Inkjet printhead

Abstract

This inkjet print head includes: an actuator substrate that has an ink flow passage including a pressure chamber; a movable film forming layer that includes a movable film, said movable film being positioned on the pressure chamber and demarcating a top surface section of the pressure chamber; a piezoelectric element that includes a lower electrode positioned on the movable film, a piezoelectric body film formed on the lower electrode, and an upper electrode formed on the piezoelectric body film; a hydrogen barrier film that, among the surfaces of the piezoelectric element, covers at least the entire side surfaces of the upper electrode and the piezoelectric body film; an interlayer insulating film that is formed on the movable film forming layer so as to cover the hydrogen barrier film; and wiring that is formed on the interlayer insulating film and is connected to the piezoelectric element, wherein a fuse is inserted partway along the wiring.

Description

[Technical Field]

[0001] The present disclosure relates to inkjet printheads. [Background technology]

[0002] Patent Document 1 discloses an inkjet printhead. The inkjet printhead of Patent Document 1 includes an actuator substrate having pressure chambers as ink flow paths, a movable membrane formed on the actuator substrate, and a piezoelectric element provided on the movable membrane. The inkjet printhead of Patent Document 1 also includes a nozzle substrate bonded to the lower surface of the actuator substrate and having nozzle holes communicating with the pressure chambers, and a protection substrate bonded to the upper surface of the actuator substrate and covering the piezoelectric element. The piezoelectric element consists of a lower electrode formed on the movable membrane, an upper electrode placed on the lower electrode, and a piezoelectric film sandwiched between them. One end of a wiring is connected to the upper electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-69685 Summary of the Invention [Problem to be solved by the invention]

[0004] In the inkjet printhead described in Patent Document 1, when dielectric breakdown occurs in a piezoelectric element, an excessive current flows through the wiring, generating Joule heat in the wiring. This Joule heat can damage the movable film and cause ink leakage. Since inkjet printheads are equipped with multiple piezoelectric elements, if dielectric breakdown in one piezoelectric element causes ink leakage, the wiring connected to adjacent piezoelectric elements deteriorates, leading to the problem of expanding the range of the failure.

[0005] The object of the present disclosure is to provide an inkjet print head that can prevent excessive current from continuing to flow through the wiring in the event of insulation breakdown of the piezoelectric element, etc., and can suppress damage to the movable film due to Joule heat generated in the wiring. [Means for solving the problem]

[0006] One embodiment of the present disclosure provides an inkjet printhead including: an actuator substrate having an ink flow path including a pressure chamber; a movable film forming layer disposed over the pressure chamber and including a movable film that defines a ceiling portion of the pressure chamber; a piezoelectric element including a lower electrode disposed on the movable film, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film; a hydrogen barrier film covering at least the entire side surface of the upper electrode and the piezoelectric film among the surfaces of the piezoelectric element; an interlayer insulating film formed on the movable film forming layer so as to cover the hydrogen barrier film; and wiring formed on the interlayer insulating film and connected to the piezoelectric element, wherein a fuse is inserted in the middle of the wiring.

[0007] With this configuration, if the piezoelectric element experiences dielectric breakdown, for example, it is possible to prevent excessive current from continuing to flow through the wiring, and to suppress damage to the movable film due to Joule heat generated in the wiring.

[0008] In one embodiment of the present disclosure, the actuator substrate has a cavity below the fuse.

[0009] In one embodiment of the present disclosure, the fuse is made of a conductor made of the same material as the wiring and having a smaller width than the wiring.

[0010] In one embodiment of the present disclosure, the wiring has a first wiring portion and a second wiring portion electrically connected via the fuse, the first wiring portion has a first end connected to the piezoelectric element and a second end connected to the fuse, the second wiring portion has a first end connected to the fuse and a second end opposite the first end, and the fuse is composed of a conductor, a first contact connecting the second end of the first wiring portion to the first end of the conductor, and a second contact connecting the first end of the second wiring portion to the second end of the conductor opposite the first end.

[0011] In one embodiment of the present disclosure, the wiring is an upper wiring having one end connected to the upper electrode of the piezoelectric element, a dummy piezoelectric element having the same structure as the piezoelectric element but not operating as a piezoelectric element is formed on the movable film formation layer, and the conductor is the upper electrode of the dummy piezoelectric element.

[0012] In an embodiment of the present disclosure, the hydrogen barrier film and the interlayer insulating film cover the surface of the dummy piezoelectric element.

[0013] In one embodiment of the present disclosure, the hydrogen barrier film and the interlayer insulating film are formed on at least a portion of the upper surface of the upper electrode of the piezoelectric element, an upper contact hole is formed in the hydrogen barrier film and the interlayer insulating film formed on the upper surface of the upper electrode of the piezoelectric element, exposing a portion of the upper surface of the upper electrode of the piezoelectric element, a first end of the first wiring portion enters the upper contact hole and is connected to the upper electrode within the upper contact hole, a first contact hole exposing a portion of the first end of the conductor and a second contact hole exposing a portion of the second end of the conductor are formed in the hydrogen barrier film and the interlayer insulating film formed on the upper surface of the conductor consisting of the upper electrode of the dummy piezoelectric element, the first contact connects the second end of the first wiring portion to the first end of the conductor via the first contact hole, and the second contact connects the first end of the second wiring portion to the second end of the conductor via the second contact hole.

[0014] In one embodiment of the present disclosure, when the portion of the first wiring portion connected to the upper electrode through the upper contact hole is defined as an upper contact, the cross-sectional area of ​​at least one of the first contact and the second contact is smaller than the cross-sectional area of ​​the upper contact.

[0015] In one embodiment of the present disclosure, the width of the conductor is smaller than the width of the upper wiring.

[0016] In one embodiment of the present disclosure, the wiring is an upper wiring having one end connected to the upper electrode of the piezoelectric element, and the conductor is composed of a metal film formed on the movable film forming layer and made of the same material as the lower electrode.

[0017] In one embodiment of the present disclosure, the hydrogen barrier film and the interlayer insulating film cover the surface of the conductor.

[0018] In one embodiment of the present disclosure, the hydrogen barrier film and the interlayer insulating film are formed on at least a portion of the upper surface of the upper electrode of the piezoelectric element, an upper contact hole is formed in the hydrogen barrier film and the interlayer insulating film formed on the upper surface of the upper electrode of the piezoelectric element, exposing a portion of the upper surface of the upper electrode of the piezoelectric element, a first end of the first wiring portion enters the upper contact hole and is connected to the upper electrode within the upper contact hole, a first contact hole exposing a portion of the first end of the conductor and a second contact hole exposing a portion of the second end of the conductor are formed in the hydrogen barrier film and the interlayer insulating film formed on the upper surface of the conductor, the first contact connects the second end of the first wiring portion to the first end of the conductor via the first contact hole, and the second contact connects the first end of the second wiring portion to the second end of the conductor via the second contact hole.

[0019] In one embodiment of the present disclosure, when the portion of the first wiring portion connected to the upper electrode through the upper contact hole is defined as an upper contact, the cross-sectional area of ​​at least one of the first contact and the second contact is smaller than the cross-sectional area of ​​the upper contact.

[0020] In one embodiment of the present disclosure, the width of the conductor is smaller than the width of the upper wiring.

[0021] In one embodiment of the present disclosure, the semiconductor device further includes a passivation film formed on the interlayer insulating film and covering the wiring.

[0022] In one embodiment of the present disclosure, a plurality of pressure chambers are provided, a piezoelectric element is provided for each of the pressure chambers, and the actuator substrate is formed with a plurality of pressure chamber rows, each row consisting of a plurality of the pressure chambers spaced apart in a predetermined first direction in a plan view, spaced apart in a second direction perpendicular to the first direction.

