Piezoelectric laminate, piezoelectric element, and method for manufacturing piezoelectric laminate

Abstract

The present invention has: a substrate (1); a lower electrode film (2) provided on the substrate; a piezoelectric film (3) which is provided on the lower electrode film and has a plane area smaller than the plane area of the lower electrode film; an upper electrode film (4) provided on the piezoelectric film; and an insulating film (5) which is provided from the upper electrode film to the lower electrode film so as to cover at least a part of the side surface of the piezoelectric film, wherein a slope section (9a), which fills the step difference between the upper surface of the upper electrode film and the upper surface of the lower electrode film, is formed in the insulating film, and the slope section is formed in a shape that mitigates the step difference.

Description

[Technical Field]

[0001] The present disclosure relates to a piezoelectric stack, a piezoelectric element, and a method for manufacturing a piezoelectric stack. [Background technology]

[0002] Piezoelectric materials are widely used in functional electronic components such as sensors and actuators. Lead-based materials, especially those with the composition formula Pb(Zr 1-x Ti x PZT-based ferroelectrics represented by the formula (III) and (IV) are widely used. PZT-based piezoelectric materials contain lead, which is undesirable from the standpoint of pollution prevention. Therefore, piezoelectric materials containing potassium, sodium, niobium, and oxygen have been proposed as lead-free piezoelectric materials, and laminates (hereinafter referred to as piezoelectric laminates) having piezoelectric films formed using such piezoelectric materials have been proposed (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-184513 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-159807 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to improve the reliability of a piezoelectric element or a piezoelectric device module fabricated using a piezoelectric laminate. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, A substrate; a lower electrode film provided on the substrate; a piezoelectric film provided on the lower electrode film and having a plane area smaller than the plane area of ​​the lower electrode film; an upper electrode film provided on the piezoelectric film; an insulating film provided from the upper electrode film to the lower electrode film so as to cover at least a part of a side surface of the piezoelectric film, a slope portion is formed in the insulating film to fill a step between an upper surface of the upper electrode film and an upper surface of the lower electrode film; The sloped portion is formed in a shape that reduces the step. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to improve the reliability of a piezoelectric element or a piezoelectric device module fabricated using a piezoelectric laminate. [Brief explanation of the drawings]

[0007] [Figure 1] 1(a) is a diagram showing an example of a cross-sectional structure of a piezoelectric laminate according to one embodiment of the present disclosure, and FIG. 1(b) is a diagram showing an example of a top view of the piezoelectric laminate shown in FIG. 1(a). [Figure 2] 10A and 10B are diagrams illustrating modified examples of the cross-sectional structure of the piezoelectric laminate according to an embodiment of the present disclosure. [Figure 3] 1A and 1B are diagrams illustrating the state of the side surfaces of the piezoelectric film in a piezoelectric laminate according to one embodiment of the present disclosure, in which (a) is a diagram showing an example in which the side surfaces of the piezoelectric film are perpendicular to the upper surface of the lower electrode film, (b) is a diagram showing an example in which the side surfaces of the piezoelectric film are inclined surfaces inclined at a predetermined angle to the upper surface of the lower electrode film, (c) is a diagram showing another example in which the side surfaces of the piezoelectric film are inclined surfaces inclined at a predetermined angle to the upper surface of the lower electrode film, and (d) is a diagram showing an example in which at least the surface of the side surfaces of the piezoelectric film facing the lower electrode film is an inclined surface inclined at a predetermined angle, and the surfaces excluding at least the surface facing the lower electrode film are perpendicular to the upper surface of the lower electrode film. [Figure 4]1(a) and 1(b) are explanatory diagrams illustrating the inclination angle θ2 of the first slope portion in the piezoelectric laminate according to one embodiment of the present disclosure, where FIG. 1(a) illustrates an example in which the inclination angle θ2 is smaller than that shown in FIG. 1(a), and FIG. 1(b) illustrates an example in which the inclination angle θ2 is larger than that shown in FIG. [Figure 5] 1 is a diagram illustrating an example of a schematic configuration of a piezoelectric device module according to an aspect of the present disclosure. [Figure 6] 6(a) is a diagram showing an example of a cross-sectional structure of a piezoelectric laminate according to one embodiment of the present disclosure, and FIG. 6(b) is an SEM image of the area indicated by dotted line A in FIG. 6(a). [Figure 7] 7(a) is a diagram showing an example of the cross-sectional structure of a piezoelectric laminate according to one embodiment of the present disclosure; (b) is an SEM image of the area indicated by dotted line B in FIG. 7(a); (c) is an SEM image of an enlarged area indicated by dotted line C in FIG. 7(b); (d) is an SEM image of an enlarged area indicated by dotted line D in FIG. 7(b); and (e) is an SEM image of an enlarged area indicated by dotted line E in FIG. 7(b). [Figure 8] 10A and 10B are diagrams illustrating modified examples of the cross-sectional structure of the piezoelectric laminate according to an embodiment of the present disclosure. [Figure 9] 10A and 10B are diagrams illustrating another modified example of the cross-sectional structure of the piezoelectric laminate according to the embodiment of the present disclosure. [Figure 10] 10(a) is a diagram showing another modified example of the cross-sectional structure of the piezoelectric laminate according to one embodiment of the present disclosure, and FIG. 10(b) is a diagram showing an example of a top view of the piezoelectric laminate shown in FIG. 10(a). [Figure 11] FIG. 1 is a diagram showing an example of a cross-sectional structure of a conventional piezoelectric laminate. [Figure 12] FIG. 10 is a diagram showing a comparative example of the cross-sectional structure of the piezoelectric laminate according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0008] <One aspect of the present disclosure> Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings.

[0009] (1) Structure of the piezoelectric laminate 1(a) and 1(b), a laminate 10 having a piezoelectric film according to this embodiment (hereinafter also referred to as piezoelectric laminate 10) includes a substrate 1, a lower electrode film 2 provided on the substrate 1, a piezoelectric film (piezoelectric thin film) 3 provided on the lower electrode film 2, an upper electrode film 4 provided on the piezoelectric film 3, and an insulating film 5. In this embodiment, an example will be described in which one laminate structure (a structure formed by laminating at least the lower electrode film 2, the piezoelectric film 3, the upper electrode film 4, and the insulating film 5) is provided on one substrate 1.

[0010] The substrate 1 is a substrate having a surface such as a thermal oxide film or a CVD (Chemical Vapor Deposition) oxide film. A single-crystal silicon (Si) substrate 1a on which a surface oxide film (SiO2 film) 1b is formed, i.e., a Si substrate having a surface oxide film, can be preferably used. Alternatively, as shown in FIG. 2, a Si substrate 1a having an insulating film 1d formed on its surface from an insulating material other than SiO2 can also be used. Alternatively, a Si substrate 1a with an exposed Si(100) or Si(111) surface, i.e., a Si substrate without a surface oxide film 1b or insulating film 1d, can also be used. Alternatively, a silicon-on-insulator (SOI) substrate, a quartz glass (SiO2) substrate, a gallium arsenide (GaAs) substrate, a sapphire (Al2O3) substrate, or a metal substrate made of a metal material such as stainless steel (SUS) can also be used. The thickness of the single-crystal Si substrate 1a can be, for example, 300 μm to 1000 μm, and the thickness of the surface oxide film 1b can be, for example, 1 nm to 4000 nm.

[0011] The lower electrode film 2 can be formed using, for example, platinum (Pt). The lower electrode film 2 is a polycrystalline film or a single-crystalline film (hereinafter, also referred to as a Pt film). The crystals constituting the Pt film are preferably crystals whose (111) plane is parallel to the main surface of the substrate 1 (including crystals whose (111) plane is inclined at an angle of ±5° or less with respect to the main surface of the substrate 1). In other words, it is preferable that the crystals constituting the Pt film are preferentially oriented in the (111) plane direction. The crystals constituting the Pt film are preferentially oriented in the (111) plane direction when the X-ray diffraction pattern obtained by X-ray diffraction (XRD) measurement has the highest peak in the (111) plane. In other words, it is preferable that the upper surface of the lower electrode film 2 (the surface underlying the piezoelectric film 3) is mainly composed of the Pt (111) plane. The lower electrode film 2 can be formed by a method such as sputtering or vapor deposition. The lower electrode film 2 can be formed using various metals other than Pt, such as gold (Au), ruthenium (Ru), or iridium (Ir), alloys mainly composed of these metals, or metal oxides such as strontium ruthenate (SrRuO3, abbreviated as SRO) or lanthanum nickelate (LaNiO3, abbreviated as LNO). The lower electrode film 2 can be a single-layer film formed using the above-mentioned metals or metal oxides. The lower electrode film 2 may be a laminate of a Pt film and a film of SRO provided thereon, or a laminate of a Pt film and a film of LNO provided thereon. Note that, to improve adhesion between the substrate 1 and the lower electrode film 2, an adhesion layer 6 mainly composed of, for example, titanium (Ti), tantalum (Ta), titanium oxide (TiO2), nickel (Ni), ruthenium oxide (RuO2), iridium oxide (IrO2), or zinc oxide (ZnO) may be provided. The adhesion layer 6 can be formed by a method such as sputtering, vapor deposition, etc. The thickness of the lower electrode film 2 (when the lower electrode film 2 is a laminate, the total thickness of each layer) can be, for example, 100 nm or more and 400 nm or less, and the thickness of the adhesion layer 6 can be, for example, 1 nm or more and 200 nm or less.

[0012] The piezoelectric film 3 is made of a material having etching anisotropy. The piezoelectric film 3 is, for example, an alkali niobium oxide film containing potassium (K), sodium (Na), niobium (Nb), and oxygen (O). The piezoelectric film 3 can be formed using potassium sodium niobate (KNN). The piezoelectric film 3 is a KNN polycrystalline film (hereinafter also referred to as KNN film 3). The crystal structure of KNN is a perovskite structure. In other words, the KNN film 3 has a perovskite structure. The KNN film 3 can be formed using a method such as sputtering, PLD (Pulsed Laser Deposition), or sol-gel method. The thickness of the KNN film 3 can be, for example, For example, the thickness can be set to 0.5 μm or more and 5 μm or less.

