Abstract:
A nozzle arrangement for an inkjet printer. the nozzle arrangement comprising a substrate assembly defining an inlet channel; a nozzle chamber wall and a roof wall collectively positioned on the substrate assembly to define a nozzle chamber in fluid communication with the inlet channel, the roof wall defining an ejection port in fluid communication with the nozzle chamber; a thermal actuator mounted to the substrate assembly and extending into the nozzle chamber to terminate in a free end, the thermal actuator comprising a pair of actuating members spaced apart to form a gap, one of the actuating members being connected to an electrical supply; a heat sink assembly positioned in the gap between the pair of actuating members; and a sealing structure provided between an end of the thermal actuator mounted to the substrate and an end of the thermal actuator terminating in the nozzle chamber, the sealing structure permitting movement of the thermal actuator therein and inhibiting fluid leakage from the nozzle chamber via surface tension.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation Application of U.S. application Ser. No. 12/116,959 filed on May 8, 2008, now U.S. Pat. No. 7,465,010, which is a Continuation Application of U.S. application Ser. No. 11/248,428, filed on Oct. 13, 2005, now issued U.S. Pat. No. 7,380,908, which is a Continuation Application of U.S. application Ser. No. 10/943,846, filed on Sep. 20, 2004, now issued U.S. Pat. No. 6,983,595, which is a Continuation Application of U.S. application Ser. No. 10/667,180, filed on Sep. 22, 2003, now issued U.S. Pat. No. 6,792,754, which is a Continuation-In-Part Application of U.S. application Ser. No. 09/504,221, filed on Feb. 15, 2000, now issued U.S. Pat. No. 6,612,110, all of which are herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an integrated circuit device. In particular, this invention relates to an integrated circuit device for fluid ejection. The invention has broad applications to such devices as micro-electromechanical pumps and micro-electromechanical movers. 
     BACKGROUND 
     Micro-electromechanical devices are becoming increasingly popular and normally involve the creation of devices on the micron scale utilizing semi-conductor fabrication techniques. For a review on micro-electromechanical devices, reference is made to the article “The Broad Sweep of Integrated Micro Systems” by S. Tom Picraux and Paul J. McWhorter published December 1998 in IEEE Spectrum at pages 24 to 33. 
     One form of micro-electromechanical device is an ink jet printing device in which ink is ejected from an ink ejection nozzle chamber. 
     Many different techniques on ink jet printing and associated devices 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 to 220 (1988). 
     Recently, a new form of ink jet printing has been developed by the present applicant that uses micro-electromechanical technology. In one form, ink is ejected from an ink ejection nozzle chamber utilizing an electromechanical actuator connected to a paddle or plunger which moves towards the ejection nozzle of the chamber for ejection of drops of ink from the ejection nozzle chamber. 
     The present invention concerns, but is not limited to, an integrated circuit device that incorporates improvements to an electromechanical bend actuator for use with the technology developed by the Applicant. 
     SUMMARY 
     According to an aspect of the present disclosure, a nozzle arrangement comprises a substrate assembly defining an inlet channel; a nozzle chamber wall and a roof wall collectively positioned on the substrate assembly to define a nozzle chamber in fluid communication with the inlet channel, the roof wall defining an ejection port in fluid communication with the nozzle chamber; a thermal actuator mounted to the substrate assembly and extending into the nozzle chamber to terminate in a free end, the thermal actuator comprising a pair of actuating members spaced apart to form a gap, one of the actuating members being connected to an electrical supply; a heat sink assembly positioned in the gap between the pair of actuating members; and a sealing structure provided between an end of the thermal actuator mounted to the substrate and an end of the thermal actuator terminating in the nozzle chamber, the sealing structure permitting movement of the thermal actuator therein and inhibiting fluid leakage from the nozzle chamber via surface tension. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings. 
         FIG. 1  is a schematic side-sectioned view of a nozzle arrangement of one embodiment of an integrated circuit device in accordance with the invention, in a pre-firing condition. 
         FIG. 2  is a schematic side-sectioned view of a nozzle arrangement of  FIG. 1 , in a firing condition. 
         FIG. 3  is a schematic side-sectioned view of a nozzle arrangement of  FIG. 1 , in a post firing condition. 
         FIG. 4  illustrates a prior art thermal bend actuator in a pre-firing condition. 
         FIG. 5  illustrates the actuator of  FIG. 4  in a firing condition. 
         FIG. 6  illustrates the actuator of  FIG. 4  in a post-firing condition. 
         FIG. 7  illustrates a thermal bend actuator in a pre-firing condition to explain the invention. 
