Method for manufacturing piezoelectric film substrate, and piezoelectric film substrate

Abstract

The method for manufacturing a piezoelectric film substrate includes: a step of forming a lower electrode layer on a substrate; a step for forming an adjustment layer containing a predetermined metal element on the lower electrode layer; a step in which a piezoelectric layer containing lead zirconate titanate having a perovskite structure is formed on the adjustment layer in a state in which the substrate is heated by a heating device at a predetermined set temperature for film formation; a step in which the substrate is continuously held for a predetermined period of time in a state in which the substrate is heated at a predetermined set temperature during film formation, following the step in which the piezoelectric layer is formed; and a step of forming an upper electrode layer after the step of holding the substrate for the predetermined period of time.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of a piezoelectric film substrate and a piezoelectric film substrate, and particularly relates to a manufacturing method of a piezoelectric film substrate in which a piezoelectric layer containing lead zirconate titanate having a perovskite structure is formed, and a piezoelectric film substrate. BACKGROUND

[0002] In the past, a method of forming a lead zirconate titanate film having a perovskite structure is known. Such a method is disclosed in Japanese Patent No. 6030418, for example.

[0003] In Japanese Patent No. 6030418, a method of forming a lead zirconate titanate film on a silicon substrate on which a platinum film is formed is disclosed. In the method of forming the lead zirconate titanate film, the lead zirconate titanate film is formed on the platinum film formed as a lower electrode on the silicon substrate. During a film forming process of forming the lead zirconate titanate film on the platinum film, the silicon substrate is maintained at a predetermined temperature by operating a heating mechanism. Further, in the method of forming the lead zirconate titanate film disclosed in Japanese Patent No. 6030418, after the film forming process of the lead zirconate titanate film, the silicon substrate is maintained at a higher temperature than that in the film forming process by the heating mechanism, thereby improving the crystallinity of the formed lead zirconate titanate film, and thus improving the voltage resistance performance.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent No. 6030418

[0007] SUMMARY OF THE INVENTION

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, in the method of forming the lead zirconate titanate film disclosed in Japanese Patent No. 6030418, the substrate on which the lead zirconate titanate film (piezoelectric layer) is formed is maintained at a temperature higher than that at the time of film formation by heating. Therefore, since the thermal expansion coefficient of the piezoelectric layer and the thermal expansion coefficient of the lower electrode are different from each other, the film stress of the piezoelectric layer increases due to heating. Therefore, it is desired to suppress the increase in the film stress and the like due to heating, and to improve the voltage resistance performance.

[0010] The present application has been achieved in order to solve the above problems, and an object of the present application is to provide a manufacturing method of a piezoelectric film substrate and a piezoelectric film substrate capable of suppressing the increase in the film stress and the like due to heating, and improving the voltage resistance performance.

[0011] MEANS FOR SOLVING THE PROBLEMS

[0012] To achieve the above object, a method for manufacturing a piezoelectric film substrate according to a first aspect of the present application includes: a step of forming a lower electrode layer on a substrate; a step of forming an adjustment layer containing a prescribed metal element on the lower electrode layer; a step of forming a piezoelectric layer on the adjustment layer in a state where the substrate is heated at a prescribed film formation time set temperature by a heating device, the piezoelectric layer containing lead zirconate titanate having a perovskite structure; a step of continuously, after the step of forming the piezoelectric layer, maintaining the substrate in a state where the substrate is heated at the prescribed film formation time set temperature for a prescribed period; and a step of forming an upper electrode layer after the step of maintaining the substrate for the prescribed period. Here, the "prescribed film formation time set temperature" refers to a substrate temperature set as a heating target of the heating device. That is, the "prescribed film formation time set temperature" is a temperature set as a target not including a change in the substrate temperature caused by factors other than the heating device, and there is an error between the "prescribed film formation time set temperature" and an actual substrate temperature due to factors other than the heating device.

[0013] As described above, the method for manufacturing a piezoelectric film substrate according to the first aspect of the present application includes: a step of continuously, after the step of forming the piezoelectric layer in a state where the substrate is heated at the prescribed film formation time set temperature, maintaining the substrate in a state where the substrate is heated at the prescribed film formation time set temperature for a prescribed period. Thus, unlike a case where the substrate is maintained in a state where the substrate is heated at a temperature higher than the film formation time set temperature at which the piezoelectric layer is formed, it is possible to suppress an increase in film stress and the like in the piezoelectric layer formed on the substrate due to heating. Also, as described above, the method for manufacturing a piezoelectric film substrate according to the first aspect of the present application includes the step of forming the piezoelectric layer on the adjustment layer containing the prescribed metal element, and thus, by maintaining the substrate on which the piezoelectric layer is formed on the adjustment layer in a state where the substrate is heated at the prescribed film formation time set temperature, it is possible to replace the titanium, zirconium, and lead elements contained in the piezoelectric layer with the metal elements contained in the adjustment layer by element diffusion. Thus, the titanium, zirconium, and lead elements contained in the piezoelectric layer are replaced with metal elements having different valence states, respectively, and thus it is possible to reduce lattice defects such as oxygen vacancies and lead vacancies contained in the piezoelectric layer, and thus it is possible to improve the voltage resistance performance of the piezoelectric layer. Also, in a case where the substrate is maintained at a temperature lower than the prescribed film formation time set temperature at which the piezoelectric layer is formed, since element diffusion from the adjustment layer is less likely to occur, the improvement in the voltage resistance performance of the piezoelectric layer is insufficient. In contrast, in the present application, since the substrate is maintained for a prescribed period in a state where the substrate is heated at the prescribed film formation time set temperature at which the piezoelectric layer is formed, it is possible to suppress the insufficient improvement in the voltage resistance performance. As a result, it is possible to suppress an increase in the effects due to heating, and it is possible to improve the voltage resistance performance.

[0014] In the method for manufacturing a piezoelectric film substrate according to the first aspect above, preferably, the step of forming an adjustment layer includes the following step: forming an adjustment layer containing strontium and ruthenium as specified metals, or containing lanthanum and nickel as specified metals, and used to adjust the crystal orientation of the piezoelectric layer. If configured in this way, by forming a piezoelectric layer on the adjustment layer, the crystal orientation of the piezoelectric layer can be adjusted, thus further improving the crystallinity of the piezoelectric layer. Furthermore, compared to titanium and zirconium contained in lead zirconate titanate of the piezoelectric layer, strontium, ruthenium, lanthanum, and nickel are all more likely to become cations with lower valence states. Therefore, when titanium and zirconium in the piezoelectric layer are replaced by any one of strontium, ruthenium, lanthanum, and nickel through elemental diffusion, the charge of the entire piezoelectric layer tends to decrease. Therefore, in order to increase the charge and maintain electroneutrality, the lead vacancies contained in the piezoelectric layer will decrease. Furthermore, when lead in the piezoelectric layer is replaced by a metal element with a higher valence state than lead, such as lanthanum, through elemental diffusion, the number of oxygen vacancies in the piezoelectric layer is reduced to decrease the overall charge of the piezoelectric layer and maintain electroneutrality. As a result, by including a process of forming an adjustment layer containing strontium and ruthenium as specified metals, or containing lanthanum and nickel as specified metals, the crystallinity of the piezoelectric layer can be further improved, and vacancies can be reduced through elemental diffusion, thus further improving the voltage withstand performance.