[0013] The KNN film 3 may contain elements other than K, Na, Nb, and O, such as copper (Cu), manganese (Mn), lithium (Li), tantalum (Ta), and antimony (Sb), within a range of, for example, 5 at % or less (when multiple types of the above elements are added, the total concentration is 5 at % or less).

[0014] The crystals constituting the KNN film 3 are preferably preferentially oriented in the (001) plane direction with respect to the main surface of the substrate 1 (Si substrate 1a when the substrate 1 is, for example, a Si substrate 1a having a surface oxide film 1b or an insulating film 1d, etc.). That is, the upper surface of the KNN film 3 (the surface serving as the base of the upper electrode film 4) is preferably mainly composed of the KNN(001) plane. For example, by directly depositing the KNN film 3 on a Pt film (lower electrode film 2) whose upper surface is mainly composed of the Pt(111) plane, it is possible to easily obtain a KNN film 3 whose upper surface is mainly composed of the KNN(001) plane.

[0015] In this specification, the crystals constituting the KNN film 3 being oriented in the (001) plane direction means that the (001) plane of the crystals constituting the KNN film 3 is parallel to the main surface of the substrate 1. The (001) plane of the crystals constituting the KNN film 3 being parallel to the main surface of the substrate 1 includes not only the case where the (001) plane is completely parallel to the main surface of the substrate 1, but also the case where the (001) plane is inclined at an angle of ±5° or less, preferably ±3° or less, relative to the main surface of the substrate 1. Furthermore, the crystals constituting the KNN film 3 being preferentially oriented in the (001) plane direction means that most of the crystals have their (001) plane parallel to the main surface of the substrate 1. For example, it is preferable that 80% or more of the crystals constituting the KNN film 3 are oriented in the (001) plane direction relative to the main surface of the substrate 1. That is, the orientation rate of the crystals constituting the KNN film 3 in the (001) plane direction is, for example, preferably 80% or more, and more preferably 90% or more. The "orientation rate" in this specification is a value calculated by the following equation (1) based on the peak intensity of the X-ray diffraction pattern (2θ / θ) obtained by performing XRD measurement on the KNN film 3.

[0016] (Number 1) Orientation rate (%) = {(001) plane diffraction peak intensity / ((001) plane diffraction peak intensity + (110) plane diffraction peak intensity)} × 100

[0017] The "(001) plane diffraction peak" in the above (Equation 1) and in this specification refers to a diffraction peak resulting from crystals oriented in the (001) plane direction (i.e., crystals whose (001) plane is parallel to the main surface of the substrate 1) among the crystals constituting the KNN film 3 in the X-ray diffraction pattern obtained by XRD measurement of the KNN film 3, and is a peak appearing within a 2θ range of 20° to 23°. The "(110) plane diffraction peak" in the above (Equation 1) and in this specification refers to a diffraction peak resulting from crystals oriented in the (110) plane direction (i.e., crystals whose (110) plane is parallel to the main surface of the substrate 1) among the crystals constituting the KNN film 3 in the X-ray diffraction pattern obtained by XRD measurement of the KNN film 3, and is a peak appearing within a 2θ range of 30° to 33°.

[0018] It is preferable that more than half of the crystals constituting the KNN film 3 have a columnar structure. The boundaries between the crystals constituting the KNN film 3, i.e., the grain boundaries present in the KNN film 3, preferably run through the thickness direction of the KNN film 3. For example, it is preferable that the number of grain boundaries running through the thickness direction of the KNN film 3 is greater than the number of grain boundaries that do not run through the thickness direction of the KNN film 3.

[0019] By subjecting the KNN film 3 to an etching process, the plane area of ​​the KNN film 3 becomes smaller than the plane area of ​​the lower electrode film 2. The KNN film 3 configured as described above exhibits a predetermined etching anisotropy when subjected to an etching process. For example, when the KNN film 3 is wet-etched through an etching mask formed on the KNN film 3, the etching rate in the film thickness direction (growth direction) tends to be greater than the etching rate in the lateral direction (direction perpendicular to the growth direction).

[0020] Due to the influence of the etching anisotropy described above, the side surface of the KNN film 3 exposed by etching tends to be processed so that the side surface is perpendicular to the upper surface of the lower electrode film 2, or at least a portion of the side surface of the KNN film 3 is inclined relative to the upper surface of the lower electrode film 2 at an angle of 75° to less than 90°, preferably 85° to less than 90°, or at least a portion of the side surface of the KNN film 3 is inclined relative to the upper surface of the lower electrode film 2 at an angle of more than 90° to less than 105°, preferably more than 90° to less than 100°. That is, as shown in FIG. 3(a), the angle θ1 (hereinafter referred to as "angle θ1") between the side surface of the KNN film 3 and the upper surface of the lower electrode film 2 can be, for example, 90°. Alternatively, as shown in FIG. 3(b), the angle θ1 can be, for example, 75° to less than 90°, preferably 85° to less than 90°. 3(c), the angle θ1 can be, for example, greater than 90° and less than 105°, and preferably greater than 90° and less than 100°. Thus, the angle θ1 can be, for example, greater than 75° and less than 105°.

[0021] The magnitude of the angle θ1 can affect the characteristics of the piezoelectric device module 30, which will be described later. If the angle θ1 is too large, the area of ​​the upper surface of the KNN film 3 is reduced, which may degrade the characteristics of the piezoelectric device module 30 fabricated by processing the piezoelectric laminate 10. On the other hand, if the angle θ1 is too small, the area of ​​the lower surface of the KNN film 3 (the surface opposite to the upper surface of the KNN film 3) is reduced, which may degrade the characteristics of the piezoelectric device module 30 as described above. From the viewpoint of avoiding degradation of the characteristics of the piezoelectric device module 30, the angle θ1 is preferably within a range of, for example, 75° to 105°, and more preferably within a range of 85° to 100°, as described above.

[0022] The side surfaces of the KNN film 3 exposed by etching may be processed so that at least a portion of the side surfaces is an inclined surface inclined at a predetermined angle with respect to the upper surface of the lower electrode film 2. For example, the side surfaces of the KNN film 3 may be processed so that at least the surface on the lower electrode film 2 side is an inclined surface inclined at an angle of 75° or more and less than 90° with respect to the upper surface of the lower electrode film 2, preferably at an angle of 85° or more and less than 90°.

[0023] Furthermore, the side surfaces of the KNN film 3 exposed by etching may be processed so that at least a part of the side surfaces is perpendicular to the upper surface of the lower electrode film 2. For example, the side surfaces of the KNN film 3 may be processed so that at least the surfaces excluding the surface on the lower electrode film 2 side (at least the surface on the upper electrode film 4 side) are perpendicular to the upper surface of the lower electrode film 2.

[0024] For example, as shown in FIG. 3(d), the side surfaces of the KNN film 3 exposed by etching may be processed so that at least the surface facing the lower electrode film 2 is an inclined surface inclined at an angle of 75° or more and less than 90° with respect to the upper surface of the lower electrode film 2, and at least the surface facing the upper electrode film 4 is a surface perpendicular to the upper surface of the lower electrode film 2.

[0025] The upper electrode film 4 can be formed using various metals such as Pt, Au, aluminum (Al), and Cu, or alloys thereof. The upper electrode film 4 can be formed using techniques such as sputtering, vapor deposition, plating, and metal paste deposition. Unlike the lower electrode film 2, the upper electrode film 4 does not significantly affect the crystalline structure of the KNN film 3. Therefore, the material, crystalline structure, and film formation technique of the upper electrode film 4 are not particularly limited. Note that, to improve adhesion between the KNN film 3 and the upper electrode film 4, an adhesion layer containing, for example, titanium (Ti), Ta, titanium oxide (TiO2), nickel (Ni), ruthenium oxide (RuO2), iridium oxide (IrO2), or the like, as a main component, may be provided. The thickness of the upper electrode film 4 can be, for example, 100 nm to 5000 nm. If an adhesion layer is provided, the thickness of the adhesion layer can be, for example, 1 nm to 200 nm.

[0026] The insulating film 5 is provided from the upper electrode film 4 to the lower electrode film 2 so as to cover part of the side surface of the KNN film 3. Details of the insulating film 5 will be described later.

[0027] As shown in FIG. 1 , an adhesion layer 7 may be provided between the insulating film 5 and the base of the insulating film 5 to enhance adhesion between the insulating film 5 and the base. That is, the adhesion layer 7 may be provided from the upper electrode film 4 to the lower electrode film 2 so as to cover a portion of the side surface of the KNN film 3, and the insulating film 5 may be provided on the adhesion layer 7. In this specification, the "base of the insulating film 5" refers not only to the side surface of the KNN film 3 but also to the upper surface of the lower electrode film 2, the upper surface of the upper electrode film 4, the side surface of the upper electrode film 4, or the like, which serves as the base for the insulating film 5. The adhesion layer 7 may be provided using an insulating metal oxide (insulating material). The adhesion layer 7 may be provided using aluminum oxide (Al2O3), tantalum oxide (Ta2O5), or the like. The adhesion layer 7 may be provided using techniques such as ALD, sputtering, or vapor deposition. The adhesion layer 7 does not significantly affect the crystalline structure of the KNN film 3. Therefore, the crystalline structure and deposition technique of the adhesion layer 7 are not particularly limited.

[0028] Metal wiring 8 having a predetermined pattern and connected to the upper electrode film 4 is provided on the insulating film 5. The metal wiring 8 is provided so as not to be connected to (contact with) the lower electrode film 2. The metal wiring 8 can be provided using various metals such as Pt, Au, aluminum (Al), Cu, etc., or alloys of these. The metal wiring 8 can be provided using techniques such as sputtering, vapor deposition, plating, and metal paste.

