Laminated substrate with piezoelectric film, method for manufacturing laminated substrate and piezoelectric element

Abstract

To improve the adhesion between a substrate and a piezoelectric film in a laminated substrate with the piezoelectric film, while preventing a decrease in the orientation of the piezoelectric film.SOLUTION: A laminated substrate has a substrate and a piezoelectric film made of an alkali niobium oxide containing potassium, sodium, niobium, and oxygen, which is formed on the substrate, when SIMS analysis is performed on the area of the substrate extending from the surface of the substrate with the piezoelectric film to a depth of 1 μm toward the opposite side of the substrate with the piezoelectric film, the concentration of potassium is less than 5E15 cm-3, the concentration of sodium is less than 5E15 cm-3, and the orientation of the crystals constituting the piezoelectric film in the (001) plane orientation is 96% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a laminated substrate having a piezoelectric film, a method for manufacturing the laminated substrate, and a piezoelectric element.

Background Art

[0002] Piezoelectrics are widely used in functional electronic components such as sensors and actuators. As piezoelectric materials, lead-based materials, particularly PZT-based ferroelectrics represented by the composition formula Pb(Zr 1-x Ti x )O3, are widely used. Since PZT-based piezoelectrics contain lead, they are not preferable from the viewpoint of pollution prevention and the like. Therefore, as a lead-free piezoelectric material, a piezoelectric material (KNN) containing potassium, sodium, niobium, and oxygen has been proposed, and a laminated substrate having a substrate, a lower electrode film formed on the substrate, and a piezoelectric film formed on the lower electrode film using KNN has been proposed (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to improve the adhesion between a substrate and a piezoelectric film while suppressing a decrease in the orientation of the piezoelectric film in a laminated substrate having the piezoelectric film.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, a substrate, A piezoelectric film made of an alkali niobate oxide containing potassium, sodium, niobium, and oxygen, which is formed on the substrate, When performing SIMS analysis on a region ranging from the surface of the substrate on which the piezoelectric film is formed to a depth of 1 μm toward the surface of the substrate opposite to the surface on which the piezoelectric film is formed among the substrates, the concentration of potassium is 5E15 cm -3 or less, and the concentration of sodium is 5E15 cm -3 or less, The orientation ratio of the crystal constituting the piezoelectric film in the (001) plane direction is 96% or more. A laminated substrate or a piezoelectric element is provided.

[0006] According to another aspect of the present disclosure, A step of preparing a substrate, A step of forming a piezoelectric film made of an alkali niobate oxide containing potassium, sodium, niobium, and oxygen on the substrate by a sputtering method, In the step of forming the piezoelectric film, the film formation temperature is 400 °C or higher and less than 500 °C, the oxygen partial pressure is 0.0025 Pa or higher and less than 0.01 Pa, and the atmospheric pressure is 0.03 Pa or higher and less than 0.1 Pa. A method for manufacturing a laminated substrate is provided.

Advantages of the Invention

[0007] According to the present disclosure, in a laminated substrate having a piezoelectric film, it is possible to improve the adhesion between the substrate and the piezoelectric film while suppressing a decrease in the orientation of the piezoelectric film.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiment for Carrying Out the Invention

[0009] <An aspect of the present disclosure> Hereinafter, an aspect of the present disclosure will be described with reference to the drawings.

[0010] (1) Configuration of the laminated substrate As shown in FIG. 1, a laminated substrate (laminate) 10 having a piezoelectric film according to this aspect (hereinafter also referred to as the laminate 10) includes a substrate 1, a lower electrode film 2 formed on the substrate 1, a piezoelectric film (piezoelectric thin film) 3 formed on the lower electrode film 2, and an upper electrode film 4 formed on the piezoelectric film 3. Note that the film obtained by "film formation" in the present disclosure is a film directly deposited on the substrate 1 and does not include a film bonded (joined) to the substrate 1.

[0011] As the substrate 1, for example, a semiconductor substrate can be used. Specifically, as the substrate 1, a single crystal silicon (Si) substrate 1a having a surface oxide film (SiO2 film) 1b such as a thermal oxide film or a CVD (Chemical Vapor Deposition) oxide film, that is, an Si substrate having a surface oxide film can be preferably used. Also, as the substrate 1, instead of the surface oxide film 1b, an Si substrate 1a having an insulating film formed of an insulating material other than SiO2 can be used. Also, as the substrate 1, an Si substrate 1a having an Si(100) plane or an Si(111) plane or the like exposed on the surface, that is, an Si substrate having no surface oxide film 1b or insulating film can be used. Also, as the substrate 1, an SOI (Silicon On Insulator) substrate or a quartz glass (SiO2) substrate can be used. The thickness of the single crystal Si substrate 1a can be, for example, 300 μm or more and 1000 μm or less, and the thickness of the surface oxide film 1b can be, for example, 1 nm or more and 4000 nm or less.

[0012] The lower electrode film 2 can be formed using, for example, platinum (Pt). The lower electrode film 2 is a polycrystalline film. Hereinafter, the polycrystalline film formed using Pt is also referred to as a Pt film. It is preferable that the (111) plane of the Pt film is parallel to the main surface of the substrate 1 (including the case where the (111) plane is inclined at an angle within ±5° with respect to the main surface of the substrate 1), that is, the Pt film is oriented in the (111) plane orientation. That the Pt film is oriented in the (111) plane orientation means that no peaks other than the peak due to the (111) plane are observed in the X-ray diffraction pattern obtained by X-ray diffraction (XRD) measured on the surface of the piezoelectric film 3. Thus, it is preferable that the main surface of the lower electrode film 2 (the surface serving as the base for the piezoelectric film 3) is composed of the Pt(111) plane. The lower electrode film 2 can be formed by a method such as sputtering or vapor deposition. As materials for the lower electrode film 2, in addition to Pt, various metals such as gold (Au), ruthenium (Ru), or iridium (Ir), alloys having these as main components, metal oxides such as strontium ruthenate (SrRuO3, abbreviation: SRO) or lanthanum nickelate (LaNiO3, abbreviation: LNO), etc. can also be used. When forming the lower electrode film 2 using a metal oxide, it is preferable that the crystals constituting the lower electrode film 2 are preferentially oriented in the (001) plane orientation with respect to the surface of the substrate 1. The lower electrode film 2 can be a single-layer film formed using the above various metals, alloys having the above various metals as main components, or metal oxides, etc. The lower electrode film 2 may be a laminate of a Pt film and a film mainly composed of SRO provided on the Pt film, a laminate of a Pt film and a film mainly composed of LNO provided on the Pt film, 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.

[0013] A adhesion layer 6 may be provided between the substrate 1 and the lower electrode film 2 to enhance their adhesion. The adhesion layer 6 can be, for example, a layer mainly composed of zinc (Zn) and oxygen (O) (hereinafter also referred to as "ZnO layer"). The ZnO layer can be formed using, for example, zinc oxide. The composition ratio of Zn and O constituting the ZnO layer preferably satisfies the relationship of Zn:O = 1:1, but is not limited thereto, and there may be some variation. The ZnO layer is a polycrystalline layer. The (0001) plane of the ZnO layer is preferably parallel to the main plane of the substrate 1 (including the case where the (0001) plane is inclined at an angle within ±5° with respect to the main plane of the substrate 1), that is, the ZnO layer is preferably oriented in the (0001) plane direction. That the ZnO layer is oriented in the (0001) plane direction means that in the X-ray diffraction pattern obtained by XRD measured on the surface of the piezoelectric film 3, the intensity of the peak caused by the (0002) plane is high. Thus, the main plane of the ZnO layer (the plane serving as the base of the lower electrode film 2) is preferably composed of the ZnO (0001) plane. The ZnO layer can be formed by a method such as sputtering or vapor deposition. The thickness of the ZnO layer can be, for example, 1 nm or more and 200 nm or less, preferably 10 nm or more and 50 nm or less. As the adhesion layer 6, for example, a layer mainly composed of titanium (Ti), tantalum (Ta), titanium oxide (TiO2), nickel (Ni), ruthenium oxide (RuO2), iridium oxide (IrO2), etc. may be provided. Such an adhesion layer 6 can also be formed by a method such as sputtering or vapor deposition, and the thickness of the adhesion layer 6 can be, for example, 1 nm or more and 200 nm or less, preferably 10 nm or more and 50 nm or less. In this specification, the adhesion layer 6 provided between the substrate 1 and the lower electrode film 2 may also be referred to as the lower adhesion layer 6.

[0014] The piezoelectric film 3 is, for example, a film formed from an alkali niobate oxide containing potassium (K), sodium (Na), niobium (Nb), and oxygen (O). That is, the piezoelectric film 3 is a film mainly composed of an alkali niobate oxide containing K, Na, Nb, and O. The piezoelectric film 3 has the composition formula (K 1-x Na x)It can be formed using an alkali niobium oxide represented by NbO3, i.e., potassium sodium niobate (KNN). The coefficient x [=Na / (K+Na)] in the above composition formula can be in the range of 0 < x < 1, preferably 0.4 ≤ x ≤ 0.8. The piezoelectric film 3 becomes a polycrystalline film of KNN (hereinafter also referred to as the KNN film 3). Also, the crystal structure of KNN is a perovskite structure. That is, the KNN film 3 has a perovskite structure. Further, it is preferable that more than half of the crystals constituting the KNN film 3 have a columnar structure. In this specification, the crystal system of KNN is regarded as a tetragonal system. The KNN film 3 can be formed by a sputtering method. The thickness of the KNN film 3 can be, for example, 0.5 μm or more and 5 μm or less, preferably 1 μm or more and 3 μm or less.