[0015] In the method for manufacturing a piezoelectric film substrate according to the first aspect above, preferably, the step of forming a piezoelectric layer includes the following steps: while a substrate placed in a film-forming chamber is heated by a heating device at a predetermined film-forming temperature, a piezoelectric layer is formed on an adjustment layer, and the step of holding the substrate for a predetermined period includes the following steps: following the step of forming the piezoelectric layer, the substrate is held for a predetermined period while the substrate placed in the film-forming chamber is kept heated by a heating device at a predetermined film-forming temperature. If configured in this way, the substrate, which is heated by a heating device at a predetermined film-forming temperature, is directly held in the film-forming chamber where the piezoelectric layer is formed, thereby improving the voltage withstand performance of the piezoelectric layer. Therefore, compared to the case where a film-forming device and a heating device are separately provided, the complexity of the device structure caused by improving the voltage withstand performance of the piezoelectric layer can be suppressed. Furthermore, when the substrate is heated to a temperature higher than that used during film formation using an apparatus different from the apparatus used for forming the piezoelectric layer, the substrate needs to be transferred to an apparatus with higher heat resistance. Moreover, if a separate apparatus is provided for heating after film formation, the substrate must be cooled and reheated for transport, thus increasing processing time. In contrast, by continuously performing a process of maintaining the substrate at a predetermined film formation temperature within the film formation chamber after the piezoelectric layer formation process, voltage withstand performance can be effectively improved with a good yield. For example, when sputtering to form a piezoelectric layer while the substrate is heated to a predetermined film formation temperature using a heating apparatus, the process of maintaining the substrate at the predetermined film formation temperature can be performed directly simply by switching off the generation of sputtering plasma. Furthermore, heating the substrate to a temperature higher than that used during film formation within the film formation chamber increases the thermal burden on the apparatus used for forming the piezoelectric layer, including the film formation chamber. When the substrate is heated to a temperature higher than that required for film formation within the film-forming chamber, the performance of the apparatus, including the film-forming chamber, needs to be improved to a level exceeding the performance required for film formation because heat resistance is required for film formation above the specified film-forming temperature for piezoelectric layer formation. Furthermore, in a film-forming chamber where a piezoelectric layer has already been formed, if the substrate is heated to a temperature higher than the film-forming temperature (i.e., the set film-forming temperature) to improve crystallinity, it is believed that particles may be generated due to the peeling of the piezoelectric layer material attached to the inner wall of the film-forming chamber. Moreover, even with a high heat resistance in the film-forming apparatus, repeated heating and cooling place a greater burden on the components constituting the apparatus, thus shortening its lifespan.In contrast, in this invention, since the substrate is kept heated at the set temperature during film formation (i.e., the set temperature during film formation) for a specified period of time, it is possible to suppress the generation of particles that cause a decrease in the performance of the generated piezoelectric film substrate, and to suppress the increase in the burden (load) on the device, including the film formation chamber used for forming the piezoelectric layer.

[0016] Preferably, the process of forming a piezoelectric layer includes the following steps: while the substrate is heated by a heating device at a predetermined film-forming temperature, a piezoelectric layer is formed on an adjustment layer by sputtering, wherein the sputtering utilizes sputtered particles from a lead-containing target disposed in the film-forming chamber. The process of holding the substrate for a predetermined period includes the following steps: following the process of forming the piezoelectric layer by sputtering, the substrate, placed in a film-forming chamber containing a lead atmosphere, is kept heated by a heating device at a predetermined film-forming temperature for a predetermined period and held for a predetermined period. If configured in this way, the substrate heated at the film-forming temperature during sputtering is directly kept heated at the film-forming temperature after sputtering is completed, thereby easily improving the voltage withstand performance of the piezoelectric layer. Furthermore, in the film-forming of the piezoelectric layer by sputtering, the film-forming chamber is in a lead atmosphere, which is filled with at least one of lead molecules and lead-containing compound molecules of lead zirconate titanate material, which is the piezoelectric layer. Therefore, by maintaining a substrate heated to a set temperature during film formation within a lead-atmosphere chamber for a specified period, lead detachment from the piezoelectric layer during heating can be suppressed, and lead can be supplied to the piezoelectric layer. This suppresses the increase of lead vacancies and oxygen vacancies caused by lead defects in the piezoelectric layer, thereby further improving the crystallinity of the piezoelectric layer. Consequently, after sputtering, by maintaining a heated substrate in the lead-atmosphere chamber after sputtering, the voltage withstand capability of the piezoelectric layer can be further improved.

[0017] In the method for manufacturing a piezoelectric film substrate according to the first aspect described above, preferably, the step of holding the substrate for a predetermined period includes the following step: holding the substrate for a predetermined period of 5 minutes or more and less than 60 minutes while it is heated at a predetermined film-forming temperature. Here, if the holding period of the substrate heated at the predetermined film-forming temperature is too short, element diffusion from the adjustment layer is unlikely to occur, thus the improvement in the voltage withstand performance of the piezoelectric layer is insufficient. Furthermore, if the holding period of the substrate heated at the predetermined film-forming temperature is too long, more elemental substitution due to element diffusion from the adjustment layer occurs, thus deteriorating the characteristics of the piezoelectric layer. In contrast, in this invention, since the substrate is held for a predetermined period of 5 minutes or more and less than 60 minutes while it is heated at the predetermined film-forming temperature, an appropriate length of time can be achieved. Therefore, compared to cases where the holding period is too short or too long, the voltage withstand performance of the piezoelectric layer can be further improved.