[0029] The thickness of the metal wiring 8 can be the same as the smallest thickness t1 of the insulating film 5, which is defined as the shortest distance from a point on the upper surface of the lower electrode film 2 or the upper surface of the upper electrode film 4 (or on the upper surface of the adhesive layer 7 if provided) to the surface of the insulating film 5. Preferably, the thickness of the metal wiring 8 can be thinner than the smallest thickness t1 of the insulating film 5. More preferably, the thickness of the metal wiring 8 can be, for example, 1 / 20 to 1 / 2, more preferably 1 / 20 to 1 / 4, of the thickness of the KNN film 3. In this embodiment, even if the thickness of the metal wiring 8 is made thinner (than conventionally), breakage of the metal wiring 8 can be avoided because the insulating film 5 has slope portions 9a and 9b, as described below.

[0030] In order to improve adhesion between the insulating film 5 and the metal wiring 8, an adhesion layer containing, for example, Ti, Ta, TiO2, Ni, RuO2, IrO2, or the like as a main component may be provided between the insulating film 5 and the metal wiring 8. The adhesion layer can be provided by a method such as sputtering or vapor deposition. When an adhesion layer is provided, the thickness of the adhesion layer can be, for example, 1 nm or more and 200 nm or less.

[0031] (2) Insulating film structure The insulating film 5 of the piezoelectric laminate 10 will be described in detail below with reference to FIGS. 1, 4(a), and 4(b). For illustrative purposes, FIG. 1 only shows an example of the thickness t2 of the insulating film 5 in the slope portion 9a (described later) and the thickness t3 of the insulating film 5 in the slope portion 9b (described later). However, the thickness t2 varies depending on the selected position of a point on the side surface of the KNN film 3, and the thickness t3 varies depending on the selected position of a point on the surface of the slope portion 9b (described later). For clarity, the adhesive layer 7 is omitted from FIGS. 4(a) and 4(b).

[0032] As shown in FIG. 1, the insulating film 5 is provided from the upper electrode film 4 to the lower electrode film 2 so as to cover part of the side surface of the KNN film 3, preferably from the upper surface of the upper electrode film 4 to the upper surface of the lower electrode film 2.

[0033] The insulating film 5 has a slope portion 9a formed therein as a first slope portion that fills the step between the upper surface of the upper electrode film 4 and the upper surface of the lower electrode film 2. The slope portion 9a is formed in a shape that reduces the step between the upper surface of the upper electrode film 4 and the upper surface of the lower electrode film 2. For example, the slope portion 9a is formed so that its surface is non-parallel to the side surface of the KNN film 3. Furthermore, for example, the slope portion 9a is formed so that the thickness t2 of the insulating film 5, which is defined as the shortest distance from a point on the side surface of the KNN film 3 to the surface of the slope portion 9a in a direction parallel to the upper surface of the substrate 1 in a vertical cross section of the slope portion 9a including the piezoelectric stack 10, gradually increases from the upper electrode film 4 side toward the lower electrode film 2 side. By forming such a slope portion 9a in the insulating film 5, i.e., by having the insulating film 5 have the slope portion 9a, it is possible to prevent disconnection of the metal wiring 8.

[0034] The surface of the slope portion 9a preferably includes a curved surface, which can reliably prevent disconnection of the metal wiring 8. It is more preferable that the surface of the slope portion 9a does not have any steps, which can more reliably prevent disconnection of the metal wiring 8.

[0035] As shown in FIG. 4(a), the smaller the inclination angle θ2 (hereinafter referred to as angle θ2) of the slope portion 9a, i.e., the more acute the angle θ2, the less likely the metal wiring 8 is to break. However, if the angle θ2 is too small, it becomes difficult to reduce the plane area of ​​the piezoelectric device module 30 (described later), and miniaturization of the piezoelectric device module 30 may not be achieved. On the other hand, as shown in FIG. 4(b), the larger the angle θ2, i.e., the closer the angle θ2 is to 90°, the more likely the metal wiring 8 is to break. It is preferable that the angle θ2 be set to an angle that achieves a good balance between miniaturizing the piezoelectric device module 30 and preventing the metal wiring 8 from breaking.

[0036] 1, the insulating film 5 located on the upper surface of the upper electrode film 4 has a slope portion 9b formed therein as a second slope portion so as to prevent a step from occurring between the upper surface of the insulating film 5 and (the upper surface of) the upper electrode film 4. The slope portion 9b is formed in a shape that prevents a step from occurring between the upper surface of the insulating film 5 and the upper electrode film 4. For example, the slope portion 9b is formed so that its surface is non-parallel to a direction perpendicular to the upper surface of the upper electrode film 4. For example, the slope portion 9b is formed so that the thickness t3 of the insulating film 5, which is defined as the shortest distance from a point on the surface of the slope portion 9b to the upper surface of the upper electrode film 4, gradually becomes thinner from the outer side toward the inner side of the upper surface of the upper electrode film 4. By forming such a slope portion 9b in the insulating film 5, it is possible to reliably prevent disconnection of the metal wiring 8.

[0037] The surface of the slope portion 9b preferably includes a curved surface, which can more reliably prevent disconnection of the metal wiring 8. It is more preferable that the surface of the slope portion 9b does not have any steps, which can more reliably prevent disconnection of the metal wiring 8.

[0038] As shown in FIG. 4(a), the smaller the inclination angle θ3 (hereinafter referred to as "angle θ3") of the slope portion 9b, i.e., the more acute the angle θ3, the less likely the metal wiring 8 is to break. However, if the angle θ3 is too small, it becomes difficult to reduce the plane area of ​​the upper electrode film 4, and it may not be possible to achieve the miniaturization of the piezoelectric device module 30 described below. On the other hand, as shown in FIG. 4(b), the larger the angle θ3, i.e., the closer the angle θ3 is to 90°, the more likely the metal wiring 8 is to break. It is preferable that the angle θ3 be set to an angle that can achieve a good balance between miniaturization of the piezoelectric device module 30 and preventing breakage of the metal wiring 8.

[0039] 1, the insulating film 5 has a layered structure in which a first layer 5a and a second layer 5b are stacked in this order from the lower electrode film 2 side. As will be described later, the first layer 5a and the second layer 5b are fabricated by different methods, and even if they are made of the same material, they have subtle differences in various physical properties, such as density, impurity concentration, refractive index, and step coverage. An interface exists in the insulating film 5 between the first layer 5a and the second layer 5b as a trace of these differences.

[0040] The first layer 5a is provided with a uniform thickness from (the upper surface of) the upper electrode film 4 to (the upper surface of) the lower electrode film 2 so as to cover part of the side surface of the KNN film 3.

[0041] The first layer 5a is made of an insulating material, for example, silicon oxide (silicon oxide) such as silicon dioxide (SiO2). The first layer 5a can be formed, for example, by depositing a vapor phase precursor. The vapor phase precursor can be a silane-based gas, such as a silicon hydride gas such as disilane (DS) gas or a halosilane gas such as dichlorosilane (DCS), or an oxidizing gas such as oxygen gas. Alternatively, an alkoxysilane-based gas, such as tetraethoxysilane (TEOS) gas, can be used alone as the vapor phase precursor. The first layer 5a can be formed using a vapor phase growth method such as CVD, ALD, sputtering, or vacuum deposition.

[0042] The first layer 5a formed by depositing the vapor phase raw material has a higher thermal conductivity than the second layer 5b described later. The insulating film 5 has such a first layer 5a that the adhesion between the insulating film 5 and the base of the insulating film 5 (or the adhesion layer 7 if provided) is improved, and peeling of the insulating film 5 can be suppressed.

[0043] From the viewpoint of reliably suppressing peeling of the insulating film 5, the thickness t4 of the first layer 5a is preferably as thick as possible. However, as described above, the first layer 5a has the characteristics of high step coverage and excellent in-plane thickness uniformity. Therefore, even if the first layer 5a is formed thick, it is difficult (and impractical) to provide the above-mentioned slope portions 9a and 9b (particularly the slope portion 9a) in the insulating film 5. Furthermore, because the first layer 5a has a high density, if it is grown thick, cracks are likely to occur due to the internal stress, etc. For these reasons, the thickness t4 of the first layer 5a is preferably set to a thickness that can reliably suppress peeling of the insulating film 5 and the minimum thickness necessary to suppress cracking in the first layer 5a. The thickness t4 of the first layer 5a can be, for example, 200 nm to 700 nm, preferably 300 nm to 600 nm, and more preferably 500 nm to 600 nm. In this specification, the thickness t4 of the first layer 5a is the thickness (thinnest thickness) defined as the distance from a point on the lower surface of the first layer 5a to the surface (upper surface) of the first layer 5a in a direction perpendicular to the upper surface of the substrate 1 in a region that is not located above the upper electrode film 4 and is not located below the slope portion 9a.

[0044] The second layer 5b is provided on the first layer 5a and forms the above-mentioned slope portions 9a and 9b.

[0045] Like the first layer 5a, the second layer 5b is made of an insulating material, such as silicon oxide such as SiO2. Forming the second layer 5b using the same material as the first layer 5a is preferable because it enhances adhesion between the second layer 5b and the first layer 5a and prevents peeling of the second layer 5b. The second layer 5b can be formed, for example, by depositing a liquid-phase precursor. The second layer 5b can be formed, for example, by applying a liquid-phase precursor obtained by dissolving a methylsiloxane-based precursor in a solvent onto the first layer 5a using, for example, a spin coating method, and then solidifying (e.g., drying or baking) the liquid-phase precursor applied to the first layer 5a. That is, the second layer 5b can be formed by the so-called spin-on-glass (SOG) method.

