JP6792225B2 - Inkjet device and manufacturing method of inkjet device - Google Patents

Description

The present invention relates to an inkjet device and a method for manufacturing the same.

Patent Document 1 discloses an inkjet recording head. Specifically, the inkjet recording head of Patent Document 1 includes a pressure generating chamber communicating with the nozzle opening, and a piezoelectric element including a piezoelectric layer and electrodes provided on the piezoelectric layer. The ink stored in the pressure generating chamber is ejected through the nozzle opening.

Japanese Unexamined Patent Publication No. 2013-91272

In the inkjet recording head of Patent Document 1, the piezoelectric layer made of PZT is formed in a size limited to the inner region of the pressure generating chamber. Such a piezoelectric layer can be obtained by laminating PZT films by, for example, the MOD (Metal Organic Decomposition) method or the sol-gel method, and patterning the PZT films.
However, it is not easy to etch PZT with high accuracy so as to fit within a certain region. Therefore, it is difficult to produce the structure of Patent Document 1 with a high yield. Further, since the side surface of the PZT is damaged by etching, in the above configuration in which the peripheral edge of the PZT film is arranged inside the pressure generating chamber, the withstand voltage between the upper electrode and the lower electrode is reduced in the movable portion. To do.

One embodiment of the present invention provides an inkjet device capable of achieving a good withstand voltage in a moving portion of a piezoelectric element.
Further, one embodiment of the present invention provides a method for manufacturing an inkjet device capable of manufacturing an inkjet device capable of achieving a good withstand voltage in a movable portion of a piezoelectric element with a high yield.

One embodiment of the present invention includes an actuator substrate that partitions a cavity in which ink is stored, a diaphragm that is supported by the actuator substrate and partitions the cavity, and an upper electrode and a lower electrode that are provided on the diaphragm. And a piezoelectric element including the upper electrode and the piezoelectric film sandwiched between the lower electrodes, the piezoelectric film extends over a region covering the entire cavity, and the upper electrode is the said. Provided is an inkjet device that is confined to the inner region of the cavity.

When a driving voltage is applied to the piezoelectric element, the vibrating membrane is displaced together with the piezoelectric element, causing a change in the volume of the cavity. As a result, the ink in the cavity is ejected. In the piezoelectric element, since the forming region of the piezoelectric film is not limited to the inner region of the cavity, the piezoelectric film can be easily processed (etched) at the time of patterning the piezoelectric film. Thereby, the yield of the inkjet device can be improved. Further, the peripheral edge of the piezoelectric film is set to at least the outer region of the cavity (that is, the outer region of the movable portion of the piezoelectric element). Therefore, even if the peripheral edge of the piezoelectric film is damaged by etching, it is possible to prevent a decrease in the withstand voltage of the piezoelectric element due to the damage.

In one embodiment of the invention, the lower electrode comprises a contact portion integrally drawn out into the outer region of the cavity, and the piezoelectric membrane surrounds the contact portion.
In one embodiment of the present invention, an ink supply path communicating with the cavity is further formed, and the piezoelectric film surrounds the distribution port.

The piezoelectric film may be exposed on the side surface of the ink supply path, but since the region where the ink supply path is formed is not a moving part of the piezoelectric element, the exposure of the piezoelectric film does not adversely affect the piezoelectric performance. ..
In one embodiment of the invention, the piezoelectric membrane is made of a PZT membrane.
In one embodiment of the present invention, the thickness of the piezoelectric film is 1 μm to 5 μm.

Since the piezoelectric film can be easily processed (etched) as described above, sufficient withstand voltage can be ensured even for a piezoelectric film having a thickness of 1 μm to 5 μm.
In one embodiment of the present invention, the vibrating membrane is made of a SiO ₂ single membrane.
In one embodiment of the present invention, the vibrating membrane is made of a SiN / SiO ₂ laminated membrane.
In one embodiment of the present invention, the upper electrode is made of a Pt single film.

In one embodiment of the present invention, the lower electrode is made of a Pt / Ti laminated film.
One embodiment of the present invention includes a nozzle substrate that supports the actuator substrate, partitions the cavity, and has a nozzle opening communicating with the cavity.
In one embodiment of the present invention, a step of forming a vibrating film on an actuator substrate, a step of sequentially forming a lower electrode film, a piezoelectric film, and an upper electrode film on the vibrating film, and a step of forming the upper electrode film. A step of forming an upper electrode having a predetermined shape by selective etching, a step of selectively etching the piezoelectric film so as to remain in a region surrounding the upper electrode, and a step of covering the entire upper electrode. Further, the present invention provides a method for manufacturing an inkjet apparatus, which includes a step of etching the actuator substrate from below to form a cavity so as to be limited to the inner region of the piezoelectric film after the etching.

In one embodiment of the present invention, the piezoelectric film is selectively etched so as to expose a part of the lower electrode film as a contact portion.
One embodiment of the present invention further comprises the step of forming an ink supply path that penetrates the piezoelectric film and reaches the cavity.
According to this method, the piezoelectric film can be processed into a pattern surrounding the ink supply path.

FIG. 1 is a schematic plan view for explaining a configuration of an inkjet head according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the inkjet head (cross-sectional view taken along line II-II of FIG. 1). FIG. 3 is a cross-sectional view of the inkjet head (cross-sectional view taken along line III-III of FIG. 1). FIG. 4 is a schematic plan view showing a pattern example of the lower electrode of the inkjet head. FIG. 5 is a schematic plan view showing a pattern example of the piezoelectric film of the inkjet head. FIG. 6 is a schematic cross-sectional view showing an ink supply path formed on the protective substrate of the inkjet head. FIG. 7A is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7B is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7C is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7D is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7E is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7F is a diagram for explaining the manufacturing process of the inkjet head. FIG. 7G is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7H is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7I is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7J is a diagram for explaining the manufacturing process of the inkjet head. FIG. 7K is a diagram for explaining the manufacturing process of the inkjet head. FIG. 7L is a diagram for explaining the manufacturing process of the inkjet head. FIG. 7M is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7N is a diagram for explaining the manufacturing process of the inkjet head. FIG. 7O is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7P is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7Q is a diagram for explaining the manufacturing process of the inkjet head. FIG. 7R is a diagram for explaining a manufacturing process of the inkjet head. FIG. 7S is a diagram for explaining the manufacturing process of the inkjet head. FIG. 8A shows a modified example of the pattern of the piezoelectric film. FIG. 8B shows a modified example of the pattern of the piezoelectric film. FIG. 9A shows a modified example of the pattern of the insulating film arranged on the piezoelectric film. FIG. 9B shows a modified example of the pattern of the insulating film arranged on the piezoelectric film. FIG. 9C shows a modified example of the pattern of the insulating film arranged on the piezoelectric film. FIG. 10A shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10B shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10C shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10D shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10E shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10F shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10G shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10H shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10I shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10J shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 10K shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 11A shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 11B shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 11C shows a modified example of the shape of the ink supply path of the protective substrate. FIG. 12A shows a modified example of the wiring pattern for driving the piezoelectric film. FIG. 12B shows a modified example of the wiring pattern for driving the piezoelectric film. FIG. 12C shows a modified example of the wiring pattern for driving the piezoelectric film. FIG. 12D shows a modified example of the wiring pattern for driving the piezoelectric film. FIG. 12E shows a modified example of the wiring pattern for driving the piezoelectric film. FIG. 12F shows a modified example of the wiring pattern for driving the piezoelectric film. FIG. 12G shows a modified example of the wiring pattern for driving the piezoelectric film. FIG. 12H shows a modified example of the wiring pattern for driving the piezoelectric film.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic plan view for explaining the configuration of the inkjet head 1 according to the embodiment of the present invention. FIG. 2 is a cross-sectional view of the inkjet head 1 (cross-sectional view taken along line II-II of FIG. 1). FIG. 3 is a cross-sectional view of the inkjet head 1 (cross-sectional view taken along line III-III of FIG. 1). FIG. 4 is a schematic plan view showing a pattern example of the lower electrode 18 of the inkjet head 1. FIG. 5 is a schematic plan view showing a pattern example of the piezoelectric film 19 of the inkjet head 1. FIG. 6 is a schematic cross-sectional view showing a main part of the protective substrate 4 of the inkjet head 1. In addition, in FIG. 4 and FIG. 5, for convenience of explanation, only necessary reference numerals are shown among the reference numerals shown in FIGS. 1 to 3.