[0018] To achieve the above objectives, a piezoelectric film substrate according to a second aspect of the present invention comprises: a lower electrode layer and an upper electrode layer formed on a substrate; an adjustment layer formed between the lower electrode layer and the upper electrode layer and containing a predetermined metal element; and a piezoelectric layer formed on the adjustment layer while heated at a predetermined film-forming temperature and containing lead zirconate titanate having a perovskite structure, the piezoelectric layer including a diffusion layer formed along the interface with the adjustment layer on the side of the lower electrode layer, the diffusion layer having a thickness of 10% or less of the overall film thickness of the piezoelectric layer; by continuously maintaining the state at a predetermined film-forming temperature for a predetermined period after the formation of the piezoelectric layer, at least one of titanium, zirconium, and lead contained in the piezoelectric layer is replaced by the predetermined metal element contained in the adjustment layer through element diffusion; and the diffusion layer has a region in which the detection intensity of the predetermined metal element contained in the diffusion layer is 10% or more higher than that of the portion of the piezoelectric layer outside the diffusion layer.

[0019] As described above, in the piezoelectric film substrate according to the second aspect of the present invention, the piezoelectric layer includes a diffusion layer formed along the interface with the adjustment layer. The diffusion layer is held for a predetermined period while being heated at a predetermined film-forming temperature after the formation of the piezoelectric layer, thereby allowing at least one of titanium, zirconium, and lead contained in the piezoelectric layer to be replaced by a predetermined metal element contained in the adjustment layer through elemental diffusion. Therefore, unlike the case where the substrate is held at a temperature higher than the film-forming temperature during the formation of the piezoelectric layer, the effects of heating, such as an increase in film stress, can be suppressed in the piezoelectric layer after film formation on the substrate. Furthermore, since the titanium, zirconium, and lead contained in the piezoelectric layer are replaced by metal elements with different valence states, lattice defects such as oxygen vacancies and lead vacancies contained in the piezoelectric layer can be reduced, thus improving the voltage withstand performance of the piezoelectric layer. Moreover, when the substrate is held at a temperature lower than the predetermined film-forming temperature during the formation of the piezoelectric layer, elemental diffusion from the adjustment layer is less likely to occur, resulting in insufficient improvement in the voltage withstand performance of the piezoelectric layer. In contrast, in this invention, since the substrate is heated at a predetermined film-forming temperature during the formation of the piezoelectric layer and then held for a predetermined period, insufficient improvement in voltage withstand performance can be suppressed. As a result, a piezoelectric film substrate that can suppress the increase in the effects of heating and improve voltage withstand performance can be provided.

[0020] Invention Effects

[0021] As described above, according to the present invention, the effects of heating, such as the increase in membrane stress, can be suppressed, and the voltage withstand performance can be improved. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view showing one embodiment of a piezoelectric film substrate.

[0023] Figure 2 This is a schematic diagram illustrating the perovskite structure of lead zirconate titanate with a piezoelectric layer.

[0024] Figure 3 This is a diagram used to illustrate the diffusion layer contained in the piezoelectric layer.

[0025] Figure 4 This is a diagram schematically illustrating the structure of a sputtering device.

[0026] Figure 5 This is a flowchart illustrating a method for manufacturing a piezoelectric film substrate according to one embodiment. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0028] (Structure of piezoelectric film substrate)

[0029] refer to Figures 1 to 4 The structure of a piezoelectric film substrate 100 according to one embodiment of the present invention will be described.

[0030] The piezoelectric film substrate 100 is a piezoelectric film substrate divided into multiple monoliths, each of which becomes a device. Each of the multiple monoliths becomes a device. The device is, for example, a MEMS (Micro Electro Mechanical Systems) device. Furthermore, the MEMS device is used, for example, as a sensor or actuator.

[0031] like Figure 1 As shown, 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 arranged and sequentially stacked on the substrate 1. In the piezoelectric film substrate 100, a lower electrode with a multilayer film is formed below the piezoelectric layer 5 by the insulating layer 2, the lower electrode layer 3, and the lower adjustment layer 4. Furthermore, in the piezoelectric film substrate 100, an upper electrode with a multilayer film is formed above the piezoelectric layer 5 by the upper adjustment layer 6 and the upper electrode layer 7. The lower adjustment layer 4 is an example of the "adjustment layer" as described in the claims.

[0032] Substrate 1 is a silicon substrate. Insulating layer 2 is a thin film of an insulator formed on substrate 1. Insulating layer 2 is formed, for example, of silicon dioxide (SiO2). Insulating layer 2 can be formed of materials such as zirconium oxide (ZrO2) or yttrium-stabilized zirconium oxide (YSZ). For example, insulating layer 2 includes a silicon oxide layer formed on the surface of substrate 1 by thermal oxidation of substrate 1, which is a silicon substrate. Substrate 1 has, for example, a thickness of about 300 μm or more and about 725 μm or less. Insulating layer 2 has, for example, a thickness of about 100 nm or more and about 500 nm or less.

[0033] On substrate 1, a lower electrode layer 3 is formed on insulating layer 2. Specifically, the lower electrode layer 3 is formed as a single crystal by epitaxial growth. The lower electrode layer 3 is formed of materials such as platinum (Pt) or iridium (Ir). The lower electrode layer 3 has a thickness of approximately 50 nm or more and approximately 200 nm or less.

[0034] A lower adjustment layer 4 is formed on the lower electrode layer 3 on the substrate 1. The lower adjustment layer 4 contains a specified metal element. The lower adjustment layer 4 contains a metal oxide. The lower adjustment layer 4 contains strontium (Sr) and ruthenium (Ru) as specified metal elements, or lanthanum (La) and nickel (Ni) as specified metal elements. The lower adjustment layer 4 is formed of materials 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 has been crystallized. The lower adjustment layer 4 functions as a seed layer (seed crystal layer) for making the crystal orientation of the piezoelectric layer 5 the desired orientation. Furthermore, the lower adjustment layer 4 has, for example, a thickness of about 2 nm or more and about 40 nm or less.

[0035] On the substrate 1, a piezoelectric layer 5 is formed on the lower conditioning layer 4. Furthermore, the piezoelectric layer 5 contains lead zirconate titanate (PZT), which exhibits ferroelectric properties. The piezoelectric layer 5 is formed from polycrystalline lead zirconate titanate. The piezoelectric layer 5 has, for example, a thickness of about 0.75 μm or more and about 5 μm or less.

[0036] like Figure 2 As shown, piezoelectric layer 5 contains lead zirconate titanate with a perovskite structure. In the perovskite structure, the metal elements are located at the A-sites, which are the vertices of the cubic lattice, and the B-sites, which are the body center, respectively, and oxygen (O) is located at the face center of each face centered at 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.