[0015] The crystals constituting the KNN film 3 are preferentially oriented in the (001) plane orientation with respect to the main surface of the substrate 1 (when the substrate 1 is, for example, a Si substrate 1a having a surface oxide film 1b or an insulating film or the like, it is the Si substrate 1a). That is, the main surface of the KNN film 3 (the surface serving as the base for the upper electrode film 4) is mainly composed of the KNN (001) plane. For example, by directly forming the KNN film 3 on a Pt film (lower electrode film 2) whose main surface is mainly composed of the Pt (111) plane, a KNN film 3 whose main surface is mainly composed of the KNN (001) plane can be obtained. In this specification, that the crystals constituting the KNN film 3 are oriented in the (001) plane orientation means that the (001) plane of the crystals constituting the KNN film 3 is parallel or substantially parallel to the main surface of the substrate 1. Also, that the crystals constituting the KNN film 3 are preferentially oriented in the (001) plane orientation means that there are many crystals whose (001) plane is parallel or substantially parallel to the main surface of the substrate 1.

[0016] In addition, the alkali niobium oxide constituting the KNN film 3 may further contain at least one element (dopant) selected from the group consisting of lithium (Li), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), bismuth (Bi), antimony (Sb), vanadium (V), indium (In), tantalum (Ta), molybdenum (Mo), tungsten (W), chromium (Cr), Ti, zirconium (Zr), hafnium (Hf), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), copper (Cu), zinc (Zn), silver (Ag), manganese (Mn), iron (Fe), cobalt (Co), Ni, aluminum (Al), Si, germanium (Ge), tin (Sn), and gallium (Ga). The concentration of these elements in the alkali niobium oxide can be, for example, 5 at% or less (when a plurality of the above elements are contained, the total concentration is 5 at% or less).

[0017] The upper electrode film 4 is mainly composed of various metals such as Pt, Au, Al, Cu, or alloys thereof. The upper electrode film 4 can be formed by methods such as sputtering, vapor deposition, plating, or the metal paste method. The upper electrode film 4 does not significantly affect the crystal structure of the KNN film 3 like the lower electrode film 2. Therefore, the material, crystal structure, and film formation method of the upper electrode film 4 are not particularly limited. Note that between the KNN film 3 and the upper electrode film 4, an adhesion layer 7 mainly composed of, for example, RuO2, IrO2, Ti, Ta, TiO2, Ni, etc. may be provided to enhance their adhesion. The thickness of the upper electrode film 4 is, for example, 50 nm or more and 5000 nm or less, preferably 50 nm or more and 300 nm or less. When the adhesion layer 7 is provided, the thickness of the adhesion layer 7 can be, for example, 1 nm or more and 200 nm or less, preferably 5 nm or more and 50 nm or less. In this specification, the adhesion layer 7 provided between the KNN film 3 and the upper electrode film 4 may also be referred to as the upper adhesion layer 7.

[0018] Although it will be described in detail later, in this embodiment, the KNN film 3 is formed under the conditions of low temperature, high oxygen partial pressure, and low ambient pressure during the manufacturing process of the laminate 10. As a result, the laminate 10 in this embodiment has both Feature 1 and Feature 2 described later. In addition, the laminate 10 in this embodiment may further have Feature 3 described later. Hereinafter, various features that the laminate 10 of this embodiment may have will be described.

[0019] (Feature 1) When forming the KNN film 3, alkali metals (potassium atoms, sodium atoms) may diffuse to the substrate 1 through the lower electrode film 2 (and the lower adhesion layer 6). When the alkali metal diffuses to the substrate 1, the adhesion between the substrate 1 and the lower electrode film 2 (the lower adhesion layer 6 if it has one) may decrease. As a result, when the piezoelectric element 20 (piezoelectric device module 30) described later obtained by processing the laminate 10 is driven, if an excessive external force is repeatedly applied to the periphery (member) of the lower electrode film 2 due to the KNN film 3 repeatedly deforming greatly, etc., the lower electrode film 2 and thus the KNN film 3 may peel off from the substrate 1.

[0020] In response to such problems, in this aspect, during the production process of the laminate 10, the KNN film 3 is formed at a low temperature. As a result, it has been successful in suppressing the diffusion of alkali metals into the substrate 1. Specifically, when the surface layer region of the substrate 1 in the laminate 10 of this aspect is analyzed by Secondary Ion Mass Spectrometry (SIMS), the potassium concentration (K concentration) is 5E15 cm -3 or less, and the sodium concentration (Na concentration) is 5E15 cm -3 or less, having the characteristic (Characteristic 1).

[0021] In this way, by forming the KNN film 3 at a low temperature, it is possible to suppress the diffusion of alkali metals into the substrate 1, and it is a new finding first discovered as a result of the intensive studies by the present inventors that a laminate 10 with a low K concentration and Na concentration in the surface layer region of the substrate 1 can be obtained.

[0022] In addition, the "surface layer region of the substrate 1" in this specification refers to the region ranging from the upper surface of the substrate 1 (when the substrate 1 has the surface oxide film 1b, from the upper surface of the surface oxide film 1b) to a depth of 1 μm in the thickness direction of the substrate 1 (toward the lower surface of the substrate 1). Also, the "upper surface of the substrate 1" is the surface on which the lower electrode film 2 etc. is formed among the two main surfaces of the substrate 1, and the "lower surface of the substrate 1" is the surface on the opposite side of the upper surface of the substrate 1 among the two main surfaces of the substrate 1.

[0023] When the K concentration and the Na concentration in the surface layer region of the substrate 1 are each 5E15 cm -3 or less, the adhesion between the substrate 1 and the lower electrode film 2 (or the lower adhesion layer 6) can be improved. As a result, even if an excessive external force is repeatedly applied to the periphery of the lower electrode film 2 during the driving of the piezoelectric element 20 (piezoelectric device module 30) described later, peeling of the lower electrode film 2 and thus the KNN film 3 from the substrate 1 can be avoided. As a result, it becomes possible to improve the reliability of the piezoelectric element 20 (piezoelectric device module 30).

[0024] The lower the K concentration and Na concentration in the surface layer region of the substrate 1, the more the adhesion between the substrate 1 and the lower electrode film 2 (or the lower adhesion layer 6) can be improved. The K concentration and Na concentration in the surface layer region of the substrate 1 are each preferably 3E14 cm -3 or less, which enables further improvement of the adhesion. Further, the K concentration in the surface layer region of the substrate 1 is more preferably, for example, 1E14 cm -3 or less, which enables further improvement of the adhesion.

[0025] The lower limit values of the K concentration and Na concentration in the surface layer region of the substrate 1 are not particularly limited. The detection limit of the K concentration by SIMS analysis at present is about 1E14 cm -3 or so, and the detection limit of the Na concentration is about 3E14 cm -3 or so.

[0026] (Feature 2) When the KNN film 3 is formed at a low temperature, although the diffusion of the alkali metal into the substrate 1 can be suppressed, the (001) orientation ratio of the KNN film 3 may decrease.

[0027] To address such problems, in this aspect, in the process of manufacturing the laminate 10, the KNN film 3 is formed under the conditions of low temperature, high oxygen partial pressure, and low ambient pressure. That is, not only is the film formation condition of the KNN film 3 set to a low temperature, but also a high oxygen partial pressure and a low ambient pressure are set. As a result, even when the film is formed at a low temperature, a KNN film 3 with a high (001) orientation ratio (high crystal orientation) has been successfully obtained. This is a new finding first discovered as a result of the intensive studies by the inventors of the present invention.

[0028] Specifically, in addition to Feature 1, the laminate 10 further has a feature (Feature 2) that the (001) orientation ratio of the KNN film 3 is, for example, 96% or more, preferably 98% or more.

[0029] Note that the (001) orientation ratio of the KNN film 3 is the orientation ratio of the crystals constituting the KNN film 3 in the (001) plane orientation. "The (001) orientation ratio of the KNN film 3 is 96% or more" means that, for example, 96% or more of the crystals constituting the KNN film 3 are oriented in the (001) plane orientation with respect to the main surface of the substrate 1. Note that the "orientation ratio" in this specification is a value calculated by the following formula (1) based on the peak intensity of the X-ray diffraction pattern (2θ / θ) obtained by performing XRD measurement on the KNN film 3.

[0030] Orientation ratio (%) = {(001) peak intensity / ((001) peak intensity + (110) peak intensity)} × 100 ··· (1)

[0031] The "(001) peak intensity" in the above formula (1) is the intensity of the diffraction peak caused by the crystals oriented in the (001) plane orientation among the crystals constituting the KNN film 3 (that is, the crystals whose (001) plane is parallel to the main surface of the substrate 1) in the X-ray diffraction pattern obtained by performing XRD measurement on the KNN film 3, and is the intensity of the peak appearing in the range of 2θ from 20° to 23°. When a plurality of peaks appear in the range of 2θ from 20° to 23°, it is the intensity of the highest peak. Also, the "(110) peak intensity" in the above formula (1) is the intensity of the diffraction peak caused by the crystals oriented in the (110) plane orientation among the crystals constituting the KNN film 3 (that is, the crystals whose (110) plane is parallel to the main surface of the substrate 1) in the X-ray diffraction pattern obtained by performing XRD measurement on the KNN film 3, and is the intensity of the peak appearing in the range of 2θ from 30° to 33°. Note that when a plurality of peaks appear in the range of 2θ from 30° to 33°, it is the intensity of the highest peak.