         FIG. 8  illustrates the actuator of  FIG. 7  in a firing condition. 
         FIG. 9  illustrates a thermal bend actuator of an integrated circuit device of the invention in a pre-firing condition. 
         FIG. 10  illustrates the actuator of  FIG. 9  in a firing condition. 
         FIG. 11  is a schematic diagram of a thermal actuator indicating a problem addressed by the invention. 
         FIG. 12  is a graph of temperature with respect to distance for the actuator of  FIG. 11 . 
         FIG. 13  is a schematic diagram of an arm indicating an aspect of the invention. 
         FIG. 14  is a graph of temperature with respect to distance for the am of  FIG. 13 . 
         FIG. 15  illustrates schematically a thermal bend actuator of an integrated circuit device of the invention. 
         FIG. 16  is a side perspective view of a CMOS wafer prior to fabrication of one of a plurality of nozzle arrangements of a second embodiment of an integrated circuit device in accordance with the invention. 
         FIG. 17  illustrates, schematically, multiple CMOS masks used in the fabrication of the CMOS wafer. 
         FIG. 18  is a side-sectioned view of the wafer of  FIG. 16 . 
         FIG. 19  is a perspective view of the wafer of  FIG. 16  with a first sacrificial layer deposited onto the wafer. 
         FIG. 20  illustrates a mask used for the deposition of the first sacrificial layer. 
         FIG. 21  is a side-sectioned view of the wafer of  FIG. 19 . 
         FIG. 22  is a perspective view of the wafer of  FIG. 19  with a first layer of titanium nitride positioned on the first sacrificial layer. 
         FIG. 23  illustrates a mask used for the deposition of the first titanium nitride layer. 
         FIG. 24  is a side-sectioned view of the wafer of  FIG. 22 . 
         FIG. 25  is a perspective view of the wafer of  FIG. 22  with a second sacrificial layer deposited on the first layer of titanium nitride. 
         FIG. 26  illustrates a mask used for the deposition of the second sacrificial layer. 
         FIG. 27  is a sectioned side view of the wafer of  FIG. 25 . 
         FIG. 28  is a perspective view of the wafer of  FIG. 25  with a second layer of titanium nitride deposited on the second sacrificial layer. 
         FIG. 29  illustrates a mask for the deposition of the second layer of titanium nitride. 
         FIG. 30  illustrates a side-sectioned view of the wafer of  FIG. 28 . 
         FIG. 31  is a perspective view of the wafer of  FIG. 28  with a third layer of sacrificial material deposited on the second layer of titanium nitride. 
         FIG. 32  illustrates a mask used for the deposition of the sacrificial material. 
         FIG. 33  is a side-sectioned view of the wafer of  FIG. 31 . 
         FIG. 34  is a perspective view of the wafer of  FIG. 31  with a layer of structural material deposited on the third layer of sacrificial material. 
         FIG. 35  illustrates that a mask is not used for the deposition of the structural material. 
         FIG. 36  is a side-sectioned view of the wafer of  FIG. 34 . 
         FIG. 37  is a perspective view of the wafer of  FIG. 34  subsequent to an etching process carried out on the structural material. 
         FIG. 38  illustrates a mask used for etching the structural material. 
         FIG. 39  is a side-sectioned view of the wafer of  FIG. 37 . 
         FIG. 40  is a perspective view of the wafer of  FIG. 37  subsequent to a further etching process carried out on the structural material. 
         FIG. 41  illustrates a mask used for etching the structural material. 
         FIG. 42  is a side-sectioned view of the wafer of  FIG. 40 . 
         FIG. 43  is a perspective view of the wafer of  FIG. 40  with a protective sacrificial layer deposited on the structural material. 
         FIG. 44  indicates that a mask is not used for the deposition of the protective sacrificial layer. 
         FIG. 45  is a side-sectioned view of the mask of  FIG. 43 . 
         FIG. 46  is a perspective view of the wafer of  FIG. 43  subsequent to a back etch being carried out on the wafer. 
         FIG. 47  illustrates a mask used for the back etch. 
         FIG. 48  is a side-sectioned view of the wafer of  FIG. 46 . 
         FIG. 49  is a perspective view of the wafer of  FIG. 46  with all the sacrificial material stripped from the wafer of  FIG. 46 . 
         FIG. 50  indicates that a mask is not used for the stripping of the sacrificial material. 
         FIG. 51  is a side-sectioned view of the wafer of  FIG. 49 . 
         FIG. 52  is a perspective view of the nozzle arrangement filled with fluid for testing purposes. 