[0023] The above and other objects, features, and advantages of the present disclosure will become apparent from the following description of the embodiments with reference to the accompanying drawings. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic plan view for explaining the configuration of an inkjet printhead according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic partially enlarged plan view showing an enlarged portion C of FIG. 1, and is a plan view including a protection substrate. [Figure 3] FIG. 3 is a schematic partially enlarged plan view showing an enlarged C portion of FIG. 1, in which the protective substrate is omitted. [Figure 4A] FIG. 4A is a schematic cross-sectional view taken along line AA in FIG. [Figure 4B] FIG. 4B is a schematic cross-sectional view taken along line BB in FIG. [Figure 5]FIG. 5 is a schematic cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a schematic plan view showing an example of a pattern of an insulating film of the inkjet print head of FIG. 1, and corresponds to FIG. [Figure 8] FIG. 8 is a schematic plan view showing an example of a pattern of the passivation film of the inkjet print head of FIG. 1, and corresponds to FIG. [Figure 9] FIG. 9 is a bottom view of the area of ​​the protection substrate shown in FIG. [Figure 10] FIG. 10 is a plan view of a semiconductor wafer as an original substrate for the actuator substrate. [Figure 11A] 11A is a cross-sectional view showing an example of a manufacturing process for the inkjet printhead of FIG. [Figure 11B] FIG. 11B is a cross-sectional view showing the next step of FIG. 11A. [Figure 11C] FIG. 11C is a cross-sectional view showing the step subsequent to that of FIG. 11B. [Figure 11D] FIG. 11D is a cross-sectional view showing the step subsequent to that of FIG. 11C. [Figure 11E] FIG. 11E is a cross-sectional view showing the step subsequent to that of FIG. 11D. [Figure 11F] FIG. 11F is a cross-sectional view showing the step subsequent to FIG. 11E. [Figure 11G] FIG. 11G is a cross-sectional view showing the step subsequent to FIG. 11F. [Figure 11H] FIG. 11H is a cross-sectional view showing the step subsequent to FIG. 11G. [Figure 11I] FIG. 11I is a cross-sectional view showing the step subsequent to FIG. 11H. [Figure 11J] FIG. 11J is a cross-sectional view showing the step subsequent to that of FIG. 11I. [Figure 11K] FIG. 11K is a cross-sectional view showing the step subsequent to that of FIG. 11J. [Figure 12A]12A is a cross-sectional view showing an example of a manufacturing process for the inkjet printhead of FIG. [Figure 12B] FIG. 12B is a cross-sectional view showing the next step of FIG. 12A. [Figure 12C] FIG. 12C is a cross-sectional view showing the next step of FIG. 12B. [Figure 12D] FIG. 12D is a cross-sectional view showing the step subsequent to that of FIG. 12C. [Figure 12E] FIG. 12E is a cross-sectional view showing the step subsequent to that of FIG. 12D. [Figure 12F] FIG. 12F is a cross-sectional view showing the step subsequent to that of FIG. 12E. [Figure 12G] FIG. 12G is a cross-sectional view showing the step subsequent to FIG. 12F. [Figure 12H] FIG. 12H is a cross-sectional view showing the step subsequent to FIG. 12F. [Figure 12I] FIG. 12I is a cross-sectional view showing the step subsequent to FIG. 12H. [Figure 12J] FIG. 12J is a cross-sectional view showing the step subsequent to that of FIG. 12I. [Figure 12K] FIG. 12K is a cross-sectional view showing the step following FIG. 12J. [Figure 13] FIG. 13 is a schematic plan view for explaining the configuration of an inkjet printhead according to the second embodiment of the present disclosure. [Figure 14] FIG. 14 is a schematic partially enlarged plan view showing an enlarged portion C of FIG. 13, and is a plan view including a protection substrate. [Figure 15] FIG. 15 is a schematic partially enlarged plan view showing an enlarged portion C of FIG. 13, in which the protection substrate is omitted. [Figure 16A] FIG. 16A is a schematic cross-sectional view taken along line AA in FIG. [Figure 16B] FIG. 16B is a schematic cross-sectional view taken along line BB in FIG. [Figure 17A] 17A is a cross-sectional view showing an example of a manufacturing process for the inkjet printhead of FIG. [Figure 17B]FIG. 17B is a cross-sectional view showing the next step of FIG. 17A. [Figure 17C] FIG. 17C is a cross-sectional view showing the step subsequent to that of FIG. 17B. [Figure 17D] FIG. 17D is a cross-sectional view showing the step subsequent to FIG. 17C. [Figure 17E] FIG. 17E is a cross-sectional view showing the step subsequent to that of FIG. 17D. [Figure 17F] FIG. 17F is a cross-sectional view showing the step subsequent to that of FIG. 17E. [Figure 17G] FIG. 17G is a cross-sectional view showing the step following FIG. 17F. [Figure 17H] FIG. 17H is a cross-sectional view showing the step subsequent to FIG. 17G. [Figure 17I] FIG. 17I is a cross-sectional view showing the step following FIG. 17H. [Figure 17J] FIG. 17J is a cross-sectional view showing the step subsequent to that of FIG. 17I. [Figure 18A] 18A is a cross-sectional view showing an example of a manufacturing process for the inkjet printhead of FIG. [Figure 18B] FIG. 18B is a cross-sectional view showing the next step of FIG. 18A. [Figure 18C] FIG. 18C is a cross-sectional view showing the step subsequent to that of FIG. 18B. [Figure 18D] FIG. 18D is a cross-sectional view showing the step subsequent to that of FIG. 18C. [Figure 18E] FIG. 18E is a cross-sectional view showing the step subsequent to that of FIG. 18D. [Figure 18F] FIG. 18F is a cross-sectional view showing the step subsequent to that of FIG. 18E. [Figure 18G] FIG. 18G is a cross-sectional view showing the step following FIG. 18F. [Figure 18H] FIG. 18H is a cross-sectional view showing the step subsequent to FIG. 18G. [Figure 18I] FIG. 18I is a cross-sectional view showing the step following FIG. 18H. [Figure 18J] FIG. 18J is a cross-sectional view showing the step subsequent to that of FIG. 18I. [Figure 19]FIG. 19 is a schematic plan view for explaining the configuration of an inkjet printhead according to a third embodiment of the present disclosure. [Figure 20] FIG. 20 is a schematic partially enlarged plan view showing an enlarged portion C of FIG. 19, and is a plan view including a protection substrate. [Figure 21] FIG. 21 is a schematic partially enlarged plan view showing an enlarged portion C of FIG. 19, in which the protection substrate is omitted. [Figure 22A] FIG. 22A is a schematic cross-sectional view taken along line AA in FIG. [Figure 22B] FIG. 22B is a schematic cross-sectional view taken along line BB in FIG. [Figure 23A] 23A is a cross-sectional view showing an example of a manufacturing process for the inkjet printhead of FIG. [Figure 23B] FIG. 23B is a cross-sectional view showing the next step of FIG. 23A. [Figure 23C] FIG. 23C is a cross-sectional view showing the step subsequent to that of FIG. 23B. [Figure 23D] FIG. 23D is a cross-sectional view showing the step subsequent to that of FIG. 23C. [Figure 23E] FIG. 23E is a cross-sectional view showing the step following that of FIG. 23D. [Figure 23F] FIG. 23F is a cross-sectional view showing the step following that of FIG. 23E. [Figure 23G] FIG. 23G is a cross-sectional view showing the step following FIG. 23F. [Figure 23H] FIG. 23H is a cross-sectional view showing the step subsequent to that of FIG. 23G. [Figure 23I] FIG. 23I is a cross-sectional view showing the step following FIG. 23H. [Figure 23J] FIG. 23J is a cross-sectional view showing the step following that of FIG. 23I. [Figure 24A] 24A is a cross-sectional view showing an example of a manufacturing process for the inkjet printhead of FIG. [Figure 24B] FIG. 24B is a cross-sectional view showing the step subsequent to that of FIG. 24A. [Figure 24C]FIG. 24C is a cross-sectional view showing the step subsequent to that of FIG. 24B. [Figure 24D] FIG. 24D is a cross-sectional view showing the step subsequent to that of FIG. 24C. [Figure 24E] FIG. 24E is a cross-sectional view showing the step subsequent to that of FIG. 24D. [Figure 24F] FIG. 24F is a cross-sectional view showing the step subsequent to that of FIG. 24E. [Figure 24G] FIG. 24G is a cross-sectional view showing the step following FIG. 24F. [Figure 24H] FIG. 24H is a cross-sectional view showing the step subsequent to that of FIG. 24G. [Figure 24I] FIG. 24I is a cross-sectional view showing the step following FIG. 24H. [Figure 24J] FIG. 24J is a cross-sectional view showing the step following that of FIG. 24H. DETAILED DESCRIPTION OF THE INVENTION

[0025] [1] First embodiment FIG. 1 is a schematic plan view illustrating the configuration of an inkjet printhead according to a first embodiment of the present disclosure. FIG. 2 is a schematic partially enlarged plan view showing an enlargement of portion C of FIG. 1, including a protective substrate. FIG. 3 is a schematic partially enlarged plan view showing an enlargement of portion C of FIG. 1, omitting the protective substrate. FIG. 4A is a schematic cross-sectional view taken along line AA of FIG. 2. FIG. 4B is a schematic cross-sectional view taken along line BB of FIG. 2. FIG. 5 is a schematic cross-sectional view taken along line VV of FIG. 2. FIG. 6 is a schematic cross-sectional view taken along line VI-VI of FIG. 2.

[0026] The structure of the inkjet printhead 1 will be explained briefly with reference to FIGS. 4A and 4B.

[0027] The inkjet printhead 1 comprises an actuator substrate assembly SA including an actuator substrate 2 and a piezoelectric element 9, a nozzle substrate 3, and a protection substrate 4. Hereinafter, the actuator substrate assembly SA will be referred to as the "substrate assembly SA".

[0028] The actuator substrate 2 is made of, for example, a silicon (Si) substrate. A movable film formation layer 10 is laminated on a surface 2a of the actuator substrate 2. An ink flow path (ink reservoir) 5 and a cavity 19 are formed in the actuator substrate 2. In this embodiment, the ink flow path 5 is formed to penetrate the actuator substrate 2. The ink flow path 5 is formed to extend elongatedly along the ink flow direction 41 indicated by the arrow in FIGS. 4A and 4B. The ink flow path 5 is composed of an ink inlet section 6 at the upstream end (the left end in FIG. 4A) of the ink flow direction 41, and a pressure chamber 7 communicating with the ink inlet section 6. In FIG. 4A, the boundary between the ink inlet section 6 and the pressure chamber 7 is indicated by a two-dot chain line.

[0029] The cavity 19 is disposed downstream of the ink flow path 5 in the ink flow direction 41. In this embodiment, the cavity 19 is formed so as to penetrate the actuator substrate 2. The cavity 19 is formed to extend along the ink flow direction 41. The cavity 19 is formed below an area including a fuse 20 (described later) and its vicinity.

[0030] The nozzle substrate 3 is made of, for example, a silicon (Si) substrate. The nozzle substrate 3 is bonded to the rear surface 2b of the actuator substrate 2. The nozzle substrate 3, together with the actuator substrate 2 and the movable film formation layer 10, defines the ink flow path 5. More specifically, the nozzle substrate 3 defines the bottom surface of the ink flow path 5. The nozzle substrate 3, together with the actuator substrate 2 and the movable film formation layer 10, also defines a cavity 19. More specifically, the nozzle substrate 3 defines the bottom surface of the cavity 19. A nozzle hole 3a is formed in the nozzle substrate 3. The nozzle hole 3a has an ink ejection port 3b on the side opposite to the pressure chamber 7.

[0031] The ceiling wall portion of the pressure chamber 7 in the movable film formation layer 10 constitutes the movable film 10A. The movable film 10A (movable film formation layer 10) is made of, for example, a silicon oxide (SiO2) film formed on the actuator substrate 2. In this specification, the movable film 10A refers to the ceiling wall portion of the movable film formation layer 10 that defines the ceiling portion of the pressure chamber 7. Therefore, the portion of the movable film formation layer 10 other than the ceiling wall portion of the pressure chamber 7 does not constitute the movable film 10A.

[0032] The thickness of the movable film 10A is, for example, 0.4 μm to 2 μm, and may be approximately 1.2 μm.

[0033] The pressure chamber 7 is defined by the movable film 10A, the actuator substrate 2, and the nozzle substrate 3, and in this embodiment is formed in a generally rectangular parallelepiped shape that is long in the ink flow direction 41. The length of the pressure chamber 7 may be, for example, about 800 μm, and its width may be about 55 μm. The ink inlet 6 communicates with one longitudinal end of the pressure chamber 7.

[0034] A first hydrogen barrier film 8 is formed on the surface of the movable film formation layer 10. The first hydrogen barrier film 8 is made of, for example, Al2O3 (alumina). The first hydrogen barrier film 8 has a thickness of approximately 50 nm to 100 nm. A piezoelectric element 9 is disposed on the surface of the first hydrogen barrier film 8 above the movable film 10A. The piezoelectric element 9 includes a lower electrode 11 formed on the first hydrogen barrier film 8, a piezoelectric film 12 formed on the lower electrode 11, and an upper electrode 13 formed on the piezoelectric film 12. In other words, the piezoelectric element 9 is formed by sandwiching the piezoelectric film 12 between the upper electrode 13 and the lower electrode 11 from above and below.

[0035] The upper electrode 13 may be a single film of platinum (Pt), or may have a laminated structure in which, for example, a conductive oxide film (for example, an IrO2 (iridium oxide) film) and a metal film (for example, an Ir (iridium) film) are laminated. The thickness of the upper electrode 13 may be, for example, about 0.2 μm.

[0036] The piezoelectric film 12 is made of, for example, PZT (PbZr x Ti 1-x O3: lead zirconate titanate) film can be applied. Such a piezoelectric film 12 is made of a sintered body of metal oxide crystal. The piezoelectric film 12 is formed to have the same shape as the upper electrode 13 in a plan view. The thickness of the piezoelectric film 12 is about 1 μm. It is preferable that the overall thickness of the movable film 10A is about the same as the thickness of the piezoelectric film 12 or about two-thirds the thickness of the piezoelectric film 12.

[0037] The first hydrogen barrier film 8 described above prevents deterioration of the characteristics of the piezoelectric film 12 due to hydrogen reduction. Furthermore, the first hydrogen barrier film 8 prevents metal elements (Pb, Zr, Ti when the piezoelectric film 12 is PZT) from escaping from the piezoelectric film 12, maintaining good piezoelectric characteristics of the piezoelectric film 12, and preventing metal from diffusing into the movable film 10A when the piezoelectric film 12 is formed.

