Actuator, liquid ejecting head, and method for manufacturing actuator

Abstract

The invention discloses an actuator, a liquid ejecting head, and a method for manufacturing the actuator. An actuator has a first electrode, a piezoelectric body, and a second electrode in this order on a surface of a substrate, and an insulating film covering at least a side surface of the piezoelectric body. The actuator has a plurality of inclined surfaces inclined with respect to the substrate at an end of a surface of the first electrode opposite to the substrate, and an angle between the substrate and a first inclined surface farthest from the substrate among the plurality of inclined surfaces is smaller than an angle between the substrate and any other inclined surface among the inclined surfaces.

Description

Technical Field

[0001] The present disclosure relates to an actuator, a liquid ejection head, and a method for manufacturing an actuator. Background Art

[0002] An actuator using a piezoelectric body that changes its shape when an electric field is applied is used as a component for slightly and accurately moving or vibrating an object in various industrial products. For example, piezoelectric bodies are used in small speakers, hard disk drives, printers (liquid ejection devices), etc. Some printers use a piezoelectric body in a liquid ejection head that ejects droplets. Such a liquid ejection head ejects droplets by driving a piezoelectric body by applying an electric field to the piezoelectric body from upper and lower electrodes formed to sandwich the piezoelectric body from above and below. Further, in order to prevent damage to the driven piezoelectric body, for example, the piezoelectric body may be formed to cover an end portion of a lower electrode having an inclined surface (see, for example, Japanese Patent Laid-Open No. 2005-35282 (Document 1)).

[0003] Forming an inclined surface at an end portion of the upper surface of the lower electrode as in Document 1 is preferable because it improves the coverability of an insulating film covering the lower electrode and the piezoelectric body. However, a portion of the piezoelectric body covering the inclined surface of the lower electrode tends to have non-uniform orientation. For this reason, a region of the piezoelectric body overlapping with the inclined surface of the lower electrode may not become an effective region where the piezoelectric body can be driven as designed. In particular, in the case where only one inclined surface is formed at an end portion of the upper surface of the lower electrode, reducing the inclination angle of the inclined surface of the lower electrode to improve the coverability of the insulating film increases the horizontal length of the inclined surface, and thus the piezoelectric body may have a narrow effective region where the piezoelectric body can be driven as designed. In contrast, forming the shape of the end portion of the lower electrode at a right angle in order not to shorten the effective region of the piezoelectric body reduces the coverability of the insulating film, and thus may reduce the reliability of the actuator. Summary of the Invention

[0004] An actuator according to an aspect of the present disclosure has a first electrode, a piezoelectric body, and a second electrode that are sequentially located on a surface of a substrate, and an insulating film that covers at least a side surface of the piezoelectric body. The actuator has a plurality of inclined surfaces that are inclined with respect to the substrate at an end portion of a surface of the first electrode opposite to the substrate, and an angle between the substrate and a first inclined surface that is the farthest from the substrate among the plurality of inclined surfaces is smaller than an angle between the substrate and any other inclined surface among the inclined surfaces.

[0005] More features of the present disclosure will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Brief Description of the Drawings

[0006] Figure 1 is a perspective view schematically showing a liquid ejection device;

[0007] Figure 2A and Figure 2B is a schematic diagram showing the flow path configuration of a liquid ejection head;

[0008] Figure 3 is a schematic cross-sectional view showing an actuator;

[0009] Figure 4 is a schematic cross-sectional view showing an actuator;

[0010] Figure 5 is a schematic cross-sectional view showing an actuator;

[0011] Figure 6 is a schematic cross-sectional view showing an actuator;

[0012] Figures 7A to 7D is a step-by-step cross-sectional view showing the process of manufacturing an actuator;

[0013] Figure 8A and Figure 8B is a step-by-step cross-sectional view showing the process of manufacturing an actuator;

[0014] Figures 9A to 9D is a step-by-step cross-sectional view showing the process of manufacturing an actuator; and

[0015] Figure 10A and Figure 10B illustrates a step-by-step cross-sectional view of the process of manufacturing an actuator. Detailed Description of the Embodiments

[0016] Various exemplary embodiments, features, and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the following embodiments do not limit the matters of the present disclosure, and not all combinations of the features described in the following embodiments are necessary for the solution provided by the present disclosure. Note that the same reference numerals are used to describe the same components.

[0017] <<Embodiment 1>>

[0018] <Configuration of the Liquid Ejection Device>

[0019] Figure 1 is a perspective view schematically showing a part of a liquid ejection device (not shown). The liquid ejection device of this embodiment is a one-pass type liquid ejection device that prints an image on the print medium 1 when the print medium 1 moves once. The liquid ejection device includes a liquid ejection head 4 as a full-line head having element substrates arranged over the entire width of the print medium 1, and each element substrate has ejection ports for ejecting liquid. The print medium 1 is conveyed by a conveyance unit 2 in the direction indicated by the arrow (+Y direction) and is printed by the liquid ejection head 4. The liquid ejection head 4 of this embodiment can be implemented in any manner, including Figure 1 the example shown inFigure 1 In the example shown, a liquid ejection device having eight liquid ejection heads 4 (4Ka, 4Kb, 4Ya, 4Yb, 4Ma, 4Mb, 4Ca, and 4Cb) is shown. These eight liquid ejection heads 4 are positioned inside the liquid ejection device by reference members.

[0020] As described earlier, the liquid ejection head 4 of the present embodiment is a one-pass type head or a so-called page-width type head, and its length is the same as the width of the print medium 1. Note that the width of the print medium 1 is a dimension measured in a direction (X direction) orthogonal to the direction in which the print medium 1 is conveyed. The liquid ejection head may be a so-called serial liquid ejection head that performs printing on the print medium while scanning the liquid ejection head. In an example configuration of the serial liquid ejection head, the liquid ejection head includes an element substrate for black ink and an element substrate for color ink. In another example configuration of the serial liquid ejection head, several element substrates are arranged such that the ejection ports can overlap in the direction in which the ejection port array is arranged. In this configuration, the width of the liquid ejection head is narrower than the width of the print medium.

[0021] <Flow channel configuration of the liquid ejection head>

[0022] Figure 2A and Figure 2B are schematic views showing the flow channel configuration of the element substrate 50 of the liquid ejection head 4 of the present embodiment. Figure 2A is a cross-sectional view of the element substrate 50 seen from the ejection port 11 side of the flow channel block 10. Figure 2B is along Figure 2A The cross-sectional view taken along IIB-IIB in. The element substrate 50 includes three substrates (the first flow channel substrate 20, the second flow channel substrate 100, and the third flow channel substrate 40), and these substrates are combined to form the flow channels. As Figure 2A shown in, the flow channel block 10 includes ejection ports 11 arranged in the Y direction and pressure chambers 12 and supply channels 13 prepared to communicate with the corresponding ejection ports 11. Each of the supply channels 13 is connected to a common liquid chamber 14 and supplies liquid (hereinafter also referred to as ink) to the corresponding pressure chamber 12. Figure 2A and Figure 2B The arrows in show the flow of the liquid (ink).