[0037] like Figure 1 As shown, an upper conditioning layer 6 is formed on a piezoelectric layer 5 on a substrate 1. The upper conditioning layer 6 contains a metal element common to or different from that of the lower conditioning layer 4. That is, the upper conditioning layer 6 contains a metal oxide. The upper conditioning layer 6 contains strontium (Sr) and ruthenium (Ru), or lanthanum (La) and nickel (Ni). The upper conditioning layer 6 is formed from materials such as strontium ruthenate (SrRuO3:SRO) containing strontium and ruthenium, or lanthanum nickelate (LaNiO3:LNO) containing lanthanum and nickel. For example, the upper conditioning layer 6 contains a metal element common to the specified metal element contained in the lower conditioning layer 4, and is a thin film with the same composition as the lower conditioning layer 4. As an example, the lower conditioning layer 4 and the upper conditioning layer 6 contain a common combination of metal elements, formed from strontium ruthenate (SrRuO3:SRO). The upper adjustment layer 6 functions as a barrier layer, inhibiting the migration (diffusion) of elements such as oxygen or lead in the piezoelectric layer 5 towards the upper electrode layer 7. The upper adjustment layer 6 can be crystalline or amorphous. For example, the upper adjustment layer 6 is formed with a thickness of about 2 nm or more and about 40 nm or less.

[0038] On substrate 1, an upper electrode layer 7 is formed on an upper adjustment layer 6. The upper electrode layer 7 is formed of materials such as titanium (Ti), gold (Au), platinum (Pt), or iridium dioxide (IrO2). The upper electrode layer 7 has, for example, a thickness of approximately 50 nm or more and approximately 500 nm or less. The upper electrode layer 7 can be formed of the same material as the lower electrode layer 3, or it can be formed of a different material. Furthermore, the materials of each layer of the upper adjustment layer 6 and the upper electrode layer 7 are not particularly limited. Moreover, the upper electrode can be a single-layer electrode; that is, the upper adjustment layer 6 may not be provided. Furthermore, an insulating layer such as a silicon oxide layer may be formed on the upper electrode layer 7.

[0039] In the piezoelectric film substrate 100 of this embodiment, after the piezoelectric layer 5 is formed on the lower adjustment layer 4, the substrate 1 with the piezoelectric layer 5 is directly kept in a heated state at the set temperature during film formation (i.e., the set temperature during film formation) to perform an annealing process that reduces lattice defects in the piezoelectric layer 5. During the annealing process, titanium, zirconium, and lead contained in the piezoelectric layer 5 are replaced by metal elements (strontium and ruthenium or lanthanum and nickel) contained in the lower adjustment layer 4 through element diffusion caused by heat. This elemental diffusion replacement occurs in the portion of the piezoelectric layer 5 along the interface between it and the lower adjustment layer 4. Furthermore, since the annealing process is performed before the formation of the upper adjustment layer 6 and the upper electrode layer 7, the replacement of elements in the piezoelectric layer 5 by metal elements contained in the upper adjustment layer 6 does not occur at the interface between the piezoelectric layer 5 and the upper adjustment layer 6.

[0040] like Figure 3 As shown, in the piezoelectric film substrate 100, the piezoelectric layer 5 includes a diffusion layer 5a. This diffusion layer 5a is continuously heated at a predetermined temperature during film formation and maintained for a predetermined period after the formation of the piezoelectric layer 5, thereby allowing at least one of titanium, zirconium, and lead contained in the piezoelectric layer 5 on the lower electrode layer 3 side to be replaced by a predetermined metal element (strontium and ruthenium or lanthanum and nickel) contained in the lower adjustment layer 4 through elemental diffusion. The diffusion layer 5a is formed along the lower interface with the lower adjustment layer 4 on the lower side of the upper and lower sides of the piezoelectric layer 5. The diffusion layer 5a has a region in which the detection intensity of the predetermined metal element (strontium and ruthenium or lanthanum and nickel) contained in the diffusion layer 5a is at least 10% higher than that of the portion of the piezoelectric layer 5 outside the diffusion layer 5a. The detection intensity of the predetermined metal element (strontium and ruthenium or lanthanum and nickel) is detected, for example, by SIMS (secondary ion mass spectrometry).

[0041] <Sputtering device>

[0042] like Figure 4As shown, in this embodiment, the piezoelectric layer 5 is formed by sputtering using a sputtering apparatus 101. The sputtering apparatus 101 is configured to sputter target particles (sputtered particles) from a target component 102 containing titanium (Ti), zirconium (Zr), and lead (Pb), which serve as the piezoelectric layer 5, and attach the sputtered particles to a substrate 1, thereby forming a thin film from the sputtered particles from the target component 102 on the substrate 1 (piezoelectric film substrate 100). The sputtering apparatus 101 includes a stage 11, a heating device 12, a film-forming chamber 13, and a vacuum pump 14.

[0043] The sputtering apparatus 101 introduces gases such as argon (Ar) and oxygen (O2) into the film-forming chamber 13, which has been evacuated by the vacuum pump 14. Then, the sputtering apparatus 101 applies a voltage to the target component 102 disposed within the film-forming chamber 13 to generate plasma within the chamber. Charged particles (e.g., argon ions) in this plasma collide with the target component 102, thereby releasing (ejecting) sputtered particles containing titanium (Ti), zirconium (Zr), and lead (Pb) from the target component 102. The released sputtered particles then adhere to the substrate 1 (piezoelectric film substrate 100) placed on the stage 11, thereby forming a thin film, i.e., a piezoelectric film layer 5, on the surface of the substrate 1.

[0044] In the sputtering apparatus 101, the heating device 12 is configured to heat the substrate 1 placed on the stage 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 disposed. The heating device 12 includes, for example, heating wires. In the sputtering apparatus 101, the substrate 1, placed in the film deposition chamber 13 and heated at a predetermined set temperature (i.e., the film deposition set temperature), is sputtered. The heating device 12 is controlled to maintain the substrate 1 at the predetermined film deposition set temperature during sputtering. That is, during film deposition by sputtering, the output of the heating device 12 is controlled to keep the substrate 1 at a predetermined constant film deposition set temperature. For example, when a 2 μm piezoelectric layer 5 is deposited, film deposition is performed by sputtering for approximately 20 minutes.

[0045] Furthermore, the sputtering apparatus 101 includes a control device 15. The control device 15 controls various parts 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 flash memory. The control device 15 controls the sputtering performed by the sputtering apparatus 101 according to the program and parameters stored in the storage device. Specifically, the control device 15 controls the application of voltage to the target component 102, the operation of the vacuum pump 14, and the operation of the heating device 12.

[0046] (Manufacturing method of piezoelectric film substrate)

[0047] Next, refer to Figure 5 The manufacturing method of the piezoelectric film substrate 100 will be described. The manufacturing method of the piezoelectric film substrate 100 is a method for manufacturing a piezoelectric film substrate that is divided into multiple single pieces that each become a device.