[0032] Note that in order to exhibit this feature, the KNN film 3 needs to have a perovskite structure. This is because when the KNN film 3 does not have a perovskite structure, no peak can be observed in the X-ray diffraction pattern obtained by performing XRD measurement at least in the range of 2θ from 20° to 23°, and as a result, the (001) orientation ratio cannot be calculated.

[0033] (Feature 3) In this embodiment, in the process of manufacturing the laminate 10, the KNN film 3 is formed under the conditions of low temperature, high oxygen partial pressure, and low atmospheric pressure. As a result, even when the film is formed at a low temperature, the KNN film 3 with a high (001) orientation ratio has been successfully obtained. As a result, it is also possible to obtain the KNN film 3 with a high piezoelectric constant.

[0034] Specifically, in addition to the above-mentioned features 1 and 2, the laminate 10 further has a feature (feature 3) that the absolute value of the piezoelectric constant e 31 of the KNN film 3 is, for example, 7 C / m 2 or more, preferably 10 C / m 2 or more.

[0035] (2) Configuration of the piezoelectric element and the piezoelectric device module FIG. 2 shows a schematic configuration diagram of an element (device) 20 (an element 20 having the KNN film 3, hereinafter also referred to as the piezoelectric element 20) obtained by shaping the above-mentioned laminate 10 into a predetermined shape by etching or the like. In this specification, the piezoelectric element 20 shown in FIG. 2 is also referred to as a simple piezoelectric element 20a.

[0036] The piezoelectric element 20 may have a membrane structure, a cantilever structure, or the like. As an example of such a piezoelectric element 20, FIG. 3 shows a schematic configuration diagram of a membrane-type MEMS piezoelectric element 20b obtained by further shaping the simple piezoelectric element 20a. The piezoelectric element 20b is obtained by performing Deep-RIE or wet etching on the simple piezoelectric element 20a and removing a part of the substrate 1 from the back surface side of the substrate 1 (the side opposite to the surface on which the lower electrode film 2 and the like are formed among the two main surfaces of the substrate 1). The piezoelectric element 20b further includes an insulating film 8 and metal wirings 9a and 9b.

[0037] The metal wiring 9a is provided so as to be connected to (in contact with) the lower electrode film 2 and not connected to (not in contact with) the upper electrode film 4. Further, the metal wiring 9b is provided so as to be connected to the upper electrode film 4 and not connected to the lower electrode film 2. The metal wirings 9a and 9b can each be formed using various metals such as Au, Al, Ti, Cr, or alloys mainly composed of these various metals. The metal wirings 9a and 9b may be single-layer films or laminated bodies formed by laminating a plurality of layers. The metal wirings 9a and 9b can be formed into films by methods such as sputtering, vapor deposition, plating, and the metal paste method.

[0038] The insulating film 8 is provided so as to insulate between the metal wiring 9b and the lower electrode film 2. The insulating film 8 is provided from the upper electrode film 4 to the substrate 1 so as to cover a part of the side surface of, for example, the KNN film 3. The insulating film 8 can be formed using oxides such as silicon oxide (SiO2), aluminum oxide (Al2O3), and tantalum oxide (Ta2O5). The insulating film 8 may be a single-layer film or a laminated body formed by laminating a plurality of layers. The insulating film 8 can be formed into a film by methods such as CVD and sputtering.

[0039] FIG. 4 shows a schematic configuration diagram of a device module 30 having the KNN film 3 according to this aspect (hereinafter, also referred to as a piezoelectric device module 30). The piezoelectric device module 30 includes at least the piezoelectric element 20b shown in FIG. 3 and a voltage application unit 11a or a voltage detection unit 11b connected to the piezoelectric element 20b. Note that the piezoelectric device module 30 may include the simple piezoelectric element 20a shown in FIG. 2 instead of the piezoelectric element 20b shown in FIG. 3.

[0040] 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 the voltage generated between the lower electrode film 2 and the upper electrode film 4 (between the electrodes). As the voltage application unit 11a and the voltage detection unit 11b, various known means can be used.

[0041] 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 with the voltage application unit 11a, the KNN film 3 can be deformed. By this deformation operation, various members connected to the piezoelectric device module 30 can be actuated. In this case, examples of the applications of the piezoelectric device module 30 include a head for an inkjet printer, a MEMS mirror for a scanner, a vibrator for an ultrasonic generator, and the like.

[0042] 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 with 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, the magnitude of the physical quantity applied to the KNN film 3 can be measured. In this case, examples of the applications of the piezoelectric device module 30 include an angular velocity sensor, an ultrasonic sensor, a pressure sensor, an acceleration sensor, and the like.

[0043] (3) Manufacturing method of piezoelectric laminate, piezoelectric element, and piezoelectric device module The manufacturing methods of the above-described laminate 10, piezoelectric element 20, and piezoelectric device module 30 will be described.

[0044] (Preparation of substrate) First, as the substrate 1, a Si substrate having a surface oxide film 1b is prepared.

[0045] (Film formation of lower adhesion layer and lower electrode film) On the surface oxide film 1b of the substrate 1, a lower adhesion layer 6 (e.g., ZnO layer) and a lower electrode film 2 (e.g., Pt film) are formed in this order by, for example, sputtering. Note that a substrate 1 on which the lower adhesion layer 6 or the lower electrode film 2 is previously formed on either main surface may be prepared.

[0046] As conditions for forming the ZnO layer as the lower adhesion layer 6, the following conditions are exemplified. The film formation time of the lower adhesion layer 6 is appropriately adjusted according to the target thickness of the lower adhesion layer 6. Target: ZnO sintered body Temperature (substrate temperature): 200°C or higher and 700°C or lower, preferably 300°C or higher and 700°C or lower, more preferably 500°C or higher and 700°C or lower Discharge power density: 2 W / cm 2 Up to 6 W / cm 2 Preferably 3 W / cm or more 2 Up to 5 W / cm 2 Or less Atmosphere: Atmosphere of a mixed gas of argon (Ar) gas and oxygen (O2) gas (hereinafter, also referred to as "Ar / O2 mixed gas atmosphere") Ratio of partial pressure of Ar gas to O2 gas (Ar gas partial pressure / O2 gas partial pressure): 5 / 1 to 30 / 1, preferably 7 / 1 to 20 / 1, more preferably 10 / 1 to 15 / 1 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 Thickness: 1 nm or more and 200 nm or less, preferably 10 nm or more and 50 nm or less

[0047] The notation of a numerical range such as "5 / 1 to 30 / 1" in this specification means that the lower limit value and the upper limit value are included in that range. The same applies to other numerical ranges. Also, the "substrate temperature" in this specification means the surface temperature of the substrate 1 during the film formation of each film (each layer).

[0048] In addition, as conditions for forming a Ti layer or the like as the lower adhesion layer 6, the following conditions are exemplified. Target: Ti plate or the like Temperature (substrate temperature): 100°C or higher and 500°C or lower, preferably 200°C or higher and 400°C or lower 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 Other conditions can be the same as the conditions for providing the ZnO layer.

[0049] When forming the Pt film as the lower electrode film 2, the following conditions are exemplified. The film formation time of the lower electrode film 2 is appropriately adjusted according to the target thickness of the lower electrode film 2. Target: Pt plate Temperature (substrate temperature): 200 °C or higher and 600 °C or lower, preferably 300 °C or higher and 500 °C or lower Discharge power density: 1 W / cm 2 or more and 5 W / cm 2 or less, preferably 2 W / cm 2 or more and 4 W / cm 2 or less Atmosphere: Ar gas atmosphere Atmospheric pressure: 0.1 Pa or higher and 0.5 Pa or lower, preferably 0.2 Pa or higher and 0.4 Pa or lower Thickness: 100 nm or more and 400 nm or less

[0050] (Film formation of KNN film) When the film formation of the lower adhesion layer 6 and the lower electrode film 2 is completed, subsequently, the KNN film 3 is formed on the lower electrode film 2 by a sputtering method such as the RF magnetron sputtering method. The composition of the KNN film 3 can be adjusted, for example, by controlling the composition of the target used during sputter film formation. The target can be produced by, for example, mixing K2CO3 powder, Na2CO3 powder, Nb2O5 powder, etc. and firing them. The composition of the target can be controlled by adjusting the mixing ratio of K2CO3 powder, Na2CO3 powder, Nb2O5 powder, etc. When forming the KNN film 3 containing the above-mentioned elements such as Cu and Mn, a target in which Cu powder (or CuO powder), Mn powder (or MnO powder), etc. are mixed in a predetermined ratio may be used in addition to the above-mentioned respective powders.