The inkjet head 1 includes an actuator substrate 2, a nozzle substrate 3, and a protective substrate 4.
The actuator substrate 2 is made of, for example, a silicon substrate, and partitions a plurality of cavities 5. The actuator substrate 2 supports the vibrating membrane 6 on the surface 2a. The vibrating membrane 6 forms the top wall of the cavity 5 and partitions the cavity 5. The piezoelectric element 7 is arranged on the vibrating film 6.

The nozzle substrate 3 is joined to the back surface 2b of the actuator substrate 2. The nozzle substrate 3 is made of, for example, a silicon substrate and is attached to the back surface 2b of the actuator substrate 2 to partition the cavity 5 together with the actuator substrate 2 and the vibrating membrane 6. The nozzle substrate 3 has a recess 8 facing the cavity 5, and an ink ejection passage 9 is formed on the bottom surface of the recess 8. The ink ejection passage 9 penetrates the nozzle substrate 3 and has an ejection port on the side opposite to the cavity 5. Therefore, when the volume of the cavity 5 changes, the ink stored in the cavity 5 passes through the ink ejection passage 9 and is ejected from the ejection port.

The protective substrate 4 is made of, for example, a silicon substrate. The protective substrate 4 is arranged so as to cover the piezoelectric element 7, and is bonded to the surface 2a of the actuator substrate 2 via an adhesive 10. The protective substrate 4 has a housing recess 12 on the facing surface 11 facing the surface 2a of the actuator substrate 2. A plurality of piezoelectric elements 7 corresponding to the plurality of cavities 5 are housed in the storage recess 12.

An ink tank (not shown) for storing ink is arranged on the protective substrate 4. The ink supply path 13 is formed so as to penetrate the protective substrate 4. The ink supply path 13 of the protective substrate 4 communicates with the ink supply path 14 in the actuator substrate 2. The ink supply path 14 communicates with the cavity 5. Therefore, the ink in the ink tank, which is the ink supply source, is supplied to the cavity 5 through the ink supply paths 13 and 14.

The configuration of the inkjet head 1 will be described more specifically.
A vibrating film forming layer 15 is formed on the surface 2a of the actuator substrate 2. In the vibrating film forming layer 15, the portion forming the top wall of the cavity 5, that is, the portion partitioning the cavity 5 is the vibrating film 6.
In this embodiment, the cavity 5 is formed so as to penetrate the actuator substrate 2. A plurality of cavities 5 extend in parallel with each other and are formed in a stripe shape on the actuator substrate 2. In FIG. 1, three cavities 5 are shown for clarification. The plurality of cavities 5 are formed at equal intervals with a minute interval (for example, about 30 μm to 350 μm) in the width direction thereof. In plan view, each cavity 5 has a rectangular shape extending elongated along the ink flow direction 16 from the ink supply path 14 toward the ink ejection passage 9. The ink supply path 14 through which the ink from the ink tank 8 is guided communicates with the common ink passage 17 at one end of the cavity 5. As shown in FIG. 1, a plurality of ink supply paths 14 are arranged at intervals along a common ink passage 17. The ink supply path 14 penetrates the vibrating film 6 (all the films arranged on the vibrating film 6 such as the lower electrode 18 and the piezoelectric film 19 described later), and further penetrates the actuator substrate 2 to the common ink passage 17. Is formed.

Each cavity 5 is partitioned by a vibrating membrane 6, an actuator substrate 2, and a nozzle substrate 3, and is formed in a substantially rectangular parallelepiped shape in this embodiment. The length of the cavity 5 may be, for example, about 800 μm, and the width W1 thereof may be about 55 μm. In this embodiment, the ink ejection passage 9 of the nozzle substrate 3 is arranged near the other end portion (the opposite end portion of the ink supply path 14) in the longitudinal direction of the cavity 5.

The vibrating film 6 may be a single film of a silicon oxide film (SiO ₂ ), or may be a laminated film (SiN / SiO ₂ ) in which a silicon nitride film is laminated on a silicon oxide film. The cavity 5 does not have to penetrate the actuator substrate 2, and may be a recess dug from the lower surface side so as to leave a part on the piezoelectric element 7 side. In this case, the rest of the actuator substrate 2 constitutes a part of the vibrating membrane 6. In this specification, the vibrating film 6 means a top wall portion of the vibrating film forming layer 15 that partitions the cavity 5.

The thickness of the vibrating membrane 6 is, for example, 0.4 μm to 2 μm. When the vibrating film 6 is composed of a silicon oxide film, the thickness of the silicon oxide film may be about 1.2 μm. When the vibrating film 6 is composed of a laminate of a silicon layer, a silicon oxide layer, and a silicon nitride layer, the thicknesses of the silicon layer, the silicon oxide layer, and the silicon nitride layer are each about 0.4 μm. May be good.

The piezoelectric element 7 is arranged on the vibrating film 6. A piezoelectric actuator (an example of a piezoelectric device) is composed of a vibrating film 6 and a piezoelectric element 7. The piezoelectric element 7 includes a lower electrode 18 formed on the vibrating film forming layer 15, a piezoelectric film 19 formed on the lower electrode 18, and an upper electrode 20 formed on the piezoelectric film 19. There is. In other words, the piezoelectric element 7 is configured by sandwiching the piezoelectric film 19 between the upper electrode 20 and the lower electrode 18.

The lower electrode 18 may have, for example, a two-layer structure (Pt / Ti) in which a Ti (titanium) layer and a Pt (platinum) layer are laminated in order from the vibrating film 6 side. In addition to this, the lower electrode 18 can also be formed of a single film such as an Au (gold) film, a Cr (chromium) layer, or a Ni (nickel) layer. The thickness of the lower electrode 18 is, for example, 0.2 times or less the thickness of the piezoelectric film 19, and specifically, it may be about 0.2 μm. As shown in FIGS. 2 and 4, the lower electrode 18 is formed over substantially the entire surface 2a of the actuator substrate 2. As a result, the plurality of cavities 5 are covered with a common lower electrode 18. The lower electrode 18 has a main electrode portion 18A arranged on the cavity 5 and an extension portion 18B extending to the outer region of the cavity 5. The main electrode portion 18A is in contact with the upper surface of the vibrating film 6. The ink supply path 14 is formed so as to penetrate the lower electrode 18. The lower electrode 18 surrounds the ink supply path 14 communicating with the cavity 5, and forms a part of the inner surface of the ink supply path 14. That is, the lower electrode 18 is exposed on the inner surface of the ink supply path 14.

As the piezoelectric film 19, for example, a PZT (PbZr _x Ti _1-x O ₃ : lead zirconate titanate) film formed by a sol-gel method or a sputtering method can be applied. Such a piezoelectric film 19 is made of a sintered body of a metal oxide crystal. The thickness of the piezoelectric film 19 is preferably 1 μm to 5 μm. The total thickness of the vibrating membrane 6 is preferably about the same as the thickness of the piezoelectric film 19 or about 2/3 of the thickness of the piezoelectric film 19. Similar to the lower electrode 18, the piezoelectric film 19 is formed over substantially the entire surface 2a of the actuator substrate 2 as shown in FIGS. 2 and 5. As a result, the plurality of cavities 5 are covered with the common piezoelectric film 19. The piezoelectric film 19 has a main portion 19A arranged on the cavity 5 and an extension portion 19B extending to the outer region of the cavity 5. The main portion 19A is in contact with the upper surface of the main electrode portion 18A of the lower electrode 18. The ink supply path 14 is formed so as to penetrate the piezoelectric film 19. The piezoelectric film 19 surrounds the ink supply path 14 communicating with the cavity 5, and forms a part of the inner surface of the ink supply path 14. That is, the piezoelectric film 19 is exposed on the inner surface of the ink supply path 14.

As shown in FIG. 1, one upper electrode 20 is provided on each cavity 5, and each is formed in a strip shape (rectangular shape) along each cavity 5 in a plan view. Further, the upper electrode 20 is arranged so that the entire upper electrode 20 is limited to the inner region of each cavity 5. The upper electrode 20 may be a single film of platinum (Pt), and for example, a conductive oxide film (for example, IrO ₂ (iridium oxide) film) and a metal film (for example, Ir (iridium) film) are laminated. It may have a laminated structure. The thickness of the upper electrode 20 is, for example, 0.2 times or less the thickness of the piezoelectric film 19, and specifically, it may be about 0.2 μm.

