Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/135—Nozzles
  • B41J2/16—Production of nozzles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/135—Nozzles
  • B41J2/16—Production of nozzles
  • B41J2/1621—Manufacturing processes
  • B41J2/1626—Manufacturing processes etching
  • B41J2/1628—Manufacturing processes etching dry etching
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/135—Nozzles
  • B41J2/16—Production of nozzles
  • B41J2/1621—Manufacturing processes
  • B41J2/1631—Manufacturing processes photolithography
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/135—Nozzles
  • B41J2/16—Production of nozzles
  • B41J2/1621—Manufacturing processes
  • B41J2/1632—Manufacturing processes machining
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/135—Nozzles
  • B41J2/16—Production of nozzles
  • B41J2/1621—Manufacturing processes
  • B41J2/164—Manufacturing processes thin film formation
  • B41J2/1642—Manufacturing processes thin film formation thin film formation by CVD [chemical vapor deposition]

Definitions

• the present invention relates to the field of inkjet printheads manufactured using micro-electromechanical systems (MEMS) techniques.
• MEMS micro-electromechanical systems
• US Patent No. 3,596,275 also discloses a process of a continuous ink jet printing including the step wherein the inkjet stream is modulated by a high frequency electro-static field so as to cause drop separation.
• This technique is still utilized by several manufacturers including Elmjet and Scitex (see also US Patent No. 3,373,437 (Sweet et al)
• Piezoelectric inkjet printers are also one form of commonly utilized inkjet printing device. Piezoelectric systems are disclosed by Kyser et. al. in US Patent No. 3,946,398 which utilizes a diaphragm mode of operation, by Zolten in US Patent No.
• thermal ink jet printing has become an extremely popular form of ink jet printing.
• the ink jet printing techniques include those disclosed by Endo et al in GB 2007162 and Vaught et al in US 4,490,728.
• Both the aforementioned references disclosed ink jet printing techniques that rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media.
• Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard. As can be seen from the foregoing, many different types of printing technologies are available.
• a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
• MEMS micro-electromechanical systems
• printhead maintenance increases the lifetime of a printhead and enables the printhead to be used after idle periods. Typical aims of printhead maintenance are the removal of particulates from the printhead, removing ink flooded onto the printhead face, and unblocking of nozzles which may become blocked with ink ('decap') or particulates. Hitherto, a variety of techniques have been used for printhead maintenance, such as suction cappers and squeegee-type wipers.
• MEMS pagewidth printhead which is amenable to a plethora of printhead maintenance techniques, including contact maintenance techniques. It would be further desirable to provide a MEMS printhead having superior mechanical robustness. It would be further desirable to provide a MEMS printhead, which traps a minimal number of particulates and hence facilitates printhead maintenance.
• an inkjet printhead comprising a reinforced bi- layered nozzle plate structure spanning across a plurality of nozzles.
• each nozzle comprises a nozzle chamber having a roof, each roof being defined by part of said nozzle plate structure.
• the nozzle chambers are formed on a substrate.
• each nozzle chamber comprises said roof spaced apart from said substrate, and sidewalls extending between said roof and said substrate.
• each roof has a nozzle aperture defined therein.
• the nozzle plate structure comprises: a first nozzle plate spanning a plurality of nozzles, said first nozzle plate having a plurality of cavities defined therein; photoresist filling said cavities; and a second nozzle plate covering said first nozzle plate and said photoresist.
• the second nozzle plate defines a planar, exterior surface of said printhead.
• the first and second nozzle plates are comprised of the same or different materials.
• the materials are ceramic materials depositable by PECVD.
• the materials are independently selected from the group comprising: silicon nitride, silicon oxide and silicon oxynitride.
• each nozzle comprises a nozzle chamber formed on a substrate, said nozzle chamber comprising a roof spaced apart from said substrate and sidewalls extending between said roof and said substrate, wherein said first nozzle plate and said sidewalls are comprised of the same material.
