer using Mask  7 . This mask defines the ink ejection port  3135  and the sacrificial etch access holes  3136 . This step is shown in  FIG. 616 . 
     18. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  8 . This mask defines the ink inlets  3113  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 617 . 
     19. Back-etch the CMOS oxide layers and subsequently deposited nitride layers and sacrificial layer through to PTFE using the back-etched silicon as a mask. 
     20. Plasma process the PTFE through the back-etched holes to make the top surface of the actuator hydrophilic. This allows the nozzle chamber to fill by capillarity, but maintains a hydrophobic surface underneath the actuator. This hydrophobic section causes an air bubble to be trapped under the actuator when the nozzle is filled with a water based ink. This bubble serves two purposes: to increase the efficiency of the heater by decreasing thermal conduction away from the heated side of the PTFE, and to reduce the negative pressure on the back of the actuator. 
     21. Etch the sacrificial material. The nozzle arrangements are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 618 . 
     22. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     23. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     24. Hydrophobize the front surface of the printheads. 
     25. Fill the completed printheads with ink  3157  and test them. A filled nozzle is shown in  FIG. 619 . 
     IJ32 
     In a preferred embodiment, the actuation of an actuator for the ejection of ink is based around the utilization of material having a High Young&#39;s modulus. 
     In a preferred embodiment, materials are utilized for the ejection of ink which have a high bend efficiency when thermally heated. The inkjet printhead is constructed utilizing standard MEMS technology and therefore should utilize materials that are common in the construction of semi-conductor wafers. In a preferred embodiment, the materials have been chosen by using a bend efficiency for actuator devices which can be calculated in accordance with the following formula.
 
bend efficiency=Young&#39;s Modulus×(Coefficient of thermal Expansion)/Density×Specific Heat Capacity
 
     Of course, different equations could be utilized and, in particular, the factors on the numerator and the denominator have been chosen for their following qualities. 
     Coefficient of thermal expansion: The greater the coefficient of thermal expansion, the greater will be the degree of movement for any particular heating of a thermal actuator. 
     Young&#39;s Modulus: The Young&#39;s modulus provides a measure of the tensile or compressive stress of a material and is an indicator of the “strength” of the bending movement Hence, a material having a high Young&#39;s modulus or strength is desirable. 
     Heat capacity: In respect of the heat capacity, the higher the heat capacity, the greater the ability of material to absorb heat without deformation. This is an undesirable property in a thermal actuator. 
     Density: The denser the material the greater the heat energy required to heat the material and again, this is an undesirable property. 
     Example materials and their corresponding “Bend Efficiencies” are listed in the following table: 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                 Young&#39;s 
                 Heat 
                   
                   
               
               
                   
                 CTE * 
                 modulus 
                 capacity 
                 Density 
                 “Bend 
               
               
                 MATERIAL 
                 10 −6 /K 
                 GPa 
                 W/Kg/C 
                 Kg/M 3   
                 efficiency” 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Gold 
                 14.2 
                 80 
                 129 
                 19300 
                 456 
               
               
                 PTFE 
                 770 
                 1.3 
                 1024 
                 2130 
                 459 
               
               
                 Silicon Nitride 
                 3.3 
                 337 
                 712 
                 3200 
                 488 
               
               
                 Osmium 
                 2.6 
                 581 
                 130 
                 22570 
                 515 
               
               
                 Tantalum- 
                 6.48 
                 186 
                 140 
                 16660 
                 517 
               
               
                 Tungsten alloy 
               
               
                 Silver 
                 18.9 
                 71 
                 235 
                 10500 
                 544 
               
               
                 Platinum 
                 8.8 
                 177 
                 133 
                 21500 
                 545 
               
               
                 Copper 
                 16.5 
                 124 
                 385 
                 8960 
                 593 
               
               
                 Molybdenum 
                 4.8 
                 323 
                 251 
                 10200 
                 606 
               
               
                 Aluminum 
                 23.1 
                 28.9 
                 897 
                 2700 
                 657 
               
               
                 Nickel 
                 13.4 
                 206 
                 444 
                 8900 
                 699 
               
               
                 Tungsten 
                 4.5 
                 408 
                 132 
                 19300 
                 721 
               
               
                 Ruthenium 
                 5.05 
                 394 
                 247 
                 12410 
                 1067 
               
               
                 Stainless Steel 
                 20.2 
                 215 
                 500 
                 7850 
                 1106 
               
               
                 Iridium 
                 6.8 
                 549 
                 130 
                 22650 
                 1268 
               
               
                 High Silicon 
                 31.5 
                 130 
                 376 
                 8250 
                 1320 
               
               
                 Brass 
               
               
                 “Chromel D” 
                 25.2 
                 212 
                 448 
                 7940 
                 1502 
               
               
                 alloy 
               
               
                 Titanium 
                 8.2 
                 575 
                 636 
                 4450 
                 1666 
               
               
                 DiBoride 
               
               
                 Boron Carbide 
                 10.1 
                 454 
                 955 
                 2520 
                 1905 
               
               
                   
               
            
           
         
       
     
     Utilizing the above equation, it can be seen that a suitable material is titanium diboride (TiB 2 ) which has a high bend efficiency and is also regularly used in semiconductor fabrication techniques. Although this material has a High Young&#39;s modulus, the coefficient of thermal expansion is somewhat lower than other possible materials. Hence, in a preferred embodiment, a fulcrum arrangement is utilized to substantially increase the travel of a material upon heating thereby more fully utilizing the effect of the High Young&#39;s modulus material. 
     Turning initially to  FIGS. 620 and 621 , there is illustrated a single nozzle arrangement  3201  of an inkjet printhead constructed in accordance with a preferred embodiment  FIG. 620  illustrates a side perspective view of the nozzle arrangement and  FIG. 621  is an exploded perspective view of the nozzle arrangement of  FIG. 620 . The single nozzle arrangement  3201  can be constructed as part of an array of nozzle arrangements formed on a silicon wafer  3202  utilizing standard MEM processing techniques. On top of the silicon wafer  3202  is formed a CMOS layer  3203  which can include multiple metal layers formed within glass layers in accordance with the normal CMOS methodologies. 
     The wafer  3202  can contain a number of etched chambers e.g.  3233  the chambers being etched through the wafer utilizing a deep trench silicon etcher. 
     A suitable plasma etching process can include a deep anisotropic trench etching system such as that available from SDS Systems Limited (See “Advanced Silicon Etching Using High Density Plasmas” by J. K. Bhardwaj, H. Ashraf, page 224 of Volume 2639 of the SPIE Proceedings in Micro Machining and Micro Fabrication Process Technology). 
     A preferred embodiment  3201  includes two arms  3204 ,  3205  which operate in air and are constructed from a thin  0 . 3  micrometer layer of titanium diboride  3206  on top of a much thicker 5.8 micron layer of glass  3207 . The two arms  3204 ,  3205  are joined together and pivot around a point  3209  which is a thin membrane forming an enclosure which in turn forms part of the nozzle chamber  3210 . 
     The arms  3204  and  3205  are affixed by posts  3211 ,  3212  to lower aluminum conductive layers  3214 ,  3215  which can form part of the CMOS layer  3203 . The outer surfaces of the nozzle chamber  3218  can be formed from glass or nitride and provide an enclosure to be filled with ink. The outer chamber  3218  includes a number of etchant holes e.g.  3219  which are provided for the rapid sacrificial etchant of internal cavities during construction. A nozzle rim  3220  is further provided around an ink ejection port  3221  for the ejection of ink. 
     The paddle surface  3224  is bent downwards as a result of release of the structure during fabrication. A current is passed through the titanium boride layer  3206  to cause heating of this layer along arms  3204  and  3205 . The heating generally expands the TiB 2  layer of arms  3204  and  3205  which have a high young&#39;s modulus. This expansion acts to bend the arms generally downwards, which are in turn pivoted around the membrane  3209 . The pivoting results in a rapid upward movement of the paddle surface  3224 . The upward movement of the paddle surface  3224  causes the ejection of ink from the nozzle chamber  3210 . The increase in pressure is insufficient to overcome the surface tension characteristics of the smaller etchant holes  3219  with the result being that ink is ejected from the nozzle chamber hole  3221 . 
     As noted previously the thin titanium diboride strip  3206  has a sufficiently high young&#39;s modulus so as to cause the glass layer  3207  to be bent upon heating of the titanium diboride layer  3206 . Hence, the operation of the inkjet device can be as illustrated in  FIGS. 622-624 . In its quiescent state, the inkjet nozzle is as illustrated in  FIG. 622 , generally in the bent down position with the ink meniscus  3230  forming a slight bulge and the paddle being pivoted around the membrane wall  3209 . The heating of the titanium diboride layer  3206  causes it to expand. Subsequently, it is bent by the glass layer  3207  so as to cause the pivoting of the paddle  3225  around the membrane wall  3209  as indicated in  FIG. 623 . This causes the rapid expansion of the meniscus  3230  resulting in the general ejection of ink from the nozzle chamber  3210 . Next, the current to the titanium diboride layer is turned off and the paddle  3225  returns to its quiescent state resulting in a general sucking back of ink via the meniscus  3230  which in turn results in the ejection of a drop  3231  on demand from the nozzle chamber  3210 . 
     Although many different alternatives are possible, the arrangement of a preferred embodiment can be constructed utilizing the following processing steps: 
     1. The starting wafer is a CMOS processed wafer with suitable electrical circuitry for the operation of an array of printhead nozzles and includes aluminum layer portions  3214 ,  3215 . 
     2. First, the CMOS wafer layer  3203  can be etched down to the silicon wafer layer  3202  in the area of an ink supply channel  3234 . 
     3. Next, a sacrificial layer can be constructed on top of the CMOS layer and planarized. A suitable sacrificial material can be aluminum. This layer is planarized, masked and etched to form cavities for the glass layer  3207 . Subsequently, a glass layer is deposited on top of the sacrificial aluminum layer and etched so as to form the glass layer  3207  and a layer  3213 . 
     4. A titanium diboride layer  3206  is then deposited followed by the deposition of a second sacrificial material layer, the material again can be aluminum, the layer subsequently being planarized. 
     5. The sacrificial etchant layer is then etched to form cavities for the deposition of the side walls e.g.  3209  of the top of the nozzle chamber  3210 . 
     6. A glass layer  3252  is then deposited on top of the sacrificial layer and etched so as to form a roof of the chamber layer. 
     7. The rim  3220  ink ejection port  3221  and etchant holes e.g.  3219  can then be formed in the glass layer  3252  utilizing suitable etching processes. 
     8. The sacrificial aluminum layers are sacrificially etched away so as to release the MEMS structure. 
     9. The ink supply channels can be formed through the back etching of the silicon wafer utilizing a deep anisotropic trench etching system such as that available from Silicon Technology Systems. The deep trench etching systems can also be simultaneously utilized to separate printheads of a wafer which can then be mounted on an ink supply system and tested for operational capabilities. 
     Turning finally to  FIG. 625 , there is illustrated a portion of a printhead  3240  showing a multi-colored series of inkjet nozzles suitably arranged to form a multi-colored printhead. The portion is shown, partially in section so as to illustrate the through wafer etching process 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  3202 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  3203 . Relevant features of the wafer at this step are shown in  FIG. 627 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 626  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide down to silicon or aluminum using Mask  1 . This mask defines the ink inlet, channel  3234 , a heater contact vias, and the edges of the printhead chips. This step is shown in  FIG. 628 . 
     3. Deposit 1 micron of sacrificial material  3250  (e.g. aluminum) 
     4. Etch the sacrificial layer using Mask  2 , defining the nozzle chamber wall and the actuator anchor point. This step is shown in  FIG. 629 . 
     5. Deposit 3 microns of PECVD glass  3213 , and etch the glass  3213  using Mask  3 . This mask defines the actuator, the nozzle walls, and the actuator anchor points with the exception of the contact vias. The etch continues through to aluminum. 
     6. Deposit 0.5 microns of heater material  3206 , for example titanium nitride (TiN) or titanium diboride (TiB 2 ). This step is shown in  FIG. 630 . 
     7. Etch the heater material using Mask  4 , which defines the actuator loop. This step is shown in  FIG. 631 . 
     8. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     9. Deposit 8 microns of sacrificial material  3251 . 
     10. Etch the sacrificial material down to glass or heater material using Mask  5 . This mask defines the nozzle chamber wall the side wall e.g.  3209 , and actuator anchor points. This step is shown in  FIG. 632 . 
     11. Deposit 3 microns of PECVD glass  3252 . This step is shown in  FIG. 633 . 
     12. Etch the glass  3252  to a depth of 1 micron using Mask  6 . This mask defines the nozzle rim  3220 . This step is shown in  FIG. 634 . 
     13. Etch down to the sacrificial layer using Mask  7 . This mask defines the nozzle port  3221  and the sacrificial etch access holes  3219 . This step is shown in  FIG. 635 . 
     14. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  3208 . This mask defines the ink inlet channels  3234  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 636 . 
     15. Etch the sacrificial material. The nozzle chambers  3210  are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 637 . 
     16. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     17. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     18. Hydrophobize the front surface of the printheads. 
     19. Fill the completed printheads with ink  3253  and test them. A filled nozzle is shown in  FIG. 638 . 
     IJ33 
     In a preferred embodiment, there is provided an ink jet printing system wherein each nozzle has a nozzle chamber having a slotted side wall through which is formed an actuator mechanism attached to a vane within the nozzle chamber such that the actuator can be activated to move the vane within the nozzle chamber to thereby cause ejection of ink from the nozzle chamber. 
     Turning now to the figures, there is illustrated in  FIG. 639  an example of an ink jet nozzle arrangement  3301  as constructed in accordance with a preferred embodiment. The nozzle arrangement includes a nozzle chamber  3302  normally filled with ink and an actuator mechanism  3303  for actuating a vane  3304  for the ejection of ink from the nozzle chamber  3302  via an ink ejection port  3305 . 
       FIG. 639  is a perspective view of the ink jet nozzle arrangement of a preferred embodiment in its idle or quiescent position.  FIG. 640  illustrates a perspective view after actuation of the actuator  3303 . 
     The actuator  3303  includes two arms  3306 ,  3307 . The two arms can be formed from titanium diboride (TiB 2 ) which has a high Young&#39;s modulus and therefore provides a large degree of bending strength. A current is passed along the arms  3306 ,  3307  with the arm  3307  having a substantially thicker portion along most of its length. The arm  3307  is stiff but for in the area of thinned portion  3308  and hence the bending moment is concentrated in the area  3308 . The thinned arm  3306  is of a thinner form and is heated by means of resistive heating of a current passing through the arms  3306 ,  3307 . The arms  3306 ,  3307  are interconnected with electrical circuitry via connections  3310 ,  3311 . 
     Upon heating of the arm  3306 , the arm  3306  is expanded with the bending of the arm  3307  being concentrated in the area  3308 . This results in movement of the end of the actuator mechanism  3303  which proceeds through a slot  3319  in a wall of the nozzle chamber  3302 . The bending further causes movement of vane  3304  so as to increase the pressure of the ink within the nozzle chamber and thereby cause its subsequent ejection from ink ejection port  3305 . The nozzle chamber  3302  is refilled via an ink channel  3313  ( FIG. 641 ) formed in a wafer substrate  3314 . After movement of the vane  3304 , so as to cause the ejection of ink, the current to arm  3306  is turned off which results in a corresponding back movement of the vane  3304 . The ink within nozzle chamber  3302  is then replenished by means of wafer ink supply channel  3313  which is attached to an ink supply formed on the back of wafer  3314 . The refill can be by means of a surface tension reduction effect of the ink within nozzle chamber  3302  across ink ejection port  3305 . 
       FIG. 641  illustrates an exploded perspective view of the components of the ink jet nozzle arrangement 
     Referring now specifically to  FIG. 641 , a preferred embodiment can be constructed utilizing semiconductor processing techniques in addition to micro machining and micro fabrication process technology (MEMS) and a full familiarity with these technologies is hereinafter assumed. 
     The nozzles can preferably be constructed by constructing a large array of nozzles on a single silicon wafer at a time. The array of nozzles can be divided into multiple printheads, with each printhead itself having nozzles grouped into multiple colors to provide for full color image reproduction. The arrangement can be constructed via the utilization of a standard silicon wafer substrate  3314  upon which is deposited an electrical circuitry layer  3316  which can comprise a standard CMOS circuitry layer. The CMOS layer can include an etched portion defining pit  3317 . On top of the CMOS layer is initially deposited a protective layer (not shown) which comprise silicon nitride or the like. On top of this layer is deposited a sacrificial material which is initially suitably etched so as to form cavities for the portion of the thermal actuator  3303  and bottom portion of the vane  3304 , in addition to the bottom rim of nozzle chamber  3302 . These cavities can then be filled with titanium diboride. Next, a similar process is used to form the glass portions of the actuator. Next, a further layer of sacrificial material is deposited and suitably etched so as to form the rest of the vane  3304  in addition to a portion of the nozzle chamber walls to the same height of vane  3304 . 
     Subsequently, a further sacrificial layer is deposited and etched in a suitable manner so as to form the rest of the nozzle chamber  3302 . The top surface of the nozzle chamber is further etched so as to form the nozzle rim rounding the ejection port  3305 . Subsequently, the sacrificial material is etched away so as to release the construction of a preferred embodiment. It will be readily evident to those skilled in the art that other MEMS processing steps could be utilized. 
     Preferably, the thermal actuator and vane portions  3303  and  3304  in addition to the nozzle chamber  3302  are constructed from titanium diboride. The utilization of titanium diboride is standard in the construction of semiconductor systems and, in addition, its material properties, including a high Young&#39;s modulus, is utilized to advantage in the construction of the thermal actuator  3303 . 
     Further, preferably the actuator  3303  is covered with a hydrophobic material, such as Teflon, so as to prevent any leaking of the liquid out of the slot  3319  ( FIG. 639 ). 
     Further, as a final processing step, the ink channel can be etched through the wafer utilizing a high anisotropic silicon wafer etch. This can be done as an anisotropic crystallographic silicon etch, or an anisotropic dry etch. A dry etch system capable of high aspect ratio deep silicon trench etching such as the Surface Technology Systems (STS) Advance Silicon Etch (ASE) system is recommended for volume production, as the chip size can be reduced over a wet etch. The wet etch is suitable for small volume production where a suitable plasma etch system is not available. Alternatively, but undesirably, ink access can be around the sides of the printhead chips. If ink access is through the wafer higher ink flow is possible, and there is less requirement for high accuracy assembly. If ink access is around the edge of the chip, ink flow is severely limited, and the printhead chips must be carefully assembled onto ink channel chips. This latter process is difficult due to the possibility of damaging the fragile nozzle plate. If plasma etching is used, the chips can be effectively diced at the same time. Separating the chips by plasma etching allows them to be spaced as little as 35 μm apart, increasing the number of chips on a wafer. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  3314 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  3316 . Relevant features of the wafer at this step are shown in  FIG. 643 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 642  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide down to silicon or aluminum using Mask  1 . This mask defines the ink inlet, the heater contact vias, and the edges of the printhead chips. This step is shown in  FIG. 644 . 
     3. Deposit 1 micron of sacrificial material  3321  (e.g. aluminum) 
     4. Etch the sacrificial layer  3321  using Mask  2 , defining the nozzle chamber wall and the actuator anchor point. This step is shown in  FIG. 645 . 
     5. Deposit 1 micron of heater material  3322 , for example titanium nitride (TiN) or titanium diboride (TiB 2 ). 
     6. Etch the heater material  3322  using Mask  3 , which defines the actuator loop and the lowest layer of the nozzle wall. This step is shown in  FIG. 646 . 
     7. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     8. Deposit 1 micron of titanium nitride  3323 . 
     9. Etch the titanium nitride  3323  using Mask  4 , which defines the nozzle chamber wall, with the exception of the nozzle chamber actuator slot, and the paddle. This step is shown in  FIG. 647 . 
     10. Deposit 8 microns of sacrificial material  3324 . 
     11. Etch the sacrificial material  3324  down to titanium nitride  3323  using Mask  5 . This mask defines the nozzle chamber wall and the paddle. This step is shown in  FIG. 648 . 
     12. Deposit a 0.5 micron conformal layer of titanium nitride  3325  and planarize down to the sacrificial layer using CMP. 
     13. Deposit 1 micron of sacrificial material  3326 . 
     14. Etch the sacrificial material  3326  down to titanium nitride  3325  using Mask  6 . This mask defines the nozzle chamber wall. This step is shown in  FIG. 649 . 
     15. Deposit 1 micron of titanium nitride  3327 . 
     16. Etch to a depth of (approx.) 0.5 micron using Mask  7 . This mask defines the nozzle rim  3328 . This step is shown in  FIG. 650 . 
     17. Etch down to the sacrificial layer  3326  using Mask  8 . This mask defines the roof of the nozzle chamber  3302 , and the port  3305 . This step is shown in  FIG. 651 . 
     18. Back-etch completely through the silicon wafer  3314  (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  9 . This mask defines the ink inlets  3313  which are etched through the wafer  3314 . The wafer  3314  is also diced by this etch. This step is shown in  FIG. 652 . 
     19. Etch the sacrificial material  3324 . The nozzle chambers  3302  are cleared, the actuators  3303  freed, and the chips are separated by this etch. This step is shown in  FIG. 653 . 
     20. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     21. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     22. Hydrophobize the front surface of the printheads. 
     23. Fill the completed printheads with ink  3329  and test them. A filled nozzle is shown in  FIG. 654 . 
     IJ34 
     In a preferred embodiment, there is provided an inkjet printer having a series of ink ejection mechanisms wherein each ink ejection mechanism includes a paddle actuated by a coil actuator, the coil spring actuator having a unique cross section so as to provide for efficient actuation as a coiled thermal actuator. 
     Turning initially to  FIG. 655 , there is illustrated a single ink ejection mechanism  3401  constructed in accordance with the principles of a preferred embodiment The ink ejection mechanism  3401  includes a chamber  3402  having a rim  3403 . The chamber  3402  is normally filled with ink which bulges out around a surface having a border along the edge of rim  3403 , the ink being retained within the chamber  3402  by means of surface tension around the rim  3403 . Outside of the chamber  3402  is located a thermal actuator device  3405 . The thermal actuator device  3405  is interconnected via a strut  3406  through a hole  3407  to a paddle device within the chamber  3402 . The strut  3406  and hole  3407  are treated so as to be hydrophobic. Further, the hole  3407  is provided in a thin elongated form so that surface tension characteristics also assist in stopping any ink from flowing out of the hole  3407 . 
     The thermal actuator device  3405  comprises a first arm portion  3409  which can be constructed from glass or other suitable material. A second arm portion  3410  can be constructed from material such as titanium diboride which has a large Young&#39;s modulus or bending strength and hence, when a current is passed through the titanium diboride layer  3410 , it expands with a predetermined coefficient of thermal expansion. The thin strip  3410  has a high Young&#39;s modulus or bending strength and therefore the thin strip  3410  is able to bend the much thicker strip  3409  which has a substantially lower Young&#39;s modulus. 
     Turning to  FIG. 656 , there is illustrated a cross-section of the arm through the line II-II of  FIG. 655  illustrating the structure of the actuator device  3405 . As described previously, the actuator device  3405  includes two titanium diboride portions  3410   a ,  3410   b  forming a circuit around the coil in addition to the glass portion  3409  which also provides for electrical isolation of the two arms, the arms being conductively joined at the strut end. 
     Turning now to  FIGS. 657-659 , there will now be explaining the operation of the ink ejection mechanism  3401  for the ejection of ink. Initially, before the paddle  3408  has started moving, the situation is as illustrated in  FIG. 657  with the nozzle chamber  3402  being filled with ink and having a slightly bulging in meniscus  3412 . Upon actuation of the actuator mechanism, the paddle  3408  begins to move towards the nozzle rim  3403  resulting in a substantial increase in pressure in the area around the nozzle rim  3403 . This in turn results in the situation as illustrated in  FIG. 658  wherein the meniscus begins to significantly bulge as a result of the increases in pressure. Subsequently, the actuator is deactivated resulting in a general urge for the paddle  3408  to return to its rest position. This results in the ink being sucked back into the chamber  3402  which in turn results in the meniscus necking and breaking off into a meniscus  3412  and ink drop  3414 , the drop  3414  proceeding to a paper or film medium (not shown) for marking. The meniscus  3412  has generally a concave shape and surface tension characteristics result in chamber refilling by means of in flow  3413  from an ink supply channel etched through the wafer. The refilling is as a consequence of surface tension forces on the meniscus  3412 . Eventually the meniscus returns to its quiescent state as illustrated in  FIG. 657 . 
     Turning now to  FIG. 660 , there is illustrated an exploded perspective view of a single ink ejection mechanism  3401  illustrating the various material layers. The ink ejection mechanism  3401  can be formed as part of a large array of mechanisms forming a print head with multiple printheads being simultaneously formed on a silicon wafer  3417 . The wafer  3417  is initially processed so as to incorporate a standard CMOS circuitry layer  3418  which provides for the electrical interconnect for the control of the conductive portions of the actuator. The CMOS layer  3418  can be completed with a silicon nitride passivation layer so as to protect it from subsequent processing steps in addition to ink flows through channel  3420 . The subsequent layers e.g.  3409 ,  3410  and  3402  can be deposited utilizing standard micro-electro mechanical systems (MEMS) construction techniques including the deposit of sacrificial aluminum layers in addition to the deposit of the layers  3410  constructed from titanium diboride the layer  3409  constructed from glass material and the nozzle chamber proper  3402  again constructed from titanium diboride. Each of these layers can be built up in a sacrificial material such as aluminum which is subsequently etched away. Further, an ink supply channel e.g.  3421  can be etched through the wafer  3417 . The etching can be by means of an isotropic crystallographic silicon etch or an isotropic dry etch. A dry etch system capable of high aspect ratio silicon trench etching such as the Surface Technology Systems (STS) Advance Silicon Etch (ASE) system is recommended. 
     Subsequent to construction of the nozzle arrangement  3401 , it can be attached to an ink supply apparatus for supplying ink to the reverse surface of the wafer  3417  so that ink can flow into chamber  3402 . 
     The external surface of nozzle chamber  3402  including rim  3403 , in addition to the area surrounding slot  3407 , can then be hydrophobically treated so as to reduce the possibility of any ink exiting slot  3407 . 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  3417 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process to form layer  3418 . This step is shown in  FIG. 662 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 661  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide layer  3418  down to silicon or aluminum using Mask  1 . This mask defines the ink inlet, the heater contact vias, and the edges of the print heads chip. This step is shown in  FIG. 663 . 
     3. Deposit 1 micron of sacrificial material  3430  (e.g. aluminum) 
     4. Etch the sacrificial layer  3430  using Mask  2 , defining the nozzle chamber wall and the actuator anchor point. This step is shown in  FIG. 664 . 
     5. Deposit 1 micron of glass  3431 . 
     6. Etch the glass using Mask  3 , which defines the lower layer of the actuator loop. 
     7. Deposit 1 micron of heater material  3432 , for example titanium nitride (TiN) or titanium diboride (TiB2). Planarize using CMP. Steps 5 to 7 form a ‘damascene’ process. This step is shown in  FIG. 665 . 
     8. Deposit 0.1 micron of silicon nitride (not shown). 
     9. Deposit 1 micron of glass  3433 . 
     10. Etch the glass  3433  using Mask  4 , which defines the upper layer of the actuator loop. 
     11. Etch the silicon nitride using Mask  5 , which defines the vias connecting the upper layer of the actuator loop to the lower layer of the actuator loop. 
     12. Deposit 1 micron of the same heater material  3434  as in step  7  heater material  3432 . Planarize using CMP. Steps 8 to 12 form a ‘dual damascene’ process. This step is shown in  FIG. 666 . 
     13. Etch the glass down to the sacrificial layer  3430  using Mask  6 , which defines the actuator and the nozzle chamber wall, with the exception of the nozzle chamber actuator slot. This step is shown in  FIG. 667 . 
     14. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     15. Deposit 3 microns of sacrificial material  3435 . 
     16. Etch the sacrificial layer  3435  down to glass using Mask  7 , which defines the nozzle chamber wall, with the exception of the nozzle chamber actuator slot. This step is shown in  FIG. 668 . 
     17. Deposit 1 micron of PECVD glass  3436  and planarize down to the sacrificial layer  3435  using CMP. This step is shown in  FIG. 669 . 
     18. Deposit 5 microns of sacrificial material  3437 . 
     19. Etch the sacrificial material  3437  down to glass using Mask  8 . This mask defines the nozzle chamber wall and the paddle. This step is shown in  FIG. 670 . 
     20. Deposit 3 microns of PECVD glass  3438  and planarize down to the sacrificial layer  3437  using CMP. 
     21. Deposit 1 micron of sacrificial material  3439 . 
     22. Etch the sacrificial material  3439  down to glass using Mask  9 . This mask defines the nozzle chamber wall. This step is shown in  FIG. 671 . 
     23. Deposit 3 microns of PECVD glass  3440 . 
     24. Etch to a depth of (approx.) 1 micron using Mask  3410 . This mask defines the nozzle rim  3403 . This step is shown in  FIG. 672 . 
     25. Etch down to the sacrificial layer  3439  using Mask  11 . This mask defines the roof of the nozzle chamber, and the nozzle itself. This step is shown in  FIG. 673 . 
     26. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  12 . This mask defines the ink inlets  3421  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 674 . 
     27. Etch the sacrificial material  3430 ,  3435 ,  3437 ,  3439 . The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 675 . 
     28. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     29. the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     30. Hydrophobize the front surface of the print heads. 
     31. Fill the completed print heads with ink  3441  and test them. A filled nozzle is shown in  FIG. 676 . 
     IJ35 
     In a preferred embodiment, there is provided an inkjet printing arrangement arranged on a silicon wafer. The ink is supplied to a first surface of the silicon wafer by means of channels etched through the back of the wafer to an ink ejection chamber located along the surface of the wafer. The ink ejection chamber is filled with ink and includes a paddle attached to an external actuator which is activated so as to compress a portion of the ink within the chamber against a sidewall resulting in the corresponding ejection of ink from the chamber. 
       FIG. 677  illustrates an ink ejection arrangement  3501  of the invention in the quiescent position with  FIG. 678  illustrating the view arrangement  3501  after activation of a thermal actuator  3507  and  FIG. 679  illustrates an exploded perspective view of the ink ejection arrangement  3501 . 
     Ink is supplied to an ink ejection chamber  3502  from an ink supply channel  3503  which is etched through the wafer  3504 . A paddle  3506  is located in the ink ejection chamber  3502  and attached to a thermal actuator  3507 . When the actuator  3507  is activated, the paddle  3506  is moved as illustrated in  FIG. 678  thereby displacing ink within the ink ejection chamber  3502  resulting in the ejection of the ink from the chamber  3502 . The actuator  3507  comprises a coiled arm which is in turn made up of three sub-arm components. 
     Turning to  FIG. 680 , there is illustrated a section through the line IV-IV of  FIG. 677  illustrating the structure of the arm which includes an upper conductive arm  3510  and a lower conductive arm  3511 . The two arms can be made from conductive titanium diboride which has a high Young&#39;s modulus in addition to a suitably high coefficient of thermal expansion. The two arms  3510 ,  3511  are encased in a silicon nitride portion  3512  of the arm. The two arms  3510 ,  3511  are conductively interconnected at one end  3513  ( FIG. 677 ) of the actuator  3507  and, at the other end, they are electrically interconnected at  3514 ,  3515 , respectively, to control circuitry to a lower CMOS layer  3517  which includes the drive circuitry for activating the actuator  3507 . 
     The conductive heating of the arms  3510 ,  3511  results in a general expansion of these two arms  3510 ,  3511 . The expansion works against the nitride portion  3512  of the arm resulting in a partial “uncoiling” of the actuator  3507  which in turn results in a corresponding movement of the paddle  3506  resulting in the ejection of ink from the nozzle chamber  3502 . The nozzle chamber  3502  can include a rim  3518  which, for convenience, can also be constructed from titanium diboride. The rim  3518  has an arcuate profile shown at  3519  which is shaped to guide the paddle  3506  on an arcuate path. Walls defining the ink ejection chamber  3502  are similarly profiled. Upon the ejection of a drop, the paddle  3506  returns to its quiescent position. 
     In  FIGS. 681-700 , there is shown manufacturing processing steps involved in the fabrication of a preferred embodiment. 
     1. Starting initially with  FIG. 681 , a starting point for manufacture is a silicon wafer having a CMOS layer  3517  which can comprise the normal CMOS processes including multi-level metal layers etc. and which provide the electrical circuitry for the operation of a preferred embodiment which can be formed as part of a multiple series or array of nozzles at a single time on a single wafer. 
     2. The next step in the construction of a preferred embodiment is to form an etched pit  3521  as illustrated in  FIG. 682 . The etched pit  3521  can be formed utilizing a highly anisotropic trench etcher such as that available from Silicon Technology Systems of the United Kingdom. The pit  3521  is preferably etched to have steep sidewalls. A dry etch system capable of high aspect ratio deep silicon trench etching is that known as the Advance Silicon Etch System available from Surface Technology Systems of the United Kingdom. 
     3. Next, as illustrated in  FIG. 683 , a 1 micron layer of aluminum  3522  is deposited over the surface of the wafer. 
     4. Next, as illustrated in  FIG. 684  a five micron glass layer  3523  is deposited on top of the aluminum layer  3522 . 
     5. Next, the glass layer  3523  is chemically and/or mechanically planarized to provide a 1 micron thick layer of glass over the aluminum layer  3522  as illustrated in  FIG. 685 . 
     6. A triple masked etch process is then utilized to etch the deposited layer as illustrated in  FIG. 686 . The etch includes a 1.5 micron etch of the glass layer  3523 . The etch defines the via  3525 , a trench for rim portions  3526 ,  3527  and a paddle portion  3528 . 
     7. Next, as illustrated in  FIG. 687 , a 0.9 micron layer  3560  of titanium diboride is deposited. 
     8. The titanium diboride layer  3560  is subsequently masked and etched to leave those portions as illustrated in  FIG. 688 . 
     9. A 1 micron layer of silicon dioxide (SiO 2 ) is then deposited and chemically and/or mechanically planarized as illustrated in  FIG. 689  to a level of the titanium diboride. 
     10. As illustrated in  FIG. 690  the silicon dioxide layer  3561  is then etched to form a spiral pattern where a nitride layer will later be deposited. The spiral pattern includes etched portions  3530 - 3532 . 
     11. Next, as illustrated in  FIG. 691 , a 0.2 micron layer  3562  of the silicon nitride is deposited. 
     12. The silicon nitride layer  3562  is then etched in areas  3534 - 3536  to provide for electrical interconnection in areas  3534 ,  3535 , in addition to a mechanical interconnection, as will become more apparent hereinafter, in the area  3536  as shown in  FIG. 692 . 
     13. As shown in  FIG. 693 , a 0.9 micron layer  3563  of titanium diboride is then deposited. 
     14. The titanium diboride is then etched to leave the via structure  3514  the spiral structure  3510  and the paddle arm  3506 , as shown in  FIG. 694 . 
     15. A 1 micron layer  3564  of silicon nitride is then deposited as illustrated in  FIG. 695 . 
     16. The nitride layer  3564  is then chemically and mechanically planarized to the level of the titanium diboride layer  3563  as shown in  FIG. 696 . 
     17. The silicon nitride layer  3564  is then etched so as to form the silicon nitride portions of a spiral arm  3542 ,  3543  with a thin portion of silicon nitride also remaining under the paddle arm as shown in  FIG. 697 . 
     18. As shown in  FIG. 698  an ink supply channel  3503  can be etched from a back of the wafer  3504 . Again, an STS deep silicon trench etcher can be utilized. 
     19. The next step is a wet etch of all exposed glass (SiO 2 ) surfaces of the wafer  3504  which results in a substantial release of the paddle structure as illustrated in  FIG. 699 . 
     20. Finally, as illustrated in  FIG. 700 , the exposed aluminum surfaces are then wet etched away resulting in a release of the paddle structure which springs back to its quiescent or return position ready for operation. 
     The wafer can then be separated into printhead units and interconnected to an ink supply along the back surface of the wafer for the supply of ink to the nozzle arrangement. 
     In  FIG. 701 , there is illustrated a portion  3549  of an array of nozzles which can include a three color output including a first color series  3550 , second color series  3551  and third color series  3552 . Each color series is further divided into two rows  3554  of ink ejection units with each unit providing for the ejection ink drops corresponding to a single pixel of a line. Hence, a page width array of nozzles can be formed including appropriate bond pads  3555  for providing electrical interconnection. The page width printhead can be formed with a silicon wafer with multiple printheads being formed simultaneously using the aforementioned steps. Subsequently, the printheads can be separated and joined to an ink supply mechanism for supplying ink via the back of the wafer to each ink ejection arrangement, the supply being suitably arranged for providing separate colors. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double-sided polished wafer  3504 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process layer  3517 . Relevant features of the wafer  3504  at this step are shown in  FIG. 703 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 702  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide down to silicon or aluminum using Mask  1 . This mask defines the ink inlet, the heater contact vias, and the edges of the printhead chips. This step is shown in  FIG. 704 . 
     3. Etch silicon to a depth of 10 microns using the etched oxide as a mask. This step is shown in  FIG. 705 . 
     4. Deposit 1 micron of sacrificial material  3522  (e.g. aluminum). This step is shown in  FIG. 706 . 
     5. Deposit 10 microns of a second sacrificial material  3570  (e.g. polyimide). This fills the etched silicon hole. 
     6. Planarize using CMP to the level of the first sacrificial material  3522 . This step is shown in  FIG. 707 . 
     7. Etch the first sacrificial layer  3522  using Mask  2 , defining the nozzle chamber wall and the actuator anchor point  3525 . This step is shown in  FIG. 708 . 
     8. Deposit 1 micron of glass  3571 . 
     9. Etch the glass  3571  and second sacrificial layer  3570  using Mask  3 . This mask defines the lower layer of the actuator loop, the nozzle chamber wall, and the lower section of the paddle. 
     10. Deposit 1 micron of heater material  3572 , for example titanium nitride (TiN) or titanium diboride (TiB2). Planarize using CMP. Steps 8 to 10 form a ‘damascene’ process. This step is shown in  FIG. 709 . 
     11. Deposit 0.1 micron of silicon nitride  3573 . 
     12. Deposit 1 micron of glass  3574 . 
     13. Etch the glass  3574  using Mask  4 , which defines the upper layer of the actuator loop, the arm to the paddle, and the upper section of the paddle. 
     14. Etch the silicon nitride  3573  using Mask  5 , which defines the vias connecting the upper layer of the actuator loop to the lower layer of the actuator loop, as well as the arm to the paddle, and the upper section of the paddle. 
     15. Deposit 1 micron of the same heater material  3575  as in step 10. Planarize using CMP. Steps 11 to 15 form a ‘dual damascene’ process. This step is shown in  FIG. 710 . 
     16. Etch the glass and nitride down to the sacrificial layer  3522  using Mask  6 , which defines the actuator. This step is shown in  FIG. 711 . 
     17. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     18. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  7 . This mask defines the ink inlets  3503  which are etched through the wafer  3504 . The wafer  3504  is also diced by this etch. This step is shown in  FIG. 712 . 
     19. Etch both sacrificial materials  3522 ,  3570 . The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 713 . 
     20. Mount the chips in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets  3503  at the back of the wafer. 
     21. Connect the chips to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     22. Fill the printhead with water. Hydrophobize the exposed portions of the printhead by exposing the printhead to a vapor of a perfluorinated alkyl trichlorosilane. Drain the water and dry the printhead. 
     23. Fill the completed printhead with ink  3576  and test it. A filled nozzle is shown in  FIG. 714 . 
     IJ36 
     In a preferred embodiment, there is provided an inkjet printhead having an array of nozzles wherein the nozzles are grouped in pairs and each pair is provided with a single actuator which is actuated so as to move a paddle type mechanism to force the ejection of ink out of one or other of the nozzle pairs. The paired nozzles eject ink from a single nozzle chamber which is resupplied by means of an ink supply channel. Further, the actuator of a preferred embodiment has unique characteristics so as to simplify the actuation process. 
     Turning initially to  FIGS. 715 to 719 , there will now be explained the principles of operation of a preferred embodiment. In a preferred embodiment, a single nozzle chamber  3601  is utilized to supply ink two ink ejection nozzles  3602 ,  3603 . Ink is resupplied to the nozzle chamber  3601  via means of an ink supply channel  3605 . In its quiescent position, to ink menisci  3606 ,  3607  are formed around the ink ejection holes  3602 ,  3603 . The arrangement of  FIG. 715  being substantially axially symmetric around a central paddle  3609  which is attached to an actuator mechanism. 
     When it is desired to eject ink out of one of the nozzles, say nozzle  3603 , the paddle  3609  is actuated so that it begins to move as indicated in  FIG. 716 . The movement of paddle  3609  in the direction  3610  results in a general compression of the ink on the right hand side of the paddle  3609 . The compression of the ink results in the meniscus  3607  growing as the ink is forced out of the nozzles  3603 . Further, the meniscus  3606  undergoes an inversion as the ink is sucked back on the left hand side of the actuator  3610  with additional ink  3612  being sucked in from ink supply channel  3605 . The paddle actuator  3609  eventually comes to rest and begins to return as illustrated in  FIG. 717 . The ink  3613  within meniscus  3607  has substantial forward momentum and continues away from the nozzle chamber whilst the paddle  3609  causes ink to be sucked back into the nozzle chamber. Further, the surface tension on the meniscus  3606  results in further in flow of the ink via the ink supply channel  3605 . The resolution of the forces at work in the resultant flows results in a general necking and subsequent breaking of the meniscus  3607  as illustrated in  FIG. 718  wherein a drop  3614  is formed which continues onto the media or the like. The paddle  3609  continues to return to its quiescent position. 
     Next, as illustrated in  FIG. 719 , the paddle  3609  returns to its quiescent position and the nozzle chamber refills by means of surface tension effects acting on meniscuses  3606 ,  3607  with the arrangement of returning to that showing in  FIG. 715 . When required, the actuator  3609  can be activated to eject ink out of the nozzle  3602  in a symmetrical manner to that described with reference to  FIGS. 715-719 . Hence, a single actuator  3609  is activated to provide for ejection out of multiple nozzles. The dual nozzle arrangement has a number of advantages including in that movement of actuator  3609  does not result in a significant vacuum forming on the back surface of the actuator  3609  as a result of its rapid movement. Rather, meniscus  3606  acts to ease the vacuum and further acts as a “pump” for the pumping of ink into the nozzle chamber. Further, the nozzle chamber is provided with a lip  3615  ( FIG. 716 ) which assists in equalizing the increase in pressure around the ink ejection holes  3603  which allows for the meniscus  3607  to grow in an actually symmetric manner thereby allowing for straight break off of the drop  3614 . 
     Turning now to  FIGS. 720 and 721 , there is illustrated a suitable nozzle arrangement with  FIG. 720  showing a single side perspective view and  FIG. 721  showing a view, partly in section illustrating the nozzle chamber. The actuator  3620  includes a pivot arm attached at the post  3621 . The pivot arm includes an internal core portion  3622  which can be constructed from glass. On each side  3623 ,  3624  of the internal portion  3622  is two separately control heater arms which can be constructed from an alloy of copper and nickel (45% copper and 55% nickel). The utilization of the glass core is advantageous in that it has a low coefficient thermal expansion and coefficient of thermal conductivity. Hence, any energy utilized in the heaters  3623 ,  3624  is substantially maintained in the heater structure and utilized to expand the heater structure and opposed to an expansion of the glass core  3622 . Structure or material chosen to form part of the heater structure preferably has a high “bend efficiency”. One form of definition of bend efficiency can be the Young&#39;s modulus times the coefficient of thermal expansion divided by the density and by the specific heat capacity. 
     The copper nickel alloy in addition to being conductive has a high coefficient of thermal expansion, a low specific heat and density in addition to a high Young&#39;s modulus. It is therefore a highly suitable material for construction of the heater element although other materials would also be suitable. 
     Each of the heater elements can comprise a conductive out and return trace with the traces being insulated from one and other along the length of the trace and conductively joined together at the far end of the trace. The current supply for the heater can come from a lower electrical layer via the pivot anchor  3621 . At one end of the actuator  3620 , there is provided a bifurcated portion  3630  which has attached at one end thereof to leaf portions  3631 ,  3632 . 
     To operate the actuator, one of the arms  3623 ,  3624  e.g.  3623  is heated in air by passing current through it The heating of the arm results in a general expansion of the arm. The expansion of the arm results in a general bending of the arm  3620 . The bending of the arm  3620  further results in leaf portion  3632  pulling on the paddle portion  3609 . The paddle  3609  is pivoted around a fulcrum point by means of attachment to leaf portions  3638 ,  3639  which are generally thin to allow for minor flexing. The pivoting of the arm  3609  causes ejection of ink from the nozzle hole  3640 . The heater is deactivated resulting in a return of the actuator  3620  to its quiescent position and its corresponding return of the paddle  3609  also to is quiescent position. Subsequently, to eject ink out of the other nozzle hole  3641 , the heater  3624  can be activated with the paddle operating in a substantially symmetric manner. 
     It can therefore be seen that the actuator can be utilized to move the paddle  3609  on demand so as to eject drops out of the ink ejection hole e.g.  3640  with the ink refilling via an ink supply channel  3644  ( FIG. 721 ) located under the paddle  3609 . 
     The nozzle arrangement of a preferred embodiment can be formed on a silicon wafer utilizing standard semi-conductor fabrication processing steps and micro-electro-mechanical systems (MEMS) construction techniques. 
     Preferably, a large wafer of printheads is constructed at any one time with each printhead providing a predetermined pagewidth capabilities and a single printhead can in turn comprise multiple colors so as to provide for full color output as would be readily apparent to those skilled in the art Turning now to  FIG. 722-FIG .  741  there will now be explained one form of fabrication of a preferred embodiment A preferred embodiment can start as illustrated in  FIG. 722  with a CMOS processed silicon wafer  3650  which can include a standard CMOS layer  3651  including of the relevant electrical circuitry etc. The processing steps can then be as follows:
     As illustrated in  FIG. 723 , a deep etch of the nozzle chamber  3698  is performed to a depth of 25 micron;   As illustrated in  FIG. 724 , a 27 micron layer of sacrificial material  3652  such as aluminum is deposited;   As illustrated in  FIG. 725 , the sacrificial material is etched to a depth of 26 micron using a glass stop so as to form cavities using a paddle and nozzle mask.   As illustrated in  FIG. 726 , a 2 micron layer of low stress glass  3653  is deposited.   As illustrated in  FIG. 727 , the glass is etched to the aluminum layer utilizing a first heater via mask.   As illustrated in  FIG. 728 , a 2 micron layer of 60% copper and 40% nickel is deposited  3655  and planarized ( FIG. 729 ) using chemical mechanical planarization (CMP).   As illustrated in  FIG. 730 , a 0.1 micron layer of silicon nitride is deposited  3656  and etched using a heater insulation mask.   As illustrated in  FIG. 731 , a 2 micron layer of low stress glass  3657  is deposited and etched using a second heater mask.   As illustrated in  FIG. 732 , a 2 micron layer of 60% copper and 40% nickel  3658  is deposited and planarized ( FIG. 733 ) using chemical mechanical planarization.   As illustrated in  FIG. 734 , a 1 micron layer of low stress glass  3660  is deposited and etched ( FIG. 735 ) using a nozzle wall mask.   As illustrated in  FIG. 736 , the glass is etched down to the sacrificial layer using an actuator paddle wall mask.   As illustrated in  FIG. 737 , a 5 micron layer of sacrificial material  3662  is deposited and planarized using CMP.   As illustrated in  FIG. 738 , a 3 micron layer of low stress glass  3663  is deposited and etched using a nozzle rim mask.   As illustrated in  FIG. 739 , the glass is etched down to the sacrificial layer using nozzle mask.   As illustrated in  FIG. 740 , the wafer can be etched from the back using a deep silicon trench etcher such as the Silicon Technology Systems deep trench etcher.   Finally, as illustrated in  FIG. 741 , the sacrificial layers are etched away releasing the ink jet structure.   