As another configuration of the inkjet head 1, a first hydrogen barrier film 21 and a second hydrogen barrier film 22 are provided. The lower surface of the lower electrode 18 (main electrode portion 18A and extension portion 18B) is covered with the first hydrogen barrier film 21, and the surface of the upper electrode 20 and the surface of the extension portion 19B of the piezoelectric film 19 are the second hydrogen. It is covered with a barrier film 22. The first and second hydrogen barrier films 21 and 22 are made of, for example, Al ₂ O ₃ (alumina). This makes it possible to prevent the characteristic deterioration of the piezoelectric film 19 due to hydrogen reduction. The thickness of the first and second hydrogen barrier films 21 and 22 is, for example, about 80 nm.

An interlayer film 23 is laminated on the second hydrogen barrier film 22. The interlayer film 23 is made of, for example, SiO ₂ . The thickness of the interlayer film 23 is, for example, about 500 nm.
The wiring film 24 is formed on the interlayer film 23. The wiring film 24 may be made of a metal material containing Al (aluminum). The thickness of the wiring film 24 is, for example, about 1000 nm. The wiring film 24 includes an upper wiring 25, a lower wiring 26, and a dummy wiring 27.

One end of the upper wiring 25 is arranged above one end of the upper electrode 20. A through hole (contact hole) 28 that continuously penetrates the second hydrogen barrier film 22 and the interlayer film 23 is formed between the upper wiring 25 and the upper electrode 20. One end of the upper wiring 25 enters the through hole 28 and is connected to the upper electrode 20 in the through hole 28. That is, the upper wiring 25 extends from above the upper electrode 20 across the outer edge of the cavity 5 to the outer region of the cavity 5.

The lower wiring 26 is arranged in the outer region of the cavity 5 in a plan view so as not to face the cavity 5. That is, the lower wiring 26 faces the extension portion 18B of the lower electrode 18 in the outer region of the cavity 5. A through hole (contact hole) 29 that continuously penetrates the piezoelectric film 19, the second hydrogen barrier film 22, and the interlayer film 23 is formed between the lower wiring 26 and the extension portion 18B of the lower electrode 18. In this embodiment, one through hole 29 is formed on an extension line of each cavity 5. The lower wiring 26 enters the plurality of through holes 29 and is connected to the extension portion 18B of the lower electrode 18 in the through holes 29. The through hole 29 penetrates the piezoelectric film 19, in other words, the contact portion of the lower wiring 26 with respect to the lower electrode 18 is surrounded by the piezoelectric film 19 as shown in FIG. The piezoelectric film 19 forms a part of the inner surface of the through hole 29, and is in contact with the lower wiring 26 in the through hole 29.

The dummy wiring 27 is a wiring film that is not electrically connected to either the upper wiring 25 or the lower wiring 26 and is electrically insulated. In this embodiment, the dummy wiring 27 is formed in an annular shape surrounding the ink supply path 14, as shown in FIG. More specifically, the dummy wiring 27 has an inner peripheral edge at a position separated from the ink supply path 14 by a certain distance so as not to be exposed on the inner surface of the ink supply path 14.

A passivation film 30 is provided so as to cover the wiring film 24. The passivation film 30 is made of, for example, SiN (silicon nitride). The thickness of the passivation film 30 is, for example, 0.5 times or more the thickness of the piezoelectric film 19, and specifically, it may be about 850 nm. The passivation film 30 is formed with pad openings 31 and 32 that expose a part of the upper wiring 25 and the lower wiring 26 as pads. The pad opening 31 is formed in the outer region of the cavity 5 in a plan view, and is formed, for example, at the tip end portion of the upper wiring 25 (the end opposite to the contact portion with the upper electrode 20). The pad opening 32 is formed so as to cover, for example, a plurality of contact portions (through holes 29) of the lower wiring 26.

An opening 33 is formed in the second hydrogen barrier film 22, the interlayer film 23, and the passivation film 30. A part of the surface of the upper electrode 20 is exposed from the opening 33. In this embodiment, as shown in FIG. 1, the peripheral edge of the upper electrode 20 is covered with the second hydrogen barrier film 22 so that the central portion of the upper electrode 20 is selectively exposed from the opening 33. The outer edge of the opening 33 of the film (in this embodiment, the interlayer film 23 and the passivation film 30) that is not in contact with the upper electrode 20 may be set in the outer region of the upper electrode 20 as shown in FIG. ..

The protective substrate 4 is formed with through holes 34, 35 that expose the pad region on the actuator substrate 2 including the pad opening 31 and the pad opening 32.
The piezoelectric element 7 is formed at a position facing the cavity 5 with the vibrating film 6 interposed therebetween. That is, the piezoelectric element 7 is formed so as to be in contact with the surface of the vibrating membrane 6 opposite to the cavity 5. A vibrating film forming layer 15 is formed on the actuator substrate 2, and the vibrating film 6 is supported by a portion around the cavity 5 in the vibrating film forming layer 15. In this way, the vibrating film 6 is supported by the actuator substrate 2. The vibrating membrane 6 has flexibility that can be deformed in the direction facing the cavity 5 (in other words, the thickness direction of the vibrating membrane 6).

When a drive voltage is applied to the piezoelectric element 7 from the drive IC (not shown), the piezoelectric film 19 is deformed by the inverse piezoelectric effect. As a result, the vibrating film 6 is deformed together with the piezoelectric element 7, which causes a volume change in the cavity 5 and pressurizes the ink in the cavity 5. The pressurized ink passes through the ink ejection passage 9 and is ejected as fine droplets from the ejection port.

The following description will be further added to the configuration of the inkjet head 1.
(1) Internal stresses of the vibrating membrane 6 and the piezoelectric film 19 In this embodiment, the vibrating membrane 6 has a compressive stress and the piezoelectric film 19 has a tensile stress. For example, the compressive stress of the vibrating membrane 6 is −300 MPa to −100 MPa, and the tensile stress of the piezoelectric film 19 is 100 MPa to 300 MPa. As a result, the absolute value of the average stress of the vibrating film 6 and the piezoelectric film 19 is 100 MPa or less. The average stress can be calculated by obtaining the average value of these values, with the tensile stress of the piezoelectric film 19 as a positive value and the compressive stress of the vibrating film 6 as a negative value.

Further, a plurality of upper layer membranes (for example, the first hydrogen barrier membrane 21, the piezoelectric membrane 19, the second hydrogen barrier membrane 22,) including the piezoelectric membrane 19 arranged above the vibrating membrane 6 when viewed from the actuator substrate 2. In consideration of the interlayer film 23 and the passivation film 30), the absolute value of the average stress between the upper layer film and the vibrating film 6 may be, for example, 50 MPa or less.
(2) The dug portion 37 of the ink supply path 13
As shown in FIGS. 2 and 6, the protective substrate 4 is formed with a through hole 36 forming an ink supply path 13, and further, the facing surface 11 of the protective substrate 4 communicates with the through hole 36. A digging portion 37 is formed. The digging portion 37 surrounds the through hole 36 and forms a wide portion at the end of the through hole 36. In this embodiment, the through hole 36 is formed in a circular shape in a plan view, and the dug portion 37 is also formed in a circular shape concentric with the through hole 36 and having a diameter larger than that of the through hole 36. .. Therefore, due to the digging portion 37, the through hole 36 has a large diameter portion 38 and a small diameter portion 39 in this order from the facing surface 11 of the protective substrate 4. The opening diameter of the through hole 36 in the large diameter portion 38 is larger than the opening diameter of the small diameter portion 39.

The small diameter portion 39 and the large diameter portion 38 are connected via a stepped surface 40 arranged in the middle of the protective substrate 4 in the thickness direction. The stepped surface 40 extends in a direction intersecting the ink flow direction (longitudinal direction) of the through hole 36, and is arranged substantially in the center in the thickness direction of the protective substrate 4. As a result, the through hole 36 is formed in a funnel shape that narrows from the facing surface 11 toward the surface opposite to the facing surface 11 in a cross-sectional view, and the stepped surface 40 is a protective substrate as shown in FIG. When viewed from the normal direction of the facing surface 11 of 4, the small diameter portion 38 is formed in an annular shape surrounding the small diameter portion 38.
(3) Difference in Opening Diameters of Through Holes 34 to 36 in Protective Substrate 4 The opening diameters of through holes 34 to 36 formed in the protective substrate 4 are different from each other. For example, based on the diameter D1 of the through hole 36 serving as the ink supply path 13, the diameter D2 of the through hole 34 and the diameter D3 of the through hole 35 are larger than the diameter D1. In FIG. 2, for convenience of explanation, the diameter of the small diameter portion 39 of the through hole 36 is defined as the diameter D1, but even when the diameter D1 is defined as the diameter of the large diameter portion 38, the relationship of diameter D1> diameter D2 and D3 Is maintained.