[0048] like Figure 5 As shown, the manufacturing method of the piezoelectric film substrate 100 includes: step S1 as a process of preparing substrate 1, step S2 as a process of forming insulating layer 2, step S3 as a process of forming lower electrode layer 3 on substrate 1, step S4 as a process of forming lower adjustment layer 4, step S5 as a process of forming piezoelectric layer 5 on lower adjustment layer 4, step S6 as a process of holding piezoelectric film substrate 100 for a predetermined period, step S7 as a process of forming upper adjustment layer 6 on piezoelectric layer 5, and step S8 as a process of forming upper electrode layer 7 on substrate 1. In the manufacturing method of piezoelectric film substrate 100 of this embodiment, steps S1 to S8 are performed sequentially. Except where specifically described, each step from S1 to S8 may be performed discontinuously.

[0049] First, in step S1, during the process of preparing substrate 1, substrate 1, which serves as a silicon substrate, is prepared. Then, in step S2, during the process of forming insulating layer 2, the silicon (Si) substrate constituting substrate 1 is thermally oxidized at a temperature of approximately 700°C, thereby forming insulating layer 2, which is a silicon oxide layer composed of SiO2, on the surface of substrate 1.

[0050] Next, in step S3, during the process of forming the lower electrode layer 3 on the substrate 1, the lower electrode layer 3 is formed by sputtering in a manner that it is stacked on the insulating layer 2 on the substrate 1. Then, in step S4, during the process of forming the lower adjustment layer 4, after forming the lower electrode layer 3, the lower adjustment layer 4 is formed on the lower electrode layer 3 on the substrate 1 by sputtering. In the process of forming the lower adjustment layer 4, for example, the substrate 1 is heated to about 500°C. As a result, the metal oxide of the lower adjustment layer 4 is crystallized. In addition, the lower electrode layer 3 and the lower adjustment layer 4 can be formed using a common sputtering apparatus or using different sputtering apparatuses.

[0051] Then, in step S5, during the process of forming a piezoelectric layer 5 on the lower adjustment layer 4, the piezoelectric layer 5 is formed on the lower adjustment layer 4 formed on the substrate 1 by sputtering while the layer is heated at a predetermined temperature during film formation. Furthermore, the sputtering of the piezoelectric layer 5 is performed using a sputtering apparatus 101, which is different from the sputtering apparatus used to form the lower electrode layer 3 and the lower adjustment layer 4.

[0052] In this embodiment, during the process of forming a piezoelectric layer 5 on the lower adjustment layer 4, the piezoelectric layer 5 is formed by sputtering particles from the target component 102 while the substrate 1 (piezoelectric film substrate 100) placed in the film formation chamber 13 of the sputtering apparatus 101 is heated at a predetermined film formation temperature by the heating device 12. Sputtering is performed while the film formation chamber 13 is evacuated by the vacuum pump 14. Here, "vacuum" refers to a pressure below atmospheric pressure. In the sputtering apparatus 101, the control device 15 heats the substrate 1 on which the lower adjustment layer 4 is formed at a predetermined film formation temperature by the heating device 12. Then, the control device 15 begins sputtering for forming the piezoelectric layer 5 on the substrate 1, which is heated at the predetermined film formation temperature. The control device 15 performs sputtering by applying a voltage to the target component 102 for a predetermined period until the piezoelectric layer 5 is formed to a predetermined thickness. During the formation of the piezoelectric layer 5 by sputtering, the control device 15 controls the operation of the heating device 12 to maintain the substrate 1 at a predetermined film formation temperature. Then, after a predetermined period (e.g., 20 minutes), sputtering is stopped. The predetermined film formation temperature is approximately 560°C or higher and approximately 700°C or lower. For example, the predetermined film formation temperature is approximately 600°C. Furthermore, the predetermined film formation temperature mentioned here refers to the temperature of the substrate 1 set as the heating target of the heating device 12. That is, the predetermined film formation temperature does not include temperature changes of the substrate 1 caused by factors other than the heating device 12, and the actual temperature of the substrate 1 may differ from the predetermined film formation temperature set as the target, depending on factors such as the presence or absence of plasma during sputtering. Furthermore, if the sputtering apparatus 101 is equipped with a display unit that displays the temperature of the substrate 1, the temperature displayed on the display unit may sometimes differ from the actual temperature of the substrate 1. The "specified film-forming temperature" is a target temperature that does not include temperature variations in the substrate 1 caused by factors other than the heating device. An error may occur between the specified film-forming temperature and the actual temperature of the substrate 1 due to factors outside the heating device. The substrate 1 is heated to crystallize lead zirconate titanate having a perovskite structure.

[0053] Then, in step S6, during the process of holding the substrate 1 (piezoelectric film substrate 100) for a predetermined period, following the process of sputtering to form the piezoelectric layer 5 (step S5), the substrate 1 (piezoelectric film substrate 100) with the piezoelectric layer 5 is held for a predetermined period while heated at a predetermined film-forming temperature during the sputtering process. That is, after forming the piezoelectric layer 5 in step S5, the substrate 1 before forming the upper adjustment layer 6 and the upper electrode layer 7 is continuously subjected to an annealing process, which is the process of holding the substrate 1 for a predetermined period in step S6. In addition, in step S6, the substrate 1 placed in the film-forming chamber 13, which is in a lead atmosphere, is held for a predetermined period. During the process of holding the substrate 1 in the film-forming chamber 13 in step S6, the film-forming chamber 13 is kept in a vacuum state by the vacuum pump 14, just as it was during film formation. Therefore, the film-forming chamber 13 is in a lead atmosphere, filled with lead-containing molecules that diffuse as sputtering particles. In the sputtering apparatus 101, after the piezoelectric layer 5 is formed, the heating device 12 is controlled by the control device 15 to continue performing the same operation as during the formation of the piezoelectric layer 5, thereby continuously heating the substrate 1 at a predetermined film-forming temperature. That is, in steps S5 and S6, the heating device 12 is controlled so that the substrate 1 is heated at the same predetermined film-forming temperature. Through the post-film-forming annealing process in step S6, the predetermined period during which the substrate 1 is kept heated at the predetermined film-forming temperature is 5 minutes or more and less than 60 minutes, preferably 20 minutes or more and less than 40 minutes, and more preferably 30 minutes.

