Method of manufacture of a dual nozzle single horizontal actuator ink jet printer

[0002] The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, US patent applications identified by their U.S. patent application Ser. Nos. (U.S. Ser. No.) are listed alongside the Australian applications from which the U.S. patent applications claim the right of priority.

[0003] Not applicable.

[0004] The present invention relates to the field of ink jet printing and, in particular, discloses a method of manufacture of an ink jet printer having a dual nozzle single horizontal actuator ink jet.

[0005] Many ink jet printing mechanisms are known. Unfortunately, in mass production techniques, the production of ink jet heads is quite difficult. For example, often, the orifice or nozzle plate is constructed separately from the ink supply and ink ejection mechanism and bonded to the mechanism at a later stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)). These separate material processing steps required in handling such precision devices often add a substantial expense in manufacturing.

[0006] Additionally, side shooting ink jet technologies (U.S. Pat. No. 4,899,181) are often used but again, this limits the amount of mass production throughput given any particular capital investment.

[0007] Additionally, more esoteric techniques are also often utilised. These can include electroforming of nickel stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)), electro-discharge machining, laser ablation (U.S. Pat. No. 5,208,604), micro-punching, etc.

[0008] The utilisation of the above techniques is likely to add substantial expense to the mass production of ink jet print heads and therefore add substantially to their final cost.

[0009] It would therefore be desirable if an efficient system for the mass production of ink jet print heads could be developed.

[0010] It is an object of the present invention to provide for a method of manufacture of an ink jet printer having a dual nozzle single horizontal actuator inkjet printer.

[0011] In accordance with a first aspect of the present invention, there is provided a method of manufacture of an ink jet printer having a dual nozzle single horizontal actuator wherein an array of nozzles are formed on a substrate utilising planar monolithic deposition, lithographic and etching processes.

[0012] Multiple ink jet heads are preferably formed simultaneously on a single planar substrate which can comprise a silicon wafer.

[0013] The print heads are preferably formed utilising standard vlsi/ulsi processing and integrated drive electronics are preferably formed on the same substrate. The integrated drive electronics may be formed utilising a CMOS fabrication process.

[0014] Ink can be ejected from the substrate substantially normal to the substrate.

[0015] In accordance with a further aspect of the present invention, there is provided a method of manufacture of a thermally actuated ink jet printer comprising a series of nozzle chambers which ejects ink via the utilization of a thermal actuator device, comprising the steps of: (a) initially providing a silicon wafer having a circuitry wafer layer including the electrical circuitry necessary for the operation of the thermal actuators on demand; (b) etching at least one nozzle chamber pit in the circuitry wafer layer and the silicon wafer; (c) depositing and etching a sacrificial layer filling the ink chamber pit, the etching including etching a first portion of a nozzle chamber wall mold and an actuator anchor mold; (d) depositing and etching a first inert material layer, filling the nozzle chamber wall mould and the actuator anchor mold, the etching including etching a via to the electrical circuitry; (e) depositing and etching a first conductive material layer defining a lower heater element conductively interconnected via the via to the electrical circuitry; (f) depositing and etching a second inert material layer, the etching defining an actuator arm attached to the lower heater element and a second portion of the nozzle chamber wall; (g) depositing and etching a second conductive material layer defining an upper heater element conductively interconnected via a via through the first and second inert material layers to the electrical circuitry; (h) depositing and etching a third inert material layer defining an actuator anchor and further portions of the nozzle chamber wall; (i) depositing and etching a sacrificial layer; (j) depositing and etching a forth inert material layer defining remaining portions of the nozzle chamber, the etching including etching at least one ink ejection nozzle in one of the nozzle chamber walls; (k) etching an ink supply channel to the nozzle chamber through the wafer; and (l) etching away the sacrificial layers.

[0016] The step (k) preferably can include etching an interconnecting channel to one of the nozzle chamber pits.

[0017] The number of ink ejection nozzles can be at least two.

[0018] The conductive material layers are preferably formed from a material having a high Young's modulus such as titanium nitride or a copper nickel alloy. The inert material layers can comprise substantially glass.

[0019] The steps are preferably also utilized to simultaneously separate the wafer into separate printheads.