In this embodiment, the thickness of the protective substrate 4 is 200 μm to 500 μm, and the diameter D1 of the through hole 36 is 30 μm to 50 μm. On the other hand, the diameter D2 of the through hole 34 is 300 μm to 1500 μm, and the diameter D3 of the through hole 35 is 300 μm to 1500 μm. As a result, the aspect ratio of the through holes 36 (opening depth (thickness of the protective substrate 4) / opening diameter) is larger than the aspect ratios of the through holes 34 and 35. For example, the aspect ratio of the through holes 36 is 10 times or more the aspect ratio of the through holes 34 and 35.
(4) The total width of the upper wiring 25 is equal to or greater than the width of the upper electrode 20 As shown in FIGS. 1 and 3, the upper wiring 25 has a total width equal to or greater than the width W2 of the upper electrode 20. The total width is the width of the upper wiring 25 itself when each upper wiring 25 is composed of one wiring film as shown in FIG.

The upper wiring 25 includes a first region 41 that crosses the boundary region 43 (that is, the outer edge of the cavity 5) between the movable portion and the non-movable portion of the inkjet head 1 and a second region 42 that is laid in the outer region of the cavity 5. And are included integrally. In this embodiment, both the first region 41 and the second region 42 have widths W3 and W4 equal to or larger than the width W2 of the upper electrode 20. On the other hand, the width W3 of the first region 41 is larger than the width W1 of the cavity 5, but the width W4 of the second region 42 is smaller than the width W1 of the cavity 5. That is, in the configuration of FIG. 1, the upper wiring 25 has a wide portion in a region crossing the boundary region 43 and a narrow portion in the outer region of the cavity 5. The width W3 of the first region 41 of the upper wiring 25 is, for example, 75 μm to 85 μm, and the width W2 of the second region 42 is, for example, 10 μm to 25 μm.

Further, as shown in FIG. 3, since the upper electrode 20 is arranged so as to be restricted to the inner region of the cavity 5, steps are formed on both sides of the upper electrode 20 in the width direction depending on the thickness of the upper electrode 20. Is formed. Then, the upper wiring 25 has a leg portion 44 formed so as to be hooked on the step in the outer region of the cavity 5 by covering the step.
7A to 7S are diagrams for explaining the manufacturing process of the inkjet head 1. 7A-7S show the cross section of the inkjet head 1 corresponding to FIG.

The manufacturing process of the inkjet head 1 is roughly divided into a preparation process for the protective substrate 4 shown in FIGS. 7A to 7I, a preparation process for the actuator substrate 2 shown in FIGS. 7J to 7Q, and others shown in FIGS. 7R to 7S. Including the process of. In the following, the preparation step of the actuator board 2 will be described after the preparation step of the protective substrate 4 will be described, but the order of these steps may be reversed from each other.

First, as shown in FIG. 7A, for example, a protective substrate 4 (silicon substrate) having a thickness of 400 μm is prepared, and as shown in FIG. 7B, a thermal oxide film 45 (for example, a thickness of 15000 Å) is formed on the surface of the protective substrate 4. It is formed.
Next, as shown in FIG. 7C, by patterning the thermal oxide film 45, an opening is formed in the region where the through hole 36 should be formed. Then, by dry etching using the thermal oxide film 45 as a mask, the hole portion 46 is formed up to the middle (approximately the center position) in the thickness direction of the protective substrate 4. The hole portion 46 is a portion that finally becomes a small diameter portion 39 of the through hole 36.

Next, as shown in FIG. 7D, an oxide film 47 is formed on the back surface of the protective substrate 4 (the surface that finally becomes the facing surface 11) by, for example, plasma CVD. Next, a resist film 48 having an opening in a region to be formed in the accommodating recess 12 and the through holes 34 to 36 is formed on the oxide film 47. Then, the oxide film 47 is selectively removed by dry etching using the resist film 48 as a mask. After that, the resist film 48 is removed.

Next, as shown in FIG. 7E, a support substrate 49 (for example, a silicon substrate having a thickness of 400 μm) is adhered to the surface of the protective substrate 4. The protective substrate 4 is supported by the support substrate 49. Next, a resist film 50 is formed on the back surface of the protective substrate 4 so as to cover the oxide film 47. In the resist film 50, among the portions embedded in the plurality of openings of the oxide film 47, the portions corresponding to the through holes 34 to 36 are selectively removed.

Next, as shown in FIG. 7F, the protective substrate 4 is selectively removed from the back surface by dry etching using the resist film 50 and the oxide film 47 as masks. The etching start position is a position corresponding to the through holes 34 to 36. By etching from the region on the opposite side of the hole 46, a through hole 36 (drilled portion 37) is formed when the etching reaches the bottom of the hole 46. At this time, etching from the back surface is performed with the diameter of the large diameter portion 38 of the through hole 36. On the other hand, in the region other than the through hole 36, the protective substrate 4 is etched with a diameter larger than that for the through hole 36, so that the through holes 34 and 35 that reach from the back surface to the front surface of the protective substrate 4 at once are holes. It is formed at the same time as the opening of the portion 46. After that, the resist film 50 is removed.

Next, as shown in FIG. 7G, the accommodating recess 12 is formed by selectively removing the protective substrate 4 from the back surface.
Next, as shown in FIG. 7H, the support substrate 49 is removed.
Next, as shown in FIG. 7I, the oxide films 45 and 47 covering the front and back surfaces of the protective substrate 4 are removed. As a result, the preparation of the protective board 4 to which the actuator board 2 is attached is completed.

On the other hand, the preparation process of the actuator substrate 2 is as follows. First, as shown in FIG. 7J, for example, an actuator substrate 2 (silicon substrate) having a thickness of 625 μm is prepared, and a vibrating film forming layer 15 is formed on the surface 2a thereof. The vibrating film forming layer 15 is formed by, for example, plasma CVD.
Next, the first hydrogen barrier film 21 (for example, 80 nm thickness) is formed on the vibrating film forming layer 15. The first hydrogen barrier film 21 is formed by, for example, a sputtering method. After the formation of the first hydrogen barrier film 21, the lower electrode 18, the piezoelectric film 19 and the upper electrode 20 are formed in this order. The lower electrode 18 and the upper electrode 20 are formed by, for example, a sputtering method, and the piezoelectric film 19 is formed by, for example, a sol-gel method, but may be formed by a sputtering method.

In the sol-gel method of the piezoelectric film 19, a gelled film formed by gelling a coating film of a precursor solution containing PZT is laminated on the lower electrode 18 and then heat-treated to perform main firing. A firing step is performed to form the piezoelectric film 19. The sol-gel method is usually carried out under high temperature conditions (for example, about 700 ° C. in the main firing step), and then the film is cooled. Since the membrane shrinks during this cooling, the piezoelectric membrane 19 has tensile stress.

After that, the upper electrode 20 is selectively etched so as to have a predetermined final shape. In this way, the piezoelectric element 7 is formed.
Next, as shown in FIG. 7K, the second hydrogen barrier film 22 and the interlayer film 23 are sequentially formed so as to cover the piezoelectric element 7. Subsequently, the interlayer film 23 and the second hydrogen barrier film 22 are continuously etched to form through holes 28 and 29.

Next, as shown in FIG. 7L, a TiN film (for example, a thickness of 50 nm) is formed on the interlayer film 23, and then the wiring film 24 is formed by a sputtering method. After that, by patterning the wiring film 24, the upper wiring 25, the lower wiring 26, and the dummy wiring 27 are formed at the same time.
Next, as shown in FIG. 7M, a passivation film 30 covering the wiring film 24 is formed. The passivation film 30 is formed by, for example, plasma CVD.

Next, as shown in FIG. 7N, the passivation film 30 is selectively etched to form the pad openings 31 and 32.
Next, as shown in FIGS. 7O and 7P, after the passivation film 30 and the interlayer film 23 on the upper electrode 20 are continuously etched, the second hydrogen barrier film 22 is selectively etched. As a result, the opening 33 is formed.