• an inkjet printhead integrated circuit comprising: a substrate having a plurality of nozzles formed thereon; drive circuitry electrically connected to actuators associated with said nozzles; and a reinforced bi-layered nozzle plate structure spanning across said plurality of nozzles.
• a method of fabricating an inkjet printhead having a planar nozzle plate comprising the steps of: (a) providing a partially- fabricated printhead having a first nozzle plate comprised of a first material spanning a plurality of nozzles, said first nozzle plate having a plurality of cavities;
• the second material is deposited by PECVD.
• the first material is deposited by PECVD onto a non-planar sacrificial scaffold to form said first nozzle plate.
• the first and second materials are the same or different from each other.
• the first and second materials are independently selected from the group comprising: silicon nitride, silicon oxide and silicon oxynitride.
• the filler is photoresist.
• step (b) is performed by the sub-steps of:
• the method further comprises the step of: thermally reflowing said photoresist to facilitate complete filling of said cavities.
• step (b)(ii) is performed by chemical mechanical planarization or by photoresist etching.
• the method further comprises the step of:
• each nozzle comprises a nozzle chamber formed on a substrate, said nozzle chamber comprising a roof spaced apart from said substrate and sidewalls extending between said roof and said substrate, wherein said first nozzle plate and said sidewalls are comprised of the same material.
• the printhead according to the invention comprises a plurality of nozzles, and typically a chamber and actuator (e.g. heater element) corresponding to each nozzle.
• the smallest repeating units of the printhead will generally have an ink supply inlet feeding ink to one or more chambers.
• An entire nozzle array is formed by repeating these individual units.
• Such an individual unit is generally referred to herein as a "unit cell”.
• a printhead may be comprised of a plurality of printhead integrated circuits, each printhead integrated circuit comprising a plurality of nozzles.
• the term "ink” is used to signify any ejectable liquid, and is not limited to conventional inks containing colored dyes.
• non-colored inks include fixatives, infra-red absorber inks, functionalized chemicals, adhesives, biological fluids, medicaments, water and other solvents, and so on.
• the ink or ejectable liquid also need not necessarily be a strictly a liquid, and may contain a suspension of solid particles.
• Figure 1 shows a partially fabricated unit cell of the MEMS nozzle array on a printhead according to the present invention, the unit cell being section along A-A of Figure 3;
• Figure 2 shows a perspective of the partially fabricated unit cell of Figure 1;
• Figure 3 shows the mark associated with the etch of the heater element trench
• Figure 4 is a sectioned view of the unit cell after the etch of the trench
• Figure 5 is a perspective view of the unit cell shown in Fig 4;
• Figure 6 is the mask associated with the deposition of sacrificial photoresist shown in Figure 7;
• Figure 7 shows the unit cell after the deposition of sacrificial photoresist trench, with partial enlargements of the gaps between the edges of the sacrificial material and the side walls of the trench;
• Figure 8 is a perspective of the unit cell shown in Fig 7;
• Figure 9 shows the unit cell following the re flow of the sacrificial photoresist to close the gaps along the side walls of the trench
• Figure 10 is a perspective of the unit cell shown in Fig 9;
• Figure 11 is a section view showing the deposition of the heater material layer
• Figure 12 is a perspective of the unit cell shown in Fig 11;
• Figure 13 is the mask associated with the metal etch of the heater material shown in Figure 14;
• Figure 14 is a section view showing the metal etch to shape the heater actuators
• Figure 15 is a perspective of the unit cell shown in Fig 14;
• Figure 16 is the mask associated with the etch shown in Fig 17;
• Figure 17 shows the deposition of the photoresist layer and subsequent etch of the ink inlet to the passivation layer on top of the CMOS drive layers
• Figure 18 is a perspective of the unit cell shown in Fig 17;