         FIG. 53  indicates that a mask is not used. 
         FIG. 54  is a side-sectioned view of the nozzle arrangement of  FIG. 52 . 
         FIG. 55  is a side-sectioned perspective view of the nozzle arrangement in a firing condition. 
         FIG. 56  is a side-sectioned view of the nozzle arrangement of  FIG. 55 . 
         FIG. 57  is a side-sectioned perspective view of the nozzle arrangement in a post-firing condition. 
         FIG. 58  is a side-sectioned view of the nozzle arrangement of  FIG. 57 . 
         FIG. 59  is a perspective view of the nozzle arrangement. 
         FIG. 60  is a detailed sectioned perspective view showing an arrangement of an actuator arm and nozzle chamber walls of the nozzle arrangement. 
         FIG. 61  is a detailed sectioned perspective view of a paddle and fluid channel of the nozzle arrangement. 
         FIG. 62  is a detailed sectioned view of part of the actuator arm of the nozzle arrangement. 
         FIG. 63  is a top plan view of an array of the nozzle arrangements. 
         FIG. 64  is a perspective view of the array of nozzle arrangements; and 
         FIG. 65  is a detailed perspective view of the array of nozzle arrangements. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIGS. 1 to 3 , reference numeral  10  generally indicates a first embodiment of a nozzle arrangement of an integrated circuit device, in accordance with the invention. 
     The nozzle arrangement  10  is one of a plurality that comprises the device. One has been shown simply for the sake of convenience. 
     In  FIG. 1 , the nozzle arrangement  10  is shown in a quiescent stage. In  FIG. 2 , the nozzle arrangement  10  is shown in an active, pre-ejection stage. In  FIG. 3 , the nozzle arrangement  10  is shown in an active, pre-ejection stage. 
     The nozzle arrangement  10  includes a wafer substrate  12 . A layer of a passivation material  20 , such as silicon nitride, is positioned on the wafer substrate  12 . A nozzle chamber wall  14  and a roof wall  16  are positioned on the wafer substrate  12  to define a nozzle chamber  18 . The roof wall  16  defines an ejection port  22  that is in fluid communication with the nozzle chamber  18 . 
     An inlet channel  24  extends through the wafer substrate  12  and the passivation material  20  into the nozzle chamber  18  so that fluid to be ejected from the nozzle chamber  18  can be fed into the nozzle chamber  18 . In this particular embodiment the fluid is ink, indicated at  26 . Thus, the fluid ejection device of the invention can be in the form of an inkjet printhead chip. 
     The nozzle arrangement  10  includes a thermal actuator  28  for ejecting the fluid  26  from the nozzle chamber  18 . The thermal actuator  28  includes a paddle  30  that is positioned in the nozzle chamber  18 , between an outlet of the inlet channel  24  and the ejection port  22  so that movement of the paddle  30  towards and away from the ejection port  22  results in the ejection of fluid  26  from the ejection port. 
     The thermal actuator  28  includes an actuating arm  32  that extends through an opening  33  defined in the nozzle chamber wall  14  and is connected to the paddle  30 . 
     The actuating arm  32  includes an actuating portion  34  that is connected to CMOS layers (not shown) positioned on the substrate  12  to receive electrical signals from the CMOS layers. 
     The actuating portion  34  has a pair of spaced actuating members  36 . The actuating members  36  are spaced so that one of the actuating members  36 . 1  is spaced between the other actuating member  36 . 2  and the passivation layer  20  and a gap  38  is defined between the actuating members  36 . Thus, for the sake of convenience, the actuating member  36 . 1  is referred to as the lower actuating member  36 . 1 , while the other actuating member is referred to as the upper actuating member  36 . 2 . 
     The lower actuating member  36 . 1  defines a heating circuit and is of a material having a coefficient of thermal expansion that permits the actuating member  36 . 1  to perform work upon expansion. The lower actuating member  36 . 1  is connected to the CMOS layers to the exclusion of the upper actuating member  36 . 2 . Thus, the lower actuating member  36 . 1  expands to a significantly greater extent than the upper actuating member  36 . 2 , when the lower actuating member  36 . 1  receives an electrical signal from the CMOS layers. This causes the actuating arm  32  to be displaced in the direction of the arrows  40  in  FIG. 2 , thereby causing the paddle  30  and thus the fluid  26  also to be displaced in the direction of the arrows  40 . The fluid  26  thus defines a drop  42  that remains connected, via a neck  44  to the remainder of the fluid  26  in the nozzle chamber  18 . 