[0038] The lower electrode 11 has a two-layer structure in which, for example, a Ti (titanium) film and a Pt (platinum) film are laminated in this order from the first hydrogen barrier film 8 side. Alternatively, the lower electrode 11 can be formed of a single film such as an Au (gold) film, a Cr (chromium) layer, or a Ni (nickel) layer. The lower electrode 11 has a main electrode portion 11A in contact with the lower surface of the piezoelectric film 12 and an extension portion 11B extending to an area outside the piezoelectric film 12. The thickness of the lower electrode 11 may be, for example, about 0.2 μm.

[0039] A second hydrogen barrier film 14 is formed on the piezoelectric element 9, the extension 11B of the lower electrode 11, and the first hydrogen barrier film 8. The second hydrogen barrier film 14 is made of, for example, Al2O3 (alumina). The second hydrogen barrier film 14 has a thickness of approximately 50 nm to 100 nm. The second hydrogen barrier film 14 is provided to prevent deterioration of the characteristics of the piezoelectric film 12 due to hydrogen reduction. The second hydrogen barrier film 14 is an example of the "hydrogen barrier film" in the present disclosure.

[0040] An insulating film 15 is laminated on the second hydrogen barrier film 14. The insulating film 15 is made of, for example, SiO2, low-hydrogen SiN, or the like. The thickness of the insulating film 15 is about 500 nm. An upper wiring 17 and a lower wiring 18 (see FIGS. 2 and 6) are formed on the insulating film 15. These wirings may be made of a metal material containing Al (aluminum). The thickness of these wirings is, for example, about 1000 nm (1 μm).

[0041] A fuse 20 is inserted in the middle of the upper wiring 17, and is blown when an excessive current flows through the upper wiring 17. The upper wiring 17 has a first wiring portion 17A and a second wiring portion 17B that are connected via the fuse 20. With reference to FIGS. 2 and 3, in a plan view, the fuse 20 has a rectangular shape that is long in the ink flow direction 41. The fuse 20 is made of the same material as the upper wiring, and is composed of a conductor that is the same thickness as the upper wiring 17 and narrower in width than the upper wiring 17. The first wiring portion 17A, the fuse 20, and the second wiring portion 17B are integrally formed.

[0042] As described above, the actuator substrate 2 has a cavity 19 formed below a region including the fuse 20 and its vicinity. The cavity 19 is disposed downstream of the ink flow path 5 in the ink flow direction 41. The cavity 19 has a generally rectangular parallelepiped shape that is long in the ink flow direction 41. In plan view, the cavity 19 has a rectangular shape that extends long along the ink flow direction 41. In other words, the top surface of the cavity 19 has two side edges that are aligned with the ink flow direction 41 and two end edges that are aligned in a direction perpendicular to the ink flow direction 41.

[0043] The width of the cavity 19 is larger than the width of the fuse 20 and larger than the width of the upper wiring 17. In this embodiment, the width of the cavity 19 is approximately equal to the width of the pressure chamber 7. The length of the cavity 19 is larger than the length of the fuse 20. In this embodiment, the length of the cavity 19 is shorter than the length of the pressure chamber 7. In a plan view, both side edges along the longitudinal direction of the fuse 20 are set back more inward than the corresponding side edges of the cavity 19. In a plan view, both end edges along the lateral direction of the fuse 20 are set back more inward than the corresponding end edges of the cavity 19.

[0044] The reason why the cavity 19 is formed in the actuator substrate 2 is as follows: If the cavity 19 were not provided, even if an excessive current flows through the upper wiring 17 and causes the fuse 20 to generate heat, the heat would escape through the actuator substrate 2 made of a Si substrate, making it difficult for the fuse 20 to blow. Therefore, the cavity 19 is formed to prevent the heat generated in the fuse 20 from escaping through the actuator substrate 2 when an excessive current flows through the upper wiring 17.

[0045] One end (first end) of the first wiring portion 17A is disposed above one end (downstream end in the ink flow direction 41) of the upper electrode 13. A contact hole 31 is formed between the first wiring portion 17A and the upper electrode 13, continuously penetrating the second hydrogen barrier film 14 and the insulating film 15. One end of the first wiring portion 17A enters the contact hole 31 and is connected to the upper electrode 13 within the contact hole 31.

[0046] The first wiring portion 17A extends from above the upper electrode 13, across the outer edge of the pressure chamber 7, and outward from the pressure chamber 7. The other end (second end) of the first wiring portion 17A is connected to one end (first end) of the fuse 20. More specifically, one end of the fuse 20 is connected to a widthwise intermediate portion of the other end of the first wiring portion 17A. One end (first end) of the second wiring portion 17B is connected to the other end (second end) of the fuse 20. More specifically, the other end of the fuse 20 is connected to a widthwise intermediate portion of one end of the second wiring portion 17B. The second wiring portion 17B extends along an extension of the first wiring portion 17A. The lower wiring 18 will be described later.

[0047] A passivation film 33 is formed on the insulating film 15, covering the upper interconnect 17, the lower interconnect 18, the fuse 20, and the insulating film 15. The passivation film 33 is made of, for example, SiN (silicon nitride). The thickness of the passivation film 33 may be, for example, about 800 nm.

[0048] A pad opening 34 exposing a portion of the second wiring portion 17B is formed in the passivation film 33. The pad opening 34 is formed in a region downstream of the cavity 19 in the ink flow direction 41, for example, at the tip end of the second wiring portion 17B (the end opposite the end connected to the fuse 20). An upper electrode pad 42 covering the pad opening 34 is formed on the passivation film 33. The upper electrode pad 42 enters the pad opening 34 and is connected to the second wiring portion 17B within the pad opening 34. A lower electrode pad 43 (see FIGS. 1, 2, 3, and 6) is also provided for the lower wiring 18, but the lower electrode pad 43 will be described later.

[0049] An ink supply through hole 44 is formed at a position corresponding to the end of the ink flow path 5 on the ink inlet section 6 side, penetrating the passivation film 33, the insulating film 15, the second hydrogen barrier film 14, the first hydrogen barrier film 8, and the movable film formation layer 10. The ink supply through hole 44 is in communication with the ink inlet section 6.

[0050] The protective substrate 4 is made of, for example, a silicon substrate. The protective substrate 4 is disposed on the substrate assembly SA so as to cover the piezoelectric element 9 and the fuse 20. The protective substrate 4 is bonded to the substrate assembly SA via an adhesive 50. The protective substrate 4 has a first recess 52 and a second recess 53 on an opposing surface 51 facing the substrate assembly SA. The piezoelectric element 9 is housed in the first recess 52. The second recess 53 faces the fuse 20 and its surrounding area. The second recess 53 is formed to prevent heat from the fuse 20 from escaping through the protective substrate 4 when an overcurrent flows through the upper wiring 17.

[0051] Furthermore, the protective substrate 4 is formed with an ink supply path 54 that communicates with the ink supply through-hole 44 and an opening 55 for exposing the pads 42 and 43. The ink supply path 54 and the opening 55 pass through the protective substrate 4. An ink tank (not shown) that stores ink is disposed on the protective substrate 4.

[0052] The piezoelectric element 9 is formed at a position facing the pressure chamber 7 with the movable film 10A and the first hydrogen barrier film 8 sandwiched between them. In other words, the piezoelectric element 9 is formed so as to contact the surface of the first hydrogen barrier film 8 opposite the pressure chamber 7. The pressure chamber 7 is filled with ink by being supplied to the pressure chamber 7 from the ink tank through the ink supply path 54, the ink supply through hole 44, and the ink inlet portion 6. The movable film 10A defines the top surface of the pressure chamber 7 and faces the pressure chamber 7. The movable film 10A is supported by the portion of the actuator substrate 2 surrounding the pressure chamber 7, and has flexibility that allows it to deform in the direction facing the pressure chamber 7 (in other words, the thickness direction of the movable film 10A).

[0053] The lower wiring 18 (see Figures 2, 3, and 6) and the upper wiring 17 are connected to a drive circuit (not shown). Specifically, the upper electrode pad 42 and the drive circuit are connected via a connecting metal member (not shown). The lower electrode pad 43 (see Figures 2, 3, and 6) and the drive circuit are connected via a connecting metal member (not shown). When a drive voltage is applied from the drive circuit to the piezoelectric element 9, the piezoelectric film 12 deforms due to the inverse piezoelectric effect. This causes the piezoelectric element 9 and the movable film 10A to deform, which changes the volume of the pressure chamber 7 and pressurizes the ink in the pressure chamber 7. The pressurized ink passes through the nozzle hole 3a and is ejected as microdroplets from the ink ejection port 3b.

[0054] The configuration of the inkjet printhead 1 will be described in more detail with reference to Figures 1 to 6. In the following description, the left side of Figure 1 will be referred to as the "left," the right side of Figure 1 as the "right," the lower side of Figure 1 as the "front," and the upper side of Figure 1 as the "rear."

[0055] 1, the inkjet printhead 1 has a rectangular shape in plan view. In this embodiment, the planar shapes and sizes of the actuator substrate 2, protection substrate 4, and nozzle substrate 3 are approximately the same as those of the inkjet printhead 1.

[0056] On the actuator substrate 2, in plan view, a plurality of rows of piezoelectric elements 9 (hereinafter referred to as "piezoelectric element rows") are arranged in stripes spaced apart in the front-rear direction, and a plurality of rows are provided spaced apart in the left-right direction. In this embodiment, for the sake of convenience, it is assumed that two rows of piezoelectric elements are provided.

[0057] 2 and 3, an ink flow path 5 (pressure chamber 7) is formed on the actuator substrate 2 for each piezoelectric element 9. Therefore, in a plan view, the actuator substrate 2 is provided with two ink flow path rows (pressure chamber rows) spaced apart in the left-right direction, each row consisting of a plurality of ink flow paths 5 (pressure chambers 7) arranged in stripes at intervals in the front-to-rear direction.

[0058] The pattern of the ink flow path array corresponding to the piezoelectric element array on the left side of Figure 1 and the pattern of the ink flow path array corresponding to the piezoelectric element array on the right side are symmetrical with respect to the line connecting the centers of the arrays. Therefore, in the ink flow paths 5 included in the left ink flow path array, the ink inlet section 6 is on the right side of the pressure chambers 7 (piezoelectric elements 9), while in the ink flow paths 5 included in the right ink flow path array, the ink inlet section 6 is on the left side of the pressure chambers 7 (piezoelectric elements 9). Therefore, the ink flow directions 41 are opposite to each other in the left ink flow path array and the right ink flow path array.

[0059] An ink supply through hole 44 is provided for each of the multiple ink flow paths 5 in each ink flow path row. The ink supply through holes 44 are arranged on the ink inlet section 6. Therefore, the ink supply through hole 44 for the ink flow paths 5 included in the left ink flow path row is arranged on the right end of the ink flow path 5, and the ink supply through hole 44 for the ink flow paths 5 included in the right ink flow path row is arranged on the left end of the ink flow path 5.

[0060] A cavity 19 is provided for each of the plurality of ink flow paths 5 in each ink flow path row. The cavity 19 corresponding to the left ink flow path row is disposed on the left side of the ink flow paths 5, and the cavity 19 corresponding to the right ink flow path row is disposed on the right side of the ink flow paths 5.

[0061] In each ink flow path row, the ink flow paths 5 are formed at equal intervals in the width direction with minute gaps (for example, about 30 μm to 350 μm) between them. Similarly, in each ink flow path row, the cavities 19 are formed at equal intervals in the width direction with minute gaps between them.

