Manufacturing method of liquid ejection head and liquid ejection head

Abstract

To stably reduce a thickness of a protection film covering a membrane-type piezoelectric element, and stably provide a liquid ejection head including a piezoelectric element with a desired displacement amount.SOLUTION: There is provided a manufacturing method of a liquid ejection head. The liquid ejection head includes an element substrate including: a piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode on a surface of a substrate in this order; wiring connected to the piezoelectric element; a terminal for supplying an electric signal and connected to the wiring; an inorganic structure arranged at a position not overlapping the piezoelectric element, the wiring, and the terminal when viewed from a direction vertical to the surface of the substrate; and a protection film that covers at least the piezoelectric element, the wiring, and the inorganic structure. The manufacturing method includes a step of etching the protection film to form a region in which part of the protection film overlapping the piezoelectric element when viewed from the direction vertical to the surface of the substrate is removed, and removing the protection film overlapping the inorganic structure to expose the inorganic structure.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a liquid ejection head and a liquid ejection head.

Background Art

[0002] In recent years, with the development of MEMS technology (Micro Electro Mechanical Systems), thin-film piezoelectric elements based on semiconductor processes have been proposed. Main applications include, for example, acceleration sensors and liquid ejection heads of inkjet printers.

[0003] In a liquid ejection head, in order to increase the displacement amount of a piezoelectric element and improve ejection performance, a configuration in which the upper layer of a piezoelectric film is opened is known. In Patent Document 1, a liquid ejection head is disclosed in which, among protective films covering a membrane-type piezoelectric element, the portion overlapping the upper electrode is removed to reduce the deformation inhibition of the piezoelectric film by the protective film.

[0004] In the liquid ejection head disclosed in Patent Document 1, the protective layer on the piezoelectric film is removed and the upper electrode is exposed. In this case, the long-term reliability of the piezoelectric element may be insufficient. In the manufacturing process, the piezoelectric element is sealed by being covered with a separate member. However, depending on the sealing ability of the separate member covering the piezoelectric element, there is a risk that the long-term reliability of the piezoelectric element will be insufficient, particularly when using aqueous ink. Also, when etching the protective film covering the piezoelectric element by vacuum plasma etching, if the upper electrode is continuously exposed to the plasma atmosphere, the upper electrode may function as a catalyst and cause damage to the piezoelectric film.

[0005] Patent Document 2 discloses a liquid ejection head in which the protective film is thinned to such an extent that the upper electrode is not exposed on the upper layer of the piezoelectric film. Thereby, while maintaining the sealing performance of the piezoelectric element, the displacement amount can be improved.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-32880 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-196838 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] As described above, in thinning the protective film on the piezoelectric element, control of the removal thickness is important. For controlling the remaining amount of the protective film, for example, there is a method of calculating the etching rate based on the etching time and controlling the etching amount (remaining film amount) by managing the etching time. However, in the method of controlling the etching amount by controlling the etching time, there may be a lack of stability such that variations in the etching amount itself and variations between different wafers are likely to occur due to changes in the state of the etching apparatus. When the remaining film amount of the protective film on the piezoelectric element is different, there may arise a problem that the displacement amount of the piezoelectric element fluctuates.

[0008] The present invention has been made in view of the above problems, and an object thereof is to stably thin the protective film covering the piezoelectric element in a membrane-like piezoelectric element and stably provide a liquid ejection head provided with a piezoelectric element having a desired displacement amount. [Means for Solving the Problems]

[0009] The present invention for solving the above problems includes a piezoelectric element having a first electrode, a piezoelectric film, and a second electrode in this order on a surface of a substrate, a wiring connected to the piezoelectric element, a terminal connected to the wiring for supplying an electric signal for driving the piezoelectric element, an inorganic structure disposed at a position where the piezoelectric element, the wiring, and the terminal do not overlap when viewed from a direction perpendicular to the substrate, and a protective film covering at least the piezoelectric element, the wiring, and the inorganic structure. A method for manufacturing a liquid ejection head including an element substrate, the method including a step of etching the protective film to form a region where a part of the protective film overlapping the piezoelectric element is removed and an opening where the protective film overlapping the inorganic structure is removed to expose the inorganic structure when viewed from a direction perpendicular to the surface of the substrate.

[0010] Further, the present invention includes a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode in this order on a surface of a substrate, a wiring connected to the piezoelectric element, a terminal connected to the wiring for supplying an electric signal for driving the piezoelectric element, and a protective film covering at least the piezoelectric element and the wiring. The protective film has a region where a part of the protective film overlapping the piezoelectric element is removed in a direction perpendicular to the surface of the substrate. In a liquid ejection head, an inorganic structure is disposed at a position where the piezoelectric element, the wiring, and the terminal do not overlap when viewed from a direction perpendicular to the surface of the substrate, and the inorganic structure is exposed from an opening of the protective film.

Advantages of the Invention

[0011] According to the present invention, in a membrane-like piezoelectric element, the thinning of the protective film covering the piezoelectric element can be stably performed, and a liquid ejection head including a piezoelectric element having a desired displacement amount can be stably provided.

Brief Description of the Drawings

[0012]

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Mode for Carrying Out the Invention

[0013] The mode for carrying out the present invention will be described with reference to the drawings. Components having the same function may be given the same reference numerals, and repeated descriptions may be omitted. Hereinafter, an example in which the present invention is applied to a liquid ejection head provided in a liquid ejection device as an inkjet printer will be described. However, the present invention is not limited to the embodiments shown below, and can be changed within the scope that those skilled in the art can conceive, such as other embodiments, additions, modifications, deletions, etc. As long as the present invention exhibits its functions and effects in any aspect, it is included in the scope of the present invention. Note that the components described below are merely examples, and are not intended to limit the scope of the present invention only to them. The present invention will be described with specific examples using a liquid ejection recording head, but is not limited to these examples, and various modifications and changes are possible within the scope of the gist thereof.

[0014] (First Embodiment) <Configuration of the Liquid Ejection Device> FIG. 1 is another view showing an example of the configuration of a liquid ejection apparatus. The liquid ejection apparatus shown in FIG. 1 is of a one-pass type that records an image with a single movement of the recording medium 1. It is an example of a liquid ejection apparatus (hereinafter also referred to as the apparatus main body) provided with a liquid ejection head 4 as a full-line head in which element substrates having ejection ports for ejecting liquid are arranged across the side corresponding to the entire width of the recording medium 1. The recording medium 1 is conveyed in the direction of the arrow by the conveying means 2, and recording is performed by the liquid ejection head 4. The liquid ejection head according to the present invention can be implemented in any form including FIG. 1 and the example of FIG. 1, and other forms are not limited either. In FIG. 1, a liquid ejection apparatus equipped with eight liquid ejection heads (4Ka, 4Kb, 4Ya, 4Yb, 4Ma, 4Mb, 4Ca, 4Cb) is shown. These eight liquid ejection heads are positioned in the liquid ejection apparatus by a reference member. In the figure, the X direction is the conveyance direction of the recording medium 1, the Y direction is the width direction of the recording medium 1, and the Z direction is a direction intersecting the X direction and the Y direction and is the direction opposite to the direction in which the liquid is ejected. In the following description, the Z direction may also be referred to as the height direction.

[0015] Note that, as described above, the liquid ejection head 4 of the present embodiment is a so-called page-wide type head of a one-pass type having a length corresponding to the width of the recording medium 1 (the size in the direction orthogonal to the conveyance direction of the recording medium). However, the present invention can also be applied to a so-called serial type liquid ejection head that performs recording while scanning the liquid ejection head with respect to the recording medium. Examples of the serial type liquid ejection head include a configuration in which one element substrate for black ink and one element substrate for color ink are each mounted. Another example is a configuration of a liquid ejection head that is shorter in width than the recording medium, in which several element substrates are arranged such that the ejection ports overlap in the ejection port row direction.

[0016] <Configuration of the liquid ejection head> Fig. 2 shows a perspective view of the liquid ejection head 4, and Fig. 3 shows a perspective view of the liquid ejection unit 7. In the liquid ejection head 4 according to the present embodiment, a plurality of liquid ejection units 7 each having an ejection port 101 for ejecting a liquid are fixed on a support member 40. Note that the present invention can be preferably applied even to a liquid ejection head configured to fix only one liquid ejection unit 7 on one support member.

[0017] As shown in Fig. 2, a plurality of liquid ejection units 7 are arranged in a staggered pattern on the liquid ejection head 4. Each liquid ejection unit 7 is provided with approximately 1000 ejection ports 101, enabling recording at 1200 dpi. As shown in Fig. 3, an electric wiring substrate 20 such as a flexible wiring substrate is connected to the element substrate 10. The electric wiring substrate 20 is configured to supply energy and electric signals for ejecting a liquid to the ejection ports, and is electrically connected to a pad portion 202 (see Fig. 5) which is a terminal of the element substrate 10.

[0018] Further, the liquid ejection head 4 has a supply unit (not shown) in which a circulation flow path for supplying or recovering ink supplied from an ink tank of the liquid ejection device to the liquid ejection unit 7 is formed. Note that the supply unit does not necessarily have to be configured to recover ink from the liquid ejection unit.

[0019] <Configuration of the element substrate> FIG. 4 is a diagram showing the flow path configuration in the element substrate 10 of the liquid ejection head according to the present embodiment. FIG. 4(a) is a top view seen from the side of the ejection port 101, and FIG. 4(b) is a cross-sectional view taken along line IVb-IVb in FIG. 4(a). The element substrate 10 includes three types of substrates (a first flow path substrate 105, a second flow path substrate 106, and a third flow path substrate 107), and forms a flow path by combining each substrate. As shown in FIG. 4(a), the flow path block 100 includes ejection ports 101 arranged along the Y direction, pressure chambers 102 prepared to communicate with each of these ejection ports 101, and supply flow paths 103. Each of the supply flow paths 103 connected to the common liquid chamber 104 supplies ink to the pressure chamber 102. The arrows in the figure indicate the flow of the liquid (hereinafter also referred to as ink). When the first flow path substrate 105, the second flow path substrate 106, and the third flow path substrate 107 are formed using a general-purpose process of MEMS, it is possible to use a silicon substrate for the three types of substrates. Also, other members such as a mold may be used and formed in combination with the silicon substrate.