     The actuating members  36  are of a resiliently flexible material. Thus, when the electrical signal is cut off and the lower actuating member  36 . 1  cools and contracts, the upper actuating member serves to drive the actuating arm  32  and paddle  30  downwardly in the direction of an arrow  29 , thereby generating a reduced pressure in the nozzle chamber  18 , which, together with the forward momentum of the drop  42  results in the separation of the drop  42  from the remainder of the fluid  26 . 
     It is of importance to note that the gap  38  between the actuating members  36  serves to inhibit buckling of the actuating arm  32  as is explained in further detail below. 
     The nozzle chamber wall  14  defines a re-entrant portion  46  at the opening  33 . The passivation layer  20  defines a channel  48  that is positioned adjacent the re-entrant portion  46 . The re-entrant portion  46  and the actuating arm  32  provide points of attachment for a meniscus that defines a fluidic seal  50  to inhibit the egress of fluid  26  from the opening  33  while the actuating arm  32  is displaced. The channel  48  inhibits the wicking of any fluid that may be ejected from the opening  33 . 
     A raised formation  52  is positioned on an upper surface of the paddle  30 . The raised formation  52  inhibits the paddle  30  from making contact with a meniscus  31 . Contact between the paddle  30  and the meniscus  31  would be detrimental to the operational characteristics of the nozzle arrangement  10 . 
     A stepped formation  25  is positioned on the passivation material  20  defining an edge of the inlet channel  24 . The stepped formation  25  is shaped and dimensioned so that, when the paddle  30  is displaced towards the ejection port  22 , an opening  23  is defined between the paddle  30  and the formation  25  at a rate that facilitates the entry of fluid into the nozzle chamber  18  in the direction of arrows  27  in  FIG. 3 . 
     A nozzle rim  54  is positioned about the ejection port  22 . 
     In  FIGS. 4 to 6 , reference numeral  60  generally indicates a thermal actuator of the type that the Applicant has identified as exhibiting certain problems and over which the present invention distinguishes. 
     The thermal actuator  60  is in the form of a thermal bend actuator that uses differential expansion as a result of uneven heating to generate movement and thus perform work. 
     The thermal actuator  60  is fast with a substrate  62  and includes an actuator arm  64  that is displaced to perform work. The actuator arm  64  has a fixed end  66  that is fast with the substrate  62 . A fixed end portion  67  of the actuator arm  64  is sandwiched between and fast with a lower activating arm  68  and an upper activating arm  70 . The activating arms  68 ,  70  are substantially the same to ensure that they remain in thermal equilibrium, for example during quiescent periods. The material of the arms  68 ,  70  is such that, when heated, the arms  68 ,  70  are capable of expanding to a degree sufficient to perform work. 
     The lower activating arm  68  is capable of being heated to the exclusion of the upper activating arm  70 . It will be appreciated that this will result in a differential expansion being set up between the arms, with the result that the actuator arm  64  is driven upwardly to perform work against a pressure P, as indicated by the arrow  72 . 
     In order to achieve this, the arms  68 ,  70  must be fast with the arm  64 . It has been found that, if the arms  68 ,  70  exceed a particular length, then the arms  68 ,  70  and the fixed end portion  67  are susceptible to buckling as shown in  FIG. 6 . It will be appreciated that this is undesirable. 
     In  FIGS. 7 and 8 , reference numeral  80  generally indicates a further thermal bend actuator by way of illustration of the principles of the present invention. With reference to  FIGS. 4 to 6 , like reference numerals refer to like parts, unless otherwise specified. 
     The thermal bend actuator  80  has shortened activation arms  68 ,  70 . This serves significantly to reduce the risk of buckling as described above. However, it has been found that, to achieve useful movement, as shown in  FIG. 8 , it is necessary for the fixed end portion  67  to be subjected to substantial shear stresses. This can have a detrimental effect on the operational characteristics of the actuator  80 . The high shear stresses can also result in delamination of the actuator arm  64 . 
     Furthermore, in both the embodiments of the thermal actuator  60 ,  80 , the temperature to which the lower activation arm can be heated is limited by characteristics of the fixed end portion  67 , such as the melting point of the fixed end portion  67 . 
     Thus, the Applicant has conceived, schematically, the thermal bend actuator as shown in  FIGS. 9 and 10 . Reference numeral  82  refers generally to that thermal bend actuator. With reference to  FIGS. 4 to 8 , like reference numerals refer to like parts, unless otherwise specified. 