Next, as shown in FIG. 7Q, a plurality of films on the actuator substrate 2 are continuously etched. As a result, the ink supply path 14 penetrating the piezoelectric film 19 and the lower electrode 18 (extension portion 18B) is formed.
Next, as shown in FIG. 7R, the adhesive 10 is then applied to the facing surface 11 of the protective substrate 4 with the facing surface 11 facing upward, and the ink supply path 13 and the ink supply path 14 are connected to each other. The actuator board 2 is fixed to the protective board 4 from above so as to match. Next, the actuator substrate 2 is thinned (for example, 625 μm → 100 μm) by being ground from the back surface 2a, and then the cavity 5 is formed by selective etching from the back surface 2a.

After that, as shown in FIG. 7S, the nozzle substrate 3 is fixed to the back surface 2b of the actuator substrate 2 so as to cover the cavity 5 of the actuator substrate 2. The inkjet head 1 is obtained through the above steps.
<Effect>
(1) Action and effect regarding the pattern of the piezoelectric film 19 In this embodiment, for example, as shown in FIG. 5, the piezoelectric film 19 is formed on almost the entire surface 2a of the actuator substrate 2, and the piezoelectric film 19 is formed. The forming region is not limited to the inner region of the cavity 5. The region where the piezoelectric film 19 is not formed is only the contact portion (through hole 29) of the ink supply path 14 and the lower wiring 26. Moreover, these removal regions can be formed by etching (FIGS. 7K, 7P) when forming the ink supply path 14 and the through hole 29. Therefore, it is not necessary to pattern the piezoelectric film 19. Even if the pattern of the piezoelectric film 19 is not the entire surface 2a of the actuator substrate 2, if the pattern extends over the region covering the entire cavity 5, the size is large and precise etching accuracy is not required. When patterning the film 19, the piezoelectric film 19 can be easily processed (etched). Thereby, the yield of the inkjet head 1 can be improved. Further, if the peripheral edge of the piezoelectric film 19 is set to at least the outer region of the cavity 5 (that is, the outer region of the movable portion of the piezoelectric element 7), the peripheral edge of the piezoelectric film 19 is damaged by etching. Even if it is damaged, it is possible to prevent a decrease in the withstand voltage of the piezoelectric element 7 due to the damage.

In this embodiment, the piezoelectric film 19 is exposed on the side surface of the ink supply path 14, but since the formed region of the ink supply path 14 is not a movable part of the piezoelectric element 7, the piezoelectric film 19 is exposed. It does not adversely affect the piezoelectric performance.
(2) Actions and Effects on Internal Stress of Vibrating Film 6 and Piezoelectric Membrane 19 In this embodiment, the piezoelectric film 19 has a tensile stress in the opposite direction to that of the vibrating membrane 6, so that it occurs in the vibrating membrane 6. The compressive stress can be offset. As a result, as shown in FIG. 7R, the tension applied to the vibrating film 6 when the actuator substrate 2 is etched and the vibrating film 6 is released can be brought close to zero. Therefore, the vibrating film 6 can be satisfactorily displaced when the piezoelectric element 7 is driven. Therefore, it is possible to obtain a displacement of a size required for ejecting ink. Moreover, the compressive stress of the vibrating film 6 can be easily adjusted by controlling the film forming conditions when performing plasma CVD, and the tensile stress of the piezoelectric film 19 is formed when the solgel method and the sputtering method are carried out. It can be easily adjusted by controlling the membrane conditions.

Further, in this embodiment, since the portion of the passivation film 30 on the upper electrode 20 is removed, the stress of the passivation film 30 has almost no effect on the tension of the vibrating film 6. Further, since the first hydrogen barrier film 21, the second hydrogen barrier film 22, the interlayer film 23, the lower electrode 18 and the upper electrode 20 are considerably thinner than the piezoelectric film 19, they have some internal stress. However, the stress does not affect the tension of the vibrating membrane 6 as in the passivation membrane 30 of this embodiment.
(3) Actions and Effects on the Digging Part 37 In this embodiment, since the digging portion 37 is formed on the facing surface 11 of the protective substrate 4, the adhesive 10 is used when fixing the actuator substrate 2 to the protective substrate 4. Even if the adhesive flows from around the through hole 36, all or part of the adhesive 10 can be captured by the digging portion 37. As a result, it is possible to prevent or prevent the through hole 36 (ink supply path 13) of the protective substrate 4 from being blocked by the adhesive 10. Therefore, the ink can be satisfactorily supplied to the cavity 5.

Further, the dug portion 37 is formed in a circular shape concentric with the through hole 36 and having a diameter larger than that of the through hole 36. Therefore, since the space required for forming the digging portion 37 is sufficient around the through hole 36, it is possible to prevent the device from becoming large due to the formation of the digging portion 37.
(4) Actions and Effects Regarding Method for Forming Through Hole 36 (Ink Supply Path 13) of Protective Substrate 4 In this embodiment, the through hole 36 is first formed after a hole 46 is formed on the surface of the protective substrate 4 (FIG. FIG. 7C), the protective substrate 4 is etched from the back surface to open the hole 46 (FIG. 7F). That is, in order to form the through hole 36, etching is performed from each of the front surface and the back surface of the protective substrate 4, but the etching depth at one time is shallower than in the case of etching from the front surface to the back surface at once. Therefore, the average etching rate up to the formation of the through hole 36 can be increased. As a result, the etching time required for forming the through hole 36 can be shortened.

Further, in this embodiment, it is necessary to form through holes 34 to 36 having different sizes from each other in the protective substrate 4. In this case, since the hole portion 46 is formed in advance in the formation region of the through hole 36 having a relatively small etching size, in the step of FIG. 7F, from the region where the through hole 36 should be formed on the back surface of the protective substrate 4. The through hole 36 can be formed by etching a substrate material having a thickness obtained by subtracting the depth of the hole portion 46 from the thickness of the protective substrate 4. Therefore, although the etching rate differs between the region where the through holes 36 are formed and the regions where the through holes 34 and 35 are formed, the timing at which the through holes 34 to 36 are formed in each region (that is, the etching completion time) Through holes 34 to 36 can be formed at substantially the same timing without variation. As a result, the occurrence of overetching can be suppressed or prevented.
(5) Action and effect regarding the shape of the through hole 36 (ink supply path 13) of the protective substrate 4 Unlike this embodiment, when etching from the opposite side of the hole 46, the etching size is almost the same as that of the hole 46. And, due to misalignment or the like, a step may occur at the seam portion of the through hole 36 (in the middle of the protective substrate 4 in the thickness direction), and a portion where the diameter of the through hole 36 is smaller than the design value may occur. .. Therefore, as shown in FIG. 6, the through hole 36 has a large diameter portion 38 and a small diameter portion 39, and the processing dimension of the large diameter portion 38 is set to a size in consideration of misalignment, so that at least A diameter corresponding to the small diameter portion 39 can be secured. Therefore, by forming the small diameter portion 39 according to the design value of the through hole 36, the through hole 36 having the diameter according to the design value can be obtained.
(6) Action and Effect Regarding Pattern of Upper Wiring 25 In this embodiment, as shown in FIGS. 1 and 3, at least the first region 41 of the upper wiring 25 (the boundary between the movable portion and the non-movable portion of the inkjet head 1). The width W3 of the region (region that crosses the region 43) is equal to or greater than the width W2 of the upper electrode 20. Therefore, even if a large stress is applied to the portion of the upper wiring 25 on the boundary region 43 due to the displacement of the vibrating membrane 6, the disconnection can be prevented.
<Modification example>
(1) Modification Example of Pattern of Piezoelectric Membrane 19 FIGS. 8A and 8B show a modification of the pattern of the piezoelectric membrane 19.

In the configuration of FIG. 8A, the piezoelectric film 19 is formed one by one corresponding to each cavity 5, although the pattern extends over the region covering the entire cavity 5. The extension portion 19B of each piezoelectric film 19 is formed along the periphery of the cavity 5. With this configuration as well, the action and effect shown in the above-mentioned "<Action and effect> (1) Action and effect related to the pattern of the piezoelectric film 19" can be realized. In order to form the piezoelectric film 19 in this section, for example, after forming the piezoelectric film 19 in the step shown in FIG. 7J and before forming the upper electrode 20, the piezoelectric film 19 has a predetermined shape. It may be patterned so as to be.