     Subsequently, the print head can be washed, mounted on an ink chamber, relevant electrical interconnections TAB bonded and the print head tested. 
     Turning now to  FIG. 742 , there is illustrated a portion of a full color printhead which is divided into three series of nozzles  3671 ,  3672  and  3673 . Each series can supply a separate color via means of a corresponding ink supply channel. Each series is further subdivided into two sub-rows e.g.  3676 ,  3677  with the relevant nozzles of each sub-row being fired simultaneously with one sub-row being fired a predetermined time after a second sub-row such that a line of ink drops is formed on a page. 
     As illustrated in  FIG. 742  the actuators a formed in a curved relationship with respect to the main nozzle access so as to provide for a more compact packing of the nozzles. Further, the block portion ( 3621  of  FIG. 720 ) is formed in the wall of an adjacent series with the block portion of the row  3673  being formed in a separate guide rail  3680  provided as an abutment surface for the TAB strip when it is abutted against the guide rail  3680  so as to provide for an accurate registration of the tab strip with respect to the bond pads  3681 ,  3682  which are provided along the length of the printhead so as to provide for low impedance driving of the actuators. 
     The principles of a preferred embodiment can obviously be readily extended to other structures. For example, a fulcrum arrangement could be constructed which includes two arms which are pivoted around a thinned wall by means of their attachment to a cross bar. Each arm could be attached to the central cross bar by means of similarly leafed portions to that shown in  FIG. 720  and  FIG. 721 . The distance between a first arm and the thinned wall can be L units whereas the distance between the second arm and wall can be NL units. Hence, when a translational movement is applied to the second arm for a distance of N x X units the first arm undergoes a corresponding movement of X units. The leafed portions allow for flexible movement of the arms whilst providing for full pulling strength when required. 
     It would be evident to those skilled in the art that the present invention can further be utilized in either mechanical arrangements requiring the application forces to induce movement in a structure. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  3650 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  3651 . Relevant features of the wafer at this step are shown in  FIG. 744 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 743  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide down to silicon or aluminum using Mask  1 . This mask defines the ink inlet, the heater contact vias, and the edges of the print head chips. This step is shown in  FIG. 745 . 
     3. Etch exposed silicon  3650  to a depth of 20 microns. This step is shown in  FIG. 746 . 
     4. Deposit a 1 micron conformal layer of a first sacrificial material  3691 . 
     5. Deposit 20 microns of a second sacrificial material  3692 , and planarize down to the first sacrificial layer using CMP. This step is shown in  FIG. 747 . 
     6. Etch the first sacrificial layer using Mask  2 , defining the nozzle chamber wall  3693 , the paddle  3609 , and the actuator anchor point  3621 . This step is shown in  FIG. 748 . 
     7. Etch the second sacrificial layer down to the first sacrificial layer using Mask  3 . This mask defines the paddle  3609 . This step is shown in  FIG. 749 . 
     8. Deposit a 1 micron conformal layer of PECVD glass  3653 . 
     9. Etch the glass using Mask  4 , which defines the lower layer of the actuator loop. 
     10. Deposit 1 micron of heater material  3655 , for example titanium nitride (TiN) or titanium diboride (TiB 2 ). 
     Planarize using CMP. This step is shown in  FIG. 750 . 
     11. Deposit 0.1 micron of silicon nitride  3656 . 
     12. Deposit 1 micron of PECVD glass  3657 . 
     13. Etch the glass using Mask  5 , which defines the upper layer of the actuator loop. 
     14. Etch the silicon nitride using Mask  6 , which defines the vias connecting the upper layer of the actuator loop to the lower layer of the actuator loop. 
     15. Deposit 1 micron of the same heater material  3658  previously deposited. Planarize using CMP. This step is shown in  FIG. 751 . 
     16. Deposit 1 micron of PECVD glass  3660 . 
     17. Etch the glass down to the sacrificial layer using Mask  6 . This mask defines the actuator and the nozzle chamber wall, with the exception of the nozzle chamber actuator slot. This step is shown in  FIG. 752 . 
     18. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     19. Deposit 4 microns of sacrificial material  3662  and planarize down to glass using CMP. 
     20. Deposit 3 microns of PECVD glass  3663 . This step is shown in  FIG. 753 . 
     21. Etch to a depth of (approx.) 1 micron using Mask  7 . This mask defines the nozzle rim  3695 . This step is shown in  FIG. 754 . 
     22. Etch down to the sacrificial layer using Mask  8 . This mask defines the roof of the nozzle chamber, and the nozzle  3640 ,  3641  itself. This step is shown in  FIG. 755 . 
     23. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  9 . This mask defines the ink inlets  3665  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 756 . 
     24. Etch both types of sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 757 . 
     25. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
       26 . Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     27. Hydrophobize the front surface of the print heads. 
     28. Fill the completed print heads with ink  3696  and test them. A filled nozzle is shown in  FIG. 758 . 
     IJ37 
     In a preferred embodiment, an inkjet printing system is provided for the projection of ink from a series of nozzles. In a preferred embodiment a single paddle is located within a nozzle chamber and attached to an actuator device. When the nozzle is actuated in a first direction, ink is ejected through a first nozzle aperture and when the actuator is activated in a second direction causing the paddle to move in a second direction, ink is ejected out of a second nozzle. Turning initially to  FIGS. 759-763 , there will now be illustrated in a schematic form, the operational principles of a preferred embodiment 
     Turning initially to  FIG. 759 , there is shown a nozzle arrangement  3701  of a preferred embodiment when in its quiescent state. In the quiescent state, ink fills a first portion  3702  of the nozzle chamber and a second portion  3703  of the nozzle chamber. A baffle is situated between the first portion  3702  and the second portion  3703  of the nozzle chamber. The ink fills the nozzle chambers from an ink supply channel  3705  to the point that a meniscus  3706 ,  3707  is formed around corresponding nozzle holes  3708 ,  3709 . A paddle  3710  is provided within the nozzle chamber  3702  with the paddle  3710  being interconnected to an actuator device  3712  which can comprise a thermal actuator which can be actuated so as to cause the actuator  3712  to bend, as will be become more apparent hereinafter. 
     In order to eject ink from the first nozzle hole  3709 , the actuator  3712 , which can comprise a thermal actuator, is activated so as to bend as illustrated in  FIG. 760 . The bending of actuator  3712  causes the paddle  3710  to rapidly move upwards which causes a substantial increase in the pressure of the fluid, such as ink, within nozzle chamber  3702  and adjacent to the meniscus  3707 . This results in a general rapid expansion of the meniscus  3707  as ink flows through the nozzle hole  3709  with result of the increasing pressure. The rapid movement of paddle  3710  causes a reduction in pressure along the back surface of the paddle  3710 . This results in general flows as indicated  3717 ,  3718  from the second nozzle chamber and the ink supply channel. Next, while the meniscus  3707  is extended, the actuator  3712  is deactivated resulting in the return of the paddle  3710  to its quiescent position as indicated in  FIG. 761 . The return of the paddle  3710  operates against the forward momentum of the ink adjacent the meniscus  3707  which subsequently results in the breaking off of the meniscus  3707  so as to form the drop  3720  as illustrated in  FIG. 761 . The drop  3720  continues onto the print media. Further, surface tension effects on the ink meniscus  3707  and ink meniscus  3706  result in ink flows  3721 - 3723  which replenish the nozzle chambers. Eventually, the paddle  3710  returns to its quiescent position and the situation is again as illustrated in  FIG. 759 . 
     Subsequently, when it is desired to eject a drop via ink ejection hole  3708 , the actuator  3712  is activated as illustrated in  FIG. 762 . The actuation  3712  causes the paddle  3710  to move rapidly down causing a substantial increase in pressure in the nozzle chamber  3703  which results in a rapid growth of the meniscus  3706  around the nozzle hole  3708 . This rapid growth is accompanied by a general collapse in meniscus  3707  as the ink is sucked back into the chamber  3702 . Further, ink flow also occurs into ink supply channel  3705  however, hopefully this ink flow is minimized. Subsequently, as indicated in  FIG. 763 , the actuator  3712  is deactivated resulting in the return of the paddle  3710  to is quiescent position. The return of the paddle  3710  results in a general lessening of pressure within the nozzle chamber  3703  as ink is sucked back into the area under the paddle  3710 . The forward momentum of the ink surrounding the meniscus  3706  and the backward momentum of the other ink within nozzle chamber  3703  is resolved through the breaking off of an ink drop  3725  which proceeds towards the print media. Subsequently, the surface tension on the meniscus  3706  and  3707  results in a general ink inflow from nozzle chamber  3703  resulting, in the arrangement returning to the quiescent state as indicated in  FIG. 759 . 
     It can therefore be seen that the schematic illustration of  FIG. 759  to  FIG. 763  describes a system where a single planar paddle is actuated so as to eject ink from multiple nozzles. 
     Turning now to  FIG. 764 , there is illustrated a sectional view through one form of implementation of a single nozzle arrangement  3701 . The nozzle arrangement  3701  can be constructed on a silicon wafer base  3728  through the construction of large arrays of nozzles at one time using standard micro electro mechanical processing techniques. 
     An array of nozzles on a silicon wafer device and can be constructed using semiconductor processing techniques in addition to micro machining and micro fabrication process technology (MEMS) and a full familiarity with these technologies is hereinafter assumed. 
     One form of construction will now be described with reference to  FIGS. 765 to 782 . On top of the silicon wafer  3728  is first constructed a CMOS processing layer  3729  which can provide for the necessary interface circuitry for driving the thermal actuator and its interconnection with the outside world. The CMOS layer  3729  being suitably passivated so as to protect it from subsequent MEMS processing techniques. The walls e.g.  3730  can be formed from glass (SiO 2 ). Preferably, the paddle  3710  includes a thinned portion  3732  for more efficient operation. Additionally, a sacrificial etchant hole  3733  is provided for allowing more effective etching of sacrificial etchants within the nozzle chamber  3702 . The ink supply channel  3705  is generally provided for interconnecting an ink supply conduit  3734  which can be etched through the wafer  3728  by means of a deep anisotropic trench etcher such as that available from Silicon Technology Systems of the United Kingdom. 
     The arrangement  3701  further includes a thermal actuator device e.g.  3712  which includes two arms comprising an upper arm  3736  and a lower arm  3737  extending from a port  3754  and formed around a glass core  3738 . Both upper and lower arm heaters  3736 ,  3737  can comprise a 0.4 μm film of 60% copper and 40% nickel hereinafter known as (Cupronickel) alloy. Copper and nickel is used because it has a high bend efficiency and is also highly compatible with standard VLSI and MEMS processing techniques. The bend efficiency can be calculated as the square of the coefficient of the thermal expansion times the Young&#39;s modulus, divided by the density and divided by the heat capacity. This provides a measure of the amount of “bend energy” produced by a material per unit of thermal (and therefore electrical) energy supplied. 
     The core can be fabricated from glass which also has many suitable properties in acting as part of the thermal actuator. The actuator  3712  includes a thinned portion  3740  for providing an interconnect between the actuator and the paddle  3710 . The thinned portion  3740  provides for non-destructive flexing of the actuator  3712 . Hence, when it is desired to actuate the actuator  3712 , say to cause it to bend downwards, a current is passed down through the top cupronickel layer causing it to be heated and expand. This in turn causes a general bending due to the thermocouple relationship between the layers  3736  and  3738 . The bending down of the actuator  3736  also causes thinned portion  3740  to move downwards in addition to the portion  3741 . Hence, the paddle  3710  is pivoted around the wall  3741  which can, if necessary, include slots for providing for efficient bending. Similarly, the heater coil  3737  can be operated so as to cause the actuator  3712  to bend up with the consequential movement upon the paddle  3710 . 
     A pit  3739  is provided adjacent to the wall of the nozzle chamber to ensure that any ink outside of the nozzle chamber has minimal opportunity to “wick” along the surface of the printhead as, the wall  3741  can be provided with a series of slots to assist in the flexing of the fulcrum. 
     Turning now to  FIGS. 765-782 , there will now be described one form of processing construction of a preferred embodiment of  FIG. 764 . This can involve the following steps: 
     1. Initially, as illustrated in  FIG. 765 , starting with a fully processed CMOS wafer  3728  the CMOS layer  3729  is deep silicon etched so as to provide for the nozzle ink inlet  3705 . 
     2. Next, as illustrated in  FIG. 766 , a 7 micron layer  3742  of a suitable sacrificial material (for example, aluminum), is deposited and etched with a nozzle wall mask in addition to the electrical interconnect mask. 
     3. Next, as illustrated in  FIG. 767 , a 7 micron layer of low stress glass  3743  is deposited and planarized using chemical planarization. 
     4. Next, as illustrated in  FIG. 768 , the sacrificial material is etched to a depth of 0.4 micron and the glass to at least a level of 0.4 micron utilizing a first heater mask. 
     5. Next, as illustrated in  FIG. 769 , the glass layer is etched  3745 ,  3746  down to the aluminum portions of the CMOS layer  3704  providing for an electrical interconnect using a first heater via mask. 
     6. Next, as illustrated in  FIG. 770 , a 3 micron layer  3748  of 50% copper and 40% nickel alloy is deposited and planarized using chemical mechanical planarization. 
     7. Next, as illustrated in  FIG. 771 , a 4 micron layer  3749  of low stress glass is deposited and etched to a depth of 0.5 micron utilizing a mask for the second heater. 
     8. Next, as illustrated in  FIG. 772 , the deposited glass layer is etched  3750  down to the cupronickel using a second heater via mask. 
     9. Next, as illustrated in  FIG. 773 , a 3 micron layer  3751  of cupronickel is deposited  3751  and planarized using chemical mechanical planarization. 
     10. As illustrated in  FIG. 774 , next, a 7 micron layer  3752  of low stress glass is deposited. 
     11. The glass  3752  is etched, as illustrated in  FIG. 775  to a depth of 1 micron utilizing a first paddle mask. 
     12. Next, as illustrated in  FIG. 776 , the glass  3752  is again etched to a depth of 3 micron utilizing a second paddle mask with the first mask utilized in  FIG. 775  etching away those areas not having any portion of the paddle and the second mask as illustrated in  FIG. 776  etching away those areas having a thinned portion. Both the first and second mask of  FIG. 775  and  FIG. 776  can be a timed etch. 
     13. Next, as illustrated in  FIG. 777 , the glass  3752  is etched to a depth of 7 micron using a third paddle mask The third paddle mask leaving the nozzle wall  3730 , baffle  3711 , thinned wall  3741  and end portion  3754  which fixes one end of the thermal actuator firmly to the substrate. 
     14. The next step, as illustrated in  FIG. 778 , is to deposit an 11 micron layer  3755  of sacrificial material such as aluminum and planarize the layer utilizing chemical mechanical planarization. 
     15. As illustrated in  FIG. 779 , a 3 micron layer  3756  of glass is deposited and etched to a depth of 1 micron utilizing a nozzle rim mask. 
     16. Next, as illustrated in  FIG. 780 , the glass  3756  is etched down to the sacrificial layer using a nozzle mask so as to form the nozzle structure  3758 . 
     17. The next step, as illustrated in  FIG. 781 , is to back etch an ink supply channel  3734  using a deep silicon trench etcher such as that available from Silicon Technology Systems. The printheads can also be diced by this etch. 
     18. Next, as illustrated in  FIG. 782 , the sacrificial layers are etched away by means of a wet etch and wash 
     The printheads can then be inserted in an ink chamber molding, tab bonded and a PTFE hydrophobic layer evaporated over the surface so as to provide for a hydrophobic surface. 
     In  FIG. 783 , there is illustrated a portion of a page with printhead including a series of nozzle arrangements as constructed in accordance with the principles of a preferred embodiment. The array  3760  has been constructed for three color output having a first row  3761  a second row  3762  and a third row  3763 . Additionally, a series of bond pads, e.g.  3764 ,  3765  are provided at the side for tab automated bonding to the printhead. Each row  3761 ,  3762 ,  3763  can be provided with a different color ink including cyan, magenta and yellow for providing full color output. The nozzles of each row  3761 - 3763  are further divided into sub rows e.g.  3768 ,  3769 . Further, a glass strip  3770  can be provided for anchoring the actuators of the row  3763  in addition to providing for alignment for the bond pad  3764 ,  3765 . 
     The CMOS circuitry can be provided so as to fire the nozzles with the correct timing relationships. For example, each nozzle in the row  3768  is fired together followed by each nozzle in the row  3769  such that a single line is printed. 
     It could be therefore seen that a preferred embodiment provides for an extremely compact arrangement of an inkjet printhead which can be made in a highly inexpensive manner in large numbers on a single silicon wafer with large numbers of printheads being made simultaneously. Further, the actuation mechanism provides for simplified complexity in that the number of actuators is halved with the arrangement of a preferred embodiment 
     One alternative form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  3728 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  3729 . Relevant features of the wafer at this step are shown in  FIG. 785 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 784  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide down to silicon or, aluminum using Mask  1 . This mask defines the ink inlet hole. 
     3. Etch silicon to a depth of 15 microns using etched oxide as a mask. The sidewall slope of this etch is not critical (75 to 90 degrees is acceptable), so standard trench etchers can be used. This step is shown in  FIG. 786 . 
     4. Deposit 7 microns of sacrificial aluminum  3742 . 
     5. Etch the sacrificial layer using Mask  2 , which defines the nozzle walls e.g.  3730  and actuator anchor  3754 . This step is shown in  FIG. 787 . 
     6. Deposit 7 microns of low stress glass  3743  and planarize down to aluminum using CMP. 
     7. Etch the sacrificial material to a depth of 0.4 microns, and glass to a depth of at least 0.4 microns, using Mask  3 . This mask defined the lower heater. This step is shown in  FIG. 788 . 
     8. Etch the glass layer down to aluminum using Mask  4 , defining heater vias  3745 ,  3746 . This step is shown in  FIG. 789 . 
     9. Deposit 1 micron of heater material  3780  (e.g. titanium nitride (TiN)) and planarize down to the sacrificial aluminum using CMP. This step is shown in  FIG. 790 . 
     10. Deposit 4 microns of low stress glass  3781 , and etch to a depth of 0.4 microns using Mask  5 . This mask defines the upper heater. This step is shown in  FIG. 791 . 
     11. Etch glass down to TiN using Mask  6 . This mask defines the upper heater vias. 
     12. Deposit 1 micron of TiN  3782  and planarize down to the glass using CMP. This step is shown in  FIG. 792 . 
     13. Deposit 7 microns of low stress glass  3783 . 
       14 . Etch glass to a depth of 1 micron using Mask  7 . This mask defines the nozzle walls e.g.  3730 , nozzle chamber baffle  3711 , the paddle, the flexure, the actuator arm, and the actuator anchor. This step is shown in  FIG. 793 . 
       15 . Etch glass to a depth of 3 microns using Mask  8 . This mask defines the nozzle walls  3730 , nozzle chamber baffle  3711 , the actuator arm  3784 , and the actuator anchor. This step is shown in  FIG. 794 . 
     16. Etch glass to a depth of 7 microns using Mask  9 . This mask defines the nozzle walls and the actuator anchor. This step is shown in  FIG. 795 . 
     17. Deposit 11 microns of sacrificial aluminum  3786  and planarize down to glass using CMP. This step is shown in  FIG. 796 . 
     18. Deposit 3 microns of PECVD glass  3787 . 
     19. Etch glass to a depth of 1 micron using Mask  10 , which defines the nozzle rims  3788 . This step is shown in  FIG. 797 . 
     20. Etch glass down to the sacrificial layer (3 microns) using Mask  11 , defining the nozzles  3708  and the nozzle chamber roof. This step is shown in  FIG. 798 . 
     21. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     22. Back-etch the silicon wafer to within approximately 10 microns of the front surface using Mask  12 . This mask defines the ink inlets  3734  which are etched through the wafer. The wafer is also diced by this etch. This etch can be achieved with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems. This step is shown in  FIG. 799 . 
     23. Etch all of the sacrificial aluminum. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 800 . 
     24. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     25. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     26. Hydrophobize the front surface of the printheads. 
     27. Fill the completed printheads with ink  3789  and test them. A filled nozzle is shown in  FIG. 801 . 
     IJ38 
     A preferred embodiment of the present invention includes an inkjet nozzle arrangement wherein a single actuator drives two output nozzles. When the actuator is driven in the first direction, ink is ejected out of a first ink ejection port and when the actuator is driven in a second direction, ink is ejected out of a second ink ejection port. The paddle actuator is interconnected via a slot in the nozzle chamber wall to a rigid thermal actuator which can be actuated so as to cause the ejection of ink from the ink ejection ports. 
     Turning initially to  FIG. 807 and 808 , there is illustrated a nozzle arrangement  3801  of a preferred embodiment with  FIG. 808  being a sectional view through the line VII-VII of  FIG. 807 . The nozzle arrangement  3801  includes two ink ejection ports  3802 ,  3803  for the ejection of ink from within a nozzle chamber. The nozzle chamber further includes first and second chamber portions  3805 ,  3806  in addition to an etched cavity  3807  which, during normal operation, are normally filled with ink supplied via an ink inlet channel  3808 . The ink inlet channel  3808  is in turn connected to an ink supply channel  3809  etched through a silicon wafer. Inside the nozzle chamber is located an actuator paddle  3810  which is interconnected through a slot  3812  in the chamber wall to an actuator arm  3813  which is actuated by means of heaters  3814 ,  3815  which are in turn connected to a substrate  3817  via an end block portion  3818  with the substrate  3817  providing the relevant electrical interconnection for the heaters  3814 ,  3815 . 
     Hence, the actuator arm  3813  can be actuated by the heaters  3814 ,  3815  to move up and down as a result of the expansion of the heaters  3814 ,  3815  so as to eject ink via the nozzle holes  3802  or  3803 . A series of holes  3820 - 3822  are also provided in a top wall of the nozzle arrangement. As will become more readily apparent hereinafter, the holes  3820 - 3822  assist in the etching of sacrificial layers during construction in addition to providing for “breathing” assistance during operation of the nozzle arrangement  3801 . The two chambers  3805 ,  3806  are separated by a baffle  3824  and the paddle arm  3810  includes a end lip portion  3825  in addition to a plug portion  3826 . The plug portion  3826  is designed to mate with the boundary of the ink inlet channel  3808  during operation. 
     Turning now to  FIGS. 802-806 , there will now be explained the operation of the nozzle arrangement  3801 . Each of  FIGS. 802-806  illustrate a cross sectional view of the nozzle arrangement during various stages of operation Turning initially to  FIG. 802 , there is shown the nozzle arrangement  3801  when in its quiescent position. In this state, the paddle  3810  is idle and ink fills the nozzle chamber so as to form menisci  3829 - 3833  and  3837 . 
     When it is desired to eject a drop out of the nozzle port  3803 , as indicated in  FIG. 804 , the bottom heater  3815  is actuated. The heater  3815  can comprise a 60% copper and 40% nickel alloy which has a high bending efficiency where the bending efficiency is defined as:
 