• Figure 19 shows the oxide etch through the passivation and CMOS layers to the underlying silicon wafer
• Figure 20 is a perspective of the unit cell shown in Fig 19;
• Figure 21 is the deep anisotropic etch of the ink inlet into the silicon wafer
• Figure 22 is a perspective of the unit cell shown in Fig 21;
• Figure 23 is the mask associated with the photoresist etch shown in Fig 24;
• Figure 24 shows the photoresist etch to form openings for the chamber roof and side walls
• Figure 25 is a perspective of the unit cell shown in Fig 24;
• Figure 26 shows the deposition of the side wall and risk material
• Figure 27 is a perspective of the unit cell shown in Fig. 26;
• Figure 28 is the mask associated with the nozzle rim etch shown in Fig 29;
• Figure 29 shows the etch of the roof layer to form the nozzle aperture rim
• Figure 30 is a perspective of the unit cell shown in Fig 29;
• Figure 31 is the mask associated with the nozzle aperture etch shown in Fig 32;
• Figure 32 shows the etch of the roof material to form the elliptical nozzle apertures
• Figure 33 is a perspective of the unit cell shown in Fig 32;
• Figure 34 shows the unit cell after backside etching, plasma ashing and wafer thinning
• Figure 35 is a perspective of the unit cell shown in Fig 34.
• Figure 36 is a cutaway perspective of an array of nozzles on a printhead integrated circuit.
• Figure 37 is a perspective of the unit cell shown in Figure 27 after cavity filling
• Figure 38 is a side view of the unit cell shown in Figure 37 after a second roof deposition
• Figure 39 is a perspective of the unit cell shown in Figure 38.
• Figure 40 is a cutaway perspective of a printhead integrated circuit with a reinforced bi- layered nozzle plate.
• each row of nozzles has a respective ink supply channel 27 extending along its length and supplying ink to a plurality of ink inlets 15 in each row.
• the ink inlets supply ink to an ink conduit 23 for each row, with each nozzle chamber receiving ink from a common ink conduit extending longitudinally along each row.
• Nozzle apertures 26, having a respective nozzle rim 25, are defined in a nozzle plate 101, which spans across the rows and columns of nozzles.
• the nozzle plate 101 is formed by PECVD of a ceramic material (e.g. silicon nitride) onto a photoresist scaffold. By virtue of this deposition process, the nozzle plate
• the 101 has a plurality of cavities 102 defined therein.
• the cavities 102 are disposed in between adjacent nozzle in a row. These cavities 102 are typically several microns deep (e.g. 1-5 microns deep) and introduce discontinuities into the nozzle plate 101.
• the overall effect is a nozzle plate, which is substantially non-planar by virtue of these cavities 102.
• the cavities 102 are substantially non-planar by virtue of these cavities 102.
• 102 may be substantially larger (wider, longer or deeper) than is illustrated in Figure 36. They may extend significantly between rows or columns of nozzles.
• the discontinuity or non-planarity arising from the cavities 102 in the nozzle plate 101 is disadvantageous for several reasons. Firstly, the cavities 102 are points of weakness in the nozzle plate 101 and reduce the overall mechanical robustness of the printhead, particularly with respect to sheer forces imparted across the nozzle plate. This is especially significant, because wiping actions across the surface of the nozzle plate 101 (as may be used during some types of printhead maintenance) cause relatively high sheer forces. Secondly, the cavities 102 can easily trap ink and/or particulates, which are then difficult to remove. The proximity of the cavities 102 to the nozzle apertures 26 is especially undesirable, because any trapped particulates are more likely to obscure nozzles and affect print quality.
• FIG. 2 is a cutaway perspective view of a nozzle unit cell 100 after the completion of CMOS processing and before MEMS processing.
• CMOS processing of the wafer four metal layers are deposited onto a silicon wafer 2, with the metal layers being interspersed between interlayer dielectric (ILD) layers.
• ILD interlayer dielectric
• the four metal layers are referred to as Ml, M2, M3 and M4 layers and are built up sequentially on the wafer during CMOS processing.