[0046] The second layer 5b formed by depositing a liquid-phase precursor has lower in-plane thickness uniformity than the first layer 5a. This allows the liquid-phase precursor to accumulate in the stepped portions of the underlying layer, which facilitates the formation of the sloped portions 9a, 9b. The insulating film 5 having such a second layer 5b facilitates the formation of the sloped portions 9a, 9b in the insulating film 5 and also facilitates the adjustment of the angles θ2 and θ3. The thickness t5 of the second layer 5b is preferably set to a value that allows the formation of the sloped portions 9a, 9b in the second layer 5b. In this specification, the thickness t5 of the second layer 5b refers to the minimum thickness, defined as the distance from a point on the lower surface of the second layer 5b to the surface of the second layer 5b in a direction perpendicular to the upper surface of the substrate 1, in a region not located above the upper electrode film 4 and other than the region where the sloped portion 9a is formed. If the thickness t5 of the second layer 5b is too thin, it may be impossible to form the slope portions 9a, 9b, especially the slope portion 9a, in the second layer 5b. The thickness t5 of the second layer 5b can be appropriately set depending on the size (height) of the step where the slope portions 9a, 9b are provided, i.e., the film thickness of the KNN film 3. For example, the thickness t5 of the second layer 5b can be made thicker than the thickness t4 of the first layer 5a.

[0047] (3) Piezoelectric device module configuration FIG. 5 shows a schematic diagram of a device module 30 (hereinafter also referred to as piezoelectric device module 30) having a KNN film 3 in this embodiment. By molding the above-described piezoelectric laminate 10 into a predetermined shape, an element (device) 20 (element 20 having a KNN film 3, hereinafter also referred to as piezoelectric element 20) as shown in FIG. 5 is obtained. The piezoelectric device module 30 includes at least the piezoelectric element 20 and a voltage application unit 11a or a voltage detection unit 11b connected to the piezoelectric element 20. The voltage application unit 11a is a means for applying a voltage between the lower electrode film 2 and the upper electrode film 4 (between the electrodes), and the voltage detection unit 11b is a means for detecting a voltage generated between the lower electrode film 2 and the upper electrode film 4 (between the electrodes). Various known means can be used for the voltage application unit 11a and the voltage detection unit 11b.

[0048] By connecting the voltage application unit 11a between the lower electrode film 2 and the upper electrode film 4 of the piezoelectric element 20, the piezoelectric device module 30 can function as an actuator. By applying a voltage between the lower electrode film 2 and the upper electrode film 4 by the voltage application unit 11a, the KNN film 3 can be deformed. This deformation action can actuate various members connected to the piezoelectric device module 30. In this case, examples of applications of the piezoelectric device module 30 include a head for an inkjet printer, a MEMS mirror for a scanner, and a vibrator for an ultrasonic generator.

[0049] By connecting the voltage detection unit 11b between the lower electrode film 2 and the upper electrode film 4 of the piezoelectric element 20, the piezoelectric device module 30 can function as a sensor. When the KNN film 3 deforms in response to a change in some physical quantity, a voltage is generated between the lower electrode film 2 and the upper electrode film 4 due to the deformation. By detecting this voltage with the voltage detection unit 11b, it is possible to measure the magnitude of the physical quantity applied to the KNN film 3. In this case, the piezoelectric device module 30 can be used, for example, as an angular velocity sensor, an ultrasonic sensor, a pressure sensor, an acceleration sensor, etc.

[0050] (4) Methods for manufacturing piezoelectric laminates, piezoelectric elements, and piezoelectric device modules A method for manufacturing the above-mentioned piezoelectric stack 10, piezoelectric element 20, and piezoelectric device module 30 will now be described.

[0051] (Deposition of adhesion layer and bottom electrode film) First, a substrate 1 is prepared, and an adhesion layer 6 (Ti layer) and a lower electrode film 2 (Pt film) are formed in this order by, for example, a sputtering method on one of the main surfaces of the substrate 1. Alternatively, a substrate 1 may be prepared on which an adhesion layer 6 and a lower electrode film 2 have already been formed on one of the main surfaces.

[0052] The conditions for providing the adhesive layer 6 include the following, for example. Temperature (substrate temperature): 100°C or higher and 500°C or lower, preferably 200°C or higher and 400°C or lower Discharge power: 1000 W or more and 1500 W or less, preferably 1100 W or more and 1300 W or less Atmosphere: Argon (Ar) gas atmosphere Atmospheric pressure: 0.1 Pa or more and 0.5 Pa or less, preferably 0.2 Pa or more and 0.4 Pa or less. Time: 30 seconds or more and 3 minutes or less, preferably 45 seconds or more and 2 minutes or less.

[0053] The conditions for depositing the lower electrode film 2 are exemplified as follows. Temperature (substrate temperature): 100°C or higher and 500°C or lower, preferably 200°C or higher and 400°C or lower Discharge power: 1000 W or more and 1500 W or less, preferably 1100 W or more and 1300 W or less Atmosphere: Ar gas atmosphere Atmospheric pressure: 0.1 Pa or more and 0.5 Pa or less, preferably 0.2 Pa or more and 0.4 Pa or less. Time: 3 minutes or more and 10 minutes or less, preferably 4 minutes or more and 8 minutes or less, more preferably 5 minutes or more and 6 minutes or less.

[0054] The adhesion layer 6 may be formed using, other than Ti, for example, Ta, TiO2, Ni, RuO2, IrO2, ZnO, etc. The lower electrode film 2 may be formed using, other than Pt, various metals such as Au, Ru, or Ir, alloys containing these as main components, or metal oxides such as SRO or LNO.

[0055] (KNN film production) After the formation of the adhesion layer 6 and the lower electrode film 2 is completed, the KNN film 3 is subsequently formed on the lower electrode film 2 by, for example, sputtering. The composition ratio of the KNN film 3 can be adjusted, for example, by controlling the composition of the target material used during sputtering film formation. The target material can be prepared by mixing and firing K2CO3 powder, Na2CO3 powder, Nb2O5 powder, etc. The composition of the target material can be controlled by adjusting the mixing ratio of K2CO3 powder, Na2CO3 powder, Nb2O5 powder, etc. When forming a KNN film 3 containing elements such as Cu and Mn, a target material prepared by mixing the above-mentioned powders with Cu powder (or CuO powder), Mn powder (or MnO powder), etc. in a predetermined ratio can be used.

[0056] The following conditions are exemplified as conditions for forming the KNN film 3. The film formation time can be set appropriately depending on the thickness of the KNN film 3. Discharge power: 2000 W or more and 2400 W or less, preferably 2100 W or more and 2300 W or less Atmosphere: Ar gas + oxygen (O2) gas atmosphere Atmospheric pressure: 0.2 Pa or more and 0.5 Pa or less, preferably 0.2 Pa or more and 0.4 Pa or less Partial pressure of Ar gas to O gas (Ar / O partial pressure ratio): 30 / 1 to 20 / 1, preferably 27 / 1 to 22 / 1 Film formation temperature: 500°C or higher and 700°C or lower, preferably 550°C or higher and 650°C or lower Film formation rate: 0.5 μm / hr or more and 2 μm / hr or less, preferably 0.5 μm / hr or more and 1.5 μm / hr or less

[0057] (KNN film processing) After the formation of the KNN film 3 is completed, the KNN film 3 is processed (shaped) into a predetermined shape by an etching process such as wet etching using a predetermined etching solution (patterning of the KNN film 3).

[0058] In patterning the KNN film 3 by wet etching, first, for example, a silicon oxide (SiO ) film is formed on the upper surface of the KNN film 3 as an etching mask for wet etching. x) film or the like is formed. Then, for example, a laminate including the substrate 1, the adhesion layer 6, the lower electrode film 2, and the KNN film 3 is immersed in an etching solution containing an alkaline aqueous solution of a chelating agent but not containing hydrofluoric acid, and wet etching is performed on the KNN film 3. Note that as the etching solution containing an alkaline aqueous solution of a chelating agent but not containing hydrofluoric acid, an etching solution in which ethylenediaminetetraacetic acid as a chelating agent, ammonia water, and hydrogen peroxide water are mixed can be used.

[0059] If the material has etching anisotropy, such as KNN, it is easy to control the side shape of the KNN film 3 by wet etching so that the side surface of the KNN film 3 is perpendicular to the upper surface of the lower electrode film 2, or so that at least a part of the side surface of the KNN film 3 is an inclined surface inclined at an angle of, for example, 75° or more and less than 90° with respect to the upper surface of the lower electrode film 2, or so that at least a part of the side surface of the KNN film 3 is an inclined surface inclined at an angle of, for example, more than 90° and 105° or less with respect to the upper surface of the lower electrode film 2.

[0060] Furthermore, if a material such as KNN has etching anisotropy, the side shape of the KNN film 3 can be easily controlled by wet etching so that at least the surface of the KNN film 3 facing the lower electrode film 2 is inclined at an angle of, for example, 75° to less than 90°, preferably 85° to less than 90°, with respect to the upper surface of the lower electrode film 2. The side shape of the KNN film 3 can also be easily controlled by wet etching so that at least the surface of the KNN film 3, excluding the surface facing the lower electrode film 2, is perpendicular to the upper surface of the lower electrode film 2. The side shape of the KNN film 3 can also be easily controlled by wet etching so that the surface of the KNN film 3 facing the lower electrode film 2 is inclined at an angle of, for example, 75° to less than 90° with respect to the upper surface of the lower electrode film 2, and so that all the surfaces of the KNN film 3, excluding the surface facing the lower electrode film 2, are perpendicular to the upper surface of the lower electrode film 2.

[0061] The patterning of the KNN film 3 may be performed by dry etching such as reactive ion etching.

[0062] By carrying out the above-mentioned patterning, the plane area of ​​the KNN film 3 becomes smaller than the plane area of ​​the lower electrode film 2.

[0063] (Deposition of upper electrode film) After the processing of the KNN film 3 is completed, the etching mask is removed, and the upper electrode film 4 having a predetermined pattern is formed by, for example, sputtering on (the upper surface of) the KNN film 3. The conditions for forming the upper electrode film 4 can be the same as those for forming the above-mentioned lower electrode film 2.