[0020] 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 in which:

[0021] FIG. 1 shows a schematic side view of an ink jet nozzle of the invention in a quiescent state;

[0022] FIG. 2 shows a schematic side view of the nozzle in an initial part of an ink ejection stage from a first nozzle opening of the nozzle;

[0023] FIG. 3 shows a schematic side view of the nozzle in a further part of the ink ejection stage from the first nozzle opening;

[0024] FIG. 4 shows a schematic side view of the nozzle in an initial part of an ink ejection stage from a second nozzle opening of the nozzle;

[0025] FIG. 5 shows a schematic side view of the nozzle in a further part of the ink ejection stage from the second nozzle opening;

[0026] FIG. 6 illustrates a perspective view, of a single nozzle arrangement of the preferred embodiment;

[0027] FIG. 7 illustrates a perspective view, partly in section of a single nozzle arrangement of the preferred embodiment;

[0028] FIG. 8 shows a schematic side view of an initial stage in the manufacture of an ink jet nozzle of the invention showing a step of an initial etch to form a nozzle cavity and an ink inlet;

[0029] FIG. 9 shows a step of depositing a first sacrificial layer;

[0030] FIG. 10 shows a step of depositing a planarizing glass layer;

[0031] FIG. 11 shows a step of etching the sacrificial material layer;

[0032] FIG. 12 shows a step of etching the glass layer;

[0033] FIG. 13 shows a step of depositing a first heater material layer;

[0034] FIG. 14 shows a step of depositing and etching a further glass layer;

[0035] FIG. 15 shows a step of depositing an aluminum layer;

[0036] FIG. 16 shows a step of depositing a glass layer;

[0037] FIG. 17 shows a step of etching the glass layer;

[0038] FIG. 18 shows a step of depositing a further heater material layer;

[0039] FIG. 19 shows a step of depositing another glass layer;

[0040] FIG. 20 shows a step of etching the glass layer;

[0041] FIG. 21 shows a step of further etching the glass layer;

[0042] FIG. 22 shows a step of depositing a further sacrificial material layer;

[0043] FIG. 23 shows a step of depositing another glass layer;

[0044] FIG. 24 shows a step of etching the glass layer deposited at the step of FIG. 23;

[0045] FIG. 25 shows a step of back etching the substrate;

[0046] FIG. 26 shows a step of etching the sacrificial material layers;

[0047] FIG. 27 illustrates a part of an array view of a printhead as constructed in accordance with the principles of the present invention;

[0048] FIG. 28 provides a legend of the materials indicated in FIGS. 29 to 47; and

[0049] FIG. 29 shows a sectional side view of an initial manufacturing step of an ink jet printhead nozzle showing a silicon wafer layer and an electrical circuitry layer;

[0050] FIG. 30 shows a step of etching the silicon wafer layer;

[0051] FIG. 31 shows a step of etching a sacrificial layer;

[0052] FIG. 32 shows a step of further etching the sacrificial material layer;

[0053] FIG. 33 shows a step of etching a glass layer;

[0054] FIG. 34 shows a step of depositing and planarizing a first heater material layer;

[0055] FIG. 35 shows a step of depositing and etching a glass layer;

[0056] FIG. 36 shows a step of etching a further glass layer;

[0057] FIG. 37 shows a step of further etching the further glass layer;

[0058] FIG. 38 shows a step of depositing a second heater material layer;

[0059] FIG. 39 shows a step of depositing yet a further glass layer;

[0060] FIG. 40 shows a step of etching said yet further glass layer;

[0061] FIG. 41 shows a step of further etching said yet further glass layer;

[0062] FIG. 42 shows a step of depositing a further sacrificial material layer;

[0063] FIG. 43 shows a step of depositing and etching a final glass layer;

[0064] FIG. 44 shows a step of further etching the final glass layer;

[0065] FIG. 45 shows a step back etching the silicon wafer layer;

[0066] FIG. 46 shows a step of etching the sacrificial material layers; and

[0067] FIG. 47 shows a step of filling the completed ink jet nozzle with ink.