[0020] As shown in FIG. 4(b), the element substrate 10 in the present embodiment is configured by laminating a first flow path substrate 105 including an ejection port 101, a second flow path substrate 106 forming a piezoelectric element and a pressure chamber, and a third flow path substrate 107 in the Z direction. The third flow path substrate 107 is a substrate that isolates the piezoelectric film 110 portion of the piezoelectric element 108 from the ink, and is a substrate including a flow path for supplying ink from the common liquid chamber 104 to the pressure chamber 102.

[0021] A supply flow path 103, a pressure chamber 102, and an ejection port 101 are formed corresponding to each of the individual piezoelectric elements 108. The adjacent pressure chambers 102 are separated by a partition wall and are not affected by the direct pressure of the adjacent piezoelectric elements 108. Here, the piezoelectric element 108 is formed adjacent to the diaphragm 109.

[0022] The ink accommodated in the pressure chamber 102 forms a meniscus at the discharge port 101 in a stable state. When a voltage waveform is applied to the piezoelectric element 108 according to a discharge signal, the piezoelectric element 108 deforms and can expand or contract the pressure chamber 102. By combining the expansion and contraction operations, droplets 113 are generated from the meniscus, and ink droplets are discharged in the -Z direction.

[0023] The ink in the pressure chamber 102 consumed by the discharge operation is supplied from the common liquid chamber 104 by the capillary force of the discharge port 101, and the meniscus is reformed at the discharge port 101. In the present disclosure, a combination of the discharge port 101, the piezoelectric element 108, and the pressure chamber 102 is referred to as a discharge element.

[0024] Here, the piezoelectric element 108 is formed with a first electrode 301, a piezoelectric film 110, a second electrode 302, and a protective film (sealing film) 304 in this order adjacent to the diaphragm 109. The first electrode 301, the second electrode 302, and the protective film 304 will be described later. Also, the piezoelectric element 108 may include a first insulating film 303 and a second insulating film 604 described later.

[0025] The arrangement density of the discharge elements in the extending direction (Y direction) of the discharge port row 200 (see FIG. 5) in which a plurality of discharge ports are arranged may be, for example, 150 npi (nozzle per inch) in the Y direction. It may be arranged at a density of 300 npi, which results in a higher-density nozzle arrangement. Of course, the present invention can be preferably applied even with other arrangement densities. The viscosity of the ink to be used is approximately several cP, and the drive waveform is adjusted so that the minimum ink discharge amount from each discharge port 101 is several pL. When the nozzle density is 300 npi, the liquid chamber width becomes narrower than that at 150 npi, so it is conceivable to ensure the necessary displacement amount by designing the diaphragm 109 thinner.

[0026] In this embodiment, the driving frequency of each piezoelectric element 108 is set to 30 kHz. The driving frequency of the piezoelectric element 108 is often designed to be approximately several tens of kHz. Such a driving frequency can be appropriately set according to the time required for each ejection element to actually eject the ink after applying a voltage to the piezoelectric element 108, refill new ink, and enable the next ejection operation. Also, the diameter of the ejection port 101 is adjusted according to the specifications of the ejected droplets and can generally be selected from approximately 10 to 30 μm. With the above configuration, each of the ejection elements arranged on the element substrate 10 ejects the ink supplied from the ink supply unit in the -Z direction from the ejection port.

[0027] FIG. 5 is a diagram showing the second flow path substrate 106 and is a top view seen from the side where the piezoelectric element 108 is disposed. The second flow path substrate 106 is formed with a piezoelectric film 110 and a pressure chamber 102, which can be preferably formed using a MEMS process using a silicon substrate.

[0028] On the element substrate 10, a plurality of ejection port rows 200 in which a plurality of ejection ports 101 are arranged at a desired density and range (ejection port row length) along the ±Y direction are arranged in a plurality of rows along the ±X direction. The number of ejection port rows 200 can be selected as any number, such as 1 row, 2 rows, 8 rows, etc. The ejection port density can be selected as any value, such as 150 npi, or 300 npi in the case of a large density. The ejection port row length is generally selected from about 0.5 inches to about 1.5 inches for long ones.

[0029] On the flow path substrate 106 that constitutes the element substrate 10 shown in FIG. 5, a piezoelectric element 108 with a thin film structure capable of expanding and contracting the volume of the pressure chamber is provided in the pressure chamber 102. Connected to the piezoelectric element 108 are a wiring 201 for supplying an electrical signal corresponding to a first electrode 301 and a second electrode 302 (see FIG. 6) described later, and a pad portion 202 for electrical connection with an electrical wiring substrate such as a flexible wiring substrate. In FIG. 5, the drawing of the wiring 201 except for the connection portion with the pad portion 202 is omitted. The shape of the pad portion 202 can be appropriately selected according to the mounting method. The pad portion 202 may be concentrated and arranged on only one side of the flow path substrate 106 as shown in FIG. 5, or may be divided and arranged on both sides. When concentrated and arranged on one side of the flow path substrate 106, there is an advantage that the number of members such as electrical wiring substrates mounted on one element substrate and the mounting process can be reduced. In particular, when using a flexible wiring substrate with an IC mounted as a mounting member, the effect of reducing the member cost becomes significant. However, when the wiring 201 and the pad portion 202 are concentrated on one side, the wiring density on the flow path substrate 106 increases, so the arrangement constraints of the wiring 201 become severe, and it may be necessary to optimize the arrangement of the wiring 201. In that case, the dimensions of Line and Space in the wiring design rules may be made smaller. Also, by making the wiring 201 into a laminated structure and distributing the wiring to each layer, it is possible to avoid the constraints of the planar arrangement space.

[0030] The piezoelectric element 108 will be described in detail. FIGS. 6 to 8 are diagrams showing the piezoelectric element 108, FIG. 6 is a top view, FIG. 7 is a cross-sectional view taken along VII-VII of FIG. 6, and FIG. 8 is a cross-sectional view taken along VIII-VIII of FIG. 6. As shown in FIG. 8, the piezoelectric element 108 is sequentially formed from the pressure chamber 102 side formed in the Si layer 600 of the flow path substrate 106, a diaphragm 109, a first electrode 301, a piezoelectric film 110, a second electrode 302, a first insulating film 303, a second wiring 702 and a relay portion 705, a second insulating film 604, a first wiring 704, and a protective film 304 are laminated. The first insulating film 303 insulates the relay portion 705 and the first electrode 301 in a region other than the contact portion 703, and the second insulating film 604 insulates the relay portion 705 and the first wiring 704 in a region other than the contact portion 706. The protective film 304 is partially opened in a region located above the second electrode 302 (+Z direction), and a region 203 is formed in which an inorganic film (protective film) covering the second electrode 302, such as the first insulating film 303 and the protective film 304, is thinned or removed.

[0031] The diaphragm 109 can be selected from, for example, a silicon nitride film, silicon, metal, heat-resistant glass, etc., according to the required mechanical properties, reliability, etc.

[0032] The piezoelectric film 110 includes, for example, oxides mainly composed of lithium and niobium or lithium and tantalum (such as lithium niobate, lithium tantalate, etc.), oxides mainly composed of lead and titanium (such as lead titanate, etc.), oxides further added with zirconium thereto (such as lead zirconate titanate, etc.), oxides mainly composed of lead and niobium, oxides mainly composed of barium and titanium (such as barium titanate, etc.), inorganic materials such as zinc oxide, quartz, aluminum nitride, and organic materials such as polylactic acid and polyvinylidene fluoride. Among them, lead zirconate titanate (PZT), which is an oxide mainly composed of lead, zirconium, and titanium and has a high displacement efficiency, can be preferably used. The thickness of the piezoelectric film 110 is determined by the applied voltage and piezoelectric characteristics required to obtain a desired displacement amount, and is generally about 1 to 2 μm. From the viewpoint of controllability, it is desirable to use a material with high linearity as the response displacement to voltage and drive it in a voltage range with high linearity. However, in reality, saturation characteristics, hysteresis characteristics, and non-linearity of electrostriction affect the displacement characteristics. For the film formation of the piezoelectric film, it is possible to select from vacuum sputtering film formation, sol-gel solution film formation, CVD film formation, etc. The piezoelectric film 110 often involves firing after film formation, and is fired at about 600 to 800 °C at most in an oxygen atmosphere using, for example, lamp annealing heating. It may be directly formed on the diaphragm 109 and integrally fired, or formed on a separate substrate, fired, and then peeled and transferred to the diaphragm 109 side, or formed on a separate substrate, peeled and transferred to the diaphragm 109 side, and then integrally formed.

[0033] Since the first electrode 301 may be exposed to a high temperature of several hundred °C in the firing process of the piezoelectric film 110, it is preferably composed of a material with a high melting temperature such as noble metals including Pt and Ir. When the firing process of the piezoelectric film can be separated, Au-based alloys, Al-based alloys, etc. may be selected.

[0034] The second electrode 302 is formed on the piezoelectric film 110, and for example, platinum, titanium, tungsten, or their alloys can be used. Similar to the first electrode 301, in order to improve the adhesion between the second electrode 302 and the piezoelectric film 110, a thin film such as titanium or chromium may be provided between the second electrode 302 and the piezoelectric film 110 as an adhesion layer.

[0035] In order to apply a desired voltage between the first electrode 301 and the second electrode 302 to displace the piezoelectric film 110, a first wiring 704 is electrically connected to the first electrode 301, and a second wiring 702 is electrically connected to the second electrode 302, respectively. Thus, it is configured to apply a potential difference according to an electrical signal sent from the outside to the piezoelectric film 110. The materials forming the first wiring 704 and the second wiring 702 may be the same or different. The materials used for the upper wiring 140 and the lower wiring 150 may be conductors, but it is preferable to use materials with low electrical resistance in order to reduce the probability of disconnection due to electromigration. For example, aluminum, copper, or gold can be mentioned. Further, it may be an alloy composed of two or more of these elements. For example, an Al-based alloy can be preferably used. Also, for the purpose of improving the adhesion of the wiring, a film of titanium or chromium may be provided between each of the first wiring 704 and the second wiring 702 and the film in contact therewith.