[0023] As Figure 2BAs shown, in this embodiment, the component substrate 50 is configured such that the first flow channel substrate 20, the second flow channel substrate 100, and the third flow channel substrate 40 are stacked in the Z direction. The first flow channel substrate 20 is a substrate including ejection ports 11 for ejecting ink. The second flow channel substrate 100 is a substrate formed with piezoelectric elements 140 and pressure chambers 12. The third flow channel substrate 40 is a substrate that isolates the piezoelectric body 400 of the piezoelectric element 140 from the ink, and is also a substrate including a flow channel through which ink is supplied from the common liquid chamber 14 to the pressure chamber 12.

[0024] Supply channels 13, pressure chambers 12, and ejection ports 11 are formed corresponding to each piezoelectric element 140. Adjacent pressure chambers 12 are separated from each other by partition walls and are not directly affected by their adjacent piezoelectric elements 140. Note that the piezoelectric elements 140 are formed adjacent to the insulating film 200 serving as a diaphragm.

[0025] In a steady state, the ink contained in the pressure chamber 12 forms a meniscus at the ejection port 11. When a voltage waveform is applied to the piezoelectric element 140 according to an ejection signal, the piezoelectric element 140 deforms, allowing the pressure chamber 12 to expand or contract. By combining the expansion operation and the contraction operation, droplets (ink droplets) 60 are generated from the meniscus and ejected in the -Z direction.

[0026] After the ink in the pressure chamber 12 is consumed by the ejection operation, the ink is supplied from the common liquid chamber 14 due to the capillary action of the ejection port 11 and forms a meniscus at the ejection port 11 again. Note that in this embodiment, the ejection port 11, the piezoelectric element 140, and the pressure chamber 12 are collectively referred to as an ejection element.

[0027] The specific dimensions of an example describing the above structure of this embodiment are described. The ejection elements - that is, the piezoelectric elements 140, the ejection ports 11, and the pressure chambers 12 are arranged in the Y direction at a density of 150 nozzles per inch (npi). Each piezoelectric element 140 is approximately 500 micrometers (μm) in terms of its size (length) in the X direction and approximately 110 μm in terms of its size (width) in the Y direction. The diameter of the ejection port 11 is 25 μm and the thickness is 30 μm, and the thickness of the first flow channel substrate 20 is 100 μm. The pressure chamber 12 is 550 μm in terms of its size (length) in the X direction, 120 μm in terms of its size (width) in the Y direction, and 100 μm in terms of its size (height) in the Z direction. Additionally, the viscosity of the ink used is 4 cp, and the minimum ink ejection amount from each inkjet port 11 is 3 pl.

[0028] In this embodiment, the driving frequency of each piezoelectric element 140 can be 30 kHz. Such a driving frequency can be appropriately set based on the time required for each ejection element to be refilled with new ink and be ready for the next ejection operation after actually ejecting ink when a voltage is applied to the piezoelectric element 140.

[0029] The liquid ejection head 4 is formed by an array of a plurality of element substrates, and each element substrate is formed by an array of a plurality of ejection elements. Each element substrate is generally connected to a flexible wiring board (not shown) and further connected to an electrical wiring board (not shown). The electrical wiring board has a power supply terminal for supplying power and a signal input terminal for receiving ejection signals. At the same time, a circulation flow path (not shown) is formed in an ink supply unit (not shown) to supply ink containing a color material and supplied from an ink tank (not shown) to each element substrate and collect the ink not consumed during printing.

[0030] With the above configuration, based on the print data input from the signal input terminal, each of the ejection elements disposed at the element substrate 50 ejects the ink supplied from the ink supply unit in the -Z direction from the ejection port using the power supplied from the power supply terminal. Note that the dimensional values of each of the above parts are only examples and can be changed as required according to various specifications.

[0031] Examples of the liquid ejection head 4 of the liquid ejection device include an inkjet print head of a printer (image printing device). However, the liquid ejected from the liquid ejection head 4 is not limited to ink. For example, the liquid ejection head 4 can eject a primer.

[0032] An actuator 700 configured such that the piezoelectric element 140 can be deformed by being driven is used in the liquid ejection head 4 of the liquid ejection device. The configuration of the actuator of the piezoelectric body described in this embodiment has high reliability and a large effective area by forming a plurality of inclined surfaces at the end of the upper surface of the first electrode covered with the piezoelectric body. Note that, as described earlier, the effective area of the piezoelectric body is the area where the piezoelectric body can be driven (deformed) as designed.

[0033] <Configuration of the actuator>

[0034] Figure 3 is an enlarged cross-sectional view schematically showing a part of the actuator 700 of this embodiment. To more easily understand the configuration of the actuator 700, Figure 3 only the second flow path substrate 100 of the element substrate 50 is shown in a simplified manner.

[0035] As Figure 3As shown, the actuator 700 of the present embodiment includes an insulating film 200, a first electrode 300, a piezoelectric body 400, a second electrode 500, and an insulating film 600. The insulating film 200, the first electrode 300, the piezoelectric body 400, the second electrode 500, and the insulating film 600 are sequentially placed on one surface of the second flow channel substrate 100. The insulating film 600 covers at least the side surface of the piezoelectric body 400. Note that the first electrode 300, the piezoelectric body 400, and the second electrode 500 form the piezoelectric element 140 described above. At the surface of the second flow channel substrate 100 opposite to the actuator 700, a recess 110 for forming the pressure chamber 12 is formed. The piezoelectric body 400 is disposed to overlap at least a part of the recess 110. In addition, the insulating film 200 formed on the upper surface of the second flow channel substrate 100 may be referred to as a substrate insulating film, and the insulating film 600 that covers at least the side surface of the piezoelectric body 400 may be referred to as a piezoelectric body insulating film.

[0036] Note that it is preferable that the second flow channel substrate 100 has a flat surface. The material to be used for the second flow channel substrate 100 is appropriately selected from, for example, silicon, silicon carbide, quartz, gallium nitride, gallium arsenide, indium phosphide, sapphire, etc. To facilitate the formation of the recess 110, a silicon-on-insulator (SOI) wafer may be used as the second flow channel substrate 100. The SOI wafer has a silicon oxide layer formed on a silicon substrate and a silicon layer formed on the silicon oxide layer. The silicon oxide layer is also referred to as a buried oxide (BOX) layer. The layer thickness of the silicon oxide layer can be selected from between several tens of nanometers and several hundreds of micrometers. The layer thickness of the silicon layer can also be selected relatively freely. In the case where the layer thickness of the silicon oxide layer and the layer thickness of the silicon layer are appropriately combined and the silicon oxide layer is used as an etching stop layer, only the silicon layer can be removed by selective etching. Such etching produces a recess 110 whose bottom surface is the surface of the silicon oxide layer. This makes it possible to easily form a recess 110 having a very flat bottom surface.

[0037] The insulating film 200 is formed on the upper surface of the second flow channel substrate 100. Materials that can be used for the insulating film 200 are, for example, typical insulating materials such as silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide, or tetraethyl orthosilicate. Note that in the case where the material of the second flow channel substrate 100 is conductive, the insulating film 200 is preferably formed between the first electrode 300 and the second flow channel substrate 100. At the same time, in the case where the material of the second flow channel substrate 100 is an insulator, this structure may not have the insulating film 200. In other words, in the case where the material of the second flow channel substrate 100 is an insulator, the actuator 700 does not need to have the insulating film 200. Note that in the case where the actuator 700 does not have the insulating film 200, the bottom of the recess 110 of the second flow channel substrate 100 can function as a diaphragm.

