Method for manufacturing piezoelectric film substrate, and piezoelectric film substrate

Abstract

This method for manufacturing a piezoelectric film substrate includes: a step for forming a lower electrode layer on a substrate; a step for forming a lower adjustment layer containing a lower adjustment element, which is a predetermined metal element, on the lower electrode layer; a step for forming a piezoelectric layer containing lead zirconate titanate having a perovskite structure on the lower adjustment layer; a step for forming an upper adjustment layer containing an upper adjustment element, which is a predetermined metal element, on the piezoelectric layer; a step for forming an upper electrode layer on the upper adjustment layer; and a step for holding, after the step for forming the upper electrode layer, the substrate for a predetermined period in a state in which the substrate is heated.

Description

Piezoelectric film substrate manufacturing method and piezoelectric film substrate

[0001] The present invention relates to a method for manufacturing a piezoelectric film substrate and a piezoelectric film substrate, and more particularly to a method for manufacturing a piezoelectric film substrate on which a piezoelectric layer containing lead zirconate titanate having a perovskite structure is formed, and a piezoelectric film substrate.

[0002] A method for forming a lead zirconate titanate film having a perovskite structure has been known, and is disclosed in, for example, Japanese Patent No. 6030418.

[0003] The above-mentioned Japanese Patent No. 6,030,418 discloses a method for forming a lead zirconate titanate film on a silicon substrate on which a platinum film has been formed. In this method, a lead zirconate titanate film is formed on a platinum film formed as a lower electrode on the silicon substrate. After the lead zirconate titanate film formation step, the silicon substrate is maintained at a temperature higher than that during the film formation step by a heating means in order to improve the crystallinity of the formed lead zirconate titanate film and thereby improve its withstand voltage performance. In the method for forming a lead zirconate titanate film disclosed in the above-mentioned Japanese Patent No. 6,030,418, the space in which the silicon substrate is held after the film formation step is filled with lead atoms and lead-containing molecules such as lead oxide, creating a lead atmosphere (Pb atmosphere).

[0004] Patent No. 6030418

[0005] However, in the method for forming a lead zirconate titanate film described in the above-mentioned Japanese Patent No. 6,030,418, in order to improve the withstand voltage performance of the lead zirconate titanate film (piezoelectric layer), it is necessary to prepare a space with a lead atmosphere (Pb atmosphere) in which the substrate is placed. Furthermore, if heating is performed in a state other than a lead atmosphere, it is thought that the withstand voltage performance of the piezoelectric layer will be reduced due to the lead atoms contained in the lead zirconate titanate being released from the surface of the piezoelectric layer. For these reasons, it is desirable to easily improve the withstand voltage performance of piezoelectric layers containing lead zirconate titanate.

[0006] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide a method for manufacturing a piezoelectric film substrate and a piezoelectric film substrate that can easily improve the voltage resistance performance of a piezoelectric layer containing lead zirconate titanate.

[0007] In order to achieve the above object, a manufacturing method of a piezoelectric film substrate according to a first aspect of the present invention comprises the steps of forming a lower electrode layer on a substrate, forming a lower adjustment layer containing a lower adjustment element which is a predetermined metal element on the lower electrode layer, depositing a piezoelectric layer containing lead zirconate titanate having a perovskite structure on the lower adjustment layer, forming an upper adjustment layer containing an upper adjustment element which is a predetermined metal element on the piezoelectric layer, forming an upper electrode layer on the upper adjustment layer, and, after the step of forming the upper electrode layer, holding the substrate in a heated state for a predetermined period of time.

[0008] A method for manufacturing a piezoelectric film substrate according to a first aspect of the present invention includes, as described above, a step of holding the substrate in a heated state for a predetermined period of time after the step of forming the upper electrode layer. This allows the upper adjustment layer below the upper electrode layer to function as a barrier, thereby preventing lead from being released from the surface of the piezoelectric layer even when the substrate is heated. Therefore, even when the substrate is heated in a space other than a lead atmosphere, a decrease in the voltage resistance performance of the piezoelectric layer due to lead release can be prevented. A method for manufacturing a piezoelectric film substrate according to a first aspect of the present invention also includes, as described above, a step of forming a piezoelectric layer containing lead zirconate titanate having a perovskite structure on a lower adjustment layer containing a lower adjustment element that is a predetermined metal element, and a step of forming an upper adjustment layer containing an upper adjustment element that is a predetermined metal element on the piezoelectric layer. This allows the titanium, zirconium, and lead elements contained in the piezoelectric layer to be replaced by the metal elements contained in each of the upper adjustment layer and the lower adjustment layer by elemental diffusion by heating the substrate with the piezoelectric layer sandwiched between the upper adjustment layer and the lower adjustment layer. Therefore, at both the upper and lower interfaces of the piezoelectric layer, titanium, zirconium, and lead contained in the piezoelectric layer are each replaced with a metal element having a different valence, thereby reducing lattice defects such as oxygen vacancies and lead vacancies contained in the piezoelectric layer, thereby improving the voltage resistance of the piezoelectric layer.As a result, the voltage resistance of the piezoelectric layer can be improved while suppressing the release of lead elements without heating the substrate in a space with a lead atmosphere, thereby preventing lead from adhering to a heating device that heats the substrate and easily improving the voltage resistance of the piezoelectric layer containing lead zirconate titanate.

[0009] In the method for manufacturing a piezoelectric film substrate according to the first aspect, the step of forming a piezoelectric layer preferably includes a step of forming the piezoelectric layer on a lower adjustment layer formed on a substrate placed in a deposition chamber, and the step of holding the substrate for a predetermined period includes a step of holding the substrate for a predetermined period in a heated state in a heat treatment furnace different from the deposition chamber. Here, if the substrate is held in a heated state in the deposition chamber in order to improve crystallinity, particles may be generated due to the material of the piezoelectric layer adhering to the inner wall of the deposition chamber peeling off. Furthermore, if the substrate is heated in the deposition chamber, the thermal load on the device for forming the piezoelectric layer, including the deposition chamber, increases. In response to these issues, the present invention holds the substrate in a heated state in a heat treatment furnace different from the deposition chamber for a predetermined period, thereby suppressing the generation of particles that may cause a deterioration in the performance of the resulting piezoelectric film substrate and suppressing an increase in the load on the device, including the deposition chamber, in which the piezoelectric layer is formed.

[0010] In this case, the step of holding the substrates for a predetermined period preferably includes a step of holding the plurality of substrates collectively in a heat treatment furnace in a heated state for a predetermined period, which can shorten the time required to manufacture the plurality of piezoelectric film substrates compared to holding the plurality of substrates individually in a heated state.