[0036] The relay portion 705 bridges the first electrode 301 and the first wiring 704. The second electrode 302 and the second wiring 702 are electrically connected at the contact portion 701. The first electrode 301 and the relay portion 705 are electrically connected at the contact portion 703. Thereby, the second wiring 702 and the first wiring 704 are electrically connected via the piezoelectric film 110.

[0037] In the present embodiment, the wirings (the first wiring 704 and the second wiring 702) are configured to be laminated in multiple layers. When piezoelectric elements are arranged at high density on a substrate, etc., making the wiring a multi-layer configuration has the advantage of increasing the degree of freedom in arranging the piezoelectric elements and the wiring.

[0038] The first insulating film 303 and the second insulating film 604 cover the first electrode 301, the piezoelectric film 110, and the second electrode 302. In this embodiment, as an example, a TEOS oxide film (silicon oxide film) is formed. Note that the TEOS oxide film is just an example, and the first insulating film 303 and the second insulating film 604 can be appropriately selected from general insulator materials such as silicon nitride, silicon oxynitride, and aluminum oxide. It may also be a laminated film in which two or more different films are laminated. For forming the first insulating film 303 and the second insulating film 604, general film formation methods such as chemical vapor deposition (CVD method) or sputtering method can be used. Since it has an excellent production rate, in this embodiment, the TEOS oxide film as the first insulating film 303 and the second insulating film 604 is formed by the CVD method.

[0039] When an oxide-based ceramic is used as the piezoelectric film 110, when forming the silicon oxide film which is the first insulating film 303 and the second insulating film 604, the piezoelectric film 110 may be damaged and the piezoelectric characteristics may deteriorate. Therefore, it is more preferable that a protective film for preventing damage to the piezoelectric film 110 is formed on the surface of the piezoelectric film 110 prior to the formation of the first insulating film 303. As a general insulating film used for the first insulating film 303 and the second insulating film 604, an SiO-based film formed by a CVD apparatus is often used. At this time, the oxide (piezoelectric film 110) on the film formation side may be easily reduced during the gas reaction. Once reduced, the interface of the Schottky junction between the piezoelectric film 110 and the second electrode 302 collapses, the leakage characteristics of the piezoelectric film 110 deteriorate, and it may lead to a decrease in long-term reliability. To prevent this, it is effective to form an oxide film such as Al2O3 formed by an ALD apparatus as a protective film for suppressing reduction. Film formation by ALD is preferable because of its excellent step coverage property for the piezoelectric film 110.

[0040] On the other hand, when Al2O3 is exposed to moisture at a high temperature, its surface deteriorates. When the formation process of contact holes and the formation processes of the first wiring 704 and the second wiring 702 described below are carried out with Al2O3 exposed on the outermost surface during the manufacturing process, the surface of the Al2O3 film may be exposed to moisture during cleaning after patterning. In some cases, the moisture remaining on the surface of the Al2O3 film causes the surface of the Al2O3 to deteriorate when the temperature rises during etching or ashing. If the deteriorated Al2O3 exists on the piezoelectric film, it may lead to a decrease in insulation resistance and cause failures. Therefore, it is desirable that the SiN film, which is the protective film 304, is formed in contact so as to cover the Al2O3 serving as the protective film.

[0041] As described above, in the piezoelectric element used in the liquid ejection head, a relatively high voltage is applied to obtain a sufficient displacement amount for ejecting the liquid. Also, when the ejection ports 101 are arranged at a high density, the surface density of the piezoelectric elements 108 on the flow path substrate 106 is high. Under such conditions, when ink is further ejected in a high-humidity environment, current may flow on the surface of the piezoelectric element, leading to failures. In a piezoelectric actuator used in a liquid ejection head for ejecting a liquid such as ink, in particular, the presence of the liquid has a great influence on the piezoelectric actuator. For this reason, the first wiring 704 and the second wiring 702 are covered with the protective film 304 as a passivation film having high moisture resistance and insulation properties. As the protective film 304, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like can be used. In particular, a passivation film containing a silicon nitride film in a part of the film has higher moisture resistance than a silicon oxide film and can obtain sufficient moisture resistance and insulation properties even with a thinner film thickness compared to the case of forming with a silicon oxide film. Therefore, it is preferable because it hardly affects the displacement characteristics of the piezoelectric actuator. Also, it is preferable that the protective film 304 has higher moisture resistance than the first insulating film 303. The moisture resistance of the two layers may be compared using a generally used moisture resistance evaluation method such as the moisture intrusion evaluation described above.

[0042] From the perspective of insulation, it is desirable that the protective film 304 is disposed so as to cover at least the first wiring 704 and the second wiring 702, and the periphery of the piezoelectric film 110, when viewed from a direction perpendicular to the substrate (diaphragm 109). From the perspective of minimizing the influence on the displacement characteristics of the piezoelectric element, it is preferable that the film thickness of the protective film 304 is the minimum required thickness.

[0043] In the piezoelectric element 108 of the liquid ejection head of the present embodiment, since it operates with a bending deformation, it becomes difficult to bend as the film thickness of the layer located above the piezoelectric film 110 (second electrode 302) increases. In order to efficiently bend the piezoelectric element 108, it is desirable to position the neutral plane of the piezoelectric element 108 defined in materials mechanics near the interface between the piezoelectric film 110 and the diaphragm 109, preferably slightly on the diaphragm 109 side. When the first insulating film 303 is formed on the upper layer of the piezoelectric film 110, the neutral plane shifts inside the piezoelectric film 110, making it difficult to bend. Also, when the protective film 304 is formed on the surface layer side of the piezoelectric film 110, it also becomes difficult to bend. Therefore, at the sites where the insulating function and the sealing function of the first insulating film 303, the second insulating film 604, and the protective film 304 are required, such as the electrical contact portions of the wirings (first wiring 704 and second wiring 702) and the electrodes (first electrode 301 and second electrode 302), a necessary film thickness is formed. On the other hand, at other sites above the piezoelectric film 110, it is desirable that the film is thinned leaving only the minimum film thickness required for sealing. By doing so, it becomes possible to improve the displacement efficiency of the bending deformation of the piezoelectric element 108. As shown in FIG. 7, the piezoelectric element 108 of the present embodiment has a region 203 where the inorganic film located on the second electrode 302 is thinned. In the present embodiment shown in FIGS. 7 and 8, in the region 203, the protective film 304 located on the outermost surface is removed, and the second insulating film 604 located on the second electrode 302 side of the protective film 304 is thinned. Note that even if only the protective film 304 located on the outermost surface is thinned in the region 203, or if all the inorganic films located on the second electrode 302 are removed, the present invention can be preferably used.

[0044] <Method for manufacturing piezoelectric element and liquid ejection head> An example of a method for manufacturing the piezoelectric element 108 having the structure shown in FIGS. 6 to 8 will be described with reference to FIG. 9. First, as shown in FIG. 9(a), an SOI (silicon on insulator) substrate to be a diaphragm 109 is prepared, and a silicon thermal oxide film (oxide film 603) as an insulating layer is formed by a wet oxidation method using oxygen and hydrogen gas. In the present embodiment, an SOI substrate having a handle layer (Si layer) 600, a BOX (buried oxide) layer 601 with a thickness of 0.5 to 1.0 μm, and a device layer (Si layer) 602 with a thickness of 0.75 to 1.25 μm is used, and the oxide film 603 has a thickness of 250 nm. A laminated film of Pt / TiO2 / Ti is formed as the first electrode 301 on the oxide film 603. Next, 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. Subsequently, a Ti-based alloy film is formed as the second electrode 302.

[0045] Thereafter, as shown in FIG. 9(b), a resist pattern 901 corresponding to the piezoelectric element 108 is formed by photolithography. By etching the second electrode 302 and the piezoelectric film 110, the second electrode 302 and the piezoelectric film 110 in the region not protected by the resist pattern 901 are removed. The piezoelectric element 108 will be formed at a position corresponding to the pressure chamber 102 formed in the flow path forming step described later. In the present embodiment, the size of the piezoelectric film 110 film is such that the length in the short side direction (Y direction) is 45 to 50 μm and the length in the long side direction (X direction) is 500 to 650 μm. Thereafter, the resist pattern 901 is removed. For example, plasma ashing and organic stripping solution cleaning can be used to remove the resist pattern 901. In FIGS. 9(b) to 9(e) described later, the portion where the pressure chamber 102 is formed is indicated by a dotted line.

[0046] Subsequently, as shown in FIG. 9(c), a resist pattern 902 for patterning the first electrode 301 is formed by photolithography. In the present embodiment, in the directions parallel to the surface of the diaphragm 109 (X direction and Y direction), the resist pattern 902 is formed to be about several μm to 10 μm wider than the region where the piezoelectric film 110 is formed. Subsequently, the layer serving as the layer of the first electrode 301 is etched to form the pattern of the first electrode 301. Thereafter, the resist pattern 901 is removed.

[0047] Next, as shown in FIG. 9(d), an Al2O3 film (not shown) with a thickness of about 20 nm is formed as a protective film for suppressing the reduction of the piezoelectric film 110. Thereafter, a TEOS oxide film with a thickness of about 400 nm is formed as the insulating film 303. Next, the electrical contact portions shown in FIGS. 6 and 8 are formed. A contact portion (contact hole) 701 through which the second electrode 302 and the second wiring 702 are electrically connected is formed, and then a contact portion (contact hole) 703 through which the first electrode 301 and the first wiring 704 are electrically connected is formed.