[0062] Each ink flow path 5 extends in an elongated shape along the ink flow direction 41. The ink flow path 5 is composed of an ink inlet section 6 that communicates with an ink supply through hole 44 and a pressure chamber 7 that communicates with the ink inlet section 6. In plan view, the pressure chamber 7 has an elongated rectangular shape that extends along the ink flow direction 41. That is, the top surface of the pressure chamber 7 has two side edges that are aligned with the ink flow direction 41 and two end edges that are aligned with a direction perpendicular to the ink flow direction 41. The ink inlet section 6 has approximately the same width as the pressure chamber 7 in plan view. The inner surface of the end of the ink inlet section 6 opposite the pressure chamber 7 is formed in a semicircular shape in plan view. The ink supply through hole 44 is circular in plan view (see particularly Figure 3).

[0063] In a plan view, the piezoelectric element 9 has a rectangular shape that is long in the longitudinal direction of the pressure chamber 7 (movable membrane 10A). The end of the piezoelectric element 9 on the ink supply through hole 44 side is formed in a semicircular shape in a plan view. The longitudinal length of the piezoelectric element 9 is shorter than the longitudinal length of the pressure chamber 7 (movable membrane 10A). As shown in FIG. 3, both end edges along the lateral direction of the piezoelectric element 9 are arranged inward from the corresponding end edges of the movable membrane 10A with a predetermined distance therebetween. In addition, the width of the piezoelectric element 9 in the lateral direction is narrower than the width of the movable membrane 10A. Both end edges along the longitudinal direction of the piezoelectric element 9 are arranged inward from the corresponding end edges of the movable membrane 10A with a predetermined distance therebetween.

[0064] A lower electrode 11 is provided for each piezoelectric element row. The lower electrode 11 provided for the left piezoelectric element row (hereinafter sometimes referred to as the "first lower electrode 11") is a common electrode shared by the multiple piezoelectric elements 9 in the left piezoelectric element row. The lower electrode 11 provided for the right piezoelectric element row (hereinafter sometimes referred to as the "second lower electrode 11") is a common electrode shared by the multiple piezoelectric elements 9 in the right piezoelectric element row.

[0065] 2 and 3, the second lower electrode 11, in plan view, is composed of a first rectangular region 61 including the plurality of piezoelectric elements 9 in the right-side piezoelectric element row, and a second rectangular region 62 extending rightward from the rear end of the first rectangular region 61. The second lower electrode 11 includes a main electrode portion 11A that is rectangular in plan view and constitutes each piezoelectric element 9 in the right-side piezoelectric element row, and an extension portion 11B that is drawn out from the main electrode portion 11A in a direction along the surface of the movable film formation layer 10 and extends outward from the periphery of the top surface of the pressure chamber 7.

[0066] The first lower electrode 11 has a planar shape that is symmetrical to the second lower electrode 11 with respect to a line passing through the center between the left-side piezoelectric element row and the right-side piezoelectric element row. In a planar view, the first lower electrode 11 consists of a first rectangular region that includes the piezoelectric elements 9 of the left-side piezoelectric element row, and a second rectangular region that extends leftward from the rear end of the first rectangular region. The first lower electrode 11 includes a main electrode portion 11A that is rectangular in a planar view and constitutes each piezoelectric element 9 of the left-side piezoelectric element row, and an extension portion 11B that is drawn from the main electrode portion 11A in a direction along the surface of the movable membrane formation layer 10 and extends outward from the periphery of the top surface of the pressure chamber 7.

[0067] In the first lower electrode 11 and the second lower electrode 11, the longitudinal length of the main electrode portion 11A is shorter than the longitudinal length of the movable film 10A. Both end edges of the main electrode portion 11A are disposed inward with a gap between them and the corresponding end edges of the movable film 10A. The lateral width of the main electrode portion 11A is narrower than the lateral width of the movable film 10A. Both side edges of the main electrode portion 11A are disposed inward with a gap between them and the corresponding side edges of the movable film 10A. In the first lower electrode 11, the extension portion 11B is a region of the entire area of ​​the first lower electrode 11 excluding the main electrode portion 11A. In the second lower electrode 11, the extension portion 11B is a region of the entire area of ​​the second lower electrode 11 excluding the main electrode portion 11A.

[0068] In plan view, the upper electrode 13 is formed in a rectangular shape with the same pattern as the main electrode portion 11A of the lower electrode 11. That is, the longitudinal length of the upper electrode 13 is shorter than the longitudinal length of the movable film 10A. Both end edges of the upper electrode 13 are arranged inward with a gap between them and the corresponding end edges of the movable film 10A. Furthermore, the width of the upper electrode 13 in the lateral direction is narrower than the width of the movable film 10A. Both end edges of the upper electrode 13 are arranged inward with a gap between them and the corresponding end edges of the movable film 10A.

[0069] The piezoelectric film 12 is formed in a rectangular shape in the same pattern as the upper electrode 13 in a plan view. That is, the longitudinal length of the piezoelectric film 12 is shorter than the longitudinal length of the movable film 10A. Both end edges of the piezoelectric film 12 are arranged on the inside with a gap between them and the corresponding end edges of the movable film 10A. Furthermore, the width of the piezoelectric film 12 in the lateral direction is narrower than the width of the movable film 10A. Both side edges of the piezoelectric film 12 are arranged on the inside with a gap between them and the corresponding side edges of the movable film 10A. The lower surface of the piezoelectric film 12 contacts the upper surface of the main electrode portion 11A of the lower electrode 11, and the upper surface of the piezoelectric film 12 contacts the lower surface of the upper electrode 13.

[0070] The first wiring portion 17A of the upper wiring 17 extends from the upper surface of one end of the piezoelectric element 9 (the end on the downstream side in the ink flow direction 41) along the end face of the piezoelectric element 9 connected to it, and further extends downstream in the ink flow direction 41 along the surface of the insulating film 15. The other end of the first wiring portion 17A is connected to one end of the fuse 20. The other end of the fuse 20 is connected to one end of the second wiring portion 17B of the upper wiring 17. The other end of the second wiring portion 17B extends downstream in the ink flow direction 41 and is disposed within the opening 55 of the protective substrate 4.

[0071] A pad opening 34 exposing the center of the tip surface of the second wiring portion 17B is formed in the passivation film 33. An upper electrode pad 42 is provided on the passivation film 33 so as to cover the pad opening 34. The upper electrode pad 42 is connected to the second wiring portion 17B within the pad opening 34.

[0072] The upper electrode pads 42 corresponding to the piezoelectric elements 9 in the left-side piezoelectric element row are arranged in a line in the front-to-rear direction on the left side of the left-side piezoelectric element row in a plan view, as shown in Fig. 1. The upper electrode pads 42 corresponding to the piezoelectric elements 9 in the right-side piezoelectric element row are arranged in a line in the front-to-rear direction on the right side of the right-side piezoelectric element row in a plan view.

[0073] 1, 2, 3, and 6, the lower wiring 18 includes a lower wiring (hereinafter sometimes referred to as a "first lower wiring 18") arranged behind the left row of upper electrode pads in a plan view, and a lower wiring (hereinafter sometimes referred to as a "second lower wiring 18") arranged behind the right row of upper electrode pads. Each lower wiring 18 has a rectangular shape in a plan view.

[0074] An extension 11B (second rectangular region) of the first lower electrode 11 exists below the first lower interconnection 18. An extension 11B (second rectangular region 62) of the second lower electrode 11 exists below the second lower interconnection 18. A contact hole 32 is formed between the lower interconnection 18 and the extension 11B of the lower electrode 11 located thereunder, continuously penetrating the second hydrogen barrier film 14 and the insulating film 15. The lower interconnection 18 enters the contact hole 32 and is connected to the extension 11B of the lower electrode 11 within the contact hole 32.

[0075] A pad opening 35 that exposes the center of the surface of the lower wiring 18 is formed in the passivation film 33. A lower electrode pad 43 that covers the pad opening 35 is formed on the passivation film 33. The lower electrode pad 43 enters the pad opening 35 and is connected to the lower wiring 18 within the pad opening 35.

[0076] As shown in FIGS. 1, 2, 4A, and 4B, the protective substrate 4 is formed with a plurality of ink supply paths 54 (hereinafter sometimes referred to as "first ink supply paths 54") that communicate with a plurality of ink supply through holes 44 for the left ink flow path row, and a plurality of ink supply paths 54 (hereinafter sometimes referred to as "second ink supply paths 54") that communicate with a plurality of ink supply through holes 44 for the right ink flow path row. The first ink supply paths 54 are arranged in a line spaced apart in the front-to-rear direction, shifted to the left with respect to the center of the width of the protective substrate 4 in a plan view. The second ink supply paths 54 are arranged in a line spaced apart in the front-to-rear direction, shifted to the right with respect to the center of the width of the protective substrate 4 in a plan view. The ink supply paths 54 are circular in shape in a plan view, with the same pattern as the ink supply through holes 44 of the substrate assembly SA. The ink supply paths 54 are aligned with the ink supply through holes 44 in a plan view.

[0077] Furthermore, openings 55 are formed in the protective substrate 4 to expose all of the upper electrode pads 42 corresponding to the left-side piezoelectric element row and the left-side lower electrode pads 43. Furthermore, openings 55 are formed in the protective substrate 4 to expose all of the upper electrode pads 42 corresponding to the right-side piezoelectric element row and the right-side lower electrode pads 43. These openings 55 are rectangular in shape and are long in the front-to-rear direction in plan view.

[0078] FIG. 9 is a bottom view of the area of ​​the protection substrate shown in FIG.

[0079] 2, 4A, 4B, 5, and 9, first recesses 52 are formed on the opposing surface 51 of the protection substrate 4 facing the actuator substrate 2 at positions facing the piezoelectric elements 9 in each piezoelectric element row. Second recesses 53 are also formed on the opposing surface 51 of the protection substrate 4 at positions facing the fuses 20 corresponding to each piezoelectric element row in each piezoelectric element row. The second recesses 53 are located downstream of the first recesses 52 in the ink flow direction 41.

[0080] An ink supply path 54 is disposed upstream of each first recess 52 in the ink flow direction 41. An opening 55 is disposed downstream of each second recess 53 in the ink flow direction 41. In plan view, each first recess 52 is formed in a rectangular shape that is slightly larger than the pattern of the upper electrode 13 of the corresponding piezoelectric element 9. A corresponding piezoelectric element 9 is housed in each first recess 52. In plan view, each second recess 53 is formed in a rectangular shape that is larger than the pattern of the corresponding fuse 20. A corresponding fuse 20 faces each second recess 53.

[0081] 7 and 8 are schematic plan views showing examples of patterns of an insulating film and a passivation film of the inkjet printhead, respectively.

[0082] In this embodiment, the insulating film 15 and the passivation film 33 are formed on the actuator substrate 2 over almost the entire area outside the first recess 52 of the protection substrate 4 in a plan view. However, in this area, the insulating film 15 has an ink supply through hole 44 and a contact hole 32 formed therein. In this area, the passivation film 33 has an ink supply through hole 44 and pad openings 34 and 35 formed therein.

[0083] In the region inside the first recess 52 of the protective substrate 4, the insulating film 15 and the passivation film 33 are formed only at one end (upper wiring region) where the upper wiring 17 is present. In this region, the passivation film 33 is formed so as to cover the top and side surfaces of the upper wiring 17 on the insulating film 15. In other words, an opening 36 is formed in the insulating film 15 and the passivation film 33 in a region excluding the upper wiring region within the region inside the first recess 52 in a plan view. A contact hole 31 is further formed in the insulating film 15.

