Abstract:
A method for creating an inkjet chamber. The method comprises the steps of firstly providing a substrate having a nozzle opening and secondly etching the substrate through the nozzle opening by alternating between anisotropic and isotropic etching processes for forming a chamber having a shape approximating a cylinder by using multiple hemispheric etches.

Description:
FIELD OF THE INVENTION 
   The invention relates generally to the field of inkjet recording heads, and in particular to a method of manufacturing an inkjet chamber. More specifically, the invention relates to the manufacture of inkjet chambers using an etching scheme that alternates between isotropic and anisotropic etches. This process enhances the performance of an inkjet recording device by enabling a finer control of detail within an inkjet chamber through the use of colorless, odorless, nontoxic, non-flammable liquefied gasses such as SULFURHEXAFLUORIDE SF 6 , and OCTAFLUOROCYCLOBUTANE C 4 F 8 , that are each used specifically for the type of etching performed. 
   BACKGROUND OF THE INVENTION 
   An inkjet recording head typically comprises outlets or nozzles that serve to eject tiny droplets of liquids used in a recording process. Situated behind the nozzles, a chamber exists that contains both electrically activated thermal electrodes producing bubbles to eject the drops, and a chamber that encloses the aforementioned electrodes. 
   A more conventional method of ejecting drops is commonly referred to as the roof-shooter method. In the roof-shooter method the bubble grows in the same direction as the drop is ejected. A typical manufacturing process for a roof-shooter inkjet recording head is represented in U.S. Pat. No. 5,478,606 by Ohkuma et al. Recently a back-shooter method has been disclosed in U.S. Pat. No. 5,760,804 to Heinzl et al. issued Jun. 2, 1998. In the back-shooter method the bubble grows in opposite direction to the drop ejection direction. 
   In the back-shooter configuration the design properties of the chamber are important in order to optimize the drop ejection and chamber refill efficiencies. These properties help achieve a high drop ejection frequency. Typical chamber structures are disclosed in U.S. Pat. No. 6,019,457 to Silverbrook issued Feb. 1, 2000 and U.S. Pat. No. 6,561,626 to Jae-sik Min et al. issued May 13, 2003. The aforementioned prior art describes a chamber, hemispheric in shape, formed by isotropic etching with an ink inlet, the same diameter as the nozzle, formed by anisotropic etching through the nozzle. 
   To control the refill impedance of an inkjet chamber, it is important to be able to control the ink inlet diameter. A recent publication, U.S. patent application Ser. No. 2003/0109073 Al by Park et al., discusses a method of manufacturing a monolithic ink-jet printhead. The discussion includes the preparation of a silicon substrate, the forming of an ink passage comprised of a manifold that supplies ink, an ink chamber filled with ink supplied from the manifold, an ink channel connecting the ink chamber to the manifold, and a nozzle through which ink is ejected. The ink chamber is formed by isotropically etching the silicon substrate through the nozzle to form the shape of the ink chamber in a hemisphere. The ink channel is formed by anisotropically dry etching the silicon substrate from the bottom surface of the ink chamber through the nozzle. The passage of a Xe—F 2  gas through the ink passage dry etches the wall of the ink passage, and permits the smoothing of the wall that more precisely adjusts the passage to some design dimension thereby improving the printing performance of the printhead. This process, however, is limited in the scope of what it can produce. Often there are additional problems and technical needs associated with the production of print-heads that require unique inkjet chamber geometries to further enhance writing performance, that are economically unattainable by present processes. 
   Consequently, a need exists for overcoming the above-described shortcomings. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, disclosed is a method for creating an inkjet chamber. The method comprises the steps of firstly providing a substrate having a nozzle opening and secondly etching the substrate through the nozzle opening by alternating between anisotropic and isotropic etching processes for forming a chamber having a shape approximating a cylinder by using multiple hemispheric etches. 
   The above and other objects of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. 
   ADVANTAGEOUS EFFECT OF THE INVENTION 
   The present invention has advantages over the prior art in that this invention allows increased manufacturability and performance of an inkjet printhead. The present invention creates an ability to control a plurality of parameters such as nozzle size and finish separately and in relation to chamber geometry and finish of an inkjet printhead. The invention produces cost and performance advantages over prior art in that this ability to control real-time the design parameters of a chamber enables the matching of the system impedance of a printhead by the matching of a required nozzle design to an ink supply chamber. This perfects the system impedance, enhances the system performance, and lowers printhead-manufacturing costs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-section of an inkjet printhead of the present invention prior to chamber formation; 
       FIG. 2  is a cross-section of an inkjet printhead of the present invention showing a first anisotropic etch and a second isotropic etch; 
       FIG. 3  is a cross-section of an inkjet printhead of the present invention showing a series of alternating anisotropic and isotropic etches; and 
       FIG. 4  is a cross-section of an inkjet printhead of the present invention showing a plurality of nozzle and ink supply bores that are attainable by the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , shown is a cross-sectional side view of a section of an inkjet printhead  10 , prior to formation of an inkjet chamber, and is representative of a typical unfinished inkjet printhead  10 . A nozzle plate  20  is formed on a printhead substrate  50 . The nozzle plate  20  additionally includes a nozzle plate bottom layer  13 . Disposed upon the nozzle plate bottom layer  13  is a heater  15  that is adjacent to a future nozzle region  30  (shown dashed) wherein a nozzle will be formed. It is useful to note at this point that future nozzle region  30  may also comprise an existing nozzle or orifice prior to performing the etching process. It should be clearly understood at this point that an existing and manufactured inkjet printhead  10  could be re-etched, modified or otherwise re-manufactured through pre-existing features using the etching process herein described. 