[0048] Thereafter, an AlCu alloy film is formed, and the second wiring 702, and a relay portion 705 for bridging the first wiring 704 and the first electrode 301 are simultaneously formed in a series of semiconductor processes. Next, a TEOS oxide film with a thickness of 400 nm is formed as the second insulating film 604 for preventing leakage between the wirings, and a contact portion (contact hole) 706 is formed in the second insulating film 604 on the region of the relay portion 705 that is electrically connected to the first electrode 301 (see FIG. 8).

[0049] Note that in this embodiment, the pad portion 202 (see FIG. 5) is desired to be located in the upper layer of the second insulating film 604 (the lower layer of the protective film 304) in the direction perpendicular to the surface of the diaphragm 109. For this reason, in order to connect the second wiring 702 located in the lower layer of the second insulating film 604 to the lower layer of the protective film 304 at the contact portion 701, the second insulating film 604 forms an opening for pad connection (not shown) in the vicinity of the pad portion 202. Subsequently, an AlCu alloy film serving as the first wiring 704 is formed, and the first wiring 704 is formed by a series of semiconductor processes. As a result, the second-layer wiring 704 electrically connected to the first electrode 301 via the relay portion 705 is formed. At the same time, another wiring located in the second layer that electrically connects the first-layer wiring 702 electrically connected to the second electrode 302 to the pad portion 202 is formed. In this way, the wiring 201 corresponding to the first electrode 301 and the second electrode 302 is electrically connected to the pad portion 202, and a configuration in which the wirings are stacked in multiple layers is realized. Thereafter, a SiN film having a thickness of about 200 nm is formed as the protective film 304 on the outermost surface second insulating film 604.

[0050] Thereafter, as shown in FIG. 9(e), the protective film 304 and the second insulating film 604, which are inorganic film layers located on the second electrode 302 of the piezoelectric film 110, are partially removed to form a region 203 where the thickness of the inorganic film on the piezoelectric film 110 is thinner than that of other portions. The method for forming the region 203 will be described later. Finally, the protective film 304 and the second insulating film 604, which are inorganic films on the pad portion 202, are removed to expose the metal surface of the pad portion 202. Through the above steps, the piezoelectric element 108 is completed.

[0051] Subsequently, in the Si layer 600 of the second flow path substrate 106, photolithography is performed from the back side of the region where the piezoelectric film 110 is formed, and a pressure chamber 102 and flow paths are formed by Si deep etching using ICP plasma (see FIG. 1). Finally, the first flow path substrate 105, the second flow path substrate 106, and the third flow path substrate 107 are joined together with an adhesive or the like to complete the element substrate 10 having the piezoelectric element 108.

[0052] Subsequently, necessary electrical mounting with the electrical wiring board 20 is performed, and the liquid ejection head is formed by joining it to a supply unit or the like.

[0053] <Removal of the inorganic film on the piezoelectric film> A method for forming a region 203 in which at least a part of the film located on the second electrode 302 is removed will be described below. The region 203 can be formed by a masking process using a photoresist by photolithography and a removal process by semiconductor plasma etching. The formation process of the region 203 may be provided after forming the protective film 304, or may be performed simultaneously with the opening (exposure) process of the pad portion 202.

[0054] Conventionally, for the formation of the region 203, a method of controlling the etching amount (remaining film amount) by calculating the etching rate and managing the etching time has been adopted. However, in the method of controlling the etching amount by controlling the etching time, variations in the etching amount itself and variations between different wafers are likely to occur due to changes in the state of the etching apparatus or the like. The etching rate is easily affected by the inner wall state of the chamber, the atmosphere in the chamber, plasma stability, and the like. For this reason, when controlling the timing of the end of the etching time by the etching time, the thinning amount (remaining film amount) of the inorganic film in the region 203 is more likely to vary compared to the present invention using the detection member 204.

[0055] To solve this problem, the inventors focused on the EPD (End Point Detector), which is generally installed in semiconductor plasma etching equipment. The EPD is a mechanism that selects the reaction species of interest by spectroscopically analyzing the plasma emission spectrum during plasma etching and grasps the timing of the start and end of the reaction of the reaction species. Fig. 10 shows an example of the waveform detected by the EPD. The horizontal axis represents time, and the vertical axis represents signal intensity. For example, when etching of a specific material starts, a transition in which the signal intensity increases as shown in Fig. 10(a) is detected. Also, in the situation where the etching of a specific material in progress ends, a transition in which the signal intensity decreases as shown in Fig. 10(b) is detected. Furthermore, when a specific material exists as a thin film, a transition (peak) in which the signal intensity increases and then decreases as shown in Fig. 10(c) is detected, and the decrease in intensity means the end of the etching of the thin film. More specifically, a stable end point determination is made using numerical determination including the first derivative coefficient near the peak shape and even the second derivative coefficient.

[0056] In the present embodiment, for the purpose of suppressing the variation in the removal thickness when at least a part of the inorganic film on the upper layer of the second electrode 302 is removed, a detection member 204 as a member detectable by EPD is disposed on the second flow path substrate 106. The detection member 204 is an inorganic structure. In the present embodiment, as shown in FIG. 5, a plurality of them are disposed near the outer peripheral portion of the second flow path substrate 106. FIG. 11 shows a cross-sectional view of the second flow path substrate 106 around the detection member 204 in XI-XI of FIG. 5. On the diaphragm 109, a first insulating film 303, a second insulating film 604, the detection member 204, and a protective film 304 are laminated in this order. On the detection member 204, a protective film 304 similar to that on the second electrode 302 is formed. Therefore, in the etching process of the protective film 304, when a component derived from the detection member 204 is detected by EPD, it is determined that the protective film 304 has been removed and the etching is terminated, so that the region 203 can be formed with good reproducibility of the removal thickness. That is, by detecting the wavelength component of the plasma emission during etching by EPD, it becomes possible to obtain the determination timing for terminating the etching. FIG. 11 shows the structure around the detection member 204 after the formation of the region 203. For the protective film 304, an opening 2041 for exposing the detection member 204 is formed in the upper layer region of the detection member 204. In the present embodiment shown in FIG. 5, the detection member 204 is disposed near the outer peripheral portion of the second flow path substrate 106, but the arrangement is not limited to this. For example, the detection member 204 may be disposed in a dicing region when a single element substrate 10 is cut out and separated.

[0057] In the etching process of the protective film 304 and the second insulating film 604 that form the region 203, any one of a CF-based gas, an SF-based gas, or a chlorine-based gas is often used as the main gas for the etching gas. The detection member 204 is required to be composed of a material that is etched with the etching gas used in the etching process. Therefore, for example, Au, Al, Pt, Ir, Al compounds, Ti compounds, Ta compounds, W compounds, etc. can be used as the detection member 204 in combination with the etching gas. When a chlorine-based gas is used as the etching gas, it is essential not to generate corrosion foreign matter due to the reaction product. Therefore, it is desirable to perform a water-based cleaning immediately after etching to surely remove the residual chlorine.

[0058] The process of forming the detection member 204 may be provided as an independent process, or may be provided using the process of forming the piezoelectric element 108. When using the process of forming the piezoelectric element 108 described above, it is more preferable because there is no increase in the number of processes associated with providing the detection member. When forming the detection member 204 using the process of forming the piezoelectric element 108, the detection member 204 can be formed from the layer forming the first electrode 301 or the wiring (the first wiring 704 or the second wiring 702). When forming the detection member 204 from the layer forming the first electrode 301, the timing when all of the inorganic films (the protective film 304, the second insulating film 604, and the insulating film 303) above the piezoelectric film 110 are removed can be detected. When forming the detection member 204 from the layer forming the first wiring 704, the timing when the protective film 304 located above the first wiring 704 is removed can be detected. When forming the detection member 204 from the layer forming the second wiring 702, the timing when the protective film 304 and the second insulating film 604 located above the second wiring 702 are removed can be detected.

[0059] As a method for controlling the removal thickness of the inorganic film in the region 203, it is also possible to adjust the area of the detection member 204 exposed to the atmosphere of the etching gas, that is, the area of the opening 2041 for exposing the detection member 204. Let the area of the region 203 where at least a part of the inorganic film of the second electrode 302 layer in one piezoelectric element 108 is removed be A, and the exposed area from one detection member 204 be B. If B / A is about 1, since the etching rate is considered to proceed equally between the detection member 204 and the region 203, by detecting the exposure timing of the detection member 204 with EPD, the inorganic film on the upper layer of the second electrode 302 can be processed equally to the upper layer of the detection member 204. In this case, the exposed area of the detection member 204 from one opening 2041 of the inorganic film in the direction parallel to the surface of the diaphragm 109 is preferably 0.5 times or more and 2 times or less, more preferably 0.75 times or more and 1.25 times or less of the area of the region 203.

[0060] When B / A is made smaller than 1, not only physical sputtering in plasma etching but also the contribution of etching involving chemical reactions increases, and the etching rate of the detection member 204 becomes relatively fast. Therefore, within the range of the inorganic film thickness on the upper layer of the detection member 204, it is possible to make an adjustment to leave the inorganic film on the piezoelectric film 110.

[0061] On the other hand, when the opening area ratio B / A is made larger than 1, the etching rate on the detection member 204 side becomes relatively slow. Therefore, it becomes possible to etch the inorganic film on the piezoelectric film 110 to a thickness greater than the thickness of the inorganic film on the detection member 204.

[0062] Thus, by utilizing the dependence of the etching rate on the opening area, regardless of the arrangement constraints of the detection member 204 in the direction perpendicular to the surface of the second circuit board 106 in the laminated structure of the second circuit board 106, the etching amount of the inorganic film on the upper layer of the second electrode 302 can be adjusted. That is, it becomes possible to adjust the remaining thickness of the inorganic film in the region 203.