On the other hand, in the configuration of FIG. 8B, the piezoelectric film 19 has only the main portion 19A and does not have the extension portion 19B. The main portion 19A of the piezoelectric film 19 has a larger planar size than the upper electrode 20, but is limited to the inner region of the cavity 5.
(2) Deformation Examples of the Pattern of the Insulating Film Arranged on the Piezoelectric Membrane 19 FIGS. 9A to 9C show the insulating film arranged on the piezoelectric film 19, specifically, the second hydrogen barrier film 22, A modified example of the patterns of the interlayer film 23 and the passivation film 30 is shown.

In the configuration of FIG. 9A, the opening 33 is not formed in the second hydrogen barrier film 22, and the surface of the upper electrode 20 is covered with the second hydrogen barrier film 22. In the configuration of FIG. 9B, the interlayer film 23 also has no opening 33. Further, in the configuration of FIG. 9C, the opening 33 is not formed in the passivation film 30 either.
In particular, when the passivation film 30 remains on the piezoelectric film 19 as in the configuration of FIG. 9C, since the passivation film 30 is a relatively thick film, the passivation film is used to adjust the tension applied to the vibrating film 6. It is necessary to consider the internal stress of 30. That is, it is preferable that the absolute value of the average stress including the passivation film 30, that is, the absolute value of the average stress of the vibrating film 6, the piezoelectric film 19 and the passivation film 30 is 50 MPa or less. By doing so, the action and effect shown in the above-mentioned "<Action and effect> (2) Action and effect regarding internal stress of the vibrating film 6 and the piezoelectric film 19" can be satisfactorily realized.
(3) Deformation Example Regarding the Shape of the Digging Part 37 of the Protective Substrate FIGS. 10A to 10K show a deformation example regarding the shape of the ink supply path 13 (particularly, the digging portion 37) of the protective substrate 4.

In the configuration of FIG. 10A, the digging portion 37 has an embankment portion 52 provided over the entire circumference of the digging portion 37 so as to form a concave groove portion 51 at the bottom of the digging portion 37 in a cross-sectional view. Have. In particular, in the configuration of FIG. 10A, the embankment portion 52 is formed in a shape having a sharp top in a cross-sectional view. On the other hand, as in the configuration of FIG. 10B, the top of the embankment portion 52 may be formed in a flat shape in cross-sectional view. In the configurations of FIGS. 10A and 10B, since the adhesive that has flowed into the through hole 36 can be captured by the groove 51, it is possible to prevent the adhesive after capture from flowing out into the through hole 36.

In the configuration of FIG. 10C, the dug portion 37 (large diameter portion 38) is formed in a tapered shape. That is, the diameter of the large diameter portion 38 gradually decreases from the facing surface 11 of the protective substrate 4 toward the opposite side.
In the configuration of FIG. 10D, the digging portion 37 has a plurality of step structures 53 (two steps in FIG. 10D) whose width is gradually narrowed step by step so that a plurality of large diameter portions 38 are formed. There is.

In the configuration of FIG. 10E, the dug portion 37 includes a radial portion 54 extending from the side surface of the large diameter portion 38. The radial portion 54 is configured, for example, by providing a plurality of fin-shaped grooves along the side surface of the through hole 36 at equal intervals. With the configuration of FIG. 10E, it is possible to prevent the adhesive from flowing into the dug portion 37 at once.
10F to 10K show a configuration in which the digging portion 37 shown in FIGS. 6 and 10A to 10E is formed on the surface portion of the facing surface 11 of the protective substrate 4, respectively. In FIGS. 6 and 10A to 10E, the dug portion 37 was formed to substantially the center in the thickness direction of the protective substrate 4.
(4) Deformation Example Regarding the Shape of the Ink Supply Path 13 of the Protective Board 4 FIGS. 11A to 11C show a modification of the shape of the ink supply path 13 of the protective substrate 4.

If the focus is on the above-mentioned "(4) Action and effect relating to the method of forming the through hole 36 (ink supply path 13) of the protective substrate 4", when the protective substrate 4 is etched from the back surface to open the hole 46. (FIG. 7F), etching may be performed with the same etching size as the diameter of the hole 46. In this case, the dug portion 37, the large diameter portion 38, and the small diameter portion 39 are not formed, but the through hole 36 has a slight etching position in the middle of the protective substrate 4 in the thickness direction (in this embodiment, the substantially central portion). It may have a seam 55 (configuration of FIG. 11A) or a step 56 (configuration of FIG. 11B) caused by the displacement.

In the configuration of FIG. 11C, the small diameter portion 39 is formed on the facing surface 11 side of the protective substrate 4, and the large diameter portion 38 is formed on the opposite side of the facing surface 11. That is, the positional relationship between the large diameter portion 38 and the small diameter portion 39 is reversed with respect to the configuration of FIG. With this configuration as well, the above-mentioned "<action effect> (5) action effect related to the shape of the through hole 36 (ink supply path 13) of the protective substrate 4" can be realized. In order to form the through hole 36 having the configuration of FIG. 11C, for example, in the step shown in FIG. 7C, a hole portion 46 having the same diameter as the large diameter portion 38 is formed, and when the hole portion 46 is opened, the small diameter portion 46 is formed. The protective substrate 4 may be etched with the same etching size as that of the portion 39.
(5) Deformation Example Regarding Pattern of Upper Wiring 25 FIGS. 12A to 12H show a modification of the pattern of the upper wiring 25.

In the configuration of FIG. 12A, the width W3 of the first region 41 and the width W4 of the second region 42 of the upper wiring 25 are the same. That is, the upper wiring 25 is formed with a constant width. The relationship between the width W2 of the upper electrode 20, the widths W3 and W4, and the width W1 of the cavity 5 is width W2 <width W3 = width W4 <width W1.
In the configuration of FIG. 12B, the contact portion (the portion near the through hole 28) of the first region 41 with the upper electrode 20 is selectively narrower than the width W2 of the upper electrode 20 with respect to the configuration of FIG. 12A. There is. On the other hand, in the portion crossing the boundary region 43, the width W3 of the first region 41 is equal to or larger than the width W2 of the upper electrode 20 as in the configuration of FIG. 12A.

In the configuration of FIG. 12C, in the configuration of FIG. 12A, the relationship between the width W1 and the width W4 is width W2 <width W1 <width W3 = width W4.
In the configuration of FIG. 12D, in the configuration of FIG. 1, the piezoelectric film 19 is formed in a size limited to the inner region of the cavity 5 in a plan view. The relationship between the width W1 to the width W4 and the width W5 of the piezoelectric film 19 is width W2 <width W4 <width W5 <width W1 <width W3. Further, in the configurations of FIGS. 12E and 12F, in the configuration of FIG. 12D, the relationship of width W1 to width W5 is such that width W2 <width W4 <width W5 <width W3 <width W1 (FIG. 12E) and width W2 <, respectively. Width W3 = Width W4 <Width W5 <Width W1 (FIG. 12F).

In the configuration of FIG. 12G, the upper wiring 25 is composed of a plurality of wiring films 24. In this case, the total width of the width W3 ′ of the first region 41 of one upper wiring 25 and the width W3 ″ of the first region 41 of the other upper wiring 25 is equal to or larger than the width W2 of the upper electrode 20. For example, the above-mentioned "<action effect> (6) action effect related to the pattern of the upper wiring 25" can be realized.
In the configuration of FIG. 12H, in the configuration of FIG. 12G, both one and the other upper wiring 25 are formed with a constant width (that is, width W3 ′ (width W3 ″) = width W4 ′ (width W4 ″). ´)).

Although the embodiments of the present invention have been described above, the present invention can also be implemented in other embodiments.
In addition, various design changes can be made within the scope of the matters described in the claims.
In addition to the inventions described in the claims, the following first and second inventions can be extracted from the contents of this specification.
(1) First Invention <Problems to be Solved by the First Invention>
Generally, the piezoelectric material is formed under high temperature conditions and then cooled, so that it has tensile stress due to shrinkage during cooling. Therefore, in Patent Document 1, when the silicon substrate material directly under the elastic film is removed to form a pressure generating chamber, the elastic film may be pulled with a large tension due to the stress of the piezoelectric layer. This causes the displacement of the elastic membrane to be small. On the other hand, when the elastic film is compressed, there is a problem that the elastic film has a large slack and the control of the displacement amount is not stable.