[0084] An outline of a method for manufacturing the inkjet printhead 1 will now be described.

[0085] FIG. 10 is a plan view of a semiconductor wafer as the original substrate of the actuator substrate, showing an enlarged view of a part of the wafer.

[0086] The semiconductor wafer (actuator wafer) 100 serving as the original substrate of the actuator substrate 2 is made of, for example, a silicon wafer. A surface 100a of the actuator wafer 100 corresponds to the surface 2a of the actuator substrate. A plurality of functional element forming regions 101 are arranged in a matrix on the surface 100a of the actuator wafer 100. Scribe regions (boundary regions) 102 are provided between adjacent functional element forming regions 101. The scribe regions 102 are strip-shaped regions with a substantially constant width, and are formed in a grid pattern extending in two perpendicular directions. Planned cutting lines 103 are set in the scribe regions 102. By performing the necessary processes on the actuator wafer 100, a substrate assembly aggregate (SA aggregate) 110 (see Figures 11H and 12H) is created in which the ink flow paths 5 and cavities 19 are not formed but the components of the substrate assemblies SA are formed on each functional element forming region 101.

[0087] A protective substrate aggregate 130 (see FIGS. 11I and 12I) is prepared in advance, which integrally includes a plurality of protective substrates 4 corresponding to each functional element forming region 101 of the substrate assembly aggregate 110. The protective substrate aggregate 130 is produced by performing necessary processes on a semiconductor wafer (protective substrate wafer) that serves as the original substrate for the protective substrate 4. The protective substrate wafer is made of, for example, a silicon wafer.

[0088] Also, a nozzle substrate aggregate 150 (see FIGS. 11K and 12K) is prepared in advance, which integrally includes a plurality of nozzle substrates 3 corresponding to each functional element formation region 101 of the substrate assembly aggregate 110. The nozzle substrate aggregate 150 is produced by performing the necessary processes on a semiconductor wafer (nozzle wafer) which serves as the original substrate for the nozzle substrates 3. The nozzle wafer is made of, for example, a silicon wafer.

[0089] After the substrate assembly aggregate 110 is created, the protective substrate aggregate 130 is bonded to the substrate assembly aggregate 110. Next, ink channels 5 and cavities 19 are formed in the substrate assembly aggregate 110. Next, the nozzle substrate aggregate 150 is bonded to the substrate assembly aggregate 110. As a result, an inkjet printhead aggregate 170 (see Figures 11K and 12K) consisting of the substrate assembly aggregate 110, the protective substrate aggregate 130, and the nozzle substrate aggregate 150 is obtained. Thereafter, the inkjet printhead aggregate 170 is cut (diced) along the planned cutting lines 103 with a dicing blade. As a result, individual inkjet printheads (chips) 1 including functional element forming regions 101 are cut out. The inkjet printhead 1 has a scribe region 102 on the periphery and the functional element forming region 101 in the central region surrounded by the scribe region 102.

[0090] A method for manufacturing the inkjet printhead 1 will now be described in detail.

[0091] 11A to 11K and 12A to 12K are cross-sectional views showing the manufacturing process of the inkjet printhead 1. Figures 11A to 11K are cross-sectional views corresponding to the cross section of Figure 4A, and Figures 12A to 12K are cross-sectional views corresponding to the cross section of Figure 4B.

[0092] First, as shown in Figures 11A and 12A, an actuator wafer 100 is prepared. However, the actuator wafer 100 used is thicker than the final actuator substrate 2. Then, a movable film formation layer 10 is formed on the surface 100a of the actuator wafer 100. Specifically, a silicon oxide film (for example, 1.2 µm thick) is formed on the surface 100a of the actuator wafer 100.

[0093] Next, a first hydrogen barrier film 8 is formed on the movable film formation layer 10. The first hydrogen barrier film 8 is made of, for example, an Al2O3 film (for example, 50 nm to 100 nm thick). The first hydrogen barrier film 8 prevents deterioration of the characteristics of the piezoelectric film 12, which will be formed later, due to hydrogen reduction. The first hydrogen barrier film 8 also prevents metal atoms from escaping from the piezoelectric film 12. If metal electrons escape, the piezoelectric characteristics of the piezoelectric film 12 may deteriorate. Furthermore, if the escaping metal atoms become mixed into the silicon layer that constitutes the movable film 10A, the durability of the movable film 10A may deteriorate.

[0094] Next, a lower electrode film 71, which is a material layer for the lower electrode 11, is formed on the first hydrogen barrier film 8. The lower electrode film 71 is made of, for example, a Pt / Ti laminated film having a Ti film (for example, 10 nm to 40 nm thick) as a lower layer and a Pt film (for example, 10 nm to 400 nm thick) as an upper layer. Such a lower electrode film 71 may be formed by a sputtering method.

[0095] Next, a piezoelectric material film 72, which is the material of the piezoelectric film 12, is formed on the entire surface of the lower electrode film 71. Specifically, for example, the piezoelectric material film 72 is formed to a thickness of 1 μm to 3 μm by a sol-gel method. Such a piezoelectric material film 72 is made of a sintered body of metal oxide crystal grains.

[0096] Next, an upper electrode film 73, which is the material of the upper electrode 13, is formed on the entire surface of the piezoelectric material film 72. The upper electrode film 73 may be, for example, a platinum (Pt) single film. The upper electrode film 73 may be, for example, an IrO2 / Ir laminated film having an IrO2 film (for example, 40 nm to 160 nm thick) as a lower layer and an Ir film (for example, 40 nm to 160 nm thick) as an upper layer. Such an upper electrode film 73 may be formed by sputtering.

[0097] 11B and 12B, the upper electrode film 73, the piezoelectric material film 72, and the lower electrode film 71 are patterned. First, a resist mask of the pattern of the upper electrode 13 is formed by photolithography. Then, using this resist mask as a mask, the upper electrode film 73 and the piezoelectric material film 72 are successively etched, thereby forming the upper electrode 13 and the piezoelectric film 12 in a predetermined pattern.

[0098] Next, after the resist mask is peeled off, a resist mask having a pattern of the lower electrode 11 is formed by photolithography. Then, using this resist mask as a mask, the lower electrode film 71 is etched to form the lower electrode 11 having a predetermined pattern. This forms the lower electrode 11 consisting of the main electrode portion 11A and the extension portion 11B. In this way, the piezoelectric element 9 consisting of the main electrode portion 11A of the lower electrode 11, the piezoelectric film 12, and the upper electrode 13 is formed.

[0099] 11C and 12C, after the resist mask is removed, a second hydrogen barrier film 14 is formed to cover the entire surface. The second hydrogen barrier film 14 may be an Al2O3 film formed by sputtering, and may have a thickness of 50 nm to 100 nm. After this, an insulating film 15 is formed on the entire surface of the second hydrogen barrier film 14. The insulating film 15 may be a SiO2 film, and may have a thickness of 200 nm to 300 nm. Subsequently, the insulating film 15 and the second hydrogen barrier film 14 are successively etched to form contact holes 31 and 32.

[0100] 11D and 12D, a wiring film constituting upper wiring 17, fuse 20, and lower wiring 18 is formed by sputtering on insulating film 15 including the insides of contact holes 31 and 32. Thereafter, the wiring film is patterned by photolithography and etching, thereby simultaneously forming upper wiring 17 (first wiring portion 17A and second wiring portion 17B), fuse 20, and lower wiring 18.

[0101] 11E and 12E, a passivation film 33 is formed on the surface of the insulating film 15 to cover the upper wiring 17, the fuse 20, and the lower wiring 18. The passivation film 33 is made of, for example, SiN. The passivation film 33 is formed by, for example, plasma CVD.

[0102] Next, a resist mask having openings corresponding to the pad openings 34 and 35 is formed by photolithography, and the passivation film 33 is etched using this resist mask. As a result, the pad openings 34 and 35 are formed in the passivation film 33, as shown in Figures 11F and 12F. After the resist mask is peeled off, the upper electrode pad 42 and the lower electrode pad 43 are formed on the passivation film 33 through the pad openings 34 and 35, respectively.

[0103] Next, a resist mask having openings corresponding to the opening 36 and the ink supply through hole 44 is formed by photolithography, and the passivation film 33 and the insulating film 15 are successively etched using this resist mask. As a result, the opening 36 and the ink supply through hole 44 are formed in the passivation film 33 and the insulating film 15, as shown in FIGS. 11G and 12G.

[0104] Next, the resist mask is peeled off. Then, a resist mask having openings corresponding to the ink supply through holes 44 is formed by photolithography, and the second hydrogen barrier film 14, the first hydrogen barrier film 8, and the movable film formation layer 10 are etched using this resist mask. As a result, as shown in Figures 11H and 12H, the ink supply through holes 44 are formed in the second hydrogen barrier film 14, the first hydrogen barrier film 8, and the movable film formation layer 10. In this way, the substrate assembly aggregate 110 is produced.

[0105] Next, as shown in Figures 11I and 12I, adhesive 50 is applied to the opposing surface 51 of the protective substrate assembly 130, and the protective substrate assembly 130 is fixed to the substrate assembly assembly 110 so that the ink supply path 54 and the corresponding ink supply through hole 44 are aligned.

[0106] Next, as shown in FIGS. 11J and 12J, backside grinding is performed to thin the actuator wafer 100. The actuator wafer 100 is thinned by polishing the backside 100b. For example, the actuator wafer 100, which is initially approximately 670 μm thick, may be thinned to approximately 300 μm thick. After this, a resist mask having openings corresponding to the ink flow paths 5 (ink inlet portions 6 and pressure chambers 7) and the cavities 19 is formed on the backside 100b of the actuator wafer 100 by photolithography. The resist mask is then used as a mask to etch the actuator wafer 100 from the backside 100b. As a result, the ink flow paths 5 (ink inlet portions 6 and pressure chambers 7) and the cavities 19 are formed in the actuator wafer 100.

[0107] During this etching, the first hydrogen barrier film 8 formed on the surface of the movable film formation layer 10 prevents metal elements (Pb, Zr, Ti in the case of PZT) from escaping from the piezoelectric film 12, thereby maintaining good piezoelectric properties of the piezoelectric film 12. As described above, the first hydrogen barrier film 8 also contributes to maintaining the durability of the silicon layer that forms the movable film 10A.

[0108] 11K and 12K, the nozzle substrate aggregate 150 is attached to the back surface 100b of the actuator wafer 100. This results in an inkjet printhead aggregate 170 consisting of the substrate assembly aggregate 110, the protective substrate aggregate 130, and the nozzle substrate aggregate 150. The inkjet printhead aggregate 170 is then cut along the planned cutting lines 103 with a dicing blade. In other words, a process is performed to cut out the inkjet printheads 1 individually.

[0109] When this process is complete, the actuator wafer 100 in the substrate assembly aggregate 110 becomes the actuator substrate 2 of each inkjet printhead 1. Furthermore, the protection substrate aggregate 130 becomes the protection substrate 4 of each inkjet printhead 1. Furthermore, the nozzle wafer 140 in the nozzle substrate aggregate 150 becomes the silicon substrate of the nozzle substrate 3 of each inkjet printhead 1. In this way, individual inkjet printheads 1 having the structure shown in FIGS. 1 to 6 are obtained.