• These CMOS layers provide all the drive circuitry and logic for operating the printhead.
• each heater element actuator is connected to the CMOS via a pair of electrodes defined in the outermost M4 layer.
• the M4 CMOS layer is the foundation for subsequent MEMS processing of the wafer.
• the M4 layer also defines bonding pads along a longitudinal edge of each printhead integrated circuit. These bonding pads (not shown) allow the CMOS to be connected to a microprocessor via wire bonds extending from the bonding pads.
• Figures 1 and 2 show the aluminium M4 layer 3 having a passivation layer 4 deposited thereon. (Only MEMS features of the M4 layer are shown in these Figures; the main CMOS features of the M4 layer are positioned outside the nozzle unit cell).
• the M4 layer 3 has a thickness of 1 micron and is itself deposited on a 2 micron layer of CVD oxide 5.
• the M4 layer 3 has an ink inlet opening 6 and pit openings 7. These openings define the positions of the ink inlet and pits formed subsequently in the MEMS process.
• bonding pads along a longitudinal edge of each printhead integrated circuit are defined by etching through the passivation layer 4. This etch reveals the M4 layer 3 at the bonding pad positions.
• the nozzle unit cell 1 is completely masked with photoresist for this step and, hence, is unaffected by the etch.
• the first stage of MEMS processing etches a pit 8 through the passivation layer 4 and the CVD oxide layer 5.
• This etch is defined using a layer of photoresist (not shown) exposed by the dark tone pit mask shown in Figure 3.
• the pit 8 has a depth of 2 microns, as measured from the top of the M4 layer 3.
• electrodes 9 are defined on either side of the pit by partially revealing the M4 layer 3 through the passivation layer 4.
• a heater element is suspended across the pit 8 between the electrodes 9.
• the pit 8 is filled with a first sacrificial layer (“SACl”) of photoresist 10.
• SACl first sacrificial layer
• a 2 micron layer of high viscosity photoresist is first spun onto the wafer and then exposed using the dark tone mask shown in Figure 6.
• the SACl photoresist 10 forms a scaffold for subsequent deposition of the heater material across the electrodes 9 on either side of the pit 8. Consequently, it is important the SACl photoresist
• the SACl photoresist must completely fill the pit 8 to avoid 'stringers' of conductive heater material extending across the pit and shorting out the electrodes 9.
• this technique results in a raised (or spiked) rim of photoresist around the perimeter of the trench.
• the present process deliberately exposes the SACl photoresist 10 inside the perimeter walls of the pit 8 ⁇ e.g. within 0.5 microns) using the mask shown in Figure 6. This ensures a planar upper surface of the SACl photoresist 10 and avoids any spiked regions of photoresist around the perimeter rim of the pit 8.
• the photoresist After exposure of the SACl photoresist 10, the photoresist is reflowed by heating. Reflowing the photoresist allows it to flow to the walls of the pit 8, filling it exactly.
• Figures 9 and 10 show the SACl photoresist 10 after reflow.
• the photoresist has a planar upper surface and meets flush with the upper surface of the M4 layer 3, which forms the electrodes 9.
• the SACl photoresist 10 is U.V. cured and/or hardbaked to avoid any reflow during the subsequent deposition step of heater material.
• Figures 11 and 12 show the unit cell after deposition of the 0.5 microns of heater material 11 onto the SACl photoresist 10. Due to the reflow process described above, the heater material 11 is deposited evenly and in a planar layer over the electrodes 9 and the SACl photoresist 10.
• the heater material may be comprised of any suitable conductive material, such as TiAl, TiN, TiAlN, TiAlSiN etc.
• a typical heater material deposition process may involve sequential deposition of a 100 A seed layer of TiAl, a 2500 A layer of TiAlN, a further 100 A seed layer of TiAl and finally a further 2500 A layer of TiAlN.
• the layer of heater material 11 is etched to define the thermal actuator 12.