[0011] In the method for manufacturing a piezoelectric film substrate according to the first aspect, the step of forming the lower adjustment layer preferably includes a step of forming a lower adjustment layer containing strontium and ruthenium as lower adjustment elements, or containing lanthanum and nickel as lower adjustment elements, and adjusting the crystal orientation of the piezoelectric layer, and the step of forming the upper adjustment layer includes a step of forming an upper adjustment layer containing strontium and ruthenium as upper adjustment elements, or containing lanthanum and nickel as upper adjustment elements.With this configuration, by forming the piezoelectric layer on the lower adjustment layer, the crystal orientation of the piezoelectric layer is adjusted, thereby further improving the crystallinity of the piezoelectric layer.In addition, strontium, ruthenium, lanthanum, and nickel are all likely to become cations with lower valences than titanium and zirconium contained in the lead zirconate titanate of the piezoelectric layer. Therefore, when titanium and zirconium in the piezoelectric layer are replaced by strontium, ruthenium, lanthanum, or nickel through elemental diffusion, the charge of the entire piezoelectric layer tends to decrease, and the lead vacancies contained in the piezoelectric layer decrease in order to increase the charge and maintain electrical neutrality. Furthermore, when lead in the piezoelectric layer is replaced by a metal element with a higher valence than lead, such as lanthanum, through elemental diffusion, the charge of the entire piezoelectric layer decreases in order to maintain electrical neutrality, and the oxygen vacancies contained in the piezoelectric layer decrease in order to maintain electrical neutrality. Therefore, since the piezoelectric layer is sandwiched between a lower adjustment layer and an upper adjustment layer containing strontium and ruthenium or lanthanum and nickel, elemental diffusion can occur at both the upper and lower interfaces of the piezoelectric layer to reduce the vacancies in the piezoelectric layer and further improve the withstand voltage performance. As a result, the withstand voltage performance of the piezoelectric layer can be further improved.

[0012] In this case, preferably, the step of forming the upper adjustment layer includes a step of forming an upper adjustment layer containing an upper adjustment element that is a metal element common to the lower adjustment element contained in the lower adjustment layer and having the same composition as the lower adjustment layer. This configuration allows both the upper adjustment layer and the lower adjustment layer to be formed from a common material. Therefore, compared to when the upper adjustment layer and the lower adjustment layer contain different metal elements, the number of types of materials used to manufacture the piezoelectric film substrate can be reduced, thereby reducing the effort required to manufacture the piezoelectric film substrate.

[0013] In the method for manufacturing a piezoelectric film substrate according to the first aspect, the step of holding the substrate for a predetermined period preferably includes holding the substrate in a heated state for a predetermined period of 5 minutes or more but less than 60 minutes. Here, if the period for holding the substrate in a heated state is too short, elemental diffusion from the lower adjustment layer and the upper adjustment layer becomes difficult, resulting in insufficient improvement in the voltage resistance performance of the piezoelectric layer. Furthermore, if the period for holding the substrate in a heated state is too long, the characteristics of the piezoelectric layer deteriorate due to excessive elemental substitution caused by elemental diffusion from the lower adjustment layer and the upper adjustment layer. In contrast, in the present invention, by holding the substrate in a heated state for a predetermined period of 5 minutes or more but less than 60 minutes, the substrate can be held in a heated state for an appropriate length of time. Therefore, the voltage resistance performance of the piezoelectric layer can be further improved compared to when the holding period is too short or too long.

[0014] In the method for manufacturing a piezoelectric film substrate according to the first aspect, the step of forming the piezoelectric layer preferably includes a step of forming the piezoelectric layer on the lower adjustment layer by sputtering while the substrate is heated to a predetermined film-forming temperature by a heating device, and the step of holding the substrate for a predetermined period includes a step of holding the substrate for a predetermined period while the substrate is heated to a temperature higher than the predetermined film-forming temperature during sputtering to form the piezoelectric layer. Here, since substitution by elemental diffusion progresses as the temperature increases, holding the substrate in a heated state at a temperature higher than the predetermined film-forming temperature during sputtering to form the piezoelectric layer allows the substrate to be held in a heated state at a sufficiently high temperature. Therefore, it is possible to prevent insufficient elemental diffusion and insufficient improvement in voltage resistance performance due to an excessively low heating temperature.

[0015] In order to achieve the above object, a piezoelectric film substrate according to a second aspect of the present invention comprises: a lower electrode layer formed on a substrate; a lower adjustment layer formed on the lower electrode layer and containing a lower adjustment element which is a predetermined metal element; a piezoelectric layer containing lead zirconate titanate having a perovskite structure formed on the lower adjustment layer; an upper adjustment layer formed on the piezoelectric layer and containing an upper adjustment element which is a predetermined metal element; and an upper electrode layer formed on the upper adjustment layer, wherein the piezoelectric layer includes a lower diffusion layer formed along the interface with the lower adjustment layer and an upper diffusion layer formed along the interface with the upper adjustment layer, the lower diffusion layer having a thickness of 10% or less of the film thickness of the entire piezoelectric layer, and At least one of titanium, zirconium, and lead contained in the piezoelectric layer is substituted by the lower adjustment element contained in the lower adjustment layer by element diffusion, and there is a region in which the detection intensity ratio of the lower adjustment element contained in the lower diffusion layer is 10% or more higher than that of the portion of the piezoelectric layer other than the upper diffusion layer and the lower diffusion layer, and the upper diffusion layer has a thickness of 10% or less of the film thickness of the entire piezoelectric layer, and at least one of titanium, zirconium, and lead contained in the piezoelectric layer is substituted by the upper adjustment element contained in the upper adjustment layer by element diffusion, and there is a region in which the detection intensity ratio of the upper adjustment element contained in the upper diffusion layer is 10% or more higher than that of the portion of the piezoelectric layer other than the upper diffusion layer and the lower diffusion layer.

[0016] A piezoelectric film substrate according to a second aspect of the present invention includes an upper adjustment layer formed on a piezoelectric layer and containing an upper adjustment element, which is a predetermined metal element. The upper adjustment layer thus acts as a barrier, preventing lead from being released from the surface of the piezoelectric layer even when the substrate is heated. Therefore, even when the substrate is heated in a space other than a lead atmosphere, deterioration in the voltage resistance performance of the piezoelectric layer due to lead release can be prevented. The piezoelectric film substrate according to the second aspect of the present invention also includes a piezoelectric layer containing lead zirconate titanate having a perovskite structure formed on the lower adjustment layer, and an upper adjustment layer formed on the piezoelectric layer and containing the upper adjustment element, which is a predetermined metal element. By heating the substrate with the piezoelectric layer sandwiched between the upper adjustment layer and the lower adjustment layer, the titanium, zirconium, and lead elements contained in the piezoelectric layer can be replaced by the metal elements contained in each of the upper adjustment layer and the lower adjustment layer through elemental diffusion. Therefore, at both the upper and lower interfaces of the piezoelectric layer, titanium, zirconium, and lead contained in the piezoelectric layer are each replaced with a metal element having a different valence, thereby reducing lattice defects such as oxygen vacancies and lead vacancies contained in the piezoelectric layer, thereby improving the voltage resistance of the piezoelectric layer. As a result, the voltage resistance of the piezoelectric layer can be improved while suppressing the release of lead elements without heating the substrate in a lead atmosphere, thereby preventing lead from adhering to a heating device that heats the substrate and providing a piezoelectric film substrate that can easily improve the voltage resistance of the piezoelectric layer containing lead zirconate titanate.