bend efficiency=Young&#39;s Modulus×(Coefficient of thermal Expansion)/Density×Specific Heat Capacity
 
     The two heaters  3814 ,  3815  can be constructed from the same material and normally exist in a state of balance when the paddle  3810  is in its quiescent position. As noted previously, when it is desired to eject a drop out of nozzle chamber  3803 , the heater  3815  is actuated which causes a rapid upwards movement of the actuator paddle  3810 . This causes a general increase in pressure in the area in front of the actuator paddle  3810  which further causes a rapid expansion in the meniscus  3830  in addition to a much less significant expansion in the menisci  3831 - 3833  (due to their being of a substantially smaller radius). Additionally, the substantial decrease in pressure around the back surface of the paddle  3810  causes a general inflow of ink through the ink inlet channel  3808  in addition to causing a general collapse in the meniscus  3829  and a corresponding flow of ink  3835  around the baffle  3824 . A slight bulging also occurs in the meniscus  3837  around the slot in the side wall  3812 . 
     Turning now to  FIG. 804 , the heater  3815  is merely pulsed and turned off when it reaches its maximum extent. Hence, the paddle actuator  3810  rapidly begins to return to its quiescent position causing the ink around the ejection port  3803  to begin to flow back into the chamber. The forward momentum of the ink in the expanded meniscus and the backward pressure exerted by actuator paddle  3810  results in a general necking of the meniscus and the subsequent breaking off of a separate drop  3839  which proceeds to the print media. The menisci  3829 ,  3831 ,  3832  and  3833  are then each of a generally concave shape and exert a further force on the ink within the nozzle chamber which begins to draw ink in from the ink inlet channel  3808  so as to replenish the nozzle chamber. Eventually, the nozzle arrangement  3801  returns to the quiescent position which is as previously illustrated in respect of  FIG. 802 . 
     Turning now to  FIG. 805 , when it is desired to eject a droplet of ink out of the ink ejection port  3802 , the heater  3814  is actuated resulting in a general expansion of the heater  3814  which in turn causes a rapid downward movement of the actuator paddle  3810 . The rapid downward movement causes a substantial increase in pressure within the cavity  3807  which in turn results in a general rapid expansion of the meniscus  3829 . The end plug portion  3826  results in a general blocking of the ink supply channel  3808  stopping fluid from flowing back down the ink supply channel  3808 . This further assists in causing ink to flow towards the cavity  3807 . The menisci  3830 - 3833  of  FIG. 802  are drawn generally into the nozzle chamber and may unite so as to form a single meniscus  3840 . The meniscus  3837  is also drawn into the chamber. The heater  3814  is merely pulsed, which as illustrated in  FIG. 806  results in a rapid return of the paddle  3810  to its quiescent position. The return of the paddle  3810  results in a general reduction in pressure within the cavity  3807  which in turn results in the ink around the nozzle  3802  beginning to flow  3843  back into the nozzle chamber in the direction of arrow  3843 . The forward momentum of the ink around the meniscus  3829  in addition to the backflow  3843  results in a general necking of the meniscus  3829  and the formation of an ink drop  3842  which separates from the main body of the ink and continues to the print media. 
     The return of the actuator paddle  3810  further results in plugging portion  3826  “unplugging” the ink supply channel  3808 . The general reduction in pressure in addition to the collapsed menisci  3840 ,  3837  and  3829  results in a flow of ink from the ink inlet channel  3808  into the nozzle chamber so as to cause replenishment of the nozzle chamber and return to the quiescent state as illustrated in  FIG. 802 . 
     Returning now to  FIG. 807  and  FIG. 808 , a number of other important features of a preferred embodiment include the fact that each of the ports  3802 ,  3803 , and each of the holes  3820 ,  3821 ,  3822 , and the slot  3812  etc. includes a rim around its outer periphery. The rim acts to stop wicking of the meniscus formed across the nozzle rim. Further, the actuator arm  3813  is provided with a wick minimization protrusion  3844  in addition to a series of pits  3845  which are shaped so as to minimize wicking along the surfaces surrounding the actuator arms  3813 . 
     The nozzle arrangement of a preferred embodiment can be formed on a silicon wafer utilizing standard semi-conductor fabrication processing steps and micro-electro-mechanical systems (MEMS) construction techniques. 
     Preferably, a large wafer of printheads is constructed at any one time with each printhead providing a predetermined pagewidth capabilities and a single printhead can in turn comprise multiple colors so as to provide for full color output as would be readily apparent to those skilled in the art. 
     Turning now to  FIG. 809-FIG .  827  there will now be explained one form of fabrication of a preferred embodiment in order to describe the structure of the nozzle arrangement  3801 . A preferred embodiment can start with a CMOS processed silicon wafer  3850  which can include a standard CMOS layer  3851  of the relevant electrical circuitry etc. The processing steps can then be as follows: 
     1. As illustrated in  FIG. 809  a deep silicon etch is performed so as to form the nozzle cavity  3807  and ink inlet  3808 . A series of pits e.g.  3845  are also etched down to an aluminum portion of the CMOS layer. 
     2. Next, as illustrated in  FIG. 810 , a sacrificial material layer  3852  is deposited and planarized using a standard Chemical Mechanical Planarization (CMP) process before being etched with a nozzle wall mask so as to form cavities for the nozzle wall, plug portion and interconnect portion. A suitable sacrificial material is aluminum which is often utilized in MEMS processes as a sacrificial material. 
     3. Next, as illustrated in  FIG. 811 , a 3 micron layer of low stress glass  3853  is deposited and planarized utilizing CMP. 
     4. Next, as illustrated in  FIG. 812 , the sacrificial material  3852  is etched to a depth of 1.1 micron and the glass  3853  is further etched at least 1.1 micron utilizing a first heater mask. 
     5. Next, as illustrated in  FIG. 813 , the glass is etched e.g.  3855  down to an aluminum layer e.g.  3856  of the CMOS layer. 
     6. Next, as illustrated in  FIG. 814 , a 3 micron layer of 60% copper and 40% nickel alloy is deposited  3857  and planarized utilizing CMP. The copper and nickel alloy hereinafter called “cupronickel” is a material having a high “bend efficiency” as previously described. 
     7. Next, as illustrated in  FIG. 815 , a 3 micron layer  3860  of low stress glass is deposited and etched utilizing a first paddle mask. 
     8. Next, as illustrated in  FIG. 816 , a further 3 micron layer of aluminum e.g.  3861  is deposited and planarized utilizing chemical mechanical planarization. 
     9. Next, as illustrated in  FIG. 817 , a 2 micron layer of low stress glass is deposited and etched  3863  by 1.1 micron utilizing a heater mask for the second heater. 
     10. As illustrated in  FIG. 818 , the glass is etched at  3864  down to the cupronickel layer so as to provide for the upper level heater contact. 
     11. Next, as illustrated in  FIG. 819 , a 3 micron layer of cupronickel alloy is deposited and planarized at  3865  utilizing CMP. 
     12. Next, as illustrated in  FIG. 820 , a 7 micron layer of low stress glass  3866  is deposited. 
     13. Next, as illustrated in  FIG. 821  the glass is etched at  3868  to a depth of 2 micron utilizing a mask for the paddle. 
     14. Next, as illustrated in  FIG. 822 , the glass is etched at  3869  to a depth of 7 micron using a mask for the nozzle walls, portions of the actuator and the post portion. 
     15. Next, as illustrated in  FIG. 823 , a 9 micron layer of sacrificial material is deposited at  3870  and planarized utilizing CMP. 
     16. Next, as illustrated in  FIG. 824 , a 3 micron layer of low stress glass is deposited and etched at  3871  to a depth of 1 micron utilizing a nozzle rim mask. 
     17. Next, as illustrated in  FIG. 825 , the glass is etched down to the sacrificial layer at  3872  utilizing a nozzle mask. 
     18. Next, as illustrated in  FIG. 826 , an ink supply channel  3809  is etched through from the back of the wafer utilizing a silicon deep trench etcher which has near vertical side wall etching properties. A suitable silicon trench etcher is the deep silicon trench etcher available from Silicon Technology Systems of the United Kingdom. The printheads can also be “diced” as a result of this etch. 
     19. Next, as illustrated in  FIG. 827 , the sacrificial layers are etched away utilizing a wet etch so as release the structure of the printhead. 
     The printheads can then be washed and inserted in an ink chamber molding for providing an ink supply to the back of the wafer so to allow ink to be supplied via the ink supply channel. The printhead can then have one edge along its surface TAB bonded to external control lines and preferably a thin anti-corrosion layer of ECR diamond-like carbon deposited over its surfaces so as to provide for anti corrosion capabilities. 
     Turning now to  FIG. 828 , there is illustrated a portion  3880  of a full color printhead which is divided into three series  3881 ,  3882  and  3883  of nozzle arrangements  3801  ( FIG. 807 ). Each series can supply a separate color via a corresponding ink supply channel. Each series is further subdivided into two sub-rows  3886 ,  3887  with the relevant nozzle arrangements of each sub-row being fired simultaneously with one sub-row being fired a predetermined time after a second sub-row such that a line of ink drops is formed on a page. 
     As illustrated in  FIG. 828  the actuators are formed in a curved relationship with respect to a line on which each series of nozzle arrangements  3801  lies, so as to provide for a compact packing of the nozzle arrangements. Further, the block portion  3818  of  FIG. 807  is formed in a wall of an adjacent series with the block portion of the row  3883  being formed in a separate guide rail  3890  provided as an abutment surface for the TAB strip when it is abutted against the guide rail  3890  so as to provide for an accurate registration of the tab strip with respect to the bond pads  3891 ,  3892  which are provided along the length of the printhead so as to provide for low impedance driving of the actuators. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  3850 , Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  3851 . This step is shown in  FIG. 830 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 829  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide down to silicon or aluminum using Mask  1 . This mask defines the pit underneath the paddle, the anti-wicking pits at the actuator entrance to the nozzle chamber, as well as the edges of the print heads chip. 
     3. Etch silicon to a depth of 20 microns using etched oxide as a mask. The sidewall slope of this etch is not critical (60 to 90 degrees is acceptable), so standard trench etchers can be used. This step is shown in  FIG. 831 . 
     4. Deposit 23 microns of sacrificial material  3852  (e.g. polyimide or aluminum). Planarize to a thickness of 3 microns over the chip surface using CMP. 
     5. Etch the sacrificial layer using Mask  2 , which defines the nozzle walls and actuator anchor. This step is shown in  FIG. 832 . 
     6. Deposit 3 microns of PECVD glass  3853  and planarize using CMP. 
     7. Etch the sacrificial material to a depth of 1.1 microns, and glass to a depth of at least 1.1 microns, using Mask  3 . This mask defined the lower heater. This step is shown in  FIG. 833 . 
     8. Etch the glass layer down to aluminum using Mask  4 , defining heater vias. This step is shown in  FIG. 834 . 
     9. Deposit 3 microns of heater material  3857  (e.g. cupronickel [Cu: 60%, Ni: 40%] or TiN). If cupronickel, then deposition can consist of three steps—a thin anti-corrosion layer of, for example, TiN, followed by a seed layer, followed by electroplating of the cupronickel. 
     10. Planarize down to the sacrificial layer using CMP. Steps 7 to 10 form a ‘dual damascene’ process. This step is shown in  FIG. 835 . 
     11. Deposit 3 microns of PECVD glass  3860  and etch using Mask  5 . This mask defines the actuator arm and the second layer of the nozzle chamber wall. This step is shown in  FIG. 836 . 
     12. Deposit 3 microns of sacrificial material  3861  and planarize using CMP. 
     13. Deposit 2 microns of PECVD glass  3863 . 
     14. Etch the glass to a depth of 1.1 microns, using Mask  6 . This mask defined the upper heater. This step is shown in  FIG. 837 . 
     15. Etch the glass layer down to heater material using Mask  7 , defining the upper heater vias  3864 . This step is shown in  FIG. 838 . 
     16. Deposit 3 microns of the same heater material  3865  as step 9. 
     17. Planarize down to the glass layer using CMP. Steps 14 to 17 form a second dual damascene process. This step is shown in  FIG. 839 . 
     18. Deposit 7 microns of PECVD glass  3866 . This step is shown in  FIG. 840 . 
     19. Etch glass to a depth of 2 microns using Mask  8 . This mask defines the paddle, actuator, actuator anchor, as well as the nozzle walls. This step is shown in  FIG. 841 . 
     20. Etch glass to a depth of 7 microns (stopping on sacrificial material in exhaust gasses) using Mask  9 . This mask defines the nozzle walls and actuator anchor. This step is shown in  FIG. 842 . 
     21. Deposit 9 microns of sacrificial material  3870  and planarize down to glass using CMP. This step is shown in  FIG. 843 . 
     22. Deposit 3 microns of PECVD glass  3871 . 
     23. Etch glass to a depth of 1 micron using Mask  10 , which defines the nozzle rims  3802 . This step is shown in  FIG. 844 . 
     24. Etch glass down to the sacrificial layer (3 microns) using Mask  11 , defining the nozzles and the nozzle chamber roof. This step is shown in  FIG. 845 . 
     25. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     26. Back-etch silicon wafer to within approximately 15 microns of the front surface using Mask  8 . This mask defines the ink inlets  3809  which are etched through the wafer. The wafer is also diced by this etch. This etch can be achieved with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems. This step is shown in  FIG. 846 . 
     27. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch This step is shown in  FIG. 847 . 
     28. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     29. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     30. Hydrophobize the front surface of the print heads. 
     31. Fill the completed print heads with ink  3874  and test them. A filled nozzle is shown in  FIG. 848 . 
     IJ39 
     In a preferred embodiment, an inkjet printing system is provided having an ink ejection nozzle arrangement such that a paddle actuator type device is utilized to eject ink from a refillable nozzle chamber. As a result of the construction processes utilized, the paddle is generally of a “cupped” shape. The cup shape provides for the alleviation of a number of the aforementioned problems. The paddle is interconnected to a thermal actuator device which is thermally actuated by means of passing a current through a portion of the thermal actuator, so as to cause the ejection of ink therefrom. Further, the cupped paddle allows for a suitable construction process which does not require the formation of thick surface layers during the process of construction. This means that thermal stresses across a series of devices constructed on a single wafer are minimized. 
     Turning initially to  FIGS. 849-851 , there will now be explained the operational principles of a preferred embodiment In  FIG. 849  there is illustrated an inkjet nozzle arrangement  3901  having a nozzle chamber  3902  which is normally filled with ink from a supply channel  3903  such that a meniscus  3904  forms across the ink ejection aperture of the nozzle arrangement Inside the nozzle arrangement, a cupped paddle actuator  3905  is provided and interconnected to an actuator arm  3906  which, when in a quiescent position, is bent downwards. The lower surface of the actuator arm  3906  includes a heater element  3908  which is constructed of material having a high “bend efficiency”. 
     Preferably, the heater element has a high bend efficiency wherein the bend efficiency is defined as:
 
bend efficiency=Young&#39;s Modulus×(Coefficient of thermal Expansion)/Density×Specific Heat Capacity
 
     A suitable material can be a copper nickel alloy of 60% copper and 40% nickel, hereinafter called (cupronickel). which can be formed below a glass layer so as to bend the glass layer. 
     In its quiescent position, the arm  3906  is bent down by the element  3908 . When it is desired to eject a droplet of ink from the nozzle chamber  3902 , a current is passed through the actuator arm  3908  by means of an interconnection provided by a post  3909 . The heater element  3908  is heated and expands with a high bend efficiency thereby causing the arm  3906  to move upwards as indicated in  FIG. 850 . The upward movement of the actuator arm  3906  causes the cupped paddle  3905  to also move up which results in a general increase in pressure within the nozzle chamber  3902  in the area surrounding the meniscus  3904 . This results in a general outflow of ink and a bulging of the meniscus  3904 . Next, as indicated in  FIG. 851 , the heater element  3908  is turned off which results in the general return of the arm  3906  to its quiescent position which further results in a downward movement of the cupped paddle  3905 . This results in a general sucking back  3911  of the ink within the nozzle chamber  3902 . The forward momentum of the ink surrounding the meniscus and the backward momentum of the ink results in a general necking of the meniscus and the formation of a drop  3912  which proceeds to the surface of the page. Subsequently, the shape of the meniscus  3904  results in a subsequent inflow of ink via the inlet channel  3903  which results in a refilling of the nozzle chamber  3902 . Eventually, the state returns to that indicated by  FIG. 849 . 
     Turning now to  FIG. 852 , there is illustrated a side perspective view partly in section of one form of construction, a single nozzle arrangement  3901  in greater detail. The nozzle arrangement  3901  includes a nozzle chamber  3902  which is normally filled with ink. Inside the nozzle chamber  3902  is a paddle actuator  3905  which divides the nozzle chamber from an ink refill supply channel  3903  which supplies ink from a back surface of a silicon wafer  3914 . 
     Outside of the nozzle chamber  3902  is located an actuator arm  3906  which includes a glass core portion and an external cupronickel portion  3908 . The actuator arm  3906  interconnects with the paddle  3905  by means of a slot  3919  located in one wall of the nozzle chamber  3902 . The slot  3919  is of small dimensions such that surface tension characteristics retain the ink within the nozzle chamber  3902 . Preferably, the external portions of the arrangement  3901  are further treated so as to be strongly hydrophobic. Additionally, a pit  3921  is provided around the slot  3919 . The pit includes a ledge  3922  with the pit and ledge interacting so as to minimize the opportunities for “wicking” along the actuator arm  3906 . Further, to assist of minimizing of wicking, the arm  3906  includes a thinned portion  3924  adjacent to the nozzle chamber  3902  in addition to a right angled wall  3925 . 
     The surface of the paddle actuator  3905  includes a slot  3912 . The slot  3912  aids in allowing for the flow of ink from the back surface of paddle actuator  3905  to a front surface. This is especially the case when initially the arrangement is filled with air and a liquid is injected into the refill channel  3903 . The dimensions of the slot are such that, during operation of the paddle for ejecting drops, minimal flow of fluid occurs through the slot  3912 . 
     The paddle actuator  3905  is housed within the nozzle chamber and is actuated so as to eject ink from the nozzle  3927  which in turn includes a rim  3928 . The rim  3928  assists in minimizing wicking across the top of the nozzle chamber  3902 . 
     The cupronickel element  3908  is interconnected through a post portion  3909  to a lower CMOS layer  3915  which provides for the electrical control of the actuator element 
     Each nozzle arrangement  3901 , can be constructed as part of an array of nozzles on a silicon wafer device and can be constructed from the utilizing semiconductor processing techniques in addition to micro machining and micro fabrication process technology (MEMS) and a full familiarity with these technologies is hereinafter assumed. 
     Turning initially to  FIG. 854   a  and  854   b , in  FIG. 854   b  there is shown an initial processing step which utilizes a mask having a region as specified in  FIG. 854   a . The initial starting material is preferably a silicon wafer  3914  having a standard 0.25 micron CMOS layer  3915  which includes drive electronics (not shown), the structure of the drive on electronics being readily apparent to those skilled in the art of CMOS integrated circuit designs. 
     The first step in the construction of a single nozzle is to pattern and etch a pit  3928  to a depth of 13 microns using the mask pattern having regions specified  3929  as illustrated in  FIG. 854   a.    
     Next, as illustrated in  FIG. 855   b , a 3 micron layer of the sacrificial material  3930  is deposited The sacrificial material can comprise aluminum. The sacrificial material  3930  is then etched utilizing a mask pattern having portions  3931  and  3932  as indicated at  FIG. 855   a.    
     Next, as shown in  FIG. 856   b  a very thin 0.1 micron layer of a corrosion barrier material  3934  (for example, silicon nitride) is deposited and subsequently etched so as to form the heater element  3935 . The etch utilizes a third mask having mask regions specified  3936  and  3937  in  FIG. 856   a.    
     Next, as shown intended in  FIG. 857   b , a 1.1 micron layer of heater material  3939  which can comprise a 60% copper 40% nickel alloy is deposited utilizing a mask having a resultant mask region  3940  as illustrated in  FIG. 857   a.    
     Next a 0.1 micron corrosion layer is deposited over the surface. The corrosion barrier can again comprise silicon nitride. 
     Next, as illustrated in  FIG. 858   b , a 3.4 micron layer of glass  3942  is deposited. The glass and nitride can then be etched utilizing a mask as specified  3943  in  FIG. 858   a . The glass layer  3942  includes, as part of the deposition process, a portion  3944  which is a result of the deposition process following the lower surface profile. 
     Next, a 6 μm layer of sacrificial material  3945  such as aluminum is deposited as indicated in  FIG. 859   b . This layer is planarized to approximately 4 micron minimum thickness utilizing a Chemical Mechanical Planarization (CMP) process. Next, the sacrificial material layer is etched utilizing a mask having regions  3948 ,  3949  as illustrated in  FIG. 859   a  so as to form portions of the nozzle wall and post. 
     Next, as illustrated in  FIG. 860   b , a 3 micron layer of glass  3950  is deposited. The 3 micron layer is patterned and etched to a depth of 1 micron using a mask having a region specified  3951  as illustrated in  FIG. 860   a  so as to form a nozzle rim. 
     Next, as illustrated in  FIG. 861   b  the glass layer is etched utilizing a further mask  3952  as illustrated in  FIG. 861   a  which leaves glass portions e.g.  3953  to form the nozzle chamber wall and post portion  3954 . 
     Next, as illustrated in  FIG. 862   b  the backside of the wafer is patterned and etched so as to form an ink supply channel  3903 . The mask utilized can have regions  3956  as specified in  FIG. 862   a . The etch through the backside of the wafer can preferably utilize a high quality deep anisotropic etching system such as that available from Silicon Technology Systems of the United Kingdom. Preferably, the etching process also results in the dicing of the wafer into its separate printheads at the same time. 
     Next, as illustrated in  FIG. 863 , the sacrificial material can be etched away so as to release the actuator structure. Upon release, the actuator  3906  bends downwards due to its release from thermal stresses built up during deposition. The printhead can then be cleaned and mounted in a molded ink supply system for the supply of ink to the back surface of the wafer. A TAB film for supplying electric control to an edge of the printhead can then be bonded utilizing normal TAB bonding techniques. The surface area can then be hydrophobically treated and finally the ink supply channel and nozzle chamber filled with ink for testing. 
     Hence, as illustrated in  FIG. 864 , a pagewidth printhead having a repetitive structure  3960  can be constructed for full color printing.  FIG. 864  shows a portion of the final printhead structure and includes three separate groupings  3961 - 3963  with one grouping for each color and each grouping e.g.  3963  in turn consisting of two separate rows of inkjet nozzles  3965 ,  3966  which are spaced apart in an interleaved pattern. The nozzle  3965 ,  3966  are fired at predetermined times so as to form an output image as would be readily understood by those skilled in the art of construction of inkjet printhead. Each nozzle e.g.  3968  includes its own actuator arm  3969  which, in order to form an extremely compact arrangement, is preferably formed so as to be generally bent with respect to the line perpendicular to the row of nozzles. Preferably, a three color arrangement is provided which has one of the groups  3961 - 3963  dedicated to cyan, magenta and another yellow color printing. Obviously, four color printing arrangements can be constructed if required. 
     Preferably, at one side a series of bond pads e.g.  3971  are formed along the side for the insertion of a tape automated bonding (TAB) strip which can be aligned by means of alignment rail e.g.  3972  which is constructed along one edge of the printhead specifically for this purpose. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  3914 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  3915 . This step is shown in  FIG. 866 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 865  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide down to silicon or aluminum using Mask  1 . This mask defines the pit underneath the paddle, as well as the edges of the printheads chip. 
     3. Etch silicon to a depth of 8 microns  3980  using etched oxide as a mask The sidewall slope of this etch is not critical (60 to 90 degrees is acceptable), so standard trench etchers can be used. This step is shown in  FIG. 867 . 
     4. Deposit 3 microns of sacrificial material  3981  (e.g. aluminum or polyimide) 
     5. Etch the sacrificial layer using Mask  3 , defining heater vias  3982  and nozzle chamber walls  3983 . This step is shown in  FIG. 868 . 
     6. Deposit 0.2 microns of heater material  3984 , e.g. TiN. 
     7. Etch the heater material using Mask  3 , defining the heater shape. This step is shown in  FIG. 869 . 
     8. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     9. Deposit 3 microns of PECVD glass  3985 . 
     10. Etch glass layer using Mask  4 . This mask defines the nozzle chamber wall, the paddle, and the actuator arm. This step is shown in  FIG. 870 . 
     11. Deposit 6 microns of sacrificial material  3986 . 
     12. Etch the sacrificial material using Mask  5 . This mask defines the nozzle chamber wall. This step is shown in  FIG. 871 . 
     13. Deposit 3 microns of PECVD glass  3987 . 
     14. Etch to a depth of (approx.) 1 micron using Mask  6 . This mask defines the nozzle rim  3928 . This step is shown in  FIG. 872 . 
     15. Etch down to the sacrificial layer using Mask  7 . This mask defines the roof of the nozzle chamber, and the nozzle  3927  itself. This step is shown in  FIG. 873 . 
     16. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  8 . This mask defines the ink inlets  3903  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 874 . 
     17. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch This step is shown in  FIG. 875 . 
     18. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     19. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     20. Hydrophobize the front surface of the printheads. 
     21. Fill the completed printheads with ink  3988  and test them. A filled nozzle is shown in  FIG. 876 . 
     IJ40 
     In a preferred embodiment, there is provided a nozzle arrangement having a nozzle chamber containing ink and a thermal actuator connected to a paddle positioned within the chamber. The thermal actuator device is actuated so as to eject ink from the nozzle chamber. A preferred embodiment includes a particular thermal actuator which includes a series of tapered portions for providing conductive heating of a conductive trace. The actuator is connected to the paddle via an arm received through a slotted wall of the nozzle chamber. The actuator arm has a mating shape so as to mate substantially with the surfaces of the slot in the nozzle chamber wall. 
     Turning initially to  FIG. 877-879 , there is provided schematic illustrations of the basic operation of a nozzle arrangement of the invention. A nozzle chamber  4001  is provided filled with ink  4002  by means of an ink inlet channel  4003  which can be etched through a wafer substrate on which the nozzle chamber  4001  rests. The nozzle chamber  4001  further includes an ink ejection port  4004  around which an ink meniscus  4005  forms. 
     Inside the nozzle chamber  4001  is a paddle type device  4007  which is interconnected to an actuator  4008  through a slot in the wall of the nozzle chamber  4001 . The actuator  4008  includes a heater means e.g.  4009  located adjacent to an end portion of a post  4010 . The post  4010  is fixed to a substrate. 
     When it is desired to eject a drop from the nozzle chamber  4001 , as illustrated in  FIG. 878 , the heater means  4009  is heated so as to undergo thermal expansion. Preferably, the heater means  4009  itself or the other portions of the actuator  4008  are built from materials having a high bend efficiency where the bend efficiency is defined as
 
bend efficiency=Young&#39;s Modulus×(Coefficient of thermal Expansion)/Density×Specific Heat Capacity
 