One embodiment of the present invention provides an inkjet device capable of satisfactorily displacing a vibrating membrane and a method for manufacturing the same.
<Means to solve the problem>
In one embodiment of the present invention, an actuator substrate that partitions a cavity in which ink is stored, a piezoelectric film that is supported by the actuator substrate and partitions the cavity, and a diaphragm provided on the diaphragm are displaced. Provided are a piezoelectric element having a piezoelectric film that changes the volume of the cavity, and an inkjet device in which the vibrating film has a compressive stress and the piezoelectric film has a tensile stress.

When a driving voltage is applied to the piezoelectric element, the vibrating membrane is displaced together with the piezoelectric element, causing a change in the volume of the cavity. As a result, the ink in the cavity is ejected. Since the piezoelectric membrane has a tensile stress in the opposite direction to the vibrating membrane, the compressive stress generated in the vibrating membrane can be offset. As a result, the tension applied to the vibrating membrane can be brought close to zero. Therefore, the vibrating membrane can be satisfactorily displaced when the piezoelectric element is driven. Therefore, it is possible to obtain a displacement of a size required for ejecting ink.

In one embodiment of the present invention, the absolute value of the average stress of the vibrating membrane and the piezoelectric film is 100 MPa or less.
One embodiment of the present invention further includes a passivation membrane formed so as to selectively expose the region for the piezoelectric element and having a thickness of 0.5 times or more that of the piezoelectric film.
One embodiment of the present invention further includes a passivation film formed so as to cover the piezoelectric element, and the absolute value of the average stress of the vibrating film, the piezoelectric film and the passivation film is 50 MPa or less.

In one embodiment of the present invention, the absolute value of the average stress between the vibrating membrane and the plurality of upper layer membranes including the piezoelectric film arranged above the vibrating membrane when viewed from the actuator substrate is 100 MPa or less. Is.
In one embodiment of the present invention, the compressive stress of the vibrating membrane is −300 MPa to −100 MPa, and the tensile stress of the piezoelectric membrane is 100 MPa to 300 MPa.

In one embodiment of the present invention, the piezoelectric membrane has substantially the same thickness as the vibrating membrane.
In one embodiment of the present invention, the thickness of the vibrating membrane and the piezoelectric film is 1 μm to 5 μm.
In one embodiment of the present invention, the piezoelectric element includes an upper electrode and a lower electrode having a thickness of 0.2 times or less the piezoelectric film sandwiching the piezoelectric film.

In one embodiment of the present invention, the upper electrode is made of a Pt single film.
In one embodiment of the present invention, the lower electrode is made of a Pt / Ti laminated film.
In one embodiment of the invention, the piezoelectric membrane comprises a PZT membrane.
In one embodiment of the present invention, the vibrating membrane is made of a SiO ₂ single membrane.
In one embodiment of the present invention, the vibrating membrane is made of a SiN / SiO ₂ laminated membrane.

One embodiment of the present invention includes a nozzle substrate that supports the actuator substrate, partitions the cavity, and has a nozzle opening communicating with the cavity.
One embodiment of the present invention includes a step of forming a diaphragm having compressive stress on an actuator substrate, a step of forming a piezoelectric element having a piezoelectric film having tensile stress on the diaphragm, and the vibration. Provided is a method for manufacturing an inkjet apparatus, which comprises a step of etching the actuator substrate from below in a region facing the film to form a cavity.

In one embodiment of the present invention, the vibrating film is formed by plasma CVD that employs predetermined film formation conditions.
By controlling the film forming conditions (gas pressure, etc.) when performing plasma CVD, the compressive stress of the vibrating membrane can be easily adjusted.
In one embodiment of the present invention, the piezoelectric film is formed by a sol-gel method or a sputtering method that employs predetermined film forming conditions.

By controlling the film forming conditions when the sol-gel method and the sputtering method are carried out, the tensile stress of the piezoelectric film can be easily adjusted.
(2) Second Invention <Problems to be Solved by the Second Invention>
In the inkjet recording head of Patent Document 1, a plurality of through holes (for example, reference numerals 33 and 43) are formed in the protective substrate of the piezoelectric element. These through holes are usually formed by etching the protective substrate, but since the etching rate decreases as the etching depth increases, it takes a long time to penetrate the protective substrate.

Further, since the etching rate increases as the etching size increases, there is a problem that overetching (undercut) occurs in the larger through hole when the sizes of the plurality of through holes are different from each other.
Further, it is preferable that the through hole is formed with a size as designed.
One embodiment of the present invention provides a method for manufacturing an inkjet device capable of shortening the etching time required for forming a through hole in a protective substrate, and an inkjet device obtained thereby.

Further, one embodiment of the present invention provides a method for manufacturing an inkjet device capable of suppressing or preventing overetching when forming a through hole in a protective substrate, and an inkjet device obtained thereby.
Further, one embodiment of the present invention provides a method for manufacturing an inkjet device capable of forming through holes in a protective substrate having a size as designed, and an inkjet device obtained thereby.
<Means to solve the problem>
In one embodiment of the present invention, an actuator substrate for partitioning a cavity in which ink is stored, a vibrating membrane supported by the actuator substrate for partitioning the cavity, and a vibrating membrane provided on the vibrating membrane are displaced. A protective substrate having a piezoelectric element that changes the volume of the cavity, an ink supply path that communicates with the cavity, and a first through hole that is fixed to the actuator substrate so as to cover the piezoelectric element and communicates with the ink supply path. Provided is an inkjet apparatus in which the first through hole has a small diameter portion and a large diameter portion having a diameter larger than the small diameter portion in order from the surface facing the actuator substrate.

In one embodiment of the present invention, an actuator substrate for partitioning a cavity in which ink is stored, a vibrating membrane supported by the actuator substrate for partitioning the cavity, and a vibrating membrane provided on the vibrating membrane are displaced. A protective substrate having a piezoelectric element that changes the volume of the cavity, an ink supply path that communicates with the cavity, and a first through hole that is fixed to the actuator substrate so as to cover the piezoelectric element and communicates with the ink supply path. Provided is an inkjet device in which the first through hole has a small diameter portion and a large diameter portion having a diameter larger than the small diameter portion in order from the opposite side of the surface facing the actuator substrate.

In one embodiment of the present invention, the protective substrate has a second through hole having a diameter larger than that of the first through hole.
One embodiment of the present invention includes wiring that is electrically connected to the piezoelectric element, extends over a region outside the cavity, and is partially exposed as a pad, the pad region comprising the pad. It is exposed from the second through hole.

In one embodiment of the invention, the piezoelectric element includes an upper electrode, a lower electrode, and a piezoelectric film sandwiched between the upper electrode and the lower electrode, and the wiring is connected to the upper electrode. The first wiring and the second wiring connected to the lower electrode are included.
In one embodiment of the present invention, the aspect ratio (opening depth / opening width) of the first through hole is 10 times or more the aspect ratio of the second through hole.

In one embodiment of the present invention, the thickness of the protective substrate is 200 μm to 500 μm, the opening width of the first through hole is 30 μm to 50 μm, and the opening width of the second through hole is 300 μm to 300 μm. It is 1500 μm.
In one embodiment of the present invention, the small-diameter portion and the large-diameter portion are connected via a stepped surface arranged in the middle of the protective substrate in the thickness direction.

In one embodiment of the present invention, the stepped surface is arranged substantially at the center in the thickness direction of the protective substrate.
In one embodiment of the present invention, the stepped surface is formed in an annular shape surrounding the small diameter portion.
In one embodiment of the present invention, the protective substrate has a recess in a region covering the piezoelectric element, and the piezoelectric element is arranged in the recess.

One embodiment of the present invention includes a step of forming a first hole portion extending to an intermediate portion in the thickness direction by etching a protective substrate having a first surface and a second surface on the opposite side from the first surface. By etching the protective substrate from the opposite first region of the first hole portion on the second surface of the protective substrate until it penetrates the first hole portion, the first through hole is formed in the first region. The step of forming, the step of preparing an actuator substrate in which the diaphragm having the ink supply path and the piezoelectric element are formed in order from the surface, and the step of preparing the first through hole and the ink supply path so as to coincide with each other in a plan view. Provided is a method for manufacturing an etching apparatus, which comprises a step of fixing the actuator substrate to a protective substrate.

Etching is performed from each of the first surface and the second surface in order to form the first through hole, but the etching depth at one time is shallower than in the case of etching from the first surface to the second surface at once. I'm done. Therefore, the average etching rate up to the formation of the first through hole can be increased. As a result, the etching time required for forming the first through hole can be shortened.