[0017] According to the present invention, as described above, the withstand voltage performance of the piezoelectric layer containing lead zirconate titanate can be easily improved.

[0018] Fig. 1 is a cross-sectional view showing a piezoelectric film substrate according to one embodiment; Fig. 2 is a diagram schematically showing the perovskite structure of lead zirconate titanate in a piezoelectric layer; Fig. 3 is a diagram for explaining an upper diffusion layer and a lower diffusion layer included in a piezoelectric layer; Fig. 4 is a diagram schematically showing the configuration of a sputtering apparatus; Fig. 5 is a diagram schematically showing the configuration of a heat treatment furnace; Fig. 6 is a flowchart for explaining a method for manufacturing a piezoelectric film substrate according to one embodiment;

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] (Configuration of Piezoelectric Film Substrate) The configuration of a piezoelectric film substrate 100 according to one embodiment of the present invention will be described with reference to FIGS.

[0021] The piezoelectric film substrate 100 is a piezoelectric film substrate that is divided into a plurality of pieces, each of which becomes a device. Each of the plurality of pieces becomes a device. The device is, for example, a MEMS (Micro Electro Mechanical Systems) device. The MEMS device is also used, for example, as a sensor or an actuator.

[0022] 1 , the piezoelectric film substrate 100 includes a substrate 1, an insulating layer 2, a lower electrode layer 3, a lower adjustment layer 4, a piezoelectric layer 5, an upper adjustment layer 6, and an upper electrode layer 7. In the piezoelectric film substrate 100, the insulating layer 2, the lower electrode layer 3, the lower adjustment layer 4, the piezoelectric layer 5, the upper adjustment layer 6, and the upper electrode layer 7 are stacked in this order on the substrate 1. In the piezoelectric film substrate 100, the insulating layer 2, the lower electrode layer 3, and the lower adjustment layer 4 form a multilayer lower electrode below the piezoelectric layer 5. In the piezoelectric film substrate 100, the upper adjustment layer 6 and the upper electrode layer 7 form a multilayer upper electrode above the piezoelectric layer 5.

[0023] The substrate 1 is a silicon substrate. The insulating layer 2 is a thin film made of an insulator formed on the substrate 1. The insulating layer 2 is made of, for example, silicon dioxide (SiO2). The insulating layer 2 may also be made of a material such as zirconium oxide (ZrO2) or yttria-stabilized zirconia (YSZ). For example, the insulating layer 2 includes a silicon oxide layer formed on the surface of the substrate 1 by thermally oxidizing the substrate 1, which is a silicon substrate. The substrate 1 has a thickness of, for example, about 300 μm or more and about 725 μm or less. The insulating layer 2 has a thickness of, for example, about 100 nm or more and about 500 nm or less.

[0024] The lower electrode layer 3 is formed on the insulating layer 2 on the substrate 1. Specifically, the lower electrode layer 3 is formed as a single crystal by epitaxial growth. The lower electrode layer 3 is made of a material such as platinum (Pt) or iridium (Ir). The lower electrode layer 3 has a thickness of, for example, about 50 nm or more and about 200 nm or less.

[0025] The lower adjustment layer 4 is formed on the substrate 1 and on the lower electrode layer 3. The lower adjustment layer 4 contains a lower adjustment element, which is a predetermined metal element. The lower adjustment layer 4 contains a metal oxide. The lower adjustment layer 4 contains strontium (Sr) and ruthenium (Ru) as the lower adjustment element, which is a predetermined metal element, or lanthanum (La) and nickel (Ni) as the lower adjustment element, which is a predetermined metal element. The lower adjustment layer 4 is formed of a material such as strontium ruthenate (SrRuO3:SRO) containing strontium and ruthenium, or lanthanum nickelate (LaNiO3:LNO) containing lanthanum and nickel. The lower adjustment layer 4 adjusts the crystal orientation of the piezoelectric layer 5. Specifically, the metal oxide forming the lower adjustment layer 4 is crystallized. The lower adjustment layer 4 functions as a seed layer (seed crystal layer) for aligning the crystal orientation of the piezoelectric layer 5 to a desired orientation. The lower adjustment layer 4 has a thickness of, for example, about 2 nm or more and about 40 nm or less.

[0026] The piezoelectric layer 5 is formed on the substrate 1 and on the lower adjustment layer 4. The piezoelectric layer 5 also contains lead zirconate titanate (PZT), which exhibits ferroelectricity. The piezoelectric layer 5 is formed of polycrystalline lead zirconate titanate. The piezoelectric layer 5 has a thickness of, for example, about 0.75 μm or more and about 5 μm or less.

[0027] 2, the piezoelectric layer 5 contains lead zirconate titanate having a perovskite structure. In a perovskite structure, a metal element is located at the A site, which is each vertex of a cubic crystal, and at the B site, which is the body center, with oxygen (O) located at the face center of each face centered on the B site. In lead zirconate titanate, lead (Pb) is located at the A site of the perovskite structure, and titanium (Ti) or zirconium (Zr) is located at the B site.

[0028] As shown in FIG. 1 , the upper adjustment layer 6 is formed on the piezoelectric layer 5 on the substrate 1. The upper adjustment layer 6 contains an upper adjustment element, which is a predetermined metal element shared with the lower adjustment layer 4, or an upper adjustment element, which is a predetermined metal element different from that of the lower adjustment layer 4. That is, the upper adjustment layer 6 contains a metal oxide. The upper adjustment layer 6 contains strontium (Sr) and ruthenium (Ru) as the upper adjustment element, which is a predetermined metal element, or lanthanum (La) and nickel (Ni) as the upper adjustment element, which is a predetermined metal element. The upper adjustment layer 6 is formed of a material such as strontium ruthenate (SrRuO:SRO) containing strontium and ruthenium, or lanthanum nickelate (LaNiO:LNO) containing lanthanum and nickel. For example, the upper adjustment layer 6 contains an upper adjustment element, which is a metal element shared with the lower adjustment element, which is a predetermined metal element, contained in the lower adjustment layer 4, and is a thin film of the same composition as the lower adjustment layer 4. As an example, the lower adjustment layer 4 and the upper adjustment layer 6 contain a common combination of metal elements and are formed of strontium ruthenate (SrRuO:SRO). The upper adjustment layer 6 functions as a barrier layer that prevents elements such as oxygen or lead in the piezoelectric layer 5 from migrating (diffusing) toward the upper electrode layer 7. The upper adjustment layer 6 may be crystalline or amorphous. The upper adjustment layer 6 is formed to a thickness of, for example, about 2 nm or more and about 40 nm or less.

[0029] The upper electrode layer 7 is formed on the upper adjustment layer 6 on the substrate 1. The upper electrode layer 7 is made of a material such as titanium (Ti), gold (Au), platinum (Pt), or iridium dioxide (IrO2). The upper electrode layer 7 has a thickness of, for example, about 50 nm or more and about 500 nm or less. The upper electrode layer 7 may be made of the same material as the lower electrode layer 3, or may be made of a different material from the lower electrode layer 3. The materials of the upper adjustment layer 6 and the upper electrode layer 7 of the upper electrode are not particularly limited. An insulating layer such as a silicon oxide layer may be formed on the upper electrode layer 7.

