Liquid ejection head and piezoelectric actuator

Abstract

The invention relates to a liquid ejection head and a piezoelectric actuator. Provided is a liquid ejection head capable of suppressing peeling from an end portion of a piezoelectric layer and an electrode layer and peeling from a wiring above a contact portion while ensuring a required amount of displacement of a piezoelectric element. To this end, a protective film is formed so as to cover a partial region including an end portion of a first electrode below the piezoelectric film, a partial region including an end portion of a second electrode above the piezoelectric film, and a second layer wiring above a contact portion across a center of the piezoelectric film.

Description

Technical Field

[0001] The present disclosure relates to a liquid ejection head having a piezoelectric element. Background Art

[0002] With the development of MEMS (Micro Electro Mechanical System) technology, thin film piezoelectric elements based on semiconductor processes have recently been proposed.

[0003] Japanese Patent Laid-Open No. 2021-024141 discloses a configuration in which a peripheral portion of an upper electrode on its upper surface, the entire side surfaces of the upper electrode and the piezoelectric film, and a peripheral portion of a lower electrode are covered with an insulating film made of, for example, silicon dioxide (SiO2), while a contact portion between the lower electrode and the wiring is not covered with the insulating film.

[0004] Japanese Patent Laid-Open No. 2016-058716 also discloses a configuration in which a peripheral portion of an upper electrode on its upper surface, the entire side surfaces of the upper electrode and the piezoelectric film, a lower electrode, and a contact portion are covered with a protective film.

[0005] However, in the configuration disclosed in Japanese Patent Laid-Open No. 2021-024141, peeling of electrode layers and wirings or peeling from the ends of the piezoelectric film may occur in contact portions not covered by the insulating film, resulting in the possibility that sufficient robustness may not be obtained in the piezoelectric element.

[0006] Moreover, in the configuration disclosed in Japanese Patent Laid-Open No. 2016-058716, the electrode layer of the piezoelectric body is provided beyond the range of the pressure chamber, and a plurality of protective films are laminated beyond the range of the pressure chamber. In such a configuration in which a plurality of protective films are laminated beyond the range of the pressure chamber as in Japanese Patent Laid-Open No. 2016-058716, the film thickness increases from the outside to the inside of the pressure chamber to limit the end of the piezoelectric element. This brings about a problem that it is difficult to obtain the necessary displacement of the piezoelectric element. Summary of the invention

[0007] Therefore, the present disclosure provides a liquid ejection head including a piezoelectric element having high robustness while ensuring a required displacement amount.

[0008] Therefore, according to the present disclosure, a liquid ejection head includes: a laminate of the following items: a substrate having a pressure chamber formed therein, the pressure chamber being connected to an ejection port for ejecting liquid; a vibration plate, the vibration plate vibrating to generate pressure in the liquid in the pressure chamber; a piezoelectric film, the piezoelectric film vibrating the vibration plate by applying a voltage; a first electrode, the first electrode being provided on one surface of the piezoelectric film between the piezoelectric film and the vibration plate; and a second electrode, the second electrode being provided on the other surface of the piezoelectric film; a first wiring, the first wiring being connected to the first electrode through a first contact portion; a second wiring, the second wiring being connected to the second electrode through a second contact portion; and a protective film, the protective film having at least a first portion and a second portion, the first portion covering a partial area including an end portion of the first electrode, the first contact portion, and the first wiring, and the second portion covering a partial area including an end portion of the second electrode, the second contact portion, and the second wiring, on one end side and the other end side of the piezoelectric film in the longitudinal direction of the piezoelectric film within a range overlapping with the pressure chamber when viewed from a direction perpendicular to the substrate.

[0009] Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A and Figure 1B is a diagram showing an element substrate;

[0011] Figure 2 This is a top view of the channel substrate in the single-chip element substrate as seen from the piezoelectric film side;

[0012] Figure 3 It is along Figure 2 A schematic cross-sectional view taken along line III-III in FIG.

[0013] Figure 4 It is shown Figure 2 Top view near III-III in FIG.

[0014] Figure 5 It is along Figure 4 A cross-sectional view taken along line VV in FIG.

[0015] FIG. 6A to FIG. 6E is a diagram sequentially showing a manufacturing process of a piezoelectric element;

[0016] Figure 7 is a diagram showing an upper surface of a piezoelectric element;

[0017] Fig. 8A and Figure 8B is a cross-sectional view of a piezoelectric element;

[0018] Fig. 9 is a diagram showing an upper surface of a piezoelectric element;

[0019] Fig.10 It is along Fig. 9 A cross-sectional view taken along line XX in FIG.

[0020] Fig.11 is a diagram showing an upper surface of a piezoelectric element;

[0021] Fig.12 is a cross-sectional view of a piezoelectric element;

[0022] Fig.13 is a diagram showing an upper surface of a piezoelectric element;

[0023] Fig.14 It is along Fig.13 A cross-sectional view taken along line XIV-XIV in FIG. 1 ; and

[0024] Fig.15 It is along Fig.13 A cross-sectional view taken along line XV-XV in FIG.

[0025] Fig.16 is a diagram showing a liquid ejection head. DETAILED DESCRIPTION

[0026] (First embodiment)

[0027] A first embodiment of the present disclosure will be described below with reference to the drawings.