[0038] The first electrode 300 is formed on the upper surface of the insulating film 200. The first electrode 300 is formed in a rectangular shape that is longer in the X direction than in the Y direction when viewed from above (Z direction) the second flow channel substrate 100. Note that when the material of the second flow channel substrate 100 is an insulator, the first electrode 300 can be formed on the upper surface of the second flow channel substrate 100. The first electrode 300 is also referred to as the lower electrode. In the manufacturing process of the actuator 700, the first electrode 300 may be exposed to a high temperature of several hundred degrees Celsius. In this case, it is preferable that a material having a high melting temperature be used as the material of the first electrode 300. Examples of such materials include copper (Cu), platinum (Pt), gold (Au), chromium (Cr), cobalt (Co), and titanium (Ti). Additionally, examples of the material of the first electrode 300 include alloys of copper, platinum, gold, chromium, cobalt, or titanium. The material of the first electrode 300 may be a multilayer body of any one of copper, platinum, gold, chromium, cobalt, and titanium.

[0039] When the piezoelectric body 400 is formed in contact with the upper surface of the first electrode 300, the first electrode 300 can also be used as a film for controlling the alignment of the crystal orientation of the piezoelectric body 400. In this case, as the material of the first electrode 300, a material having an appropriate crystal structure is selected as needed according to the material of the piezoelectric body 400. Note that the film for controlling the alignment of the crystal orientation of the piezoelectric body 400 is also referred to as a crystal orientation control film. For example, when the material of the piezoelectric body 400 is lead zirconate titanate (PZT), platinum is preferably used as the material of the first electrode 300 that also serves as the crystal orientation control film. A typical film formation method such as magnetron sputtering can be used to form the film of the first electrode 300 using platinum as the material. In forming the film of the first electrode 300, the film thickness of the first electrode 300 is adjusted as needed so that the piezoelectric body 400 can obtain a desired orientation. When the material of the first electrode 300 is platinum, as an adhesion layer for improving the adhesion strength between the first electrode 300 and the insulating film 200, a layer of a multilayer body of any one of titanium, titanium oxide, etc. or an alloy layer of titanium, titanium oxide, etc. can be formed between the first electrode 300 and the insulating film 200.

[0040] Furthermore, the first electrode 300 can be a multilayer body having an adhesion layer for improving the adhesion strength with the insulating film 200 and a conductive layer laminated on the upper surface of the adhesion layer. In this case, thin films such as titanium and chromium can be used as the material of the adhesion layer, and metal materials such as copper, platinum, gold, chromium, cobalt, or titanium can be used as the material of the conductive layer. The material of the conductive layer can also be an alloy of copper, platinum, gold, chromium, cobalt, or titanium. As described earlier, when the piezoelectric body 400 is formed in contact with the upper surface of the conductive layer, as the material of the conductive layer that also serves as the crystal orientation control film, a material having an appropriate crystal structure can be selected as needed according to the material of the piezoelectric body 400.

[0041] A plurality of inclined surfaces, for example, two inclined surfaces 301 and 302, are formed at the +X direction end portion of the upper surface of the first electrode 300. Note that a plurality of inclined surfaces are similarly formed at the +Y direction end portion and the -Y direction end portion of the upper surface of the first electrode 300. The plurality of inclined surfaces formed at the +Y direction end portion and the -Y direction end portion have the same configuration as the inclined surfaces formed at the +X direction end portion, and thus are not shown or described.

[0042] In the present embodiment, the inclined surface of the two inclined surfaces 301 and 302 that is the farthest from the second flow channel substrate 100 in the +Z direction is referred to as the first inclined surface 301, and the inclined surface of the two inclined surfaces 301 and 302 that is the second farthest from the second flow channel substrate 100 in the +Z direction is referred to as the second inclined surface 302. The angle between the first inclined surface 301 and the second flow channel substrate 100 is referred to as the first angle θ1, and the angle between the second inclined surface 302 and the second flow channel substrate 100 is referred to as the second angle θ2. Note that the angle between each inclined surface of the first electrode 300 and the second flow channel substrate 100 is the angle between the inclined surface of the first electrode 300 and the flat surface on the second flow channel substrate 100. For example, as Figure 3 shown, the angle between each inclined surface of the first electrode 300 and the second flow channel substrate 100 may be the angle between the inclined surface of the first electrode 300 and the upper surface of the insulating film 200. The angle between each inclined surface of the first electrode 300 and the second flow channel substrate 100 may be the angle between the inclined surface of the first electrode 300 and the upper surface of the second flow channel substrate 100.

[0043] The first inclined surface 301 is formed as a flat surface that extends long in the Y direction. The first inclined surface 301 extends obliquely downward from the edge portion of the portion of the upper surface of the first electrode 300 that is parallel to the second flow channel substrate 100. The second inclined surface 302 is formed as a flat surface that extends long in the Y direction and is arranged side by side with the first inclined surface 301. The second inclined surface 302 extends obliquely downward from the lower edge portion of the first inclined surface 301. In addition, the first angle θ1 is smaller than the second angle θ2. For example, the first angle θ1 is preferably 12 degrees or more and 22 degrees or less, and the second angle θ2 is preferably 27 degrees or more and 37 degrees or less.

[0044] The piezoelectric body 400 is formed on the upper surface of the first electrode 300, or in other words, on the surface of the first electrode 300 that faces the insulating film 200 (second flow channel substrate 100). The piezoelectric body 400 covers the upper surface of the first electrode 300 including the two inclined surfaces 301, 302. The portions of the piezoelectric body 400 covering the two inclined surfaces 301, 302 extend along the two inclined surfaces 301, 302 and thus are inclined with respect to the second flow channel substrate 100. Lead zirconate titanate capable of large deformation is mainly used as the material of the piezoelectric body 400. Piezoelectric materials other than lead zirconate titanate can also be used as the material of the piezoelectric body 400. Examples of the piezoelectric material of the piezoelectric body 400 include barium titanate, lead titanate, lead metaniobate, bismuth titanate, zinc oxide, aluminum nitride, and sodium potassium niobate.

[0045] The film of the piezoelectric body 400 is formed using a typical film formation method such as sputtering or spin coating. The thickness of the piezoelectric body 400 is preferably about 2 μm. In the case where the film of the piezoelectric body 400 is formed by coating, the piezoelectric body 400 is formed of several layers. After the film of the piezoelectric body 400 is formed, the piezoelectric body 400 is baked so that the piezoelectric body 400 can have a desired crystal orientation. The temperature for baking the piezoelectric body 400 is selected as needed according to the piezoelectric material. In the case where the material of the piezoelectric body 400 is lead zirconate titanate, the temperature for baking the piezoelectric body 400 can be in the range from 600°C to 900°C. After the piezoelectric body 400 is baked, etching such as wet etching or dry etching is performed to process the piezoelectric body 400 into a desired device shape. The position of the end of the piezoelectric body 400 formed by etching can be on the plurality of inclined surfaces of the first electrode 300, or on the insulating film 200 beyond the +X direction end of the first electrode 300. In addition, the +X direction end of the piezoelectric body 400 can cover all or part of the plurality of inclined surfaces of the first electrode 300.