In one embodiment of the present invention, a second through hole is etched from a second region laterally displaced from the first region with an etching width larger than that of the first through hole at the same time as etching the first region. Includes the step of forming.
Since the first hole portion is formed in advance in the formation region of the first through hole having a relatively small etching size, the thickness obtained by subtracting the depth of the first hole portion from the thickness of the protective substrate is formed from the first region. The first through hole can be formed by etching the substrate material. Therefore, although the etching rate differs between the first region and the second region, the timing at which the through holes are formed in each region (that is, the etching completion time) is eliminated, and the first through holes and the second through holes are eliminated. The holes can be formed at approximately the same timing. As a result, the occurrence of overetching can be suppressed or prevented.

In one embodiment of the present invention, when the first through hole is formed, the protective substrate is etched with an etching width different from that of the first hole portion, so that the protective substrate is etched in order from either the first surface or the second surface. A first through hole having a small diameter portion and a large diameter portion having a diameter larger than the small diameter portion is formed.
When etching from the opposite side (first region) of the first hole, if the etching size is almost the same as the first hole, the seam of the through hole (thickness of the protective substrate) may be caused by misalignment. A step may occur in the middle of the direction, and the diameter may be smaller than the design value. Therefore, by setting the processing dimension of the large diameter portion to a size in consideration of the misalignment, it is possible to secure at least the diameter corresponding to the small diameter portion. Therefore, by forming the small diameter portion according to the design value of the first through hole, the first through hole having the diameter according to the design value can be obtained. The first hole portion to be formed first may be a large diameter portion or a small diameter portion.

In one embodiment of the present invention, the first hole portion is formed so that the bottom portion is located substantially at the center in the thickness direction of the protective substrate.
One embodiment of the present invention includes a step of forming a first hole portion extending to an intermediate portion in the thickness direction by etching a protective substrate having a first surface and a second surface on the opposite side from the first surface. By etching the protective substrate from the opposite first region of the first hole portion on the second surface of the protective substrate until it penetrates the first hole portion, the first through hole is formed in the first region. Provided is a method for manufacturing a protective substrate for an etching apparatus, which includes a step of forming.

Etching is performed from each of the first surface and the second surface in order to form the first through hole, but the etching depth at one time is shallower than in the case of etching from the first surface to the second surface at once. I'm done. Therefore, the average etching rate up to the formation of the first through hole can be increased. As a result, the etching time required for forming the first through hole can be shortened.

In one embodiment of the present invention, a second through hole is etched from a second region laterally displaced from the first region with an etching width larger than that of the first through hole at the same time as etching the first region. Includes the step of forming.
Since the first hole portion is formed in advance in the formation region of the first through hole having a relatively small etching size, the thickness obtained by subtracting the depth of the first hole portion from the thickness of the protective substrate is formed from the first region. The first through hole can be formed by etching the substrate material. Therefore, although the etching rate differs between the first region and the second region, the timing at which the through holes are formed in each region (that is, the etching completion time) is eliminated, and the first through holes and the second through holes are eliminated. The holes can be formed at approximately the same timing. As a result, the occurrence of overetching can be suppressed or prevented.

In one embodiment of the present invention, when the first through hole is formed, the protective substrate is etched with an etching width different from that of the first hole portion, so that the protective substrate is etched in order from either the first surface or the second surface. A first through hole having a small diameter portion and a large diameter portion having a diameter larger than the small diameter portion is formed.
By setting the processing dimension of the large diameter portion to a size that takes into consideration the misalignment, it is possible to secure at least the diameter corresponding to the small diameter portion. Therefore, by forming the small diameter portion according to the design value of the first through hole, the first through hole having the diameter according to the design value can be obtained.

In one embodiment of the present invention, the first hole portion is formed so that the bottom portion is located substantially at the center in the thickness direction of the protective substrate.

1 Inkjet head 2 Actuator board 2a Front side 2b Back side 3 Nozzle board 4 Protective board 5 Cavity 6 Vibrating film 7 Piezoelectric element 8 Recess 9 Ink ejection passage 10 Adhesive 11 Facing surface 12 Storage recess 13 Ink supply path 14 Ink supply path 15 Vibration Membrane forming layer 16 Ink flow direction 17 Common ink passage 18 Lower electrode 18A Main electrode part 18B Extension part 19 Piezoelectric film 19A Main part 19B Extension part 20 Upper electrode 21 First hydrogen barrier film 22 Second hydrogen barrier film 23 Interlayer film 24 Wiring Membrane 25 Upper Wiring 26 Lower Wiring 27 Dummy Wiring 28 Through Hole 29 Through Hole 30 Passion Membrane 31 Pad Opening 32 Pad Opening 33 Opening 34 Through Hole 35 Through Hole 36 Through Hole 37 Drilling Part 38 Large Diameter Part 39 Small Diameter Part 40 Step Surface 41 1st area 42 2nd area 43 Boundary area 44 Leg 45 Thermal oxide film 46 Hole 47 Oxide film 48 Resist film 49 Support substrate 50 Resist film 51 Groove 52 Embankment 53 Step structure 54 Radial part 55 Seam 56 Step

Claims (12)

An actuator board that partitions the cavity where ink is stored, and
A vibrating membrane supported by the actuator substrate and partitioning the cavity,
A piezoelectric element provided on the vibrating membrane and including an upper electrode, a lower electrode, and a piezoelectric film sandwiched between the upper electrode and the lower electrode.
In a region facing the cavity and where the upper electrode is not arranged, the piezoelectric film and the lower electrode are penetrated and communicated with a common ink passage which is a space bordering the top wall of the cavity. An ink supply path, which is a space that communicates with one end of the cavity via an ink passage and borders the top wall of the cavity extending in parallel with the vibrating membrane.
A nozzle opening that supports the actuator substrate to partition the cavity and communicates with the cavity, and a first diameter provided between the cavity and the nozzle opening and formed on the cavity side and the nozzle opening side. Including a nozzle substrate having a recess formed in the first diameter and having a second diameter smaller than the first diameter.
A plurality of the ink supply paths overlap the common ink passage,
The piezoelectric film extends over a region covering the entire cavity and surrounds the ink supply path so as to form a part of the inner surface of the ink supply path.
The upper electrode is restricted to the inner region of the cavity.
An inkjet device that extends over a region that covers the entire cavity and surrounds the ink supply path so as to form a portion of the inner surface of the ink supply path. The lower electrode comprises a contact that is integrally pulled out into the outer region of the cavity.
The inkjet device according to claim 1, wherein the piezoelectric film surrounds the contact portion. The inkjet device according to claim 1 or 2, wherein the piezoelectric film is a PZT film. The inkjet device according to claim 3, wherein the thickness of the piezoelectric film is 1 μm to 5 μm. The inkjet device according to any one of claims 1 to 4, wherein the vibrating film is made of a single SiO ₂ film. The inkjet device according to any one of claims 1 to 4, wherein the vibrating film is made of a SiN / SiO ₂ laminated film. The inkjet device according to any one of claims 1 to 6, wherein the upper electrode is made of a single Pt film. The inkjet device according to any one of claims 1 to 7, wherein the lower electrode is made of a Pt / Ti laminated film. The inkjet device according to any one of claims 1 to 8, further comprising a protective substrate fixed to the actuator substrate so as to cover the piezoelectric element and having a first through hole communicating with the ink supply path. The inkjet device according to claim 9, wherein the first through hole has a large diameter portion and a small diameter portion having a diameter smaller than the large diameter portion in order from the surface facing the actuator substrate. The process of forming a vibrating film on the actuator substrate,
A step of forming a lower electrode film, a piezoelectric film, and an upper electrode film on the vibrating membrane in this order,
A step of forming an upper electrode having a predetermined shape by selectively etching the upper electrode film, and
A step of selectively etching the piezoelectric film so as to remain in the region surrounding the upper electrode.
A step of penetrating the piezoelectric film and the lower electrode film in a region where the upper electrode is not arranged, and forming an ink supply path in which a part of the inner surface is formed by the piezoelectric film and the lower electrode film. ,
A step of etching the actuator substrate from below to form a cavity so as to cover the entire upper electrode and the ink supply path and to be limited to the inner region of the piezoelectric film after etching. A method of manufacturing an inkjet device, including. The method for manufacturing an inkjet device according to claim 11, wherein the piezoelectric film is selectively etched so as to expose a part of the lower electrode film as a contact portion.

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