[0028] Figure 1A and Figure 1B 1 is a diagram showing an element substrate 112 formed by combining a first channel substrate 105, a second channel substrate 106, and a third channel substrate 107. If a general MEMS process is adopted, a silicon substrate is generally used for three types of substrates, namely, the first channel substrate 105, the second channel substrate 106, and the third channel substrate 107. Other members such as a mold may be used in combination with the silicon substrate. In the following figures, the X direction indicates the direction in which a nozzle array 200 to be described later is arranged, the Y direction indicates the direction in which an ejection port 101 to be described later is arranged, and the -Z direction indicates the direction in which ink is ejected.

[0029] A plurality of channel blocks 100 are formed in the element substrate 112 . Figure 1A It is a perspective view seen from the surface of the ejection outlet 101 including a plurality of channel blocks 100 . Figure 1B It is along Figure 1A The cross-sectional view taken along the line IB-IB in FIG. Figure 1A and Figure 1B As shown in FIG. 1 , the channel blocks 100 each include an ejection port 101, and a pressure chamber 102 and a supply channel 103 connected to each of the ejection ports 101. Each of the supply channels connected to a common liquid chamber 104 supplies ink to the pressure chamber 102. Figure 1B The arrows shown in indicate the flow of ink.

[0030] like Figure 1B As shown in FIG. 1 , the element substrate 112 is formed by laminating a first channel substrate 105 including an ejection port 101, a second channel substrate 106 having a piezoelectric element 108 and a pressure chamber 102, and a third channel substrate 107 including an ink supply channel isolating the piezoelectric element 108 from the ink in the Z direction. A supply channel 103, a pressure chamber 102, and an ejection port 101 are formed corresponding to each piezoelectric element 108. The pressure chamber 102 is separated from the adjacent pressure chamber 102 in the Y direction by a partition, and each pressure chamber is not directly affected by the adjacent piezoelectric element 108.

[0031] Here, the piezoelectric element 108 is formed by laminating a vibration plate 109, a piezoelectric film 110, a first electrode 301, a second electrode 302, a first insulating film 303, a second insulating film 604, and a protective film 304 (which will be referred to later). Figure 3 Description). The vibration plate 109 generates pressure on the liquid in the pressure chamber through the action of the piezoelectric film 110. That is, the ink contained in the pressure chamber 102 forms a meniscus at the ejection port 101 in a stable state. When a voltage is applied to the piezoelectric element 108 according to the ejection signal, the piezoelectric element 108 deforms tortuously to expand or contract the volume of the pressure chamber 102. By combining the expansion and contraction operations, ink droplets 113 are generated from the meniscus and ejected to the external air side (-Z direction). Pressure is thus applied to the liquid in the pressure chamber through the action of the piezoelectric element 108 and the vibration plate 109. The ink in the pressure chamber 102 consumed by the ejection operation is supplied from the common liquid chamber 104 through capillary force, and a meniscus is reformed at the ejection port 101. In the present embodiment, the combination of the ejection port 101, the piezoelectric element 108 and the pressure chamber 102 is referred to as an ejection element.

[0032] The vibration plate 109 can be made of silicon nitride film, silicon, metal, heat-resistant glass, etc., depending on the required mechanical properties and reliability. The piezoelectric film 110 can be formed by vacuum sputtering, sol-gel solution, chemical vapor deposition (CVD), etc. Many piezoelectric films 110 are calcined after formation, and the calcination is performed at a maximum of 600 to 800° C. in an oxygen atmosphere, for example, by lamp annealing, etc. The film can be formed directly on the vibration plate 109 and calcined integrally, or it can be formed on a separate substrate and calcined before being peeled off and transferred to the vibration plate 109 side, or it can be formed on a separate substrate and peeled off and transferred to the vibration plate 109 side before being calcined integrally.

[0033] Reference again Figure 3 , a first electrode 301 is formed on one surface of the piezoelectric film 110, and a second electrode 302 is formed on the other surface of the piezoelectric film 110. Regarding the first electrode 301 and the second electrode 302, in the case of undergoing a calcination process, a noble metal with high heat resistance, such as Pt and Ir, is selected. On the other hand, in the case where the calcination process can be separated, an Au-based alloy, an Al-based alloy, etc. can also be selected. As the piezoelectric film 110, a PZT-based ceramic is widely known. From the viewpoint of controllability, it is desirable to use a material with high linearity in voltage response displacement and drive within a voltage range with high linearity. However, in reality, saturation characteristics, hysteresis characteristics, nonlinearity of electrostriction, etc. affect the displacement characteristics.

[0034] In the present embodiment, each ejection element (hereinafter also referred to as a nozzle) can be arranged in the Y direction at a density of 150npi (nozzles per inch), or can be arranged at a higher density of, for example, 300npi or 600npi. The viscosity of the ink used is about several to more than ten cP, and the drive waveform is adjusted so that the minimum ink ejection amount from each ejection port 101 is a few pL. When the nozzle density is 300npi, the width of the liquid chamber is narrower than the width of the liquid chamber when the nozzle density is 150npi. Therefore, the vibration plate 109 is designed to be thin to ensure the necessary displacement. In addition, each piezoelectric element 108 is often designed to have a driving frequency of tens of kHz. Such a driving frequency is set from the time required for each ejection element to actually eject ink and then refill new ink for the next ejection operation after a voltage is applied to the piezoelectric element 108.