     A suitable material for the heater elements is a copper nickel alloy which can be formed so as to bend a glass material. 
     The heater means  4009  is ideally located adjacent the end portion of the post  4010  such that the effects of activation are magnified at the paddle end  4007  such that small thermal expansions near the post  4010  result in large movements of the paddle end. 
     The heater means  4009  and consequential paddle movement causes a general increase in pressure around the ink meniscus  4005  which expands, as illustrated in  FIG. 878 , in a rapid manner. The heater current is pulsed and ink is ejected out of the port  4004  in addition to flowing in from the ink channel  4003 . 
     Subsequently, the paddle  4007  is deactivated to again return to its quiescent position. The deactivation causes a general reflow of the ink into the nozzle chamber. The forward momentum of the ink outside the nozzle rim and the corresponding backflow results in a general necking and breaking off of the drop  4012  which proceeds to the print media. The collapsed meniscus  4005  results in a general sucking of ink into the nozzle chamber  4002  via the ink flow channel  4003 . In time, the nozzle chamber  4001  is refilled such that the position in  FIG. 877  is again reached and the nozzle chamber is subsequently ready for the ejection of another drop of ink. 
       FIG. 880  illustrates a side perspective view of the nozzle arrangement  FIG. 881  illustrates sectional view through an array of nozzle arrangement of  FIG. 880 . In these figures, the numbering of elements previously introduced has been retained. 
     Firstly, the actuator  4008  includes a series of tapered actuator units e.g.  4015  which comprise an upper glass portion (amorphous silicon dioxide)  4016  formed on top of a titanium nitride layer  4017 . Alternatively a copper nickel alloy layer (hereinafter called cupronickel) can be utilized which will have a higher bend efficiency where bend efficiency is defined as:
 
bend efficiency=Young&#39;s Modulus×(Coefficient of thermal Expansion)/Density×Specific Heat Capacity
 
     The titanium nitride layer  4017  is in a tapered form and, as such, resistive heating takes place near an end portion of the post  4010 . Adjacent titanium nitride/glass portions  4015  are interconnected at a block portion  4019  which also provides a mechanical structural support for the actuator  4008 . 
     The heater means  4009  ideally includes a plurality of the tapered actuator unit  4015  which are elongate and spaced apart such that, upon heating, the bending force exhibited along the axis of the actuator  4008  is maximized. Slots are defined between adjacent tapered units  4015  and allow for slight differential operation of each actuator  4008  with respect to adjacent actuators  4008 . 
     The block portion  4019  is interconnected to an arm  4020 . The arm  4020  is in turn connected to the paddle  4007  inside the nozzle chamber  4001  by means of a slot e.g.  4022  formed in the side of the nozzle chamber  4001 . The slot  4022  is designed generally to mate with the surfaces of the arm  4020  so as to minimize opportunities for the outflow of ink around the arm  4020 . The ink is held generally within the nozzle chamber  4001  via surface tension effects around the slot  4022 . 
     When it is desired to actuate the arm  4020 , a conductive current is passed through the titanium nitride layer  4017  via vias within the block portion  4019  connecting to a lower CMOS layer  4006  which provides the necessary power and control circuitry for the nozzle arrangement. The conductive current results in heating of the nitride layer  4017  adjacent to the post  4010  which results in a general upward bending of the arm  4020  and consequential ejection of ink out of the nozzle  4004 . The ejected drop is printed on a page in the usual manner for an inkjet printer as previously described. 
     An array of nozzle arrangements can be formed so as to create a single printhead. For example, in  FIG. 881  there is illustrated a partly sectioned various array view which comprises multiple ink ejection nozzle arrangements of  FIG. 880  laid out in interleaved lines so as to form a printhead array. Of course, different types of arrays can be formulated including full color arrays etc. 
     Fabrication of the ink jet nozzle arrangement is indicated in  FIGS. 883 to 892 . A preferred embodiment achieves a particular balance between utilization of the standard semi-conductor processing material such as titanium nitride and glass in a MEMS process. Obviously the skilled person may make other choices of materials and design features where the economics are justified. For example, a copper nickel alloy of 50% copper and 50% nickel may be more advantageously deployed as the conductive heating compound as it is likely to have higher levels of bend efficiency. Also, other design structures may be employed where it is not necessary to provide for such a simple form of manufacture. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  4031 , complete a 0.5 micron, one poly, 2 metal CMOS process to form layer  4006 . This step is shown in  FIG. 883 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 882  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide layer  4006  down to silicon or aluminum  4032  using Mask  1 . This mask defines the nozzle chamber, the surface anti-wicking notch, and the heater contacts. This step is shown in  FIG. 884 . 
     3. Deposit 1 micron of sacrificial material  4033  (e.g. aluminum or photosensitive polyimide) 
     4. Etch (if aluminum) or develop (if photosensitive polyimide) the sacrificial layer  4033  using Mask  2 . This mask defines the nozzle chamber walls and the actuator anchor point. This step is shown in  FIG. 885 . 
     5. Deposit 0.2 micron of heater material  4034 , e.g. TIN. 
     6. Deposit 3.4 microns of PECVD glass  4035 . 
     7. Etch both glass  4035  and heater  4034  layers together, using Mask  3 . This mask defines the actuator, paddle, and nozzle chamber walls. This step is shown in  FIG. 886 . 
     8. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     9. Deposit 10 microns of sacrificial material  4036 . 
     10. Etch or develop sacrificial material  4036  using Mask  4 . This mask defines the nozzle chamber wall. This step is shown in  FIG. 887 . 
     11. Deposit 3 microns of PECVD glass  4037 . 
     12. Etch to a depth of (approx.) 1 micron using Mask  5 . This mask defines the nozzle rim  4038 . This step is shown in  FIG. 888 . 
     13. Etch down to the sacrificial layer  4036  using Mask  6 . This mask defines the roof of the nozzle chamber, and the nozzle  4004  itself. This step is shown in  FIG. 889 . 
     14. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  7 . This mask defines the ink inlets  4003  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 890 . 
     15. Etch the sacrificial material  4033 ,  4036 . The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in  FIG. 891 . 
     16. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets  4003  at the back of the wafer. 
     17. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     18. Hydrophobize the front surface of the print heads. 
     19. Fill the completed print heads with ink  4039  and test them. A filled nozzle is shown in  FIG. 892 . 
     IJ41 
     In a preferred embodiment, there is provided a nozzle chamber having ink within it and a thermal actuator device interconnected to a paddle, the thermal actuator device being actuated so as to eject ink from the nozzle chamber. A preferred embodiment includes a particular thermal actuator structure which includes a tapered heater structure arm for providing positional heating of a conductive heater layer row. The actuator arm is connected to the paddle through a slotted wall in the nozzle chamber. The actuator arm has a mating shape so as to mate substantially with the surfaces of the slot in the nozzle chamber wall. 
     Turning initially to  FIGS. 893-895 , there is provided schematic illustrations of the basic operation of the device. A nozzle chamber  4101  is provided filled with ink  4102  by means of an ink inlet channel  4103  which can be etched through a wafer substrate on which the nozzle chamber  4101  rests. The nozzle chamber  4101  includes an ink ejection nozzle or aperture  4104  around which an ink meniscus forms. 
     Inside the nozzle chamber  4101  is a paddle type device  4107  which is connected to an actuator arm  4108  through a slot in the wall of the nozzle chamber  4101 . The actuator arm  4108  includes a heater means  4109  located adjacent to a post end portion  4110  of the actuator arm. The post  4110  is fixed to a substrate. 
     When it is desired to eject a drop from the nozzle chamber, as illustrated in  FIG. 894 , the heater means  4109  is heated so as to undergo thermal expansion. Preferably, the heater means itself or the other portions of the actuator arm  4108  are built from materials having a high bend efficiency where the bend efficiency is defined as
 
bend efficiency=Young&#39;s Modulus×(Coefficient of thermal Expansion)/Density×Specific Heat Capacity
 
     A suitable material for the heater elements is a copper nickel alloy which can be formed so as to bend a glass material. 
     The heater means is ideally located adjacent the post end portion  4110  such that the effects of activation are magnified at the paddle end  4107  such that small thermal expansions near post  4110  result in large movements of the paddle end. The heating  4109  causes a general increase in pressure around the ink meniscus  4105  which expands, as illustrated in  FIG. 894 , in a rapid manner. The heater current is pulsed and ink is ejected out of the nozzle  4104  in addition to flowing in from the ink channel  4103 . Subsequently, the paddle  4107  is deactivated to again return to its quiescent position. The deactivation causes a general reflow of the ink into the nozzle chamber. The forward momentum of the ink outside the nozzle rim and the corresponding backflow results in a general necking and breaking off of a drop  4112  which proceeds to the print media. The collapsed meniscus  4105  results in a general sucking of ink into the nozzle chamber  4101  via the in flow channel  4103 . In time, the nozzle chamber is refilled such that the position in  FIG. 893  is again reached and the nozzle chamber is subsequently ready for the ejection of another drop of ink. 
     Turning now to  FIG. 896 , there is illustrated a single nozzle arrangement  4120  of a preferred embodiment. The arrangement includes an actuator arm  4121  which includes a bottom layer  4122  which is constructed from a conductive material such as a copper nickel alloy (hereinafter called cupronickel) or titanium nitride (TiN). The layer  4122 , as will become more apparent hereinafter includes a tapered end portion near the end post  4124 . The tapering of the layer  4122  near this end means that any conductive resistive heating occurs near the post portion  4124 . 
     The layer  4122  is connected to the lower CMOS layers  4126  which are formed in the standard manner on a silicon substrate surface  4127 . The actuator arm  4121  is connected to an ejection paddle which is located within a nozzle chamber  4128 . The nozzle chamber includes an ink ejection nozzle  4129  from which ink is ejected and includes a convoluted slot arrangement  4130  which is constructed such that the actuator arm  4121  is able to move up and down while causing minimal pressure fluctuations in the area of the nozzle chamber  4128  around the slot  4130 . 
       FIG. 897  illustrates a sectional view through a single nozzle.  FIG. 897  illustrates more clearly the internal structure of the nozzle chamber which includes the paddle  4132  attached to the actuator arm  4121  having face  4133 . Importantly, the actuator arm  4121  includes, as noted previously, a bottom conductive layer  4122 . Additionally, a top layer  4125  is also provided. 
     The utilization of a second layer  4125  of the same material as the first layer  4122  allows for more accurate control of the actuator position as will be described with reference to  FIGS. 898 and 899 . In  FIG. 898 , there is illustrated the example where a high Young&#39;s modulus material  4140  is deposited utilizing standard semiconductor deposition techniques and on top of which is further deposited a second layer  4141  having a much lower Young&#39;s modulus. Unfortunately, the deposition is likely to occur at a high temperature. Upon cooling, the two layers are likely to have different coefficients of thermal expansion and different Young&#39;s modulus. Hence, in ambient room temperature, the thermal stresses are likely to cause bending of the two layers of material as shown at  4142 . 
     By utilizing a second deposition of the material having a high Young&#39;s Modulus, the situation in  FIG. 899  is likely to result wherein the material  4141  is sandwiched between the two layers  4140 . Upon cooling, the two layers  4140  are kept in tension with one another so as to result in a more planar structure  4145  regardless of the operating temperature. This principle is utilized in the deposition of the two layers  4122 ,  4125  of  FIGS. 896-897 . 
     Turning again to  FIGS. 896 and 897 , one important attribute of a preferred embodiments includes the slotted arrangement  4130 . The slotted arrangement results in the actuator arm  4121  moving up and down thereby causing the paddle  4132  to also move up and down resulting in the ejection of ink. The slotted arrangement  4130  results in minimum ink outflow through the actuator arm connection and also results in minimal pressure increases in this area. The face  4133  of the actuator arm is extended out so as to form an extended interconnect with the paddle surface thereby providing for better attachment. The face  4133  is connected to a block portion  4136  which is provided to provide a high degree of rigidity. The actuator arm  4121  and the wall of the nozzle chamber  4128  have a general corrugated nature so as to reduce any flow of ink through the slot  4130 . The exterior surface of the nozzle chamber adjacent the block portion  4136  has a rim e.g.  4138  so to minimize wicking of ink outside of the nozzle chamber. A pit  4137  is also provided for this purpose. The pit  4137  is formed in the lower CMOS layers  4126 . An ink supply channel  4139  is provided by means of back etching through the wafer to the back surface of the nozzle. 
     Turning to  FIGS. 900-907  there will now be described the manufacturing steps utilized on the construction of a single nozzle in accordance with a preferred embodiment. 
     The manufacturing uses standard micro-electro mechanical techniques. 
     1. A preferred embodiment starts with a double sided polished wafer complete with, say, a 0.5 micron 1 poly 2 metal CMOS process providing for all the electrical interconnects necessary to drive the inkjet nozzle. 
     2. As shown in  FIG. 900 , the CMOS wafer  4126  is etched at  4150  down to the silicon layer  4127 . The etching includes etching down to an aluminum CMOS layer  4151 ,  4152 . 
     3. Next, as illustrated in  FIG. 901 , a 1 micron layer of sacrificial material  4155  is deposited. The sacrificial material can be aluminum or photosensitive polyimide. 
     4. The sacrificial material is etched in the case of aluminum or exposed and developed in the case of polyimide in the area of the nozzle rim  4156  and including a dished paddle area  4157 . 
     Next, a 1 micron layer of heater material  4160  (cupronickel or TiN) is deposited. 
     A 3.4 micron layer of PECVD glass  4161  is then deposited. 
     7. A second layer  4162  equivalent to the first layer  4160  is then deposited. 
     8. All three layers  4160 - 4162  are then etched utilizing the same mask. The utilization of a single mask substantially reduces the complexity in the processing steps involved in creation of the actuator paddle structure and the resulting structure is as illustrated in  FIG. 902 . Importantly, a break  4163  is provided so as to ensure electrical isolation of the heater portion from the paddle portion. 
     9. Next, as illustrated in  FIG. 903 , a 10 micron layer of sacrificial material  4170  is deposited. 
     10. The deposited layer is etched (or just developed if polyimide) utilizing a fourth mask which includes nozzle rim etchant holes  4171 , block portion holes  4172  and post portion  4173 . 
     11. Next a 10 micron layer of PECVD glass is deposited so as to form the nozzle rim  4171 , arm portions  4172  and post portions  4173 . 
     12. The glass layer is then planarized utilizing chemical mechanical planarization (CMP) with the resulting structure as illustrated in  FIG. 903 . 
     13. Next, a 3 micron layer of PECVD glass is deposited. 
     14. The deposited glass is then etched as shown in  FIG. 904 , to a depth of approximately 1 micron so as to form nozzle rim portion  4181  and actuator interconnect portion  4182 . 
     15. Next, as illustrated in  FIG. 905 , the glass layer is etched utilizing a 6th mask so as to form final nozzle rim portion  4181  and actuator guide portion  4182 . 
     16. Next, as illustrated in  FIG. 906 , the ink supply channel is back etched  4185  from the back of the wafer utilizing a 7th mask. The etch can be performed utilizing a high precision deep silicon trench etcher such as the STS Advanced Silicon Etcher (ASE). This step can also be utilized to nearly completely dice the wafer. 
     17. Next, as illustrated in  FIG. 907  the sacrificial material can be stripped or dissolved to also complete dicing of the wafer in accordance with requirements. 
     18. Next, the printheads can be individually mounted on attached molded plastic ink channels to supply ink to the ink supply channels. 
     19. The electrical control circuitry and power supply can then be bonded to an etch of the printhead with a TAB film. 
     20. Generally, if necessary, the surface of the printhead is then hydrophobized so as to ensure minimal wicking of the ink along external surfaces. Subsequent testing can determine operational characteristics. 
     Importantly, as shown in the plan view of  FIG. 908 , the heater element has a tapered portion adjacent the post  4173  so as to ensure maximum heating occurs near the post. 
     Of course, different forms of inkjet printhead structures can be formed. For example, there is illustrated in  FIG. 909 , a portion of a single color printhead having two spaced apart rows  4190 ,  4191 , with the two rows being interleaved so as to provide for a complete line of ink to be ejected in two stages. Preferably, a guide rail  4192  is provided for proper alignment of a TAB film with bond pads  4193 . A second protective barrier  4194  can also preferably be provided. Preferably, as will become more apparent with reference to the description of  FIG. 910  adjacent actuator arms are interleaved and reversed. 
     Turning now to  FIG. 910 , there is illustrated a full color printhead arrangement which includes three series of inkjet nozzles  4195 ,  4196 ,  4197  one each devoted to a separate color. Again, guide rails  4198 ,  4199  are provided in addition to bond pads, e.g.  4174 . In  FIG. 910 , there is illustrated a general plan of the layout of a portion of a full color printhead which clearly illustrates the interleaved nature of the actuator arms. 
     One alternative form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  4127 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process to form layer  4126 . Relevant features of the wafer at this step are shown in  FIG. 912 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 911  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch oxide down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber, the surface anti-wicking notch  4137 , and the heater contacts  4175 . This step is shown in  FIG. 913 . 
     3. Deposit 1 micron of sacrificial material  4155  (e.g. aluminum or photosensitive polyimide) 
     4. Etch (if aluminum) or develop (if photosensitive polyimide) the sacrificial layer using Mask  2 . This mask defines the nozzle chamber walls  4176  and the actuator anchor point. This step is shown in  FIG. 914 . 
     5. Deposit 1 micron of heater material  4160  (e.g. cupronickel or TiN). If cupronickel, then deposition can consist of three steps—a thin anti-corrosion layer of, for example, TiN, followed by a seed layer, followed by electroplating of the 1 micron of cupronickel. 
     6. Deposit 3.4 microns of PECVD glass  4161 . 
     7. Deposit a layer  4162  identical to step 5. 
     8. Etch both layers of heater material, and glass layer, using Mask  3 . This mask defines the actuator, paddle, and nozzle chamber walls. This step is shown in  FIG. 915 . 
     9. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     10. Deposit 10 microns of sacrificial material  4170 . 
     11. Etch or develop sacrificial material using Mask  4 . This mask defines the nozzle chamber wall  4176 . This step is shown in  FIG. 916 . 
     12. Deposit 3 microns of PECVD glass  4177 . 
     13. Etch to a depth of (approx.) 1 micron using Mask  5 . This mask defines the nozzle rim  4181 . This step is shown in  FIG. 917 . 
     14. Etch down to the sacrificial layer using Mask  6 . This mask defines the roof  4178  of the nozzle chamber, and the nozzle itself. This step is shown in  FIG. 918 . 
     15. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  7 . This mask defines the ink inlets  4139  which are etched through the wafer. The wafer is also diced by this etch This step is shown in  FIG. 919 . 
     16. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch This step is shown in  FIG. 920 . 
     17. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     18. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     19. Hydrophobize the front surface of the printheads. 
     20. Fill the completed printheads with ink  4179  and test them. A filled nozzle is shown in  FIG. 921 . 
     IJ42 
     In a preferred embodiment, ink is ejected out of a nozzle chamber via an ink ejection port as the result of the utilization of a series of radially positioned thermal actuator devices that are arranged around the ink ejection port and are activated so as to pressurize the ink within the nozzle chamber thereby causing ink ejection. 
     Turning now to  FIGS. 922 ,  923  and  924 , there is illustrated the basic operational principles of a preferred embodiment.  FIG. 922  illustrates a single nozzle arrangement  4201  in a quiescent state. The arrangement  4201  includes a nozzle chamber  4202  which is normally filled with ink to form a meniscus  4203  in an ink ejection port  4204 . The nozzle chamber  4202  is formed within a wafer  4205 . The nozzle chamber  4202  is in fluid communication with an ink supply channel  4206  which is etched through the wafer  4205  using a highly isotropic plasma etching system. A suitable etcher is the Advance Silicon Etch (ASE) system available from Surface Technology Systems of the United Kingdom. 
     The nozzle arrangement  4201  includes a series of radially positioned thermoactuator devices  4208 ,  4209  about the ink ejection port  4204 . These devices comprise a series of polytetrafluoroethylene (PTFE) actuators having an internal serpentine copper core, which is positioned so that upon heating of the copper core, the subsequent expansion of the surrounding Teflon results in a generally inward movement of radically outer edges of the actuators  4208 ,  4209 . Hence, when it is desired to eject ink from the ink ejection nozzle  4204 , a current is passed through the actuators  4208 ,  4209  which results in the bending as illustrated in  FIG. 923 . The bending movement of actuators  4208 ,  4209  results in a substantial increase in pressure within the nozzle chamber  4202 . The rapid increase in pressure in nozzle chamber  4202 , in turn results in a rapid expansion of the meniscus  4203  as illustrated in  FIG. 923 . 
     The actuators  4208 ,  4209  are briefly activated only and subsequently deactivated so that the actuators  4208 ,  4209  rapidly return to their original positions as shown in  FIG. 924 . This results in a general inflow of ink and a necking and breaking of the meniscus  4203  resulting in the ejection of a drop  4212 . The necking and breaking of the meniscus  4203  is a consequence of a forward momentum of the ink of the drop  4212  and a negative pressure created as a result of the return of the actuators  4208 ,  4209  to their original positions. The return of the actuators  4208 ,  4209  also results in a general inflow of ink in the direction of an arrow so from the supply channel  4206 . Surface tension effects results in a return of the nozzle arrangement  4201  to the quiescent position as illustrated in  FIG. 922 . 
       FIGS. 925(   a ) and  925 ( b ) illustrate a principle of operation of the thermal actuators  4208 ,  4209 . Each thermal  4208 ,  4209  actuator is preferably constructed from a material  4214  having a high coefficient of thermal expansion. Embedded within the material  4214  is a series of heater elements  4215  which can be a series of conductive elements designed to carry a current. The conductive elements  4215  are heated by passing a current through the elements  4215  with the heating resulting in a general increase in temperature in the area around the heating elements  4215 . The increase in temperature causes a corresponding expansion of the PTFE which has a high coefficient of thermal expansion Hence, as illustrated in  FIG. 925(   b ), the PTFE is bent generally in a inward direction. 
     Turning now to  FIG. 926 , there is illustrated a side perspective view of one nozzle arrangement constructed in accordance with the principles previously outlined. The nozzle chamber  4202  is formed by an isotropic surface etch of the wafer  4205 . The wafer  4205  includes a CMOS layer  4221  including all the required power and drive circuits. Further, the actuators  4208 ,  4209  are fabricated as a series of leaf or petal type actuators each having an internal copper or aluminum core  4217  which winds in a serpentine nature to provide for substantially unhindered expansion of the actuator device. The operation of the actuators  4208 ,  4209  is as described earlier with reference to  FIG. 925(   a ) and  FIG. 925(   b ) such that, upon activation, the petals  4208  bend inwardly as previously described. The ink supply channel  4206  is created with a deep silicon back edge of the wafers utilizing a plasma etcher or the like. The copper or aluminum coil  4217  defines a complete circuit A central arm  4218  which includes both metal and PTFE portions provides main structural support for the actuators  4208 ,  4209  in addition to providing a current trace for the conductive elements. 
     Steps of the manufacture of the nozzle arrangement  4201  are described with reference to  FIG. 927  to  FIG. 934 . The nozzle arrangement  4201  is preferably constructed utilizing microelectromechanical (MEMS) techniques and can include the following construction techniques: 
     As shown initially in  FIG. 927 , the initial processing starting material is a standard semi-conductor wafer  4220  having a complete CMOS level  4221  to the first level metal. The first level metal includes portions  4222  which are utilized for providing power to the thermal actuators  4208 ,  4209  ( FIG. 926 ). 
     The first step, as illustrated in  FIG. 928 , is to etch a nozzle region down to the silicon wafer  4220  utilizing an appropriate mask. 
     Next, as illustrated in  FIG. 929 , a 2 micron layer of polytetrafluoroethylene (PTFE)  4223  is deposited and etched to define vias  4224  for interconnecting multiple levels. 
     Next, as illustrated in  FIG. 930 , the second level metal layer is deposited, masked and etched to form a heater structure  4225 . The heater structure  4225  is connected at  4226  with a lower aluminum layer. 
     Next, as illustrated in  FIG. 931 , a further 2 micron layer of PTFE  4223  is deposited and etched to a depth of micron utilizing a nozzle rim mask so as to form a nozzle rim  4228  in addition to ink flow guide rails  4229  which inhibit wicking along the surface of the PTFE layer. The guide rails  4229  thin slots. Thus, surface tension effects result in minimal outflow of ink during operation from the slots. 
     Next, as illustrated in  FIG. 932 , the PTFE is etched utilizing a nozzle and actuator mask to define an ejection nozzle port  4230  and slots  4231  and  4232 . 
     Next, as illustrated in  FIG. 933 , the wafer is crystallographically etched on a &lt;111&gt; plane utilizing a standard crystallographic etchant such as KOH. The etching forms a chamber  4233 , directly below the ink ejection port  4230 . 
     Next, turning to  FIG. 934 , the ink supply channel  4206  is etched from a back of the wafer utilizing a highly anisotropic etcher such as the STS etcher from Silicon Technology Systems of the United Kingdom. An array  4236  of ink jet nozzles can be formed simultaneously with a portion of the array  4236  being illustrated in  FIG. 935 . A portion of the printhead is formed simultaneously and diced by the STS etching process. The array  4236  shown provides for four column printing with each separate column attached to a different color ink supply channel which is supplied from the back of the wafer. Bond pads  4237  provide for electrical control of the ejection mechanism. 
     In this manner, large pagewidth printheads can be formulated to provide for a drop on demand ink ejection mechanism. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed along the following steps: 
     1. Using a double sided polished wafer  4220 , complete a 0.5 micron, one poly, 2 metal CMOS process to form layer  4221 . This step is shown in  FIG. 937 . For clarity; these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 936  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch the CMOS oxide layers down to silicon or second level metal using Mask  1 . This mask defines the nozzle cavity and the edge of the chips. This step is shown in  FIG. 937 . 
     3. Deposit a thin layer (not shown) of a hydrophilic polymer, and treat the surface of this polymer for PTFE adherence. 
     4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE)  4260 . 
     5. Etch the PTFE and CMOS oxide layers to second level metal using Mask  2 . This mask defines the contact vias  4224  for the heater electrodes. This step is shown in  FIG. 938 . 
     6. Deposit and pattern 0.5 microns of gold  4261  using a lift-off process using Mask  3 . This mask defines the heater pattern. This step is shown in  FIG. 939 . 
     7. Deposit 1.5 microns of PTFE  4262 . 
     8. Etch 1 micron of PTFE using Mask  4 . This mask defines the nozzle rim  4228  and the ink flow guide rails  4229  at the edge of the nozzle chamber. This step is shown in  FIG. 940 . 
     9. Etch both layers of PTFE and the thin hydrophilic layer down to silicon using Mask  5 . This mask defines a gap  4264  at the edges of the actuators  4208 ,  4209  ( FIG. 926 ), and the edge of the chips. It also forms the mask for the subsequent crystallographic etch. This step is shown in  FIG. 941 . 
     10. Crystallographically etch the exposed silicon using KOH. This etch stops on &lt;111&gt; crystallographic planes  4265 , forming an inverted square pyramid with sidewall angles of 54. 74 degrees. This step is shown in FIG.  942 . 
     11. Back-etch through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  6 . This mask defines the ink supply channel  4206  which are etched through the wafer  4220 . The wafer  4220  is also diced by this etch. This step is shown in  FIG. 943 . 
     12. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     13. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     14. Fill the completed printheads with ink  4266  and test them. A filled nozzle is shown in  FIG. 944 . 
     IJ43 
     In a preferred embodiment, ink is ejected out of a nozzle chamber via an ink ejection port using a series of radially positioned thermal actuator devices that are arranged about the ink ejection port and are activated to pressurize the ink within the nozzle chamber thereby causing the ejection of ink through the ejection port. 
     Turning now to  FIGS. 945 ,  946  and  947 , there is illustrated the basic operational principles of a preferred embodiment  FIG. 945  illustrates a single nozzle arrangement  4301  in its quiescent state. The arrangement  4301  includes a nozzle chamber  4302  which is normally filled with ink so as to form a meniscus  4303  in an ink ejection port  4304 . The nozzle chamber  4302  is formed within a wafer  4305 . The nozzle chamber  4302  is supplied with ink via an ink supply channel  4306  which is etched through the wafer  4305  with a highly isotropic plasma etching system. A suitable etcher can be the Advance Silicon Etch (ASE) system available from Surface Technology Systems of the United Kingdom. 
     A top of the nozzle arrangement  4301  includes a series of radially positioned actuators  4308 ,  4309 . These actuators comprise a polytetrafluoroethylene (PTFE) layer and an internal serpentine copper core  4317 . Upon heating of the copper core  4317 , the surrounding PTFE expands rapidly resulting in a generally downward movement of the actuators  4308 ,  4309 . Hence, when it is desired to eject ink from the ink ejection port  4304 , a current is passed through the actuators  4308 ,  4309  which results in them bending generally downwards as illustrated in  FIG. 946 . The downward bending movement of the actuators  4308 ,  4309  results in a substantial increase in pressure within the nozzle chamber  4302 . The increase in pressure in the nozzle chamber  4302  results in an expansion of the meniscus  4303  as illustrated in  FIG. 946 . 
     The actuators  4308 ,  4309  are activated only briefly and subsequently deactivated. Consequently, the situation is as illustrated in  FIG. 947  with the actuators  4308 ,  4309  returning to their original positions. This results in a general inflow of ink back into the nozzle chamber  4302  and a necking and breaking of the meniscus  4303  resulting in the ejection of a drop  4312 . The necking and breaking of the meniscus  4303  is a consequence of the forward momentum of the ink associated with drop  4312  and the backward pressure experienced as a result of the return of the actuators  4308 ,  4309  to their original positions. The return of the actuators  4308 ,  4309  also results in a general inflow of ink  4350  from the channel  4306  as a result of surface tension effects and, eventually, the state returns to the quiescent position as illustrated in  FIG. 945 . 
       FIGS. 948(   a ) and  948 ( b ) illustrate the principle of operation of the thermal actuator. The thermal actuator is preferably constructed from a material  4314  having a high coefficient of thermal expansion. Embedded within the material  4314  are a series of heater elements  4315  which can be a series of conductive elements designed to carry a current. The conductive elements  4315  are heated by passing a current through the elements  4315  with the heating resulting in a general increase in temperature in the area around the heating elements  4315 . The position of the elements  4315  is such that uneven heating of the material  4314  occurs. The uneven increase in temperature causes a corresponding uneven expansion of the material  4314 . Hence, as illustrated in  FIG. 948(   b ), the PTFE is bent generally in the direction  4351  shown. 
     In  FIG. 949 , there is illustrated a cross-sectional perspective view of one embodiment of a nozzle arrangement constructed in accordance with the principles previously outlined. The nozzle chamber  4302  formed with an isotropic surface etch of the wafer  4305 . The wafer  4305  can include a CMOS layer including all the required power and drive circuits. Further, the actuators  4308 ,  4309  each have a leaf or petal formation which extends towards a nozzle rim  4328  defining the ejection port  4304 . The normally inner end of each leaf or petal formation is displaceable with respect to the nozzle rim  4328 . Each activator  4308 ,  4309  has an internal copper core  4317  defining the element  4315  ( FIG. 948(   a )). The core  4317  winds in a serpentine manner to provide for substantially unhindered expansion of the actuators  4308 ,  4309 . The operation of the actuators  4308 ,  4309  is as illustrated in  FIG. 949(   a ) and  FIG. 949(   b ) such that, upon activation, the actuators  4308  bend as previously described resulting in a displacement of each petal formation away from the nozzle rim  4328  and into the nozzle chamber  4302 . The ink supply channel  4306  can be created via a deep silicon back etch of the wafer  4305  utilizing a plasma etcher or the like. The copper or aluminum core  4317  can provide a complete circuit. A central arm  4318  which can include both metal and PTFE portions provides the main structural support for the actuators  4308 ,  4309 . 
     Turning now to  FIG. 950  to  FIG. 957 , one form of manufacture of the nozzle arrangement  4301  in accordance with the principles of a preferred embodiment is shown. The nozzle arrangement  4301  is preferably manufactured using microelectromechanical (MEMS) techniques and can include the following construction techniques: 
     As shown initially in  FIG. 950 , the initial processing starting material is a standard semi-conductor wafer  4320  having a complete CMOS level  4321  to a first level of metal. The first level of metal includes portions  4322  which are utilized for providing power to the thermal actuators  4308 ,  4309 . 
     The first step, as illustrated in  FIG. 951 , is to etch a nozzle region down to the silicon wafer  4320  utilizing an appropriate mask. 
     Next, as illustrated in  FIG. 952 , a 2 micron layer of polytetrafluoroethylene (PTFE) is deposited and etched so as to define vias  4324  for interconnecting multiple levels. 
     Next, as illustrated in  FIG. 953 , the second level metal layer is deposited, masked and etched to define a heater structure  4325 . The heater structure  4325  includes via  4326  interconnected with a lower aluminum layer. 
     Next, as illustrated in  FIG. 954 , a further 2 micron layer of PTFE is deposited and etched to the depth of 1 micron utilizing a nozzle rim mask to define the nozzle rim  4328  in addition to ink flow guide rails  4329  which generally restrain any wicking along the surface of the PTFE layer. The guide rails  4329  surround small thin slots and, as such, surface tension effects are a lot higher around these slots which in turn results in minimal outflow of ink during operation. 
     Next, as illustrated in  FIG. 955 , the PTFE is etched utilizing a nozzle and actuator mask to define a port portion  4330  and slots  4331  and  4332 . 
     Next, as illustrated in  FIG. 956 , the wafer is crystallographically etched on a &lt;111&gt; plane utilizing a standard crystallographic etchant such as KOH. The etching forms a chamber  4332 , directly below the port portion  4330 . 
     In  FIG. 957 , the ink supply channel  4334  can be etched from the back of the wafer utilizing a highly anisotropic etcher such as the STS etcher from Silicon Technology Systems of the United Kingdom. An array of ink jet nozzles can be formed simultaneously with a portion of an array  4336  being illustrated in  FIG. 958 . A portion of the printhead is formed simultaneously and diced by the STS etching process. The array  4336  shown provides for four column printing with each separate column attached to a different color ink supply channel being supplied from the back of the wafer. Bond pads  4337  provide for electrical control of the ejection mechanism. 
     In this manner, large pagewidth printheads can be fabricated so as to provide for a drop-on-demand ink ejection mechanism. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double-sided polished wafer  4360 , complete a 0.5 micron, one poly, 2 metal CMOS process  4361 . This step is shown in  FIG. 960 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 959  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch the CMOS oxide layers down to silicon or second level metal using Mask  1 . This mask defines the nozzle cavity and the edge of the chips. This step is shown in  FIG. 960 . 
     3. Deposit a thin layer (not shown) of a hydrophilic polymer, and treat the surface of this polymer for PTFE adherence. 
     4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE)  4362 . 
     5. Etch the PTFE and CMOS oxide layers to second level metal using Mask  2 . This mask defines the contact vias for the heater electrodes. This step is shown in  FIG. 961 . 
     6. Deposit and pattern 0.5 microns of gold  4363  using a lift-off process using Mask  3 . This mask defines the heater pattern. This step is shown in  FIG. 962 . 
     7. Deposit 1.5 microns of PTFE  4364 . 
     8. Etch 1 micron of PTFE using Mask  4 . This mask defines the nozzle rim  4365  and the rim at the edge  4366  of the nozzle chamber. This step is shown in  FIG. 963 . 
     9. Etch both layers of PTFE and the thin hydrophilic layer down to silicon using Mask  5 . This mask defines a gap  4367  at inner edges of the actuators, and the edge of the chips. It also forms the mask for a subsequent crystallographic etch. This step is shown in  FIG. 964 . 
     10. Crystallographically etch the exposed silicon using KOH. This etch stops on &lt;111&gt; crystallographic planes  4368 , forming an inverted square pyramid with sidewall angles of 54.74 degrees. This step is shown in  FIG. 965 . 
     11. Back-etch through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  6 . This mask defines the ink inlets  4369  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 966 . 
     12. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets  4369  at the back of the wafer. 
     13. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     14. Fill the completed print heads with ink  4370  and test them. A filled nozzle is shown in  FIG. 967 . 
     IJ44 
     A preferred embodiment of the present invention discloses an inkjet printing device made up of a series of nozzle arrangements. Each nozzle arrangement includes a thermal surface actuator device which includes an L-shaped cross sectional profile and an air breathing edge such that actuation of the paddle actuator results in a drop being ejected from a nozzle utilizing a very low energy level. 
     Turning initially to  FIG. 968  to  FIG. 970 , there will now be described the operational principles of a preferred embodiment In  FIG. 968 , there is illustrated schematically a sectional view of a single nozzle arrangement  4401  which includes an ink nozzle chamber  4402  containing an ink supply which is resupplied by means of an ink supply channel  4403 . A nozzle rim  4404  is provided, across which a meniscus  4405  forms, with a slight bulge when in the quiescent state. A bend actuator device  4407  is formed on the top surface of the nozzle chamber and includes a side arm  4408  which runs generally parallel to the surface  4409  of the nozzle chamber wall so as to form an “air breathing slot”  4410  which assists in the low energy actuation of the bend actuator  4407 . Ideally, the front surface of the bend actuator  4407  is hydrophobic such that a meniscus  4412  forms between the bend actuator  4407  and the surface  4409  leaving an air pocket in slot  4410 . 
     When it is desired to eject a drop via the nozzle rim  4404 , the bend actuator  4407  is actuated so as to rapidly bend down as illustrated in  FIG. 969 . The rapid downward movement of the actuator  4407  results in a general increase in pressure of the ink within the nozzle chamber  4402 . This results in a outflow of ink around the nozzle rim  4404  and a general bulging of the meniscus  4405 . The meniscus  4412  undergoes a low amount of movement. 
     The actuator device  4407  is then turned off so as to slowly return to its original position as illustrated in  FIG. 970 . The return of the actuator  4407  to its original position results in a reduction in the pressure within the nozzle chamber  4402  which results in a general back flow of ink into the nozzle chamber  4402 . The forward momentum of the ink outside the nozzle chamber in addition to the back flow of ink  4415  results in a general necking and breaking off of the drop  4414 . Surface tension effects then draw further ink into the nozzle chamber via ink supply channel  4403 . Ink is drawn in the nozzle chamber  4403  until the quiescent position of  FIG. 968  is again achieved. 
     The actuator device  4407  can be a thermal actuator which is heated by means of passing a current through a conductive core. Preferably, the thermal actuator is provided with a conductive core encased in a material such as polytetrafluoroethylene which has a high level coefficient of expansion. As illustrated in  FIG. 971   a , a conductive core  4423  is preferably of a serpentine form and encased within a material  4424  having a high coefficient of thermal expansion. Hence, as illustrated in  FIG. 971   b , on heating of the conductive core  4423 , the material  4424  expands to a greater extent and is therefore caused to bend down in accordance with requirements. 
     Turning now to  FIG. 972 , there is illustrated a side perspective view, partly in section, of a single nozzle arrangement when in the state as described with reference to  FIG. 969 . The nozzle arrangement  4401  can be formed in practice on a semiconductor wafer  4420  utilizing standard MEMS techniques. 
     The silicon wafer  4420  preferably is processed so as to include a CMOS layer  4421  which can include the relevant electrical circuitry required for the full control of a series of nozzle arrangements  4401  formed so as to form a printhead unit On top of the CMOS layer  4421  is formed a glass layer  4422  and an actuator  4407  which is driven by means of passing a current through a serpentine copper coil  4423  which is encased in the upper portions of a polytetrafluoroethylene (PTFE) layer  4424 . Upon passing a current through the coil  4423 , the coil  4423  is heated as is the PTFE layer  4424 . PTFE has a very high coefficient of thermal expansion and hence expands rapidly. The coil  4423  constructed in a serpentine nature is able to expand substantially with the expansion of the PTFE layer  4424 . The PTFE layer  4424  includes a lip portion  4408  which upon expansion, bends in a scooping motion as previously described. As a result of the scooping motion, the meniscus  4405  generally bulges and results in a consequential ejection of a drop of ink. The nozzle chamber  4402  is later replenished by means of surface tension effects in drawing ink through an ink supply channel  4403  which is etched through the wafer through the utilization of a highly an isotropic silicon trench etcher. Hence, ink can be supplied to the back surface of the wafer and ejected by means of actuation of the actuator  4407 . The gap between the side arm  4408  and chamber wall  4409  allows for a substantial breathing effect which results in a low level of energy being required for drop ejection. 
     A large number of arrangements  4401  of  FIG. 972  can be formed together on a wafer with the arrangements being collected into printheads which can be of various sizes in accordance with requirements. Turning now to  FIG. 973 , there is illustrated one form of an array  4430  which is designed so as to provide three color printing with each color providing two spaced apart rows of nozzle arrangements  4434 . The three groupings can comprise groupings  4431 ,  4432  and  4433  with each grouping supplied with a separate ink color so as to provide for full color printing capability. Additionally, a series of bond pads e.g.  4436  are provided for TAB bonding control signals to the printhead  4430 . Obviously, the arrangement  4430  of  FIG. 973  illustrates only a portion of a printhead which can be of a length as determined by requirements. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  4420 , complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process  4421 . Relevant features of the wafer at this step are shown in  FIG. 975 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 974  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch the CMOS oxide layers down to silicon or second level metal using Mask  1 . This mask defines the nozzle cavity and the edge of the chips. Relevant features of the wafer at this step are shown in  FIG. 975 . 
     3. Plasma etch the silicon to a depth of 20 microns using the oxide as a mask. This step is shown in  FIG. 976 . 
     4. Deposit 23 microns of sacrificial material  4450  and planarize down to oxide using CMP. This step is shown in  FIG. 977 . 
     5. Etch the sacrificial material to a depth of 15 microns using Mask  2 . This mask defines the vertical paddle  4408  at the end of the actuator. This step is shown in  FIG. 978 . 
     6. Deposit a thin layer (not shown) of a hydrophilic polymer, and treat the surface of this polymer for PTFE adherence. 
     7. Deposit 1.5 microns of polytetrafluoroethylene (PTFE)  4451 . 
     8. Etch the PTFE and CMOS oxide layers to second level metal using Mask  3 . This mask defines the contact vias  4452  for the heater electrodes. This step is shown in  FIG. 979 . 
     9. Deposit and pattern 0.5 microns of gold  4453  using a lift-off process using Mask  4 . This mask defines the heater pattern. This step is shown in  FIG. 980 . 
     10. Deposit 1.5 microns of PTFE  4454 . 
     11. Etch 1 micron of PTFE using Mask  5 . This mask defines the nozzle rim  4404  and the rim  4404  at the edge of the nozzle chamber. This step is shown in  FIG. 981 . 
     12. Etch both layers of PTFE and the thin hydrophilic layer down to the sacrificial layer using Mask  6 . This mask defines the gap  4410  at the edges of the actuator and paddle. This step is shown in  FIG. 982 . 
     13. Back-etch through the silicon wafer to the sacrificial layer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask  7 . This mask defines the ink inlets which  4403  are etched through the wafer. This step is shown in  FIG. 983 . 
     14. Etch the sacrificial layers. The wafer is also diced by this etch. 
     15. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     16. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     17. Fill the completed printheads with ink  4455  and test them. A filled nozzle is shown in  FIG. 984 . 
     IJ45 
     In a preferred embodiment, an ink jet print head is constructed from a series of nozzle arrangements where each nozzle arrangement includes a magnetic plate actuator which is actuated by a coil which is pulsed so as to move the magnetic plate and thereby cause the ejection of ink. The movement of the magnetic plate results in a leaf spring device being extended resiliently such that when the coil is deactivated, the magnetic plate returns to a rest position resulting in the ejection of a drop of ink from an aperture created within the plate. 
     Turning now to  FIGS. 985  to  FIG. 987 , there will now be explained the operation of this embodiment. 
     Turning initially to  FIG. 985 , there is illustrated an ink jet nozzle arrangement  4501  which includes a nozzle chamber  4502  which connects with an ink ejection nozzle  4503  such that, when in a quiescent position, an ink meniscus  4504  forms over the nozzle  4503 . The nozzle  4503  is formed in a magnetic nozzle plate  4505  which can be constructed from a ferrous material. Attached to the nozzle plate  4505  is a series of leaf springs e.g.  4506 ,  4507  which bias the nozzle plate  4505  away from a base plate  4509 . Between the nozzle plate  4505  and the base plate  4509 , there is provided a conductive coil  4510  which is interconnected and controlled via a lower circuitry layer  4511  which can comprise a standard CMOS circuitry layer. The ink chamber  4502  is supplied with ink from a lower ink supply channel  4512  which is formed by etching through a wafer substrate  4513 . The wafer substrate  4513  can comprise a semiconductor wafer substrate. The ink chamber  4502  is interconnected to the ink supply channel  4512  by means of a series of slots  4514  which can be etched through the CMOS layer  4511 . 
     The area around the coil  4510  is hydrophobically treated so that, during operation, a small meniscus e.g.  4516 ,  4517  forms between the nozzle plate  4505  and base plate  4509 . 
     When it is desired to eject a drop of ink, the coil  4510  is energized. This results in a movement of the plate  4505  as illustrated in  FIG. 986 . The general downward movement of the plate  4505  results in a substantial increase in pressure within nozzle chamber  4502 . The increase in pressure results in a rapid growth in the meniscus  4504  as ink flows out of the nozzle chamber  4503 . The movement of the plate  4505  also results in the springs  4506 ,  4507  undergoing a general resilient extension. The small width of the slot  4514  results in minimal outflows of ink into the nozzle chamber  4502 . 
     Moments later, as illustrated in  FIG. 987 , the coil  4510  is deactivated resulting in a return of the plate  4505  towards its quiescent position as a result of the springs  4506 ,  4507  acting on the nozzle plate  4505 . The return of the nozzle plate  4505  to its quiescent position results in a rapid decrease in pressure within the nozzle chamber  4502  which in turn results in a general back flow of ink around the ejection nozzle  4503 . The forward momentum of the ink outside the nozzle plate  4505  and the back suction of the ink around the ejection nozzle  4503  results in a drop  4519  being formed and breaking off so as to continue to the print media. 
     The surface tension characteristics across the nozzle  4503  result in a general inflow of ink from the ink supply channel  4512  until such time as the quiescent position of  FIG. 985  is again reached. In this manner, a coil actuated magnetic ink jet print head is formed for the adoption of ink drops on demand. Importantly, the area around the coil  4510  is hydrophobically treated so as to expel any ink from flowing into this area. 
     Turning now to  FIG. 988 , there is illustrated a side perspective view, partly in section of a single nozzle arrangement constructed in accordance with the principles as previously outlined with respect to  FIGS. 985  to  FIG. 987 . The arrangement  4501  includes a nozzle plate  4505  which is formed around an ink supply chamber  4502  and includes an ink ejection nozzle  4503 . A series of leaf spring elements  4506 - 4508  are also provided which can be formed from the same material as the nozzle plate  4505 . A base plate  4509  also is provided for encompassing the coil  4510 . The wafer  4513  includes a series of slots  4514  for the wicking and flowing of ink into nozzle chamber  4502  with the nozzle chamber  4502  being interconnected via the slots with an ink supply channel  4512 . The slots  4514  are of a thin elongated form so as to provide for fluidic resistance to a rapid outflow of fluid from the chamber  4502 . 
     The coil  4510  is conductive interconnected at a predetermined portion (not shown) with a lower CMOS layer for the control and driving of the coil  4510  and movement of base plate  4505 . Alternatively, the plate  4509  can be broken into two separate semi-circular plates and the coil  4510  can have separate ends connected through one of the semi circular plates through to a lower CMOS layer. 
     Obviously, an array of ink jet nozzle devices can be formed at a time on a single silicon wafer so as to form multiple printheads. 
     One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps: 
     1. Using a double sided polished wafer  4513 , complete a 0.5 micron, one poly, 2 metal CMOS process  4511 . Due to high current densities, both metal layers should be copper for resistance to electromigration. This step is shown in  FIG. 990 . For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle.  FIG. 989  is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations. 
     2. Etch the CMOS oxide layers down to silicon or aluminum using Mask  1 . This mask defines the nozzle chamber inlet cross, the edges of the print heads chips, and the vias for the contacts from the second level metal electrodes to the two halves of the split fixed magnetic plate  4509 . 
     3. Plasma etch the silicon to a depth of 15 microns, using oxide from step 2 as a mask. This etch does not substantially etch the second level metal. This step is shown in  FIG. 991 . 
     4. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosen due to a high saturation flux density of 2 Tesla, and a low coercivity. [Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturation magnetic flux density, Nature 392, 796-798 (1998)]. 
     5. Spin on 4 microns of resist  4550 , expose with Mask  2 , and develop. This mask defines the split fixed magnetic plate  4509 , for which the resist acts as an electroplating mold. This step is shown in  FIG. 992 . 
     6. Electroplate 3 microns of CoNiFe. This step is shown in  FIG. 993 . 
     7. Strip the resist and etch the exposed seed layer. This step is shown in  FIG. 994 . 
     8. Deposit 0.5 microns of silicon nitride  4551 , which insulates the solenoid from the fixed magnetic plate  4509 . 
     9. Etch the nitride layer using Mask  3 . This mask defines the contact vias from each end of the solenoid coil to the two halves of the split fixed magnetic plate  4509 , as well as returning the nozzle chamber  4502  to a hydrophilic state. This step is shown in  FIG. 995 . 
     10. Deposit an adhesion layer plus a copper seed layer. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities. 
     11. Spin on 13 microns of resist  4552  and expose using Mask  4 , which defines the solenoid spiral coil, for which the resist acts as an electroplating mold. As the resist is thick and the aspect ratio is high, an X-ray proximity process, such as LIGA, can be used. This step is shown in  FIG. 996 . 
     12. Electroplate 12 microns of copper  4510 . 
     13. Strip the resist and etch the exposed copper seed layer. This step is shown in  FIG. 997 . 
     14. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated. 
     15. Deposit 0.1 microns of silicon nitride, which acts as a corrosion barrier (not shown). 
     16. Deposit 0.1 microns of PTFE (not shown), which makes the top surface of the fixed magnetic plate  4509  and the solenoid hydrophobic, thereby preventing the space between the solenoid and the magnetic piston from filling with ink (if a water based ink is used. In general, these surfaces should be made ink-phobic). 
     17. Etch the PTFE layer using Mask  5 . This mask defines the hydrophilic region of the nozzle chamber  4502 . The etch returns the nozzle chamber  4502  to a hydrophilic state. 
     18. Deposit 1 micron of sacrificial material  4553 . This defines the magnetic gap, and the travel of the magnetic piston. 
     19. Etch the sacrificial layer using Mask  6 . This mask defines the spring posts. This step is shown in  FIG. 998 . 
     20. Deposit a seed layer of CoNiFe. 
     21. Deposit 12 microns of resist  4554 . As the solenoids will prevent even flow during a spin-on application, the resist should be sprayed on. Expose the resist using Mask  7 , which defines the walls of the magnetic plunger, plus the spring posts. As the resist is thick and the aspect ratio is high, an X-ray proximity process, such as LIGA, can be used. This step is shown in  FIG. 999 . 
     22. Electroplate 12 microns of CoNiFe  4555 . This step is shown in  FIG. 1000 . 
     23. Deposit a seed layer of CoNiFe. 
     24. Spin on 4 microns of resist  4556 , expose with Mask  8 , and develop. This mask defines the roof of the magnetic plunger, the nozzle, the springs, and the spring posts. The resist forms an electroplating mold for these parts. This step is shown in  FIG. 1001 . 
     25. Electroplate 3 microns of CoNiFe  4557 . This step is shown in  FIG. 1002 . 
     26. Strip the resist, sacrificial, and exposed seed layers. This step is shown in  FIG. 1003 . 
     27. Back-etch through the silicon wafer until the nozzle chamber inlet cross is reached using Mask  9 . This etch may be performed using an ASE Advanced Silicon Etcher from Surface Technology Systems. The mask defines the ink inlets  4512  which are etched through the wafer. The wafer is also diced by this etch. This step is shown in  FIG. 1004 . 
     28. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer. 
     29. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. 
     30. Fill the completed printheads with ink  4558  and test them. A filled nozzle is shown in  FIG. 1005 . 
     IJ46 
     Recently, for example, in PCT Application No. PCT/AU98/00550 the present applicant has proposed an inkjet printing device which utilizes micro-electromechanical (MEMS) processing techniques in the construction of a thermal bend actuator type device for the ejection of fluid from a nozzle chamber. 
     The aforementioned application discloses an actuator which is substantially exposed to an external atmosphere, often adjacent a print media surface. This is likely to lead to substantial operational problems in that the exposed actuator could be damaged by foreign objects or paper dust etc. leading to a malfunction. 
     Accordingly, there is provided an inkjet printhead chip that comprises 
     a substrate that incorporates drive circuitry; 
     a plurality of nozzle arrangements that are positioned on the substrate, each nozzle arrangement comprising: 
     a nozzle chamber wall and a roof wall positioned on the substrate to define a nozzle chamber, the roof wall defining an ink ejection port in fluid communication with the nozzle chamber; 
     an ink ejection member that is positioned in the nozzle chamber and is displaceable towards and away from the ink ejection port to eject ink from the ink ejection port; and 
     an elongate actuator that is fast, at one end, to the substrate to receive an electrical signal from the drive circuitry and fast, at an opposite end, with the ink ejection member, the actuator incorporating a heating circuit that is connected to the drive circuitry layer the heating circuit being positioned and configured so that, on receipt of, and termination of, a suitable electrical drive signal from the drive circuitry layer, the heating circuit serves to generate differential thermal expansion and contraction, respectively, such that the actuator is displaced to drive the ink ejection member towards and away from the ink ejection port, wherein 
     the drive circuitry is configured to generate a heating signal which is sufficient to heat the actuator, without generating movement, to an extent such that the ink is heated, prior to generating the drive signal. 
     The drive circuitry may be configured to generate a series of pulses with pulses of a predetermined first duration defining heating signals and a series of pulses of a predetermined second duration defining drive signals. 
     The printhead chip may include a number of temperature sensors that are connected to a temperature determination unit for detecting ink temperature and an ink ejection drive unit for determining whether or not preheating of the ink is required. 
     The drive circuitry may be defined by CMOS circuitry positioned in the substrate. The CMOS circuitry may incorporate control logic circuitry for each nozzle arrangement, which is connected to the heating circuit. 
     Each control logic circuitry may include shift register circuitry for receiving a data input, transfer register circuitry that is connected to the shift register circuitry to generate a transfer enable signal and to latch the data input and to generate a firing phase control signal, and gate circuitry that is connected to the transfer register circuitry to be activated by the control signal to output a heating pulse which is received by the heating circuit. 
     Each elongate actuator may have a laminated structure of at least two layers, with one of the layers defining the heating circuit. 
     Each elongate actuator may have three layers in the form of a middle layer of a resiliently flexible, non-electrically conductive material, and a pair of opposite, substantially identical metal layers. 
     According to another aspect, there is provided an inkjet printhead formed on a silicon wafer and including a plurality of nozzle devices, each nozzle device comprising a nozzle chamber and an aperture through which ink from the nozzle chamber is ejected, an actuator for applying pressure to ink within the nozzle chamber to cause ejection of an ink drop through the aperture, and drive circuitry for controlling the actuator, wherein the drive circuitry and the actuator share area of said silicon wafer. 
     Preferably the actuator and the drive circuitry overlap. 
     Preferably the actuator overlies the drive circuitry. 
     Preferably the actuator is external to the nozzle chamber. 
     Preferably the actuator is a thermal bend actuator. 
     Preferably the actuator is attached to a paddle which resides within the nozzle chamber. 
     Description of Preferred and Other Embodiments 
     The preferred embodiment is a 1600 dpi modular monolithic print head suitable for incorporation into a wide variety of page width printers and in print-on-demand camera systems. The print head is fabricated by means of Micro-Electro-Mechanical-Systems (MEMS) technology, which refers to mechanical systems built on the micron scale, usually using technologies developed for integrated circuit fabrication. 
     As more than 50,000 nozzles are required for a 1600 dpi A4 photographic quality page width printer, integration of the drive electronics on the same chip as the print head is essential to achieve low cost. Integration allows the number of external connections to the print head to be reduced from around 50,000 to around 100. To provide the drive electronics, the preferred embodiment integrates CMOS logic and drive transistors on the same wafer as the MEMS nozzles. MEMS has several major advantages over other manufacturing techniques:
     mechanical devices can be built with dimensions and accuracy on the micron scale;   millions of mechanical devices can be made simultaneously, on the same silicon wafer; and   the mechanical devices can incorporate electronics.   