[0030] In the piezoelectric film substrate 100 according to this embodiment, after the upper electrode layer 7 is formed, the substrate 1 on which the piezoelectric layer 5 is formed is heated and held thereon to perform an annealing treatment to reduce lattice defects in the piezoelectric layer 5. In the annealing treatment, titanium, zirconium, and lead contained in the piezoelectric layer 5 are substituted by metal elements (strontium and ruthenium, or lanthanum and nickel) contained in the lower adjustment layer 4 and the upper adjustment layer 6 due to elemental diffusion caused by heat. The substitution by elemental diffusion occurs in a portion along the interface between the piezoelectric layer 5 and the lower adjustment layer 4 and in a portion along the interface between the piezoelectric layer 5 and the upper adjustment layer 6.

[0031] 3, in the piezoelectric film substrate 100, the piezoelectric layer 5 includes a lower diffusion layer 5a and an upper diffusion layer 5b. The lower diffusion layer 5a is maintained in a heated state for a predetermined period of time after the formation of the upper electrode layer 7, thereby substituting at least one of titanium, zirconium, and lead contained in the piezoelectric layer 5 with a predetermined metal element (lower adjustment element) contained in the lower adjustment layer 4 through elemental diffusion. The lower diffusion layer 5a is formed along the interface with the lower adjustment layer 4 on the lower side of the upper and lower sides of the piezoelectric layer 5. The lower diffusion layer 5a has a region in which the detection intensity ratio of the lower adjustment element (strontium and ruthenium, or lanthanum and nickel), which is the predetermined metal element contained in the lower diffusion layer 5a, is 10% or more higher than that of the portions of the piezoelectric layer 5 other than the lower diffusion layer 5a and the upper diffusion layer 5b. The upper diffusion layer 5b is heated for a predetermined period of time after the formation of the upper electrode layer 7, thereby substituting at least one of titanium, zirconium, and lead contained in the piezoelectric layer 5 with a predetermined metal element (upper adjustment element) contained in the upper adjustment layer 6 through elemental diffusion. The upper diffusion layer 5b is formed along the interface with the upper adjustment layer 6 on the upper side of the upper and lower sides of the piezoelectric layer 5. The upper diffusion layer 5b has a region in which the detection intensity ratio of the upper adjustment element (strontium and ruthenium, or lanthanum and nickel), which is the predetermined metal element contained in the upper diffusion layer 5b, is 10% or more higher than that of the portions of the piezoelectric layer 5 other than the lower diffusion layer 5a and the upper diffusion layer 5b. The detection intensity ratio between the lower adjustment element and the upper adjustment element is detected, for example, by SIMS (secondary ion mass spectrometry).

[0032] 4 , in this embodiment, the piezoelectric layer 5 is formed by sputtering using a sputtering device 101. The sputtering device 101 is configured to sputter target particles (sputtered particles) from a target member 102 containing titanium (Ti), zirconium (Zr), and lead (Pb), which are materials for the piezoelectric layer 5, and to deposit the sputtered particles on the substrate 1, thereby forming a thin film from the sputtered particles from the target member 102 on the substrate 1 (piezoelectric film substrate 100). The sputtering device 101 includes a mounting table 11, a heating device 12, a film formation chamber 13, and a vacuum pump 14.

[0033] The sputtering apparatus 101 introduces gases such as argon (Ar) and oxygen (O) into the deposition chamber 13, which has been evacuated to a vacuum by the vacuum pump 14. The sputtering apparatus 101 then applies a voltage to a target member 102 disposed in the deposition chamber 13 to generate plasma within the deposition chamber 13. Charged particles (e.g., argon ions) in the plasma collide with the target member 102, causing sputter particles containing titanium (Ti), zirconium (Zr), and lead (Pb) to be emitted (knocked out) from the target member 102. The emitted sputter particles then adhere to the substrate 1 (piezoelectric film substrate 100) placed on the mounting table 11, forming a thin film on the surface of the substrate 1 and forming the piezoelectric layer 5.

[0034] In the sputtering apparatus 101, the heating device 12 is configured to heat the substrate 1 placed on the mounting table 11. Specifically, the heating device 12 has a heating surface along the main surface of the substrate 1 on the side where the substrate 1 is placed. The heating device 12 includes, for example, an electric heating wire. In the sputtering apparatus 101, sputtering is performed on the substrate 1 placed in the film formation chamber 13 and heated to a predetermined film formation temperature. The heating device 12 is controlled so that the substrate 1 is maintained at the predetermined film formation temperature during the period in which sputtering is performed. In other words, the output of the heating device 12 is controlled so that the substrate 1 is maintained at a predetermined constant film formation temperature during the period in which film formation by sputtering is performed. For example, when a 2 μm thick piezoelectric layer 5 is to be formed, film formation by sputtering is performed for approximately 20 minutes.

[0035] The sputtering apparatus 101 also includes a control device 15. The control device 15 controls each part of the sputtering apparatus 101. The control device 15 includes, for example, an arithmetic unit including a CPU (Central Processing Unit) and a storage device such as a flash memory. The control device 15 controls sputtering by the sputtering apparatus 101 based on programs and parameters stored in the storage device. Specifically, the control device 15 controls the application of voltage to the target member 102, the operation of the vacuum pump 14, and the operation of the heating device 12.

[0036] <Heat Treatment Furnace> As shown in FIG. 5 , in this embodiment, an annealing process is performed on the substrate 1 (piezoelectric film substrate 100) on which the upper electrode layer 7 has been formed in a heat treatment furnace 103, which is different from the film formation chamber 13 of the sputtering apparatus 101. The annealing process involves holding the substrate 1 (piezoelectric film substrate 100) in a heated state for a predetermined period of time. Furthermore, in the annealing process, a batch process is performed in which a plurality of substrates 1 are annealed together in one heat treatment furnace 103. The heat treatment furnace 103 has a heater 21 disposed therein. The heat treatment furnace 103 is configured to accommodate a plurality of substrates 1 (a plurality of piezoelectric film substrates 100) therein. The plurality of substrates 1 are arranged in a row along the main surfaces within the heat treatment furnace 103. The plurality of substrates 1 arranged in a row are held in a heated state in the heat treatment furnace 103, thereby performing a collective annealing process on the plurality of substrates 1. In the heat treatment furnace 103, the substrates 1 are heated in an oxygen atmosphere, for example, to which oxygen is supplied.

[0037] (Method for manufacturing piezoelectric film substrate) Next, a method for manufacturing the piezoelectric film substrate 100 will be described with reference to Fig. 6. The method for manufacturing the piezoelectric film substrate 100 is a method for manufacturing a piezoelectric film substrate that is divided into a plurality of individual pieces that each become a device.