[0035] like Fig.16As shown in , the liquid ejection head 1000 is often configured as a head by arranging a plurality of element substrates 112, each of which is a unit (a chip) including a plurality of ejection elements arranged therein. Each element substrate 112 is generally connected to a flexible printed circuit board and is also connected to an electrical wiring board. A power supply terminal for supplying power to the element substrate 112 and a signal input terminal for receiving an ejection signal are arranged on the electrical wiring board.

[0036] On the other hand, the ink supply unit may have a circulation channel formed therein, which supplies ink containing a color material supplied from an ink tank to each element substrate 112 and collects ink that is not consumed in printing.

[0037] With the above configuration, each ejection element arranged on the element substrate 112 ejects the ink supplied by the ink supply unit from the ejection port 101 to the outside air side (-Z side) using the power supplied from the power supply terminal based on the print data input from the signal input terminal. Note that the dimensional value of each part described above is merely an example and may be appropriately changed depending on the specification.

[0038] Figure 2 1 is a top view of the second channel substrate 106 of the element substrate 112 as viewed from the side of the piezoelectric film 110. The piezoelectric film 110 (see Figure 3 ) and the pressure chamber 102 are formed in the second channel substrate 106. For formation, a MEMS process using a silicon substrate is preferably adopted. On the element substrate 112, a plurality of nozzle arrays 200 are arranged along the ±X direction, and the nozzles are arranged along the ±Y direction at a specified density and a specified nozzle length. At least two nozzle arrays 200 are arranged, and up to eight arrays, etc. can be used. The length of the nozzle array is generally selected from a range of about 0.5 inches to up to about 1.5 inches. A liquid ejection head is configured by combining a plurality of such element substrates 112.

[0039] exist Figure 2 On the second channel substrate 106 constituting the element substrate 112 shown in FIG. 1 , wiring 201 is arranged to supply power to the first electrode 301 of each piezoelectric film 110 (see Figure 3 ) and the second electrode 302 (see later described Figure 3 ) supplies a corresponding electrical signal. The second channel substrate 106 is provided with a pad portion 202 for electrical connection with an external electrical substrate. The shape of the pad portion 202 is appropriately designed according to the mounting method. The pad portion 202 may be as follows: Figure 2As shown in the figure, it is arranged only on one side of the second channel substrate 106, or it can be arranged separately on both sides. The advantage of arranging the pad portion 202 only on one side of the second channel substrate 106 is to reduce the number of mounting components and steps. Using a flexible cable with IC installed as a mounting component enhances the effect of reducing material costs. However, in the case where the wiring is concentrated on one side, the wiring density in the wiring routing area increases, resulting in stricter layout constraints requiring optimized wiring layout. In addition, by making the wiring into a laminated structure, the wiring can be distributed to each layer, and the plane layout space constraints can be avoided.

[0040] As the nozzle density increases, the liquid chamber width becomes narrower. Therefore, in order for the piezoelectric element 108 to eject a predetermined amount of ink, a large displacement is required, and the curvature of the vibration plate needs to be increased. The large curvature during deformation increases the stress at the end of the piezoelectric element 108, resulting in the possibility that peeling will occur. Therefore, there is a method of forming a protective film to prevent peeling, but if the protective film is wide or thick, there is a possibility that peeling will occur due to stress concentration caused by residual stress in the film, or the possibility of hindering the displacement of the piezoelectric element 108. Therefore, in the present embodiment, a portion of the upper surface and the side surface portion of the piezoelectric element 108 are covered with a protective film.

[0041] With reference to the drawings, a description will be given below of a piezoelectric element 108 as a microstructure formed using a semiconductor process according to the present embodiment. Note that the present embodiment will be described focusing on the configuration and manufacturing method of the piezoelectric element 108.

[0042] Note that the components described in the following embodiments are merely examples and are not intended to limit the scope of the present disclosure to only these. The present disclosure will be described using an example employing a liquid ejection method, but is not limited thereto, and various modifications and changes may be made within the scope of the gist.

[0043] In this embodiment, the respective ejection elements (nozzles) (ie, the piezoelectric elements 108) are arranged at a density of 300 npi in the Y direction. Figure 4 , the size of the piezoelectric element 108 is 700 μm (length) in the X direction and 50 μm (width) in the Y direction. The size of the pressure chamber 102 is 750 μm (length) in the X direction, 55 μm (width) in the Y direction, and 100 μm (height) in the Z direction. Since the width of the liquid chamber is narrower than that in the case of 150 npi, the required displacement amount is ensured by designing the vibration plate 109 to be thin. Referring again to Figure 2 , the diameter of the ejection port 101 is 20 μm. The nozzle diameter, which is the diameter of the ejection port 101, is a value adjusted according to the specification of the ejected droplets, and can be selected from a range of about 10 to 30 μm.

[0044] Figure 3 It is along Figure 2 A schematic cross-sectional view taken along line III-III in FIG. Figure 3 The piezoelectric element 108 is described. The diaphragm-shaped piezoelectric element 108 is formed at a position corresponding to the pressure chamber 102. The piezoelectric element 108 is formed by laminating the vibration plate 109, the first electrode 301, the piezoelectric film 110, the second electrode 302, the first insulating film 303, the second insulating film 604, and the protective film 304 in this order from the pressure chamber 102 side. The protective film 304 has an opening in the region 203 above the piezoelectric film 110.

