Process for forming inkjet nozzle chambers

Abstract

An inkjet nozzle device includes a main chamber having a floor, a roof and a perimeter wall extending between the floor and the roof The main chamber includes: a firing chamber having a nozzle aperture defined in the roof and an actuator for ejection of ink through the nozzle aperture; an antechamber for supplying ink to the firing chamber, the antechamber having a main chamber inlet defined in the floor; and a baffle structure partitioning the main chamber to define the firing chamber and the antechamber, the baffle structure extending between the floor and the roof. The firing chamber and the antechamber have a common plane of symmetry.

Claims

1. (canceled)

2. (canceled)

3. (canceled)

4. (canceled)

5. (canceled)

6. (canceled)

7. (canceled)

8. (canceled)

9. (canceled)

10. (canceled)

11. A process for forming an inkjet chamber over a hole defined in a frontside surface of a wafer substrate, said process comprising the steps of: (i) laminating a layer of dry film photoresist onto the frontside surface defining the hole, such that the layer of dry film photoresist bridges over a void space of the hole; (ii) defining, using a photoimaging process,- wall openings corresponding to chamber walls in the dry film photoresist; (iii) depositing chamber material into the wall openings and over the dry film photoresist so as to form chamber walls and a chamber roof; (iv) defining a nozzle opening in the chamber roof; and (v) removing the dry film photoresist to form the inkjet chamber over the hole, wherein the chamber material is selected from the group consisting of: silicon oxide, silicon nitride and silicon oxynitride.

12. The process of claim 11, wherein the frontside surface comprises a bonded heater device.

13. The process of claim 11 further comprising additional MEMS fabrication steps.

14. The process of claim 13, wherein a respective inlet for the inkjet chamber is defined by the hole.

15. The process of claim 14, further comprising at least one of: backside wafer thinning and backside etching of ink supply channels.

16. The process of claim 15, wherein the process forms a plurality of inkjet chambers and each ink supply channel meets with one or more of the holes.

17. The process of claim 16, wherein each ink supply channel is relatively wider than each hole.

18. The process of claim 17, wherein the nozzle opening is aligned or offset from the hole.

19. The process of claim 11, wherein the inkjet chamber comprises a firing chamber having the nozzle opening and an antechamber having the hole, the firing chamber being laterally connected to the antechamber.

20. The process of claim 19, wherein the chamber walls define a perimeter wall of the inkjet chamber.

21. The process of claim 11, wherein the layer of dry film photoresist has a thickness in the range of 5 to 20 microns.

22. The process of claim 11, wherein the dry film photoresist comprises an epoxy resin.

23. The process of claim 11, wherein the deposition step (iii) is performed using at least one deposition method selected from the group consisting of: TEOS CVD; high density plasma CVD (HDPCVD); and plasma-enhanced CVD (PECVD).

24. The process of claim 23, wherein the deposition step (iii) comprises the sub-steps of: (a) depositing, using a first deposition method, a first chamber material to fill the wall openings, thereby forming the chamber walls and at least partially forming the chamber roof; and (b) planarizing an upper surface of the first chamber material.

25. The process of claim 24 comprising the further sub-step of: (a) depositing, using a second deposition method, a second chamber material over the planarized upper surface of the first chamber material so as to complete formation of the chamber roof.

26. The process of claim 25, wherein the first and second chamber materials are the same as each other.

27. The process of claim 25, the first and second deposition methods are the same as each other.

28. The process of claim 24, wherein the planarizing is performed using chemical-mechanical-planarization (CMP).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0033] FIG. 1 is a schematic side view of a silicon substrate having a hole etched in frontside surface;

[0034] FIG. 2 shows the substrate shown in FIG. 1 after lamination of a dry film layer;

[0035] FIG. 3 shows the substrate shown in FIG. 2 after photoetching of the dry film layer;

[0036] FIG. 4 shows the substrate shown in FIG. 3 after deposition of chamber material;

[0037] FIG. 5 shows the substrate shown in FIG. 4 after etching of the chamber material;

[0038] FIG. 6 shows the substrate shown in FIG. 5 after oxidative removal of the dry film layer;

[0039] FIG. 7 is a perspective of inkjet nozzle devices suitable for formation via the MEMS process flow shown in FIGS. 1 to 6;

[0040] FIG. 8 is a sectional side view of the inkjet nozzle device shown in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

MEMS Process Flow for Forming Inkjet Chambers

[0041] FIGS. 1 to 6 show schematically an exemplary MEMS process flow for forming inkjet chambers 70 according to the first aspect. Although the process is shown with reference to one unit cell of a wafer substrate, it will be appreciated that the process may be used to form a plurality (typically thousands) of identical unit cells on a single wafer substrate. The wafer is typically diced after completion of the MEMS processes to provide individual printhead chips, as known in the art.