     The thermal bend actuator  82  does not include the fixed end portion  67 . Instead, ends  84  of the activating arms  68 ,  70 , opposite the substrate  62 , are fast with the fixed end  66  of the actuator arm  64 , instead of the fixed end  66  being fast with the substrate  62 . Thus, the fixed end portion  67  is replaced with a gap  86 , equivalent to the gap  38  described above. As a result, the activating arms  68 ,  70  can operate without being limited by the characteristics of the actuator arm  64 . Further, shear stresses are not set up in the actuator arm  64  so that delamination is avoided. Buckling is also avoided by the configuration shown in  FIGS. 9 and 10 . 
     In  FIG. 11 , reference numeral  90  generally indicates a schematic layout of a thermal actuator for illustration of a problem that Applicant has identified with thermal actuators. 
     The thermal actuator  90  includes an actuator arm  92 . The actuator arm  92  is positioned between a pair of heat sink members  91 . It will be appreciated that when the arm  92  is heated, the resultant thermal expansion will result in the heat sink members  91  being driven apart. The graph shown in  FIG. 12  is a temperature v. distance graph that indicates the relationship between the temperature applied to the actuator arm  92  and the position along the actuator arm  92 . 
     As can be seen from the graph, at some point  93  intermediate the heat sinks  91 , the melting point, indicated at  89 , of the actuator arm  92 , is exceeded. This is clearly undesirable, as this would cause a breakdown in the operation of the actuator arm  92 . The graph clearly indicates that the level of heating of the actuator arm  92  varies significantly along the length of the actuator arm  92 , which is undesirable. 
     In  FIG. 13 , reference numeral  94  generally indicates a further layout of a thermal actuator, for illustrative purposes. With reference to  FIG. 11 , like reference numerals refer to like parts, unless otherwise specified. 
     The thermal actuator  94  includes a pair of heat sinks  96  that are positioned on the actuator arm  92  between the heat sink members  91 . The graph shown in  FIG. 14  is a graph of temperature v. distance along the actuator arm  92 . As can be seen in that graph, that point intermediate the heat sink members  91  is inhibited from reaching the melting point of the actuator arm  92 . Furthermore, the actuator arm  92  is heated more uniformly along its length than in the thermal actuator  80 . 
     In  FIG. 15 , reference numeral  98  generally indicates a thermal actuator that incorporates some of the principles of the present invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified. 
     The thermal actuator  98  is similar to the thermal actuator  82  shown in  FIGS. 9 and 10 . However, further to enhance the operational characteristics of the thermal actuator  98 , a pair of heat sinks  100  is positioned in the gap  86 , in contact with both the upper and lower activation arms  68 , 70 . Furthermore, the heat sinks  100  are configured to define a pair of spaced struts to provide the thermal actuator  98  with integrity and strength. The spaced struts  100  serve to inhibit buckling as the arm  64  is displaced. 
     In  FIGS. 55 to 59 , reference numeral  110  generally indicates a second embodiment of a nozzle arrangement of an integrated circuit device, in accordance with the invention, part of which is generally indicated by reference numeral  112  in  FIGS. 60 to 62 . 
     The device  112  includes a wafer substrate  114 . A fluid passivation layer in the form of a layer of silicon nitride  116  is positioned on the wafer substrate  114 . A cylindrical nozzle chamber wall  118  is positioned on the silicon nitride layer  116 . A roof wall  120  is positioned on the nozzle chamber wall  118  so that the roof wall  120  and the nozzle chamber wall  118  define a nozzle chamber  122 . 
     A fluid inlet channel  121  is defined through the substrate  114  and the silicon nitride layer  116 . 
     The roof wall  120  defines a fluid ejection port  124 . A nozzle rim  126  is positioned about the fluid ejection port  124 . 
     An anchoring member  128  is mounted on the silicon nitride layer  116 . A thermal actuator  130  is fast with the anchoring member  128  and extends into the nozzle chamber  122  so that, on displacement of the thermal actuator  130 , fluid is ejected from the fluid ejection port  124 . The thermal actuator  130  is fast with the anchoring member  128  to be in electrical contact with CMOS layers (not shown) positioned on the wafer substrate  114  so that the thermal actuator  130  can receive an electrical signal from the CMOS layers. 
     The thermal actuator  130  includes an actuator arm  132  that is fast with the anchoring member  128  and extends towards the nozzle chamber  122 . A paddle  134  is positioned in the nozzle chamber  122  and is fast with an end of the actuator arm  132 . 
     The actuator arm  132  includes an actuating portion  136  that is fast with the anchoring member  128  at one end and a sealing structure  138  that is fast with the actuating portion at an opposed end. The paddle  134  is fast with the sealing structure  138  to extend into the nozzle chamber  122 . 