[0038] 6, the manufacturing method of the piezoelectric film substrate 100 includes step S1, which is a process of preparing the substrate 1, step S2, which is a process of forming the insulating layer 2, step S3, which is a process of forming the lower electrode layer 3 on the substrate 1, step S4, which is a process of forming the lower adjustment layer 4, step S5, which is a process of depositing the piezoelectric layer 5 on the lower adjustment layer 4, step S6, which is a process of forming the upper adjustment layer 6 on the piezoelectric layer 5, step S7, which is a process of forming the upper electrode layer 7 on the substrate 1, and step S8, which is a process of holding the piezoelectric film substrate 100 for a predetermined period of time. In the manufacturing method of the piezoelectric film substrate 100 according to this embodiment, steps S1 to S8 are performed in this order.

[0039] First, in step S1, a silicon substrate is prepared as the substrate 1. Then, in step S2, a silicon (Si) substrate constituting the substrate 1 is thermally oxidized at a temperature of about 700° C. to form the insulating layer 2, which is a silicon oxide layer made of SiO2, on the surface of the substrate 1.

[0040] Next, in step S3, in the process of forming the lower electrode layer 3 on the substrate 1, the lower electrode layer 3 is formed by sputtering so as to be laminated on the insulating layer 2 on the substrate 1. Then, in step S4, in the process of forming the lower adjustment layer 4, after the lower electrode layer 3 is formed, the lower adjustment layer 4 is formed by sputtering on the lower electrode layer 3 on the substrate 1. In the process of forming the lower adjustment layer 4, the substrate 1 is heated to, for example, about 500° C. This crystallizes the metal oxide in the lower adjustment layer 4. The lower electrode layer 3 and the lower adjustment layer 4 may be formed using a common sputtering apparatus, or may be formed using different sputtering apparatuses.

[0041] Then, in step S5, in the process of depositing the piezoelectric layer 5 on the lower adjustment layer 4, the piezoelectric layer 5 is deposited on the lower adjustment layer 4 formed on the substrate 1 by sputtering in a state heated to a predetermined deposition set temperature. Note that the sputtering for depositing the piezoelectric layer 5 is performed by a sputtering apparatus 101 different from the sputtering apparatus for forming the lower electrode layer 3 and the lower adjustment layer 4.

[0042] In this embodiment, in the process of forming the piezoelectric layer 5 on the lower adjustment layer 4, the substrate 1 (piezoelectric film substrate 100) placed in the film-forming chamber 13 of the sputtering apparatus 101 is heated to a predetermined film-forming temperature by the heating device 12, and the piezoelectric layer 5 is formed by sputtering using sputter particles from the target member 102. Sputtering is performed while the film-forming chamber 13 is evacuated by the vacuum pump 14. Note that "vacuum" here refers to a pressure lower than atmospheric pressure. In the sputtering apparatus 101, the control device 15 heats the substrate 1 on which the lower adjustment layer 4 has been formed to a predetermined film-forming temperature by the heating device 12. The control device 15 then initiates sputtering to form the piezoelectric layer 5 on the substrate 1 heated to the film-forming temperature. The control device 15 performs sputtering by applying a voltage to the target member 102 for a predetermined period of time until the piezoelectric layer 5 is formed to a predetermined thickness. The control device 15 controls the operation of the heating device 12 so that the substrate 1 is maintained at a predetermined film-forming temperature during the period in which the piezoelectric layer 5 is formed by sputtering. Then, after a predetermined period (e.g., 20 minutes) has elapsed, sputtering is stopped. The predetermined film-forming temperature is approximately 560°C or higher and approximately 700°C or lower. For example, the predetermined film-forming temperature is approximately 600°C. The predetermined film-forming temperature is the temperature of the substrate 1 set as a target for heating by the heating device 12. In other words, the predetermined film-forming temperature does not include temperature changes of the substrate 1 due to factors other than the heating device 12. The actual temperature of the substrate 1 may differ from the predetermined film-forming temperature set as a target depending on factors such as the presence or absence of plasma during sputtering. Furthermore, if the sputtering device 101 is equipped with a display unit that displays the temperature of the substrate 1, the temperature displayed on the display unit may differ from the actual temperature of the substrate 1. The "predetermined film formation set temperature" is a temperature set as a target that does not include temperature changes of the substrate 1 due to factors other than the heating device, and an error occurs between the predetermined film formation set temperature and the actual temperature of the substrate 1 due to factors other than the heating device.The substrate 1 is heated so as to crystallize the lead zirconate titanate with a perovskite structure.

[0043] Then, in step S6, in the process of forming the upper adjustment layer 6 on the piezoelectric layer 5, the upper adjustment layer 6 is formed by sputtering so as to be laminated on the piezoelectric layer 5 on the substrate 1. Then, in step S7, in the process of forming the upper electrode layer 7 on the substrate 1, after the upper adjustment layer 6 is formed, the upper electrode layer 7 is formed by sputtering on the upper adjustment layer 6 on the substrate 1. For example, the process of forming the upper adjustment layer 6 and the upper electrode layer 7 is performed without heating the substrate 1 (piezoelectric film substrate 100). Furthermore, the upper adjustment layer 6 and the upper electrode layer 7 may be formed by a common sputtering apparatus, or may be formed by different sputtering apparatuses.

[0044] Then, in step S8, in the process of holding the substrate 1 (piezoelectric film substrate 100) for a predetermined period, after the process of forming the upper adjustment layer 6 (step S6) and the process of forming the upper electrode layer 7 (step S7), the substrate 1 (piezoelectric film substrate 100) on which the piezoelectric layer 5 has been formed is held in a heated state for a predetermined period. That is, the substrate 1 on which the upper adjustment layer 6 and the upper electrode layer 7 have been formed is subjected to an annealing process in step S8, which is a process of holding the substrate 1 for a predetermined period. Note that in the process of holding the substrate 1 for a predetermined period in step S8, the substrate 1 is placed in a heat treatment furnace 103 different from the film formation chamber 13 in which the piezoelectric layer 5 is formed, and is held in a heated state at a temperature higher than the predetermined film formation set temperature during sputtering for a predetermined period. In step S8, the substrate 1 is held in the heat treatment furnace 103, and oxygen is supplied to create an oxygen atmosphere inside the heat treatment furnace 103. In the heat treatment furnace 103, a control device (not shown) controls the operation of the heater 21, thereby continuously heating the substrate 1 at a temperature higher than the predetermined film-forming temperature. In step S8, the substrate 1 is held in a heated state at 550°C or higher and 650°C or lower. In the heat treatment furnace 103, the substrate 1 is held in a heated state at approximately 650°C, which is higher than the film-forming temperature of approximately 600°C. The predetermined period during which the substrate 1 is held heated to the predetermined film-forming temperature by the annealing treatment after film formation in step S8 is 5 minutes or longer but shorter than 60 minutes, preferably 20 minutes or longer but 40 minutes or shorter, and more preferably 30 minutes.