     To reduce the cost of manufacturing each mechanical device, as many as possible devices should be manufactured from the same silicon wafer. 
     The drive circuitry to drive a paddle actuator takes up space on a silicon wafer. The actuator itself also takes up space. A greater number of devices could be yielded from a single silicon wafer if the drive circuit and actuator shared silicon area. That is, a greater yield could be achieved if the drive circuitry and actuator overlapped. This might be achieved by having the actuator completely or partly overlying the drive circuitry or by having the drive circuitry completely or partly overlying the actuator. That is, the drive circuitry could be above or below the actuator in part or in full. 
     The term “IJ46 print head” is used herein to identify print heads made according to the preferred embodiment of this invention. 
     Operating Principle 
     One embodiment relies on the utilization of a thermally actuated lever arm which is utilized for the ejection of ink. The nozzle chamber from which ink ejection occurs includes a thin nozzle rim around which a surface meniscus is formed. A nozzle rim is formed utilizing a self aligning deposition mechanism. The preferred embodiment also includes the advantageous feature of a flood prevention rim around the ink ejection nozzle. 
     Turning initially to  FIG. 1006  to  FIG. 1008 , there will be now initially explained the operation of principles of the ink jet print head of the preferred embodiment. In  FIG. 1006 , there is illustrated a single nozzle arrangement  46001  which includes a nozzle chamber  46002  which is supplied via an ink supply channel  46003  so as to form a meniscus  46004  around a nozzle rim  46005 . A thermal actuator mechanism  46006  is provided and includes an end paddle  46007  which can be a circular form. The paddle  46007  is attached to an actuator arm  46008  which pivots at a post  46009 . The actuator arm  46008  includes two layers  46010 ,  46011  which are formed from a conductive material having a high degree of stiffness, such as titanium nitride. The bottom layer  46010  forms a conductive circuit interconnected to post  46009  and further includes a thinned portion near the end post  46009 . Hence, upon passing a current through the bottom layer  46010 , the bottom layer is heated in the area adjacent the post  46009 . Without the heating, the two layers  46010 ,  46011  are in thermal balance with one another. The heating of the bottom layer  46010  causes the overall actuator mechanism  46006  to bend generally upwards and hence paddle  46007  as indicated in  FIG. 1007  undergoes a rapid upward movement. The rapid upward movement results in an increase in pressure around the rim  46005  which results in a general expansion of the meniscus  46004  as ink flows outside the chamber. The conduction to the bottom layer  46010  is then turned off and the actuator arm  46006 , as illustrated in  FIG. 1008  begins to return to its quiescent position. The return results in a movement of the paddle  46007  in a downward direction. This in turn results in a general sucking back of the ink around the nozzle  46005 . The forward momentum of the ink outside the nozzle in addition to the backward momentum of the ink within the nozzle chamber results in a drop  46014  being formed as a result of a necking and breaking of the meniscus  46004 . Subsequently, due to surface tension effects across the meniscus  46004 , ink is drawn into the nozzle chamber  46002  from the ink supply channel  46003 . 
     The operation of the preferred embodiment has a number of significant features. Firstly, there is the aforementioned balancing of the layer  46010 ,  46011 . The utilization of a second layer  46011  allows for more efficient thermal operation of the actuator device  46006 . Further, the two-layer operation ensures thermal stresses are not a problem upon cooling during manufacture, thereby reducing the likelihood of peeling during fabrication. This is illustrated in  FIG. 1009  and  FIG. 1010 . In  FIG. 1009 , there is shown the process of cooling off a thermal actuator arm having two balanced material layers  46020 ,  46021  surrounding a central material layer  46022 . The cooling process affects each of the conductive layers  46020 ,  46021  equally resulting in a stable configuration. In  FIG. 1010 , a thermal actuator arm having only one conductive layer  46020  as shown. Upon cooling after manufacture, the upper layer  46020  is going to bend with respect to the central layer  46022 . This is likely to cause problems due to the instability of the final arrangement and variations and thickness of various layers which will result in different degrees of bending. 
     Further, the arrangement described with reference to  FIGS. 1006 to 1009  includes an ink jet spreading prevention rim  46025  ( FIG. 1006 ) which is constructed so as to provide for a pit  46026  around the nozzle rim  46005 . Any ink which should flow outside of the nozzle rim  46005  is generally caught within the pit  46026  around the rim and thereby prevented from flowing across the surface of the ink jet print head and influencing operation. This arrangement can be clearly seen in  FIG. 1016 . 
     Further, the nozzle rim  46005  and ink spread prevention rim  46025  are formed via a unique chemical mechanical planarization technique. This arrangement can be understood by reference to  FIG. 1011  to  FIG. 1014 . Ideally, an ink ejection nozzle rim is highly symmetrical in form as illustrated at  46030  in  FIG. 1011 . The utilization of a thin highly regular rim is desirable when it is time to eject ink. For example, in  FIG. 1012  there is illustrated a drop being ejected from a rim during the necking and breaking process. The necking and breaking process is a high sensitive one, complex chaotic forces being involved Should standard lithography be utilized to form the nozzle rim, it is likely that the regularity or symmetry of the rim can only be guaranteed to within a certain degree of variation in accordance with the lithographic process utilized. This may result in a variation of the rim as illustrated at  46035  in  FIG. 1013 . The rim variation leads to a non-symmetrical rim  46035  as illustrated in  FIG. 1013 . This variation is likely to cause problems when forming a droplet. The problem is illustrated in  FIG. 1016  wherein the meniscus  36  creeps along the surface  46037  where the rim is bulging to a greater width. This results in an ejected drop likely to have a higher variance in direction of ejection. 
     In the preferred embodiment, to overcome this problem, a self aligning chemical mechanical planarization (CMP) technique is utilized. A simplified illustration of this technique will now be discussed with reference to  FIG. 1015 . In  FIG. 1015 , there is illustrated a silicon substrate  46040  upon which is deposited a first sacrificial layer  46041  and a thin nozzle layer  46042  shown in exaggerated form. The sacrificial layer is first deposited and etched so as to form a “blank” for the nozzle layer  46042  that is deposited over all surfaces conformally. In an alternative manufacturing process, a further sacrificial material layer can be deposited on top of the nozzle layer  46042 . 
     Next, the critical step is to chemically mechanically planarize the nozzle layer and sacrificial layers down to a first level eg.  46044 . The chemical mechanical planarization process acts to effectively “chop off” the top layers down to level  46044 . Through the utilization of conformal deposition, a regular rim is produced. The result, after chemical mechanical planarization, is illustrated schematically in  FIG. 1016 . 
     The description of the preferred embodiments will now proceed by first describing an ink jet preheating step preferably utilized in the IJ46 device. 
     Ink Preheating 
     In the preferred embodiment, an ink preheating step is utilized so as to bring the temperature of the print head arrangement to be within a predetermined bound. The steps utilized are illustrated at  46101  in  FIG. 1017 . Initially, the decision to initiate a printing run is made at  46102 . Before any printing has begun, the current temperature of the print head is sensed to determine whether it is above a predetermined threshold. If the heated temperature is too low, a preheat cycle  46104  is applied which heats the print head by means of heating the thermal actuators to be above a predetermined temperature of operation. Once the temperature has achieved a predetermined temperature, the normal print cycle  46105  has begun. 
     The utilization of the preheating step  46104  results in a general reduction in possible variation in factors such as viscosity etc. allowing for a narrower operating range of the device and, the utilization of lower thermal energies in ink ejection. 
     The preheating step can take a number of different forms. Where the ink ejection device is of a thermal bend actuator type, it would normally receive a series of clock pulse as illustrated in  FIG. 1018  with the ejection of ink requiring clock pulses  46110  of a predetermined thickness so as to provide enough energy for ejection. 
     As illustrated in  FIG. 1019 , when it is desired to provide for preheating capabilities, these can be provided through the utilization of a series of shorter pulses eg.  46111 , which whilst providing thermal energy to the print head, fail to cause ejection of the ink from the ink ejection nozzle. 
       FIG. 1021  illustrates an example graph of the print head temperature during a printing operation. Assuming the print head has been idle for a substantial period of time, the print head temperature, initially  46115 , will be the ambient temperature. When it is desired to print, a preheating step ( 46104  of  FIG. 1017 ) is executed such that the temperature rises as shown at  46116  to an operational temperature T 2  at  46117 , at which point printing can begin and the temperature left to fluctuate in accordance with usage requirements. 
     Alternately, as illustrated in  FIG. 1021 , the print head temperature can be continuously monitored such that should the temperature fall below a threshold eg.  46120 , a series of preheating cycles are injected into the printing process so as to increase the temperature to  46121 , above a predetermined threshold. 
     Assuming the ink utilized has properties substantially similar to that of water, the utilization of the preheating step can take advantage of the substantial fluctuations in ink viscosity with temperature. Of course, other operational factors may be significant and the stabilisation to a narrower temperature range provides for advantageous effects. As the viscosity changes with changing temperature, it would be readily evident that the degree of preheating required above the ambient temperature will be dependant upon the ambient temperature and the equilibrium temperature of the print head during printing operations. Hence, the degree of preheating may be varied in accordance with the measured ambient temperature so as to provide for optimal results. 
     A simple operational schematic is illustrated in  FIG. 1023  with the print head  46130  including an on-board series of temperature sensors which are connected to a temperature determination unit  46131  for determining the current temperature which in turn outputs to an ink ejection drive unit  46132  which determines whether preheating is required at any particular stage. The on-chip (print head) temperature sensors can be simple MEMS temperature sensors, the construction of which is well known to those skilled in the art. 
     Manufacturing Process 
     IJ46 device manufacture can be constructed from a combination of standard CMOS processing, and MEMS postprocessing. Ideally, no materials should be used in the MEMS portion of the processing which are not already in common use for CMOS processing. In the preferred embodiment, the only MEMS materials are PECVD glass, sputtered TiN, and a sacrificial material (which may be polyimide, PSG, BPSG, aluminum, or other materials). Ideally, to fit corresponding drive circuits between the nozzles without increasing chip area, the minimum process is a 0.5 micron, one poly, 3 metal CMOS process with aluminum metalization. However, any more advanced process can be used instead. Alternatively, NMOS, bipolar, BiCMOS, or other processes may be used. CMOS is recommended only due to its prevalence in the industry, and the availability of large amounts of CMOS fab capacity. 
     For a 100 mm photographic print head using the CMY process color model, the CMOS process implements a simple circuit consisting of 19,200 stages of shift register, 19,200 bits of transfer register, 19,200 enable gates, and 19,200 drive transistors. There are also some clock buffers and enable decoders. The clock speed of a photo print head is only 3.8 MHz, and a 30 ppm A4 print head is only 14 MHz, so the CMOS performance is not critical. The CMOS process is fully completed, including passivation and opening of bond pads before the MEMS processing begins. This allows the CMOS processing to be completed in a standard CMOS fab, with the MEMS processing being performed in a separate facility. 
     Reasons for Process Choices 
     It will be understood from those skilled in the art of manufacture of MEMS devices that there are many possible process sequences for the manufacture of an IJ46 print head. The process sequence described here is based on a ‘generic’ 0.5 micron (drawn) n-well CMOS process with 1 poly and three metal layers. This table outlines the reasons for some of the choices of this ‘nominal’ process, to make it easier to determine the effect of any alternative process choices. 
     