[0064] (Formation of adhesive layer) After the deposition of the upper electrode film 4 is completed, a mask having a predetermined pattern is formed as necessary, and then, for example, by an ALD method, an adhesion layer 7 (Al2O3 layer) is formed from the upper electrode film 4 to the lower electrode film 2 so as to cover part of the side surface of the KNN film 3.

[0065] The conditions for providing the adhesive layer 7 are exemplified as follows. Temperature (substrate temperature): 100°C or higher and 500°C or lower, preferably 200°C or higher and 400°C or lower Feedstock: Trimethylaluminum ((CH3)3Al, abbreviated as TMA), pure water (H2O) Time: 10 minutes or more and 600 minutes or less, preferably 30 minutes or more and 480 minutes or less, more preferably 60 minutes or more and 150 minutes or less

[0066] As the adhesion layer 7, for example, a Ta2O5 layer may be provided.

[0067] (Insulating film formation) After the formation of the adhesion layer 7 is completed, the insulating film 5 is formed on the adhesion layer 7. In the film formation sequence of the insulating film 5, a step of forming a first layer 5a and a step of forming a second layer 5b on the first layer 5a are performed in this order.

[0068] <First layer formation step> In this step, a first layer 5a as part of the insulating film 5 is provided on the adhesion layer 7 from the upper electrode film 4 to the lower electrode film 2 so as to cover part of the side surface of the KNN film 3. In this step, the first layer 5a is provided by depositing a vapor phase precursor using, for example, a vapor phase growth method. For example, in this step, the first layer 5a made of silicon oxide is provided by a plasma CVD method using TEOS gas.

[0069] The conditions for forming the first layer 5a are exemplified as follows. Temperature (substrate temperature): 200°C or higher and 500°C or lower, preferably 300°C or higher and 400°C or lower Feedstock: TEOS, oxygen (O2) Discharge power: 50W or more and 500W or less, preferably 80W or more and 300W or less Ambient pressure: 20 Pa or more and 150 Pa or less, preferably 50 Pa or more and 70 Pa or less Time: 10 minutes or more and 20 minutes or less

[0070] By forming the first layer 5a under the above conditions, the first layer 5a can be provided with a uniform thickness from the upper electrode film 4 to the lower electrode film 2 so as to cover part of the side surface of the KNN film 3.

[0071] Furthermore, by forming the first layer 5a under the above conditions, it is possible to provide a first layer 5a that is denser than the second layer 5b and has excellent step coverage, continuity, and in-plane thickness uniformity. This reliably improves adhesion between the first layer 5a and the underlying layer (adhesion layer 7) of the insulating film 5, making it possible to suppress peeling of the insulating film 5. For example, even if unevenness resulting from the patterning of the KNN film 3 described above is formed on the side surfaces of the KNN film 3, peeling of the insulating film 5 (first layer 5a) can be suppressed.

[0072] Furthermore, by forming the first layer 5a under the above-described conditions, the thickness of the first layer 5a can be set to the minimum necessary thickness that can reliably suppress peeling of the insulating film 5 and suppress the occurrence of cracks in the first layer 5a.

[0073] <Second layer formation step> After the first layer formation step is completed, a second layer 5b is formed on the first layer 5a as part of the insulating film 5. In this step, a liquid-phase precursor is deposited to form the second layer 5b. For example, a liquid-phase precursor obtained by dissolving a methylsiloxane-based precursor in a solvent is applied to the first layer 5a using a spin coating method, and then the liquid-phase precursor is solidified (dried and baked) to form the second layer 5b made of silicon oxide. In other words, the second layer 5b is formed using a so-called SOG.

[0074] Examples of conditions for applying the liquid phase raw material include the following conditions. Spin coating rotation speed: 1500 rpm or more and 5000 rpm or less, preferably 2000 rpm or more and 4000 rpm or less, more preferably 2500 rpm or more and 3500 rpm or less Raw material: methylsiloxane solution (e.g., OCDT-7 12000T manufactured by Tokyo Ohka Kogyo Co., Ltd.)

[0075] Furthermore, the solidification (drying, firing) of the liquid phase raw material can be carried out, for example, by heating the laminate on which the liquid phase raw material has been applied using a hot plate to thoroughly volatilize the solvent in the liquid phase raw material, and then holding the laminate in a nitrogen atmosphere at a predetermined temperature (for example, 300°C or higher and 600°C or lower, preferably 400°C or higher and 500°C or lower) for a predetermined time (for example, 20 minutes or higher and 60 minutes or lower, preferably 30 minutes or higher and 40 minutes or lower). Heating using a hot plate can be carried out, for example, by carrying out the following steps in this order: first heating, in which the laminate is heated for a predetermined time (e.g., 30 seconds to 120 seconds) using a hot plate adjusted to a predetermined first temperature (e.g., 90°C to 120°C); second heating, in which the laminate is heated for a predetermined time (e.g., 30 seconds to 120 seconds) using a hot plate adjusted to a predetermined second temperature higher than the first temperature (e.g., 140°C to 170°C); and third heating, in which the laminate is heated for a predetermined time (e.g., 30 seconds to 120 seconds) using a hot plate adjusted to a predetermined third temperature higher than the first and second temperatures (e.g., 180°C to 220°C).

[0076] By forming the second layer 5b under the above conditions, the second layer 5b having the slope portion 9a can be provided. Furthermore, by forming the second layer 5b under the above conditions, the shape of the slope portion 9a can be easily controlled to reduce the step. For example, the shape of the slope portion 9a can be easily controlled so that the surface is non-parallel to the side surface of the KNN film 3. Furthermore, the shape of the slope portion 9a can be easily controlled so that the thickness t2 of the insulating film 5 in the slope portion 9a gradually increases from the upper electrode film 4 side toward the lower electrode film 2 side.

[0077] Furthermore, by forming the second layer 5b under the above conditions, it is possible to provide the second layer 5b having a slope portion 9b. Furthermore, by forming the second layer 5b under the above conditions, it is possible to easily control the shape of the slope portion 9b. For example, the shape of the slope portion 9b can be easily controlled so that the surface is a plane that is not parallel to the direction perpendicular to the upper surface of the upper electrode film 4. Furthermore, the shape of the slope portion 9b can be easily controlled so that the thickness t3 of the insulating film 5 in the slope portion 9b gradually becomes thinner from the outside toward the inside of the upper electrode film 4.

[0078] Furthermore, by forming the second layer 5b under the above conditions, it becomes possible to easily adjust the angles θ2 and θ3.

[0079] Furthermore, by forming the second layer 5b under the above conditions, the surfaces of the slope portions 9a and 9b can be curved, preferably surfaces without steps.

[0080] (Formation of metal wiring) After the formation of the insulating film 5 is completed, if a predetermined mask has been formed, the mask is removed. Then, the metal wiring 8 is formed on the insulating film 5. In the sequence for forming the metal wiring 8, a step of forming an adhesion layer on the insulating film 5 and a step of forming the metal wiring 8 on the adhesion layer are performed in this order.

[0081] <Adhesion layer formation step> In this step, a mask having a predetermined pattern is formed as needed, and then a layer made of Ti is provided as an adhesive layer by, for example, electron beam (EB) evaporation.

[0082] The conditions for providing the adhesive layer include, for example, the following conditions. Temperature (substrate temperature): 80°C or higher and 120°C or lower, preferably 90°C or higher and 110°C or lower Time: 1 minute or more and 10 minutes or less, preferably 3 minutes or more and 5 minutes or less

[0083] The adhesion layer for improving adhesion between the insulating film 5 and the metal wiring 8 may be formed using Ta, TiO2, Ni, RuO2, IrO2, etc., in addition to Ti. This adhesion layer can also be formed using a method such as sputtering, in addition to EB evaporation.

[0084] <Metal wiring formation step> In this step, metal wiring 8, which is connected to the upper electrode film 4 but not to the lower electrode film 2, is provided on the adhesion layer formed on the insulating film 5. For example, the metal wiring 8 made of Au is provided by EB evaporation.

[0085] The conditions for providing the metal wiring 8 are exemplified as follows. Temperature (substrate temperature): 80°C or higher and 120°C or lower, preferably 90°C or higher and 110°C or lower Time: 5 to 30 minutes, preferably 10 to 20 minutes

[0086] The metal wiring 8 may be formed using various metals other than Au, such as Pt, Au, Al, Cu, or alloys thereof. The metal wiring 8 may also be formed using techniques such as sputtering in addition to EB evaporation.

[0087] After the formation of the metal wiring 8 is completed, if a predetermined mask has been provided, the predetermined mask is removed. This results in a piezoelectric laminate 10 having the substrate 1, the adhesion layer 6, the lower electrode film 2 (Pt film), the KNN film 3, the upper electrode film 4, the adhesion layer 7, the insulating film 5, and the metal wiring 8, as shown in FIG. 1(a).

[0088] (Fabrication of piezoelectric elements and piezoelectric device modules) Then, predetermined processing is performed on the insulating film 5 to expose a portion of the lower electrode film 2 and form the piezoelectric stack 10 into a predetermined shape. This results in a piezoelectric element 20 as shown in Fig. 5, and by connecting a voltage application unit 11a or a voltage detection unit 11b to the piezoelectric element 20, a piezoelectric device module 30 is obtained.

[0089] (5) Effects The present disclosure provides one or more of the following advantages:

[0090] (a) The insulating film 5 is formed with a sloped portion 9a that fills the step between the upper surface of the upper electrode film 4 and the upper surface of the lower electrode film 2, and the sloped portion 9a is formed in a shape that reduces the step, thereby making it possible to prevent breakage of the metal wiring 8. As a result, it is possible to improve the reliability of the piezoelectric element 20 and the piezoelectric device module 30.

[0091] (b) The insulating film 5 has a sloped portion 9b formed therein, which prevents a step from occurring between the upper surface of the insulating film 5 and the upper electrode film 4, thereby reliably preventing disconnection of the metal wiring 8. As a result, the reliability of the piezoelectric element 20 and the piezoelectric device module 30 can be reliably improved.