[0045] In this embodiment, the annealing treatment in step S8 reduces lattice defects such as oxygen vacancies and lead vacancies contained in the piezoelectric layer 5. The annealing treatment after the deposition of the piezoelectric layer 5 causes the metal elements (lower adjustment elements) contained in the lower adjustment layer 4 below the piezoelectric layer 5 and the metal elements (upper adjustment elements) contained in the upper adjustment layer 6 above the piezoelectric layer 5 to diffuse into the piezoelectric layer 5 by elemental diffusion. This elemental diffusion replaces titanium (Ti), zirconium (Zr), and lead (Pb) in the lead zirconate titanate of the piezoelectric layer 5 with strontium and ruthenium (Sr and Ru), or lanthanum and nickel (La and Ni), in the lower adjustment layer 4 and the upper adjustment layer 6, respectively. For example, when the lower adjustment layer 4 and the upper adjustment layer 6 are formed of lanthanum nickelate (LaNiO), titanium (Ti) or zirconium (Zr) located at the B site of the piezoelectric layer 5 is replaced with lanthanum (La) or nickel (Ni) in the lower adjustment layer 4 and the upper adjustment layer 6. When titanium (Ti) or zirconium (Zr) with a valence of 4+ is replaced with lanthanum (La) or nickel (Ni) with a valence of 2+ or 3+, the number of lead vacancies that can be regarded as anions decreases in order to maintain electrical neutrality. Furthermore, when lead (Pb) with a valence of 2+ located at the A site of the piezoelectric layer 5 is replaced with lanthanum (La) with a valence of 3+, the number of oxygen vacancies that can be regarded as cations decreases in order to maintain electrical neutrality. In this way, the titanium, zirconium, and lead contained in the piezoelectric layer 5 are each replaced with a metal element having a different valence, thereby reducing lattice defects such as oxygen vacancies and lead vacancies contained in the piezoelectric layer 5.

[0046] Furthermore, in this embodiment, in the process of holding the substrate 1 (piezoelectric film substrate 100) for a predetermined period in step S8, a plurality of substrates 1 (piezoelectric film substrates 100) are annealed together. Specifically, the plurality of substrates 1 are placed in a heat treatment furnace 103 and held together for a predetermined period in a heated state. That is, the processes of steps S1 to S7 are repeated multiple times, or multiple production lines are prepared and multiple substrates are manufactured in parallel, thereby manufacturing a plurality of substrates 1 each having an upper electrode layer 7 formed thereon, and the process of step S8 is performed so that the plurality of substrates 1 each having an upper electrode layer 7 formed thereon are held together in a heated state in the heat treatment furnace 103. For example, 20 to 100 substrates 1 are heated together in the heat treatment furnace 103. The piezoelectric film substrate 100 is manufactured through the processes of steps S1 to S8.

[0047] Thereafter, when processing into a shape for a device is performed, for example, photolithography is used to process the lower electrode (lower electrode layer 3 and lower adjustment layer 4), the piezoelectric layer 5, and the upper electrode (upper adjustment layer 6 and upper electrode layer 7) into a shape for the device. In the case of photolithography, wet etching using an etching solution or dry etching using an etching gas is used to remove unnecessary portions and leave necessary portions, thereby processing the piezoelectric film substrate 100 into a shape for the device. Furthermore, when the piezoelectric film substrate 100 is divided into individual pieces for the device, the piezoelectric film substrate 100 is cut into the individual pieces for the device using, for example, a blade.

[0048] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0049] In this embodiment, as described above, the manufacturing method of the piezoelectric film substrate 100 includes, after the step of forming the upper electrode layer 7 (step S7), the step of holding the substrate 1 in a heated state for a predetermined period of time (step S8). This allows the upper adjustment layer 6 below the upper electrode layer 7 to function as a barrier, thereby preventing lead from being released from the surface of the piezoelectric layer 5 even when the substrate 1 is heated. Therefore, even when the substrate 1 is heated in a space other than a lead atmosphere, a decrease in the withstand voltage performance of the piezoelectric layer 5 due to lead release can be prevented. In this embodiment, as described above, the manufacturing method of the piezoelectric film substrate 100 includes the steps of: forming the piezoelectric layer 5 containing lead zirconate titanate having a perovskite structure on the lower adjustment layer 4 containing the lower adjustment element, which is a predetermined metal element (step S5); and forming the upper adjustment layer 6 containing the upper adjustment element, which is a predetermined metal element, on the piezoelectric layer 5 (step S6). As a result, by heating the substrate 1 with the piezoelectric layer 5 sandwiched between the upper adjustment layer 6 and the lower adjustment layer 4, the titanium, zirconium, and lead elements contained in the piezoelectric layer 5 can be replaced by metal elements contained in each of the upper adjustment layer 6 and the lower adjustment layer 4 through elemental diffusion. Therefore, at both the upper and lower interfaces of the piezoelectric layer 5, the titanium, zirconium, and lead contained in the piezoelectric layer 5 are replaced with metal elements having different valences, thereby reducing lattice defects such as oxygen vacancies and lead vacancies contained in the piezoelectric layer 5 and improving the voltage resistance of the piezoelectric layer 5. As a result, the voltage resistance of the piezoelectric layer 5 can be improved while suppressing the release of lead elements without heating the substrate 1 in a space containing a lead atmosphere, thereby suppressing the adhesion of lead to the heating device (heat treatment furnace 103) that heats the substrate 1 and easily improving the voltage resistance of the piezoelectric layer 5 containing lead zirconate titanate.

[0050] In this embodiment, as described above, the method for manufacturing the piezoelectric film substrate 100 includes a step (step S5) of forming a piezoelectric layer 5 on the lower adjustment layer 4 formed on the substrate 1 placed in the deposition chamber 13. The method for manufacturing the piezoelectric film substrate 100 also includes a step (step S8) of holding the substrate 1 in a heated state for a predetermined period of time in a heat treatment furnace 103 different from the deposition chamber 13. Here, if the substrate 1 is held in a heated state in the deposition chamber 13 in order to improve crystallinity, particles may be generated due to peeling off of the material of the piezoelectric layer 5 adhering to the inner wall of the deposition chamber 13, etc. Furthermore, if the substrate 1 is heated in the deposition chamber 13, the thermal load on the apparatus for forming the piezoelectric layer 5, including the deposition chamber 13, increases. In contrast, in this embodiment, the substrate 1 placed in a heat treatment furnace 103, which is different from the deposition chamber 13, is maintained in a heated state for a predetermined period of time. This suppresses the generation of particles that could cause a decrease in the performance of the resulting piezoelectric film substrate 100, and also suppresses an increase in the burden (load) on the apparatus, including the deposition chamber 13, in which the piezoelectric layer 5 is deposited. Furthermore, in this embodiment, a step (step S8) of maintaining the heated substrate 1 for a predetermined period of time is performed in a heat treatment furnace 103, which is different from the apparatus (sputtering apparatus) in which the upper electrode layer 7 is formed. Here, since the upper electrode layer 7 is generally formed at room temperature without heating the substrate 1, if a step of maintaining the substrate 1 in a heated state is performed in the apparatus in which the upper electrode layer 7 is formed, an additional heating device must be provided in the apparatus in which the upper electrode layer 7 is formed. This requires the apparatus to be equipped with heating functions and heat resistance that are unnecessary for forming the upper electrode layer 7, and also increases the thermal burden on the apparatus in which the upper electrode layer 7 is formed.In contrast to this, as in the present embodiment, by performing a process (step S8) of holding the heated substrate 1 for a predetermined period of time in a heat treatment furnace 103 that is different from the apparatus (sputtering apparatus) in which the upper electrode layer 7 is formed, it is possible to prevent components unnecessary for forming the upper electrode layer 7 from being placed in the apparatus in which the upper electrode layer 7 is formed, and to prevent an increase in the burden on the apparatus in which the upper electrode layer 7 is formed.