[0051] In this embodiment, the film formation conditions of the KNN film 3 are set at a low temperature, the oxygen partial pressure is increased, and further, the atmospheric pressure is decreased. Specifically, when forming the KNN film 3, the following conditions are exemplified. The film formation time of the KNN film 3 is appropriately adjusted according to the target thickness of the KNN film 3. Temperature (substrate temperature): 400 °C or higher and less than 500 °C, more preferably 400 °C or higher and 450 °C or lower Atmosphere: Ar / O2 mixed gas atmosphere Oxygen partial pressure (O2 gas partial pressure) in the atmosphere: 0.0025 Pa or more and less than 0.01 Pa, preferably 0.003 Pa or more and less than 0.01 Pa Atmospheric pressure (chamber pressure): 0.03 Pa or more and less than 0.1 Pa, preferably 0.03 Pa or more and 0.08 Pa or less Discharge power density: 2.7 W / cm 2 Up to 4.1 W / cm 2 Below, preferably 2.8 W / cm 2 Above 3.8 W / cm 2 Below Film deposition rate: 0.5 μm / hr or more and 4 μm / hr or less, preferably 0.5 μm / hr or more and 2 μm / hr or less Thickness: 0.5 μm or more and 5 μm or less, preferably 1 μm or more and 3 μm or less

[0052] By depositing the KNN film 3 under the above conditions, particularly by depositing the KNN film 3 with the film deposition temperature, oxygen partial pressure, and atmospheric pressure within the ranges of the above predetermined conditions, the K concentration and Na concentration in the surface layer region of the substrate 1 can each be 5E15 cm -3 Below, and a laminate 10 with an (001) orientation ratio of the KNN film 3 of 96% or more can be obtained. That is, a laminate 10 having both of the above characteristics 1 and 2 can be obtained.

[0053] Particularly, by depositing the KNN film 3 with the film deposition temperature within the range of the above predetermined conditions, it becomes possible to suppress the diffusion of alkali metals into the substrate 1. As a result, the K concentration and Na concentration in the surface layer region of the substrate 1 can each be 5E15 cm -3 Below. That is, it becomes possible to obtain a laminate 10 having the above characteristic 1.

[0054] When the film deposition temperature of the KNN film 3 is 500 °C or higher, it may not be possible to suppress the diffusion of alkali metals into the substrate 1.

[0055] When the film formation temperature of the KNN film 3 is less than 500°C, the diffusion of alkali metals can be suppressed, and the K concentration and the Na concentration in the surface layer region of the substrate 1 can be reduced respectively. As a result, the K concentration and the Na concentration in the surface layer region of the substrate 1 can be reduced to 5E15 cm -3 or less. Further, when the film formation temperature of the KNN film 3 is, for example, 450°C or less, the diffusion of alkali metals can be surely suppressed, and the K concentration and the Na concentration in the surface layer region of the substrate 1 can be further reduced. For example, the K concentration and the Na concentration in the surface layer region of the substrate 1 can be reduced to 3E14 cm -3 or less, and furthermore, the K concentration in the surface layer region of the substrate 1 can be reduced to 1E14 cm -3 or less.

[0056] When the film formation temperature of the KNN film 3 is less than 400°C, while the effect of suppressing the diffusion of alkali metals into the substrate 1 reaches a peak, the (001) orientation ratio of the KNN film 3 may decrease. As a result, even if the oxygen partial pressure and the atmospheric pressure during the film formation of the KNN film 3 are within the range of predetermined conditions, the (001) orientation ratio of the KNN film 3 may not be able to reach 96% or more.

[0057] When the film formation temperature of the KNN film 3 is 400°C or more, it becomes possible to surely obtain the KNN film 3 having a (001) orientation ratio of 96% or more while suppressing the diffusion of alkali metals into the substrate 1. That is, it becomes possible to obtain the laminate 10 having both the above-mentioned feature 1 and feature 2.

[0058] Further, when the oxygen partial pressure during the film formation of the KNN film 3 is less than 0.0025 Pa, the (001) orientation ratio of the KNN film 3 may not be sufficiently increased. Therefore, when the oxygen partial pressure is less than 0.0025 Pa in the case where the film formation temperature of the KNN film 3 is 400°C or more and less than 500°C, the (001) orientation ratio of the KNN film 3 may not be able to reach 96% or more. As a result, the absolute value of the piezoelectric constant e 31 may not be able to reach 7 C / m 2 or more.

[0059] When the oxygen partial pressure is 0.0025 Pa or more, the (001) orientation ratio of the KNN film 3 can be sufficiently increased, and even when the film formation temperature of the KNN film 3 is 400 °C or more and less than 500 °C, the (001) orientation ratio of the KNN film 3 can be made 96% or more. That is, it becomes possible to obtain the laminate 10 having both the above-described features 1 and 2. Further, when the oxygen partial pressure is 0.0025 Pa or more, even if the film formation temperature of the KNN film 3 is 400 °C or more and less than 500 °C, the piezoelectric constant e 31 of the KNN film 3 can also be made 7 C / m 2 or more in absolute value. That is, it becomes possible to obtain the laminate 10 having all of the above-described features 1 to 3. When the oxygen partial pressure is 0.003 Pa or more, the (001) orientation ratio of the KNN film 3 can be further increased, and the (001) orientation ratio of the KNN film 3 can be made 98% or more, or the piezoelectric constant e 31 of the KNN film 3 can also be made 10 C / m 2 or more in absolute value.

[0060] When the oxygen partial pressure is 0.01 Pa or more, since the sputtering energy required for crystallization of the KNN film 3 is taken away by ionization of oxygen, the (001) orientation ratio of the KNN film 3 tends to decrease. Therefore, when the film formation temperature is 400 °C or more and less than 500 °C and the oxygen partial pressure is 0.01 Pa or more, the (001) orientation ratio of the KNN film 3 may not be able to be made 96% or more. As a result, the absolute value of the piezoelectric constant e 31 may not be able to be made 7 C / m 2 or more.

[0061] When the oxygen partial pressure is less than 0.01 Pa, a decrease in the (001) orientation ratio of the KNN film 3 can be suppressed, and even when the film formation temperature of the KNN film 3 is 400 °C or more and less than 500 °C, the (001) orientation ratio of the KNN film 3 can be made 96% or more. That is, it becomes possible to obtain the laminate 10 having both the above-described features 1 and 2. Further, when the oxygen partial pressure is less than 0.01 Pa, even if the film formation temperature of the KNN film 3 is 400 °C or more and less than 500 °C, the absolute value of the piezoelectric constant e 31 can also be made 7 C / m 2 or more.

[0062] In addition, when the atmospheric pressure during the formation of the KNN film 3 is 0.1 Pa or more, the (001) orientation ratio of the KNN film 3 may not be sufficiently increased. Therefore, when the film formation temperature of the KNN film 3 is 400 °C or more and less than 500 °C and the atmospheric pressure is 0.1 Pa or more, the (001) orientation ratio of the KNN film 3 may not be able to reach 96% or more. As a result, the absolute value of the piezoelectric constant e 31 may not be able to reach 7 C / m 2 or more.

[0063] When the atmospheric pressure is less than 0.1 Pa, the (001) orientation ratio of the KNN film 3 can be sufficiently increased, and the (001) orientation ratio of the KNN film 3 can be made 96% or more. That is, it becomes possible to obtain the laminate 10 having both the above-described feature 1 and feature 2. In addition, when the atmospheric pressure is less than 0.1 Pa, the absolute value of the piezoelectric constant e 31 of the KNN film 3 can also be made 7 C / m 2 or more. Further, when the atmospheric pressure is 0.08 Pa or less, the (001) orientation ratio of the KNN film 3 can be further increased, the (001) orientation ratio of the KNN film 3 can be made 98% or more, or the absolute value of the piezoelectric constant e 31 of the KNN film 3 can be made 10 C / m 2 or more.

[0064] In addition, when the atmospheric pressure is less than 0.03 Pa, the (001) orientation ratio of the KNN film 3 may not be sufficiently increased. Therefore, when the film formation temperature of the KNN film 3 is 400 °C or more and less than 500 °C and the atmospheric pressure is less than 0.03 Pa, the (001) orientation ratio of the KNN film 3 may not be able to reach 96% or more. As a result, the absolute value of the piezoelectric constant e 31 may not be able to reach 7 C / m 2 or more.

[0065] When the atmospheric pressure is 0.03 Pa or more, the (001) orientation ratio of the KNN film 3 can be sufficiently increased, and even when the film formation temperature of the KNN film 3 is 400 °C or more and less than 500 °C, the (001) orientation ratio of the KNN film 3 can be made 96% or more. That is, it becomes possible to obtain the laminate 10 having both the above-described feature 1 and feature 2. Further, when the atmospheric pressure is 0.03 Pa or more, the absolute value of the piezoelectric constant e 31 of the KNN film 3 can also be made 7 C / m 2 or more.

[0066] As described above, only by forming the KNN film 3 with all of the film formation temperature, oxygen partial pressure, and atmospheric pressure within the range of the above-described predetermined conditions, the laminate 10 having both the above-described feature 1 and feature 2, and further, the laminate 10 having all of the above-described feature 1, feature 2, and feature 3 can be obtained. If at least any one of the conditions of the film formation temperature, oxygen partial pressure, and atmospheric pressure is outside the range of the above conditions, the laminate having both the above-described feature 1 and feature 2 may not be obtained.

[0067] (Film Formation of Upper Adhesion Layer and Upper Electrode Film) When the film formation of the KNN film 3 is completed, an upper adhesion layer 7 (for example, RuO2 layer) and an upper electrode film 4 (for example, Pt film) are formed in this order on the KNN film 3 by, for example, a sputtering method.