       
         
           
               
               
             
               
                   
               
               
                 Nominal Process 
                 Reason 
               
               
                   
               
             
            
               
                 CMOS 
                 Wide availability 
               
               
                 0.5 micron or less 
                 0.5 micron is required to fit drive electronics 
               
               
                   
                 under the actuators 
               
               
                 0.5 micron or more 
                 Fully amortized fabs, low cost 
               
               
                 N-well 
                 Performance of n-channel is more important 
               
               
                   
                 than p-channel transistors 
               
               
                 6” wafers 
                 Minimum practical for 4” monolithic print 
               
               
                   
                 heads 
               
               
                 1 polysilicon layer 
                 2 poly layers are not required, as there is little 
               
               
                   
                 low current connectivity 
               
               
                 3 metal layers 
                 To supply high currents, most of metal 3 also 
               
               
                   
                 provides sacrificial structures 
               
               
                 Aluminum metalization 
                 Low cost, standard for 0.5 micron processes 
               
               
                   
                 (copper may be more efficient) 
               
               
                   
               
            
           
         
       
     
                            Mask Summary                                         Mask #   Mask   Notes   Type   Pattern   Align to   CD                                                 1   N-well       CMOS 1    Light   Flat     4 μm       2   Active   Includes   CMOS 2    Dark   N-Well     1 μm               nozzle               chamber       3   Poly       CMOS 3    Dark   Active   0.5 μm       4   N+       CMOS 4    Dark   Poly     4 μm       5   P+       CMOS 4    Light   Poly     4 μm       6   Contact   Includes   CMOS 5    Light   Poly   0.5 μm               nozzle               chamber       7   Metal 1       CMOS 6    Dark   Contact   0.6 μm       8   Via 1   Includes   CMOS 7    Light   Metal 1   0.6 μm               nozzle               chamber       9   Metal 2   Includes   CMOS 8    Dark   Via 1   0.6 μm               sacrificial               al.       10   Via 2   Includes   CMOS 9    Light   Metal 2   0.6 μm               nozzle               chamber       11   Metal 3   Includes   CMOS 10   Dark   Poly     1 μm               sacrificial               al.       12   Via 3   Overcoat,   CMOS 11   Light   Poly   0.6 μm               but 0.6 μm               CD       13   Heater       MEMS 1    Dark   Poly   0.6 μm       14   Actuator       MEMS 2    Dark   Heater     1 μm       15   Nozzle   For CMP   MEMS 3    Dark   Poly     2 μm               control       16   Chamber       MEMS 4    Dark   Nozzle     2 μm       17   Inlet   Backside   MEMS 5    Light   Poly     4 μm               deep               silicon               etch                    
Example Process Sequence (Including CMOS Steps)
 
     Although many different CMOS and other processes can be used, this process description is combined with an example CMOS process to show where MEMS features are integrated in the CMOS masks, and show where the CMOS process may be simplified due to the low CMOS performance requirements. 
     Process steps described below are part of the example ‘generic’ IP3M 0.5 micron CMOS process. 
     As shown in  FIG. 18 , processing starts with a standard 6″ p-type &lt;100&gt; wafers. (8″ wafers can also be used, giving a substantial increase in primary yield). 
     Using the n-well mask of  FIG. 1024 , implant the n-well transistor portions  46210  of  FIG. 1025 . 
     Grow a thin layer of SiO 2  and deposit Si 3 N 4  forming a field oxide hard mask. 
     Etch the nitride and oxide using the active mask of  FIG. 1027 . The mask is oversized to allow for the LOCOS bird&#39;s beak. The nozzle chamber region is incorporated in this mask, as field oxide is excluded from the nozzle chamber. The result is a series of oxide regions  46212 , illustrated in  FIG. 1028 . 
     Implant the channel-stop using the n-well mask with a negative resist, or using a complement of the n-well mask. 
     Perform any required channel stop implants as required by the CMOS process used. 
     Grow 0.5 micron of field oxide using LOCOS. 
     Perform any required n/p transistor threshold voltage adjustments. Depending upon the characteristics of the CMOS process, it may be possible to omit the threshold adjustments. This is because the operating frequency is only 3.8 MHz, and the quality of the I-devices is not critical. The n-transistor threshold is more significant, as the on-resistance of the n-channel drive transistor has a significant effect on the efficiency and power consumption while printing. 
     Grow the gate oxide. 
     Deposit 0.3 microns of poly, and pattern using the poly mask illustrated in  FIG. 1030  so as to form poly portions  46214  shown in  FIG. 1029 . 
     Perform the n+ implant shown e.g.  46216  in  FIG. 1034  using the n+ mask shown in  FIG. 1033 . The use of a drain engineering processes such as LDD should not be required, as the performance of the transistors is not critical. 
     Perform the p+ implant shown e.g.  218  in  FIG. 1037 , using a complement of the n+mask shown in  FIG. 1036 , or using the n+ mask with a negative resist. The nozzle chamber region will be doped either n+ or p+ depending upon whether it is included in the n+ mask or not The doping of this silicon region is not relevant as it is subsequently etched, and the STS ASE etch process recommended does not use boron as an etch stop. 
     Deposit 0.6 microns of PECVD TEOS glass to form ILD  1 , shown e.g.  46220  in  FIG. 1040 . 
     Etch the contact cuts using the contact mask of  FIG. 1039 . The nozzle region is treated as a single large contact region, and will not pass typical design rule checks. This region should therefore be excluded from the DRC. 
     Deposit 0.6 microns of aluminum to form metal  46001 . 
     Etch the aluminum using the metal  46001  mask shown in  FIG. 1042  so as to form metal regions e.g.  46224  shown in  FIG. 1043 . The nozzle metal region is covered with metal  1  e.g.  46225 . This aluminum  46225  is sacrificial, and is etched as part of the MEMS sequence. The inclusion of metal  46001  in the nozzle is not essential, but helps reduce the step in the neck region of the actuator lever arm. 
     Deposit 0.7 microns of PECVD TEOS glass to form ILD  2  regions e.g.  46228  of  FIG. 1046 . 
     Etch the contact cuts using the via 1 mask shown in  FIG. 1045 . The nozzle region is treated as a single large via region, and again it will not pass DRC. 
     Deposit 0.6 microns of aluminum to form metal  2 . 
     Etch the aluminum using the metal  2  mask shown in  FIG. 1047  so as to form metal portions e.g.  46230  shown in  FIG. 1048 . The nozzle region  46231  is fully covered with metal  2 . This aluminum is sacrificial, and is etched as part of the MEMS sequence. The inclusion of metal  2  in the nozzle is not essential, but helps reduce the step in the neck region of the actuator lever arm. Sacrificial metal  2  is also used for another fluid control feature. A relatively large rectangle of metal  2  is included in the neck region  46233  of the nozzle chamber. This is connected to the sacrificial metal  3 , so is also removed during the MEMS sacrificial aluminum etch. This undercuts the lower rim of the nozzle chamber entrance for the actuator (which is formed from ILD  3 ). The undercut adds 90 degrees to angle of the fluid control surface, and thus increases the ability of this rim to prevent ink surface spread. 
     Deposit 0.7 microns of PECVD TEOS glass to form ILD  3 . 
     Etch the contact cuts using the via 2 mask shown in  FIG. 1050  so as to leave portions e.g.  46236  shown in  FIG. 1051 . As well as the nozzle chamber, fluid control rims are also formed in ILD  3 . These will also not pass DRC. 
     Deposit 1.0 microns of aluminum to form metal  3 . 
     Etch the aluminum using the metal  3  mask shown in  FIG. 1052  so as to leave portions e.g.  46238  as shown in  FIG. 1053 . Most of metal  46003  e.g.  46239  is a sacrificial layer used to separate the actuator and paddle from the chip surface. Metal  3  is also used to distribute V+ over the chip. The nozzle region is fully covered with metal  3  e.g.  46240 . This aluminum is sacrificial, and is etched as part of the MEMS sequence. The inclusion of metal  3  in the nozzle is not essential, but helps reduce the step in the neck region of the actuator lever arm. 
     Deposit 0.5 microns of PECVD TEOS glass to form the overglass. 
     Deposit 0.5 microns of Si 3 N 4  to form the passivation layer. 
     Etch the passivation and overglass using the via 3 mask shown in  FIG. 1055  so as to form the arrangement of  FIG. 1056 . This mask includes access  46242  to the metal  3  sacrificial layer, and the vias e.g.  46243  to the heater actuator. Lithography of this step has 0.6 micron critical dimensions (for the heater vias) instead of the normally relaxed lithography used for opening bond pads. This is the one process step which is different from the normal CMOS process flow. This step may either be the last process step of the CMOS process, or the first step of the MEMS process, depending upon the fab setup and transport requirements. 
     Wafer Probe. Much, but not all, of the functionality of the chips can be determined at this stage. If more complete testing at this stage is required, an active dummy load can be included on chip for each drive transistor. This can be achieved with minor chip area penalty, and allows complete testing of the CMOS circuitry. 
     Transfer the wafers from the CMOS facility to the MEMS facility. These may be in the same fab, or may be distantly located. 
     Deposit 0.9 microns of magnetron sputtered TIN. Voltage is −65V, magnetron current is 7.5 A, argon gas pressure is 0.3 Pa, temperature is 300° C. This results in a coefficient of thermal expansion of 9.4×10 −6 /° C., and a Young&#39;s modulus of 600 GPa [Thin Sold Films 270 p 266, 1995], which are the key thin film properties used. 
     Etch the TiN using the heater mask shown in  FIG. 1058 . This mask defines the heater element, paddle arm, and paddle. There is a small gap  46247  shown in  FIG. 1059  between the heater and the TiN layer of the paddle and paddle arm. This is to prevent electrical connection between the heater and the ink, and possible electrolysis problems. Sub-micron accuracy is required in this step to maintain a uniformity of heater characteristics across the wafer. This is the main reason that the heater is not etched simultaneously with the other actuator layers. CD for the heater mask is 0.5 microns. Overlay accuracy is +/−0.1 microns. The bond pads are also covered with this layer of TiN. This is to prevent the bond pads being etched away during the sacrificial aluminum etch. It also prevents corrosion of the aluminum bond pads during operation. TiN is an excellent corrosion barrier for aluminum. The resistivity of TIN is low enough to not cause problems with the bond pad resistance. 
     Deposit 2 microns of PECVD glass. This is preferably done at around 350° C. to 400° C. to minimize intrinsic stress in the glass. Thermal stress could be reduced by a lower deposition temperature, however thermal stress is actually beneficial, as the glass is sandwiched between two layers of TiN. The TiN/glass/TiN tri-layer cancels bend due to thermal stress, and results in the glass being under constant compressive stress, which increases the efficiency of the actuator. 
     Deposit 0.9 microns of magnetron sputtered TiN. This layer is deposited to cancel bend from the differential thermal stress of the lower TiN and glass layers, and prevent the paddle from curling when released from the sacrificial materials. The deposition characteristics should be identical to the first TiN layer. 
     Anisotropically plasma etch the TIN and glass using actuator mask as shown in  FIG. 1061 . This mask defines the actuator and paddle. CD for the actuator mask is 1 micron. Overlay accuracy is +/−0.1 microns. The results of the etching process is illustrated in  FIG. 1062  with the glass layer  46250  sandwiched between TIN layers  46251 ,  46248 . Electrical testing can be performed by wafer probing at this time. All CMOS tests and heater functionality and resistance tests can be completed at wafer probe. 
     Deposit 15 microns of sacrificial material. There are many possible choices for this material. The essential requirements are the ability to deposit a 15 micron layer without excessive wafer warping, and a high etch selectivity to PECVD glass and TiN. Several possibilities are phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), polymers such as polyimide, and aluminum. Either a close CTE match to silicon (BPSG with the correct doping, filled polyimide) or a low Young&#39;s modulus (aluminum) is required. This example uses BPSG. Of these issues, stress is the most demanding due to the extreme layer thickness. BPSG normally has a CTE well below that of silicon, resulting in considerable compressive stress. However, the composition of BPSG can be varied significantly to adjust its CTE close to that of silicon. As the BPSG is a sacrificial layer, its electrical properties are not relevant, and compositions not normally suitable as a CMOS dielectric can be used. Low density, high porosity, and a high water content are all beneficial characteristics as they will increase the etch selectivity versus PECVD glass when using an anhydrous HF etch. 
     Etch the sacrificial layer to a depth of 2 microns using the nozzle mask as defined in  FIG. 1064  so as to form the structure  46254  illustrated in section in  FIG. 1065 . The mask of  FIG. 1064  defines all of the regions where a subsequently deposited overcoat is to be polished off using CMP. This includes the nozzles themselves, and various other fluid control features. CD for the nozzle mask is 2 microns. Overlay accuracy is +/−0.5 microns. 
     Anisotropically plasma etch the sacrificial layer down to the CMOS passivation layer using the chamber mask as illustrated in  FIG. 1067 . This mask defines the nozzle chamber and actuator shroud including slots  46255  as shown in  FIG. 1068 . CD for the chamber mask is 2 microns. Overlay accuracy is +/−0.2 microns. 
     Deposit 0.5 microns of fairly conformal overcoat material  46257  as illustrated in  FIG. 1070 . The electrical properties of this material are irrelevant, and it can be a conductor, insulator, or semiconductor. The material should be: chemically inert, strong, highly selective etch with respect to the sacrificial material, be suitable for CMP, and be suitable for conformal deposition at temperatures below 500° C. Suitable materials include: PECVD glass, MOCVD TiN, ECR CVD TiN, PECVD Si 3 N 4 , and many others. The choice for this example is PECVD TEOS glass. This must have a very low water content if BPSG is used as the sacrificial material and anhydrous HF is used as the sacrificial etchant, as the anhydrous HF etch relies on water content to achieve 1000:1 etch selectivity of BPSG over TEOS glass. The conformed overcoat  46257  forms a protective covering shell around the operational portions of the thermal bend actuator while permitting movement of the actuator within the shell. 
     Planarize the wafer to a depth of 1 micron using CMP as illustrated in  FIG. 1072 . The CMP processing should be maintained to an accuracy of +/−0.5 microns over the wafer surface. Dishing of the sacrificial material is not relevant. This opens the nozzles  46259  and fluid control regions e.g.  46260 . The rigidity of the sacrificial layer relative to the nozzle chamber structures during CMP is one of the key factors which may affect the choice of sacrificial materials. Turn the print head wafer over and securely mount the front surface on an oxidized silicon wafer blank  46262  illustrated in  FIG. 1074  having an oxidized surface  46263 . The mounting can be by way of glue  46265 . The blank wafers  46262  can be recycled. 
     Thin the print head wafer to 300 microns using backgrinding (or etch) and polish. The wafer thinning is performed to reduce the subsequent processing duration for deep silicon etching from around 5 hours to around 2.3 hours. The accuracy of the deep silicon etch is also improved, and the hard-mask thickness is halved to 2.5 microns. The wafers could be thinned further to improve etch duration and print head efficiency. The limitation to wafer thickness is the print head fragility after sacrificial BPSG etch. 
     Deposit a SiO 2  hard mask (2.5 microns of PECVD glass) on the backside of the wafer and pattern using the inlet mask as shown in  FIG. 1072 . The hard mask of  FIG. 1072  is used for the subsequent deep silicon etch, which is to a depth of 315 microns with a hard mask selectivity of 150:1. This mask defines the ink inlets, which are etched through the wafer. CD for the inlet mask is 4 microns. Overlay accuracy is +/−2 microns. The inlet mask is undersize by 5.25 microns on each side to allow for a reentrant etch angle of 91 degrees over a 300 micron etch depth. Lithography for this step uses a mask aligner instead of a stepper. Alignment is to patterns on the front of the wafer. Equipment is readily available to allow sub-micron front-to-back alignment. 
     Back-etch completely through the silicon wafer (using, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) through the previously deposited hard mask. The STS ASE is capable of etching highly accurate holes through the wafer with aspect ratios of 30:1 and sidewalls of 90 degrees. In this case, a re-entrant sidewall angle of 91 degrees is taken as nominal. A reentrant angle is chosen because the ASE performs better, with a higher etch rate for a given accuracy, with a slightly reentrant angle. Also, a re-entrant etch can be compensated by making the holes on the mask undersize. Non-re-entrant etch angles cannot be so easily compensated, because the mask holes would merge. The wafer is also preferably diced by this etch The final result is as illustrated in  FIG. 1074  including back etched ink channel portions  46264 . 
     Etch all exposed aluminum. Aluminum on all three layers is used as sacrificial layers in certain places. 
     Etch all of the sacrificial material. The nozzle chambers are cleared by this etch with the result being as shown in  FIG. 1076 . If BPSG is used as the sacrificial material, it can be removed without etching the CMOS glass layers or the actuator glass. This can be achieved with 1000:1 selectivity against undoped glass such as TEOS, using anhydrous HF at 1500 sccm in a N 2  atmosphere at 60° C. [L. Chang et al, “Anhydrous HF etch reduces processing steps for DRAM capacitors”,  Solid State Technology  Vol. 41 No. 5, pp 71-76, 1998]. The actuators are freed and the chips are separated from each other, and from the blank wafer, by this etch. If aluminum is used as the sacrificial layer instead of BPSG, then its removal is combined with the previous step, and this step is omitted. 
     Pick up the loose print heads with a vacuum probe, and mount the print heads in their packaging. This must be done carefully, as the unpackaged print heads are fragile. The front surface of the wafer is especially fragile, and should not be touched. This process should be performed manually, as it is difficult to automate. The package is a custom injection molded plastic housing incorporating ink channels that supply the appropriate color ink to the ink inlets at the back of the print head. The package also provides mechanical support to the print head. The package is especially designed to place minimal stress on the chip, and to distribute that stress evenly along the length of the package. The print head is glued into this package with a compliant sealant such as silicone. 
     Form the external connections to the print head chip. For a low profile connection with minimum disruption of airflow, tape automated bonding (TAB) may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper. All of the bond pads are along one 100 mm edge of the chip. There are a total of 504 bond pads, in 8 identical groups of 63 (as the chip is fabricated using 8 stitched stepper steps). Each bond pad is 100×100 micron, with a pitch of 200 micron. 256 of the bond pads are used to provide power and ground connections to the actuators, as the peak current is 6.58 Amps at 3V. There are a total of 40 signal connections to the entire print head (24 data and 16 control), which are mostly bussed to the eight identical sections of the print head. 
     Hydrophobize the front surface of the print heads. This can be achieved by the vacuum deposition of 50 nm or more of polytetrafluoroethylene (PTFE). However, there are also many other ways to achieve this. As the fluid is fully controlled by mechanical protuberances formed in previous steps, the hydrophobic layer is an ‘optional extra’ to prevent ink spreading on the surface if the print head becomes contaminated by dust. 
     Plug the print heads into their sockets. The socket provides power, data, and ink. The ink fills the print-head by capillarity. Allow the completed print heads to fill with ink, and test.  FIG. 1079  illustrates the filling of ink  46268  into the nozzle chamber. 
     Process Parameters used for this Implementation Example 
     The CMOS process parameters utilized can be varied to suit any CMOS process of 0.5 micron dimensions or better. The MEMS process parameters should not be varied beyond the tolerances shown below. Some of these parameters affect the actuator performance and fluidics, while others have more obscure relationships. For example, the wafer thin stage affects the cost and accuracy of the deep silicon etch, the thickness of the back-side hard mask, and the dimensions of the associated plastic ink channel molding. Suggested process parameters can be as follows: 
                                                     Parameter   Type   Min.   Nom.   Max.   Units   Tol.                                                            Wafer resistivity   CMOS   15   20   25   Ω cm   ±25%       Wafer thickness   CMOS   600   650   700   μm    ±8%       N-Well Junction   CMOS   2   2.5   3   μm   ±20%       depth       n+ Junction depth   CMOS   0.15   0.2   0.25   μm   ±25%       p+ Junction depth   CMOS   0.15   0.2   0.25   μm   ±25%       Field oxide   CMOS   0.45   0.5   0.55   μm   ±10%       thickness       Gate oxide thickness   CMOS   12   13   14   nm    ±7%       Poly thickness   CMOS   0.27   0.3   0.33   μm   ±10%       ILD 1 thickness   CMOS   0.5   0.6   0.7   μm   ±16%       (PECVD glass)       Metal 1 thickness   CMOS   0.55   0.6   0.65   μm    ±8%       (aluminum)       ILD 2 thickness   CMOS   0.6   0.7   0.8   μm   ±14%       (PECVD glass)       Metal 2 thickness   CMOS   0.55   0.6   0.65   μm    ±8%       (aluminum)       ILD 3 thickness   CMOS   0.6   0.7   0.8   μm   ±14%       (PECVD glass)       Metal 3 thickness   CMOS   0.9   1.0   1.1   μm   ±10%       (aluminum)       Overcoat (PECVD   CMOS   0.4   0.5   0.6   μm   ±20%       glass)       Passivation (Si 3 N 4)     CMOS   0.4   0.5   0.6   μm   ±20%       Heater thickness   MEMS   0.85   0.9   0.95   μm    ±5%       (TiN)       Actuator thickness   MEMS   1.9   2.0   2.1   μm    ±5%       (PECVD glass)       Bend compensator   MEMS   0.85   0.9   0.95   μm    ±5%       thickness (TiN)       Sacrificial layer   MEMS   13.5   15   16.5   μm   ±10%       thickness (low stress       BPSG)       Nozzle etch (BPSG)   MEMS   1.6   2.0   2.4   μm   ±20%       Nozzle chamber and   MEMS   0.3   0.5   0.7   μm   ±40%       shroud (PECVD       glass)       Nozzle CMP depth   MEMS   0.7   1   1.3   μm   ±30%       Wafer thin (back-   MEMS   295   300   305   μm   ±1.6%        grind and polish)       Back-etch hard   MEMS   2.25   2.5   2.75   μm   ±10%       mask (SiO 2 )       STS ASE back-etch   MEMS   305   325   345   μm    ±6%       (stop on aluminum)                    
Control Logic
 
     Turning over to  FIG. 1081 , there is illustrated the associated control logic for a single ink jet nozzle. The control logic  46280  is utilized to activate a heater element  46281  on demand. The control logic  46280  includes a shift register  46282 , a transfer register  46283  and a firing control gate  46284 . The basic operation is to shift data from one shift register  46282  to the next until it is in place. Subsequently, the data is transferred to a transfer register  46283  upon activation of a transfer enable signal  46286 . The data is latched in the transfer register  46283  and subsequently, a firing phase control signal  46289  is utilized to activate a gate  46284  for output of a heating pulse to heat an element  46281 . 
     As the preferred implementation utilizes a CMOS layer for implementation of all control circuitry, one form of suitable CMOS implementation of the control circuitry will now be described. Turning now to  FIG. 1082 , there is illustrated a schematic block diagram of the corresponding CMOS circuitry. Firstly, shift register  46282  takes an inverted data input and latches the input under control of shift clocking signals  46291 ,  46292 . The data input  46290  is output  46294  to the next shift register and is also latched by a transfer register  46283  under control of transfer enable signals  46296 ,  46297 . The enable gate  46284  is activated under the control of enable signal  46299  so as to drive a power transistor  46300  which allows for resistive heating of resistor  46281 . The functionality of the shift register  46282 , transfer register  46283  and enable gate  46284  are standard CMOS components well understood by those skilled in the art of CMOS circuit design. 
     Replicated Units 
     The ink jet print head can consist of a large number of replicated unit cells each of which has basically the same design. This design will now be discussed. 
     Turning initially to  FIG. 1083 , there is illustrated a general key or legend of different material layers utilized in subsequent discussions. 
       FIG. 1084  illustrates the unit cell  46305  on a 1 micron grid  46306 . The unit cell  46305  is copied and replicated a large number of times with  FIG. 1084  illustrating the diffusion and poly-layers in addition to vias e.g.  46308 . The signals  46290 ,  46291 ,  46292 ,  46296 ,  46297  and  46299  are as previously discussed with reference to  FIG. 1082 . A number of important aspects of  FIG. 1084  include the general layout including the shift register, transfer register and gate and drive transistor. Importantly, the drive transistor  46300  includes an upper poly-layer e.g.  46309  which is laid out having a large number of perpendicular traces e.g.  46312 . The perpendicular traces are important in ensuring that the corrugated nature of a heater element formed over the power transistor  46300  will have a corrugated bottom with corrugations running generally in the perpendicular direction of trace  46112 . This is best shown in  FIGS. 1074 ,  1076  and  1079 . Consideration of the nature and directions of the corrugations, which arise unavoidably due to the CMOS wiring underneath, is important to the ultimate operational efficiency of the actuator. In the ideal situation, the actuator is formed without corrugations by including a planarization step on the upper surface of the substrate step prior to forming the actuator. However, the best compromise that obviates the additional process step is to ensure that the corrugations extend in a direction that is transverse to the bending axis of the actuator as illustrated in the examples, and preferably constant along its length. This results in an actuator that may only be 2% less efficient than a flat actuator, which in many situations will be an acceptable result. By contrast, corrugations that extend longitudinally would reduce the efficiency by about 20% compared to a flat actuator. 
     In  FIG. 1085 , there is illustrated the addition of the first level metal layer which includes enable lines  46296 ,  46297 . 
     In  FIG. 1086 , there is illustrated the second level metal layer which includes data in-line  46290 , SClock line  46291 , SClock  46292 , Q  294 , TEn  46296  and TEn  46297 , V- 46320 , V DD    46321 , V SS    46322 , in addition reflected components  46323  to  46328 . The portions  46330  and  46331  are utilized as a sacrificial etch. 
     Turning now to  FIG. 1087  there is illustrated the third level metal layer which includes a portion  46340  which is utilized as a sacrificial etch layer underneath the heater actuator. The portion  46341  is utilized as part of the actuator structure with the portions  46342  and  46343  providing electrical interconnections. 
     Turning now to  FIG. 1088 , there is illustrated the planar conductive heating circuit layer including heater arms  46350  and  46351  which are interconnected to the lower layers. The heater arms are formed on either side of a tapered slot so that they are narrower toward the fixed or proximal end of the actuator arm, giving increased resistance and therefore heating and expansion in that region. The second portion of the heating circuit layer  46352  is electrically isolated from the arms  46350  and  46351  by a discontinuity  46355  and provides for structural support for the main paddle  46356 . The discontinuity may take any suitable form but is typically a narrow slot as shown at  46355 . 
     In  FIG. 1089  there is illustrated the portions of the shroud and nozzle layer including shroud  46353  and outer nozzle chamber  46354 . 
     Turning to  FIG. 1090 , there is illustrated a portion  46360  of a array of ink ejection nozzles which are divided into three groups  46361 - 46363  with each group providing separate color output (cyan, magenta and yellow) so as to provide full three color printing. A series of standard cell clock buffers and address decoders  46364  is also provided in addition to bond pads  46365  for interconnection with the external circuitry. 
     Each color group  46361 ,  46363  consists of two spaced apart rows of ink ejection nozzles e.g.  46367  each having a heater actuator element. 
       FIG. 1092  illustrates one form of overall layout in a cut away manner with a first area  46370  illustrating the layers up to the polysilicon level. A second area  46371  illustrating the layers up to the first level metal, the area  46372  illustrating the layers up to the second level metal and the area  46373  illustrating the layers up to the heater actuator layer. 
     The ink ejection nozzles are grouped in two groups of 10 nozzles sharing a common ink channel through the wafer. Turning to  FIG. 1093 , there is illustrated the back surface of the wafer which includes a series of ink supply channels  46380  for supplying ink to a front surface. 
     Replication 
     The unit cell is replicated 19,200 times on the 4″ print head, in the hierarchy as shown in the replication hierarchy table below. The layout grid is ½ l at 0.5 micron (0.125 micron). Many of the ideal transform distances fall exactly on a grid point. Where they do not, the distance is rounded to the nearest grid point. The rounded numbers are shown with an asterisk. The transforms are measured from the center of the corresponding nozzles in all cases. The transform of a group of five even nozzles into five odd nozzles also involves a 180° rotation. The translation for this step occurs from a position where all five pairs of nozzle centers are coincident 
                            Replication Hierarchy Table                                                                                 Y                                           X   Transform           Replication   Rotation   Replication   Total   Transform   Grid   Actual       Grid   Actual       Replication   Stage   (°)   Ratio   Nozzles   pixels   units   microns   Pixels   units   microns                                                                 0   Initial rotation   45   1:1   1   0      0   0   0   0   0       1   Even nozzles in   0   5:1   5   2     254   31.75     1/10   13*   1.625*           a pod       2   Odd nozzles in a   180   2:1   10   1     127   15.875   1 9/16   198*    24.75*           pod       3   Pods in a CMY   0   3:1   30   5½     699*   87.375*   7   889    111.125           tripod       4   Tripods per   0   10:1‘   300   10    1270   158.75   0   0   0           podgroup       5   Podgroups per   0   2:1   600   100    12700   1587.5   0   0   0           firegroup       6   Firegroups per   0   4:1   2400   200    25400   3175   0   0   0           segment       7   Segments per   0   8:1   19200   800   101600   12700   0   0   0           print head                    
Composition
 
     Taking the example of a 4-inch print head suitable for use in camera photoprinting as illustrated in  FIG. 1094 , a 4-inch print head  46380  consists of 8 segments eg.  46381 , each segment is ½ an inch in length. Consequently each of the segments prints bi-level cyan, magenta and yellow dots over a different part of the page to produce the final image. The positions of the 8 segments are shown in  FIG. 1094 . In this example, the print head is assumed to print dots at 1600 dpi, each dot is 15.875 microns in diameter. Thus each half-inch segment prints 800 dots, with the 8 segments corresponding to positions as illustrated in the following table: 
     