     The actuating portion  136  includes a pair of spaced substantially identical activating arms  140 . One of the activating arms  140 . 1  is positioned between the other activating arm  140 . 2  and the silicon nitride layer  116 . A gap  142  is defined between the arms  140  and is equivalent to the gap  38  described with reference to  FIGS. 1 to 3 . 
     As can be seen in  FIG. 59 , the actuating portion  136  is divided into two identical portions  143  that are spaced in a plane that is parallel to the substrate  114 . 
     The activating arm  140 . 1  is of a conductive material that has a coefficient of thermal expansion that is sufficient to permit work to be harnessed from thermal expansion of the activating arm  140 . 1 . The activating arm  140 . 1  defines a resistive heating circuit that is connected to the CMOS layers to receive an electrical current from the CMOS layers, so that the activating arm  140 . 1  undergoes thermal expansion. The activating arm  140 . 2 , on the other hand, is not connected to the CMOS layers and therefore undergoes a negligible amount of expansion, if any. This sets up differential expansion in the actuation portion  136  so that the actuating portion  136  is driven away from the silicon nitride layer  116  and the paddle  134  is driven towards the ejection port  124  to generate a drop  144  of fluid that extends from the port  124 . When the electrical current is cut off, the resultant cooling of the actuating portion  136  causes the arm  140 . 1  to contract so that the actuating portion  136  moves back to a quiescent condition towards the silicon nitride layer  116 . The actuator arm  132  is also of a resiliently flexible material. This enhances the movement towards the silicon nitride layer  116 . 
     As a result of the paddle  134  moving back to its quiescent condition, a fluid pressure within the nozzle chamber is reduced and the fluid drop  144  separates as a result of the reduction in pressure and the forward momentum of the fluid drop  144 , as shown in  FIGS. 57 and 58 . In use, the CMOS layers can generate a high frequency electrical potential so that the actuator arm is able to oscillate at that frequency, thereby permitting the paddle  134  to generate a stream of fluid drops. 
     A heat sink member  146  is mounted on the activating arm  140 . 1 . The heat sink member  146  serves to ensure that a temperature gradient along the arm  140 . 1  does not peak excessively at or near a centre of the arm  140 . 1 . Thus, the arm  140 . 1  is inhibited from reaching its melting point while still maintaining suitable expansion characteristics. 
     A strut  148  is connected between the activating arms  140  to ensure that the activating arms  140  do not buckle as a result of the differential expansion of the activating arms  140 . Detail of the strut  148  is shown in  FIG. 62 . 
     The purpose of the sealing structure  138  is to permit movement of the actuating arm and the paddle  134  while inhibiting leakage of fluid from the nozzle chamber  122 . This is achieved by the roof wall  120 , the nozzle chamber wall  118  and the sealing structure  138  defining complementary formations  150  that, in turn, with the fluid, set up fluidic seals which accommodate such movement. These fluidic seals rely on the surface tension of the fluid to retain a meniscus that prevents the fluid from escaping from the nozzle chamber  122 . 
     The sealing structure  138  has a generally I-shaped profile when viewed in plan. Thus, the sealing structure  138  has an arcuate end portion  156 , a leg portion  158  and a rectangular base portion  160 , the leg portion  158  interposed between the end portion  156  and the base portion  160 , when viewed in plan. The roof wall  120  defines an arcuate slot  152  which accommodates the end portion  156  and the nozzle chamber wall  118  defines an opening into the arcuate slot  152 , the opening being dimensioned to accommodate the leg portion  158 . The roof wall  120  defines a ridge  162  about the slot  152  and part of the opening. The ridge  162  and edges of the end portion  156  and leg portion  158  of the sealing structure  138  define purchase points for a meniscus that is generated when the nozzle chamber  122  is filled with fluid, so that a fluidic seal is created between the ridge  162  and the end and leg portions  156 ,  158 . 
     As can be seen in  FIG. 60 , a transverse profile of the sealing structure  138  reveals that the end portion  156  extends partially into the fluid inlet channel  121  so that it overhangs an edge of the silicon nitride layer  116 . The leg portion  158  defines a recess  164 . The nozzle chamber wall  118  includes a re-entrant formation  166  that is positioned on the silicon nitride layer  116 . Thus, a tortuous fluid flow path  168  is defined between the silicon nitride layer  116 , the re-entrant formation  166 , and the end and leg portions  156 ,  158  of the sealing structure  138 . This serves to slow the flow of fluid, allowing a meniscus to be set up between the re-entrant formation  166  and a surface of the recess  164 . 