[0063] It is desirable that the flow path substrate 106 includes a plurality of detection members 204, and the ratio of the total exposed area of the plurality of detection members 204 to the area of the surface on which the piezoelectric element 108 of one second flow path substrate 106 is formed is 5% or more. Alternatively, it is desirable that the ratio of the total exposed area of the plurality of detection members 204 to the total area of the regions 203 of the plurality of piezoelectric elements 108 included in one second flow path substrate 106 is 1 / 4 or more. This is because if the total exposed area of the detection members 204 is too small, the S / N of the emission intensity from the etching reaction included in the plasma emission will be insufficient, making it difficult to detect by EPD. Also, it is preferable to arrange the plurality of detection members 204 to be close to the arrangement density of the piezoelectric film 110.

[0064] (Second Embodiment) In the following description, the focus will be on the differences from the above-described first embodiment, and the description of the parts similar to the configuration of the first embodiment will be omitted.

[0065] In this embodiment, at least a part of the inorganic film on the upper layer of the second electrode 302 and the inorganic film on the upper layer of the pad portion 202 which is an electrical connection portion are removed simultaneously. Thereby, there is an advantage that the number of manufacturing steps of the element substrate and the liquid ejection head can be reduced.

[0066] FIG. 12 is a view showing the second flow path substrate 106, and is a top view seen from the side where the piezoelectric element 108 is arranged. A plurality of detection members 204 are arranged in alignment around the element substrate.

[0067] The pad portion 202 is formed by also using the layer for forming the wiring (the first wiring 704 and the second wiring 702), thereby preventing an increase in the number of manufacturing steps due to providing the detection members 204. As materials for forming the wiring and the detection members 204, for example, an Al alloy, an Al alloy with a barrier metal, or the like can be used.

[0068] Since the element substrate 10 includes the detection member 204, the S / N of the spectrum for detecting the end of the etching for exposing the pad portion 202 from the inorganic film is improved. Therefore, it becomes possible to accurately detect the timing when the pad portion 202 is exposed. It is desirable that the exposed area of the detection member 204 is substantially equal to the exposed area of one pad portion 202 from the inorganic film. More specifically, the exposed area of the detection member 204 from one opening 2041 of the inorganic film in the direction parallel to the surface of the diaphragm 109 is preferably 0.5 times or more and 2 times or less, more preferably 0.75 times or more and 1.25 times or less of the area of the pad portion 202.

Example

[0069] With reference to the drawings, as an example of the present embodiment, a piezoelectric element (piezoelectric actuator) as a fine structure manufactured using a semiconductor process and a liquid ejection head using the same will be described. Hereinafter, the configuration and manufacturing method of the second flow path substrate 106 will be mainly described.

[0070] Note that the components described in the following examples are merely examples, and are not intended to limit the scope of the present invention only to them. The present invention will be described with specific examples using a liquid ejection head, but is not limited to these examples, and various modifications and changes are possible within the scope of the gist.

Example

[0071] To describe the piezoelectric element 108 of Example 1, a cross-sectional view taken along line B-B' of FIG. 2 is shown in FIG. 6. Also, a top view of the vicinity of line B-B' of FIG. 2 is shown in FIG. 7(a), and a cross-sectional view taken along line D-D' of FIG. 7(a) is shown in FIG. 7(b). A cross-sectional view taken along line C-C' of FIG. 2 is shown in FIG. 8. Also, FIG. 9 shows an outline of the formation process of the piezoelectric element 108 in a cross-sectional view taken along line B-B'. Further, FIG. 10 shows an outline of the formation process of the detection member 204 in a cross-sectional view taken along line C-C'.

[0072] In this example, the element substrate and the liquid ejection head shown in the first embodiment are created and configured as shown in FIGS. 6 to 8.

[0073] In this embodiment, the individual ejection elements are arranged at a density of 300 npi in the Y direction. The size of the piezoelectric element 108 is approximately 700 μm in the X direction (length), 50 μm in the Y direction (width), the diameter of the ejection port 101 is 20 μm, the thickness of the nozzle 1011 communicating with the ejection port 101 is 30 μm, and the thickness of the first flow path substrate 105 is 100 μm. The size of the pressure chamber 102 is 750 μm in the X direction (length), 55 μm in the Y direction (width), and 100 μm in the Z direction (height). By setting the arrangement density of the ejection elements to 300 npi, the width of the pressure chamber 102 becomes narrower compared to the density of 150 npi, which is a conventional density of ejection elements in a piezoelectric liquid ejection head. Therefore, it is desirable to ensure the displacement amount of the piezoelectric element 108 required for liquid ejection by forming the region 203 and designing the diaphragm 109 to be thin.

[0074] In Example 1, the detection member 204 having the configuration shown in FIG. 11 is formed simultaneously in the process of forming the piezoelectric element 108. More specifically, the detection member 204 is formed using the layer for forming the first wiring 704 located between the protective film 304 and the second insulating film 604. Thereby, it becomes possible to detect the timing at which the protective film 304 is removed in the region 203.

[0075] With reference to FIGS. 13 and 9, the formation process of the detection member 204 will be described. The cross-sectional view of FIG. 13 is a cross-sectional view at a position corresponding to XI-XI of FIG. 5. First, as shown in FIGS. 13(a) and 9(a), layers to become the first electrode 301, the piezoelectric film 110, and the second electrode 302 are formed on the entire surface of the substrate to become the diaphragm 109. Thereafter, as shown in FIGS. 13(b) and 9(c), the layers to become the first electrode 301, the piezoelectric film 110, and the second electrode 302 are etched to form the piezoelectric element 108, and these layers are removed in the region where the piezoelectric element 108 is not formed.

[0076] Next, a TEOS oxide film with a thickness of 400 nm as the first insulating film 303, a second wiring 702, and a TEOS oxide film with a thickness of 200 nm as the second insulating film 604 are formed on the diaphragm 109, and a layer that will become the first wiring 704 is formed. By etching the layer that will become the first wiring 704, the first wiring 704 and the detection member 204 are formed. Note that the first wiring 704 and the detection member 204 are formed using an AlCu alloy film. Thereafter, an SiN film with a thickness of about 200 nm is formed as the protective film 304 to obtain the state shown in FIGS. 13(c) and 9(d).

[0077] Subsequently, as shown in FIG. 9(e), a region 203 is formed by removing a part of the inorganic film on the upper layer of the second electrode 302. At the same time in this step, as shown in FIG. 13(d), the upper layer (protective film 304) of the detection member 204 is etched to form an opening 2041 and expose the detection member 204. In this embodiment, a chlorine-based etching gas is used. When the AlCu alloy film is exposed from the opening of the detection member 204 by etching and the etching of the AlCu alloy film starts, the signal intensity of the plasma emission derived from Al begins to increase. After maintaining for about 10 seconds at the stage where the signal intensity of Al is stable, the etching is terminated.

[0078] In this embodiment, as shown in FIG. 2, a plurality of detection members 204 were arranged around the flow path substrate 106. The exposed area from the opening 2041 of one detection member 204 was set to be about 1.5 times that of the region 203. Therefore, since the area of the region 203 is narrower than the exposed area from the opening 2041 of the detection member 204, the etching rate of the region 203 becomes relatively faster than the etching rate of the opening 2041. Therefore, in the region 203 on the second electrode 302, the inorganic film (the protective film 304 and the second insulating film 604) can be removed to a depth greater than the thickness of the layer formed on the detection member 204, that is, the protective film 304. Here, the SiN film of the protective film 304 with a thickness of 200 nm and the TEOS oxide film of the second insulating film 604 with a thickness of 200 nm were removed, and a configuration in which the TEOS oxide film of the second insulating film 604 with a thickness of 200 nm and the TEOS oxide film of the insulating film 303 with a thickness of 400 nm remained on the second electrode 302 was obtained with good reproducibility. In this way, by determining the end point of etching using the detection member 204, the thinning amount of the inorganic film on the second electrode 302 (piezoelectric film 110) is stabilized, and the repeatability of the thinning amount between different wafers is also improved.

[0079] In this embodiment, since a chlorine-based gas is used for etching, the chlorine component is removed. After the etching with the chlorine-based gas is completed, the resist is ashed and then the two-fluid cleaning is sufficiently performed to completely remove the chlorine component. Thereafter, the pad portion 202 is opened using a series of semiconductor process steps. On the pad portion 202, an Au film for performing good electrical mounting with the electrical wiring substrate 20 is formed by electroplating growth to a thickness of 1 μm (not shown).

[0080] Subsequently, a series of semiconductor process steps are performed from the back side of the second flow path substrate 106, and a pressure chamber 102 and a flow path are formed in the second flow path substrate 106 by Si deep etching using ICP plasma. Thereafter, the first flow path substrate 105, the second flow path substrate 106, and the third flow path substrate 107, which were formed in separate processes, were joined with an adhesive to complete the element substrate 10 having the piezoelectric element 108.

[0081] Thereafter, necessary electrical implementation was carried out, and a liquid ejection head was formed by bonding a module serving as an ink supply unit and the element substrate 10 with an adhesive.

Example

[0082] In this example, the element substrate and the liquid ejection head shown in the first embodiment were fabricated. In the following description, the focus will be on the differences from the above-described Example 1, and the description of the parts similar to the configuration of Example 1 will be omitted.

[0083] FIG. 14 shows a cross-sectional view of the piezoelectric element 108 and the detection member 204 of this example. The cross-sectional view of the piezoelectric element 108 in FIG. 14 is a cross-sectional view at a position corresponding to VII-VII in FIG. 5.

[0084] Different from Example 1, the exposed area of one detection member 204 was made equal to the area of region 203. In the dry etching process of thinning the inorganic film on the upper layer of the second electrode 302 to form region 203, a CF-based etching gas was used. Also, the detection member 204 was formed from the layer where the first wiring 704 was formed in the same manner as in Example 1, but these detection members 204 and the first wiring 704 were formed using an AlCu alloy film with a TiN film about 20 nm thick formed on the surface opposite to the diaphragm 109.