       
         
           
               
               
               
             
               
                   
               
               
                 Segment 
                 First dot 
                 Last dot 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 0 
                 0 
                 799 
               
               
                 1 
                 800 
                 1599 
               
               
                 2 
                 1600 
                 2399 
               
               
                 3 
                 2400 
                 3199 
               
               
                 4 
                 3200 
                 3999 
               
               
                 5 
                 4000 
                 4799 
               
               
                 6 
                 4800 
                 5599 
               
               
                 7 
                 5600 
                 6399 
               
               
                   
               
            
           
         
       
     
     Although each segment produces 800 dots of the final image, each dot is represented by a combination of bi-level cyan, magenta, and yellow ink. Because the printing is bi-level, the input image should be dithered or error-diffused for best results. 
     Each segment  46381  contains 2,400 nozzles: 800 each of cyan, magenta, and yellow. A four-inch print head contains 8 such segments for a total of 19,200 nozzles. 
     The nozzles within a single segment are grouped for reasons of physical stability as well as minimization of power consumption during printing. In terms of physical stability, as shown in  FIG. 1093  groups of 10 nozzles are grouped together and share the same ink channel reservoir. In terms of power consumption, the groupings are made so that only 96 nozzles are fired simultaneously from the entire print head. Since the 96 nozzles should be maximally distant, 12 nozzles are fired from each segment. To fire all 19,200 nozzles, 200 different sets of 96 nozzles must be fired. 
       FIG. 1095  shows schematically, a single pod  46395  which consists of 10 nozzles numbered 1 to 10 sharing a common ink channel supply. 5 nozzles are in one row, and 5 are in another. Each nozzle produces dots 15.875 μm in diameter. The nozzles are numbered according to the order in which they must be fired. 
     Although the nozzles are fired in this order, the relationship of nozzles and physical placement of dots on the printed page is different The nozzles from one row represent the even dots from one line on the page, and the nozzles on the other row represent the odd dots from the adjacent line on the page.  FIG. 1096  shows the same pod  46395  with the nozzles numbered according to the order in which they must be loaded. 
     The nozzles within a pod are therefore logically separated by the width of 1 dot. The exact distance between the nozzles will depend on the properties of the ink jet firing mechanism. In the best case, the print head could be designed with staggered nozzles designed to match the flow of paper. In the worst case there is an error of 1/3200 dpi. While this error would be viewable under a microscope for perfectly straight lines, it certainly will not be an apparent in a photographic image. 
     As shown in  FIG. 1097 , three pods representing Cyan  46398 , Magenta  46197 , and Yellow  46396  units, are grouped into a tripod  46400 . A tripod represents the same horizontal set of 10 dots, but on different lines. The exact distance between different color pods depends on the ink jet operating parameters, and may vary from one ink jet to another. The distance can be considered to be a constant number of dot-widths, and must therefore be taken into account when printing: the dots printed by the cyan nozzles will be for different lines than those printed by the magenta or yellow nozzles. The printing algorithm must allow for a variable distance up to about 8 dot-widths. 
     As illustrated in  FIG. 1098 , 10 tripods eg.  46404  are organized into a single podgroup  46405 . Since each tripod contains 30 nozzles, each podgroup contains 300 nozzles: 100 cyan, 100 magenta and 100 yellow nozzles. The arrangement is shown schematically in  FIG. 1098 , with tripods numbered 0-9. The distance between adjacent tripods is exaggerated for clarity. 
     As shown in  FIG. 1099 , two podgroups (PodgroupA  46410  and PodgroupB  46411 ) are organized into a single firegroup  46414 , with 4 firegroups in each segment  46415 . Each segment  46415  contains 4 firegroups. The distance between adjacent firegroups is exaggerated for clarity. 
                                         Name of Grouping   Composition   Replication Ratio   Nozzle Count                                                Nozzle   Base unit   1:1   1       Pod   Nozzles per   10:1    10           pod       Tripod   Pods per CMY   3:1   30           tripod       Podgroup   Tripods per   10:1    300           podgroup       Firegroup   Podgroups per   2:1   600           firegroup       Segment   Firegroups per   4:1   2,400           segment       Print head   Segments per   8:1   19,200           print head                    
Load and Print Cycles
 
     The print head contains a total of 19,200 nozzles. A Print Cycle involves the firing of up to all of these nozzles, dependent on the information to be printed. A Load Cycle involves the loading up of the print head with the information to be printed during the subsequent Print Cycle. 
     Each nozzle has an associated NozzleEnable ( 46289  of  FIG. 1081 ) bit that determines whether or not the nozzle will fire during the Print Cycle. The NozzleEnable bits (one per nozzle) are loaded via a set of shift registers. 
     Logically there are 3 shift registers per color, each 800 deep. As bits are shifted into the shift register they are directed to the lower and upper nozzles on alternate pulses. Internally, each 800-deep shift register is comprised of two 400-deep shift registers: one for the upper nozzles, and one for the lower nozzles. Alternate bits are shifted into the alternate internal registers. As far as the external interface is concerned however, there is a single 800 deep shift register. 
     Once all the shift registers have been fully loaded (800 pulses), all of the bits are transferred in parallel to the appropriate NozzleEnable bits. This equates to a single parallel transfer of 19,200 bits. Once the transfer has taken place, the Print Cycle can begin. The Print Cycle and the Load Cycle can occur simultaneously as long as the parallel load of all NozzleEnable bits occurs at the end of the Print Cycle. 
     In order to print a 6″×4″ image at 1600 dpi in say 2 seconds, the 4″ print head must print 9,600 lines (6×1600). Rounding up to 10,000 lines in 2 seconds yields a line time of 200 microseconds. A single Print Cycle and a single Load Cycle must both finish within this time. In addition, a physical process external to the print head must move the paper an appropriate amount. 
     Load Cycle 
     The Load Cycle is concerned with loading the print head&#39;s shift registers with the next Print Cycle&#39;s NozzleEnable bits. 
     Each segment has 3 inputs directly related to the cyan, magenta, and yellow pairs of shift registers. These inputs are called CDataIn, MDataIn, and YDataIn. Since there are 8 segments, there are a total of 24 color input lines per print head. A single pulse on the SRClock line (shared between all 8 segments) transfers 24 bits into the appropriate shift registers. Alternate pulses transfer bits to the lower and upper nozzles respectively. Since there are 19,200 nozzles, a total of 800 pulses are required for the transfer. Once all 19,200 bits have been transferred, a single pulse on the shared PTransfer line causes the parallel transfer of data from the shift registers to the appropriate NozzleEnable bits. The parallel transfer via a pulse on PTransfer must take place after the Print Cycle has finished. Otherwise the NozzleEnable bits for the line being printed will be incorrect. 
     Since all 8 segments are loaded with a single SRClock pulse, the printing software must produce the data in the correct sequence for the print head. As an example, the first SRClock pulse will transfer the C, M, and Y bits for the next Print Cycle&#39;s dot 0, 800, 1600, 2400, 3200, 4000, 4800, and 5600. The second SRClock pulse will transfer the C, M, and Y bits for the next Print Cycle&#39;s dot 1, 801, 1601, 2401, 3201, 4001, 4801 and 5601. After 800 SRClock pulses, the PTransfer pulse can be given. 
     It is important to note that the odd and even C, M, and Y outputs, although printed during the same Print Cycle, do not appear on the same physical output line. The physical separation of odd and even nozzles within the print head, as well as separation between nozzles of different colors ensures that they will produce dots on different lines of the page. This relative difference must be accounted for when loading the data into the print head. The actual difference in lines depends on the characteristics of the ink jet used in the print head. The differences can be defined by variables D 1  and D 2  where D 1  is the distance between nozzles of different colors (likely value 4 to 8), and D 2  is the distance between nozzles of the same color (likely value=1). Table 3 shows the dots transferred to segment n of a print head on the first 4 pulses. 
     
       
         
           
               
               
               
               
            
               
                   
                   
               
               
                   
                 Yellow 
                 Magenta 
                 Cyan 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Pulse 
                 Line 
                 Dot 
                 Line 
                 Dot 
                 Line 
                 Dot 
               
               
                   
               
               
                 1 
                 N 
                 800S 
                 N + D 1   
                 800S 
                 N + 
                 800S 
               
               
                   
                   
                   
                   
                   
                 2D1 
               
               
                 2 
                 N + 
                 800S + 1 
                 N + D 1  + D 2   
                 800S + 1 
                 N + 
                 800S + 1 
               
               
                   
                 D 2   
                   
                   
                   
                 2D 1  + 
               
               
                   
                   
                   
                   
                   
                 D 2   
               
               
                 3 
                 N 
                 800S + 2 
                 N + D 1   
                 800S + 2 
                 N + 
                 800S + 2 
               
               
                   
                   
                   
                   
                   
                 2D 1   
               
               
                 4 
                 N + 
                 800S + 3 
                 N + D 1  + D 2   
                 800S + 3 
                 N + 
                 800S + 3 
               
               
                   
                 D 2   
                   
                   
                   
                 2D 1  + 
               
               
                   
                   
                   
                   
                   
                 D 2   
               
               
                   
               
            
           
         
       
     
     And so on for all 800 pulses. The 800 SRClock pulses (each clock pulse transferring 24 bits) must take place within the 200 microseconds line time. Therefore the average time to calculate the bit value for each of the 19,200 nozzles must not exceed 200 microseconds/19200=10 nanoseconds. Data can be clocked into the print head at a maximum rate of 10 MHz, which will load the data in 80 microseconds. Clocking the data in at 4 MHz will load the data in 200 microseconds. 
     Print Cycle 
     The print head contains 19,200 nozzles. To fire them all at once would consume too much power and be problematic in terms of ink refill and nozzle interference. A single print cycle therefore consists of 200 different phases. 96 maximally distant nozzles are fired in each phase, for a total of 19,200 nozzles.
         4 bits TripodSelect (select 1 of 10 tripods from a firegroup)       

     The 96 nozzles fired each round equate to 12 per segment (since all segments are wired up to accept the same print signals). The 12 nozzles from a given segment come equally from each firegroup. Since there are 4 firegroups, 3 nozzles fire from each firegroup. The 3 nozzles are one per color. The nozzles are determined by:
         4 bits NozzleSelect (select 1 of 10 nozzles from a pod)       

     The duration of the firing pulse is given by the AEnable and BEnable lines, which fire the PodgroupA and PodgroupB nozzles from all firegroups respectively. The duration of a pulse depends on the viscosity of the ink (dependent on temperature and ink characteristics) and the amount of power available to the print head. The AEnable and BEnable are separate lines in order that the firing pulses can overlap. Thus the 200 phases of a Print Cycle consist of 100 A phases and 100 B phases, effectively giving 100 sets of Phase A and Phase B. 
     When a nozzle fires, it takes approximately 100 microseconds to refill. This is not a problem since the entire Print Cycle takes 200 microseconds. The firing of a nozzle also causes perturbations for a limited time within the common ink channel of that nozzle&#39;s pod. The perturbations can interfere with the firing of another nozzle within the same pod. Consequently, the firing of nozzles within a pod should be offset by at least this amount The procedure is to therefore fire three nozzles from a tripod (one nozzle per color) and then move onto the next tripod within the podgroup. Since there are 10 tripods in a given podgroup, 9 subsequent tripods must fire before the original tripod must fire its next three nozzles. The 9 firing intervals of 2 microseconds gives an ink settling time of 18 microseconds. 
     Consequently, the firing order is:
         TripodSelect 0, NozzleSelect 0 (Phases A and B)   TripodSelect 1, NozzleSelect 0 (Phases A and B)   TripodSelect 2, NozzleSelect 0 (Phases A and B)   . . .   TripodSelect 9, NozzleSelect 0 (Phases A and B)   TripodSelect 0, NozzleSelect 1 (Phases A and B)   TripodSelect 1, NozzleSelect 1 (Phases A and B)   TripodSelect 2, NozzleSelect I (Phases A and B)   . . .   TripodSelect 8, NozzleSelect 9 (Phases A and B)   TripodSelect 9, NozzleSelect 9 (Phases A and B)       

     Note that phases A and B can overlap. The duration of a pulse will also vary due to battery power and ink viscosity (which changes with temperature).  FIG. 1100  shows the AEnable and BEnable lines during a typical Print Cycle. 
     Feedback from the Print Head 
     The print head produces several lines of feedback (accumulated from the 8 segments). The feedback lines can be used to adjust the timing of the firing pulses. Although each segment produces the same feedback, the feedback from all segments share the same tri-state bus lines. Consequently only one segment at a time can provide feedback. A pulse on the SenseEnable line ANDed with data on CYAN enables the sense lines for that segment The feedback sense lines are as follows:
         Tsense informs the controller how hot the print head is. This allows the controller to adjust timing of firing pulses, since temperature affects the viscosity of the ink.   Vsense informs the controller how much voltage is available to the actuator. This allows the controller to compensate for a flat battery or high voltage source by adjusting the pulse width.   Rsense informs the controller of the resistivity (Ohms per square) of the actuator heater. This allows the controller to adjust the pulse widths to maintain a constant energy irrespective of the heater resistivity.   Wsense informs the controller of the width of the critical part of the heater, which may vary up to ±5% due to lithographic and etching variations. This allows the controller to adjust the pulse width appropriately.
 
Preheat Mode
       

     The printing process has a strong tendency to stay at the equilibrium temperature. To ensure that the first section of the printed photograph has a consistent dot size, ideally the equilibrium temperature should be met before printing any dots. This is accomplished via a preheat mode. 
     The Preheat mode involves a single Load Cycle to all nozzles with Is (i.e. setting all nozzles to fire), and a number of short firing pulses to each nozzle. The duration of the pulse must be insufficient to fire the drops, but enough to heat up the ink surrounding the heaters. Altogether about 200 pulses for each nozzle are required, cycling through in the same sequence as a standard Print Cycle. 
     Feedback during the Preheat mode is provided by Tsense, and continues until an equilibrium temperature is reached (about 30° C. above ambient). The duration of the Preheat mode can be around 50 milliseconds, and can be tuned in accordance with the ink composition. 
     Print Head Interface Summary 
     The print head has the following connections: 
     
       
         
           
               
               
               
             
               
                   
               
               
                 Name 
                 #Pins 
                 Description 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Tripod Select 
                 4 
                 Select which tripod will fire (0-9) 
               
               
                 NozzleSelect 
                 4 
                 Select which nozzle from the pod will fire 
               
               
                   
                   
                 (0-9) 
               
               
                 AEnable 
                 1 
                 Firing pulse for podgroup A 
               
               
                 BEnable 
                 1 
                 Firing pulse for podgroup B 
               
               
                 CDataIn[0-7] 
                 8 
                 Cyan input to cyan shift register of segments 
               
               
                   
                   
                 0-7 
               
               
                 MDataIn[0-7] 
                 8 
                 Magenta input to magenta shift register of 
               
               
                   
                   
                 segments 0-7 
               
               
                 YDataIn[0-7] 
                 8 
                 Yellow input to yellow shift register of 
               
               
                   
                   
                 segments 0-7 
               
               
                 SRClock 
                 1 
                 A pulse on SRClock (ShiftRegisterClock) 
               
               
                   
                   
                 loads the current values from CDataIn[0-7], 
               
               
                   
                   
                 MdataIn[0-7] and YDataIn[0-CDataIn[0-7], 
               
               
                   
                   
                 MDataIn[0-7] and YDataIn[0-7] into the 
               
               
                   
                   
                 24 shift registers. 
               
               
                 PTransfer 
                 1 
                 Parallel transfer of data from the shift 
               
               
                   
                   
                 registers to the internal NozzleEnable bits 
               
               
                   
                   
                 (one per nozzle). 
               
               
                 SenseEnable 
                 1 
                 A pulse on SenseEnable ANDed with data 
               
               
                   
                   
                 on CDataIn[n] enables the sense lines for 
               
               
                   
                   
                 segment n. 
               
               
                 Tsense 
                 1 
                 Temperature sense 
               
               
                 Vsense 
                 1 
                 Voltage sense 
               
               
                 Rsense 
                 1 
                 Resistivity sense 
               
               
                 Wsense 
                 1 
                 Width sense 
               
               
                 Logic GND 
                 1 
                 Logic ground 
               
               
                 Logic PWR 
                 1 
                 Logic power 
               
               
                 V- 
                 Bus bars 
               
               
                 V+ 
               
               
                 TOTAL 
                 43 
               
               
                   
               
            
           
         
       
     
     Internal to the print head, each segment has the following connections to the bond pads: 
     Pad Connections 
     Although an entire print head has a total of 504 connections, the mask layout contains only 63. This is because the chip is composed of eight identical and separate sections, each 12.7 micron long. Each of these sections has 63 pads at a pitch of 200 microns. There is an extra 50 microns at each end of the group of 63 pads, resulting in an exact repeat distance of 12,700 microns (12.7 micron, ½″) Pads 
     
       
         
           
               
               
               
             
               
                   
               
               
                 No. 
                 Name 
                 Function 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 1 
                 V− 
                 Negative actuator supply 
               
               
                 2 
                 V ss   
                 Negative drive logic supply 
               
               
                 3 
                 V+ 
                 Positive actuator supply 
               
               
                 4 
                 V dd   
                 Positive drive logic supply 
               
               
                 5 
                 V− 
                 Negative actuator supply 
               
               
                 6 
                 SClk 
                 Serial data transfer clock 
               
               
                 7 
                 V+ 
                 Positive actuator supply 
               
               
                 8 
                 TEn 
                 Parallel transfer enable 
               
               
                 9 
                 V− 
                 Negative actuator supply 
               
               
                 10 
                 EPEn 
                 Even phase enable 
               
               
                 11 
                 V+ 
                 Positive actuator supply 
               
               
                 12 
                 OPEn 
                 Odd phase enable 
               
               
                 13 
                 V− 
                 Negative actuator supply 
               
               
                 14 
                 NA[0] 
                 Nozzle Address [0] (in pod) 
               
               
                 15 
                 V+ 
                 Positive actuator supply 
               
               
                 16 
                 NA[1] 
                 Nozzle Address [1] (in pod) 
               
               
                 17 
                 V− 
                 Negative actuator supply 
               
               
                 18 
                 NA[2] 
                 Nozzle Address [2] (in pod) 
               
               
                 19 
                 V+ 
                 Positive actuator supply 
               
               
                 20 
                 NA[3] 
                 Nozzle Address [3] (in pod) 
               
               
                 21 
                 V− 
                 Negative actuator supply 
               
               
                 22 
                 PA[0] 
                 Pod Address [0] (1 of 10) 
               
               
                 23 
                 V+ 
                 Positive actuator supply 
               
               
                 24 
                 PA[1] 
                 Pod Address [1] (1 of 10) 
               
               
                 25 
                 V− 
                 Negative actuator supply 
               
               
                 26 
                 PA[2] 
                 Pod Address [2] (1 of 10) 
               
               
                 27 
                 V+ 
                 Positive actuator supply 
               
               
                 28 
                 PA[3] 
                 Pod Address [3] (1 of 10) 
               
               
                 29 
                 V− 
                 Negative actuator supply 
               
               
                 30 
                 PGA[0] 
                 Podgroup Address [0] 
               
               
                 31 
                 V+ 
                 Positive actuator supply 
               
               
                 32 
                 FGA[0] 
                 Firegroup Address [0] 
               
               
                 33 
                 V− 
                 Negative actuator supply 
               
               
                 34 
                 FGA[1] 
                 Firegroup Address [1] 
               
               
                 35 
                 V+ 
                 Positive actuator supply 
               
               
                 36 
                 SEn 
                 Sense Enable 
               
               
                 37 
                 V− 
                 Negative actuator supply 
               
               
                 38 
                 Tsense 
                 Temperature sense 
               
               
                 39 
                 V+ 
                 Positive actuator supply 
               
               
                 40 
                 Rsense 
                 Actuator resistivity sense 
               
               
                 41 
                 V− 
                 Negative actuator supply 
               
               
                 42 
                 Wsense 
                 Actuator width sense 
               
               
                 43 
                 V+ 
                 Positive actuator supply 
               
               
                 44 
                 Vsense 
                 Power supply voltage sense 
               
               
                 45 
                 V− 
                 Negative actuator supply 
               
               
                 46 
                 N/C 
                 Spare 
               
               
                 47 
                 V+ 
                 Positive actuator supply 
               
               
                 48 
                 D[C] 
                 Cyan serial data in 
               
               
                 49 
                 V− 
                 Negative actuator supply 
               
               
                 50 
                 D[M} 
                 Magenta serial data in 
               
               
                 51 
                 V+ 
                 Positive actuator supply 
               
               
                 52 
                 D[Y] 
                 Yellow serial data in 
               
               
                 53 
                 V− 
                 Negative actuator supply 
               
               
                 54 
                 Q[C] 
                 Cyan data out (for testing) 
               
               
                 55 
                 V+ 
                 Positive actuator supply 
               
               
                 56 
                 Q[M} 
                 Magenta data out (for testing) 
               
               
                 57 
                 V− 
                 Negative actuator supply 
               
               
                 58 
                 Q[Y] 
                 Yellow data out (for testing) 
               
               
                 59 
                 V+ 
                 Positive actuator supply 
               
               
                 60 
                 V ss   
                 Negative drive logic supply 
               
               
                 61 
                 V− 
                 Negative actuator supply 
               
               
                 62 
                 V dd   
                 Positive drive logic supply 
               
               
                 63 
                 V+ 
                 Positive actuator supply 
               
               
                   
               
            
           
         
       
     
                            Fabrication and Operational Tolerances                                             Cause of                           Parameter   variation   Compensation   Min.   Nom.   Max.   Units                                                 Ambient Temperature   Environmental   Real-time   −10   25   50   ° C.       Nozzle Radius   Lithographic   Brightness adjust   5.3   5.5   5.7   micron       Nozzle Length   Processing   Brightness adjust   0.5   1.0   1.5   micron       Nozzle Tip Contact Angle   Processing   Brightness adjust   100   110   120   °       Paddle Radius   Lithographic   Brightness adjust   9.8   10.0   10.2   micron       Paddle-Chamber Gap   Lithographic   Brightness adjust   0.8   1.0   1.2   micron       Chamber Radius   Lithographic   Brightness adjust   10.8   11.0   11.2   micron       Inlet Area   Lithographic   Brightness adjust   5500   6000   6500   micron 2         Inlet Length   Processing   Brightness adjust   295   300   305   micron       Inlet etch angle (re-entrant)   Processing   Brightness adjust   90.5   91   91.5   degrees       Heater Thickness   Processing   Real-time   0.95   1.0   1.05   micron       Heater Resistivity   Materials   Real-time   115   135   160   μΩ-cm       Heater Young&#39;s Modulus   Materials   Mask design   400   600   650   GPa       Heater Density   Materials   Mask design   5400   5450   5500   kg/m 3         Heater CTE   Materials   Mask design   9.2   9.4   9.6   10 −6 /° C.       Heater Width   Lithographic   Real-time   1.15   1.25   1.35   micron       Heater Length   Lithographic   Real-time   27.9   28.0   28.1   micron       Actuator Glass Thickness   Processing   Brightness adjust   1.9   2.0   2.1   micron       Glass Young&#39;s Modulus   Materials   Mask design   60   75   90   GPa       Glass CTE   Materials   Mask design   0.0   0.5   1.0   10 −6 /° C.       Actuator Wall Angle   Processing   Mask design   85   90   95   degrees       Actuator to Substrate Gap   Processing   None required   0.9   1.0   1.1   micron       Bend Cancelling Layer   Processing   Brightness adjust   0.95   1.0   1.05   micron       Lever Arm Length   Lithographic   Brightness adjust   87.9   88.0   88.1   micron       Chamber Height   Processing   Brightness adjust   10   11.5   13   micron       Chamber Wall Angle   Processing   Brightness adjust   85   90   95   degrees       Color Related Ink Viscosity   Materials   Mask design   −20   Nom.   +20   %       Ink Surface tension   Materials   Programmed   25   35   65   mN/m       Ink Viscosity @ 25° C.   Materials   Programmed   0.7   2.5   15   cP       Ink Dye Concentration   Materials   Programmed   5   10   15   %       Ink Temperature (relative)   Operation   None   −10   0   +10   ° C.       Ink Pressure   Operation   Programmed   −10   0   +10   kPa       Ink Drying   Materials   Programmed   +0   +2   +5   cP       Actuator Voltage   Operation   Real-time   2.75   2.8   2.85   V       Drive Pulse Width   Xtal Osc.   None required   1.299   1.300   1.301   microsec       Drive Transistor Resistance   Processing   Real-time   3.6   4.1   4.6   W       Fabrication Temp. (TiN)   Processing   Correct by design   300   350   400   ° C.       Battery Voltage   Operation   Real-time   2.5   3.0   3.5   V                    
Variation with Ambient Temperature
 
     The main consequence of a change in ambient temperature is that the ink viscosity and surface tension changes. As the bend actuator responds only to differential temperature between the actuator layer and the bend compensation layer, ambient temperature has negligible direct effect on the bend actuator. The resistivity of the TiN heater changes only slightly with temperature. The following simulations are for an water based ink, in the temperature range 0° C. to 80° C. 
     The drop velocity and drop volume does not increase monotonically with increasing temperature as one may expect. This is simply explained: as the temperature increases, the viscosity falls faster than the surface tension falls. As the viscosity falls, the movement of ink out of the nozzle is made slightly easier. However, the movement of the ink around the paddle—from the high pressure zone at the paddle front to the low pressure zone behind the paddle—changes even more. Thus more of the ink movement is ‘short circuited’ at higher temperatures and lower viscosities. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                   
               
             
            
               
                 Ambient 
                 Ink 
                 Surface 
                 Actuator 
                 Actuator 
                 Actuator 
                 Pulse 
                 Pulse 
                 Pulse 
               
               
                 Temperature 
                 Viscosity 
                 Tension 
                 Width 
                 Thickness 
                 Length 
                 Voltage 
                 Current 
                 Width 
               
               
                 ° C. 
                 cP 
                 dyne 
                 μm 
                 μm 
                 μm 
                 V 
                 mA 
                 μs 
               
               
                   
               
               
                  0 
                 1.79 
                 38.6 
                 1.25 
                 1.0 
                 27 
                 2.8 
                 42.47 
                 1.6 
               
               
                 20 
                 1.00 
                 35.8 
                 1.25 
                 1.0 
                 27 
                 2.8 
                 42.47 
                 1.6 
               
               
                 40 
                 0.65 
                 32.6 
                 1.25 
                 1.0 
                 27 
                 2.8 
                 42.47 
                 1.6 
               
               
                 60 
                 0.47 
                 29.2 
                 1.25 
                 1.0 
                 27 
                 2.8 
                 42.47 
                 1.6 
               
               
                 80 
                 0.35 
                 25.6 
                 1.25 
                 1.0 
                 27 
                 2.8 
                 42.47 
                 1.6 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Ambient 
                 Pulse 
                 Peak 
                 Paddle 
                 Paddle 
                 Drop 
                 Drop 
               
               
                   
                 Temperature 
                 Energy 
                 Temperature 
                 Deflection 
                 Velocity 
                 Velocity 
                 Volume 
               
               
                   
                 ° C. 
                 nJ 
                 ° C. 
                 μm 
                 m/s 
                 m/s 
                 pl 
               
               
                   
                   
               
               
                   
                  0 
                 190 
                 465 
                 3.16 
                 2.06 
                 2.82 
                 0.80 
               
               
                   
                 20 
                 190 
                 485 
                 3.14 
                 2.13 
                 3.10 
                 0.88 
               
               
                   
                 40 
                 190 
                 505 
                 3.19 
                 2.23 
                 3.25 
                 0.93 
               
               
                   
                 60 
                 190 
                 525 
                 3.13 
                 2.17 
                 3.40 
                 0.78 
               
               
                   
                 80 
                 190 
                 545 
                 3.24 
                 2.31 
                 3.31 
                 0.88 
               
               
                   
                   
               
            
           
         
       
     
     The temperature of the IJ46 print head is regulated to optimize the consistency of drop volume and drop velocity. The temperature is sensed on chip for each segment. The temperature sense signal (Tsense) is connected to a common Tsense output. The appropriate Tsense signal is selected by asserting the Sense Enable (Sen) and selecting the appropriate segment using the D[C 0-7 ] lines. The Tsense signal is digitized by the drive ASIC, and drive pulse width is altered to compensate for the ink viscosity change. Data specifying the viscosity/temperature relationship of the ink is stored in the Authentication chip associated with the ink. 
     Variation with Nozzle Radius 
     The nozzle radius has a significant effect on the drop volume and drop velocity. For this reason it is closely controlled by 0.5 micron lithography. The nozzle is formed by a 2 micron etch of the sacrificial material, followed by deposition of the nozzle wall material and a CMP step. The CMP planarizes the nozzle structures, removing the top of the overcoat, and exposed the sacrificial material inside. The sacrificial material is subsequently removed, leaving a self-aligned nozzle and nozzle rim. The accuracy internal radius of the nozzle is primarily determined by the accuracy of the lithography, and the consistency of the sidewall angle of the 2 micron etch. 
     The following table shows operation at various nozzle radii. With increasing nozzle radius, the drop velocity steadily decreases. However, the drop volume peaks at around a 5.5 micron radius. The nominal nozzle radius is 5.5 microns, and the operating tolerance specification allows a +/−4% variation on the radius, giving a range of 5.3 to 5.7 microns. The simulations also include extremes outside of the nominal operating range (5.0 and 6.0 micron). The major nozzle radius variations will likely be determined by a combination of the sacrificial nozzle etch and the CMP step. This means that variations are likely to be non-local: differences between wafers, and differences between the center and the perimeter of a wafer. The between wafer differences are compensated by the ‘brightness’ adjustment. Within wafer variations will be imperceptible as long as they are not sudden. 
                                                                Nozzle   Ink   Surface   Actuator   Actuator   Pulse   Pulse   Pulse   Pulse       Radius   Viscosity   Tension   Width   Length   Voltage   Current   Width   Energy       μm   cP   mN/m   μm   μm   V   mA   μs   nJ               5.0   0.65   32.6   1.25   25   2.8   42.36   1.4   166       5.3   0.65   32.6   1.25   25   2.8   42.36   1.4   166       5.5   0.65   32.6   1.25   25   2.8   42.36   1.4   166       5.7   0.65   32.6   1.25   25   2.8   42.36   1.4   166       6.0   0.65   32.6   1.25   25   2.8   42.36   1.4   166                                                         Nozzle   Peak   Peak   Paddle   Paddle   Drop   Drop           Radius   Temperature   Pressure   Deflection   Velocity   Velocity   Volume           μm   ° C.   kPa   μm   m/s   m/s   pl                       5.0   482   75.9   2.81   2.18   4.36   0.84           5.3   482   69.0   2.88   2.22   3.92   0.87           5.5   482   67.2   2.96   2.29   3.45   0.99           5.7   482   64.1   3.00   2.33   3.09   0.95           6.0   482   59.9   3.07   2.39   2.75   0.89                        
Ink Supply System
 