[0045] In the case of using an oxide-based ceramic as the piezoelectric film 110, it may be preferable to form a reduction inhibiting film on the piezoelectric film 110 before forming an insulating film. Although SiO-based films are often used as general insulating films in CVD devices, oxides on the film-forming side are easily reduced during gas reactions. Once reduced, the interface of the Schottky junction between the piezoelectric film 110 and the second electrode 302 collapses, causing deterioration in the leakage characteristics of the piezoelectric film 110, which can lead to degradation of long-term reliability. In order to prevent this, it is effective to form an oxide film (not shown) such as Al2O3 as one of the reduction inhibiting films using an ALD device.

[0046] Then, a SiO-based or SiN-based film is formed as a first insulating film 303 for wiring using CVD8 or TEOS (tetraethoxysilane). Thereafter, an electrical contact portion with the piezoelectric film 110 is formed in the first insulating film 303. In the next step of forming wiring, an Al-based alloy film is often mainly used, but other alloy films may also be used. Then, a SiO-based or SiN-based film is formed as a sealing film (not shown) using CVD or TEOS. Finally, from Figure 2 The sealing film is removed from the connection area of ​​the pad portion 202 shown in FIG.

[0047] The piezoelectric element 108 in the liquid ejection head according to the present embodiment is used for zigzag deformation. Therefore, the increase in the thickness of the film above the piezoelectric film 110 makes it less likely that the zigzag deformation will occur, resulting in the possibility that the desired effect will not be achieved. In order to efficiently achieve zigzag deformation, it is preferred that the neutral plane defined by material mechanics is positioned near the interface between the piezoelectric film 110 and the vibration plate 109, preferably slightly toward the vibration plate 109. Since the first insulating film 303 is additionally formed above the piezoelectric film 110, the neutral plane is offset to the inside of the piezoelectric film 110, making it difficult to bend. In the case where the protective film 304 is formed on the surface side of the piezoelectric film 110, such bending is also suppressed. It is preferred to form the necessary film thickness in the part (such as the electrical contact part) requiring insulation and sealing functions, and partially remove or thin the film above the piezoelectric film 110 so that the minimum film thickness required for sealing is retained. This makes it possible to improve the displacement efficiency of zigzag deformation.

[0048] The region 203 on the piezoelectric film 110 where the inorganic film is thinned or removed is achieved by masking with a photoresist using a photolithography process and a removal step using semiconductor plasma etching.

[0049] Figure 4 It is shown Figure 2 In this embodiment, the protective film 304 is formed above the end of the first electrode 301 and the piezoelectric film 110 (see Figure 3 ) on the end of the second electrode 302 above the contact portion 706, and on the second layer wiring 704 above the contact portion 706. Figure 4 As shown in , when viewed from a direction perpendicular to the substrate, the protective film 304 continuously covers the area overlapping the periphery of the piezoelectric film 110. The protective film 304 has an opening in the area 203 which is a part of the area of ​​the second electrode 302 on the piezoelectric film 110. The area of ​​the pressure chamber 102 without the protective film 304 is wider than the area with the protective film 304.

[0050] Inside the pressure chamber 102 area, the protective film 304 protrudes from the end of the second electrode 302 on the piezoelectric film 110. Lx_in is the protrusion amount in the X direction and Ly_in is the protrusion amount in the Y direction. The protective film 304 also protrudes from the end of the first electrode 301. Lx_out is the protrusion amount in the X direction and Ly_out is the protrusion amount in the Y direction. Wc1 is the width of the contact portion 703 in the Y direction (width direction), Wa is the width of the second electrode 302 in the Y direction, We is the width of the first electrode 301 in the Y direction, and Wc2 is the width of the contact portion 701 in the Y direction.

[0051] Figure 5 It is along Figure 4104 is a cross-sectional view taken along line VV in FIG. The diaphragm-shaped piezoelectric element 108 is formed at a position corresponding to the pressure chamber 102 (on the surface of the vibration plate 109 opposite to the pressure chamber 102). The piezoelectric element 108 is formed by laminating the vibration plate 109, the first electrode 301, the piezoelectric film 110, the second electrode 302, the first insulating film 303, the first layer wiring 702 and the relay portion 705, the second insulating film 604, the second layer wiring 704, and the protective film 304 in this order from the pressure chamber 102 side. The first insulating film 303 insulates the relay portion 705 from the first electrode 301 in the region other than the contact portion 703. The second insulating film 604 insulates the relay portion 705 from the second layer wiring 704 in the region other than the contact portion 706.

[0052] The relay portion 705 bridges the first electrode 301 and the second layer wiring 704. The second electrode 302 and the first layer wiring 702 are electrically connected at the contact portion 701. The contact portion 703 electrically connects the first electrode 301 and the relay portion 705. The first layer wiring 702 and the second layer wiring 704 are thereby electrically connected through the piezoelectric film 110.

[0053] FIG. 6A to FIG. 6E 1 is a diagram sequentially showing the steps of manufacturing the piezoelectric element 108. The steps of manufacturing the piezoelectric element 108 will be described below. First, Fig. 6A As shown in , an SOI (silicon on insulator) substrate is prepared as a vibration plate 109, which has a buried oxide (BOX) layer 601 with a thickness of 0.5 to 1.0 μm and a device layer 602 with a thickness of 0.75 to 1.25 μm. Then, a 250 nm thick oxide film 603 is formed on the surface of the SOI substrate by thermal oxidation of the device layer. Then, a Pt / TiO2 / Ti laminated film is formed thereon as the first electrode 301 of the piezoelectric element 108. A PZT film with a thickness of 1.5 to 2.5 μm is formed as the piezoelectric film 110 by a sol-gel method, and a Ti-based alloy film is formed as the second electrode 302.