[0068] The preferred embodiment of the present invention includes an inkjet arrangement wherein a single actuator drives two output nozzles. When the actuator is driven in a first direction, ink is ejected out of a first nozzle and when the actuator is driven in a second direction, ink is ejected out of a second nozzle. 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 holes.

[0069] Turning initially to FIGS. 6 and 7, there is illustrated a nozzle arrangement 1 of the preferred embodiment with FIG. 7 being a sectional view through the line VII—VII of FIG. 6. The nozzle arrangement 1 includes two ink ejection ports 2, 3 for the ejection of ink from within a nozzle chamber. The nozzle chamber further includes first and second chamber portions 5, 6 in addition to an etched cavity 7 which, during normal operation, are normally filled with ink supplied via an ink inlet channel 8. The ink inlet channel 8 is in turn connected to an ink supply channel 9 etched through a silicon wafer 50. Inside the nozzle chamber is located an actuator paddle 10 which is interconnected through a slot 12 in the chamber wall to an actuator arm 13 which is actuated by means of thermal actuators 14, 15 which are in turn connected to a substrate 17 via an end block portion 18 with the substrate 17 providing the relevant electrical interconnection for the heaters 14, 15.

[0070] Hence, the actuator arm 13 can be actuated by the thermal actuators 14, 15 to move up and down so as to eject ink via the nozzle holes 2 or 3. A series of holes eg. 20-22 are also provided in a top of the nozzle plate. As will become more readily apparent hereinafter, the holes 20-22 assist in the etching of sacrificial layers during construction in addition to providing for “breathing” assistance during operation of the nozzle arrangement 1. The two chambers 5, 6 are separated by a baffle 24 and the paddle arm 10 includes an end lip portion 25 in addition to a plug portion 26. The plug portion 26 is designed to mate with the boundary of the ink inlet channel 8 during operation.

[0071] Turning now to FIGS. 1-5, there will now be explained the operation of the nozzle arrangement 1. Each of FIGS. 1-5 illustrate a cross sectional view of the nozzle arrangement during various stages of operation. Turning initially to FIG. 1, there is shown the nozzle arrangement 1 when in its quiescent position. In this state, the paddle 10 is idle and ink fills the nozzle chamber so as to form menisci 29-33 and 37.

[0072] When it is desired to eject a drop out of the nozzle port 3, as indicated in FIG. 3, the bottom heater 15 is actuated. The heater 15 can comprise a 60% copper and 40% nickel alloy which has a high bending efficiency where the bending efficiency is defined as: $\mathrm{bend}\mathrm{efficiency}=\frac{\mathrm{Young}’s\mathrm{Modulus}\times \left(\mathrm{Coefficient}\mathrm{of}\mathrm{Thermal}\mathrm{Expansion}\right)}{\mathrm{Density}\times \mathrm{Specific}\mathrm{Heat}\mathrm{Capacity}}$

[0073] The two heaters 14, 15 can be constructed from the same material and normally exist in a state of balance when the paddle 10 is in its quiescent position. As noted previously, when it is desired to eject a drop out of nozzle chamber 3 port, the heater 15 is actuated which causes a rapid upwards movement of the actuator paddle 10. This causes a general increase in pressure in the area in front of the actuator paddle 10 which further causes a rapid expansion in the meniscus 30 in addition to a much less significant expansion in the menisci 31-33 (due to their being of a substantially smaller radius). Additionally, the substantial decrease in pressure around the back surface of the paddle 10 causes a general inflow of ink from the nozzle chamber portion 5 in addition to causing a general collapse in the meniscus 29 and a corresponding flow of ink 35 around the baffle 24. A slight bulging also occurs in the meniscus 37 around the slot 12 in the side wall.

[0074] Turning now to FIG. 3, the heater 15 is merely pulsed and turned off when it reaches its maximum extent. Hence, the paddle actuator 10 rapidly begins to return to its quiescent position causing the ink around the ejection port 3 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 10 results in a general necking of the meniscus and the subsequent breaking off of a separate drop 39 which proceeds to the print media. The menisci 29, 31, 32 and 33 each of a generally concave shape exert a further force on the ink within the nozzle chamber which begins to draw ink in from the ink inlet channel 8 so as to replenish the nozzle chamber. Eventually, the nozzle arrangement returns to the quiescent position which is as previously illustrated in respect of FIG. 1.