[0092] (c) The formation of the sloped portions 9a and 9b in the insulating film 5 makes it possible to prevent breakage of the metal wiring 8 even if the thickness of the metal wiring 8 is made thinner than before. As a result, it is possible to further reduce the size and weight of the piezoelectric device module 30 and to reduce the manufacturing costs.

[0093] (d) The surfaces of the slope portions 9a and 9b are curved, which makes it possible to reliably prevent disconnection of the metal wiring 8. Furthermore, the surfaces of the slope portions 9a and 9b are not stepped, which makes it possible to more reliably prevent disconnection of the metal wiring 8.

[0094] (e) The side of the KNN film 3 is perpendicular to the upper surface of the lower electrode film 2, or at least a portion of the side of the KNN film 3 is an inclined surface inclined at an angle of 75° or more and less than 90° to the upper surface of the lower electrode film 2, or at least a portion of the side of the KNN film 3 is an inclined surface inclined at an angle of more than 90° and less than 105° to the upper surface of the lower electrode film 2, thereby making it possible to avoid a deterioration in the characteristics of the piezoelectric device module 30.

[0095] (f) Since the insulating film 5 has a laminated structure in which the first layer 5a and the second layer 5b are laminated, it is possible to form the slope portions 9a, 9b in the insulating film 5 while suppressing peeling of the insulating film 5.

[0096] (g) Since the first layer 5a and the second layer 5b are formed using the same material, the adhesion between the first layer 5a and the second layer 5b is improved, and peeling of the second layer 5b, i.e., peeling of the insulating film 5, can be reliably suppressed.

[0097] (h) By depositing a liquid-phase precursor to provide the second layer 5b as part of the insulating film 5, the slope portions 9a, 9b can be easily formed in the second layer 5b (insulating film 5), and the above-mentioned angles θ2, θ3 can also be easily adjusted.

[0098] (i) By depositing a vapor phase precursor to provide the first layer 5a as part of the insulating film 5, the first layer 5a has a higher density than the second layer 5b, and is a layer that is excellent in step coverage, continuity, and in-plane thickness uniformity. The insulating film 5 having such a first layer 5a can improve adhesion between the insulating film 5 and the underlying layer, and can suppress peeling of the insulating film 5.

[0099] Fig. 6(a) shows an example of the cross-sectional structure of a piezoelectric laminate according to one embodiment of the present disclosure, and Fig. 6(b) shows an SEM image of the area indicated by dotted line A in Fig. 6(a). The laminate shown in Figs. 6(a) and 6(b) is a laminate in which a lower electrode film 2 is provided on a substrate 1, a KNN film 3 is provided on the lower electrode film 2, the KNN film 3 is patterned by wet etching, a first layer 5a is provided to cover the surface of the KNN film 3 and the upper surface of the lower electrode film 2, and a second layer 5b is provided on the first layer 5a. In other words, the laminate shown in Figs. 6(a) and 6(b) does not have an adhesion layer 7 and is a laminate before the metal wiring 8 is formed. From Figure 6(b), it can be seen that at least the surface of the side of the KNN film 3 exposed by etching that faces the lower electrode film 2 is an inclined surface that is inclined at an angle of 75° or more and less than 90° with respect to the upper surface of the lower electrode film 2, and even if the surfaces of the side of the KNN film 3 other than the surface facing the lower electrode film 2 are perpendicular to the upper surface of the lower electrode film 2, the first layer 5a having excellent step coverage and continuity is provided with a uniform thickness, and further, the second layer 5b can form a slope portion 9a in the insulating film 5.

[0100] FIG. 7(a) shows an example of the cross-sectional structure of a piezoelectric laminate according to one embodiment of the present disclosure. FIG. 7(b) shows an SEM image of the area indicated by dotted line B in FIG. 7(a). FIG. 7(c) shows an SEM image of the area indicated by dotted line C in FIG. 7(b). FIG. 7(d) shows an SEM image of the area indicated by dotted line D in FIG. 7(b). FIG. 7(e) shows an SEM image of the area indicated by dotted line E in FIG. 7(b). The piezoelectric laminate shown in FIGS. 7(b)-(e) was fabricated under the conditions described above by providing a lower electrode film 2, a KNN film 3, an upper electrode film 4, an insulating film 5 (first layer 5a and second layer 5b), and a metal wiring 8 made of Au. From FIGS. 7(b)-(e), it can be seen that sloped portions 9a and 9b were formed in the insulating film 5 and that no breaks occurred in the metal wiring 8, i.e., that breaks in the metal wiring 8 were avoided.

[0101] For reference, a conventional piezoelectric laminate will now be described. As shown in FIG. 11 , in the conventional piezoelectric laminate 100, a step (global step) occurs in the insulating film 5 due to the step between the upper surface of the upper electrode film 4 and the upper surface of the lower electrode film 2. This poses a problem in that the metal wiring 8 is easily broken or the insulating film 5 is easily peeled off at corners formed by the side surface of the KNN film 3 and the upper surface of the lower electrode film 2, or at corners formed by the upper surface and side surface of the upper electrode film 4. In contrast, in this embodiment, a sloped portion 9a that fills the step between the upper surface of the upper electrode film 4 and the upper surface of the lower electrode film 2 is formed in the insulating film 5, and the sloped portion 9a is shaped to reduce the step. This makes it possible to prevent breakage of the metal wiring 8. Furthermore, in this embodiment, the insulating film 5 has a layered structure formed by stacking a first layer 5a and a second layer 5b, which also makes it possible to prevent peeling of the insulating film 5.

[0102] 12, in order to avoid disconnection of the metal wiring 8, it is also possible to form the side surface of the KNN film 3 as an inclined surface that is inclined at an angle of more than 105° with respect to the upper surface of the lower electrode film 2, i.e., to set the above-mentioned angle θ1 to be more than 105° and less than 180°. However, in the piezoelectric laminate 101, the area of ​​the upper surface of the KNN film 3 is reduced, which degrades the characteristics of the piezoelectric device module 30 fabricated by processing the piezoelectric laminate 101. In contrast, in this embodiment, the sloped portions 9a and 9b are formed in the insulating film 5, which makes it possible to avoid a reduction in the area of ​​the upper surface of the KNN film 3 and thus a degradation in the characteristics of the piezoelectric device module 30, while also preventing disconnection of the metal wiring 8.

[0103] (6) Variations This aspect can be modified as follows. In the following description of the modifications, the same components as those in the above aspect are denoted by the same reference numerals, and the description thereof will be omitted. The above aspect and the following modifications can be combined in any way.

[0104] (Variation 1) In the above embodiment, an example in which the slope portions 9a and 9b are formed in the insulating film 5 has been described, but the present invention is not limited to this. For example, as shown in FIG. 8, it is sufficient that at least the slope portion 9a is formed in the insulating film 5. In this modification, it is also possible to prevent disconnection of the metal wiring 8, and the same effect as in the above embodiment can be obtained. However, from the viewpoint of reliably preventing disconnection of the metal wiring 8, it is preferable that both the slope portions 9a and 9b are formed in the insulating film 5.

[0105] (Variation 2) In the above embodiment, the insulating film 5 has the first layer 5a and the second layer 5b, but the present invention is not limited to this. For example, as shown in FIG. 9, the insulating film 5 may be a single-layer film. The single-layer insulating film 5 can be formed by the same method and under the same conditions as those used to form the second layer 5b. In this modification, at least the slope portion 9a is formed in the insulating film 5, thereby achieving the same effect as the above embodiment.

[0106] However, from the viewpoint of reliably suppressing peeling of the insulating film 5, it is preferable that the insulating film 5 has the first layer 5a and the second layer 5b. Furthermore, in this modification, if the insulating film 5 is formed to a thickness that allows the slope portion 9a to be formed, the inside of the slope portion 9a may become half-baked due to defective firing. From the viewpoint of avoiding defective firing of the insulating film 5, it is preferable that the insulating film 5 has the first layer 5a and the second layer 5b.

[0107] (Variation 3) In the above embodiment, an example has been described in which the insulating film 5 is provided from the upper electrode film 4 to the lower electrode film 2 so as to cover a portion of the side surface of the KNN film 3, but this is not limiting. The insulating film 5 may be provided from the upper electrode film 4 to the lower electrode film 2 so as to cover at least a portion of the side surface of the KNN film 3. For example, as shown in FIGS. 10(a) and 10(b), the insulating film 5 may be provided from the upper electrode film 4 to the lower electrode film 2 so as to cover the entire side surface of the KNN film 3. This can reliably improve the reliability of the piezoelectric stack 10, the piezoelectric element 20, and the piezoelectric device module 30. However, the insulating film 5 need only be provided in areas where insulation is required.

[0108] (Variation 4) In the above embodiment, an example has been described in which the KNN film 3 is deposited, the KNN film 3 is processed, and the upper electrode film 4 is deposited in this order, but the order of the steps may be changed as appropriate. For example, the KNN film 3 is deposited, the upper electrode film 4 is deposited, and the upper electrode film 4 and the KNN film 3 are processed (patterned) in this order. The upper electrode film 4 can be patterned by various known methods.

[0109] (Variation 5) In the above embodiment, the piezoelectric laminate 10 has the adhesion layers 6 and 7, but is not limited to this. The adhesion layers 6 and 7 may be provided as needed, and if a predetermined adhesion can be ensured without providing the adhesion layers 6 and 7, the adhesion layers 6 and 7 may not be provided.

[0110] (Variation 6) In the above embodiment, the piezoelectric film 3 is made of KNN, but the present invention is not limited thereto. The piezoelectric film 3 may be made of a material having etching anisotropy, in addition to KNN. For example, the piezoelectric film 3 may be an oxide film having a perovskite structure containing lead, zirconium, titanium, and oxygen (PZT film), a film made of polydimethylsiloxane (PDMS film), an oxide film having a perovskite structure containing bismuth, sodium, titanium, and oxygen (BNT film), or an oxide film containing bismuth, iron, and oxygen (bismuth ferrite film). In this modification, the insulating film 5 has a configuration similar to that of the above embodiment and modification, and thus the same effects as those of the above embodiment and modification can be obtained.