[0068] The following conditions are exemplified as the conditions for forming an RuO2 layer or the like as the upper adhesion layer 7. The film formation time of the upper adhesion layer 7 is appropriately adjusted according to the target thickness of the upper adhesion layer 7. Target: Ru plate, etc. Temperature (substrate temperature): Room temperature (25 °C) or more and less than 500 °C, preferably room temperature (25 °C) or more and 450 °C or less Discharge power density: 0.3 W / cm 2 or more and 2 W / cm 2 or less, preferably 0.5 W / cm 2 or more and 1 W / cm 2 or less Atmosphere: Ar / O2 mixed gas atmosphere Ratio of partial pressure of Ar gas to O2 gas (Ar gas partial pressure / O2 gas partial pressure): 3 / 5 to 1 / 1, preferably 3 / 4 to 1 / 1 Atmospheric pressure: 0.1 Pa or more and 1.0 Pa or less, preferably 0.2 Pa or more and 0.7 Pa or less Thickness: 1 nm or more and 200 nm or less, preferably 5 nm or more and 50 nm or less

[0069] As conditions for forming a Pt film or the like as the upper electrode film 4, the following conditions are exemplified. The film formation time of the upper electrode film 4 is appropriately adjusted according to the target thickness of the upper electrode film 4. Target: Pt plate or the like Temperature (substrate temperature): room temperature (25 °C) or more and less than 500 °C, preferably room temperature (25 °C) or more and 450 °C or less Discharge power density: 1 W / cm 2 to 5 W / cm 2 or less, preferably 2 W / cm 2 or more and 4 W / cm 2 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 Thickness: 50 nm or more and 5000 nm or less, preferably 50 nm or more and 300 nm or less

[0070] By forming the upper adhesion layer 7 and the upper electrode film 4 under the above conditions, particularly by forming the upper adhesion layer 7 and the upper electrode film 4 with the film formation temperature within the range of the above predetermined conditions, diffusion of alkali metal into the substrate 1 can be more reliably suppressed. As a result, the laminate 10 in which the K concentration and the Na concentration in the surface layer region of the substrate 1 are each 5E15 cm -3 or less can be more reliably obtained.

[0071] As described above, by sequentially forming the lower adhesion layer 6, the lower electrode film 2, the KNN film 3, the upper adhesion layer 7, and the upper electrode film 4, a laminate 10 as shown in FIG. 1 is obtained.

[0072] (Fabrication of piezoelectric element) After manufacturing the laminate 10 as shown in FIG. 1, the laminate 10 is processed to manufacture the simple piezoelectric element 20a.

[0073] Specifically, first, for example, by dry etching using Ar gas or a reactive gas, the upper electrode film 4 (including the upper adhesion layer 7) and the KNN film 3 are individually patterned. In the patterning process, the upper electrode film 4 (including the upper adhesion layer 7) and the KNN film 3 are each formed into a predetermined shape, and a part of the lower electrode film 2 is exposed. Also, in the patterning process, a photoresist can be used as an etching mask.

[0074] After manufacturing the simple piezoelectric element 20a as shown in FIG. 2, for example, by dry etching using Ar gas or a reactive gas, the lower electrode film 2 and the lower adhesion layer 6 are each patterned, and the lower electrode film 2 and the lower adhesion layer 6 are each formed into a predetermined shape. In this patterning process, a photoresist can be used as an etching mask.

[0075] After the patterning of the lower electrode film 2 and the lower adhesion layer 6 is completed, the insulating film 8 and the metal wirings 9a and 9b are provided. Specifically, first, a layer made of an insulating material (that is, the insulating film 8) is provided from the upper electrode film 4 to the substrate 1 so as to cover the side surface of the KNN film 3 by a method such as CVD method or sputtering method. Then, the insulating film 8 is patterned by dry etching using Ar gas or a reactive gas such as CF4 gas, or wet etching, and the insulating film 8 is formed into a predetermined shape.

[0076] After providing the insulating film 8, a layer made of a material containing metal (metal wiring layer) is provided by a method such as sputtering method, vapor deposition method, plating method, metal paste method, etc. Then, dry etching using Ar gas or reactive gas, or wet etching is performed on the metal wiring layer to perform pattern processing, and metal wirings 9a and 9b are formed. The metal wiring 9a is formed (patterned) so as to be connected to the lower electrode film 2 and not connected to the upper electrode film 4, and the metal wiring 9b is formed so as to be connected to the upper electrode film 4 and not connected to the lower electrode film 2.

[0077] Note that the etching conditions in the pattern processing when forming the insulating film 8 and the metal wirings 9a and 9b, and the etching conditions of the substrate 1 when processing the piezoelectric laminate 10 into the piezoelectric element 20 can be general etching conditions used in the semiconductor device manufacturing process as long as the insulating property of the KNN film 3 is not deteriorated.

[0078] Also, a part of the substrate 1 is removed from the back side of the substrate 1 by Deep-RIE or wet etching. Thereby, a piezoelectric element 20b as shown in FIG. 3 is obtained.

[0079] (Fabrication of piezoelectric device module) By connecting the voltage application unit 11a or the voltage detection unit 11b to the obtained piezoelectric element 20 (20b), a device module 30 having the KNN film 3 (hereinafter, also referred to as the piezoelectric device module 30) is obtained.

[0080] (4) Effects According to this aspect, one or more of the following effects can be obtained.

[0081] (a) In this aspect, in the manufacturing process of the laminate 10, the KNN film 3 is formed under the conditions that the film formation temperature is 400 ° C or more and less than 500 ° C, the oxygen partial pressure is 0.0025 Pa or more and less than 0.01 Pa, and the atmospheric pressure is 0.03 Pa or more and less than 0.1 Pa.

[0082] By forming the KNN film 3 with the film formation temperature being 400 °C or higher and less than 500 °C, diffusion of alkali metals into the substrate 1 can be suppressed. As a result, the obtained laminate 10 can have a feature (feature 1) that "the K concentration and the Na concentration in the surface layer region of the substrate 1 are each 5E15 cm -3 or less".

[0083] Also, by forming the KNN film 3 with the oxygen partial pressure and the ambient pressure within the ranges of the above-described predetermined conditions, a KNN film 3 with a high (001) orientation ratio can be obtained while forming the KNN film 3 at a low temperature (400 °C or higher and less than 500 °C). As a result, the obtained laminate 10 can further have a feature (feature 2) that "the (001) orientation ratio of the KNN film 3 is 96% or higher".

[0084] Thus, by forming the KNN film 3 with all of the film formation temperature, the oxygen partial pressure, and the ambient pressure within the ranges of the above-described predetermined conditions, the obtained laminate 10 can have both of the above feature 1 and feature 2.

[0085] Since the laminate 10 has the above feature 1, it becomes possible to improve the adhesion between the substrate 1 and the lower electrode film 2 (lower adhesion layer 6). Thereby, when the piezoelectric element 20 (piezoelectric device module 30) is driven, even if an excessive external force is repeatedly applied to the periphery (member) of the lower electrode film 2 due to the KNN film 3 repeatedly deforming greatly, peeling of the lower electrode film 2 and thus the KNN film 3 from the substrate 1 can be avoided. As a result, it becomes possible to improve the reliability of the piezoelectric element 20 and thus the piezoelectric device module 30.

[0086] Also, since the laminate 10 has both feature 1 and feature 2, it becomes possible to obtain a laminate 10 (piezoelectric element 20, piezoelectric device module 30) with high reliability and excellent piezoelectric characteristics.

[0087] (b) By forming the KNN film 3 with all of the film formation temperature, oxygen partial pressure, and atmospheric pressure within the range of the above-described predetermined conditions, it becomes possible to obtain the KNN film 3 having a high piezoelectric constant while forming the KNN film 3 at a low temperature. As a result, in addition to the above characteristics 1 and 2, the laminate 10 has a characteristic (characteristic 3) that "the absolute value of the piezoelectric constant e 31 of the KNN film 3 is, for example, 7 C / m 2 or more". Thereby, the KNN film 3 and thus the laminate 10 can surely have excellent piezoelectric characteristics.

[0088] It has also been proposed to fabricate a piezoelectric laminate using a bonding (joining) method. That is, a method of fabricating a piezoelectric laminate by depositing a first electrode film, a KNN film, and a second electrode film in this order on a first substrate, bonding a second substrate to the upper surface of the second electrode film, and then removing the first substrate has also been proposed. In the piezoelectric laminate fabricated using the bonding method, it is considered that the alkali metal has not diffused into the second substrate. In addition, in the piezoelectric laminate fabricated using this method, the second electrode film functions as a lower electrode film, and the first electrode film functions as an upper electrode film. However, in the piezoelectric laminate fabricated by such a method using bonding, there is a problem that the adhesion between the substrate (second substrate) and the lower electrode film (second electrode film) is very low. Further, in the method using bonding, since the number of manufacturing steps of the piezoelectric laminate increases, there are also concerns such as complication of the manufacturing process, reduction in productivity, and cost increase. On the other hand, in this aspect, the laminate 10 is fabricated without using the bonding method, and further, in the manufacturing process thereof, the diffusion of the alkali metal into the substrate 1 is suppressed. As a result, the adhesion between the substrate 1 and the lower electrode film 2 (lower adhesion layer 6) has been successfully improved. In addition, since the laminate 10 is fabricated without using the bonding method, the laminate 10 (and thus the piezoelectric element 20 and the piezoelectric device module 30) according to this aspect has no traces derived from bonding. That is, in the laminate 10 (and thus the piezoelectric element 20 and the piezoelectric device module 30) according to this aspect, there are no traces derived from bonding at the interface between the substrate 1 and the KNN film 3, at the interface between the substrate 1 and the lower electrode film 2 (lower adhesion layer 6 when having the lower adhesion layer 6), or at the interface between the lower electrode film 2 and the KNN film 3. Here, the "traces derived from bonding" include the presence (distribution) of inclusions (e.g., adhesives) used for bonding and the presence (distribution) of impurities not derived from the film deposition process (e.g., impurities derived from adhesives).