[0075] Turning now to FIG. 4, when it is desired to eject a droplet of ink out of the ink ejection port 2, the thermal actuator 14 is actuated resulting in a general expansion of the thermal actuator 14 which in turn causes a rapid downward movement of the actuator paddle 10. The rapid downward movement causes a substantial increase in pressure within the cavity 7 which in turn results in a general rapid expansion of the meniscus 29. The end plug portion 26 results in a general blocking of the ink supply channel 8 stopping fluid from flowing back down the ink supply channel 8. This further assists in causing ink to flow towards the cavity 7. The menisci 30-33 of FIG. 1 are drawn generally into the nozzle chamber and may unite so as to form a single meniscus 40. The meniscus 37 is also drawn into the chamber. The heater 14 is merely pulsed, which as illustrated in FIG. 5 results in a rapid return of the paddle 10 to its quiescent position. The return of the paddle 10 results in a general reduction in pressure within the cavity 7 which in turn results in the ink around the nozzle 2 beginning to flow 43 back into the nozzle chamber. The forward momentum of the ink around the meniscus 29 in addition to the backflow 43 results in a general necking of the meniscus and the formation of an ink drop 42 which separates from the main body of the ink and continues to the print media.

[0076] The return of the actuator paddle 10 further results in plugging portion 26 “unplugging” the ink supply channel 8. The general reduction in pressure in addition to the collapsed menisci 40, 37 and 29 results in a flow of ink from the ink inlet channel 8 into the nozzle chamber so as to cause replenishment of the nozzle chamber and return to the quiescent state as illustrated in FIG. 2.

[0077] Returning now to FIG. 6 and FIG. 7, a number of other important features of the preferred embodiment include the fact that each nozzle eg. 2, 3, 20, 21, 22, 12 etc. includes a nozzle rim around its outer periphery. The nozzle rim acts to stop wicking of the meniscus formed across the nozzle rim. Further, the actuator arm 13 is provided with a wick minimisation protrusion eg. 44 in addition to a series of pits eg. 45 which were again shaped so as to minimise wicking along the surfaces surrounding the actuator arms 13.

[0078] The nozzle arrangement of the preferred embodiment can be formed on a silicon wafer utilising standard semiconductor fabrication processing steps and micro-electromechanical systems (MEMS) construction techniques.

[0079] For a general introduction to a micro-electro mechanical system (MEMS) reference is made to standard proceedings in this field including the proceeding of the SPIE (International Society for Optical Engineering) including volumes 2642 and 2882 which contain the proceedings of recent advances and conferences in this field.

[0080] 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.

[0081] Turning to FIG. 8-FIG. 26 there will now be explained one form of fabrication of the preferred embodiment. The preferred embodiment can start with a CMOS processed silicon wafer 50 which can include a standard CMOS layer 51 of the relevant electrical circuitry etc. The processing steps can then be as follows:

[0082] 1. As illustrated in FIG. 8 a deep silicon etch is performed so as to form the nozzle cavity 7 and ink inlet 8. A series of pits eg. 45 are also etched down to an aluminum portion of the CMOS layer 51.

[0083] 2. Next, as illustrated in FIG. 9, a sacrificial material layer 52 is deposited and planarised 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 utilised in MEMS processes as a sacrificial material.

[0084] 3. Next, as illustrated in FIG. 10, a 3 μm layer of low stress glass 53 is deposited and planarized utilising CMP.

[0085] 4. Next, as illustrated in FIG. 11, the sacrificial material 52 is etched to a depth of 1.1 μm and the glass 53 is further etched at least 1.1 μm utilising a first heater mask.

[0086] 5. Next, as illustrated in FIG. 12, the glass is etched eg. 55 down to an aluminum layer eg. 56 of the CMOS layer.

[0087] 6. Next, as illustrated in FIG. 13, a 3 μm layer 57 of 60% copper and 40% nickel alloy is deposited and planarized utilising CMP. The copper and nickel alloy hereinafter called “cupronickel” is a material having a high “bend efficiency” as previously described.