[0111] (Variation 7) In the above embodiment, an example has been described in which the piezoelectric laminate 10 has the metal wiring 8, but the present invention is not limited to this. The laminate before the metal wiring 8 is provided can also be considered as the piezoelectric laminate 10, and the piezoelectric laminate 10 may be distributed on the market without the metal wiring 8 provided.

[0112] (Variation 8) For example, an orientation control layer for controlling the orientation of the crystals constituting the KNN film 3 may be provided between the lower electrode film 2 and the KNN film 3, i.e., directly below the KNN film 3. If the lower electrode film 2 is not provided, an orientation control layer may be provided between the substrate 1 and the KNN film 3. The orientation control layer may be formed using a metal oxide such as SRO, LNO, or strontium titanate (SrTiO3, abbreviated as STO), which is different from the material constituting the lower electrode film 2. The crystals constituting the orientation control layer preferably have a (100) plane preferential orientation relative to the main surface of the substrate 1.

[0113] (Variation 9) For example, the KNN film 3 may contain, in addition to Cu or Mn, or instead of Cu or Mn, other metal elements that have the same effect as Cu or Mn, at a predetermined concentration.

[0114] (Variation 10) In the above embodiment, an example in which one laminated structure is formed on one substrate 1 has been described, but this is not limiting. For example, multiple laminated structures may be formed on one substrate 1. In this case, each of the multiple laminated structures includes a lower electrode film 2, a KNN film 3 provided on the lower electrode film 2 and having a plane area smaller than that of the lower electrode film 2, an upper electrode film 4 provided on the KNN film 3, and an insulating film 5 provided from the upper electrode film 4 to the lower electrode film 2 so as to cover at least a portion of the side surface of the KNN film 3, and the insulating film 5 preferably has at least the slope portion 9a described above. A substrate 1 on which one or more laminated structures are formed is also referred to as a piezoelectric laminated substrate.

[0115] (Variation 11) For example, when the above-mentioned piezoelectric laminate 10 is molded into the piezoelectric element 20, the substrate 1 may be removed from the piezoelectric laminate 10, as long as the piezoelectric device module 30 made using the piezoelectric laminate 10 (piezoelectric element 20) can be used for a desired purpose such as a sensor or actuator.

[0116] <Preferred aspects of the present disclosure> Preferred aspects of the present disclosure will be described below.

[0117] (Appendix 1) According to one aspect of the present disclosure, A substrate; a lower electrode film provided on the substrate; a piezoelectric film provided on the lower electrode film and having a plane area smaller than the plane area of ​​the lower electrode film; an upper electrode film provided on the piezoelectric film; an insulating film provided from the upper electrode film to the lower electrode film so as to cover at least a part of a side surface of the piezoelectric film, a slope portion is formed in the insulating film to fill a step between an upper surface of the upper electrode film and an upper surface of the lower electrode film; The sloped portion is formed in a shape that reduces the step.

[0118] (Appendix 2) The piezoelectric laminate according to Supplementary Note 1, preferably The surface of the slope portion is non-parallel to the side surface of the piezoelectric film.

[0119] (Appendix 3) The piezoelectric laminate according to Supplementary Note 1 or 2, preferably In the slope portion of the insulating film, the thickness (t2) of the insulating film, which is defined as the shortest distance from a point on the side surface of the piezoelectric film to the surface of the slope portion in a direction parallel to the top surface of the substrate in a vertical cross section of the slope portion including the piezoelectric laminate, gradually becomes thicker from the side of the upper electrode film toward the side of the lower electrode film.

[0120] (Appendix 4) The piezoelectric laminate according to any one of Supplementary Notes 1 to 3, preferably The surface of the slope portion is a surface including a curved surface. Preferably, the surface of the slope portion does not have a step.

[0121] (Appendix 5) The piezoelectric laminate according to any one of Supplementary Notes 1 to 4, preferably the insulating film is provided so as to cover the upper surface of the upper electrode film, The insulating film located on the upper surface of the upper electrode film has a second slope portion formed thereon so as to prevent a step from occurring between the upper surface of the insulating film and the upper electrode film. Preferably, the surface of the second slope portion is a surface that is not parallel to a direction perpendicular to the upper surface of the upper electrode film.

[0122] (Appendix 6) The piezoelectric laminate according to Supplementary Note 5, preferably In the second slope portion of the insulating film, the thickness (t3) of the insulating film, which is defined as the shortest distance from a point on the surface of the second slope portion to the upper surface of the upper electrode film, gradually becomes thinner from the outside of the upper electrode film toward the inside of the upper electrode film.

[0123] (Appendix 7) The piezoelectric laminate according to Supplementary Note 5 or 6, preferably The surface of the second slope portion is a surface including a curved surface. Preferably, the surface of the second slope portion does not have a step.

[0124] (Appendix 8) The piezoelectric laminate according to any one of Supplementary Notes 1 to 7, preferably The side surface of the piezoelectric film is perpendicular to the top surface of the lower electrode film.

[0125] (Appendix 9) The piezoelectric laminate according to any one of Supplementary Notes 1 to 7, preferably At least a portion of the side surface of the piezoelectric film is an inclined surface inclined at an angle of 75° or more and less than 90°, preferably 85° or more and less than 90°, relative to the upper surface of the lower electrode film, or an inclined surface inclined at an angle of more than 90° and less than 105°, preferably more than 90° and less than 100°, relative to the upper surface of the lower electrode film.

[0126] (Appendix 10) The piezoelectric laminate according to Supplementary Note 9, preferably Of the side surfaces of the piezoelectric film, at least the surface facing the lower electrode film is an inclined surface inclined at an angle of 75° or more and less than 90°, preferably 85° or more and less than 90°, with respect to the upper surface of the lower electrode film. Also preferably, of the side surfaces of the piezoelectric film, at least the surfaces excluding the surface facing the lower electrode film are perpendicular to the upper surface of the lower electrode film.

[0127] (Appendix 11) The piezoelectric laminate according to any one of Supplementary Notes 1 to 10, preferably Metal wiring connected to the upper electrode film is provided on the insulating film.

[0128] (Appendix 12) The piezoelectric laminate according to Supplementary Note 11, preferably The thickness of the metal wiring is equal to or thinner than the thinnest thickness of the insulating film (t1), which is defined as the shortest distance from a point on the top surface of the lower electrode film or the top surface of the upper electrode film to the surface of the insulating film. Preferably, the thickness of the metal wiring is 1 / 20 to 1 / 2, more preferably 1 / 20 to 1 / 4, of the thickness of the piezoelectric film.

[0129] (Appendix 13) The piezoelectric laminate according to any one of Supplementary Notes 1 to 12, preferably The insulating film is a first layer having a uniform thickness; and a second layer provided on the first layer and forming the slope portion.

[0130] (Appendix 14) The piezoelectric stack according to Supplementary Note 13, preferably The first layer is formed by depositing a vapor phase precursor, and the second layer is formed by depositing a liquid phase precursor. Preferably, the density of the first layer is different from the density of the second layer. More preferably, the density of the first layer is higher than the density of the second layer.

[0131] (Appendix 15) The piezoelectric stack according to claim 14, preferably The thickness (t5) of the second layer, which is defined as the distance from a point on the lower surface of the second layer in a region that is not located above the upper electrode film and that is not the region that forms the slope portion, to the surface of the second layer in a direction perpendicular to the upper surface of the substrate, is thicker than the thickness (t4) of the first layer, which is defined as the distance from a point on the lower surface of the first layer in a region that is not located above the upper electrode film and that is not below the slope portion, to the surface of the first layer in a direction perpendicular to the upper surface of the substrate.

[0132] (Appendix 16) The piezoelectric laminate according to any one of Supplementary Notes 13 to 15, preferably The first layer and the second layer are formed using the same material.

[0133] (Appendix 17) The piezoelectric stack according to claim 16, preferably The first layer and the second layer are both made of silicon oxide.

[0134] (Appendix 18) The piezoelectric laminate according to any one of Supplementary Notes 13 to 17, preferably the first layer is formed using a vapor phase growth method (CVD method, ALD method, sputtering method, vacuum deposition method, etc.), The second layer is formed by solidifying (for example, drying or baking) a liquid-phase precursor that has been applied onto the first layer (for example, by spin coating).

[0135] (Appendix 19) The piezoelectric laminate according to any one of Supplementary Notes 1 to 18, preferably An adhesive layer for enhancing adhesion between the insulating film and the base (the upper electrode film, the piezoelectric film, and the lower electrode film) is provided between the insulating film and the base.

[0136] (Appendix 20) The piezoelectric stack according to Supplementary Note 19, preferably The adhesion layer is made of an insulating metal oxide (insulating material), and is preferably made of either aluminum oxide (Al2O3) or tantalum oxide (Ta2O5).

[0137] (Appendix 21) The piezoelectric laminate according to any one of Supplementary Notes 1 to 20, preferably The piezoelectric film is made of a material having etching anisotropy.

[0138] (Appendix 22) The piezoelectric laminate according to any one of Supplementary Notes 1 to 21, preferably The piezoelectric film is an alkali niobium oxide film containing potassium, sodium, niobium, and oxygen and having a perovskite structure.

[0139] (Appendix 23) According to another aspect of the present disclosure, A substrate; a lower electrode film provided on the substrate; a piezoelectric film provided on the lower electrode film and having a plane area smaller than the plane area of ​​the lower electrode film; an upper electrode film provided on the piezoelectric film; an insulating film provided from the upper electrode film to the lower electrode film so as to cover at least a part of a side surface of the piezoelectric film, a slope portion is formed in the insulating film to fill a step between an upper surface of the upper electrode film and an upper surface of the lower electrode film; The sloped portion is formed in a shape that reduces the step.