[0089] (5) Modified Example This aspect can be modified as in the following modification examples. In the description of the following modification examples, the same reference numerals are given to the same components as those in the above aspect, and the description thereof is omitted. Further, the above aspect and the following modification examples can be arbitrarily combined.

[0090] (Modification Example 1) As the substrate 1, for example, it is also possible to use a semiconductor substrate for which it is required to reduce the thermal history. Specifically, as the substrate 1, it is also possible to use a semiconductor substrate (for example, a Si substrate) on which semiconductor elements are formed on any one of the main surfaces.

[0091] The semiconductor element may include, for example, a p-type MOSFET and an n-type MOSFET, and may have a CMOS (Complementary Metal Oxide Semiconductor) structure in which these function complementarily. Further, a protective film such as an oxide film or a nitride film for protecting the semiconductor element may be further formed on the substrate 1, or the protective film may be considered to be included in the semiconductor element. Note that various known methods can be used for forming the semiconductor element. Further, for forming the n-type region and the p-type region of the semiconductor element, methods such as a method of thermally diffusing a dopant and a method of activating ions by ion implantation and annealing can be used.

[0092] Further, when the substrate 1 has a surface oxide film 1b or an insulating film, in this modification example, the surface oxide film 1b or the insulating film is formed on the upper surface of the substrate 1 (the surface of the substrate 1 on which the semiconductor element is formed) except for the formation location of the semiconductor element.

[0093] Also, in this modified example, the lower electrode film 2 is formed at a position on the upper surface of the substrate 1 that is different from the formation location of the semiconductor element (on the surface oxide film 1b or the insulating film when the substrate 1 has a surface oxide film 1b or an insulating film, etc.). Therefore, the piezoelectric element 20 can be formed at a position on the upper surface of the substrate 1 that is different from the formation position of the semiconductor element. Also, the piezoelectric element 20 can be formed on the semiconductor element (on the protective film). In these cases, the surface layer region of the substrate 1 is a region extending from the interface between the piezoelectric element 20 and the substrate 1 or the interface between the piezoelectric element 20 and the semiconductor element (protective film) to a depth of 1 μm toward the back surface of the substrate 1.

[0094] Also in this modified example, in the process of manufacturing the laminate 10, by forming the KNN film 3 with all of the film formation temperature, oxygen partial pressure, and atmospheric pressure within the range of the above-described predetermined conditions, it is possible to increase the (001) orientation ratio of the KNN film while suppressing the diffusion of the alkali metal into the substrate 1. As a result, the same effects as those of the above-described aspect are obtained. That is, a laminate 10 having at least both of Feature 1 and Feature 2 is obtained.

[0095] Note that the CMOS structure formed using the above-described method is vulnerable to heat. For example, when the n-type region or the p-type region is heated, the dopant may migrate and the dopant concentration may change. In this modified example, since the KNN film 3 is formed at a low temperature of 400 °C or higher and less than 500 °C, it is possible to form the semiconductor element and the piezoelectric element on the same substrate 1 while reducing the thermal history of the semiconductor element. Also, by reducing the thermal history of the semiconductor element, it is possible to suppress the shortening of the life and the deterioration of the performance of the semiconductor element.

[0096] Also, in this modified example, it is preferable that the film formation temperatures of the lower electrode film 2 and the lower adhesion layer 6 are each less than 500°C. Specifically, the film formation temperature of the lower electrode film 2 is, for example, 200°C or higher and less than 500°C, preferably 300°C or higher and 450°C or lower. When forming a ZnO layer as the lower adhesion layer 6, the film formation temperature is, for example, 200°C or higher and less than 500°C, preferably 300°C or higher and 450°C or lower, more preferably 400°C or higher and 450°C or lower. When forming a Ti layer or the like as the lower adhesion layer 6, the film formation temperature is preferably, for example, 100°C or higher and less than 500°C, preferably 200°C or higher and 400°C or lower. Thereby, the thermal history for the semiconductor element can be surely reduced, and the shortening of the life and the deterioration of the performance of the semiconductor element can be surely suppressed.

[0097] (Modified Example 2) In the above-described modified example 1, an example in which the semiconductor element has a CMOS structure has been described. However, the semiconductor element is not limited to CMOS as long as it has an element structure that is vulnerable to heat. Elements formed by using techniques such as thermal diffusion or ion implantation of dopants for the formation of the n-type region or the p-type region are vulnerable to heat. Therefore, when the semiconductor element is formed by using these techniques, that is, when the semiconductor element has either a region in which a p-type or n-type dopant is thermally diffused or a region in which the dopant is ion implanted, this aspect can also be preferably applied, and the same effects as those of the above-described aspects and modified examples can be obtained.

[0098] (Modified Example 3) Since the KNN film 3 is formed at a low temperature of 400°C or higher and less than 500°C as described above, it is also possible to use another substrate that requires a small thermal history as the substrate 1.

[0099] For example, it is also possible to use a substrate on which a CMUT (Capacitive Micro-machined Ultrasound Transducer) structure is formed as the substrate 1.

[0100] Also, for example, it is also possible to use either a resin substrate or a glass substrate that is vulnerable to heat as the substrate 1.

[0101] As the resin substrate, for example, a substrate made of polyimide, polytetrafluoroethylene (PTFE), polyethylene naphthalate, polypropylene, polystyrene, polycarbonate, polysulfone, polyarylate, polyamide, polyethylene terephthalate (PET), or acrylic resin can be used. Further, as the resin substrate, for example, a glass epoxy resin substrate, a paper phenol substrate, a paper epoxy substrate, a glass composite substrate, or a fluororesin substrate can also be used. Further, as the resin substrate, a composite resin substrate containing, for example, silicon oxide particles, metal nanoparticles, inorganic oxide nanoparticles, inorganic nitride nanoparticles, metal-based or inorganic-based nanofibers or microfibers in the above resin substrate can also be used. The thickness of the resin substrate can be, for example, 10 μm or more and 1000 μm or less.

[0102] Even when the above-described substrate is used as the substrate 1, in the process of manufacturing the laminate 10, by forming the KNN film 3 with all of the film formation temperature, oxygen partial pressure, and atmospheric pressure within the range of the above-described predetermined conditions, it is required to reduce the thermal history. On the substrate 1 that is vulnerable to heat or the substrate 1 that is weak to heat, while suppressing the diffusion of the alkali metal into the substrate 1, the KNN film 3 with a high (001) orientation ratio can be formed. As a result, also in this modification example, the laminate 10 having at least both of the feature 1 and the feature 2 can be obtained.

[0103] Further, when a substrate on which a CMUT structure is formed, a resin substrate that is weak to heat, or a glass substrate is used as the substrate 1, it is preferable that the film formation temperatures of the lower electrode film 2 and the lower adhesion layer 6 are each less than 500°C. Specifically, the film formation temperature of the lower electrode film 2 is, for example, 200°C or more and less than 500°C, preferably 300°C or more and 450°C or less. When a ZnO layer is formed as the lower adhesion layer 6, the film formation temperature is, for example, 200°C or more and less than 500°C, preferably 300°C or more and 450°C or less, more preferably 400°C or more and 450°C or less. When a Ti layer or the like is formed as the lower adhesion layer 6, the film formation temperature is, for example, 100°C or more and less than 500°C, preferably 200°C or more and 400°C or less. Thereby, the thermal history with respect to the substrate 1 can be surely reduced.

[0104] Furthermore, it is also possible to use a metal substrate as the substrate 1. As the metal substrate, for example, a substrate containing platinum (Pt), gold (Au), iron (Fe), titanium (Ti), copper (Cu), molybdenum (Mo), nickel (Ni), aluminum (Al), tungsten (W), palladium (Pd) as the main component can be used. Also, as the metal substrate, for example, a substrate made of stainless steel (Stainless Steel: SUS), permalloy, or inconel can be used. The thickness of the metal substrate can be, for example, 10 μm or more and 1000 μm or less. Also in this case, in the process of manufacturing the laminate 10, by forming the KNN film 3 with all of the film formation temperature, oxygen partial pressure, and atmospheric pressure within the range of the above-described predetermined conditions, a laminate 10 having at least both of Feature 1 and Feature 2 can be obtained.

[0105] (Modification Example 4) In the above-described embodiments and modification examples, the example of providing the lower adhesion layer 6 and the lower electrode film 2 has been described, but the present invention is not limited thereto. The lower adhesion layer 6 and the lower electrode film 2 may not be provided. That is, the KNN film 3 may be directly formed on the substrate 1.

[0106] Also in this modification example, in the process of manufacturing the laminate 10, by forming the KNN film 3 with all of the film formation temperature, oxygen partial pressure, and atmospheric pressure within the range of the above-described predetermined conditions, it is possible to increase the (001) orientation ratio of the KNN film while suppressing the diffusion of the alkali metal into the substrate 1. As a result, also in this aspect, the same effects as those of the above-described embodiments and modification examples can be obtained. That is, a laminate 10 having at least both of Feature 1 and Feature 2 can be obtained.