[0110] In the inkjet printhead 1 obtained in this manner, the side surfaces of the actuator substrate 2 and the nozzle substrate 3 are flush in all directions (flush around the entire periphery) in a plan view. That is, in this embodiment, an inkjet printhead 1 is obtained in which there is no step between the actuator substrate 2 and the nozzle substrate 3. Also in this embodiment, the side surfaces of the actuator substrate 2 and the protective substrate 4 are also flush in all directions (flush around the entire periphery) in a plan view. That is, in this embodiment, an inkjet printhead 1 is obtained in which there is no step between the actuator substrate 2 and the protective substrate 4 either.

[0111] In the method for manufacturing an inkjet printhead according to this embodiment, the nozzle substrate aggregate 150 is bonded to the substrate assembly aggregate 110, to which the protection substrate aggregate 130 is fixed, to create the inkjet printhead aggregate 170. The inkjet printhead aggregate 170 is then diced to cut out the individual inkjet printheads 1. This makes it possible to manufacture the inkjet printhead 1 more efficiently than, for example, manufacturing the individual substrate assemblies SA and then bonding the nozzle substrates 3 to the individual substrate assemblies SA to manufacture the inkjet printhead.

[0112] In the inkjet printhead 1 according to this embodiment, when dielectric breakdown occurs in one piezoelectric element 9, an excessive current flows in the upper wiring 17 of that piezoelectric element 9. However, because the fuse 20 is provided midway through the upper wiring 17, the fuse 20 is heated and blown. This prevents an excessive current from continuing to flow through the upper wiring 17, thereby suppressing damage to the movable film caused by Joule heat generated in the upper wiring 17 and suppressing ink leakage. This prevents the upper wiring 17 connected to other adjacent piezoelectric elements 9 from being deteriorated by ink, and suppresses the expansion of the failure area. [2] Second embodiment Fig. 13 is a plan view of an inkjet printhead according to a second embodiment of the present disclosure, and is a plan view corresponding to Fig. 1. Fig. 14 is a schematic, partially enlarged plan view showing an enlargement of part C of Fig. 13, including a protective substrate. Fig. 15 is a schematic, partially enlarged plan view showing an enlargement of part C of Fig. 13, omitting the protective substrate. Fig. 16A is a schematic cross-sectional view of region A in the cross-sectional view taken along line AA of Fig. 14. Fig. 16B is a schematic cross-sectional view of region B in the cross-sectional view taken along line BB of Fig. 14.

[0113] In Fig. 13, parts corresponding to the parts in Fig. 1 described above are denoted by the same reference numerals as in Fig. 1. In Fig. 14, parts corresponding to the parts in Fig. 2 described above are denoted by the same reference numerals as in Fig. 2. In Fig. 15, parts corresponding to the parts in Fig. 3 described above are denoted by the same reference numerals as in Fig. 3. In Figs. 16A and 16B, parts corresponding to the parts in Figs. 4A and 4B described above are denoted by the same reference numerals as in Figs. 4A and 4B.

[0114] The inkjet printhead 1A according to the second embodiment is different from the inkjet printhead 1 according to the first embodiment in the configuration of the fuse 20. Specifically, the fuse 20 is made up of a conductor 21 formed from the upper electrode 213 of the dummy piezoelectric element 209, a first contact 22 connecting one end (first end) of the conductor 21 to the other end (second end) of the first wiring portion 17A of the upper wiring 17, and a second contact 23 connecting the other end (second end) of the conductor 21 to one end (first end) of the second wiring portion 17B of the upper wiring 17.

[0115] The dummy piezoelectric element 209 is formed on the first hydrogen barrier film 8 above the cavity 19. The dummy piezoelectric element 209 has a structure similar to that of the piezoelectric element 9, but does not operate as a piezoelectric element. The dummy piezoelectric element 209 is composed of a lower electrode 211 formed on the first hydrogen barrier film 8, a piezoelectric film 212 formed on the lower electrode 211, and an upper electrode 213 formed on the piezoelectric film 212. The upper electrode 213 is connected to the upper wiring 17, but the lower electrode 211 is not connected to the lower wiring.

[0116] In a plan view, the lower electrode 211 has a rectangular shape that is long in the length direction of the cavity 19, and both end edges are formed in a curved shape that protrudes outward. In a plan view, the width of the lower electrode 211 in the short side direction is approximately equal to the width of the upper electrode 13 of the piezoelectric element 9 in the short side direction. In a plan view, both end edges of the lower electrode 211 are recessed inward from the corresponding end edges of the cavity 19. The length of the lower electrode 211 in the longitudinal direction is longer than the length of the cavity 19 in the long side direction. In a plan view, both end edges of the lower electrode 211 protrude outward from the corresponding end edges of the cavity 19.

[0117] In plan view, the upper electrode 213 has a rectangular shape that is long in the length direction of the cavity 19, and both end edges are formed in a curved shape that protrudes outward. The width in the short side direction of the upper electrode 213 is shorter than the width in the short side direction of the lower electrode 211. In plan view, both side edges of the upper electrode 213 are set back more inward than the corresponding both side edges of the lower electrode 211. The length in the longitudinal direction of the upper electrode 213 is shorter than the length in the long side direction of the cavity 19. In plan view, both end edges of the upper electrode 213 are set back more inward than the corresponding both end edges of the cavity 19.

[0118] The piezoelectric film 212 has the same pattern as the upper electrode 213 in a planar view. In a planar view, the piezoelectric film 212 has a rectangular shape that is long in the length direction of the cavity 19, and both end edges are formed in a curved shape that protrudes outward. The width in the short side direction of the piezoelectric film 212 is shorter than the width in the short side direction of the lower electrode 211. In a planar view, both side edges of the piezoelectric film 212 are set back more inward than the corresponding both side edges of the lower electrode 211. The length in the longitudinal direction of the piezoelectric film 212 is shorter than the length in the long side direction of the cavity 19. In a planar view, both end edges of the piezoelectric film 212 are set back more inward than the corresponding both end edges of the cavity 19.

[0119] The surface and side surfaces of the upper electrode 213 of the dummy piezoelectric element 209, the side surfaces of the piezoelectric film 212, and the surface and side surfaces of the lower electrode 211 are covered with a second hydrogen barrier film 14. The second hydrogen barrier film 14 is covered with an insulating film 15.

[0120] The other end of the first wiring portion 17A is disposed above one end (the upstream end in the ink flow direction 41) of the upper electrode 213. In this embodiment, the width of the upper electrode 213 in the short side direction is shorter than the width of the first wiring portion 17A (upper wiring 17). In a plan view, both side edges of one end of the upper electrode 213 are set back more inward than the corresponding both side edges of the other end of the first wiring portion 17A.

[0121] A contact hole 24 is formed between the first wiring portion 17A and the upper electrode 213, continuously penetrating the second hydrogen barrier film 14 and the insulating film 15. A first contact 22 is embedded in the contact hole 24, connecting the other end of the first wiring portion 17A to one end of the upper electrode 213 (conductor 21). The first contact 22 is formed integrally with the first wiring portion 17A.

[0122] One end of the second wiring portion 17B is disposed above the other end of the upper electrode 213. In this embodiment, the width of the upper electrode 213 in the short side direction is shorter than the width of the second wiring portion 17B (upper wiring 17). In plan view, both side edges of the other end of the upper electrode 213 are set back more inward than the corresponding both side edges of one end of the second wiring portion 17B.

[0123] A contact hole 25 is formed between the second wiring portion 17B and the upper electrode 213, continuously penetrating the second hydrogen barrier film 14 and the insulating film 15. A second contact 23 is embedded in the contact hole 25, connecting one end of the second wiring portion 17B to the other end of the upper electrode 213 (conductor 21). The second contact 23 is formed integrally with the second wiring portion 17B. It is preferable that the cross-sectional area of ​​at least one of the first contact 22 and the second contact 23 is smaller than the cross-sectional area of ​​the upper wiring portion (upper contact) in the contact hole 31. In this embodiment, the cross-sectional areas of the first contact 22 and the second contact 23 are smaller than the cross-sectional area of ​​the upper wiring portion in the contact hole 31.

[0124] In the region inside the second recess 53 of the protective substrate 4, the insulating film 15 and the passivation film 33 are formed at one end where the first wiring portion 17A is located and at the other end where the second wiring portion 17B is located, but not at the longitudinal center. In the region inside the second recess 53, the passivation film 33 is formed so as to cover the upper and side surfaces of the first wiring portion 17A on the insulating film 15 and the upper and side surfaces of the second wiring portion 17B on the insulating film 15. In other words, an opening 26 is formed in the insulating film 15 and the passivation film 33 in a region inside the second recess 53 in a plan view, excluding the upper wiring region. Contact holes 24 and 25 are further formed in the insulating film 15.

[0125] In the second embodiment, the same effects as in the first embodiment can be obtained.

[0126] In addition, as in the above-mentioned conductor 21 (upper electrode 213), if the width of the conductor 21 in the short direction is shorter than the width of the upper wiring 17 and the conductor 21 has the property of being more susceptible to melting than the upper wiring 17, the cross-sectional area of ​​the first contact 22 and the second contact 23 may be equal to or greater than the cross-sectional area of ​​the upper wiring portion within the contact hole 31.

[0127] Furthermore, if the cross-sectional area of ​​at least one of the first contact 22 and the second contact 23 is smaller than the cross-sectional area of ​​the upper wiring portion within the contact hole 31, and if at least one of the first contact 22 and the second contact 23 has a property that makes it more susceptible to melting than the upper wiring 17, the width in the short direction of the upper electrode 213 (conductor 21) may be greater than the width of the upper wiring 17.

[0128] A method for manufacturing the inkjet printhead 1A will now be described in detail.

[0129] Figures 17A to 17J and 18A to 18J are cross-sectional views showing the manufacturing process of the inkjet printhead 1A. Figures 17A to 17J are cross-sectional views corresponding to the cross section of Figure 16A, and Figures 18A to 18J are cross-sectional views corresponding to the cross section of Figure 16B.

[0130] 11A and 12A described above, the upper electrode film 73, the piezoelectric material film 72, and the lower electrode film 71 are patterned as shown in FIGS. 17A and 18A. First, a resist mask having the pattern of the upper electrodes 13, 213 is formed by photolithography. Then, using this resist mask as a mask, the upper electrode film 73 and the piezoelectric material film 72 are successively etched to form the upper electrodes 13, 233 and the piezoelectric films 12, 212 in a predetermined pattern.

[0131] Next, after the resist mask is peeled off, a resist mask is formed by photolithography in the pattern of the lower electrodes 11, 211. Then, using this resist mask as a mask, the lower electrode film 71 is etched, thereby forming the lower electrodes 11, 211 in a predetermined pattern.

[0132] The lower electrode 11 is composed of a main electrode portion 11A and an extension portion 11B. In this manner, a piezoelectric element 9 is formed, which is composed of the main electrode portion 11A of the lower electrode 11, the piezoelectric film 12, and the upper electrode 13. In addition, a dummy piezoelectric element 209 is formed, which is composed of a lower electrode 211, a piezoelectric film 212, and an upper electrode 213. The upper electrode 213 constitutes the conductor 21 of the fuse 20.

[0133] 17B and 18B, after the resist mask is removed, a second hydrogen barrier film 14 is formed to cover the entire surface. After that, an insulating film 15 is formed on the entire surface of the second hydrogen barrier film 14. Subsequently, the insulating film 15 and the second hydrogen barrier film 14 are successively etched to form contact holes 31, 32, 24, and 25.