[0046] The second electrode 500 is formed on the upper surface of the piezoelectric body 400, or in other words, on the surface of the piezoelectric body 400 that faces the first electrode 300. A typical electrode material having conductivity can be used as the material of the second electrode 500. For example, a metal material such as aluminum (Al), tungsten (W), copper, titanium, chromium, gold, or platinum can be used as the material of the second electrode 500. In the case where the piezoelectric body 400 may be bent due to the internal stress in the first electrode 300 increased during the formation of the first electrode 300, the second electrode 500 can be given an internal stress in a direction opposite to that of the first electrode 300. This enables the second electrode 500 to have the function of eliminating the stress applied to the piezoelectric body 400. Examples of the material of the second electrode 500 that can be given an internal stress in a direction opposite to that of the first electrode 300 include titanium tungsten alloy. Note that the upper wiring 801 is electrically connected to the +X direction portion of the second electrode 500. The lower wiring 802 (seeFigure 8A and Figure 8B ) the portion of the first electrode 300 that protrudes in the -X direction beyond the piezoelectric body 400 and is electrically connected thereto.

[0047] An insulating film 600 is formed to cover the upper surface of the second electrode 500, the side surfaces of the piezoelectric body 400, the upper surface of a part of the first electrode 300, and the upper surface of a part of the insulating film 200. The insulating film 600 is disposed between the upper wiring 801 and the second electrode 500, between the upper wiring 801 and the piezoelectric body 400, between the lower wiring 802 and the first electrode 300, and between the upper wiring 801 (or the lower wiring 802) and the insulating film 200. Note that the insulating film 600 covers the portion of the upper surface of the first electrode 300 that protrudes in the -X direction beyond the piezoelectric body 400, including a plurality of surfaces formed at the -X direction end portion of the upper surface of the first electrode 300. In addition, in the case where a part of a plurality of inclined surfaces of the first electrode 300 at the end portion of the piezoelectric body 400 is covered, the insulating film 600 covers the remaining portions of the plurality of inclined surfaces of the first electrode 300. In other words, the insulating film 600 covers the portion of the upper surface of the first electrode 300 that is not covered by the piezoelectric body 400. Similar to the insulating film 200 formed on the upper surface of the second flow channel substrate 100, materials advantageously used for the insulating film 600 are silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide, tetraethyl orthosilicate, etc. In addition, the material of the insulating film 600 may be a multilayer film of any one of silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide, and tetraethyl orthosilicate. For example, the material of the insulating film 600 may be a multilayer film having an aluminum oxide film formed in contact with the second electrode 500 and the first electrode 300 and a silicon oxide film formed to cover the aluminum oxide film.

[0048] In order to sufficiently displace the piezoelectric body 400, it is preferable that the potential difference applied between the second electrode 500 (upper wiring 801) and the first electrode 300 (lower wiring 802), that is, the potential difference applied in the direction of the film thickness of the piezoelectric body 400, is about 30 V or greater. In the case where the piezoelectric body 400 is formed using a semiconductor, a relatively large potential difference is applied to the semiconductor device in order to displace the piezoelectric body 400. At the same time, the breakdown electric field strength of the insulating film 600 is about 10 megavolts per centimeter (MV / cm). Therefore, making the film thickness of the insulating film 600 30 nanometers (nm) or greater can reduce the probability of damage to the actuator 700. In order to form an insulating film 600 thick enough without causing breakdown with good productivity, chemical vapor deposition (CVD) or sputtering is generally used as the film formation method for the insulating film 600.

[0049] In order to displace the piezoelectric body 400 by applying a desired voltage to the second electrode 500 and the first electrode 300, the second electrode 500 is electrically connected to the upper wiring 801, and the first electrode 300 is electrically connected to the lower wiring 802. At a portion of the insulating film 600 that covers the second electrode 500, an upper through-hole 601 penetrating in the vertical direction (Z direction) is formed. One end of the upper wiring 801 is inserted through the upper through-hole 601 and joined to the second electrode 500. At a portion of the insulating film 600 that covers the first electrode 300, a lower through-hole 602 penetrating in the vertical direction (Z direction) is formed (see Figure 7D ). One end of the lower wiring 802 is inserted through the lower through-hole 602 and joined to the first electrode 300.

[0050] A commonly used metal material can be used as the material of the upper wiring 801 and the lower wiring 802. For example, metal materials such as aluminum, copper, or gold can be used as the material of the upper wiring 801 and the lower wiring 802. Examples of the material of the upper wiring 801 and the lower wiring 802 include alloys of aluminum, copper, or gold. In addition, in order to improve the adhesion strength between the upper wiring 801 and the lower wiring 802 and the insulating film 600, thin films such as titanium and chromium can be formed between the upper wiring 801 and the insulating film 600 and between the lower wiring 802 and the insulating film 600.

[0051] As described earlier, in order to displace the piezoelectric body 400 sufficiently, a relatively high voltage is preferably applied to the second electrode 500 and the first electrode 300. In addition, due to the high surface density of the plurality of actuators 700 provided at the chip-type liquid ejection head (element substrate 50), when current flows through the surface of the element substrate 50 in a high-humidity environment, the actuators 700 may be damaged. Therefore, the upper wiring 801 and the lower wiring 802 are preferably covered with a passivation film 900 having high insulation. A material having high insulation (such as silicon dioxide, silicon nitride, or aluminum oxide) is advantageously used as the material of the passivation film 900. In the liquid ejection head, the passivation film 900 is preferably moisture-resistant. For example, a passivation film partially including a silicon nitride film is preferred because it has higher moisture resistance than a passivation film formed of a silicon oxide film. Compared with a passivation film formed of a silicon oxide film, even when the film thickness is small, a passivation film partially including a silicon nitride film can have sufficient moisture resistance and insulation. Using a moisture-resistant passivation film can help prevent the high-humidity environment from affecting the displacement performance of the piezoelectric body 400.

[0052] Note that it is difficult to planarize the upper wiring 801 and the lower wiring 802 formed on the upper surface of the insulating film 600, such as by chemical mechanical polishing (CMP), because this may affect the displacement performance of the piezoelectric body 400. Accordingly, a step shape based on the upper through hole 601 appears at the surface of the upper wiring 801, and a step shape based on the lower through hole 602 appears at the surface of the lower wiring 802. Therefore, the passivation film 900 covers steps of 30 nm or more generated at portions of the upper wiring 801 inserted through the upper through hole 601 and steps of 30 nm or more generated at portions of the lower wiring 802 inserted through the lower through hole 602.

[0053] In the present embodiment, the first electrode 300 is processed to an appropriate size according to the design. In this case, controlling the shape of the end portion of the first electrode 300 can improve the coverability of the insulating film 600 covering the side surface of the piezoelectric body 400 formed on the upper surface of the first electrode 300, and thus expand the effective area of the piezoelectric body 400.

[0054] If the end portion of the first electrode 300 has a right-angled structure, voids may be generated at the step portion of the insulating film 600 covering the upper surface of the second electrode 500 and the +X direction side surface of the piezoelectric body 400, which may reduce the coverability of the insulating film 600 and thus may reduce the reliability. The portion of the piezoelectric body 400 away from the second flow channel substrate 100 is displaced as a free end, and thus is displaced more greatly than the portion of the piezoelectric body 400 close to the second flow channel substrate 100. For this reason, when the piezoelectric body 400 is driven, stress concentration may occur at the piezoelectric body 400 and the insulating film 600.