     A print head constructed in accordance with the aforementioned techniques can be utilized in a print camera system similar to that disclosed in PCT patent application No. PCT/AU98/00544. A print head and ink supply arrangement suitable for utilization in a print on demand camera system will now be described. Starting initially with  FIG. 1101  and  FIG. 1102 , there is illustrated portions of an ink supply arrangement in the form of an ink supply unit  46430 . The supply unit can be configured to include three ink storage chambers  46521  to supply three color inks to the back surface of a print head, which in the preferred form is a print head chip  46431 . The ink is supplied to the print head by means of an ink distribution molding or manifold  46433  which includes a series of slots e.g.  434  for the flow of ink via closely toleranced ink outlets  46432  to the back of the print head  46431 . The outlets  46432  are very small having a width of about 100 microns and accordingly need to be made to a much higher degree of accuracy than the adjacent interacting components of the ink supply unit such as the housing  46495  described hereafter. 
     The print head  44631  is of an elongate structure and can be attached to the print head aperture  46435  in the ink distribution manifold by means of silicone gel or a like resilient adhesive  46520 . 
     Preferably, the print head is attached along its back surface  46438  and sides  46439  by applying adhesive to the internal sides of the print head aperture  46435 . In this manner the adhesive is applied only to the interconnecting faces of the aperture and print head, and the risk of blocking the accurate ink supply passages  46380  formed in the back of the print head chip  46431  (see  FIG. 1093 ) is minimised. A filter  46436  is also provided that is designed to fit around the distribution molding  46433  so as to filter the ink passing through the molding  46433 . 
     Ink distribution molding  46433  and filter  46436  are in turn inserted within a baffle unit  46437  which is again attached by means of a silicone sealant applied at interface  46438 , such that ink is able to, for example, flow through the holes  46440  and in turn through the holes  46434 . The baffles  437  can be a plastic injection molded unit which includes a number of spaced apart baffles or slats  46441 - 46443 . The baffles are formed within each ink channel so as to reduce acceleration of the ink in the storage chambers  46521  as may be induced by movement of the portable printer, which in this preferred form would be most disruptive along the longitudinal extent of the print head, whilst simultaneously allowing for flows of ink to the print head in response to active demand therefrom. The baffles are effective in providing for portable carriage of the ink so as to minimize disruption to flow fluctuations during handling. 
     The baffle unit  46437  is in turn encased in a housing  46445 . The housing  46445  can be ultrasonically welded to the baffle member  46437  so as to seal the baffle member  46437  into three separate ink chambers  46521 . The baffle member  46437  further includes a series of pierceable end wall portions  46450 - 46452  which can be pierced by a corresponding mating ink supply conduit for the flow of ink into each of the three chambers. The housing  46445  also includes a series of holes  46455  which are hydrophobically sealed by means of tape or the like so as to allow air within the three chambers of the baffle units to escape whilst ink remains within the baffle chambers due to the hydrophobic nature of the holes eg.  46455 . 
     By manufacturing the ink distribution unit in separate interacting components as just described, it is possible to use relatively conventional molding techniques, despite the high degree of accuracy required at the interface with the print head. That is because the dimensional accuracy requirements are broken down in stages by using successively smaller components with only the smallest final member being the ink distribution manifold or second member needing to be produced to the narrower tolerances needed for accurate interaction with the ink supply passages  46380  formed in the chip. 
     The housing  46445  includes a series of positioning protuberances eg.  46460 - 46462 . A first series of protuberances is designed to accurately position interconnect means in the form of a tape automated bonded film  46470 , in addition to first  46465  and second  46466  power and ground busbars which are interconnected to the TAB film  46470  at a large number of locations along the surface of the TAB film so as to provide for low resistance power and ground distribution along the surface of the TAB film  46470  which is in turn interconnected to the print head chip  46431 . 
     The TAB film  46470 , which is shown in more detail in an opened state in  FIGS. 1107 and 1108 , is double sided having on its outer side a data/signal bus in the form of a plurality of longitudinally extending control line interconnects  46550  which releasably connect with a corresponding plurality of external control lines. Also provided on the outer side are busbar contacts in the form of deposited noble metal strips  46552 . 
     The inner side of the TAB film  46470  has a plurality of transversely extending connecting lines  46553  that alternately connect the power supply via the busbars and the control lines  46550  to bond pads on the print head via region  46554 . The connection with the control lines occurring by means of vias  46556  that extend through the TAB film. One of the many advantages of using the TAB film is providing a flexible means of connecting the rigid busbar rails to the fragile print head chip  46431 . 
     The busbars  46465 ,  46466  are in turn connected to contacts  46475 ,  46476  which are firmly clamped against the busbars  46465 , 46466  by means of cover unit  46478 . The cover unit  46478  also can comprise an injection molded part and includes a slot  480  for the insertion of an aluminum bar for assisting in cutting a printed page. 
     Turning now to  FIG. 1103  there is illustrated a cut away view of the print head unit  46430 , associated platen unit  46490 , print roll and ink supply unit  46491  and drive power distribution unit  46492  which interconnects each of the units  46430 , 46490  and  46491 . 
     The guillotine blade  46495  is able to be driven by a first motor along the aluminum blade  46498  so as to cut a picture  46499  after printing has occurred. The operation of the system of  FIG. 1103  is very similar to that disclosed in PCT patent application PCT/AU98/00544. Ink is stored in the core portion  46500  of a print roll former  46501  around which is rolled print media  46502 . The print media is fed under the control of electric motor  46494  between the platen  46290  and print head unit  46490  with the ink being interconnected via ink transmission channels  46505  to the print head unit  46430 . The print roll unit  46491  can be as described in the aforementioned PCT specification. In  FIG. 1104 , there is illustrated the assembled form of single printer unit  46510 . 
     Features and Advantages 
     The IJ46 print head has many features and advantages over other printing technologies. In some cases, these advantages stem from new capabilities. In other cases, the advantages stem from the avoidance of problems inherent in prior art technologies. A discussion of some of these advantages follows. 
     High Resolution 
     The resolution of a IJ46 print head is 1,600 dots per inch (dpi) in both the scan direction and transverse to the scan direction. This allows full photographic quality color images, and high quality text (including Kanji). Higher resolutions are possible: 2,400 dpi and 4,800 dpi versions have been investigated for special applications, but 1,600 dpi is chosen as ideal for most applications. The true resolution of advanced commercial piezoelectric devices is around 120 dpi and thermal ink jet devices around 600 dpi. 
     Excellent Image Quality 
     High image quality requires high resolution and accurate placement of drops. The monolithic page width nature of IJ46 print heads allows drop placement to sub-micron precision. High accuracy is also achieved by eliminating misdirected drops, electrostatic deflection, air turbulence, and eddies, and maintaining highly consistent drop volume and velocity. Image quality is also ensured by the provision of sufficient resolution to avoid requiring multiple ink densities. Five color or 6 color ‘photo’ ink jet systems can introduce halftoning artifacts in mid tones (such as flesh-tones) if the dye interaction and drop sizes are not absolutely perfect. This problem is eliminated in binary three color systems such as used in IJ46 print heads. 
     High Speed (30 ppm per Print Head) 
     The page width nature of the print head allows high-speed operation, as no scanning is required. The time to print a full color A4 page is less than 2 seconds, allowing full 30 page per minute (ppm) operation per print head. Multiple print heads can be used in parallel to obtain 60 ppm, 90 ppm, 120 ppm, etc. IJ46 print heads are low cost an compact, so multiple head designs are practical. 
     Low Cost 
     As the nozzle packing density of the IJ46 print head is very high, the chip area per print head can be low. This leads to a low manufacturing cost as many print head chips can fit on the same wafer. 
     All Digital Operation 
     The high resolution of the print head is chosen to allow fully digital operation using digital halftoning. This eliminates color non-linearity (a problem with continuous tone printers), and simplifies the design of drive ASICs. 
     Small Drop Volume 
     To achieve true 1,600 dpi resolution, a small drop size is required. An IJ46 print head&#39;s drop size is one picoliter (1 pl). The drop size of advanced commercial piezoelectric and thermal ink jet devices is around 3 pl to 30 pl. 
     Accurate Control of Drop Velocity 
     As the drop ejector is a precise mechanical mechanism, and does not rely on bubble nucleation, accurate drop velocity control is available. This allows low drop velocities (3-4 m/s) to be used in applications where media and airflow can be controlled. Drop velocity can be accurately varied over a considerable range by varying the energy provided to the actuator. High drop velocities (10 to 15 m/s) suitable for plain-paper operation and relatively uncontrolled conditions can be achieved using variations of the nozzle chamber and actuator dimensions. 
     Fast Drying 
     A combination of very high resolution, very small drops, and high dye density allows full color printing with much less water ejected. A 1600 dpi IJ46 print head ejects around 33% of the water of a 600 dpi thermal ink jet printer. This allows fast drying and virtually eliminates paper cockle. 
     Wide Temperature Range 
     IJ46 print heads are designed to cancel the effect of ambient temperature. Only the change in ink characteristics with temperature affects operation and this can be electronically compensated. Operating temperature range is expected to be 0° C. to 50° C. for water based inks. 
     No Special Manufacturing Equipment Required 
     The manufacturing process for IJ46 print heads leverages entirely from the established semiconductor manufacturing industry. Most ink jet systems encounter major difficulty and expense in moving from the laboratory to production, as high accuracy specialized manufacturing equipment is required. 
     High Production Capacity Available 
     A 6″ CMOS fab with 10,000 wafer starts per month can produce around 18 million print heads per annum. An 8″ CMOS fab with 20,000 wafer starts per month can produce around 60 million print heads per annum. There are currently many such CMOS fabs in the world. 
     Low Factory Setup Cost 
     The factory set-up cost is low because existing 0.5 micron 6″ CMOS fabs can be used. These fabs could be fully amortized, and essentially obsolete for CMOS logic production. Therefore, volume production can use ‘old’ existing facilities. Most of the MEMS post-processing can also be performed in the CMOS fab. 
     Good Light-Fastness 
     As the ink is not heated, there are few restrictions on the types of dyes that can be used. This allows dyes to be chosen for optimum light-fastness. Some recently developed dyes from companies such as Avecia and Hoechst have light-fastness of 4. This is equal to the light-fastness of many pigments, and considerably in excess of photographic dyes and of ink jet dyes in use until recently. 
     Good Water-Fastness 
     As with light-fastness, the lack of thermal restrictions on the dye allows selection of dyes for characteristics such as water-fastness. For extremely high water-fastness (as is required for washable textiles) reactive dyes can be used. 
     Excellent Color Gamut 
     The use of transparent dyes of high color purity allows a color gamut considerably wider than that of offset printing and silver halide photography. Offset printing in particular has a restricted gamut due to light scattering from the pigments used. With three-color systems (CMY) or four-color systems (CMYK) the gamut is necessarily limited to the tetrahedral volume between the color vertices. Therefore it is important that the cyan, magenta and yellow dies are as spectrally pure as possible. A slightly wider ‘hexcone’ gamut that includes pure reds, greens, and blues can be achieved using a 6 color (CMYRGB) model. Such a six-color print head can be made economically as it requires a chip width of only 1 mm. 
     Elimination of Color Bleed 
     Ink bleed between colors occurs if the different primary colors are printed while the previous color is wet. While image blurring due to ink bleed is typically insignificant at 1600 dpi, ink bleed can ‘muddy’ the midtones of an image. Ink bleed can be eliminated by using microemulsion-based ink, for which IJ46 print heads are highly suited. The use of microemulsion ink can also help prevent nozzle clogging and ensure long-term ink stability. 
     High Nozzle Count 
     An IJ46 print head has 19,200 nozzles in a monolithic CMY three-color photographic print head. While this is large compared to other print heads, it is a small number compared to the number of devices routinely integrated on CMOS VLSI chips in high volume production It is also less than 3% of the number of movable mirrors which Texas Instruments integrates in its Digital Micromirror Device (DMD), manufactured using similar CMOS and MEMS processes. 
     51,200 Nozzles per A4 Page Width Print Head 
     A four color (CMYK) IJ46 print head for page width A4/US letter printing uses two chips. Each 0.66 cm 2  chip has 25,600 nozzles for a total of 51,200 nozzles. 
     Integration of Drive Circuits 
     In a print head with as many as 51,200 nozzles, it is essential to integrate data distribution circuits (shift registers), data timing, and drive transistors with the nozzles. Otherwise, a minimum of 51,201 external connections would be required. This is a severe problem with piezoelectric ink jets, as drive circuits cannot be integrated on piezoelectric substrates. Integration of many millions of connections is common in CMOS VLSI chips, which are fabricated in high volume at high yield. It is the number of off-chip connections that must be limited. 
     Monolithic Fabrication 
     IJ46 print heads are made as a single monolithic CMOS chip, so no precision assembly is required. All fabrication is performed using standard CMOS VLSI and MEMS (Micro-Electro-Mechanical Systems) processes and materials. In thermal ink jet and some piezoelectric ink jet systems, the assembly of nozzle plates with the print head chip is a major cause of low yields, limited resolution, and limited size. Also, page width arrays are typically constructed from multiple smaller chips. The assembly and alignment of these chips is an expensive process. 
     Modular, Extendable for Wide Print Widths 
     Long page width print heads can be constructed by butting two or more 100 mm IJ46 print heads together. The edge of the IJ46 print head chip is designed to automatically align to adjacent chips. One print head gives a photographic size printer, two gives an A4 printer, and four gives an A3 printer. Larger numbers can be used for high speed digital printing, page width wide format printing, and textile printing. 
     Duplex Operation 
     Duplex printing at the full print speed is highly practical. The simplest method is to provide two print heads—one on each side of the paper. The cost and complexity of providing two print heads is less than that of mechanical systems to turn over the sheet of paper. 
     Straight Paper Path 
     As there are no drums required, a straight paper path can be used to reduce the possibility of paper jams. This is especially relevant for office duplex printers, where the complex mechanisms required to turn over the pages are a major source of paperjams. 
     High Efficiency 
     Thermal ink jet print heads are only around 0.01% efficient (electrical energy input compared to drop kinetic energy and increased surface energy). IJ46 print heads are more than 20 times as efficient 
     Self-Cooling Operation 
     The energy required to eject each drop is 160 nJ (0.16 microJoules), a small fraction of that required for thermal ink jet printers. The low energy allows the print head to be completely cooled by the ejected ink, with only a 40° C. worst-case ink temperature rise. No heat sinking is required. 
     Low Pressure 
     The maximum pressure generated in an IJ46 print head is around 60 kPa (0.6 atmospheres). The pressures generated by bubble nucleation and collapse in thermal ink jet and Bubblejet systems are typically in excess of 10 MPa (100 atmospheres), which is 160 times the maximum IJ46 print head pressure. The high pressures in Bubblejet and thermal inkjet designs result in high mechanical stresses. 
     Low Power 
     A 30 ppm A4 IJ46 print head requires about 67 Watts when printing full 3 color black. When printing 5% coverage, average power consumption is only 3.4 Watts. 
     Low Voltage Operation 
     IJ46 print heads can operate from a single 3V supply, the same as typical drive ASICs. Thermal ink jets typically require at least 20 V, and piezoelectric ink jets often require more than 50 V. The IJ46 print head actuator is designed for nominal operation at 2.8 volts, allowing a 0.2 volt drop across the drive transistor, to achieve 3V chip operation. 
     Operation from 2 or 4 AA Batteries 
     Power consumption is low enough that a photographic IJ46 print head can operate from AA batteries. A typical 6″×4″ photograph requires less than 20 Joules to print (including drive transistor losses). Four AA batteries are recommended if the photo is to be printed in 2 seconds. If the print time is increased to 4 seconds, 2 AA batteries can be used. 
     Battery Voltage Compensation 
     IJ46 print heads can operate from an unregulated battery supply, to eliminate efficiency losses of a voltage regulator. This means that consistent performance must be achieved over a considerable range of supply voltages. The IJ46 print head senses the supply voltage, and adjusts actuator operation to achieve consistent drop volume. 
     Small Actuator and Nozzle Area 
     The area required by an IJ46 print head nozzle, actuator, and drive circuit is 1764 μm 2 . This is less than 1% of the area required by piezoelectric ink jet nozzles, and around 5% of the area required by Bubblejet nozzles. The actuator area directly affects the print head manufacturing cost. 
     Small Total Print head Size 
     An entire print head assembly (including ink supply channels) for an A4, 30 ppm, 1,600 dpi, four color print head is 210 mm×12 mm×7 mm. The small size allows incorporation into notebook computers and miniature printers. A photograph printer is 106 mm×7 mm×7 mm, allowing inclusion in pocket digital cameras, palmtop PC&#39;s, mobile phone/fax, and so on. Ink supply channels take most of this volume. The print head chip itself is only 102 mm×0.55 mm×0.3 mm. 
     Miniature Nozzle Capping System 
     A miniature nozzle capping system has been designed for IJ46 print heads. For a photograph printer this nozzle capping system is only 106 mm×5 mm×4 mm, and does not require the print head to move. 
     High Manufacturing Yield 
     The projected manufacturing yield (at maturity) of the IJ46 print heads is at least 80%, as it is primarily a digital CMOS chip with an area of only 0.55 cm 2 . Most modem CMOS processes achieve high yield with chip areas in excess of 1 cm 2 . For chips less than around 1 cm 2 , cost is roughly proportional to chip area. Cost increases rapidly between 1 cm 2  and 4 cm 2 , with chips larger than this rarely being practical. There is a strong incentive to ensure that the chip area is less than 1 cm 2 . For thermal ink jet and Bubblejet print heads, the chip width is typically around 5 mm, limiting the cost effective chip length to around 2 cm. A major target of IJ46 print head development has been to reduce the chip width as much as possible, allowing cost effective monolithic page width print heads. 
     Low Process Complexity 
     With digital IC manufacture, the mask complexity of the device has little or no effect on the manufacturing cost or difficulty. Cost is proportional to the number of process steps, and the lithographic critical dimensions. IJ46 print heads use a standard 0.5 micron single poly triple metal CMOS manufacturing process, with an additional 5 MEMS mask steps. This makes the manufacturing process less complex than a typical 0.25 micron CMOS logic process with 5 level metal. 
     Simple Testing 
     IJ46 print heads include test circuitry that allows most testing to be completed at the wafer probe stage. Testing of all electrical properties, including the resistance of the actuator, can be completed at this stage. However, actuator motion can only be tested after release from the sacrificial materials, so final testing must be performed on the packaged chips. 
     Low Cost Packaging 
     IJ46 print heads are packaged in an injection molded polycarbonate package. All connections are made using Tape Automated Bonding (TAB) technology (though wire bonding can be used as an option). All connections are along one edge of the chip. 
     No Alpha Particle Sensitivity 
     Alpha particle emission does not need to be considered in the packaging, as there are no memory elements except static registers, and a change of state due to alpha particle tracks is likely to cause only a single extra dot to be printed (or not) on the paper. 
     Relaxed Critical Dimensions 
     The critical dimension (CD) of the IJ46 print head CMOS drive circuitry is 0.5 microns. Advanced digital IC&#39;s such as microprocessors currently use CDs of 0.25 microns, which is two device generations more advanced than the IJ46 print head requires. Most of the MEMS post processing steps have CDs of 1 micron or greater. 
     Low Stress During Manufacture 
     Devices cracking during manufacture are a critical problem with both thermal ink jet and piezoelectric devices. This limits the size of the print head that it is possible to manufacture. The stresses involved in the manufacture of IJ46 print heads are no greater than those required for CMOS fabrication. 
     No Scan Banding 
     IJ46 print heads are full page width, so do not scan. This eliminates one of the most significant image quality problems of ink jet printers. Banding due to other causes (mis-directed drops, print head alignment) is usually a significant problem in page width print heads. These causes of banding have also been addressed. 
     ‘Perfect’Nozzle Alignment 
     All of the nozzles within a print head are aligned to sub-micron accuracy by the 0.5 micron stepper used for the lithography of the print head. Nozzle alignment of two 4″ print heads to make an A4 page width print head is achieved with the aid of mechanical alignment features on the print head chips. This allows automated mechanical alignment (by simply pushing two print head chips together) to within 1 micron. If finer alignment is required in specialized applications, 4″ print heads can be aligned optically. 
     No Satellite Drops 
     The very small drop size (1 pl) and moderate drop velocity (3 m/s) eliminates satellite drops, which are a major source of image quality problems. At around 4m/s, satellite drops form, but catch up with the main drop. Above around 4.5 m/s, satellite drops form with a variety of velocities relative to the main drop. Of particular concern is satellite drops which have a negative velocity relative to the print head, and therefore are often deposited on the print head surface. These are difficult to avoid when high drop velocities (around 10 m/s) are used. 
     Laminar Air Flow 
     The low drop velocity requires laminar airflow, with no eddies, to achieve good drop placement on the print medium. This is achieved by the design of the print head packaging. For ‘plain paper’ applications and for printing on other ‘rough’ surfaces, higher drop velocities are desirable. Drop velocities to 15 m/s can be achieved using variations of the design dimensions. It is possible to manufacture 3 color photographic print heads with a 4 m/s drop velocity, and 4 color plain-paper print heads with a 15 m/s drop velocity, on the same wafer. This is because both can be made using the same process parameters. 
     No Misdirected Drops 
     Misdirected drops are eliminated by the provision of a thin rim around the nozzle, which prevents the spread of a drop across the print head surface in regions where the hydrophobic coating is compromised. 
     No Thermal Crosstalk 
     When adjacent actuators are energized in Bubblejet or other thermal ink jet systems, the heat from one actuator spreads to others, and affects their firing characteristics. In IJ46 print heads, heat diffusing from one actuator to adjacent actuators affects both the heater layer and the bend-cancelling layer equally, so has no effect on the paddle position. This virtually eliminates thermal crosstalk. 
     No Fluidic Crosstalk 
     Each simultaneously fired nozzle is at the end of a 300 micron long ink inlet etched through the (thinned) wafer. These ink inlets are connected to large ink channels with low fluidic resistance. This configuration virtually eliminates any effect of drop ejection from one nozzle on other nozzles. 
     No Structural Crosstalk 
     This is a common problem with piezoelectric print heads. It does not occur in IJ46 print heads. 
     Permanent Print Head 
     The IJ46 print heads can be permanently installed. This dramatically lowers the production cost of consumables, as the consumable does not need to include a print head. 
     No Kogation 
     Kogation (residues of burnt ink, solvent, and impurities) is a significant problem with Bubblejet and other thermal ink jet print heads. IJ46 print heads do not have this problem, as the ink is not directly heated. 
     No Cavitation 
     Erosion caused by the violent collapse of bubbles is another problem that limits the life of Bubblejet and other thermal ink jet print heads. IJ46 print heads do not have this problem because no bubbles are formed. 
     No Electromigration 
     No metals are used in IJ46 print head actuators or nozzles, which are entirely ceramic. Therefore, there is no problem with electromigration in the actual ink jet devices. The CMOS metalization layers are designed to support the required currents without electromigration. This can be readily achieved because the current considerations arise from heater drive power, not high speed CMOS switching. 
     Reliable Power Connections 
     While the energy consumption of IJ46 print heads are fifty times less than thermal ink jet print heads, the high print speed and low voltage results in a fairly high electrical current consumption Worst case current for a photographic IJ46 print head printing in two seconds from a 3 Volt supply is 4.9 Amps. This is supplied via copper busbars to 256 bond pads along the edge of the chip. Each bond pad carries a maximum of 40 mA. On chip contacts and vias to the drive transistors carry a peak current of 1.5 mA for 1.3 microseconds, and a maximum average of 12 mA. 
     No Corrosion 
     The nozzle and actuator are entirely formed of glass and titanium nitride (TiN), a conductive ceramic commonly used as metalization barrier layers in CMOS devices. Both materials are highly resistant to corrosion. 
     No Electrolysis 
     The ink is not in contact with any electrical potentials, so there is no electrolysis. 
     No Fatigue 
     All actuator movement is within elastic limits, and the materials used are all ceramics, so there is no fatigue. 
     No Friction 
     No moving surfaces are in contact, so there is no friction. 
     No Stiction 
     The IJ46 print head is designed to eliminate stiction, a problem common to many MEMS devices. Stiction is a word combining “stick” with “friction” and is especially significant at the in MEMS due to the relative scaling of forces. In the IJ46 print head, the paddle is suspended over a hole in the substrate, eliminating the paddle-to-substrate stiction which would otherwise be encountered. 
     No Crack Propagation 
     The stresses applied to the materials are less than 1% of that which leads to crack propagation with the typical surface roughness of the TiN and glass layers. Comers are rounded to minimize stress ‘hotspots’. The glass is also always under compressive stress, which is much more resistant to crack propagation than tensile stress. 
     No Electrical Poling Required 
     Piezoelectric materials must be poled after they are formed into the print head structure. This poling requires very high electrical field strengths—around 20,000 V/cm. The high voltage requirement typically limits the size of piezoelectric print heads to around 5 cm, requiring 100,000 Volts to pole. IJ46 print heads require no poling. 
     No Rectified Diffusion 
     Rectified diffusion—the formation of bubbles due to cyclic pressure variations—is a problem that primarily afflicts piezoelectric ink jets. IJ46 print heads are designed to prevent rectified diffusion, as the ink pressure never falls below zero. 
     Elimination of the Saw Street 
     The saw street between chips on a wafer is typically 200 microns. This would take 26% of the wafer area. Instead, plasma etching is used, requiring just 4% of the wafer area. This also eliminates breakage during sawing. 
     Lithography Using Standard Steppers 
     Although IJ46 print heads are 100 mm long, standard steppers (which typically have an imaging field around 20 mm square) are used. This is because the print head is ‘stitched’ using eight identical exposures. Alignment between stitches is not critical, as there are no electrical connections between stitch regions. One segment of each of 32 print heads is imaged with each stepper exposure, giving an ‘average’ of 4 print heads per exposure. 
     Integration of Full Color on a Single Chip 
     IJ46 print heads integrate all of the colors required onto a single chip. This cannot be done with page width ‘edge shooter’ ink jet technologies. 
     Wide Variety of Inks 
     IJ46 print heads do not rely on the ink properties for drop ejection. Inks can be based on water, microemulsions, oils, various alcohols, MEK, hot melt waxes, or other solvents. IJ46 print heads can be ‘tuned’ for inks over a wide range of viscosity and surface tension. This is a significant factor in allowing a wide range of applications. 
     Laminar Air Flow with No Eddies 
     The print head packaging is designed to ensure that airflow is laminar, and to eliminate eddies. This is important, as eddies or turbulence could degrade image quality due to the small drop size. 
     Drop Repetition Rate 
     The nominal drop repetition rate of a photographic IJ46 print head is 5 kHz, resulting in a print speed of 2 second per photo. The nominal drop repetition rate for an A4 print head is 10 kHz for 30+ppm A4 printing. The maximum drop repetition rate is primarily limited by the nozzle refill rate, which is determined by surface tension when operated using non-pressurized ink. Drop repetition rates of 50 kHz are possible using positive ink pressure (around 20 kPa). However, 34 ppm is entirely adequate for most low cost consumer applications. For very high-speed applications, such as commercial printing, multiple print heads can be used in conjunction with fast paper handling. For low power operation (such as operation from 2 AA batteries) the drop repetition rate can be reduced to reduce power. 
     Low Head-to-Paper Speed 
     The nominal head to paper speed of a photographic IJ46 print head is only 0.076 m/sec. For an A4 print head it is only 0.16 m/sec, which is about a third of the typical scanning ink jet head speed. The low speed simplifies printer design and improves drop placement accuracy. However, this head-to-paper speed is enough for 34 ppm printing, due to the page width print head. Higher speeds can readily be obtained where required. 
     High Speed CMOS Not Required 
     The clock speed of the print head shift registers is only 14 MHz for an A4/letter print head operating at 30 ppm. For a photograph printer, the clock speed is only 3.84 MHz. This is much lower than the speed capability of the CMOS process used. This simplifies the CMOS design, and eliminates power dissipation problems when printing near-white images. 
     Fully Static CMOS Design 
     The shift registers and transfer registers are fully static designs. A static design requires 35 transistors per nozzle, compared to around 13 for a dynamic design. However, the static design has several advantages, including higher noise immunity, lower quiescent power consumption, and greater processing tolerances. 
     Wide Power Transistor 
     The width to length ratio of the power transistor is 688. This allows a 4 Ohm on-resistance, whereby the drive transistor consumes 6.7% of the actuator power when operating from 3V. This size transistor fits beneath the actuator, along with the shift register and other logic. Thus an adequate drive transistor, along with the associated data distribution circuits, consumes no chip area that is not already required by the actuator. 
     There are several ways to reduce the percentage of power consumed by the transistor: increase the drive voltage so that the required current is less, reduce the lithography to less than 0.5 micron, use BiCMOS or other high current drive technology, or increase the chip area, allowing room for drive transistors which are not underneath the actuator. However, the 6.7% consumption of the present design is considered a cost-performance optimum. 
     Range of Applications 
     The presently disclosed ink jet printing technology is suited to a wide range of printing systems. 
     Major example applications include:
     Color and monochrome office printers   SOHO printers   Home PC printers   Network connected color and monochrome printers   Departmental printers   Photographic printers   Printers incorporated into cameras   Printers in 3G mobile phones   Portable and notebook printers   Wide format printers   Color and monochrome copiers   Color and monochrome facsimile machines   Multi-function printers combining print, fax, scan, and copy functions   Digital commercial printers   Short run digital printers   Packaging printers   Textile printers   Short run digital printers   Offset press supplemental printers   Low cost scanning printers   High speed page width printers   Notebook computers with inbuilt page width printers   Portable color and monochrome printers   Label printers   Ticket printers   Point-of-sale receipt printers   Large format CAD printers   Photofinishing printers   Video printers   PhotoCD printers   Wallpaper printers   Laminate printers   Indoor sign printers   Billboard printers   Videogame printers   Photo ‘kiosk’ printers   Business card printers   Greeting card printers   Book printers   Newspaper printers   Magazine printers   Forms printers   Digital photo album printers   Medical printers   Automotive printers   Pressure sensitive label printers   Color proofing printers   Fault tolerant commercial printer arrays.
 
Prior Art ink jet technologies
   

     Similar capability print heads are unlikely to become available from the established ink jet manufacturers in the near future. This is because the two main contenders—thermal ink jet and piezoelectric ink jet—each have severe fundamental problems meeting the requirements of the application. 
     The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for these applications, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. The high power consumption limits the nozzle packing density. 
     The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per print head, but is a major impediment to the fabrication of page width print heads with 19,200 nozzles. 
     Comparison of IJ46 print heads and Thermal Ink Jet (TIJ) printing mechanisms 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 Factor 
                 TIJ print heads 
                 IJ46 print heads 
                 Advantage 
               
               
                   
               
             
            
               
                 Resolution 
                 600 
                  1,600 
                 Full photographic image 
               
               
                   
                   
                   
                 quality and high quality 
               
               
                   
                   
                   
                 text 
               
               
                 Printer 
                 Scanning 
                 Page width 
                 IJ46 print heads do not 
               
               
                 type 
                   
                   
                 scan, resulting in faster 
               
               
                   
                   
                   
                 printing and smaller size 
               
               
                 Print 
                 &lt;1 ppm 
                 30 ppm 
                 IJ46 print head&#39;s page 
               
               
                 speed 
                   
                   
                 width results in &gt;30 
               
               
                   
                   
                   
                 times faster operation 
               
               
                 Number of 
                 300 
                 51,200 
                 &gt;100 times as many 
               
               
                 nozzles 
                   
                   
                 nozzles enables the high 
               
               
                   
                   
                   
                 print speed 
               
               
                 Drop 
                 20 picoliters 
                 1 picoliter 
                 Less water on the paper, 
               
               
                 volume 
                   
                   
                 print is immediately dry, 
               
               
                   
                   
                   
                 no ‘cockle’ 
               
               
                 Construc- 
                 Multi-part 
                 Monolithic 
                 IJ46 print heads do not 
               
               
                 tion 
                   
                   
                 require high precision 
               
               
                   
                   
                   
                 assembly 
               
               
                 Efficiency 
                 &lt;0.1% 
                 2% 
                 20 times increase in 
               
               
                   
                   
                   
                 efficiency results in low 
               
               
                   
                   
                   
                 power operation 
               
               
                 Power 
                 Mains power 
                 Batteries 
                 Battery operation allows 
               
               
                 supply 
                   
                   
                 portable printers, e.g. in 
               
               
                   
                   
                   
                 cameras, phones 
               
               
                 Peak 
                 &gt;100 atm 
                 0.6 atm 
                 The high pressures in a 
               
               
                 pressure 
                   
                   
                 thermal ink jet cause 
               
               
                   
                   
                   
                 reliability problems 
               
               
                 Ink 
                 +300° C. 
                 +50° C. 
                 High ink temperatures 
               
               
                 temper- 
                   
                   
                 cause burnt dye deposits 
               
               
                 ature 
                   
                   
                 (kogation) 
               
               
                 Cavitation 
                 Problem 
                 None 
                 Cavitation (erosion due 
               
               
                   
                   
                   
                 to bubble collapse) limits 
               
               
                   
                   
                   
                 head life 
               
               
                 Head life 
                 Limited 
                 Permanent 
                 TIJ print heads are 
               
               
                   
                   
                   
                 replaceable due to 
               
               
                   
                   
                   
                 cavitation and kogation 
               
               
                 Operating 
                 20 V 
                 3 V 
                 Allows operation from 
               
               
                 voltage 
                   
                   
                 small batteries, important 
               
               
                   
                   
                   
                 for portable and pocket 
               
               
                   
                   
                   
                 printers 
               
               
                 Energy 
                 10 μJ 
                 160 nJ 
                 &lt; 1/50 of the drop ejection 
               
               
                 per drop 
                   
                   
                 energy allows battery 
               
               
                   
                   
                   
                 operation 
               
               
                 Chip area 
                 40,000 μm 2   
                 1,764 μm 2   
                 Small size allows low 
               
               
                 per nozzle 
                   
                   
                 cost manufacture 
               
               
                   
               
            
           
         
       
     
     The presently disclosed ink jet printing technology is potentially suited to a wide range of printing system including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic “minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays. 
     It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.