[0054] Next, if Figure 6B As shown in , the second electrode 302 and the PZT film are patterned by photolithography (resist pattern 901) and etched. This forms a pattern of the piezoelectric film 110 and the second electrode 302 at a position corresponding to the pressure chamber 102 formed in the channel forming step. The size of the piezoelectric film 110 is 45 to 50 μm in the width direction and 500 to 650 μm in the longitudinal direction. Then, the photoresist is removed before proceeding to the next step.

[0055] like Figure 6CAs shown in , the pattern of the first electrode 301 is formed by photolithography (resist pattern 902) so as to have a width of several μm to 10 μm from the PZT region and then etching. Then, the photoresist is removed before proceeding to the next step.

[0056] like Fig.6D As shown in FIG, an Al2O3 film having a thickness of about 20 nm is formed as a barrier film (not shown) to prevent damage to the PZT film during the process. Then, a TEOS oxide film having a thickness of 400 nm is formed as a first insulating film 303 to prevent leakage between elements. Next, a Figure 4 and Figure 5 The contact portion 701 (see FIG. 1 ) for electrically connecting the second electrode 302 of the piezoelectric film 110 to the wiring is formed. Figure 4 and Figure 5 ), and then a contact portion 703 for electrically connecting the first electrode 301 of the piezoelectric film 110 to the wiring is formed (see Figure 4 and Figure 5 ). Thereafter, an AlCu alloy film is formed, and a first-layer wiring 702 for bridging is simultaneously formed through a series of semiconductor processes (see Figure 4 and Figure 5 ) and second layer wiring 704 (see Figure 4 and Figure 5 ) and the relay portion 705 of the first electrode 301 (see Figure 4 and Figure 5 ). Next, a TEOS oxide film with a thickness of 400 nm is formed as a second insulating film 604 to prevent leakage between wirings, and a contact portion 706 is formed on a region of a relay portion 705 to be electrically connected to the first electrode 301 (see Figure 4 and Figure 5 ).

[0057] Here, since the electrical pad portion 202 (see Figure 2 ) is to be located above the second insulating film 604 (below the protective film 304), so the wiring 702 located in the first layer (lower layer) needs to be connected to the second layer (upper layer). To this end, an opening (not shown) for pad connection is formed in the second insulating film 604 near the pad portion 202. Thereafter, an AlCu alloy film constituting the second layer wiring is formed, and the wiring 704 located in the second layer is formed through a series of semiconductor processes. Then, the second layer wiring 704 is formed, and the second layer wiring 704 is electrically connected to the first electrode 301 through the relay portion 705. At the same time, the first layer wiring 702 electrically connected to the second electrode 302 is electrically connected to the pad portion 202. The wiring located in the second layer is thereby formed.

[0058] The wiring 201 corresponding to the first electrode 301 and the second electrode 302 (see Figure 2 ) is thereby electrically connected to the pad portion 202. A configuration having multi-layer wiring is thereby achieved. A SiN-based protective film 304 having a thickness of approximately 200 nm is formed on the uppermost surface layer (surface) (protective film formation). The protective film 304 is made of an inorganic material and may be a film containing at least SiO, or any one of Al, Zr, and Hf.

[0059] Furthermore, the film thickness×Young's modulus E of the protective film 304 is 10 to 80% of the film thickness×Young's modulus Ep of the piezoelectric film 110, where Young's modulus E is the Young's modulus of each material of the protective film 304, and Young's modulus Ep is the Young's modulus of the piezoelectric film 110. It is preferable that the residual stress of the protective film 304 is within ±100 MPa (weak compression to weak tension).

[0060] like Fig. 6E As shown in , the second insulating film 604 and the protective film 304 above the piezoelectric film 110 are removed, and the protective film 304 around the piezoelectric element 108 is removed to form a region 203 from which the protective film 304 has been removed. Finally, the upper inorganic film of the pad portion 202 is removed to expose the metal surface. Through these steps, the piezoelectric element 108 is completed.

[0061] Here, in Figure 4 , inside the pressure chamber 102, the protective film 304 intrudes into the second electrode 302 from the end of the second electrode 302 above the piezoelectric film 110. It is preferable that the protrusion amounts Lx_in and Ly_in in the X and Y directions are both 5 to 10 μm. More specifically, the protective film 304 covers until it intrudes inward from the end of the second electrode 302 by a portion greater than or equal to 5 μm and less than or equal to 10 μm. The protective film 304 also protrudes from the end of the first electrode 301. It is preferable that the protrusion amounts Lx_out and Ly_out in the X and Y directions are both greater than or equal to 5 μm and less than or equal to 10 μm.

[0062] It is also preferable that the width Wc1 of the contact portion 703 is greater than or equal to 70% and less than or equal to 100% of the width We of the first electrode 301 under the piezoelectric film 110. In other words, it is preferable that the following relationship is satisfied.

[0063] We×0.7≤Wc1≤We

[0064] It is also preferable that the width Wc2 of the contact portion 701 is 70% or more and 100% or less of the width Wa of the second electrode 302. In other words, it is desirable that the following relationship is satisfied.