[0055] In the present embodiment, a plurality of inclined surfaces, for example, two inclined surfaces 301 and 302, are formed at the end portion of the upper surface of the first electrode 300. Since the insulating film 600 extends along the two inclined surfaces 301 and 302 of the first electrode 300, the height change at the step portion of the insulating film 600 covering the upper surface of the second electrode 500 and the +X direction side surface of the piezoelectric body 400 is gentle. The formation of the two inclined surfaces 301 and 302 at the end portion of the upper surface of the first electrode 300 can improve the coverability of the insulating film 600 covering the +X direction side surface of the piezoelectric body 400, and thus enhance the reliability. The formation of the two inclined surfaces 301 and 302 at the end portion of the upper surface of the first electrode 300 can also shorten the horizontal length of the two inclined surfaces 301 and 302. This enables the area of the piezoelectric body 400 overlapping with the two inclined surfaces 301 and 302 to be smaller, which means a larger effective area of the piezoelectric body 400 and a higher actuation efficiency of the piezoelectric body 400.

[0056] In addition, the angle (first angle θ1) between the first inclined surface 301 and the second flow channel substrate 100 is smaller than the angle (second angle θ2) between the second inclined surface 302 and the second flow channel substrate 100. Since the inclination angle of the inclined surface gradually increases toward the second flow channel substrate 100 when the inclination angle of the first inclined surface 301, which is the farthest from the second flow channel substrate 100, is the smallest, stress concentration at the piezoelectric body 400 and the insulating film 600 can be reduced when the piezoelectric body 400 is driven. In addition, since the inclination angle of the inclined surface gradually increases toward the second flow channel substrate 100 when the inclination angle of the first inclined surface 301, which is the farthest from the second flow channel substrate 100, is the smallest, the coverability of the portion of the piezoelectric body 400 covering the two inclined surfaces 301 and 302 can be improved. As described earlier, the first angle θ1 is preferably 12 degrees or more and 22 degrees or less, and the second angle θ2 is preferably 27 degrees or more and 37 degrees or less. This enables improvement of the coverability of the insulating film 600 covering the +X direction side surface of the piezoelectric body 400 and shortening of the horizontal lengths of the two inclined surfaces 301 and 302.

[0057] As described earlier, according to the present embodiment, a piezoelectric body 400 having a large effective area and an actuator 700 having high reliability can be provided. Specifically, according to the present embodiment, a plurality of inclined surfaces, namely, two inclined surfaces 301 and 302 are formed at the ends of the upper surface of the first electrode 300. The formation of the two inclined surfaces 301 and 302 at the ends of the upper surface of the first electrode 300 improves the coverability of the insulating film 600 covering the +X direction side surface of the piezoelectric body 400, thus enhancing the reliability. The formation of the two inclined surfaces 301 and 302 at the ends of the upper surface of the first electrode 300 also shortens the horizontal lengths of the two inclined surfaces 301 and 302. This makes the area of the piezoelectric body 400 overlapping with the two inclined surfaces 301 and 302 smaller, which means a larger effective area of the piezoelectric body 400 and a higher actuation efficiency of the piezoelectric body 400. In addition, the angle (first angle θ1) between the first inclined surface 301 and the second flow channel substrate 100 is smaller than the angle (second angle θ2) between the second inclined surface 302 and the second flow channel substrate 100. Since the inclination angle of the inclined surface increases sequentially toward the second flow channel substrate 100 when the inclination angle of the first inclined surface 301, which is the farthest from the second flow channel substrate 100, is the smallest, stress concentration at the piezoelectric body 400 and the insulating film 600 during the driving of the piezoelectric body 400 can be alleviated. In addition, since the inclination angle of the inclined surface increases sequentially toward the second flow channel substrate 100 when the inclination angle of the first inclined surface 301, which is the farthest from the second flow channel substrate 100, is the smallest, the coverability of the portion of the piezoelectric body 400 covering the two inclined surfaces 301 and 302 can be improved. In this way, a piezoelectric body 400 having a large effective area and an actuator 700 having high reliability can be provided.

[0058] Note that the two inclined surfaces 301 and 302 can each be formed as curved surfaces. In other words, the first inclined surface 301 can be formed as a curved surface, and the second inclined surface 302 can be formed as a curved surface. In this case, the boundary portion between the first inclined surface 301 and the second inclined surface 302 is the portion where the angle between the tangent plane of each inclined surface and the second flow channel substrate 100 changes discontinuously. Further, in this case, the first inclined surface 301 is formed in a curved surface shape that is convexly curved in a cross-section (XZ cross-section) seen in the Y direction. The second inclined surface 302 is formed in a curved surface shape that is convexly curved with a curvature larger than that of the first inclined surface 301 in a cross-section seen in the Y direction. As the tangent point where the tangent plane of the first inclined surface 301 intersects the first inclined surface 301 is farther from the second flow channel substrate 100, the angle between the tangent plane of the first inclined surface 301 and the second flow channel substrate 100 becomes smaller. As the tangent point where the tangent plane of the second inclined surface 302 intersects the second inclined surface 302 is farther from the second flow channel substrate 100, the angle between the tangent plane of the second inclined surface 302 and the second flow channel substrate 100 becomes smaller.

[0059] As in the above-described embodiment, this improves the coverability of the insulating film 600 that covers the +X direction side surface of the piezoelectric body 400 and shortens the horizontal lengths of the two inclined surfaces 301 and 302. Further, since the inclination angle of the inclined surface gradually increases toward the second flow channel substrate 100 in the case where the inclination angle of the first inclined surface 301, which is the farthest from the second flow channel substrate 100, is the smallest, stress concentration at the passivation film 900 during driving of the piezoelectric body 400 can be alleviated.

[0060] <First Modified Example>

[0061] Figure 4 FIG. is an enlarged cross-sectional view schematically showing a part of the actuator 700 of the first modified example. The components in the first modified example are configured to be similar to the components in the above-described embodiment, and thus the same reference numerals as those used for the components in the above-described embodiment are used for description. In the first modified example, as another example of the plurality of inclined surfaces, three inclined surfaces 301, 302, and 303 are formed at the +X direction end portion of the upper surface of the first electrode 300. Note that three inclined surfaces are also formed at the +Y direction end portion and the -Y direction end portion of the upper surface of the first electrode 300.

[0062] In the first modification example, among the three inclined surfaces 301, 302, and 303, the inclined surface that is the farthest from the second flow channel substrate 100 in the +Z direction is referred to as the first inclined surface 301. Among the three inclined surfaces 301, 302, and 303, the inclined surface that is the second farthest from the second flow channel substrate 100 is referred to as the second inclined surface 302. Among the three inclined surfaces 301, 302, and 303, the inclined surface that is the third farthest from the second flow channel substrate 100 is referred to as the third inclined surface 303. The angle between the first inclined surface 301 and the second flow channel substrate 100 is referred to as the first angle θ1, the angle between the second inclined surface 302 and the second flow channel substrate 100 is referred to as the second angle θ2, and the angle between the third inclined surface 303 and the second flow channel substrate 100 is referred to as the third angle θ3. Note that, as in the above-described embodiment, the angle between each inclined surface of the first electrode 300 and the second flow channel substrate 100 is the angle between the inclined surface of the first electrode 300 and the flat surface on the second flow channel substrate 100.