[0042] In FIG. 1, there is a shown a silicon substrate 50 having a frontside hole 52 formed in a frontside surface 54 of the substrate. The frontside hole 52 typically has a depth of at least 10 microns (e.g. 10 to 50 microns) and an aspect ratio of greater than 1:1. Referring to FIG. 2, in a first step, a thin layer of photoimageable dry film photoresist 56 is laminated onto the frontside surface 54 of the substrate 50. The lamination process may be optimized, as is known in the art, to minimize sagging of the dry film photoresist 56 into the frontside hole 52. The layer of dry film photoresist 56 may have a thickness in the range of 5 to 15 microns.

[0043] In a second step, and referring now to FIG. 3, wall openings 58 are defined in the dry film photoresist 56 using a photoimaging (photoetching) process. Typically, the dry film photoresist is a negative resist dry film whereby unexposed regions of the film are dissolved by a photoresist developer to define the wall openings 58.

[0044] In a third step, and referring now to FIG. 4, a chamber material is deposited using a CVD process so as to fill the wall openings 58, thereby forming chamber walls 62 and a chamber roof 60. For example, a TEOS deposition may be used to fill the wall openings 58 with a silicon oxide chamber material. Alternatively, a high density plasma oxide deposition may be used to fill the wall openings 58 with a silicon oxide chamber material.

[0045] The dry film photoresist 56 may be thermally and/or UV cured prior to the relatively high temperature deposition step. Of course, other suitable depositable chamber materials (e.g. silicon nitride) may be used to form the chamber walls 62 and chamber roof 60.

[0046] The chamber walls 62 and chamber roof 60 may be co-formed in a single deposition step. Alternatively, the chamber walls 62 may be formed via an initial deposition filling the wall openings 58 following by a planarization step using chemical-mechanical-planarization (CMP). Following CMP, a subsequent deposition step may be used to thicken the chamber roof 60 to a desired thickness. A two-stage deposition process with CMP advantageously provides a more planar roof structure, which assists with providing more controlled nozzle etching in a subsequent step and, consequently, minimizes any undesirable nozzle size variation. A planar nozzle plate is also advantageous for printhead wiping.

[0047] It will be readily apparent that the chamber walls 62 and chamber roof 60 may be formed of the same or different materials using the two-stage deposition process in order to provide optimal characteristics for the inkjet chamber. Likewise, the first and second deposition steps may be performed using the same or different deposition methods in order to optimize inkjet chamber characteristics.

[0048] With the chamber roof 60 and chamber walls 62 formed, a nozzle opening 66 is defined in the chamber roof during a fourth step, as shown in FIG. 5. The nozzle opening 66 is formed using conventional photolithographic masking and etching steps, as known in the art.

[0049] Finally, in a fifth step shown in FIG. 6, the dry film photoresist 56 is removed via, for example, oxidative ashing to form the inkjet chamber 70 positioned over the frontside hole 52. Thus, in the novel MEMS process flow described herein, the dry film photoresist 56 is used as a sacrificial scaffold for forming the chamber roof 60 and chamber walls 62 via deposition of a ceramic material. In this way, highly robust inkjet chambers 70 may be formed over frontside holes 52 using ceramic materials without requiring filling and planarizing of the frontside holes. Moreover, any unashed dry film photoresist 56 trapped in cavities provide additional rigidity and support for a nozzle plate 68 spanning between chamber roofs 60.

[0050] In FIG. 6, the nozzle opening 66 is aligned with the frontside hole 52, although it will of course be appreciated that the nozzle opening may be offset from the frontside hole, depending on the particular configuration of the inkjet nozzle device.

[0051] After frontside MEMS fabrication steps are completed, the wafer substrate 50 is typically thinned from a backside and an ink supply channel (not shown) is etched from the backside to meet with the frontside holes 52, thereby providing fluidic connection between the backside and frontside of the wafer substrate.

MEMS Inkjet Nozzle Devices

[0052] By way of completeness, there will now be described an inkjet nozzle device 10, which may be fabricated using the MEMS process described above.