     A channel  170  is defined in the silicon nitride layer  116  and is aligned with the recess  164 . The channel  170  serves to collect any fluid that may be emitted from the tortuous fluid flow path  168  to inhibit wicking of that fluid along the layer  116 . 
     The paddle  134  has a raised formation  172  that extends from an upper surface  174  of the paddle  134 . Detail of the raised formation  172  can be seen in  FIG. 61 . The raised formation  172  is essentially the same as the raised formation  52  of the first embodiment. The raised formation  172  thus prevents the surface  174  of the paddle  134  from making contact with a meniscus  186 , which would be detrimental to the operating characteristics of the nozzle arrangement  110 . The raised formation  172  also serves to impart rigidity to the paddle  134 , thereby enhancing the operational efficiency of the paddle  134 . 
     Importantly, the nozzle chamber wall  118  is shaped so that, as the paddle  134  moves towards the fluid ejection port  124  a sufficient increase in a space between a periphery  184  of the paddle  134  and the nozzle chamber wall  118  takes place to allow for a suitable amount of fluid to flow rapidly into the nozzle chamber  122 . This fluid is drawn into the nozzle chamber  122  when the meniscus  186  re-forms as a result of surface tension effects. This allows for refilling of the nozzle chamber  122  at a suitable rate. 
     In  FIGS. 63 and 64 , reference numeral  180  generally indicates an integrated circuit device that incorporates a plurality of the nozzle arrangements  110 . 
     The plurality of the nozzle arrangements  110  are positioned in a predetermined array  182  that spans a printing area. It will be appreciated that each nozzle arrangement  110  can be actuated with a single pulse of electricity such as that which would be generated with an “on” signal. It follows that printing by the chip  180  can be controlled digitally right up to the operation of each nozzle arrangement  110 . 
     In  FIGS. 16 and 18 , reference numeral  190  generally indicates a wafer substrate  192  with multiple CMOS layers  194  in an initial stage of fabrication of the nozzle arrangement  110 , in accordance with the invention. This form of fabrication is based on integrated circuit fabrication techniques. As is known, such techniques use masks and deposition, developing and etching processes. Furthermore, such techniques usually involve the replication of a plurality of identical units on a single wafer. Thus, the fabrication process described below is easily replicated to achieve the chip  180 . Thus, for convenience, the fabrication of a single nozzle arrangement  110  is described with the understanding that the fabrication process is easily replicated to achieve the device  180 . 
     In  FIG. 17 , reference numeral  196  is a mask used for the fabrication of the multiple CMOS layers  194 . 
     The CMOS layers  194  are fabricated to define a connection zone  198  for the anchoring member  128 . The CMOS layers  194  also define a recess  200  for the channel  170 . The wafer substrate  192  is exposed at  202  for future etching of the fluid inlet channel  121 . 
     In  FIGS. 19 and 21 , reference numeral  204  generally indicates the structure  190  with a 1-micron thick layer of photosensitive, sacrificial polyimide  206  spun on to the structure  190  and developed. 
     The layer  206  is developed using a mask  208 , shown in  FIG. 20 . 
     In  FIGS. 22 and 24 , reference numeral  210  generally indicates the structure  204  with a 0.2-micron thick layer of titanium nitride  212  deposited on the structure  204  and subsequently etched. 
     The titanium nitride  212  is sputtered on the structure  204  using a magnetron. Then, the titanium nitride  212  is etched using a mask  214  shown in  FIG. 23 . The titanium nitride  212  defines the activating arm  140 . 1 , the re-entrant formation  166  and the paddle  134 . It will be appreciated that the polyimide  206  ensures that the activating arm  140 . 1  is positioned 1 micron above the silicon nitride layer  116 . 
     In  FIGS. 25 and 27 , reference numeral  216  generally indicates the structure  210  with a 1.5-micron thick layer  218  of sacrificial photosensitive polyimide deposited on the structure  210 . 
     The polyimide  218  is developed with ultra-violet light using a mask  220  shown in  FIG. 26 . 
     The remaining polyimide  218  is used to define a deposition zone  222  for the activating arm  140 . 2  and a deposition zone  224  for the raised formation  172  on the paddle  134 . Thus, it will be appreciated that the gap  142  has a thickness of 1.5 micron. 
     In  FIGS. 28 and 30 , reference numeral  226  generally indicates the structure  216  with a 0.2-micron thick layer  228  of titanium nitride deposited on the structure  216 . 