[0140] (Appendix 24) According to yet another aspect of the present disclosure, A piezoelectric laminate substrate in which a plurality of laminate structures are formed on a single substrate, Each of the plurality of laminated structures is a lower electrode film; a piezoelectric film provided on the lower electrode film and having a plane area smaller than the plane area of ​​the lower electrode film; an upper electrode film provided on the piezoelectric film; an insulating film provided from the upper electrode film to the lower electrode film so as to cover at least a part of a side surface of the piezoelectric film, a slope portion is formed in the insulating film to fill a step between an upper surface of the upper electrode film and an upper surface of the lower electrode film; The sloped portion is formed in a shape that reduces the step.

[0141] (Appendix 25) According to yet another aspect of the present disclosure, providing a lower electrode film on a substrate; providing a piezoelectric film on the lower electrode film; a step of processing the piezoelectric film into a predetermined shape; providing an upper electrode film on the piezoelectric film; providing an insulating film from the upper electrode film to the lower electrode film so as to cover at least a part of a side surface of the piezoelectric film; In the step of providing the insulating film, forming a slope portion in the insulating film to fill a step between an upper surface of the upper electrode film and an upper surface of the lower electrode film; There is provided a method for manufacturing a piezoelectric laminate, in which the shape of the slope portion is controlled to reduce the step.

[0142] (Appendix 26) The method according to claim 25, preferably comprising: In the step of providing the insulating film, the shape of the slope portion is controlled so that the thickness (t2) of the insulating film, which is defined as the shortest distance from a point on the side of the piezoelectric film to the surface of the slope portion in a direction parallel to the top surface of the substrate, in a vertical cross section of the slope portion including the piezoelectric laminate, gradually becomes thicker from the side of the upper electrode film toward the side of the lower electrode film.

[0143] (Appendix 27) The method according to claim 25 or 26, preferably comprising: In the step of providing the insulating film, A second slope portion that does not create a step between the upper surface of the insulating film and the upper electrode film is further formed in the insulating film.

[0144] (Appendix 28) The method according to any one of Supplementary Notes 25 to 27, preferably comprising: In the step of processing the piezoelectric film, The shape of the side surface of the piezoelectric film is controlled so that the side surface of the piezoelectric film is perpendicular to the upper surface of the lower electrode film.

[0145] (Appendix 29) The method according to any one of Supplementary Notes 25 to 27, preferably comprising: In the step of processing the piezoelectric film, The shape of the side surface of the piezoelectric film is controlled so that at least a portion of the side surface of the piezoelectric film is an inclined surface that is inclined at an angle of 75° or more and less than 90°, preferably 85° or more and less than 90°, relative to the upper surface of the lower electrode film, or an inclined surface that is inclined at an angle of more than 90° and less than 105°, preferably more than 90° and less than 100°, relative to the upper surface of the lower electrode film.

[0146] (Appendix 30) The method according to claim 29, preferably comprising: In the step of processing the piezoelectric film, the side shape of the piezoelectric film is controlled so that at least the surface of the side of the piezoelectric film facing the lower electrode film is an inclined surface inclined at an angle of 75° to 90°, preferably 85° to 90°, with respect to the upper surface of the lower electrode film. Also preferably, in the step of processing the piezoelectric film, the side shape of the piezoelectric film is controlled so that at least the surfaces of the side of the piezoelectric film excluding the surface facing the lower electrode film are perpendicular to the upper surface of the lower electrode film.

[0147] (Appendix 31) The method according to any one of Supplementary Notes 25 to 30, preferably comprising: The method further includes the step of providing metal wiring connected to the upper electrode film on the insulating film.

[0148] (Appendix 32) The method according to any one of Supplementary Notes 25 to 31, preferably comprising: In the step of providing the insulating film, a liquid phase precursor is deposited to provide at least a portion of the insulating film.

[0149] (Appendix 33) The method according to any one of Supplementary Notes 25 to 32, preferably comprising: In the step of providing the insulating film, a vapor phase precursor is deposited to provide at least a portion of the insulating film.

[0150] (Appendix 34) The method according to any one of Supplementary Notes 25 to 33, preferably comprising: In the step of providing the insulating film, a first layer having a uniform thickness is provided as part of the insulating film from the upper electrode film to the lower electrode film so as to cover at least a part of the side surface of the piezoelectric film; A second layer having the slope portion is provided on the first layer as part of the insulating film.

[0151] (Appendix 35) The method according to any one of Supplementary Notes 25 to 34, preferably comprising: In the process of providing the insulating film, a vapor phase precursor is deposited using a vapor phase growth method (CVD, ALD, sputtering, vacuum deposition, etc.) to provide the first layer, a liquid phase precursor is applied onto the first layer (for example, using a spin coating method), and the liquid phase precursor is solidified (dried and fired) to provide the second layer.

[0152] (Appendix 36) The method according to any one of Supplementary Notes 25 to 35, preferably comprising: The method further includes providing an adhesion layer that enhances adhesion between the insulating film and a base of the insulating film, The step of providing the adhesive layer is performed after the step of forming the upper electrode film and before the step of providing the insulating film. [Explanation of symbols]

[0153] 1 board 2 Lower electrode film 3 Piezoelectric film (KNN film) 4 Upper electrode film 5. Insulating film 5a 1st layer 5b 2nd layer 9a, 9b Slope section 10 Piezoelectric laminate

Claims

1. A substrate; a lower electrode film provided on the substrate; a piezoelectric film provided on the lower electrode film and having a plane area smaller than the plane area of ​​the lower electrode film; an upper electrode film provided on the piezoelectric film; an insulating film provided from the upper electrode film to the lower electrode film so as to cover at least a part of a side surface of the piezoelectric film, a slope portion is formed in the insulating film to fill a step between an upper surface of the upper electrode film and an upper surface of the lower electrode film; The slope portion is formed in a shape that reduces the step, The surface of the slope portion is a surface that includes a curved surface.

2. 2. The piezoelectric stack according to claim 1, wherein the thickness of the insulating film, defined as the shortest distance from a point on the side surface of the piezoelectric film to the surface of the slope portion in a direction parallel to the top surface of the substrate, in a vertical cross section of the slope portion including the piezoelectric stack, gradually increases from the side of the upper electrode film to the side of the lower electrode film.

3. The piezoelectric stack according to claim 1 , wherein the side surface of the piezoelectric film is perpendicular to the upper surface of the lower electrode film.

4. 3. The piezoelectric stack according to claim 1, wherein at least the side surface of the piezoelectric film facing the lower electrode film is an inclined surface inclined at an angle of 75° or more and less than 90° with respect to the upper surface of the lower electrode film.

5. The piezoelectric stack according to claim 4 , wherein the side surfaces of the piezoelectric film, excluding at least the surface on the lower electrode film side, are perpendicular to the upper surface of the lower electrode film.

6. 6. The piezoelectric laminate according to claim 1, wherein a metal wiring connected to the upper electrode film is provided on the insulating film.

7. The insulating film is a first layer having a uniform thickness; 7. The piezoelectric laminate according to claim 1, further comprising: a second layer provided on the first layer and forming the slope portion.

8. the first layer is formed by depositing a vapor phase source; The piezoelectric stack according to claim 7 , wherein the second layer is formed by depositing a liquid phase raw material.

9. 9. The piezoelectric stack according to claim 7, wherein the first layer and the second layer are both made of silicon oxide.

10. 10. The piezoelectric laminate according to claim 1, wherein an adhesive layer is provided between the insulating film and the base of the insulating film to enhance adhesion between the insulating film and the base.

11. 11. The piezoelectric stack according to claim 1, wherein the piezoelectric film is an alkali niobium oxide film containing potassium, sodium, niobium, and oxygen and having a perovskite structure.

12. A substrate; a lower electrode film provided on the substrate; a piezoelectric film provided on the lower electrode film and having a plane area smaller than the plane area of ​​the lower electrode film; an upper electrode film provided on the piezoelectric film; an insulating film provided from the upper electrode film to the lower electrode film so as to cover at least a part of a side surface of the piezoelectric film, a slope portion is formed in the insulating film to fill a step between an upper surface of the upper electrode film and an upper surface of the lower electrode film; The slope portion is formed in a shape that reduces the step, A piezoelectric element, wherein the surface of the slope portion includes a curved surface.

13. providing a lower electrode film on a substrate; providing a piezoelectric film on the lower electrode film; a step of processing the piezoelectric film into a predetermined shape; providing an upper electrode film on the piezoelectric film; providing an insulating film from the upper electrode film to the lower electrode film so as to cover at least a part of a side surface of the piezoelectric film; In the step of providing the insulating film, forming a slope portion in the insulating film to fill a step between an upper surface of the upper electrode film and an upper surface of the lower electrode film; a method for manufacturing a piezoelectric laminate, the shape of the slope portion being controlled to reduce the step and to have a curved surface;

14. The method for manufacturing a piezoelectric stack according to claim 13 , wherein in the step of providing the insulating film, at least a part of the insulating film is provided by depositing a liquid-phase precursor.

15. In the step of providing the insulating film, a first layer having a uniform thickness is provided as part of the insulating film from the upper electrode film to the lower electrode film so as to cover at least a part of the side surface of the piezoelectric film; The method for manufacturing a piezoelectric stack according to claim 13 or 14, further comprising providing a second layer having the slope portion on the first layer as a part of the insulating film.

16. In the step of providing the insulating film, depositing a vapor source using a vapor deposition method to provide the first layer; The method for manufacturing a piezoelectric stack according to claim 15, wherein the second layer is formed by applying a liquid phase raw material onto the first layer and solidifying the liquid phase raw material.

17. The method further includes providing an adhesion layer that enhances adhesion between the insulating film and a base of the insulating film, The method for manufacturing a piezoelectric laminate according to any one of claims 13 to 16, wherein the step of providing the adhesion layer is performed after the step of forming the upper electrode film and before the step of providing the insulating film.

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