[0053] Referring to FIGS. 7 and 8, there is shown the inkjet nozzle device 10 comprising a main chamber 12 having a floor 14, a roof 16 and a perimeter wall 18 extending between the floor and the roof. FIG. 7 shows a CMOS layer 20, which may comprise a plurality of metal layers interspersed with interlayer dielectric (ILD) layers.

[0054] In FIG. 7 the roof 16 is shown as a transparent layer so as to reveal details of each nozzle device 10. Typically, the roof 16 and perimeter walls 18 are comprised of a ceramic material, such as silicon dioxide or silicon nitride.

[0055] The main chamber 12 of the nozzle device 10 comprises a firing chamber 22 and an antechamber 24. The firing chamber 22 comprises a nozzle aperture 26 defined in the roof 16 and an actuator in the form of a resistive heater element 28 bonded to the floor 14. The antechamber 24 comprises a main chamber inlet 30 (or floor inlet 30) defined in the floor 14. The main chamber inlet 30 meets and partially overlaps with an endwall 18B of the antechamber 24. This arrangement optimizes the capillarity of the antechamber 24, thereby encouraging priming and optimizing chamber refill rates.

[0056] A baffle plate 32 partitions the main chamber 12 so as to define the firing chamber 22 and the antechamber 24. The baffle plate 32 extends between the floor 14 and the roof 16.

[0057] The antechamber 24 fluidically communicates with the firing chamber 22 via a pair of firing chamber entrances 34 which flank the baffle plate 32 on either side thereof. Each firing chamber entrance 34 is defined by a gap extending between a respective side edge of the baffle plate 32 and the perimeter wall 18.

[0058] The nozzle aperture 26 is elongate and takes the form of an ellipse having a major axis aligned with a central longitudinal axis of the heater element.

[0059] As best shown in FIG. 8, the heater element 28 is connected at each end thereof to respective electrodes 36 exposed through the floor 14 of the main chamber 12 by one or more vias 37. Typically, the electrodes 36 are defined by an upper metal layer of the CMOS layer 20. The heater element 28 may be comprised of, for example, titanium-aluminium alloy, titanium aluminium nitride etc. In one embodiment, the heater 28 may be coated with one or more protective layers, as known in the art.

[0060] The vias 37 may be filled with any suitable conductive material (e.g. copper, tungsten etc.) to provide electrical connection between the heater element 28 and the electrodes 36. A suitable process for forming electrode connections from the heater element 28 to the electrodes 36 is described in U.S. Pat. No. 8,453,329, the contents of which are incorporated herein by reference.

[0061] Part of each electrode 36 may be positioned directly beneath an end wall 18A and baffle plate 32 respectively. This arrangement advantageously improves the overall symmetry of the device 10, as well as minimizing the risk of the heater element 28 delaminating from the floor 14.

[0062] A printhead chip 100 may be comprised of a plurality of inkjet nozzle devices 10, although the partial cutaway view of the printhead chip 100 in FIG. 7 shows only two inkjet nozzle devices 10 for clarity. The printhead chip 100 is defined by a printhead substrate 102 having the passivated CMOS layer 20 and a MEMS layer containing the inkjet nozzle devices 10. As shown in FIG. 7, each main chamber inlet 30 meets with an ink supply channel 104 defined in a backside of the printhead chip 100. The ink supply channel 104 is generally much wider than the main chamber inlets 30 and provides a bulk supply of ink for hydrating each main chamber 12 in fluid communication therewith. Each ink supply channel 104 extends parallel with one or more rows of nozzle devices 10 disposed at a frontside of the printhead chip 100. Typically, each ink supply channel 104 supplies ink to a pair of nozzle rows (only one row shown in FIG. 7 for clarity), in accordance with the arrangement shown in FIG. 21B of U.S. Pat. No. 7,441,865, the contents of which are incorporated herein by reference.

[0063] As foreshadowed above, the printhead chip 100 may be fabricated by building the MEMS layer containing inkjet nozzle devices 10 on a wafer substrate using a modified MEMS process flow based on the process described in connection with FIGS. 1 to 6. In the modified MEMS process flow, the baffle plate 32 is formed at the same time as the chamber walls 62 and chamber roof 60 by filling a suitable baffle opening (not shown) defined in the dry film photoresist 56. Accordingly, the process described herein provides an alternative to prior art processes for forming ceramic inkjet chambers over a frontside hole, which obviates filling and planarizing steps and thereby reduces the overall cost of printhead chip fabrication.

[0064] It will, of course, be appreciated that the present invention has been described by way of example only and that modifications of detail may be made within the scope of the invention, which is defined in the accompanying claims.