[0065] Wa×0.7≤Wc2≤Wa

[0066] The preferred conditions described above are conditions for preventing peeling as a result of considering how to suppress peeling while maintaining displacement that satisfies the specifications of the ejected droplets with process tolerance.

[0067] Thus, a protective film 304 is formed that covers a portion of the region including the end of the first electrode 301 below the piezoelectric film 110, a portion of the region including the end of the second electrode 302 above the piezoelectric film 110, and the second layer wiring 704 above the contact portion 706 across the boundary end of the piezoelectric film 110. This makes it possible to alleviate the residual stress in the protective film, thereby making it less likely that peeling will occur due to stress concentration. This makes it possible to realize a piezoelectric element 108 with high robustness while ensuring the necessary displacement amount of the piezoelectric element 108.

[0068] (Second embodiment)

[0069] A second embodiment of the present disclosure will be described below with reference to the drawings. Note that the basic configuration of this embodiment is the same as that of the first embodiment, so a characteristic configuration will be described below.

[0070] Figure 7 is a diagram showing the upper surface of the piezoelectric element 108 according to the present embodiment. Fig. 8A It is along Figure 7 A cross-sectional view taken along line VIIIA-VIIIA in FIG. Figure 8B It is along Figure 7 VIIIB-VIIIB in the cross-sectional view. In the piezoelectric element 108 of the present embodiment, a protective film 304 is formed on both ends of the first electrode 301 in the X direction below the piezoelectric film 110, on both ends of the second electrode 302 in the X direction above the piezoelectric film 110, and on the second layer wiring 704 above the contact portion 706. More specifically, a quadrilateral protective film 304 is formed so as to partially cover both ends of the first electrode 301 in the Y direction and both ends of the second electrode 302 in the Y direction. In the present embodiment, as Figure 7 As shown in FIG. 1 , the protective film 304 is provided at five locations in both end portions of the first electrode 301 and the second electrode 302 in the Y direction.

[0071] As described above, when viewed from a direction perpendicular to the substrate, the boundary of the piezoelectric film 110 between the two ends is partially covered by a plurality of protective films 304. As a result, when the piezoelectric element 108 is deformed, deflection is less likely to occur in the protective film 304 at the ends other than the corners of the piezoelectric film 110 and the electrode, making it possible to prevent peeling due to deflection in the protective film 304.

[0072] (Third Embodiment)

[0073] A third embodiment of the present disclosure will be described below with reference to the drawings. Note that the basic configuration of this embodiment is the same as that of the first embodiment, so a characteristic configuration will be described below.

[0074] Fig. 9 is a diagram showing the upper surface of the piezoelectric element 108 according to the present embodiment. Fig.10 It is along Fig. 9 XX in FIG. 1 is a cross-sectional view taken along line XX in FIG. In the piezoelectric element 108 of the present embodiment, as in the second embodiment, a protective film 304 is formed on both ends of the first electrode 301 in the X direction below the piezoelectric film 110 and on both ends of the second electrode 302 in the X direction above the piezoelectric film 110. More specifically, the protective film 304 is divided and formed on one end side and the other end side of the piezoelectric film 110 in the longitudinal direction of the piezoelectric film 110. In addition, as in the second embodiment, the protective film 304 is formed on the second layer wiring 704 above the contact portion 706. The present embodiment is also different from the second embodiment in that the protective film 304 is not formed on both ends of the first electrode 301 in the Y direction and both ends of the second electrode 302 in the Y direction except for the portions covered by the two ends in the X direction.

[0075] In this embodiment, a diaphragm-shaped piezoelectric element 108 is formed at a position corresponding to the pressure chamber 102. At the center of the pressure chamber 102 (the center in the X direction), as shown in FIG. Fig.10 As shown in FIG, the vibration plate 109, the first electrode 301, the piezoelectric film 110, the second electrode 302, the first insulating film 303, and the second insulating film 604 are sequentially laminated from the pressure chamber 102 side, and the protective film 304 is removed. The protective film 304 thus formed can collectively suppress the peeling of the corners of the piezoelectric film 110 and the electrodes.

[0076] (Fourth embodiment)

[0077] A fourth embodiment of the present disclosure will be described below with reference to the drawings. Note that the basic configuration of this embodiment is the same as that of the first embodiment, so a characteristic configuration will be described below.

[0078] Fig.11 is a diagram showing the upper surface of the piezoelectric element 108 according to the present embodiment. In the piezoelectric element 108 of the present embodiment, the protective film 304 is formed so as to cover the end of the first electrode 301 in the -X direction and the second layer wiring 704 above the contact portion 706 (in the Z direction). In the piezoelectric element 108, the protective film 304 is also formed radially outward at the end of the first electrode 301 in the X direction and at both ends of the second electrode 302 in the X direction.

[0079] More specifically, the protective film 304 extending in the YX direction, the X direction, and the -YX direction is partially provided at the end of the first electrode 301 in the X direction, thereby forming a radial protective film 304. Moreover, the protective film 304 extending in the -XY direction, the -X direction, and the -XY direction is partially provided at the end of the first electrode 301 in the -X direction, thereby forming a radial protective film 304. In addition, the protective film 304 extending in the -XY direction, the -X direction, and the -XY direction is partially provided at the end of the second electrode 302 in the -X direction, thereby forming a radial protective film 304. The protective film 304 extending in the YX direction, the X direction, and the -YX direction is partially provided at the end of the second electrode 302 in the X direction, thereby forming a radial protective film 304. Among the radial protective films 304 toward the outside of the piezoelectric element 108 , the size (area) of the protective films 304 disposed at the corners of the first electrode 301 and the second electrode 302 is larger than the size (area) of the protective films 304 disposed at other positions.