     Firstly, a 0.05-micron thick layer of PECVD silicon nitride (not shown) is deposited on the structure  216  at a temperature of 572 degrees Fahrenheit. Then, the layer  228  of titanium nitride is deposited on the PECVD silicon nitride. The titanium nitride  228  is etched using a mask  230  shown in  FIG. 29 . 
     The remaining titanium nitride  228  is then used as a mask to etch the PECVD silicon nitride. 
     The titanium nitride  228  serves to define the activating arm  140 . 2 , the raised formation  172  on the paddle  134 , and the heat sink members  146 . 
     In  FIGS. 31 and 33 , reference numeral  232  generally indicates the structure  226  with 6 microns of photosensitive polyimide  234  deposited on the structure  226 . 
     The polyimide  234  is spun on and exposed to ultra violet light using a mask  236  shown in  FIG. 32 . The polyimide  234  is then developed. 
     The polyimide  234  defines a deposition zone  238  for the anchoring member  128 , a deposition zone  240  for the sealing structure  138 , a deposition zone  242  for the nozzle chamber wall  118  and a deposition zone  244  for the roof wall  120 . 
     It will be appreciated that the thickness of the polyimide determines the height of the nozzle chamber  122 . A degree of taper of 1 micron from a bottom of the chamber to the top can be accommodated. 
     In  FIGS. 34 and 36 , reference numeral  246  generally indicates the structure  232  with 2 microns of PECVD silicon nitride  247  deposited on the structure  232 . 
     This serves to fill the deposition zones  238 ,  240 ,  242  and  244  with the PECVD silicon nitride. As can be seen in  FIG. 35 , no mask is used for this process. 
     In  FIGS. 37 and 39 , reference numeral  248  generally indicates the PECVD silicon nitride  246  etched to define the nozzle rim  126 , the ridge  162  and a portion of the sealing structure  138 . 
     The PECVD silicon nitride  246  is etched using a mask  250  shown in  FIG. 38 . 
     In  FIGS. 40 and 42  reference numeral  252  generally indicates the structure  248  with the PECVD silicon nitride  246  etched to define a surface of the anchoring member  128 , a further portion of the sealing structure  138  and the fluid ejection port  124 . 
     The etch is carried out using a mask  254  shown in  FIG. 41  to a depth of 1 micron stopping on the polyimide  234 . 
     In  FIGS. 43 and 45 , reference numeral  256  generally indicates the structure  252  with a protective layer  258  of polyimide spun on to the structure  252  as a protective layer for back etching the structure  256 . 
     As can be seen in  FIG. 44 , a mask is not used for this process. 
     In  FIGS. 46 and 48 , reference numeral  259  generally indicates the structure  256  subjected to a back etch. 
     In this step, the wafer substrate  114  is thinned to a thickness of 300 microns. 3 microns of a resist material (not shown) are deposited on the back side of the wafer  114  and exposed using a mask  260  shown in  FIG. 47 . Alignment is to metal portions  262  on a front side of the wafer  114 . This alignment is achieved using an IR microscope attached to a wafer aligner. 
     The back etching then takes place to a depth of 330 microns (allowing for a 10% overetch) using a deep-silicon “Bosch Process” etch. This process is available on plasma etchers from Alcatel, Plasma-therm, and Surface Technology Systems. The chips are also diced by this etch, but the wafer is still held together by 11 microns of the various polyimide layers. This etch serves to define the fluid inlet channel  121 . 
     In  FIGS. 49 and 51 , reference numeral  264  generally indicates the structure  259  with all the sacrificial material stripped. This is done in an oxygen plasma etching process. As can be seen in  FIG. 50 , a mask is not used for this process. 
     In  FIGS. 52 and 54 , reference numeral  266  generally indicates the structure  264 , which is primed with fluid  268 . In particular, a package is prepared by drilling a 0.5 mm hole in a standard package, and gluing a fluid hose (not shown) to the package. The fluid hose should include a 0.5-micron absolute filter to prevent contamination of the nozzles from the fluid  268 . 
     The integrated circuit device of the invention is potentially suited to a wide range of printing systems including: colour 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 in-built pagewidth printers, portable colour and monochrome printers, colour and monochrome copiers, colour and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic ‘minilabs’, video printers, PHOTOCD™ printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays. 
     Further, the MEMS fabrication principles outlined have general applicability in the construction of MEMS devices. 
     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 preferred embodiment without departing from the spirit or scope of the invention as broadly described. The preferred embodiment is, therefore, to be considered in all respects to be illustrative and not restrictive.