[0134] 17C and 18C, a wiring film is formed by sputtering on insulating film 15, including inside contact holes 31, 32, 24, and 25. Thereafter, the wiring film is patterned by photolithography and etching, thereby simultaneously forming upper wiring 17 (first wiring portion 17A and second wiring portion 17B), first contact 22 and second contact 23 of fuse 20, and lower wiring 18. As a result, fuse 20 consisting of conductor 21 (upper electrode 213), first contact 22, and second contact 23 is obtained.

[0135] Next, as shown in FIGS. 17D and 18D, a passivation film 33 is formed on the surface of the insulating film 15 to cover the upper wiring 17 and the lower wiring 18.

[0136] Next, a resist mask having openings corresponding to the pad openings 34 and 35 is formed by photolithography, and the passivation film 33 is etched using this resist mask. As a result, the pad openings 34 and 35 are formed in the passivation film 33, as shown in Figures 17E and 18E. After the resist mask is peeled off, the upper electrode pad 42 and the lower electrode pad 43 are formed on the passivation film 33 through the pad openings 34 and 35, respectively.

[0137] Next, a resist mask having openings corresponding to the openings 36, 26 and the ink supply through hole 44 is formed by photolithography, and the passivation film 33 and the insulating film 15 are successively etched using this resist mask. As a result, the openings 36, 26 and the ink supply through hole 44 are formed in the passivation film 33 and the insulating film 15, as shown in Figures 17F and 18F.

[0138] Next, the resist mask is peeled off. Then, a resist mask having openings corresponding to the ink supply through holes 44 is formed by photolithography, and the second hydrogen barrier film 14, the first hydrogen barrier film 8, and the movable film formation layer 10 are etched using this resist mask. As a result, as shown in Figures 17G and 18G, the ink supply through holes 44 are formed in the second hydrogen barrier film 14, the first hydrogen barrier film 8, and the movable film formation layer 10. In this way, the substrate assembly aggregate 110 is produced.

[0139] Next, as shown in Figures 17H and 18H, adhesive 50 is applied to the opposing surface 51 of the protective substrate aggregate 130, and the protective substrate aggregate 130 is fixed to the substrate assembly aggregate 110 so that the ink supply path 54 and the corresponding ink supply through hole 44 are aligned.

[0140] Next, as shown in Figures 17I and 18I, backside grinding is performed to thin the actuator wafer 100. The actuator wafer 100 is polished from the backside 100b, thereby thinning the actuator wafer 100. Thereafter, a resist mask having openings corresponding to the ink flow paths 5 (ink inlet portions 6 and pressure chambers 7) and the cavities 19 is formed on the backside 100b side of the actuator wafer 100 by photolithography, and the actuator wafer 100 is etched from the backside 100b using this resist mask as a mask. As a result, the ink flow paths 5 (ink inlet portions 6 and pressure chambers 7) and the cavities 19 are formed in the actuator wafer 100.

[0141] 17J and 18J, the nozzle substrate aggregate 150 is attached to the rear surface 100b of the actuator wafer 100. This results in an inkjet printhead aggregate 170 consisting of the substrate assembly aggregate 110, the protective substrate aggregate 130, and the nozzle substrate aggregate 150. The inkjet printhead aggregate 170 is then cut along the planned cutting lines 103 with a dicing blade. In other words, a process is carried out to cut out the inkjet printheads 1 individually.

[0142] When this process is complete, the actuator wafers 100 in the substrate assembly aggregate 110 become the actuator substrates 2 of the individual inkjet printheads 1. Furthermore, the protection substrate aggregate 130 becomes the protection substrate 4 of the individual inkjet printheads 1. Furthermore, the nozzle wafers 140 in the nozzle substrate aggregate 150 become the silicon substrates of the nozzle substrates 3 of the individual inkjet printheads 1. In this way, individual inkjet printheads 1 having the structure shown in Figures 13 to 16B are obtained. [3] Third embodiment Fig. 19 is a plan view of an inkjet printhead according to a third embodiment of the present disclosure, and is a plan view corresponding to Fig. 1. Fig. 20 is a schematic, partially enlarged plan view showing an enlargement of part C of Fig. 19, including a protective substrate. Fig. 21 is a schematic, partially enlarged plan view showing an enlargement of part C of Fig. 19, omitting the protective substrate. Fig. 22A is a schematic cross-sectional view taken along line AA of Fig. 20. Fig. 22B is a schematic cross-sectional view taken along line BB of Fig. 20.

[0143] In Fig. 19, parts corresponding to the parts in Fig. 1 described above are denoted by the same reference numerals as in Fig. 1. In Fig. 20, parts corresponding to the parts in Fig. 2 described above are denoted by the same reference numerals as in Fig. 2. In Fig. 21, parts corresponding to the parts in Fig. 3 described above are denoted by the same reference numerals as in Fig. 3. In Figs. 22A and 22B, parts corresponding to the parts in Figs. 4A and 4B described above are denoted by the same reference numerals as in Figs. 4A and 4B.

[0144] The inkjet printhead 1B according to the third embodiment is different from the inkjet printhead 1 according to the first embodiment in the configuration of the fuse 20. Specifically, the fuse 20 is composed of a conductor 21 formed on the first hydrogen barrier film 8 and made of the same material as the lower electrode 11, a first contact 22 connecting one end (first end) of the conductor 21 to the other end (second end) of the first wiring portion 17A of the upper wiring 17, and a second contact 23 connecting the other end (second end) of the conductor 21 to one end (first end) of the second wiring portion 17B of the upper wiring 17.

[0145] In a plan view, the conductor 21 has a rectangular shape that is long in the ink flow direction 41, and both end edges are formed in a curved shape that protrudes outward. In a plan view, the conductor 21 is arranged inside the cavity 19. In a plan view, the width of the conductor 21 in the short side direction is shorter than the width of the cavity 19 in the short side direction. In a plan view, both side edges of the conductor 21 are set back more inward than the corresponding side edges of the cavity 19. The length of the conductor 21 in the longitudinal direction is shorter than the length of the cavity 19 in the long side direction. In a plan view, both end edges of the conductor 21 are set back more inward than the corresponding end edges of the cavity 19.

[0146] The surface and side surfaces of the conductor 21 are covered with a second hydrogen barrier film 14. The second hydrogen barrier film 14 is covered with an insulating film 15.

[0147] The other end of the first wiring portion 17A is disposed above one end (the upstream end in the ink flow direction 41) of the conductor 21. In this embodiment, the width of the conductor 21 in the short direction is shorter than the width of the first wiring portion 17A (upper wiring 17). In a plan view, both side edges of one end of the conductor 21 are set back more inward than the corresponding both side edges of the other end of the first wiring portion 17A.

[0148] A contact hole 24 is formed between the first wiring portion 17A and the conductor 21, continuously penetrating the second hydrogen barrier film 14 and the insulating film 15. A first contact 22 is embedded in the contact hole 24, connecting the other end of the first wiring portion 17A to one end of the conductor 21. The first contact 22 is formed integrally with the first wiring portion 17A.

[0149] One end of the second wiring portion 17B is disposed above the other end of the conductor 21. In this embodiment, the width of the conductor 21 in the short side direction is shorter than the width of the second wiring portion 17B (upper wiring 17). In a plan view, both side edges of one end of the conductor 21 are set back more inward than the corresponding both side edges of one end of the second wiring portion 17B.

[0150] A contact hole 25 is formed between the second wiring portion 17B and the conductor 21, continuously penetrating the second hydrogen barrier film 14 and the insulating film 15. A second contact 23 is embedded in the contact hole 25, connecting one end of the second wiring portion 17B to the other end of the conductor 21. The second contact 23 is formed integrally with the second wiring portion 17B. It is preferable that the cross-sectional area of ​​at least one of the first contact 22 and the second contact 23 is smaller than the cross-sectional area of ​​the upper wiring portion (upper contact) in the contact hole 31. In this embodiment, the cross-sectional areas of the first contact 22 and the second contact 23 are smaller than the cross-sectional area of ​​the upper wiring portion in the contact hole 31.

[0151] In the third embodiment, the same effects as in the first embodiment can be obtained.

[0152] In addition, as in the above-mentioned conductor 21, if the width of the conductor 21 in the short direction is shorter than the width of the upper wiring 17 and the conductor 21 has a property of being more susceptible to melting than the upper wiring 17, the cross-sectional area of ​​the first contact 22 and the second contact 23 may be greater than the cross-sectional area of ​​the upper wiring portion within the contact hole 31.

[0153] Furthermore, if the cross-sectional area of ​​at least one of the first contact 22 and the second contact 23 is smaller than the cross-sectional area of ​​the upper wiring portion within the contact hole 31, and if at least one of the first contact 22 and the second contact 23 has a property that makes it more susceptible to melting than the upper wiring 17, the width in the short direction of the conductor 21 may be greater than the width of the upper wiring 17.

[0154] A method for manufacturing the inkjet printhead 1B will now be described in detail.

[0155] 23A to 23J and 24A to 24J are cross-sectional views showing the manufacturing process of the inkjet printhead 1. Figures 23A to 23J are cross-sectional views corresponding to the cross section of Figure 22A, and Figures 24A to 24J are cross-sectional views corresponding to the cross section of Figure 22B.

[0156] 11A and 12A described above, the upper electrode film 73, the piezoelectric material film 72, and the lower electrode film 71 are patterned as shown in FIGS. 23A and 24A. First, a resist mask having the pattern of the upper electrode 13 is formed by photolithography. Then, using this resist mask as a mask, the upper electrode film 73 and the piezoelectric material film 72 are successively etched, thereby forming the upper electrode 13 and the piezoelectric film 12 in a predetermined pattern.

[0157] Next, after the resist mask is peeled off, a resist mask having a pattern of the lower electrode 11 and the conductor 21 is formed by photolithography. Then, using this resist mask as a mask, the lower electrode film 71 is etched, thereby forming the lower electrode 11 and the conductor 21 in a predetermined pattern.

[0158] The lower electrode 11 is made up of a main electrode portion 11A and an extension portion 11B. In this manner, the main electrode portion 11A of the lower electrode 11, the piezoelectric film 12, and the upper electrode 13 form a piezoelectric element 9.

[0159] 23B and 24B, the resist mask is removed, and then a second hydrogen barrier film 14 is formed to cover the entire surface. After that, an insulating film 15 is formed on the entire surface of the second hydrogen barrier film 14. Subsequently, the insulating film 15 and the second hydrogen barrier film 14 are successively etched to form contact holes 31, 32, 24, and 25.

[0160] 23C and 24C, a wiring film is formed by sputtering on insulating film 15, including inside contact holes 31, 32, 24, and 25. Thereafter, the wiring film is patterned by photolithography and etching, thereby simultaneously forming upper wiring 17 (first wiring portion 17A and second wiring portion 17B), first contact 22 and second contact 23 of fuse 20, and lower wiring 18. This results in fuse 20 consisting of conductor 21, first contact 22, and second contact 23.

[0161] Next, as shown in FIGS. 23D and 24D, a passivation film 33 is formed on the surface of the insulating film 15 to cover the upper wiring 17 and the lower wiring 18.