[0088] 7. Next, as illustrated in FIG. 14, a 3 μm layer 60 of low stress glass is deposited and etched utilising a first paddle mask.

[0089] 8. Next, as illustrated in FIG. 15, a further 3 μm 61 layer of aluminum is deposited and planarized utilising chemical mechanical planarization.

[0090] 9. Next, as illustrated in FIG. 16, a 2 μm layer 63 of low stress glass is deposited and etched by 1.1 μm utilizing a heater mask for the second heater.

[0091] 10. As illustrated in FIG. 17, the glass is etched down to the cupronickel layer 57 so as to provide for the upper level heater contact 64.

[0092] 11. Next, as illustrated in FIG. 18, a 3 μm layer 65 of cupronickel alloy is deposited and planarized utilizing CMP.

[0093] 12. Next, as illustrated in FIG. 19, a 71 μm layer 66 of low stress glass is deposited.

[0094] 13. Next, as illustrated in FIG. 20 the glass 66 is etched as at 68 to a depth of 2 μm utilizing a mask for the paddle.

[0095] 14. Next, as illustrated in FIG. 21, the glass 66 is etched as at 69 to a depth of 7 μm using a mask for the nozzle walls, portions of the actuator and the post portion.

[0096] 15. Next, as illustrated in FIG. 22, a 9 μm layer 70 of sacrificial material is deposited and planarized utilising CMP.

[0097] 16. Next, as illustrated in FIG. 23, a 3 μm layer 71 of low stress glass is deposited and etched to a depth of 1 μm utilizing a nozzle rim mask.

[0098] 17. Next, as illustrated in FIG. 24, the glass 71 is etched as at 72 down to the sacrificial layer 70 utilising a nozzle mask.

[0099] 18. Next, as illustrated in FIG. 25, an ink supply channel 9 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.

[0100] 19. Next, as illustrated in FIG. 26, the sacrificial layers are etched away utilising a wet etch so as release the structure of the printhead.

[0101] 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.

[0102] Turning now to FIG. 27, there is illustrated a portion 80 of a full color printhead which is divided into three series of nozzles 81, 82 and 83. Each series can supply a separate color via means of a corresponding ink supply channel. Each series is further subdivided into two subrows 86, 87 with the relevant nozzles of each subrow being fired simultaneously with one subrow being fired a predetermined time after a second subrow such that a line of ink drops is formed on a page.

[0103] As illustrated in FIG. 27 the actuators are 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 (18) of FIG. 6 is formed in the wall of an adjacent series with the block portion of the row 83 being formed in a separate guide rail 90 provided as an abutment surface for the TAB strip when it is abutted against the guide rail 90 so as to provide for an accurate registration of the tab strip with respect to the bond pads 91, 92 which are provided along the length of the printhead so as to provide for low impedance driving of the actuators.

[0104] 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:

[0105] 1. Using a double sided polished wafer 50, complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process to form layer 51. This step is shown in FIG. 29. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 28 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.

[0106] 2. Etch oxide down to silicon or aluminum using Mask 1. This mask defines the pit 45 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.

[0107] 3. Etch silicon 50 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. 30.

[0108] 4. Deposit 23 microns of sacrificial material 52 (e.g. polyimide or aluminum). Planarize to a thickness of 3 microns over the chip surface using CMP.

[0109] 5. Etch the sacrificial layer 52 using Mask 2, which defines the nozzle walls and actuator anchor. This step is shown in FIG. 31.

[0110] 6. Deposit 3 microns of PECVD glass 53 and planarize using CMP.

[0111] 7. Etch the sacrificial material 52 to a depth of 1.1 microns, and glass 53 to a depth of at least 1.1 microns, using Mask 3. This mask defined the lower heater. This step is shown in FIG. 32.

[0112] 8. Etch the glass layer 53 down to aluminum 56 using Mask 4, defining heater vias. This step is shown in FIG. 33.

[0113] 9. Deposit 3 microns of heater material 57 (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.

[0114] 10. Planarize down to the sacrificial layer 52 using CMP. Steps 7 to 10 form a ‘dual damascene’ process. This step is shown in FIG. 34.