[0051] In this embodiment, as described above, the method for manufacturing the piezoelectric film substrate 100 includes a step (step S8) of holding the plurality of substrates 1 collectively for a predetermined period in a heated state, the plurality of substrates 1 being placed in the heat treatment furnace 103. This configuration makes it possible to shorten the time required to manufacture the plurality of piezoelectric film substrates 100 compared to holding the plurality of substrates 1 (piezoelectric film substrates 100) one by one in a heated state.

[0052] In this embodiment, as described above, the manufacturing method of the piezoelectric film substrate 100 includes a step (step S4) of forming a lower adjustment layer 4 containing strontium and ruthenium as lower adjustment elements or containing lanthanum and nickel as lower adjustment elements, and adjusting the crystal orientation of the piezoelectric layer 5. The manufacturing method of the piezoelectric film substrate 100 also includes a step (step S6) of forming an upper adjustment layer 6 containing strontium and ruthenium as upper adjustment elements or containing lanthanum and nickel as upper adjustment elements. With this configuration, by forming the piezoelectric layer 5 on the lower adjustment layer 4, the crystal orientation of the piezoelectric layer 5 is adjusted, thereby further improving the crystallinity of the piezoelectric layer 5. Furthermore, strontium, ruthenium, lanthanum, and nickel all tend to become cations with smaller valences than titanium and zirconium contained in the lead zirconate titanate of the piezoelectric layer 5. Therefore, when titanium and zirconium in the piezoelectric layer 5 are replaced by any of strontium, ruthenium, lanthanum, and nickel through elemental diffusion, the charge of the entire piezoelectric layer 5 tends to decrease, and the charge increases to maintain electrical neutrality, thereby reducing the number of lead vacancies in the piezoelectric layer 5. Furthermore, when lead in the piezoelectric layer 5 is replaced by a metal element with a higher valence than lead, such as lanthanum, through elemental diffusion, the charge of the entire piezoelectric layer 5 decreases to maintain electrical neutrality, thereby reducing the number of oxygen vacancies in the piezoelectric layer 5. Therefore, since the piezoelectric layer 5 is sandwiched between the lower adjustment layer 4 and the upper adjustment layer 6, each containing strontium and ruthenium or lanthanum and nickel, elemental diffusion can occur at both the upper and lower interfaces of the piezoelectric layer 5 to reduce the number of vacancies in the piezoelectric layer 5 and further improve the withstand voltage performance. As a result, the withstand voltage performance of the piezoelectric layer 5 can be further improved.

[0053] In this embodiment, as described above, the manufacturing method of the piezoelectric film substrate 100 includes a step (step S6) of forming an upper adjustment layer 6 that contains an upper adjustment element that is a metal element common to the lower adjustment element contained in the lower adjustment layer 4 and has the same composition as the lower adjustment layer 4. With this configuration, both the upper adjustment layer 6 and the lower adjustment layer 4 can be formed from the same material. Therefore, compared to when the upper adjustment layer 6 and the lower adjustment layer 4 contain different metal elements, the number of types of materials used to manufacture the piezoelectric film substrate 100 can be reduced, and the effort required to manufacture the piezoelectric film substrate 100 can be reduced.

[0054] In this embodiment, as described above, the manufacturing method of the piezoelectric film substrate 100 includes a step (step S8) of holding the substrate 1 in a heated state for a predetermined period of time that is at least 5 minutes but less than 60 minutes. Here, if the period for holding the substrate 1 in a heated state is too short, element diffusion from the lower adjustment layer 4 and the upper adjustment layer 6 becomes difficult, resulting in insufficient improvement in the voltage resistance performance of the piezoelectric layer 5. Furthermore, if the period for holding the substrate 1 in a heated state is too long, the characteristics of the piezoelectric layer 5 deteriorate due to excessive element substitution caused by element diffusion from the lower adjustment layer 4 and the upper adjustment layer 6. In contrast, in this embodiment, by holding the substrate 1 in a heated state for a predetermined period of time that is at least 5 minutes but less than 60 minutes, the substrate 1 can be held in a heated state for an appropriate length of time. Therefore, the voltage resistance performance of the piezoelectric layer 5 can be further improved compared to when the holding period is too short or too long.

[0055] In this embodiment, as described above, the manufacturing method of the piezoelectric film substrate 100 includes a step (step S5) of forming the piezoelectric layer 5 on the lower adjustment layer 4 by sputtering while the substrate 1 is heated to a predetermined film-forming temperature by the heating device 12. The manufacturing method of the piezoelectric film substrate 100 also includes a step (step S8) of holding the substrate 1 for a predetermined period in a state in which the substrate 1 is heated at a temperature higher than the predetermined film-forming temperature during the sputtering process for forming the piezoelectric layer 5. Since substitution due to elemental diffusion progresses as the temperature increases, holding the substrate 1 in a state in which the substrate 1 is heated at a temperature higher than the predetermined film-forming temperature during the sputtering process for forming the piezoelectric layer 5 allows the substrate 1 to be held in a state in which it is heated at a sufficiently high temperature. This prevents insufficient elemental diffusion and insufficient improvement in voltage resistance performance due to an excessively low heating temperature.

[0056] (Modifications) The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above-mentioned embodiments, and includes all modifications (modifications) within the meaning and scope of the claims.

[0057] For example, in the above embodiment, the lower adjustment layer 4 and the upper adjustment layer 6 contain strontium and ruthenium, or lanthanum and nickel, but the present invention is not limited to this. In the present invention, the lower adjustment layer and the upper adjustment layer may be configured to contain metal elements other than strontium and ruthenium, or lanthanum and nickel. Furthermore, the lower adjustment layer may not have the function of adjusting the crystal orientation of the piezoelectric layer. Furthermore, the lower adjustment layer and the upper adjustment layer may contain different combinations of metal elements. For example, the lower adjustment layer may be lanthanum nickelate (LaNiO3:LNO), and the upper adjustment layer may be strontium ruthenate (SrRuO3:SRO). Furthermore, the lower adjustment layer and the upper adjustment layer may be multilayer films.

[0058] In the above embodiment, the lower electrode layer 3, the lower adjustment layer 4, the piezoelectric layer 5, the upper adjustment layer 6, and the upper electrode layer 7 are each formed by sputtering. However, the present invention is not limited to this. In the present invention, any of the lower electrode layer 3, the lower adjustment layer 4, the piezoelectric layer 5, the upper adjustment layer 6, and the upper electrode layer 7 may be formed by a method other than sputtering. For example, the lower electrode layer or the upper electrode layer may be formed by vacuum deposition. The piezoelectric layer may be formed by pulsed laser deposition (PLD), chemical vapor deposition (CVD), a sol-gel method, or the like. The lower electrode layer, the lower adjustment layer, the piezoelectric layer, the upper adjustment layer, and the upper electrode layer may be formed (deposited) using a common sputtering apparatus. The piezoelectric layer may be single crystal or polycrystalline.