[0162] Next, a resist mask having openings corresponding to the pad openings 34 and 35 is formed by photolithography, and the passivation film 33 is etched using this resist mask. As a result, the pad openings 34 and 35 are formed in the passivation film 33, as shown in Figures 23E and 24E. After the resist mask is peeled off, the upper electrode pad 42 and the lower electrode pad 43 are formed on the passivation film 33 through the pad openings 34 and 35, respectively.

[0163] Next, a resist mask having openings corresponding to the opening 36 and the ink supply through hole 44 is formed by photolithography, and the passivation film 33 and the insulating film 15 are successively etched using this resist mask. As a result, the opening 36 and the ink supply through hole 44 are formed in the passivation film 33 and the insulating film 15, as shown in Figures 23F and 24F.

[0164] Next, the resist mask is peeled off. Then, a resist mask having openings corresponding to the ink supply through holes 44 is formed by photolithography, and the second hydrogen barrier film 14, the first hydrogen barrier film 8, and the movable film formation layer 10 are etched using this resist mask. As a result, as shown in Figures 23G and 24G, the ink supply through holes 44 are formed in the second hydrogen barrier film 14, the first hydrogen barrier film 8, and the movable film formation layer 10. In this way, the substrate assembly aggregate 110 is produced.

[0165] Next, as shown in Figures 23H and 24H, adhesive 50 is applied to the opposing surface 51 of the protective substrate aggregate 130, and the protective substrate aggregate 130 is fixed to the substrate assembly aggregate 110 so that the ink supply path 54 and the corresponding ink supply through hole 44 are aligned.

[0166] Next, as shown in Figures 23I and 24I, backside grinding is performed to thin the actuator wafer 100. The actuator wafer 100 is polished from the backside 100b, thereby thinning the actuator wafer 100. After this, a resist mask having openings corresponding to the ink flow paths 5 (ink inlet portions 6 and pressure chambers 7) and the cavities 19 is formed on the backside 100b side of the actuator wafer 100 by photolithography, and the actuator wafer 100 is etched from the backside 100b using this resist mask as a mask. As a result, the ink flow paths 5 (ink inlet portions 6 and pressure chambers 7) and the cavities 19 are formed in the actuator wafer 100.

[0167] Thereafter, as shown in Figures 23J and 24J, the nozzle substrate aggregate 150 is attached to the back surface 100b of the actuator wafer 100. This results in an inkjet printhead aggregate 170 consisting of the substrate assembly aggregate 110, the protective substrate aggregate 130, and the nozzle substrate aggregate 150. Thereafter, the inkjet printhead aggregate 170 is cut along the planned cutting lines 103 with a dicing blade. In other words, a process is carried out to cut out the inkjet printheads 1 individually.

[0168] When this process is complete, the actuator wafers 100 in the substrate assembly aggregate 110 become the actuator substrates 2 of the individual inkjet printheads 1. Furthermore, the protective substrate aggregate 130 becomes the protective substrates 4 of the individual inkjet printheads 1. Furthermore, the nozzle wafers 140 in the nozzle substrate aggregate 150 each become the silicon substrates of the nozzle substrates 3 of the individual inkjet printheads 1. In this way, individual inkjet printheads 1 having the structure shown in Figures 19 to 22B are obtained.

[0169] Although the embodiments of the present disclosure have been described above, the present disclosure can also be embodied in other embodiments. In the above-described embodiments, two rows of piezoelectric elements (pressure chamber rows) are provided on the actuator substrate 2, but only one row of piezoelectric elements (pressure chamber rows) may be provided, or three or more rows of piezoelectric elements (pressure chamber rows) may be provided.

[0170] In addition, in the above-described embodiment, PZT was exemplified as the material for the piezoelectric film, but other piezoelectric materials made of metal oxides such as lead titanate (PbPO3), potassium niobate (KNbO3), lithium niobate (LiNbO3), and lithium tantalate (LiTaO3) may also be used.

[0171] Furthermore, the upper wiring pattern is not limited to the above-described pattern, and may be, for example, a pattern in which the upper wiring passes between adjacent piezoelectric elements in the front-rear direction.

[0172] Alternatively, a lower wiring may be provided for each piezoelectric element. In this case, instead of providing the fuse 20 in the middle of each upper wiring 17, a fuse may be provided in the middle of each lower wiring.

[0173] Although the embodiments of the present disclosure have been described in detail, these are merely examples used to clarify the technical content of the present disclosure, and the present disclosure should not be construed as being limited to these examples, and the scope of the present disclosure is limited only by the appended claims.

[0174] This application corresponds to Patent Application No. 2020-193728 filed with the Japan Patent Office on November 20, 2020, the entire disclosure of which is incorporated herein by reference. [Explanation of symbols]

[0175] 1,1A,1B Injection Printhead 2 Actuator board 2a surface 2b Back side 3 Nozzle Board 3a Nozzle hole 3b Ink nozzle 4 Protection Board 5 Ink flow path 6 Ink inlet 7 Pressure chamber (cavity) 8 First hydrogen barrier film 9 Piezoelectric element 10 Movable membrane forming layer 10A movable membrane 11 Lower electrode 11A main electrode section 11B Extension 12 Piezoelectric film 13 Upper electrode 14 Second hydrogen barrier film 15 insulating film 17 Upper wiring 18 Lower wiring 19 Cavity 20. Fuse 21 Conductor 22 First Contact 23 Second Contact 24 contact holes 25 contact holes 26 Aperture 31 Contact hole (upper wiring) 32 Contact hole (bottom wiring) 33 Passivation film 34 Pad opening (upper wiring) 35 Pad opening (bottom wiring) 36 Openings (insulating film and passivation film) 41 Ink flow direction 42 Upper electrode pad 43 Lower electrode pad 44 Ink supply through hole 50 Adhesive 51 Opposite surface 52 First recess 53 Second recess 54 Ink supply path 55 Opening 61 First rectangular area 62 Second rectangular area 71 Lower electrode film 72 Piezoelectric material film 73 Upper electrode film 100 Actuator Wafer 100a surface 100b back side 101 Functional element formation area 102 Scribe area 103 Cutting line 110 Substrate assembly assembly 130 Protective substrate assembly 140 nozzle wafer 150 nozzle substrate assembly 170 Inkjet printhead assembly 209 Dummy piezoelectric element 211 Lower electrode 212 Piezoelectric film 213 Upper electrode SA Board Assembly

Claims

1. an actuator substrate having an ink flow path including a pressure chamber; a movable film forming layer disposed above the pressure chamber and including a movable film that defines a top surface of the pressure chamber; a piezoelectric element including a lower electrode disposed on the movable film, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film; a hydrogen barrier film covering at least the entire side surfaces of the upper electrode and the piezoelectric film on the surface of the piezoelectric element; an interlayer insulating film formed on the movable film formation layer so as to cover the hydrogen barrier film; wiring formed on the interlayer insulating film and connected to the piezoelectric element; The inkjet printhead has a fuse inserted in the middle of the wiring.

2. The inkjet printhead of claim 1 , wherein the actuator substrate has a cavity below the fuse.

3. 3. The inkjet printhead according to claim 1, wherein the fuse is made of a conductor made of the same material as the wiring and having a smaller width than the wiring.

4. the wiring has a first wiring portion and a second wiring portion electrically connected via the fuse, the first wiring portion has a first end connected to the piezoelectric element and a second end connected to the fuse, the second wiring portion has a first end connected to the fuse and a second end opposite the first end, 3. The inkjet printhead of claim 1, wherein the fuse comprises a conductor, a first contact connecting a second end of the first wiring portion to a first end of the conductor, and a second contact connecting a first end of the second wiring portion to a second end of the conductor opposite the first end.

5. the wiring is an upper wiring, one end of which is connected to an upper electrode of the piezoelectric element, a dummy piezoelectric element having the same structure as the piezoelectric element but not operating as a piezoelectric element is formed on the movable film formation layer; 5. The ink jet printhead of claim 4, wherein the conductor is a top electrode of the dummy piezoelectric element.

6. 6. The inkjet printhead according to claim 5, wherein the hydrogen barrier film and the interlayer insulating film cover the surfaces of the dummy piezoelectric elements.

7. the hydrogen barrier film and the interlayer insulating film are formed on at least a part of the top surface of the upper electrode of the piezoelectric element, an upper contact hole exposing a part of an upper surface of the upper electrode of the piezoelectric element is formed in the hydrogen barrier film and the interlayer insulating film formed on the upper surface of the upper electrode of the piezoelectric element, and a first end of the first wiring portion enters the upper contact hole and is connected to the upper electrode within the upper contact hole; a first contact hole exposing a part of a first end of the conductor and a second contact hole exposing a part of a second end of the conductor are formed in the hydrogen barrier film and the interlayer insulating film formed on the upper surface of the conductor consisting of the upper electrode of the dummy piezoelectric element; the first contact connects a second end of the first wiring portion and a first end of the conductor through the first contact hole; 7. The inkjet printhead of claim 6, wherein the second contact connects a first end of the second wiring portion and a second end of the conductor through the second contact hole.

8. When a portion of the first wiring portion connected to the upper electrode via the upper contact hole is defined as an upper contact, 8. The inkjet printhead of claim 7, wherein at least one of the first contact and the second contact has a cross-sectional area that is smaller than a cross-sectional area of ​​the top contact.

9. 9. The inkjet printhead according to claim 5, wherein the width of the conductor is smaller than the width of the upper wiring.

10. the wiring is an upper wiring, one end of which is connected to an upper electrode of the piezoelectric element, 5. The ink jet printhead according to claim 4, wherein the conductor is formed from a metal film formed on the movable film formation layer and made of the same material as the lower electrode.

11. The inkjet printhead of claim 10 , wherein the hydrogen barrier film and the interlayer insulating film cover a surface of the conductor.

12. the hydrogen barrier film and the interlayer insulating film are formed on at least a part of the top surface of the upper electrode of the piezoelectric element, an upper contact hole exposing a part of an upper surface of the upper electrode of the piezoelectric element is formed in the hydrogen barrier film and the interlayer insulating film formed on the upper surface of the upper electrode of the piezoelectric element, and a first end of the first wiring portion enters the upper contact hole and is connected to the upper electrode within the upper contact hole; a first contact hole exposing a portion of a first end of the conductor and a second contact hole exposing a portion of a second end of the conductor are formed in the hydrogen barrier film and the interlayer insulating film formed on the upper surface of the conductor; the first contact connects a second end of the first wiring portion and a first end of the conductor through the first contact hole; 12. The inkjet printhead of claim 11, wherein the second contact connects a first end of the second wiring portion and a second end of the conductor through the second contact hole.

13. When a portion of the first wiring portion connected to the upper electrode via the upper contact hole is defined as an upper contact, 13. The inkjet printhead of claim 12, wherein at least one of the first contact and the second contact has a cross-sectional area that is smaller than a cross-sectional area of ​​the top contact.

14. The inkjet printhead according to any one of claims 10 to 13, wherein the width of the conductor is smaller than the width of the upper wiring.

15. 15. The inkjet printhead according to claim 1, further comprising a passivation film formed on the interlayer insulating film and covering the wiring.

16. A plurality of the pressure chambers are provided, the piezoelectric element is provided for each of the pressure chambers, The inkjet printhead according to any one of claims 1 to 15, wherein the actuator substrate has a plurality of pressure chamber rows formed thereon in a plan view at intervals in a predetermined first direction, the pressure chambers being spaced apart in a second direction perpendicular to the first direction.

Images