[0115] 11. Deposit 3 microns of PECVD glass 60 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. 35.

[0116] 12. Deposit 3 microns of sacrificial material 61 and planarize using CMP.

[0117] 13. Deposit 2 microns of PECVD glass 63.

[0118] 14. Etch the glass 63 to a depth of 1.1 microns, using Mask 6. This mask defined the upper heater. This step is shown in FIG. 36.

[0119] 15. Etch the glass layer 63 down to heater material using Mask 7, defining the upper heater vias 64. This step is shown in FIG. 37.

[0120] 16. Deposit 3 microns of the same heater material 65 as step 9.

[0121] 17. Planarize down to the glass layer 63 using CMP. Steps 14 to 17 form a second dual damascene process. This step is shown in FIG. 38.

[0122] 18. Deposit 7 microns of PECVD glass 66. This step is shown in FIG. 39.

[0123] 19. Etch glass 66 to a depth of 2 microns using Mask 8 as shown at 68. This mask defines the paddle, actuator, actuator anchor, as well as the nozzle walls. This step is shown in FIG. 40.

[0124] 20. Etch glass 66 to a depth of 7 microns (stopping on sacrificial material 61 in exhaust gasses) using Mask 9 as shown at 69. This mask defines the nozzle walls and actuator anchor. This step is shown in FIG. 41.

[0125] 21. Deposit 9 microns of sacrificial material 70 and planarize down to glass 66 using CMP. This step is shown in FIG. 42.

[0126] 22. Deposit 3 microns of PECVD glass 71.

[0127] 23. Etch glass 71 to a depth of 1 micron using Mask 10, which defines the nozzle rims. This step is shown in FIG. 43.

[0128] 24. Etch glass 71 down to the sacrificial layer 70 (3 microns) using Mask 11, defining the nozzles and the nozzle chamber roof. This step is shown in FIG. 44.

[0129] 25. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.

[0130] 26. Back-etch silicon wafer to within approximately 15 microns of the front surface using Mask 8.

[0131] This mask defines the ink inlets 9 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. 45.

[0132] 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. 46.

[0133] 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.

[0134] 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.

[0135] 30. Hydrophobize the front surface of the print heads.

[0136] 31. Fill the completed print heads with ink 74 and test them. A filled nozzle is shown in FIG. 47.

[0137] It would therefore be evident that the preferred embodiment provides for a compact form of manufacture of an inkjet printhead which includes a dual nozzle single actuator system.

[0138] 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 in-built 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 trade mark 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.

[0139] 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.

[0140] Ink Jet Technologies

[0141] The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

[0142] The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, 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. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

[0143] 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 pagewidth print heads with 19,200 nozzles.

[0144] Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include:

[0145] low power (less than 10 Watts)

[0146] high resolution capability (1,600 dpi or more)

[0147] photographic quality output

[0148] low manufacturing cost

[0149] small size (pagewidth times minimum cross section)

[0150] high speed (<2 seconds per page).

[0151] All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table above under the heading Cross References to Related Applications.

[0152] 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

[0153] 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 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.

[0154] Ink is supplied to the back of the print head by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The print head is connected to the camera circuitry by tape automated bonding.

[0155] Tables of Drop-on-Demand Ink Jets

[0156] 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.

[0157] The following tables form the axes of an eleven dimensional table of ink jet types.

[0158] Actuator mechanism (18 types)

[0159] Basic operation mode (7 types)

[0160] Auxiliary mechanism (8 types)

[0161] Actuator amplification or modification method (17 types)

[0162] Actuator motion (19 types)

[0163] Nozzle refill method (4 types)

[0164] Method of restricting back-flow through inlet (10 types)

[0165] Nozzle clearing method (9 types)

[0166] Nozzle plate construction (9 types)

[0167] Drop ejection direction (5 types)

[0168] Ink type (7 types)

[0169] 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 IJ45 which matches the docket numbers in the in the table under the heading Cross References to Related Applications.

[0170] Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet print heads with characteristics superior to any currently available ink jet technology.

[0171] 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 IJ45 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.

[0172] 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.

[0173] The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.