   Referring next to  FIG. 2 , shown is a cross-sectional side view of an inkjet printhead  10 , that details an output nozzle  35 , highlighted by a dashed circle, and represents output nozzle  35  being a first etch  80 . The first etch  80  produces a first feature that is represented by output nozzle  35 , by switching between a first gas such as SULFURHEXAFLUORIDE SF 6 , and a second gas such as OCTAFLUOROCYCLOBUTANE C 4 F 8 , and produces the beginning of an inkjet chamber  25 . Note that the first etch  80  is an anisotropic etch, and produces an essentially cylindrical bore much like that produced by a drill. The second etch  90  using just SULFURHEXAFLUORIDE SF 6  alone is an isotropic etch and produces a hemispherically shaped feature. This second etch  90  has the unique ability to produce an undercut of the nozzle plate  20 , which in turn will produce a nozzle plate bottom  40 . The switching of active gasses in the present invention to produce sequential cuts with different features creates an ability to actively machine an inkjet chamber  25  of inkjet printhead  10  to an optimum shape. Additionally, a finer control of the relative shape of the inkjet chamber  25  is realized through a plurality of sequential isotropic and anisotropic etches. 
   Referring now to  FIG. 3 , there is shown an additional cross-sectional side view of the inkjet printhead  10 , showing the printhead nozzle plate  20 , output nozzle  35 , and an inkjet chamber  25 , shown dashed, that also represents a finished first operation. The first etch  80  and second etch  90  produces an inkjet chamber  25 , and encompasses an essentially hemispheric shape overall. Since an essentially smooth wall surface and a greater etching depth may be desirable within the inkjet printhead  10 , the means of producing those results is as follows. Still referring to  FIG. 3 , a third etch  110  and a fourth etch  120  would be necessary to produce a greater etching depth within the inkjet printhead  10 . These additional etching operations wherein the third etch  110 , and the fourth etch  120  are anisotropic and isotropic etches respectfully, etch away more printhead material  50 , and further serve to shape the inkjet chamber  25 . The finish of the new chamber walls created by fourth etch  120  is controllable. By adding a plurality of closely spaced anisotropic and isotropic etching steps, a finely finished but slightly arcuate shaped feature will be achieved. It is important to note at this point that the undercut of the nozzle plate  20  must extend past the outer extremity of the heater  15 . 
   Referring now to  FIG. 4 , there is shown a cross-sectional side view of an inkjet printhead  10  of the present invention. A printhead nozzle plate  20  and a nozzle plate bottom  40  enclose a heater  15  that serves to eject ink from an output nozzle  35 . The previously described and completed fourth etch  120  produces a finished chamber wall that possesses the arcuate shaped finish that is produced by the plurality of closely spaced sequential anisotropic and isotropic etches. It should be understood at this point that while four etches are discussed herein, any multiplicity of etches are possible to achieve a desired effect. The ink supply interface  60  separates the printhead material  50  from the ink supply manifold  70 . Connecting the finished chamber produced by the fourth etch  120  and the ink supply manifold  70  is an ink supply channel area  130  and the area is defined with a dashed circle. This ink supply channel area  130  and the ability of the present invention to control its size produces an ability to precisely control the operating impedance of the inkjet printhead  10 . The operating impedance of printhead  10  is defined as how fast the inkjet chamber  25  refills as a result of ejecting ink by actuating the heating element  15  and ejecting ink through output nozzle  35 . It is instructive to note that ink can be defined, as any one of a plurality of substances such as inks, medicines, and liquids comprised of other assorted substances. The operating impedance is controlled by the ability to vary the size of the output nozzle  35  in relation to the size of the ink supply channel area  130 . The ink entry port can comprise a plurality of sizes including a small ink entry port  150 , large ink entry port  160 , and a medium ink entry port  170  that is substantially the same size as the output nozzle  35 . The output nozzle  35  and the ink supply channel area  130  can each be of any size necessary to eject a desired volume of ink, and those sizes can be controlled in the etching processes heretofore described. The sizes of the output nozzle  35  and the ink supply channel area  130  are varied by controlling the isotropic etches. By pushing the leading edges of an isotropic etch more or less through the ink supply interface  60 , the ink supply channel area  130  can be of a plurality of sizes including the small ink entry port  150 , large ink entry port  160 , and a medium ink entry port  170 . Further, by expanding the edges of an isotropic etch and undercutting the roof bottom  40  the bottom surface of heating element  15  can be exposed and provide maximum heat transfer into the ink. 
   The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
   
     
       
             
           
             
             
           
         
             
                 
             
             
               PARTS LIST 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               10 
               inkjet printhead 
             
             
               13 
               nozzle plate bottom layer 
             
             
               15 
               heater 
             
             
               20 
               nozzle plate 
             
             
               25 
               inkjet chamber 
             
             
               30 
               nozzle region 
             
             
               35 
               output nozzle 
             
             
               40 
               nozzle plate bottom 
             
             
               50 
               printhead substrate 
             
             
               60 
               ink supply interface 
             
             
               70 
               ink supply manifold 
             
             
               80 
               first etch 
             
             
               90 
               second etch 
             
             
               110 
               third etch 
             
             
               120 
               fourth etch 
             
             
               130 
               ink supply channel area 
             
             
               150 
               small ink entry port 
             
             
               160 
               large ink entry port 
             
             
               170 
               medium ink entry port