[0063] The first inclined surface 301 is formed as a plane that extends long in the Y direction. The first inclined surface 301 extends obliquely downward from the edge portion of the upper surface of the first electrode 300 that is parallel to the second flow channel substrate 100. The second inclined surface 302 is formed as a flat surface that extends long in the Y direction and is arranged side by side with the first inclined surface 301. The second inclined surface 302 extends obliquely downward from the lower edge portion of the first inclined surface 301. The third inclined surface 303 is formed as a flat surface that extends long in the Y direction and is arranged side by side with the first inclined surface 301 and the second inclined surface 302. The third inclined surface 303 extends obliquely downward from the lower edge portion of the second inclined surface 302. In addition, the first angle θ1 is smaller than the second angle θ2 and the third angle θ3. In other words, the second angle θ2 is greater than the first angle θ1, and the third angle θ3 is greater than the second angle θ2. The portion of the piezoelectric body 400 that covers the three inclined surfaces 301, 302, and 303 extends along the three inclined surfaces 301, 302, and 303, and thus is inclined with respect to the second flow channel substrate 100.

[0064] According to the first modification example, as in the above-described embodiment, an actuator 700 having a piezoelectric body 400 with a large effective area and high reliability can be provided.

[0065] In addition, the first angle θ1 is preferably 12 degrees or more and 22 degrees or less. The second angle θ2 is preferably 27 degrees or more and 37 degrees or less. The third angle θ3 is preferably 67 degrees or more and 77 degrees or less. This improves the coverability of the insulating film 600 that covers the +X direction side surface of the piezoelectric body 400 and shortens the horizontal lengths of the three inclined surfaces 301, 302, and 303.

[0066] Note that the three inclined surfaces 301, 302, and 303 can each be formed as curved surfaces. In other words, the first inclined surface 301 can be formed as a curved surface, the second inclined surface 302 can be formed as a curved surface, and the third inclined surface 303 can be formed as a curved surface. In this case, the portions where the angle between the tangent plane of each inclined surface and the second flow channel substrate 100 changes discontinuously are the boundary portions between the first inclined surface 301 and the second inclined surface 302 and between the second inclined surface 302 and the third inclined surface 303. Further, in this case, the first inclined surface 301 is formed in a curved surface shape that is convexly curved in the cross section (XZ cross section) seen in the Y direction. The second inclined surface 302 is formed in a curved surface shape that is convexly curved with a curvature larger than that of the first inclined surface 301 in the cross section seen in the Y direction. The third inclined surface 303 is formed in a curved surface shape that is convexly curved with a curvature larger than that of the second inclined surface 302 in the cross section seen in the Y direction. As the tangent point where the tangent plane of the first inclined surface 301 intersects the first inclined surface 301 is farther from the second flow channel substrate 100, the angle between the tangent plane of the first inclined surface 301 and the second flow channel substrate 100 becomes smaller. As the tangent point where the tangent plane of the second inclined surface 302 intersects the second inclined surface 302 is farther from the second flow channel substrate 100, the angle between the tangent plane of the second inclined surface 302 and the second flow channel substrate 100 becomes smaller. As the tangent point where the tangent plane of the third inclined surface 303 intersects the third inclined surface 303 is farther from the second flow channel substrate 100, the angle between the tangent plane of the third inclined surface 303 and the second flow channel substrate 100 becomes smaller.

[0067] As in the above-described embodiment, this improves the coverability of the insulating film 600 covering the +X direction side surface of the piezoelectric body 400 and shortens the horizontal lengths of the three inclined surfaces 301, 302, and 303. Further, since the inclination angle of the inclined surface gradually increases toward the second flow channel substrate 100 when the inclination angle of the first inclined surface 301, which is the farthest from the second flow channel substrate 100, is the smallest, stress concentration at the passivation film 900 during driving of the piezoelectric body 400 can be reduced.

[0068] Note that four or more inclined surfaces, for example, four inclined surfaces, five inclined surfaces, six inclined surfaces, can be formed at the +X direction end portion of the upper surface of the first electrode 300. In the case where N is an integer of 3 or more and k is an integer of 2 or more and N or less, the angle between the second flow channel substrate 100 and the inclined surface that is the k-th farthest from the second flow channel substrate 100 among the N inclined surfaces is preferably larger than the angle between the second flow channel substrate 100 and the inclined surface that is the (k - 1)-th farthest from the second flow channel substrate 100 among the N inclined surfaces.

[0069] <Second Modified Example>

[0070] Figure 5 is an enlarged cross-sectional view schematically showing a part of the actuator 700 of the second modification. The components in the second modification are configured to be similar to those in the above-described embodiment, and thus the same reference numerals as those used for the components in the above-described embodiment are used for description. As Figure 5 shown, the piezoelectric body 400 of the second modification is formed to extend onto the upper surface of the insulating film 200 beyond the +X direction end of the first electrode 300.

[0071] According to the second modification, as in the above-described embodiment, a piezoelectric body 400 having a large effective area and an actuator 700 having high reliability can be provided.

[0072] Note that, in the case where sputtering is used to form the piezoelectric body 400, for example, as Figure 3 shown, the portion of the piezoelectric body 400 covering the inclined surface of the first electrode 300 tends to be inclined with respect to the second flow channel substrate 100. This enables reduction of the stepped portion of the insulating film 600 that the upper wiring 801 electrically connected to the second electrode 500 needs to cross. Further, even in the case where sputtering is used to form the piezoelectric body 400, depending on the film formation conditions (such as pressure and power) of the piezoelectric body 400, the end portion of the piezoelectric body 400 can be made close to being parallel to the second flow channel substrate 100.

[0073] <Third Modification>

[0074] Figure 6 is an enlarged cross-sectional view schematically showing a part of the actuator 700 of the third modification. The components in the third modification are configured to be similar to those in the above-described embodiment, and thus the same reference numerals as those used for the components in the above-described embodiment are used for description. The piezoelectric body 400 of the third modification is formed by spin coating. As Figure 6 shown, in the case where spin coating is used to form the piezoelectric body 400, the portion of the piezoelectric body 400 covering the inclined surface of the first electrode 300 tends to be inclined less with respect to the second flow channel substrate 100 than in the case where sputtering is used to form the piezoelectric body 400. However, as in the case where sputtering is used to form the piezoelectric body 400, adjusting the coating amount in spin coating, the thickness of the piezoelectric body 400, the viscosity of the piezoelectric body 400, etc. allows the end portion of the piezoelectric body 400 to be inclined with respect to the second flow channel substrate 100. As in the case where sputtering is used to form the piezoelectric body 400, the photolithography step and the etching step in the formation of the upper wiring 801 on the upper surface of the insulating film 600 located above the piezoelectric body 400 are facilitated.

[0075] According to the third modification example, like in the above-described embodiment, an actuator 700 having a piezoelectric body 400 with a large effective area and high reliability can be provided.

[0076] In the above-described embodiment, in the first electrode 300 and the second electrode 500, only the first electrode 300 may be formed of platinum, or both the first electrode 300 and the second electrode 500 may be formed of platinum.

[0077] Although in the above-described embodiment, the actuator 700 is used for the liquid ejection head 4 of the liquid ejection device, the present disclosure is not limited thereto. For example, the actuator can be used for a speaker or a hard disk drive. Further, the actuator can be used for an autofocus mechanism in a portable camera module or an anti-shake function in a digital camera.

[0078] <<Example>>

[0079] Next, a specific example of the actuator 700 will be described using the drawings.

[0080] <Example 1>

[0081] Example 1 is an example corresponding to the above-described embodiment. The configuration and manufacturing method of the actuator 700 in which sputtering is used to form the piezoelectric body 400 are described in Example 1. Note that the components in Example 1 are configured to be similar to the components in the above-described embodiment, and thus the same reference numerals as those used for the components in the above-described embodiment are used for description.