• Each actuator 12 has contacts 28 that establish an electrical connection to respective electrodes 9 on either side of the SACl photoresist 10.
• a heater element 29 spans between its corresponding contacts 28. This etch is defined by a layer of photoresist (not shown) exposed using the dark tone mask shown in Figure 13.
• the heater element 12 is a linear beam spanning between the pair of electrodes 9.
• the heater element 12 may alternatively adopt other configurations, such as those described in Applicant's US Patent No. 6,755,509, the content of which is herein incorporated by reference.
• an ink inlet for the nozzle is etched through the passivation layer 4, the oxide layer 5 and the silicon wafer 2.
• each of the metal layers had an ink inlet opening (see, for example, opening 6 in the M4 layer 3 in Figure 1) etched therethrough in preparation for this ink inlet etch.
• a relatively thick layer of photoresist 13 is spun onto the wafer and exposed using the dark tone mask shown in Figure 16.
• the thickness of photoresist 13 required will depend on the selectivity of the deep reactive ion etch (DRIE) used to etch the ink inlet. With an ink inlet opening 14 defined in the photoresist 13, the wafer is ready for the subsequent etch steps.
• DRIE deep reactive ion etch
• the dielectric layers are etched through to the silicon wafer below. Any standard oxide etch (e.g. O 2 /C 4 F 8 plasma) may be used.
• an ink inlet 15 is etched through the silicon wafer 2 to a depth of 25 microns, using the same photoresist mask 13. Any standard anisotropic DRIE, such as the Bosch etch (see US Patent Nos. 6,501,893 and 6,284,148) may be used for this etch. Following etching of the ink inlet 15, the photoresist layer 13 is removed by plasma ashing.
• the ink inlet 15 is plugged with photoresist and a second sacrificial layer (“SAC2") of photoresist 16 is built up on top of the SACl photoresist 10 and passivation layer 4.
• SAC2 photoresist 16 will serve as a scaffold for subsequent deposition of roof material, which forms a roof and sidewalls for each nozzle chamber.
• a ⁇ 6 micron layer of high viscosity photoresist is spun onto the wafer and exposed using the dark tone mask shown in Figure 23.
• the mask exposes sidewall openings 17 in the SAC2 photoresist 16 corresponding to the positions of chamber sidewalls and sidewalls for an ink conduit.
• openings 18 and 19 are exposed adjacent the plugged inlet 15 and nozzle chamber entrance respectively.
• These openings 18 and 19 will be filled with roof material in the subsequent roof deposition step and provide unique advantages in the present nozzle design.
• the openings 18 filled with roof material act as priming features, which assist in drawing ink from the inlet 15 into each nozzle chamber.
• the openings 19 filled with roof material act as filter structures and fluidic cross talk barriers. These help prevent air bubbles from entering the nozzle chambers and diffuses pressure pulses generated by the thermal actuator 12.
• nozzle chambers 24 having a roof 21 and sidewalls 22.
• An ink conduit 23 for supplying ink into each nozzle chamber is also formed during deposition of the roof material 20.
• any priming features and filter structures are formed at the same time.
• the roof material 20 may be comprised of any suitable material, such as silicon nitride, silicon oxide, silicon oxynitride, aluminium nitride etc.
• the nozzle plate 101 has cavities 102 (shown in Figure 36) in regions between nozzles.
• the next stage defines an elliptical nozzle rim 25 in the roof 21 by etching away 2 microns of roof material 20. This etch is defined using a layer of photoresist (not shown) exposed by the dark tone rim mask shown in Figure 28.
• the elliptical rim 25 comprises two coaxial rim lips 25a and 25b, positioned over their respective thermal actuator 12.
• the next stage defines an elliptical nozzle aperture 26 in the roof 21 by etching all the way through the remaining roof material 20, which is bounded by the rim 25. This etch is defined using a layer of photoresist (not shown) exposed by the dark tone roof mask shown in Figure 31.