[0085] A part of the inorganic film is removed by dry etching with a CF-based gas to form region 203. To obtain the timing of the end of etching, attention is paid to the spectrum of plasma emission derived from N of TiN formed on the uppermost layer of the detection member. After detecting the emission spectrum showing from the start to the end of the reaction of TiN of the detection member 204 as shown in FIG. 5(c), etching is terminated after waiting for about 10 seconds. Here, the timing when the protective film 304 on the detection member 204 is removed and the etching of the detection member 204 (TiN) starts corresponds to the timing when the protective film 304 is removed in the region 203 on the piezoelectric film 110 and the etching of the second insulating film 604 starts. The etching rate of TiN constituting the uppermost layer of the detection member 204 is slower than the etching rate of the TEOS oxide film of the second insulating film 604. Therefore, by waiting for the end of the etching of TiN with a thickness of 20 nm, the TEOS film is removed with a thickness several times or more that of 20 nm.

[0086] In this embodiment, as the inorganic film on the second electrode 302, a 200-nm SiN film of the protective film 304 and an approximately 250-nm TEOS oxide film of the second insulating film 604 are removed, and on the second electrode 302, there remains an approximately 150-nm TEOS oxide film of the second insulating film 604 and a 400-nm TEOS oxide film of the first insulating film 303, obtaining a configuration.

[0087] When the uppermost layer of the first wiring 704 is formed of AlCu, in the etching with the CF-based gas used in this embodiment, AlCu is hardly etched, so it is considered difficult to detect the peak derived from Al as in Example 1. In this embodiment, the first wiring 704 has a laminated structure in which TiN that can be etched with a CF-based gas is formed on the AlCu alloy. Thereby, the timing of the end of etching can be obtained from the spectrum of plasma emission derived from N of TiN. It is preferable to appropriately select the combination of the type of gas used for etching and the composition of the uppermost layer of the detection member 204 or the type of element to be detected as in this embodiment.

[0088] In the etching of CF-based gas, the etching rate of the TiN film is slower than that of the inorganic films (the SiN film which is the protective film 304 and the TEOS oxide film 604 which is the second insulating film 604). Therefore, by waiting for the decrease in the peak of the emission spectrum derived from N in the TiN film and then ending the etching, a configuration in which the thickness of the inorganic film located on the second electrode 302 is reduced to the same extent as in Example 1 as shown in FIG. 14 can be obtained with good reproducibility.

Example

[0089] In this example, the element substrate and the liquid ejection head shown in the first embodiment were fabricated. In the following description, the focus will be on the differences from Example 1 described above, and the description of the parts similar to the above-described configuration will be omitted.

[0090] FIG. 15 shows a cross-sectional view around the piezoelectric element 108 and the detection member 204 after the formation of the region 203 in this example.

[0091] In this example, different from Example 1 and Example 2, the detection member 204 is located between the first insulating film 303 and the second insulating film 604 in the direction perpendicular to the surface of the diaphragm 109. Therefore, the detection member 204 is formed using the layer in which the second wiring 702 located between the first insulating film 303 and the second insulating film 604 is formed in the piezoelectric element 108. Thereby, it becomes possible to detect the timing when the protective film 304 and the second insulating film 604 are removed in the region 203.

[0092] Note that the exposed area from the opening 2041 of one detection member 204 was made equal to the area of the region 203. Also, in the dry etching process for forming the region 203, a chlorine-based etching gas was used. The uppermost layer of the detection member 204 and the second wiring 702 is an AuCu alloy, and the end point of etching was detected using the signal intensity of the plasma emission derived from Al.

[0093] In the step of etching the protective film 304 (SiN film) and the second insulating film 604 (TEOS oxide film), which are inorganic layers located above the piezoelectric film 110, the inorganic layer of the upper layer of the detection member 204 is etched simultaneously. An opening 2041 is formed to expose the detection member 204. When the AlCu alloy is exposed from the opening 2041 of the detection member 204 by etching and the etching of the AlCu alloy film is started, the signal intensity of the plasma emission derived from Al begins to increase. After maintaining for about 10 seconds at the stage where the signal intensity of Al is stabilized, the etching is terminated.

[0094] Since a chlorine-based gas is used for etching, the chlorine component is removed. After the etching with the chlorine-based gas is completed, the resist is ashed and then the two-fluid cleaning is sufficiently performed to completely remove the chlorine component.

[0095] In this embodiment, as the inorganic film on the second electrode 302, the SiN film of the protective film 304 and the TEOS oxide film of the second insulating film 604 are removed. Furthermore, about 100 nm of the TEOS oxide film of the first insulating film 303 is also removed, and a configuration in which about 300 nm of the insulating film 303 remains on the second electrode 302 is obtained with good reproducibility.

Example

[0096] In this embodiment, the element substrate and the liquid ejection head shown in the first embodiment are fabricated. In the following description, the points different from those in the above-described Example 1 will be mainly described, and the parts similar to the above-described configuration will be omitted from the description.

[0097] FIG. 16 shows a cross-sectional view around the piezoelectric element 108 and the detection member 204 after the formation of the region 203 in this embodiment.

[0098] In this embodiment, similar to Example 3, the detection member 204 is located between the first insulating film 303 and the second insulating film 604 in the direction perpendicular to the surface of the diaphragm 109. The detection member 204 is formed using the layer for forming the second wiring 702.

[0099] In the etching process of thinning the inorganic film on the piezoelectric film 110 to form the region 203, a CF-based etching gas was used in the same manner as in Example 2. Further, the second wiring 702 and the detection member 204 are formed using an AlCu alloy film on which TiN with a thickness of about 20 nm is formed on the uppermost surface on the opposite side of the diaphragm 109.

[0100] The arrangement position of the detection member 204 on the surface of the second flow path substrate 106 is the same as that in Example 1. Further, the exposed area of one detection member 204 is made equal to the area of the region 203.

[0101] The inorganic film is thinned by dry etching with a CF-based gas to form the region 203. To obtain the timing of the end of etching, attention is paid to the spectrum of plasma emission derived from C of the CF-based gas and N of TiN formed on the uppermost layer of the detection member. After the reaction of TiN of the detection member 204 starts as shown in FIG. 10(c), it is confirmed that the emission intensity starts to decrease, and then the etching is terminated. Here, the timing when the protective film 304 and the second insulating film 604 on the detection member 204 are removed and the etching of the detection member 204 (TiN) starts corresponds to the timing when the protective film 304 and the second insulating film 604 are removed on the second electrode 302 and the etching of the first insulating film 303 starts. The etching rate of TiN constituting the uppermost layer of the detection member 204 is slower than the etching rate of the TEOS oxide film of the first insulating film 303. Therefore, by waiting for the end of etching of 20 nm thick TiN, the first insulating film 303 is removed with a thickness several times or more that of 20 nm in the region 203. In this example, since the etching is terminated after confirming the end of etching of TiN on the uppermost layer of the detection member 204, the inorganic film on the second electrode 302 can be made thinner than in Example 3.

[0102] In this example, as the inorganic film on the second electrode 302, a configuration in which a 200 nm SiN film of the protective film 304, a 400 nm TEOS oxide film of the second insulating film 604, and further about 250 nm of the TEOS oxide film of the first insulating film 303 are removed and about 150 nm of the TEOS oxide film of the first insulating film 303 remains can be obtained with good reproducibility.

Example

[0103] In this embodiment, the element substrate and the liquid ejection head shown in the first embodiment were fabricated. In the following description, the description will focus on the differences from the above-described Example 1, and the parts similar to the above-described configuration will be omitted from the description.

[0104] FIG. 17 shows a top view of the flow path substrate 106 in this embodiment. FIG. 18 shows a cross-sectional view around the piezoelectric element 108 and the detection member 204 after the formation of the region 203 in this embodiment. The cross-sectional view of the piezoelectric element 108 in FIG. 17 is the cross-sectional view taken along XVIII-XVIII in FIG. 17. Further, FIG. 19 shows a cross-sectional view of the piezoelectric element 108 taken along XIX-XIX in FIG. 17.

[0105] In this embodiment, the individual ejection elements are arranged at a density of 150 npi in the Y direction, which is different from those in Examples 1 to 4. The size of the piezoelectric element 108 is approximately 500 μm in the X direction (length) and 110 μm in the Y direction (width). The diameter of the ejection port 101 is approximately 25 μm, the thickness of the nozzle 1011 communicating with the ejection port 101 is 30 μm, and the thickness of the first flow path substrate 105 is 100 μm. The size of the pressure chamber 102 is 550 μm in the X direction (length), 120 μm in the Y direction (width), and 100 μm in the Z direction (height).

[0106] In this embodiment, it is different from the multilayer wiring configurations in Examples 1 to 4. The two types of wirings connected to the first electrode 301 and the second electrode 302, respectively, are configured to be located in the same layer (at the same height) in the height direction (Z direction) without being laminated. Therefore, it is sufficient to have the first insulating film 303 that insulates the wiring 1503 and the first electrode 301, and it does not have the second insulating film 604 that was arranged between the first wiring 704 and the second wiring 702 in the height direction in Examples 1 to 4.

[0107] As shown in FIGS. 18 and 19, in the piezoelectric element 108 of this embodiment, a TEOS oxide film with a thickness of 400 nm as the first insulating film 303 is formed on the upper layer of the second electrode 302. A wiring 1503 is formed on the upper layer of the insulating film 303, and the first electrode 301 and the wiring 1503 are electrically connected at the contact portion 1501, and the second electrode 302 and the wiring 1503 are electrically connected at the contact portion 1502, respectively. Then, a protective film 304 with a thickness of 200 nm is formed so as to cover the first insulating film 303 and the wiring 1503.

[0108] In this embodiment, the detection member 204 is formed using the layer for forming the wiring 1503. The wiring 1503 and the detection member 204 are formed using an AlCu alloy film with a TiN film having a thickness of about 20 nm formed on the surface opposite to the diaphragm 109. The opening area of one detection member 204 is made equal to the area of the region 203.