[0082] Figures 7A to 8B is a step-by-step cross-sectional view illustrating the manufacturing process in Example 1. As Figure 7A shown, a substrate 100E made of single crystal silicon is prepared as a raw material for the second flow channel substrate 100. The substrate 100E as a raw material for the second flow channel substrate 100 is hereinafter simply referred to as the substrate 100E. A silicon oxide film having a thickness of 500 nm is formed on the upper surface of the substrate 100E by a wet oxidation method using oxygen and hydrogen (O 2 and H 2 gas) to form an insulating film 200.

[0083] Next, as Figure 7BAs shown in the figure, the first electrode 300 is formed to cover the insulating film 200. In the formation of the first electrode 300, a first film as the raw material of the first electrode 300 is formed on the upper surface of the insulating film 200 by sputtering. After the film formation, a resist pattern is formed lithographically to fabricate the desired pattern of the first electrode 300, and the first electrode 300 is formed by dry etching. By dry etching, a plurality of inclined surfaces (e.g., two inclined surfaces 301, 302) are formed at the end of the upper surface of the first electrode 300. Note that platinum is used as the material of the first electrode 300, and the thickness of the first electrode 300 is 100 nm. As an adhesion layer for improving the adhesion strength between the first electrode 300 and the insulating film 200, a multilayer body of titanium and titanium oxide (not shown) is formed by sputtering.

[0084] Alternatively, three inclined surfaces 301, 302, 303 may be formed at the end of the upper surface of the first electrode 300. In this case, for example, the first angle θ1 may be 17 degrees, the second angle θ2 may be 32 degrees, and the third angle θ3 may be 72 degrees.

[0085] The etching conditions used in the formation of the first electrode 300 are adjusted so that a structure in which the end of the upper surface of the first electrode 300 has a plurality of flat or curved inclined surfaces can be obtained. For example, by depositing reaction products on the etched surface of the first electrode 300 while setting the resist to be retracted during etching and adjusting the etching conditions of the dry etching apparatus, the end of the upper surface of the first electrode 300 can be formed into a desired structure. The etching conditions depend on the configuration of the etching apparatus. For example, the etching conditions may be as follows: RF power, 400 W to 600 W; bias power, 100 W to 200 W; pressure, 0.3 Pa to 1.0 Pa; and the gas used, a mixed gas of chlorine and argon.

[0086] Next, as Figure 7C shown in the figure, a piezoelectric body 400 is formed to cover the first electrode 300, and a second electrode 500 is formed to cover the piezoelectric body 400. The second electrode 500 and the piezoelectric body 400 are formed as follows. A film as the raw material of the piezoelectric body 400 is formed on the upper surface of the first electrode 300 by sputtering. In addition, a second film as the raw material of the second electrode 500 is formed on the upper surface of the film as the raw material of the piezoelectric body 400 by sputtering. After the film formation, a resist pattern is formed lithographically to fabricate the desired patterns of the second electrode 500 and the piezoelectric body 400, and etching is performed to form the second electrode 500 and the piezoelectric body 400. Note that lead zirconate titanate is used as the material of the piezoelectric body 400, and the thickness of the piezoelectric body 400 is 2 μm. A titanium-tungsten alloy is used as the material of the second electrode 500, and the thickness of the second electrode 500 is 120 nm.

[0087] As a result, a piezoelectric element 140 formed of a first electrode 300, a piezoelectric body 400, and a second electrode 500 is formed (see Figure 2B ). The portion of the piezoelectric body 400 (and the second electrode 500) covering the inclined surface of the first electrode 300 is inclined with respect to the substrate 100E. The patterning boundary line for the piezoelectric body 400 may be located on one of the inclined surfaces of the first electrode 300 or may be located on the insulating film 200. The side surface of the piezoelectric body 400 formed by etching may be perpendicular to the substrate 100E (the upper surface thereof) as shown in Figure 7C , or may be inclined with respect to the substrate 100E.

[0088] Next, as shown in Figure 7D , an insulating film 600 having a thickness of 100 nm is formed on the upper sides of the first electrode 300, the piezoelectric body 400, and the second electrode 500 using CVD. In addition, a resist pattern is lithographically formed to create a desired pattern for the upper through-hole 601 and the lower through-hole 602, and etching is performed to form the upper through-hole 601 and the lower through-hole 602 in the insulating film 600. Note that tetraethyl orthosilicate (TEOS) is used as the material for the insulating film 600. In addition, considering that a part of the underlying insulating film 200 is removed when forming the first electrode 300 using dry etching, the film thickness and film formation conditions of the insulating film 600 can be determined.

[0089] Next, as shown in Figure 8A , an upper wiring 801 and a lower wiring 802 are formed to cover the insulating film 600. In the formation of the upper wiring 801 and the lower wiring 802, a film serving as a raw material for the upper wiring 801 and the lower wiring 802 is formed on the upper surface of the insulating film 600 by sputtering. After film formation, a resist pattern is lithographically formed to create a desired pattern for the upper wiring 801 and the lower wiring 802, and etching is performed to form the upper wiring 801 and the lower wiring 802. As a result, the upper wiring 801 is electrically connected to the second electrode 500 through the upper through-hole 601 in the insulating film 600, and the lower wiring 802 is electrically connected to the first electrode 300 through the lower through-hole 602 in the insulating film 600.

[0090] Next, as shown in Figure 8B , a silicon nitride film having a thickness of 50 nm is formed on the upper sides of the upper wiring 801 and the lower wiring 802 using CVD to form a passivation film 900 having high insulation. In the formation of the passivation film 900, a resist pattern is lithographically formed to create a desired pattern, and then etching is performed to form an opening portion only at the central portion of the portion of the passivation film 900 overlapping with the second electrode 500. This makes it possible to increase the moisture resistance and improve the reliability of the upper wiring 801 and the lower wiring 802.

[0091] Thus, the actuator 700 of Example 1 is completed. Although not shown, next, the substrate 100E is processed to form a recess 110 for retaining ink, and thus the second flow channel substrate 100 is produced. Next, the first flow channel substrate 20 is joined to the lower surface side of the second flow channel substrate 100, and the third flow channel substrate 40 is joined to the upper surface side of the second flow channel substrate 100. Thus, a liquid ejection head including a plurality of actuators 700 is produced. Then, as in the conventional liquid ejection head manufacturing method, electrical components, support members, etc. are mounted and assembled to the liquid ejection head. Thus, the liquid ejection head unit is completed.

[0092] According to Example 1, a piezoelectric body 400 having a large effective area and an actuator 700 with high reliability can be provided.

[0093] <Example 2>

[0094] Example 2 is an example corresponding to the above-described embodiment. The configuration and manufacturing method of the actuator 700 in which spin coating is used to form the piezoelectric body 400 are described in Example 2. Note that the components in Example 2 are configured to be similar to the components in the above-described embodiment, and thus the same reference numerals as those used for the components in the above-described embodiment are used for description.

[0095] Figures 9A to 10B is a step-by-step cross-sectional view illustrating the manufacturing process in Example 2. As Figure 9A shown, a substrate 100E made of single crystal silicon is prepared as a raw material for the second flow channel substrate 100. As in Example 1, an insulating film 200 is formed on the upper surface of the substrate 100E.