[0054] In this embodiment, the annealing process in step S6 reduces lattice defects such as oxygen vacancies and lead vacancies in the piezoelectric layer 5. Through the annealing process after film formation of the piezoelectric layer 5, the metal elements contained in the lower adjustment layer 4 below the piezoelectric layer 5 diffuse into the piezoelectric layer 5 via element diffusion. Through this element diffusion, the titanium (Ti), zirconium (Zr), and lead (Pb) in the lead zirconate titanate of the piezoelectric layer 5 are replaced by strontium and ruthenium (Sr and Ru) or lanthanum and nickel (La and Ni) in the lower adjustment layer 4. For example, when the lower adjustment layer 4 is formed as lanthanum nickelate (LaNiO3), the titanium (Ti) or zirconium (Zr) disposed at the B site of the piezoelectric layer 5 is replaced by lanthanum (La) or nickel (Ni) in the lower adjustment layer 4. When titanium (Ti) or zirconium (Zr) with a valence state of 4+ is replaced by lanthanum (La) or nickel (Ni) with a valence state of 2+ or 3+, the lead vacancies, which are considered anions, are reduced to maintain electroneutrality. Furthermore, when lead (Pb) with a valence state of 2+ at the A-site of the piezoelectric layer 5 is replaced by lanthanum (La) with a valence state of 3+, the oxygen vacancies, which are considered cations, are reduced to maintain electroneutrality. Thus, by replacing titanium, zirconium, and lead in the piezoelectric layer 5 with metal elements of different valence states, lattice defects such as oxygen and lead vacancies in the piezoelectric layer 5 are reduced.

[0055] Then, in step S7, during the process of forming the upper adjustment layer 6 on the piezoelectric layer 5, the upper adjustment layer 6 is formed by sputtering in a manner that it is stacked on the piezoelectric layer 5 on the substrate 1. Furthermore, in step S8, during the process of forming the upper electrode layer 7 on the substrate 1, after forming the upper adjustment layer 6, the upper electrode layer 7 is formed on the upper adjustment layer 6 on the substrate 1 by sputtering. For example, the processes of forming the upper adjustment layer 6 and the upper electrode layer 7 are performed without heating the substrate 1 (piezoelectric film substrate 100). Furthermore, the upper adjustment layer 6 and the upper electrode layer 7 can be formed using a common sputtering apparatus or using different sputtering apparatuses. Through the processes of steps S1 to S8, the piezoelectric film substrate 100 can be manufactured.

[0056] Subsequently, in the process of shaping the substrate into a device shape, for example, photolithography is used to shape the lower electrode (lower electrode layer 3 and lower adjustment layer 4), piezoelectric layer 5, and upper electrode (upper adjustment layer 6 and upper electrode layer 7) into a device shape. In the case of photolithography, unwanted portions are removed and desired portions are left by wet etching with an etching solution or dry etching with an etching gas, thereby shaping the piezoelectric film substrate 100 into a device shape. Furthermore, when the piezoelectric film substrate 100 is divided into device wafers, for example, a blade is used to cut the piezoelectric film substrate 100 into device wafers.

[0057] (Effects of this implementation method)

[0058] In this embodiment, the following effects can be achieved.

[0059] As described above, in this embodiment, the method for manufacturing the piezoelectric film substrate 100 includes: a step of forming a piezoelectric layer 5 while heated at a predetermined film-forming temperature (step S5); and then, a step of holding the substrate 1 for a predetermined period while heated at the predetermined film-forming temperature (step S6). Therefore, unlike the case where the substrate 1 is held at a temperature higher than the predetermined film-forming temperature for forming the piezoelectric layer 5, the effects of heating, such as an increase in film stress, can be suppressed more effectively in the piezoelectric layer 5 formed on the substrate 1. Furthermore, as described above, the manufacturing method of the piezoelectric film substrate 100 of this embodiment includes a step (step S5) of forming a piezoelectric layer 5 on a lower adjustment layer 4 (adjustment layer) containing a specified metal element. Therefore, by holding the substrate 1 on which the piezoelectric layer 5 is formed on the lower adjustment layer 4 in a state of being heated at a specified film-forming temperature, the titanium, zirconium, and lead elements contained in the piezoelectric layer 5 can be replaced by the metal elements contained in the lower adjustment layer 4 through element diffusion. Therefore, by replacing the titanium, zirconium, and lead contained in the piezoelectric layer 5 with metal elements of different valence states, the lattice defects such as oxygen vacancies and lead vacancies contained in the piezoelectric layer 5 can be reduced, thereby improving the voltage withstand performance of the piezoelectric layer 5. Furthermore, when the substrate 1 is held at a temperature lower than the film-forming temperature during the formation of the piezoelectric layer 5, element diffusion from the lower adjustment layer 4 is not easily generated, and therefore the improvement in the voltage withstand performance of the piezoelectric layer 5 is insufficient. In contrast, in this embodiment, since the substrate 1 is heated at a predetermined film-forming temperature during the formation of the piezoelectric layer 5, and the substrate 1 is held for a predetermined period of time, insufficient improvement in voltage withstand performance can be suppressed. As a result, the increased effects caused by heating can be suppressed, and voltage withstand performance can be improved.

[0060] As described above, in this embodiment, the manufacturing method of the piezoelectric film substrate 100 includes the following steps (step S4): forming a lower adjustment layer 4 (adjustment layer), which contains strontium and ruthenium as specified metals, or contains lanthanum and nickel as specified metals, and is used to adjust the crystal orientation of the piezoelectric layer 5. Therefore, by forming a film of the piezoelectric layer 5 on the lower adjustment layer 4, the crystal orientation of the piezoelectric layer 5 can be adjusted, thus further improving the crystallinity of the piezoelectric layer 5. Furthermore, compared to titanium and zirconium contained in lead zirconate titanate of the piezoelectric layer 5, strontium, ruthenium, lanthanum, and nickel are all more likely to become cations with lower valence states. Therefore, when titanium and zirconium in the piezoelectric layer 5 are replaced by any one of strontium, ruthenium, lanthanum, and nickel through elemental diffusion, the charge of the entire piezoelectric layer 5 tends to decrease. Therefore, in order to increase the charge and maintain electroneutrality, the lead vacancies contained in the piezoelectric layer 5 will decrease. Furthermore, when lead in the piezoelectric layer 5 is replaced by a metal element with a higher valence state than lead, such as lanthanum, through elemental diffusion, the number of oxygen vacancies in the piezoelectric layer 5 is reduced to decrease the overall charge of the piezoelectric layer 5 and maintain electroneutrality. As a result, by including the process of forming a lower adjustment layer 4 containing strontium and ruthenium as specified metals, or containing lanthanum and nickel as specified metals (step S4), the crystallinity of the piezoelectric layer 5 can be further improved, and vacancies can be reduced through elemental diffusion, thereby further improving the voltage withstand performance.