• the elliptical nozzle aperture 26 is positioned over the thermal actuator 12, as shown in Figure 33.
• the nozzle plate 101 is deposited by PECVD.
• PECVD plasma vapor deposition
• the nozzle plate fabrication can be incorporated into a MEMS fabrication process which uses standard CMOS deposition/etch techniques.
• the overall manufacturing cost of the printhead can be kept low.
• many prior art printheads have laminated nozzle plates, which are not only susceptible to delamination, but also require a separate lamination step that cannot be performed by standard CMOS processing. Ultimately, this adds to the cost of such printheads.
• PECVD deposition of the nozzle plate 101 has its own challenges. It is fundamentally important to deposit a sufficient thickness of roof material (e.g. silicon nitride) so that the nozzle plate is not overly brittle.
• Deposition is not problematic when depositing onto planar structures; however, as will be appreciated from Figures 24-27, deposition of roof material 20 must also form sidewalls 22 of nozzle chambers 24.
• the SAC2 scaffold 16 may have sloped walls (not shown in Figure 24) to assist with deposition of roof material into sidewall regions 17.
• the roof 21 (which forms the nozzle plate 101) is first planarized. Planarization is achieved by depositing an additional layer of photoresist (e.g. about 10 microns thickness) onto the roof 21, which fills all the cavities 102. Typically, this photoresist is then thermally re flowed to ensure that the cavities 102 are completely filled.
• photoresist e.g. about 10 microns thickness
• the layer of photoresist is then removed back to the level of the roof 21 so that the upper surface of the roof 21 and the upper surface of photoresist 103 deposited in the cavities 102 together form a contiguous planar surface.
• Photoresist removal can be performed by any suitable technique, such as chemical- mechanical planarization (CMP) or controlled photoresist etching (e.g. O 2 plasma).
• CMP chemical- mechanical planarization
• O 2 plasma controlled photoresist etching
• the next stage deposits additional roof material (e.g. 1 micron thick layer) by PECVD onto the planar structure shown in Figure 37.
• additional roof material e.g. 1 micron thick layer
• PECVD PECVD
• the resultant unit cell has a first roof 21 A and a second roof 2 IB.
• the exterior second roof 2 IB is fully planar by virtue of its deposition onto a planar structure.
• the second roof 2 IB is reinforced by the underlying photoresist 103 filling the cavities 102 in the first roof 2 IA.
• This reinforced bi-layered roof structure is mechanically very robust compared to the single roof structure shown in Figure 27.
• the increased thickness and internozzle reinforcement improves the general robustness of the roof structure.
• the planarity of the exterior second roof 2 IB provides improved robustness with respect to sheer forces across the roof.
• the first and second roofs 21 A and 2 IB may be comprised of the same or different materials.
• the first and second roofs are comprised of materials independently selected from the group comprising: silicon nitride, silicon oxide and silicon oxynitride.
• the first roof 21 A is comprised of silicon nitride and the second roof is comprised of silicon oxide.
• the resultant printhead integrated circuit having a planar, bi-layered reinforced nozzle plate, is shown in Figure 40.
• the nozzle plate comprises a first nozzle plate 101 A and an exterior second nozzle plate 10 IB, which is completely planar save for the nozzle rims and nozzle apertures.
• This printhead integrated circuit according to the present invention facilitates printhead maintenance operations. Its improved mechanical integrity means that relatively robust cleaning techniques (e.g. wiping) may be used without damaging the printhead. Furthermore, the absence of cavities 102 in the exterior second nozzle plate 102B minimizes the risk of particulates or ink becoming trapped permanently on the printhead. It will, of course, be appreciated that the present invention has been described purely by way of example and that modifications of detail may be made within the scope of the invention, which is defined by the accompanying claims.

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• 2007
  • 2007-10-24 WO PCT/AU2007/001618 patent/WO2009052543A1/en active Application Filing
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