[0109] In the etching process of forming the region 203 by removing at least a part of the inorganic films (protective film 304 and first insulating film 303) on the upper layer of the second electrode 302, a CF-based etching gas is used as in Embodiment 2 and Embodiment 4. When the SiN film which is the protective film 304 is etched, TiN is exposed on the surface layer of the detection member 204. When etching TiN with a CF-based gas, attention is paid to the spectrum of the plasma emission derived from C of the CF-based gas and N of the TiN formed on the uppermost layer of the detection member 204. As shown in FIG. 5(c), after detecting the start of the reaction of the TiN located on the uppermost layer of the detection member 204 and confirming a clear rise in the emission intensity, etching is terminated after waiting for about 10 seconds. That is, etching is terminated immediately at the stable timing when the etching of the TiN film starts. As a result, as shown in FIG. 17, as the inorganic film on the second electrode 302, about 200 nm of the SiN film of the protective film 304 and about 100 nm of the TEOS oxide film of the first insulating film 303 are removed, and a configuration in which about 300 nm of the TEOS oxide film of the first insulating film 303 remains is obtained with good reproducibility.

Example

[0110] In this embodiment, the element substrate and the liquid ejection head shown in the second embodiment were fabricated. In the following description, the focus will be on the differences from the above-described Example 1, and descriptions of parts that are the same as the above-described configuration will be omitted.

[0111] Fig. 20 shows a cross-sectional view around the piezoelectric element 108 and the detection member 204 after the formation of the region 203 in this embodiment. The cross-sectional view of the piezoelectric element 108 in Fig. 20 is a cross-sectional view at a position corresponding to XX-XX in Fig. 12.

[0112] In this embodiment, the detection member 204 is located between the protective film 304 and the insulating film 604 in a direction perpendicular to the surface of the diaphragm 109. Therefore, the detection member 204 is formed using the layer for forming the first wiring 704 that is located between the protective film 304 and the second insulating film 604 in the piezoelectric element 108. Also, the pad portion 202 is formed in the same manner as the detection member 204, using the layer for forming the first wiring 704. The first wiring 704, the detection member 204, and the pad portion 202 are formed using an AlCu alloy film. The exposed area of one detection member 204 is made equal to the exposed area from the protective film 304 of the pad portion 202.

[0113] The inorganic films (protective film 304, first insulating film 303, and second insulating film 604) located on the second electrode 302, the pad portion 202, and the detection member 204 are etched in the same process. In this embodiment, a chlorine-based etching gas is used. When etching the SiN film, which is the outermost protective film 304, the AlCu alloy film as the outermost layer of the detection member 204 and the pad portion 202 is exposed. The signal intensity of the plasma emission derived from Al starts to increase at the stage when the etching of the AlCu alloy starts. After maintaining for about 10 seconds after the signal intensity of Al starts to increase, the etching is terminated. Thereby, a state in which the AlCu alloy films of the detection member 204 and the pad portion 202 are exposed is obtained.

[0114] Since a chlorine-based gas was used for the etching, the removal of the chlorine component was performed. After the etching with the chlorine-based gas is completed, the chlorine component is completely removed by sufficiently performing resist ashing and then two-fluid cleaning.

[0115] In this embodiment, as shown in FIG. 20, as the inorganic film on the second electrode 302, 100 nm of the SiN film of the protective film 304 and the TEOS oxide film of the second insulating film 604 are removed. A configuration in which 300 nm of the second insulating film 604 and approximately 400 nm of the first insulating film 303 remain on the second electrode 302 is obtained with good reproducibility.

Example

[0116] In this embodiment, the element substrate and the liquid ejection head shown in the second embodiment were fabricated. In the following description, the description will focus on the points different from those in the above-described Example 6, and the description of the parts similar to the configuration of Example 6 will be omitted.

[0117] FIG. 21 shows a cross-sectional view of the piezoelectric element 108 and the detection member 204 of this embodiment. The cross-sectional view of the piezoelectric element 108 in FIG. 21 is a cross-sectional view at a position corresponding to XX-XX in FIG. 12.

[0118] In this embodiment, as in Example 6, the detection member 204 is located between the protective film 304 and the second insulating film 604 in a direction perpendicular to the surface of the diaphragm 109. Therefore, the detection member 204 was formed using the layer for forming the first wiring 704 that is located between the first insulating film 303 and the second insulating film 604 in the piezoelectric element 108. Also, the pad portion 202 was formed in the same manner as the detection member 204, using the layer for forming the first wiring 704. The first wiring 704, the detection member 204, and the pad portion 202 were formed using an AlCu alloy film. Also, different from Example 6, the wiring 1503 and the detection member 204 are formed using an AlCu alloy film with a TiN film having a thickness of about 20 nm formed on the surface opposite to the diaphragm 109. The exposed area of one detection member 204 was made equal to the exposed area of the pad portion 202 from the protective film 304. That is, the detection member 204 and the pad portion 202 are arranged in a layer at the same height as the first wiring 704, which is the upper wiring.

[0119] The inorganic films located on the second electrode 302, the pad portion 202, and the detection member 204 are etched in the same process. In this embodiment, a CF-based etching gas is used. When the SiN film, which is the outermost protective film 304, is etched, the TiN film as the outermost layer of the detection member 204 and the pad portion 202 is exposed. When etching TiN with a CF-based gas, the spectrum of plasma emission derived from N of TiN can be used to detect the end of etching. The start and end of the reaction are detected from the increase and decrease in the emission spectrum derived from N of TiN of the detection member 204 as shown in FIG. 10(c), and etching is terminated after waiting for about 10 seconds. As a result, the TiN film on the upper portion of the pad portion 202 is removed, and a state is obtained in which the AlCu alloy films of the detection member 204 and the pad portion 202 are exposed.

[0120] Note that the etching rate of the TiN film using a CF-based gas is slower than that of the TEOS film constituting the second insulating film 604. Therefore, by terminating the etching at the timing when the TiN film is etched and the spectrum becomes stable, in the region 203 on the second electrode 302, the layer formed on the detection member 204, that is, the inorganic films (protective film 304 and second insulating film 604) can be removed to a depth deeper than the thickness of the protective film 304. In this embodiment, as shown in FIG. 21, the 200-nm SiN film of the protective film 304 and the 250-nm TEOS oxide film of the second insulating film 604 are removed in the region 203 on the second electrode 302. A configuration in which 150 nm of the second insulating film 604 and the first insulating film 303 remain on the second electrode 302 can be obtained with good reproducibility. Thus, in this embodiment, compared with Example 6, the inorganic film on the second electrode 302 in the region 203 can be made thinner.

Example

[0121] In this embodiment, the element substrate and the liquid ejection head shown in the second embodiment were fabricated. In the following description, the description will focus on the differences from the example, and the description of the parts similar to the above-described configuration will be omitted.

[0122] The top view schematic diagram of the flow path substrate 106 in this embodiment is the same as that in Example 5 and FIG. 17. FIG. 22 shows a cross-sectional view of the piezoelectric element 108 and the detection member 204 of this embodiment. The cross-sectional view of the piezoelectric element 108 in FIG. 22 is a cross-sectional view at a position corresponding to XX-XX in FIG. 12.

[0123] Unlike in Examples 1 to 4 and Examples 6 to 7, the individual ejection elements are arranged at a density of 150 npi in the Y direction in the same manner as in Example 5. Also, in terms of dimensions, similar to Example 5, the size of the piezoelectric element 108 is approximately 500 μm in the X direction (length) and 110 μm in the Y direction (width). The diameter of the ejection port 101 is approximately 25 μm, the thickness of the nozzle 1011 communicating with the ejection port 101 is 30 μm, and the thickness of the first flow path substrate 105 is 100 μm. The size of the pressure chamber 102 is 550 μm in the X direction (length), 120 μm in the Y direction (width), and 100 μm in the Z direction (height).

[0124] In this embodiment, it is different from the multilayer wiring configurations in Examples 1 to 4 and Examples 6 to 7. The two types of wirings respectively connected to the first electrode 301 and the second electrode 302 are configured to be located in the same layer (same height) in the height direction (Z direction) without being laminated. Therefore, it is sufficient to have the first insulating film 303 that insulates the wiring 1503 and the first electrode 301, and it does not have the second insulating film 604 that was arranged between the first wiring 704 and the second wiring 702 in the height direction in Examples 1 to 4 and Examples 6 to 7.

[0125] In this embodiment, the detection member 204 is formed using the layer for forming the wiring 1503. The wiring 1503 and the detection member 204 are formed using an AlCu alloy film with a TiN film having a thickness of about 20 nm formed on the surface opposite to the diaphragm 109. Note that, unlike in Example 5, the exposed area of one detection member 204 is made equal to the exposed area from the protective film 304 of the pad portion 202.

[0126] In the etching process of removing at least a part of the inorganic films (the protective film 304 and the first insulating film 303) on the upper layer of the second electrode 302 to form the region 203, a CF-based etching gas was used. When the SiN film, which is the protective film 304, is etched, TiN is exposed on the surface layer side of the detection member 204. When etching TiN with a CF-based gas, attention is paid to the spectrum of the plasma emission derived from N of TiN. In this embodiment, as shown in FIG. 10(c), the start of the reaction of the TiN on the uppermost layer of the detection member 204 is detected, and after confirming until the N emission intensity of TiN decreases, the etching is terminated. After the etching is completed, in the pad portion 202, TiN is removed and the AlCu alloy film is exposed. The etching rate of TiN is slower than that of the TEOS oxide film. For this reason, as the inorganic film on the second electrode 302, a configuration in which 200 nm of the SiN film of the protective film 304 and 250 nm of the TEOS oxide film of the first insulating film 303 are removed and 150 nm of the TEOS oxide film of the first insulating film 303 remains can be obtained with good reproducibility.

[0127] (Other Embodiments) The present disclosure includes configurations typified by the following examples of a method for manufacturing a liquid ejection head and examples of a liquid ejection head.

[0128] <Configuration 1> A piezoelectric element including a first electrode, a piezoelectric film, and a second electrode in this order on the surface of a substrate, a wiring connected to the piezoelectric element, a terminal connected to the wiring for supplying an electrical signal for driving the piezoelectric element, and an inorganic structure disposed at a position where the piezoelectric element, the wiring, and the terminal do not overlap when viewed from a direction perpendicular to the substrate, and a method for manufacturing a liquid ejection head including an element substrate having a protective film covering at least the piezoelectric element, the wiring, and the inorganic structure, etching the protective film to form a region in which a part of the protective film overlapping the piezoelectric element is removed and an opening in which the protective film overlapping the inorganic structure is removed to expose the inorganic structure when viewed from a direction perpendicular to the surface of the substrate.