[0061] As described above, in this embodiment, the manufacturing method of the piezoelectric film substrate 100 includes the following steps (step S5): while the substrate 1 placed in the film-forming chamber 13 is heated by the heating device 12 at a predetermined film-forming temperature, a piezoelectric layer 5 is formed on the lower adjustment layer 4 (adjustment layer). The manufacturing method of the piezoelectric film substrate 100 includes the following steps (step S6): following the step of forming the piezoelectric layer 5 (step S5), the substrate 1 placed in the film-forming chamber 13 is held for a predetermined period while being heated by the heating device 12 at a predetermined film-forming temperature. Therefore, in the film-forming chamber 13 where the piezoelectric layer 5 is formed while the substrate 1 is heated by the heating device 12 at the temperature set during film formation, the substrate 1, which is heated by the heating device 12 at the temperature set during film formation, is directly kept in this state. This improves the voltage withstand performance of the piezoelectric layer 5. Therefore, compared to the case where a film-forming device and a device for heating after film formation are provided separately, the complexity of the device structure caused by improving the voltage withstand performance of the piezoelectric layer 5 can be suppressed. Furthermore, if the substrate 1 is heated to a temperature higher than the temperature during film formation by a device different from the device for forming the piezoelectric layer 5 (sputtering device 101), the substrate 1 needs to be transferred to a device with higher heat resistance. Moreover, if a device for heating after film formation is provided separately, the substrate 1 must be cooled and reheated for transport operations, thus increasing the operation time. In contrast, by continuously maintaining the substrate 1 in a state heated to the temperature set during film formation within the film formation chamber 13 after the process of forming the piezoelectric layer 5 (step S5) (step S6), the voltage withstand performance can be effectively improved with a good yield. For example, when the piezoelectric layer 5 is formed by sputtering while the substrate 1 is heated to the predetermined temperature set during film formation by the heating device 12, the process of maintaining the substrate 1 in a state heated to the temperature set during film formation (step S6) can be performed directly simply by switching off the generation of sputtered plasma. Furthermore, if the substrate 1 is heated to a temperature higher than that during film formation within the film formation chamber 13, the heat load on the apparatus (sputtering apparatus 101) used for forming the piezoelectric layer 5, including the film formation chamber 13, will increase. When the substrate 1 is heated to a temperature higher than that used for film formation within the film-forming chamber 13, it is necessary to improve the performance of the apparatus including the film-forming chamber 13 to exceed the performance required for film formation, as heat resistance is required for film formation above the set temperature during film formation of the piezoelectric layer 5. Furthermore, in the film-forming chamber 13 where the piezoelectric layer 5 has been formed, if the substrate 1 is heated to a temperature higher than the heating temperature used for film formation (i.e., the set temperature during film formation) to improve crystallinity, it is believed that particles may be generated due to the peeling off of the material of the piezoelectric layer 5 attached to the inner wall of the film-forming chamber 13.Furthermore, even when the apparatus for film formation has high heat resistance, repeated heating and cooling place a greater burden on the components constituting the apparatus, thus shortening its lifespan. In contrast, in this embodiment, since the substrate 1 is kept heated at the set temperature during film formation (i.e., the set temperature during film formation) for a specified period, the generation of particles that cause a decline in the performance of the generated piezoelectric film substrate 100 can be suppressed, and the increase in the burden (load) on the apparatus, including the film formation chamber 13 used for forming the piezoelectric layer 5, can be suppressed.

[0062] In this embodiment, as described above, the manufacturing method of the piezoelectric film substrate 100 includes the following steps (step S5): while the substrate 1 is heated by the heating device 12 at a predetermined film-forming temperature, a piezoelectric layer 5 is formed on the lower adjustment layer 4 (adjustment layer) by sputtering using sputtering particles from a lead-containing target member 102 disposed in the film-forming chamber 13. The manufacturing method of the piezoelectric film substrate 100 includes the following steps (step S6): following the step of sputtering to form the piezoelectric layer 5 (step S5), the substrate 1, placed in the film-forming chamber 13 which is internally in a lead atmosphere, is heated by the heating device 12 at a predetermined film-forming temperature for a predetermined period of time. Therefore, the substrate 1, heated at the film-forming temperature during sputtering, is directly kept heated at the film-forming temperature after sputtering is completed, thereby easily improving the voltage withstand performance of the piezoelectric layer 5. Furthermore, during the sputtering of the piezoelectric layer 5, the film-forming chamber 13 is filled with a lead atmosphere, which is filled with at least one of lead molecules and lead-containing compound molecules, which are lead zirconate titanate materials used as the piezoelectric layer 5. Therefore, by maintaining the substrate 1, which is heated to a temperature set during film formation, within the film-forming chamber 13, a lead atmosphere is present, for a predetermined period, it is possible to suppress lead detachment from the piezoelectric layer 5 during heating and to supply lead to the piezoelectric layer 5. Thus, the increase in lead vacancies and oxygen vacancies caused by lead defects in the piezoelectric layer 5 can be suppressed, thereby further improving the crystallinity of the piezoelectric layer 5. Consequently, after sputtering is completed, by maintaining the heated substrate 1 within the sputtered film-forming chamber 13, which is in a lead atmosphere, the voltage withstand performance of the piezoelectric layer 5 can be further improved.

[0063] As described above, in this embodiment, the manufacturing method of the piezoelectric film substrate 100 includes the following step (step S6): holding the substrate 1 for a predetermined period of 5 minutes to 60 minutes while it is heated at a predetermined film-forming temperature. If the holding period of the substrate 1 at the predetermined film-forming temperature is too short, element diffusion from the lower adjustment layer 4 (adjustment layer) is difficult to occur, resulting in insufficient improvement in the voltage withstand performance of the piezoelectric layer 5. Furthermore, if the holding period of the substrate 1 at the predetermined film-forming temperature is too long, elemental substitution due to element diffusion from the lower adjustment layer 4 occurs more frequently, thus deteriorating the characteristics of the piezoelectric layer 5. In contrast, in this embodiment, since the substrate 1 is held for a predetermined period of 5 minutes to 60 minutes while it is heated at the predetermined film-forming temperature, an appropriate length of time can be achieved. Therefore, compared with cases where the holding period is too short or too long, the voltage withstand performance of the piezoelectric layer 5 can be further improved.

[0064] (Variation example)

[0065] Furthermore, it should be considered that the embodiments disclosed herein are merely exemplary in all respects and not restrictive. The scope of the invention is not defined by the description of the above embodiments, but by the claims, and also includes all modifications (variations) that are equivalent in meaning and scope to the claims.

[0066] For example, in the above embodiments, an example is shown where the lower adjustment layer 4 (adjustment layer) contains strontium and ruthenium as specified metals, or contains lanthanum and nickel as specified metals, but the present invention is not limited thereto. In the present invention, the adjustment layer may also be configured to contain metal elements different from strontium, ruthenium, lanthanum, and nickel. Furthermore, the adjustment layer may not have the function of adjusting the crystal orientation of the piezoelectric layer. Furthermore, the adjustment layer may be a multilayer film.