[0080] By forming such a radial protective film 304 , wrinkles are less likely to occur in the protective film 304 near the corners of the piezoelectric film 110 and the electrode when the piezoelectric element 108 is deformed, making it possible to suppress peeling due to the wrinkles.

[0081] (Fifth Embodiment)

[0082] A fifth embodiment of the present disclosure will be described below with reference to the drawings. Note that the basic configuration of this embodiment is the same as that of the first embodiment, so a characteristic configuration will be described below.

[0083] Fig.12 : is a cross-sectional view of the piezoelectric element 108 according to the present embodiment. In the piezoelectric element 108 of the present embodiment, an Al2O3 film (not shown) having a thickness of about 20 nm is formed on the protective film 304, and a protective film 305 having a thickness of about 200 nm is formed thereon. Then, the protective film 305 is etched using photolithography to leave only the protective film 305 on the contact portion 703 side.

[0084] By forming the protective film 305 on the contact portion 703 side in this way, the protective film on the contact portion 703 side is made thicker. This makes it possible to set substantially the same height of the protective film on the contact portion 701 side and the contact portion 703 side. As a result, the deviation of stress on the entire piezoelectric element 108 can be reduced and the occurrence of peeling can be suppressed.

[0085] (Sixth Embodiment)

[0086] A sixth embodiment of the present disclosure will be described below with reference to the drawings. Note that the basic configuration of this embodiment is the same as that of the first embodiment, so a characteristic configuration will be described below.

[0087] Fig.13 is a diagram showing the upper surface of the piezoelectric element 108 according to the present embodiment. Fig.14 It is along Fig.13 A cross-sectional view taken along line XIV-XIV in FIG. Fig.15 It is along Fig.13 104 is a cross-sectional view taken along the line XV-XV in FIG. The piezoelectric element 108 of the present embodiment has a wiring structure different from the multilayer wiring configuration of the above embodiment. More specifically, two types of wiring (wiring for the first electrode 301 and wiring for the second electrode 302) are located in the same layer. Since the two types of wiring are located in the same layer in the thickness direction, it is sufficient to have a first insulating film 303 that insulates the wiring 1503 from the first electrode 301, and the second insulating film 604 is not used.

[0088] like Fig.14 As shown in , a diaphragm-shaped piezoelectric element 108 is formed at a position corresponding to the pressure chamber 102. At the center of the pressure chamber 102 in the X direction, the vibration plate 109, the first electrode 301, the piezoelectric film 110, the second electrode 302, and the first insulating film 303 are laminated in order from the pressure chamber 102 side, and the protective film 304 is removed. Fig.15 As shown in FIG. 1 , a protective film 304 is formed at the end of the piezoelectric element 108 .

[0089] like Fig.15 As shown in FIG. 1 , in the piezoelectric element 108 of the present embodiment, a TEOS oxide film as a first insulating film 303 and a SiN film as a protective film 304 are formed over the piezoelectric film 110. In the piezoelectric element 108, a contact portion 1501 between the first electrode 301 and the wiring 1503 and a contact portion 1502 between the second electrode 302 and the wiring 1503 are formed, and the wiring 1503 is formed on the first insulating film 303.

[0090] In each of the above embodiments, the individual piezoelectric elements are arranged in the Y direction at a density of 150 npi (nozzles per inch). The dimensions of the piezoelectric element 108 are 500 μm in length in the X direction and 110 μm in width in the Y direction. The ejection port 101 (see FIG. 1 ) has a diameter of 25 μm and a thickness of 30 μm. The first channel substrate 105 has a thickness of 100 μm. The dimensions of the pressure chamber 102 are 550 μm in length in the X direction, 120 μm in width in the Y direction, and 100 μm in height in the Z direction.

[0091] By forming the protective film 304 in this way, even in a wiring configuration in which two types of wiring are located in the same layer, peeling due to stress concentration is less likely to occur, thereby making it possible to suppress peeling from the ends of the piezoelectric film 110 and the electrode and peeling in the wiring above the contact portion between the electrode layer and the wiring.

[0092] While 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 following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A liquid ejection head, comprising: Laminates of: a substrate having a pressure chamber formed therein, the pressure chamber being communicated with a spray port for spraying liquid, a vibrating plate that vibrates to generate pressure in the liquid in the pressure chamber, a piezoelectric film that causes the vibration plate to vibrate by applying a voltage to the piezoelectric film, a first electrode provided on one surface of the piezoelectric film between the piezoelectric film and the vibration plate, and a second electrode provided on the other surface of the piezoelectric film; a first wiring connected to the first electrode through a first contact portion; a second wiring connected to the second electrode through a second contact portion; as well as A protective film, when viewed from a direction perpendicular to the substrate, within a range overlapping with the pressure chamber, at one end side and the other end side of the piezoelectric film in the longitudinal direction of the piezoelectric film, the protective film having at least a first part and a second part, the first part covering a partial area including the end of the first electrode, the first contact portion, and the first wiring, and the second part covering a partial area including the end of the second electrode, the second contact portion, and the second wiring.

2. The liquid ejection head according to claim 1, wherein When viewed from a direction perpendicular to the substrate, in a region of the substrate overlapping the pressure chamber, a region without the protective film is larger than a region with the protective film.