[0059] In the above embodiment, an example was shown in which a plurality of substrates 1 were held in a heated state for a predetermined period in a heat treatment furnace 103 different from the deposition chamber 13 in which the piezoelectric layer 5 was deposited. However, the present invention is not limited to this. In the present invention, the substrates 1 may be held in a heated state one by one. In this case, the substrates may be held in a heated state for a predetermined period in the device in which the upper electrode layer was formed. Furthermore, when the piezoelectric layer, the upper adjustment layer, and the upper electrode layer are formed (deposited) using a common sputtering device, after the upper electrode layer is formed, the substrates may be held in a heated state for a predetermined period in the sputtering device used in the deposition of the piezoelectric layer.

[0060] In the above embodiment, the substrate 1 is held in a heated state for a predetermined period of 5 minutes or more and less than 60 minutes after the upper electrode layer 7 is formed, but the present invention is not limited to this. In the present invention, the substrate may be held in a heated state for a predetermined period of 60 minutes or more.

[0061] In the above embodiment, the set temperature during deposition of the piezoelectric layer 5 is 560° C. or higher and 700° C. or lower, and the substrate 1 is maintained in a heated state at a temperature higher than the set temperature during deposition of the piezoelectric layer 5 for a predetermined period of time. However, the present invention is not limited to this. In the present invention, the set temperature during deposition of the piezoelectric layer may be lower than 560° C. or higher than 700° C. Furthermore, after the step of forming the upper adjustment layer, the substrate may be maintained in a heated state at a temperature lower than the set temperature during deposition or at the same temperature as the set temperature during deposition for a predetermined period of time.

[0062] In the above embodiment, the lower electrode layer 3 and the upper electrode layer 7 are formed of a metal material such as platinum (Pt) or iridium (Ir), but the present invention is not limited to this. In the present invention, the lower electrode layer and the upper electrode layer may be formed of a material containing titanium (Ti) or gold (Au). They may also be formed of a material such as cerium oxide (CeO), high-temperature copper oxide superconductor (LSCO), lanthanum (La), or strontium (Sr). The lower electrode layer and the upper electrode layer may also be formed of different materials.

[0063] REFERENCE SIGNS LIST 1 substrate 2 insulating layer 3 lower electrode layer 4 lower adjustment layer 5 piezoelectric layer 5a lower diffusion layer 5b upper diffusion layer 6 upper adjustment layer 7 upper electrode layer 12 heating device 13 film formation chamber 100 piezoelectric film substrate 101 sputtering device 102 target member 103 heat treatment furnace

Claims

1. A method for manufacturing a piezoelectric film substrate, comprising the steps of: forming a lower electrode layer on a substrate; forming a lower adjustment layer on the lower electrode layer, the lower adjustment layer including a lower adjustment element which is a predetermined metal element; depositing a piezoelectric layer including lead zirconate titanate having a perovskite structure on the lower adjustment layer; forming an upper adjustment layer on the piezoelectric layer, the upper adjustment layer including an upper adjustment element which is a predetermined metal element; forming an upper electrode layer on the upper adjustment layer; and, after the step of forming the upper electrode layer, holding the substrate in a heated state for a predetermined period of time.

2. A method for manufacturing a piezoelectric film substrate as described in claim 1, wherein the step of depositing the piezoelectric layer includes a step of depositing the piezoelectric layer on the lower adjustment layer formed on the substrate placed in a deposition chamber, and the step of holding the substrate for the predetermined period includes a step of holding the substrate for the predetermined period in a heated state, the substrate being placed in a heat treatment furnace different from the deposition chamber.

3. A method for manufacturing a piezoelectric film substrate as described in claim 2, wherein the step of holding the substrate for the specified period includes a step of holding the substrates together for the specified period in a heated state in the heat treatment furnace.

4. A method for manufacturing a piezoelectric film substrate as described in claim 1, wherein the step of forming the lower adjustment layer includes a step of forming the lower adjustment layer containing strontium and ruthenium as the lower adjustment elements, or containing lanthanum and nickel as the lower adjustment elements, and adjusting the crystal orientation of the piezoelectric layer, and the step of forming the upper adjustment layer includes a step of forming the upper adjustment layer containing strontium and ruthenium as the upper adjustment elements, or containing lanthanum and nickel as the upper adjustment elements.

5. A method for manufacturing a piezoelectric film substrate as described in claim 4, wherein the step of forming the upper adjustment layer includes a step of forming the upper adjustment layer containing the upper adjustment element which is a common metal element with the lower adjustment element contained in the lower adjustment layer and having the same composition as the lower adjustment layer.

6. A method for manufacturing a piezoelectric film substrate as described in claim 1, wherein the step of holding the substrate for the predetermined period of time includes a step of holding the substrate in a heated state for the predetermined period of time that is greater than or equal to 5 minutes and less than 60 minutes.

7. A method for manufacturing a piezoelectric film substrate as described in claim 1, wherein the step of depositing the piezoelectric layer includes a step of depositing the piezoelectric layer on the lower adjustment layer by sputtering while the substrate is heated to a predetermined deposition set temperature by a heating device, and the step of holding the substrate for the predetermined period includes a step of holding the substrate for the predetermined period while the substrate is heated to a temperature higher than the predetermined deposition set temperature during sputtering to deposit the piezoelectric layer.

8. A piezoelectric device comprising: a lower electrode layer formed on a substrate; a lower adjustment layer formed on the lower electrode layer and containing a lower adjustment element which is a predetermined metal element; a piezoelectric layer containing lead zirconate titanate having a perovskite structure formed on the lower adjustment layer; an upper adjustment layer formed on the piezoelectric layer and containing an upper adjustment element which is a predetermined metal element; and an upper electrode layer formed on the upper adjustment layer, wherein the piezoelectric layer includes a lower diffusion layer formed along the interface with the lower adjustment layer and an upper diffusion layer formed along the interface with the upper adjustment layer, the lower diffusion layer having a thickness of 10% or less of the entire film thickness of the piezoelectric layer, at least one of titanium, zircon and lead contained in the piezoelectric layer is substituted by the lower adjustment element contained in the lower adjustment layer by elemental diffusion, the lower diffusion layer has a thickness of 10% or less of the entire film thickness of the piezoelectric layer, A piezoelectric film substrate, in which at least one of titanium, zircon, and lead contained in the piezoelectric layer is replaced by the upper adjustment element contained in the upper adjustment layer by elemental diffusion, and the piezoelectric film substrate has an area in which the detection intensity ratio of the upper adjustment element contained in the upper diffusion layer is 10% or more higher than that of the portion of the piezoelectric layer other than the upper diffusion layer and the lower diffusion layer.

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