[0067] Furthermore, in the above embodiments, examples are shown of the lower electrode layer 3, lower adjustment layer 4 (adjustment layer), piezoelectric layer 5, upper adjustment layer 6, and upper electrode layer 7 being formed by sputtering, but the present invention is not limited thereto. In the present invention, any one of the lower electrode layer 3, lower adjustment layer 4 (adjustment layer), piezoelectric layer 5, upper adjustment layer 6, and upper electrode layer 7 can be formed by methods other than sputtering. For example, the lower electrode layer or the upper electrode layer can also be formed by vacuum deposition. Furthermore, the piezoelectric layer can also be formed by PLD (pulsed laser deposition), CVD (chemical vapor deposition), or sol-gel method. Furthermore, the lower electrode layer, lower adjustment layer (adjustment layer), piezoelectric layer, upper adjustment layer, and upper electrode layer can also be formed (film-forming) using a common sputtering apparatus. Furthermore, the piezoelectric layer can be single crystal or polycrystalline.

[0068] Furthermore, in the above embodiment, an example was shown where the substrate 1 was held for a predetermined period of time in a film-forming chamber 13 where the piezoelectric layer 5 had been formed and the chamber was in a lead atmosphere. However, the present invention is not limited to this. In the present invention, the substrate 1, which is heated to a predetermined film-forming temperature, can be held for a predetermined period of time in a different chamber or apparatus than the film-forming chamber where the piezoelectric layer has been formed. Furthermore, in the process of holding the substrate for a predetermined period of time while heated to a predetermined film-forming temperature, the atmosphere surrounding the substrate can be an oxygen atmosphere instead of a lead atmosphere.

[0069] Furthermore, in the above embodiments, an example was shown where the substrate 1 was held at a predetermined film-forming temperature for a specified period of 5 minutes or more but less than 60 minutes; however, the present invention is not limited to this. In the present invention, the substrate can be held at a predetermined film-forming temperature for a specified period of 60 minutes or more.

[0070] Furthermore, in the above embodiments, an example was shown where the set temperature for forming the piezoelectric layer 5 was 560°C or higher and 700°C or lower; however, the present invention is not limited thereto. In the present invention, the set temperature for forming the piezoelectric layer can be less than 560°C or more than 700°C.

[0071] Furthermore, in the above embodiments, examples are shown where the lower electrode layer 3 and the upper electrode layer 7 are formed of metallic materials such as platinum (Pt) or iridium (Ir), but the present invention is not limited thereto. In the present invention, the lower electrode layer and the upper electrode layer can be formed of materials containing titanium (Ti) or gold (Au). They can also be formed of materials such as cerium oxide (CeO2), copper oxide superconductor (LSCO), lanthanum (La), or strontium (Sr). Furthermore, the lower electrode layer and the upper electrode layer can be formed of different materials.

[0072] Symbol Explanation

[0073] 1-Substrate, 2-Insulating layer, 3-Lower electrode layer, 4-Lower conditioning layer (conditioning layer), 5-Piezoelectric film, 5a-Diffusion layer, 6-Upper conditioning layer, 7-Upper electrode layer, 12-Heating device, 13-Film forming chamber, 100-Piezoelectric film substrate, 101-Sputtering device, 102-Target component.

Claims

1. A method for manufacturing a piezoelectric film substrate, comprising: The process of forming a lower electrode layer on a substrate; The process of forming an adjustment layer containing a specified metal element on the lower electrode layer; In the process of forming a piezoelectric layer on the adjustment layer while the substrate is heated at a predetermined temperature by a heating device during film formation, the piezoelectric layer contains lead zirconate titanate having a perovskite structure. Following the process of forming the piezoelectric layer, the process continues with a process of holding the substrate for a predetermined period while the substrate is heated at the predetermined temperature set during film formation; and a process of forming an upper electrode layer after holding the substrate for the predetermined period.

2. The method for manufacturing a piezoelectric film substrate according to claim 1, wherein, The process of forming the adjustment layer includes the following steps: forming the adjustment layer, wherein the adjustment layer contains strontium and ruthenium as the specified metal elements, or contains lanthanum and nickel as the specified metal elements, and is used to adjust the orientation of the crystal of the piezoelectric layer.

3. The method for manufacturing a piezoelectric film substrate according to claim 1, wherein, The process of forming the piezoelectric layer includes the following steps: while the substrate placed in the film forming chamber is heated by the heating device at the predetermined film forming temperature, the piezoelectric layer is formed on the adjustment layer; The process of holding the substrate for the specified period includes the following steps: after the process of forming the piezoelectric layer, the substrate is held for the specified period while being heated by the heating device at the specified temperature set during film formation, with the substrate placed in the film formation chamber being heated.

4. The method for manufacturing a piezoelectric film substrate according to claim 3, wherein, The process of forming the piezoelectric layer includes the following steps: while the substrate is heated by the heating device at the temperature set during the predetermined film formation, the piezoelectric layer is formed on the adjustment layer by sputtering, wherein the sputtering utilizes sputtered particles from a lead-containing target component disposed in the film formation chamber; The process of holding the substrate for the specified period includes the following steps: following the process of sputtering the piezoelectric layer, the substrate is held for the specified period while the substrate, placed in the film-forming chamber which is in a lead atmosphere, is heated by the heating device at the specified film-forming temperature.

5. The method for manufacturing a piezoelectric film substrate according to claim 1, wherein, The process of holding the substrate for the specified period includes the following steps: holding the substrate for the specified period of 5 minutes or more and less than 60 minutes while it is heated at the specified temperature set during film formation.

6. A piezoelectric film substrate, comprising: A lower electrode layer and an upper electrode layer are formed on a substrate; An adjustment layer, formed between the lower electrode layer and the upper electrode layer, and containing a specified metal element; and A piezoelectric layer is formed on the adjustment layer while the layer is heated to a predetermined temperature during film formation, and the piezoelectric layer contains lead zirconate titanate with a perovskite structure. The piezoelectric layer includes a diffusion layer formed along the interface with the adjustment layer on the side of the lower electrode layer. The diffusion layer has a thickness of less than 10% of the total thickness of the piezoelectric layer; By continuously maintaining a state of heating at a predetermined temperature set during film formation, following the formation of the piezoelectric layer, for a predetermined period, at least one of titanium, zirconium, and lead contained in the piezoelectric layer is replaced by the predetermined metal element contained in the adjustment layer through elemental diffusion; and The diffusion layer has a region in which the detection intensity of the specified metal element contained in the diffusion layer is more than 10% higher than that of the portion of the piezoelectric layer outside the diffusion layer.

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