3. The liquid ejection head according to claim 1, wherein The protective film continuously covers a region overlapping with a periphery of the piezoelectric film when viewed from a direction perpendicular to the substrate.

4. The liquid ejection head according to claim 1, wherein The protective film covers both end portions of the piezoelectric film to which the first contact portion and the second contact portion are provided.

5. The liquid ejection head according to claim 1, wherein The first wiring is connected to the first electrode through a relay portion.

6. The liquid ejection head according to claim 5, wherein The first electrode is connected to the relay portion through the first contact portion, and the relay portion is connected to the first wiring through a third contact portion.

7. The liquid ejection head according to claim 6, further comprising: a first insulating film that insulates the relay portion from the first electrode except for the first contact portion; as well as A second insulating film insulates the relay portion from the first wiring except for the third contact portion.

8. The liquid ejection head according to claim 4, wherein When viewed from a direction perpendicular to the substrate, a boundary of the piezoelectric film between the two end portions is partially covered by a plurality of protective films.

9. The liquid ejection head according to claim 4, wherein The two end portions are partially covered with a plurality of protective films, and the protective films are provided radially outward from a region of the piezoelectric film.

10. The liquid ejection head according to claim 9, wherein When viewed from a direction perpendicular to the substrate, an area of ​​the protective film disposed at a corner of the first electrode and the second electrode is larger than an area of ​​the protective film disposed at other positions.

11. The liquid ejection head according to claim 4, wherein The thickness of the protective film covering the end portion of the piezoelectric film provided with the first contact portion is greater than the thickness of the protective film covering the end portion of the piezoelectric film provided with the second contact portion.

12. The liquid ejection head according to claim 3, wherein When viewed from a direction perpendicular to the substrate, a length of the protective film protruding outward from an end portion of the first electrode is greater than or equal to 5 μm and less than or equal to 10 μm.

13. The liquid ejection head according to claim 12, wherein The protective film covers a portion of the second electrode where the protective film intrudes inward from an end portion of the second electrode by 5 μm or more and 10 μm or less when viewed in a direction perpendicular to the substrate.

14. The liquid ejection head according to claim 1, wherein When viewed from a direction perpendicular to the substrate, a relationship of We×0.7≤Wc1≤We is satisfied, where Wc1 is the width of the first contact portion in the width direction of the piezoelectric film and We is the width of the piezoelectric film in the width direction.

15. The liquid ejection head according to claim 1, wherein When viewed from a direction perpendicular to the substrate, a relationship of Wa×0.7≤Wc2≤Wa is satisfied, where Wc2 is the width of the second contact portion in the width direction of the piezoelectric film and Wa is the width of the piezoelectric film in the width direction.

16. The liquid ejection head according to claim 1, wherein The film thickness × Young's modulus E of the protective film is greater than or equal to 10% of the film thickness × Young's modulus Ep of the piezoelectric film and less than or equal to 80% of the film thickness × Young's modulus Ep of the piezoelectric film, where Young's modulus E is the Young's modulus of the protective film and Young's modulus Ep is the Young's modulus of the piezoelectric film.

17. The liquid ejection head according to claim 1, wherein The residual stress of the protective film is within ±100 MPa.

18. The liquid ejection head according to claim 1, wherein The protective film is made of an inorganic material and contains at least SiN, SiO, or any one of Al, Zr, and Hf.

19. A liquid ejection head, comprising: Laminates of: a substrate having a pressure chamber formed therein, the pressure chamber being communicated with a spray port for spraying liquid, a vibrating plate that vibrates to generate pressure in the liquid in the pressure chamber, a piezoelectric film that causes the vibration plate to vibrate by applying a voltage to the piezoelectric film, a first electrode provided on one surface of the piezoelectric film between the piezoelectric film and the vibration plate, and a second electrode provided on the other surface of the piezoelectric film; a wiring layer connected to the first electrode through a first contact portion and connected to the second electrode through a second contact portion; as well as A protective film, when viewed from a direction perpendicular to the substrate, within a range overlapping with the pressure chamber, on one end side and the other end side of the piezoelectric film in the longitudinal direction of the piezoelectric film, the protective film having at least a first part and a second part, the first part covering a partial area including the end of the first electrode and the first contact portion, and the second part covering a partial area including the end of the second electrode and the second contact portion.

20. A piezoelectric actuator for a liquid ejection head, comprising: Laminates of: a substrate having a pressure chamber formed therein, the pressure chamber being communicated with a spray port for spraying liquid, a vibrating plate that vibrates to generate pressure in the liquid in the pressure chamber, a piezoelectric film that causes the vibration plate to vibrate by applying a voltage to the piezoelectric film, a first electrode provided on one surface of the piezoelectric film between the piezoelectric film and the vibration plate, and a second electrode provided on the other surface of the piezoelectric film; a first wiring connected to the first electrode through a first contact portion; a second wiring connected to the second electrode through a second contact portion; as well as A protective film, when viewed from a direction perpendicular to the substrate, within a range overlapping with the pressure chamber, at one end side and the other end side of the piezoelectric film in the longitudinal direction of the piezoelectric film, the protective film having at least a first part and a second part, the first part covering a partial area including the end of the first electrode, the first contact portion, and the first wiring, and the second part covering a partial area including the end of the second electrode, the second contact portion, and the second wiring.

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