[0129] <Configuration 2> The method for manufacturing a liquid ejection head according to Configuration 1, wherein in the step of etching the protective film, the etching is terminated when the inorganic structure is exposed from the formed opening.

[0130] <Configuration 3> The method for manufacturing a liquid ejection head according to Configuration 1 or 2, wherein a film to be the wiring is patterned to form the wiring and the inorganic structure.

[0131] <Configuration 4> The etching is dry etching, The method for manufacturing a liquid ejection head according to any one of Configurations 1 to 3, wherein in the step of etching the protective film, it is detected that the inorganic structure is exposed by detecting a change in the signal intensity of the plasma emission spectrum.

[0132] <Configuration 5> The wiring includes a first wiring electrically connected to the first electrode and a second wiring electrically connected to the second electrode, The method for manufacturing a liquid ejection head according to Configuration 3, wherein the inorganic structure is formed simultaneously with at least one of the first wiring or the second wiring.

[0133] <Configuration 6> The method for manufacturing a liquid ejection head according to Configuration 5, wherein a film to be the wiring is patterned to form the first wiring, the second wiring, and the inorganic structure.

[0134] <Configuration 7> The method for manufacturing a liquid ejection head according to Configuration 5, wherein the wiring has a multilayer wiring structure, and in a direction perpendicular to the surface of the substrate, the first wiring and the second wiring are located in different layers, respectively.

[0135] <Configuration 8> The exposed area of the inorganic structure from one of the openings in the direction parallel to the surface is 0.5 times or more and 2 times or less the area of the region corresponding to one piezoelectric element. The method for manufacturing a liquid ejection head according to any one of Configurations 1 to 7.

[0136] <Configuration 9> The terminal is exposed from the protective film, The exposed area of the inorganic structure from one of the openings in the direction parallel to the surface is 0.5 times or more and 2 times or less the exposed area of the terminal. The method for manufacturing a liquid ejection head according to any one of Configurations 1 to 7.

[0137] <Configuration 10> The method for manufacturing a liquid ejection head according to any one of Configurations 1 to 9, having a plurality of the inorganic structures.

[0138] <Configuration 11> The total area of the plurality of openings in the direction parallel to the surface occupies 5% or more of the area of the element substrate. The method for manufacturing a liquid ejection head according to Configuration 10.

[0139] <Configuration 12> The inorganic structure contains any one of Au, Al, Pt, Ir, Al compounds, Ti compounds, Ta compounds, and W compounds. The method for manufacturing a liquid ejection head according to any one of Configurations 1 to 11.

[0140] <Configuration 13> An element substrate having a piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode in this order on the surface of the substrate, a wiring connected to the piezoelectric element, a terminal connected to the wiring and for supplying an electric signal for driving the piezoelectric element, and a protective film covering at least the piezoelectric element and the wiring. In the liquid ejection head having a region in which a part of the protective film overlapping the piezoelectric element in the direction perpendicular to the surface of the substrate is removed, When viewed from a direction perpendicular to the surface of the substrate, an inorganic structure is disposed at a position where the piezoelectric element, the wiring, and the terminal do not overlap, and the inorganic structure is exposed from the opening of the protective film, a liquid ejection head.

[0141] <Configuration 14> The liquid ejection head according to Configuration 13, wherein the wiring is a multilayer wiring including a first wiring electrically connected to the first electrode and a second wiring electrically connected to the second electrode.

[0142] <Configuration 15> The liquid ejection head according to Configuration 14, wherein the inorganic structure is located at the same height as at least one of the first wiring or the second wiring in a direction perpendicular to the surface of the substrate.

[0143] <Configuration 16> The liquid ejection head according to Configuration 14, wherein the detection member is located at the same height as the first electrode in a direction perpendicular to the surface of the substrate.

[0144] <Configuration 17> The liquid ejection head according to any one of Configurations 13 to 16, wherein an exposed area of the inorganic structure from one of the openings in a direction parallel to the surface is 0.5 times or more and 2 times or less the area of the region corresponding to one piezoelectric element.

[0145] <Configuration 18> The terminal is exposed from the protective film, The liquid ejection head according to any one of Configurations 13 to 16, wherein an exposed area of the inorganic structure from one of the openings in a direction parallel to the surface is 0.5 times or more and 2 times or less the exposed area of the terminal.

[0146] <Configuration 19> The liquid ejection head according to any one of Configurations 13 to 18, wherein the inorganic structure is formed of the same material as the wiring or the first electrode.

[0147] <Configuration 20> The inorganic structure contains any one of Au, Al, Pt, Ir, Al compounds, Ti compounds, Ta compounds, and W compounds, and is the liquid ejection head according to any one of Configurations 13 to 19.

Explanation of symbols

[0148] 4 Liquid ejection head 10 Element substrate 108 Piezoelectric element 109 Diaphragm 110 Piezoelectric film 202 Pad portion (terminal) 204 Detection member (inorganic structure) 301 First electrode 302 Second electrode 303 First insulating film 304 Protective film 604 Second insulating film 702 Second wiring 704 First wiring

Claims

1. A method for manufacturing a liquid ejection head including an element substrate having a piezoelectric element including a first electrode, a piezoelectric film, and a second electrode provided in this order on a surface of a substrate, a wiring connected to the piezoelectric element, a terminal connected to the wiring for supplying an electrical signal for driving the piezoelectric element, an inorganic structure disposed at a position where the piezoelectric element, the wiring, and the terminal do not overlap when viewed from a direction perpendicular to the substrate, and a protective film covering at least the piezoelectric element, the wiring, and the inorganic structure, the method comprising: etching the protective film to form a region where a part of the protective film overlapping the piezoelectric element is removed and an opening where the protective film overlapping the inorganic structure is removed to expose the inorganic structure when viewed from a direction perpendicular to the surface of the substrate.

2. The method for manufacturing a liquid ejection head according to claim 1, wherein in the step of etching the protective film, the etching is terminated when the inorganic structure is exposed from the formed opening.

3. The method for manufacturing a liquid ejection head according to claim 1, wherein a film to be the wiring is patterned to form the wiring and the inorganic structure.

4. The etching is dry etching, and in the step of etching the protective film, it is detected that the inorganic structure is exposed by detecting a change in signal intensity of a plasma emission spectrum. The method for manufacturing a liquid ejection head according to claim 1.

5. The wiring includes a first wiring electrically connected to the first electrode and a second wiring electrically connected to the second electrode, and the method for manufacturing a liquid ejection head according to claim 3, wherein the inorganic structure is formed simultaneously with at least one of the first wiring and the second wiring.

6. The method for manufacturing a liquid ejection head according to claim 5, wherein a film to be the wiring is patterned to form the first wiring, the second wiring, and the inorganic structure.

7. The method for manufacturing a liquid ejection head according to claim 5, wherein the wiring has a multilayer wiring structure, and the first wiring and the second wiring are located in different layers in a direction perpendicular to the surface of the substrate.

8. The method for manufacturing a liquid ejection head according to claim 1, wherein an exposed area of the inorganic structure from one of the openings in a direction parallel to the surface is 0.5 times or more and 2 times or less the area of the region corresponding to one piezoelectric element.

9. The terminal is exposed from the protective film, The exposed area of the inorganic structure from one of the openings in the direction parallel to the surface is 0.5 times or more and 2 times or less the exposed area of the terminal. The method for manufacturing a liquid ejection head according to claim 1.

10. The method for manufacturing a liquid ejection head according to claim 1, having a plurality of the inorganic structures.

11. The total area of the plurality of openings in the direction parallel to the surface occupies 5% or more of the area of the element substrate. The method for manufacturing a liquid ejection head according to claim 10.

12. The inorganic structure contains any one of Au, Al, Pt, Ir, Al compounds, Ti compounds, Ta compounds, and W compounds. The method for manufacturing a liquid ejection head according to claim 1.

13. On the surface of the substrate, a piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode in this order, a wiring connected to the piezoelectric element, and a terminal connected to the wiring for supplying an electric signal for driving the piezoelectric element, and an element substrate having a protective film covering at least the piezoelectric element and the wiring are provided. In a liquid ejection head in which a part of the protective film that overlaps the piezoelectric element in a direction perpendicular to the surface of the substrate is removed from the protective film. When viewed from a direction perpendicular to the surface of the substrate, an inorganic structure is disposed at a position where the piezoelectric element, the wiring, and the terminal do not overlap, and the inorganic structure is exposed from an opening of the protective film. A liquid ejection head.

14. The wiring is a multilayer wiring including a first wiring electrically connected to the first electrode and a second wiring electrically connected to the second electrode. The liquid ejection head according to claim 13.

15. The inorganic structure is located at the same height as at least one of the first wiring or the second wiring in a direction perpendicular to the surface of the substrate. The liquid ejection head according to claim 14.

16. The detection member is located at the same height as the first electrode in a direction perpendicular to the surface of the substrate. The liquid ejection head according to claim 14.

17. The exposed area of the inorganic structure from one of the openings in the direction parallel to the surface is 0.5 times or more and 2 times or less the area of the region corresponding to one piezoelectric element. The liquid ejection head according to claim 13.

18. The terminal is exposed from the protective film, The exposed area of the inorganic structure from one of the openings in the direction parallel to the surface is 0.5 times or more and 2 times or less the exposed area of the terminal. The liquid ejection head according to claim 13.

19. The inorganic structure is formed of the same material as the wiring or the first electrode. The liquid ejection head according to claim 13.

20. The inorganic structure contains any one of Au, Al, Pt, Ir, Al compounds, Ti compounds, Ta compounds, and W compounds. The liquid ejection head according to claim 19, characterized in that.

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