[0107] Also, in this modification example, since the KNN film 3 is formed at a low temperature of 400°C or more and less than 500°C, any of the substrates described in Modification Examples 1 to 3 above can be used as the substrate 1.

[0108] <Other Aspects> The embodiments and modifications of the present disclosure have been specifically described above. However, the present disclosure is not limited to the above-described embodiments and modifications, and various changes can be made without departing from the gist thereof.

[0109] In addition, in the above-described embodiment, the case where the lower adhesion layer 6 is provided between the substrate 1 and the lower electrode film 2 and the upper adhesion layer 7 is provided between the KNN film 3 and the upper electrode film 4 has been described, but the present disclosure is not limited thereto. If the necessary adhesion can be ensured, the lower adhesion layer 6 and the upper adhesion layer 7 may not be provided.

Example

[0110] Hereinafter, experimental results verifying the effects of the above-described embodiment will be described.

[0111] (Sample 1) As a substrate, a Si substrate having a surface with a (100) plane orientation, a thickness of 610 μm, a diameter of 6 inches, and a thermally oxidized film (SiO2 film) with a thickness of 500 nm formed on the surface was prepared. Then, on this substrate (on the thermally oxidized film), a ZnO layer (thickness: 25 nm) as a lower adhesion layer, a Pt film (thickness: 200 - 300 nm) as a lower electrode film, and a KNN film (thickness: 2 μm) as a piezoelectric film were sequentially formed to fabricate a piezoelectric laminate (Sample 1). In Sample 1, the lower adhesion layer, the lower electrode film, and the KNN film were all formed by the RF magnetron sputtering method. Note that

[0112] The conditions for forming the ZnO layer as the lower adhesion layer were as follows. Target: ZnO sintered body Substrate temperature: 500 °C Discharge power density: 4 W / cm 2 Atmosphere: Ar / O2 mixed gas atmosphere Atmospheric pressure (chamber pressure): 0.3 Pa Ar gas partial pressure / O2 gas partial pressure: 10 / 1 Film formation time: 3 minutes (thickness 25 nm)

[0113] The conditions for forming the Pt film as the lower electrode film were as follows. Target: Pt plate Substrate temperature: 500 °C Discharge power density: 2 W / cm 2 Atmosphere: Ar gas atmosphere Atmospheric pressure (chamber pressure): 0.3 Pa Film formation time: 20 minutes (thickness 200 nm)

[0114] The conditions for forming the KNN film were as follows. Target: KNN sintered body Discharge power density: 3 W / cm 2 Atmosphere: Ar / O2 mixed gas atmosphere Film formation temperature: 490 °C Oxygen partial pressure: 0.003 Pa Atmospheric pressure (chamber pressure): 0.05 Pa Film formation time: 120 minutes (thickness 2000 nm (2 μm))

[0115] (Samples 2 - 13) For Samples 2 - 13, the temperature, oxygen partial pressure, and atmospheric pressure during KNN film formation were as described in Table 1. Other conditions were the same as those for Sample 1 during film formation.

[0116]

Table 1

[0117] [Evaluation] For each of Samples 1 - 13, the K concentration and Na concentration in the surface layer region of the substrate, the (001) orientation ratio of the KNN film, the piezoelectric constant e 31 , and the adhesion between the substrate and the lower adhesion layer (lower electrode film) were evaluated.

[0118] (Measurement of K concentration and Na concentration) The measurement of the K concentration and the Na concentration in the surface layer region of the substrate was performed by SIMS analysis. For the SIMS analysis, in order to improve the analysis accuracy, each sample in a state where the KNN film was removed by etching was used. The measurement results of the K concentration and the Na concentration in the surface layer region of the substrate are shown in Table 2 below. In Table 2, 1E14 cm of the K concentration -3 The following means that the K concentration in the surface layer region of the substrate is below the detection limit of the lower limit value by SIMS analysis, and 3E14 cm of the Na concentration -3 The following means that the Na concentration in the surface layer region of the substrate is below the detection limit of the lower limit value by SIMS analysis.

[0119] (Evaluation of the (001) orientation ratio of the KNN film) The (001) orientation ratio of the KNN film was evaluated by calculating according to the above formula (1) based on the peak intensity of the X-ray diffraction pattern (2θ / θ) obtained by performing XRD measurement on the KNN film. The calculation results of the (001) orientation ratio are shown in Table 2 below. In Table 2, the "orientation ratio" means the (001) orientation ratio of the KNN film.

[0120] (Evaluation of the piezoelectric constant) The piezoelectric constant e of the KNN film 31 was measured (evaluated) as follows. First, rectangular test pieces with a width of 2.5 mm and a length of 20 mm were prepared from each sample. One end in the longitudinal direction of each prepared test piece was fixed as a fixed end, and the other end was used as a free end to prepare a simple piezoelectric element having a cantilever (single-ended beam) structure, and a voltage application means was connected to this piezoelectric element. Then, while applying a voltage to the KNN film of each test piece (piezoelectric element), the displacement amount of the free end of the test piece was measured with a laser. Using the measured displacement amount, the piezoelectric constant e 31 was calculated. In the following (Equation 2), s 11,s is the Young's modulus of the substrate (Si substrate) of each sample, h s is the thickness of the substrate of each sample, L is the beam length (14.5 mm), δ is the output displacement based on the measured displacement amount, and V is the voltage applied to the piezoelectric film. The piezoelectric constant e 31The frequency of the alternating electric field (alternating voltage) during measurement is 350 Hz, and the maximum value of the voltage applied to the KNN film is 20 V. The piezoelectric constant e 31 has the unit C / m 2 . The measurement results of the piezoelectric constant e 31 are shown in Table 2 below.

[0121] (Equation 2) TIFF2025103513000003.tif19170

[0122] (Evaluation of Adhesion) The adhesion between the substrate and the lower adhesion layer (lower electrode film) was evaluated by the following alternating voltage application test. First, two rectangular test pieces with a width of 2.5 mm and a length of 20 mm were prepared from each sample. One end in the longitudinal direction of each prepared test piece was fixed as a fixed end, and the other end was used as a free end to fabricate a simple piezoelectric element having a cantilever (single-ended beam) structure, and a voltage application means was connected to this piezoelectric element. Then, an alternating voltage was continuously applied to the KNN film of the test piece (piezoelectric element) for 100 hours to one of the two pieces and for 200 hours to the other. The frequency of the alternating voltage was 350 Hz, and the maximum value of the voltage applied to the KNN film was 30 V. After the voltage application, the presence or absence of peeling of the lower adhesion layer (lower electrode film) was confirmed with a scanning electron microscope. The evaluation results are shown in Table 2 below. In Table 2, "○" means that peeling of the lower electrode film was not confirmed (no peeling) in the piezoelectric element to which the alternating voltage was applied for 200 hours, "△" means that peeling of the lower electrode film was not confirmed in the piezoelectric element to which the alternating voltage was applied for 100 hours, but peeling of the lower electrode film was confirmed in the piezoelectric element to which the alternating voltage was applied for 200 hours, and "×" means that peeling of the lower electrode film was confirmed in the piezoelectric element to which the alternating voltage was applied for 100 hours.

[0123]

Table 2

[0124] From Table 2, in Samples 1, 2, 3, 6, 8, 10, and 12 where the KNN film was formed under the conditions that the film formation temperature was 400°C or higher and less than 500°C, the oxygen partial pressure was 0.0025 Pa or higher and less than 0.01 Pa, and the atmospheric pressure was 0.03 Pa or higher and less than 0.1 Pa, the K concentration and the Na concentration in the surface layer region of the substrate were 5E15 cm -3 or less, and it was confirmed that the (001) orientation ratio of the KNN film was 96% or higher. From this, it can be seen that in Samples 1, 2, 3, 6, 8, 10, and 12, the diffusion of alkali metals into the substrate is suppressed, and also that even when the KNN film is formed at a low temperature, the (001) orientation ratio of the KNN film is sufficiently increased. Furthermore, in Samples 1, 2, 3, 6, 8, 10, and 12, the piezoelectric constant e 31 is 7 C / m 2 or higher can also be confirmed. Thus, it can be confirmed that in the samples where the KNN film was formed with all of the film formation temperature, oxygen partial pressure, and atmospheric pressure within the range of the above-described predetermined conditions, a laminate having both of the above-described Feature 1 and Feature 2, and furthermore, a laminate having all of the above-described Features 1 to 3 can be obtained.

[0125] Also, among the samples (laminates) having both of the above-described Feature 1 and Feature 2, in Samples 2, 3, 6, 8, 10, and 12 where the film formation temperature was 400°C or higher and 450°C or lower, the K concentration and the Na concentration in the surface layer region of the substrate were 3E14 cm -3 or less, and furthermore, it was confirmed that the K concentration in the surface layer region of the substrate was 1E14 cm -3 or less. That is, when the KNN film is formed under the condition of 400°C or higher and 450°C or lower, while avoiding a decrease in the (001) orientation ratio of the KNN film, the diffusion of alkali metals into the substrate is more reliably suppressed, and it can be seen that the values can be reduced to below the detection limit of the lower limit values of the K concentration and the Na concentration by SIMS analysis. Also, in these samples, even when an AC voltage of frequency: 350 Hz, maximum voltage value: 30 V was applied for 200 hours, peeling of the lower electrode film was not confirmed. That is, it was found that Samples 2, 3, 6, 8, 10, and 12 have higher adhesion than Sample 1.