[0096] Next, as Figure 9B shown, as in Example 1, a first electrode 300 is formed to cover the insulating film 200. In the formation of the first electrode 300, as in Example 1, a plurality of inclined surfaces (e.g., two inclined surfaces 301, 302) are formed at the end of the upper surface of the first electrode 300.

[0097] Next, as Figure 9CAs shown, the piezoelectric body 400 is formed to cover the first electrode 300, and the second electrode 500 is formed to cover the piezoelectric body 400. The second electrode 500 and the piezoelectric body 400 are formed as follows. A film as the raw material of the piezoelectric body 400 is formed on the upper surface of the first electrode 300 by spin coating and baked at 800 °C to obtain a desired crystal orientation. Additionally, a second film as the raw material of the second electrode 500 is formed on the upper surface of the film as the raw material of the piezoelectric body 400 by sputtering. After film formation, a resist pattern is lithographically formed to fabricate the desired patterns of the second electrode 500 and the piezoelectric body 400, and etching is performed to form the second electrode 500 and the piezoelectric body 400. Note that lead zirconate titanate is used as the material of the piezoelectric body 400, and the thickness of the piezoelectric body 400 is 2 μm. Titanium tungsten alloy is used as the material of the second electrode 500, and the thickness of the second electrode 500 is 120 nm.

[0098] As a result, a piezoelectric element 140 formed of the first electrode 300, the piezoelectric body 400, and the second electrode 500 is formed (see Figure 2B ). Compared with the case where the piezoelectric body 400 is formed by sputtering, the portion of the piezoelectric body 400 (and the second electrode 500) covering the inclined surface of the first electrode 300 is inclined more gently with respect to the substrate 100E. The boundary line for patterning the piezoelectric body 400 may be located on one of the inclined surfaces of the first electrode 300 or may be located on the insulating film 200. The side surface of the piezoelectric body 400 formed by etching may be perpendicular to the substrate 100E (the upper surface thereof) as shown in Figure 9C , or may be inclined with respect to the substrate 100E.

[0099] Next, as shown in Figure 9D , an insulating film 600 having a thickness of 100 nm is formed on the upper sides of the first electrode 300, the piezoelectric body 400, and the second electrode 500, like in Example 1. In the formation of the insulating film 600, an upper through hole 601 and a lower through hole 602 are formed in the insulating film 600, like in Example 1.

[0100] Next, as shown in Figure 10A , upper wirings 801 and lower wirings 802 are formed to cover the insulating film 600, like in Example 1. As a result, the upper wiring 801 is electrically connected to the second electrode 500 through the upper through hole 601 in the insulating film 600, and the lower wiring 802 is electrically connected to the first electrode 300 through the lower through hole 602 in the insulating film 600.

[0101] Next, as shown in Figure 10BAs shown, like in Example 1, a passivation film 900 with high insulation is formed on the upper side of the upper wiring 801 and the lower wiring 802. In the formation of the passivation film 900, like in Example 1, an opening is formed only at the central portion of the portion of the passivation film 900 that overlaps with the second electrode 500. This enables an increase in moisture resistance and an improvement in the reliability of the upper wiring 801 and the lower wiring 802.

[0102] Thus, the actuator 700 of Example 2 is completed. Although not shown, next, the substrate 100E is processed to form a recess 110 for retaining ink, and thus the second flow channel substrate 100 is produced. Next, the first flow channel substrate 20 is joined to the lower surface side of the second flow channel substrate 100, and the third flow channel substrate 40 is joined to the upper surface side of the second flow channel substrate 100. Thus, a liquid ejection head including a plurality of actuators 700 is produced. Then, like in the conventional liquid ejection head manufacturing method, electrical components, support members, etc. are installed and assembled on the liquid ejection head. Thus, the liquid ejection head unit is completed.

[0103] According to Example 2, a piezoelectric body 400 with a large effective area and an actuator 700 with high reliability can be provided.

[0104] Although the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the present disclosure is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to encompass all such modifications as well as equivalent structures and functions.

Claims

1. An actuator, comprising: A first electrode, a piezoelectric body, and a second electrode are sequentially disposed on a surface of a substrate, and an insulating film covering at least the side surface of the piezoelectric body, wherein The actuator has a plurality of inclined surfaces inclined with respect to the substrate at an end of a surface of the first electrode opposing the substrate, and An angle between the substrate and a first inclined surface farthest from the substrate among the plurality of inclined surfaces is smaller than an angle between the substrate and any other inclined surface among the inclined surfaces.

2. The actuator according to claim 1, wherein The first electrode comprises platinum.

3. The actuator according to claim 1, wherein The material of the piezoelectric body is lead zirconate titanate.

4. The actuator according to claim 1, wherein An angle between the substrate and each of the inclined surfaces decreases with a distance from the substrate.

5. The actuator according to claim 1, wherein An angle between the substrate and the first inclined surface is greater than or equal to 12 degrees and less than or equal to 22 degrees.

6. The actuator according to claim 1, wherein An angle between the substrate and a second inclined surface, among the plurality of inclined surfaces, that is second farthest from the substrate is 27 degrees or more and 37 degrees or less.

7. The actuator according to claim 1, wherein The plurality of inclined surfaces include three inclined surfaces, and An angle between the substrate and a third inclined surface, which is thirdly farthest from the substrate among the three inclined surfaces, is greater than or equal to 67 degrees and less than or equal to 77 degrees.

8. The actuator according to claim 1, wherein The plurality of inclined surfaces include three inclined surfaces, An angle between the substrate and a second inclined surface of the three inclined surfaces that is second farthest from the substrate is greater than an angle between the substrate and the first inclined surface, and An angle between the substrate and a third inclined surface, which is thirdly farthest from the substrate among the three inclined surfaces, is greater than an angle between the substrate and the second inclined surface.

9. The actuator according to claim 1, wherein Each of the plurality of inclined surfaces is formed by a curved surface, and An angle between a tangent plane of the substrate and the curved surface decreases as a tangent point where the tangent plane intersects the curved surface moves away from the substrate.

10. The actuator according to claim 1, wherein The piezoelectric body covers at least a portion of the plurality of inclined surfaces.

11. The actuator according to claim 10, wherein A portion of the piezoelectric body covering at least a portion of the plurality of inclined surfaces is inclined relative to the substrate.

12. The actuator according to claim 1, wherein The insulating film covers at least a portion of the plurality of inclined surfaces of the first electrode.

13. The actuator according to claim 1, wherein The insulating film covers a surface of the second electrode that is opposed to the piezoelectric body.

14. The actuator according to claim 13, wherein The insulating film has a through hole for connecting the second electrode and a wiring to be electrically connected to the second electrode.

15. The actuator according to claim 1, wherein A side surface of the first electrode is formed by the plurality of inclined surfaces. 16 . A liquid ejecting head that ejects liquid by driving the actuator according to claim 1 .

17. A method for manufacturing an actuator, the method comprising: forming a film on a surface of a substrate; forming a first electrode by dry etching the film; forming a piezoelectric body on the first electrode; forming a second electrode on the piezoelectric body; as well as An insulating film is formed to cover at least the side surface of the piezoelectric body, wherein In forming the first electrode, a plurality of inclined surfaces inclined with respect to the substrate are formed at an end of a surface of the first electrode opposing the substrate, and An angle between the substrate and a first inclined surface farthest from the substrate among the plurality of inclined surfaces is smaller than an angle between the substrate and any other inclined surface among the inclined surfaces.

Images