[0126] Also, from Table 2, it can be confirmed that in Sample 4, the K concentration and Na concentration in the surface layer region of the substrate are 5E15 cm -3 respectively. From this, it can be seen that when the film formation temperature of the KNN film is 500 °C (500 °C or higher), even if the oxygen partial pressure and atmospheric pressure during KNN film formation are within the range of predetermined conditions, the diffusion of alkali metals into the substrate cannot be suppressed. That is, it can be seen that a laminate having both of the above-mentioned Features 1 and 2 cannot be obtained.

[0127] Also, from Table 2, it can be confirmed that in Sample 5, the (001) orientation ratio of the KNN film is less than 96%. From this, it can be seen that when the film formation temperature of the KNN film is 390 °C (less than 400 °C), even if the oxygen partial pressure and atmospheric pressure during KNN film formation are within the range of predetermined conditions, the (001) orientation ratio of the KNN film cannot be sufficiently increased. That is, it can be seen that a laminate having both of the above-mentioned Features 1 and 2 cannot be obtained.

[0128] Also, from Table 2, in Samples 7 and 9, the (001) orientation ratio of the KNN film is less than 96%, and the piezoelectric constant e 31 is less than 7.0 C / m 2 It can be confirmed. From this, it can be seen that when the oxygen partial pressure during KNN film formation is 0.01 Pa (0.01 Pa or higher) or when the oxygen partial pressure during KNN film formation is 0.002 Pa (less than 0.0025 Pa), the (001) orientation ratio of the KNN film cannot be sufficiently increased. For this reason, it can be seen that when the film formation temperature of the KNN film is less than 500 °C, the (001) orientation ratio of the KNN film becomes less than 96%. That is, it can be seen that a laminate having both of the above-mentioned Features 1 and 2 cannot be obtained. Also, as a result of the (001) orientation ratio of the KNN film being less than 96%, it can also be seen that the piezoelectric constant e 31 may also be less than 7.0 C / m 2 .

[0129] Also, from Table 2, in Samples 11 and 13, the (001) orientation ratio of the KNN film is less than 96%, and the piezoelectric constant e 31 is less than 7.0 C / m 2It can be confirmed that it is less than this. From this, it can be seen that when the atmospheric pressure during the formation of the KNN film is 0.1 Pa (0.1 Pa or more), or when the atmospheric pressure during the formation of the KNN film is 0.025 Pa (less than 0.03 Pa), the (001) orientation ratio of the KNN film cannot be sufficiently increased. Therefore, it can be seen that when the film formation temperature of the KNN film is less than 500 °C, the (001) orientation ratio of the KNN film becomes less than 96%. That is, it can be seen that a laminate having both of the above-described features 1 and 2 cannot be obtained. Further, as a result of the (001) orientation ratio of the KNN film being less than 96%, it can also be seen that the piezoelectric constant e 31 may also be less than 7.0 C / m 2 is obtained.

[0130] <Preferred Embodiment of the Present Disclosure> Hereinafter, preferred embodiments of the present disclosure will be appended.

[0131] (Appendix 1) According to one embodiment of the present disclosure, a substrate, a piezoelectric film made of an alkali niobate oxide containing potassium, sodium, niobium, and oxygen, formed on the substrate, and when performing SIMS analysis on a region ranging from the surface of the substrate on which the piezoelectric film is formed to a depth of 1 μm toward the surface opposite to the surface of the substrate on which the piezoelectric film is formed, among the substrates, the concentration of potassium is 5E15 cm -3 or less, and the concentration of sodium is 5E15 cm -3 or less, and the orientation ratio of the crystal constituting the piezoelectric film in the (001) plane orientation is 96% or more, a laminated substrate is provided.

[0132] (Appendix 2) The laminated substrate according to Appendix 1, wherein the piezoelectric constant e of the piezoelectric film 31 is 7 C / m 2 or more.

[0133] (Appendix 3) The laminated substrate according to Appendix 1 or 2, The substrate is any one of a semiconductor substrate, a resin substrate, a glass substrate, and a metal substrate.

[0134] (Appendix 4) A laminated substrate according to any one of Appendices 1 to 3, wherein the substrate is a silicon substrate, and a semiconductor element is formed on the substrate.

[0135] (Appendix 5) A laminated substrate according to Appendix 4, wherein the substrate has a protective film for protecting the semiconductor element.

[0136] (Appendix 6) A laminated substrate according to Appendix 4 or 5, wherein the semiconductor element has either a region in which a p-type or n-type dopant (impurity) is diffused or a region in which the dopant is ion-implanted.

[0137] (Appendix 7) A laminated substrate according to any one of Appendices 1 to 6, comprising a lower electrode film formed between the substrate and the piezoelectric film.

[0138] (Appendix 8) According to another aspect of the present disclosure, a step of preparing a substrate, and a step of forming a piezoelectric film composed of an alkali niobate oxide containing potassium, sodium, niobium, and oxygen on the substrate by a sputtering method, wherein in the step of forming the piezoelectric film, the film formation temperature is 400°C or higher and lower than 500°C, the oxygen partial pressure is 0.0025 Pa or higher and lower than 0.01 Pa, and the atmospheric pressure is 0.03 Pa or higher and lower than 0.1 Pa. A method for manufacturing a laminated substrate is provided.

[0139] (Appendix 9) According to still another aspect of the present disclosure, a substrate, The lower electrode film formed on the substrate, A piezoelectric film formed on the substrate and composed of an alkali niobate oxide containing potassium, sodium, niobium, and oxygen, When performing SIMS analysis on a region ranging from the surface of the substrate on which the piezoelectric film is formed to a depth of 1 μm toward the surface of the substrate opposite to the surface on which the piezoelectric film is formed, the concentration of potassium is 5E15 cm -3 or less, and the concentration of sodium is 5E15 cm -3 or less, The orientation rate of the crystal constituting the piezoelectric film in the (001) plane direction is 96% or more, A piezoelectric element or a piezoelectric device module is provided.

[0140] (Appendix 10) The piezoelectric element or piezoelectric device module according to Appendix 9, Comprising an upper electrode film formed on the piezoelectric film.

[0141] (Appendix 11) The piezoelectric element or piezoelectric device module according to Appendix 9 or 10, Comprising a lower electrode film formed between the substrate and the piezoelectric film.

[0142] (Appendix 12) The laminated substrate according to any one of Appendices 1 to 7, or the piezoelectric element or piezoelectric device module according to any one of Appendices 9 to 11, There are no traces resulting from bonding at the interface between the substrate and the piezoelectric film, the interface between the substrate and the lower electrode film (including the lower adhesion layer when including the lower adhesion layer), or the interface between the lower electrode film and the piezoelectric film. Note that the traces resulting from bonding mean the distribution of inclusions used for bonding and impurities not derived from the film formation process, etc.

Explanation of Symbols

[0143] 1 Substrate 2 Lower electrode film 3 Piezoelectric film 4 Upper electrode film 6 Lower adhesion layer 7 Upper adhesion layer 8 Insulating film 9a, 9b Metal wiring 10 Laminate 20 Piezoelectric element 30 Piezoelectric device module

Claims

1. A substrate, and a piezoelectric film formed on the substrate and composed of an alkali niobate oxide containing potassium, sodium, niobium, and oxygen. When performing SIMS analysis on the region ranging from the surface of the substrate on which the piezoelectric film is formed to a depth of 1 μm toward the surface opposite to the surface of the substrate on which the piezoelectric film is formed among the substrates, the potassium concentration is 5E15 cm －３ or less, and the sodium concentration is 5E15 cm －３ or less, and The orientation rate of the crystal constituting the piezoelectric film in the (001) plane direction is 96% or more. A laminated substrate.

2. The piezoelectric constant e of the piezoelectric film ３１ is 7 C / m ２ The laminated substrate according to claim 1, wherein the piezoelectric constant e is 7 C / m or more.

3. The laminated substrate according to claim 1 or 2, wherein the substrate is any one of a semiconductor substrate, a resin substrate, a glass substrate, and a metal substrate.

4. The substrate is a silicon substrate, and a semiconductor element is formed on the substrate. The laminated substrate according to claim 1 or 2.

5. The laminated substrate according to claim 4, wherein a protective film for protecting the semiconductor element is formed on the substrate.

6. A step of preparing a substrate, and a step of forming a piezoelectric film composed of an alkali niobate oxide containing potassium, sodium, niobium, and oxygen on the substrate by a sputtering method. In the step of forming the piezoelectric film, the film formation temperature is 400 °C or higher and lower than 500 °C, the oxygen partial pressure is 0.0025 Pa or higher and lower than 0.01 Pa, and the atmospheric pressure is 0.03 Pa or higher and lower than 0.1 Pa. A method for manufacturing a laminated substrate.

7. A substrate, and a piezoelectric film formed on the substrate and composed of an alkali niobate oxide containing potassium, sodium, niobium, and oxygen. When SIMS analysis was performed on the region extending from the surface of the substrate on which the piezoelectric film was formed to a depth of 1 μm toward the surface of the substrate opposite to the surface on which the piezoelectric film was formed among the substrates, the potassium concentration was 5E15 cm －３ or less, and the sodium concentration was 5E15 cm －３ or less, and The orientation rate of the crystal constituting the piezoelectric film in the (001) plane direction is 96% or more. A piezoelectric element.

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