Method for producing a piezoelectric film substrate and piezoelectric film substrate

Abstract

A method for producing a piezoelectric film substrate according to the invention comprises: forming a lower electrode layer on or over a substrate, forming a lower matching layer having a lower matching element as a predetermined metal element, on or over the lower electrode layer, applying a piezoelectric layer having a lead zirconate titanate structure with a perovskite structure, on or over the lower matching layer, forming an upper matching layer having an upper matching element as a predetermined metal element, on or over the piezoelectric layer, forming an upper electrode layer on or over the upper matching layer, and holding the substrate for a predetermined period after the formation of the upper electrode layer, wherein the substrate is in a heated state.

Description

Technical field

[0001] The present invention relates to a method for producing a piezoelectric film substrate and a piezoelectric film substrate, and in particular a method for producing a piezoelectric film substrate and a piezoelectric film substrate in which a piezoelectric layer containing lead zirconate titanate with a perovskite structure is applied. Background technology

[0002] Methods for forming a lead zirconate titanate film with a perovskite structure are known in the art. One such method is disclosed, for example, in Japanese patent publication no. JP 6030418.

[0003] The aforementioned Japanese patent publication No. JP 6030418 discloses a method for forming a lead zirconate titanate film on a silicon substrate on which a platinum film is formed. In this method for forming the lead zirconate titanate film, the lead zirconate titanate film is applied to the platinum film, which is formed as the bottom electrode on the silicon substrate. To improve the crystallinity and dielectric strength of the applied lead zirconate titanate film, the silicon substrate is maintained at a temperature higher than that used for the application process, using a heating device, after the application process. In the method described in the aforementioned Japanese patent publication No.In the process described in JP 6030418 for forming a lead zirconate titanate film, the space in which the silicon substrate is held after the deposition process is in a lead-containing atmosphere (Pb atmosphere) filled with lead-containing molecules, such as lead atoms and lead oxides. State of the art patent document

[0004] Patent document 1: Japanese patent publication no. JP 6030418 Brief explanation of the invention Problems to be solved by the invention

[0005] However, the method described in the aforementioned Japanese patent publication No. 6030418 for forming a lead zirconate titanate film requires providing a space containing a lead atmosphere (Pb-containing atmosphere) in which the substrate is placed, in order to improve the dielectric strength of the lead zirconate titanate film (the piezoelectric layer). Furthermore, if heating is performed in a condition other than a lead atmosphere, it is conceivable that the dielectric strength of the piezoelectric layer will deteriorate, as the lead atoms contained in the lead zirconate titanate are released from the surface of the piezoelectric layer. For these reasons, it is desirable to improve the dielectric strength of a piezoelectric layer containing lead zirconate titanate in a simple manner.

[0006] The present invention is intended to solve the above-mentioned problem, and an objective of the present invention is to provide a method for producing a piezoelectric film substrate and a piezoelectric film substrate that is able to improve the dielectric strength of a piezoelectric layer containing lead zirconate titanate in a simple manner. Means for solving the tasks

[0007] To achieve the aforementioned objective, a method for producing a piezoelectric film substrate according to a first aspect of the present invention comprises: forming a lower electrode layer on or over a substrate; forming a lower matching layer, comprising a lower matching element or lower matching elements as a predetermined metal element or predetermined metal elements, on or over the lower electrode layer; applying a piezoelectric layer comprising lead zirconate titanate with a perovskite structure, on or over the lower matching layer; forming an upper matching layer, comprising an upper matching element or upper matching elements as a predetermined metal element or predetermined metal elements.comprising predetermined metal elements on or above the piezoelectric layer, forming an upper electrode layer on or above the upper matching layer, and holding the substrate for a predetermined period after the formation of the upper electrode layer, wherein the substrate is in a heated state.

[0008] As explained above, the method for producing the piezoelectric film substrate according to the first aspect of the present invention comprises holding the substrate for a predetermined period after the formation of the upper electrode layer, wherein the substrate is in a heated state. Since the upper conformal layer beneath the upper electrode layer acts as a barrier, it is thus possible to prevent the release of lead from the surface of the piezoelectric layer even when the substrate is heated. For this reason, it is possible to prevent a reduction in the dielectric strength of the piezoelectric layer due to released lead, even when the substrate is heated in a space that does not have a lead-containing atmosphere.Furthermore, the method for producing a piezoelectric film substrate according to the first aspect of the present invention, as explained above, comprises: depositing a piezoelectric layer having a lead zirconate titanate structure with a perovskite structure onto or over the lower matching layer, which has a lower matching element or lower matching elements as a predetermined metal element or elements, and forming an upper matching layer, which has an upper matching element or upper matching elements as a predetermined metal element or elements, onto or over the piezoelectric layer. Accordingly, titanium, zirconium, and lead atoms contained in the piezoelectric layer can be substituted by elemental diffusion with the metal element or elements contained in the upper and lower matching layers.This is achieved by heating the substrate, with the piezoelectric layer positioned between the upper and lower matching layers. Since lattice defects such as oxygen vacancies and lead vacancies in the piezoelectric layer can be reduced by substituting titanium, zirconium, and lead in the piezoelectric layer with a metal element or metal elements with different valences at both interfaces on the upper and lower surfaces of the piezoelectric layer, it is therefore possible to improve the dielectric strength of the piezoelectric layer.Since the dielectric strength of the piezoelectric layer can be improved, while preventing the release of lead elements even without heating the substrate in a lead-containing atmosphere, it is possible to easily improve the dielectric strength of the piezoelectric layer, which has lead zirconate titanate, while simultaneously preventing the adhesion of lead to a heating device for heating the substrate.

[0009] In the method for producing the piezoelectric film substrate according to the aforementioned first aspect, it is preferable that the application of the piezoelectric layer comprises the application of the piezoelectric layer onto or over the lower matching layer formed on or over the substrate arranged in a deposition chamber, and that the holding of the substrate for the predetermined period comprises the holding of the substrate for the predetermined period, wherein the substrate is arranged in a heat treatment furnace separate from the deposition chamber and is in a heated state.If the substrate is kept heated to improve crystallinity in the deposition chamber where the piezoelectric layer is applied, it is conceivable that particles could be generated due to material from the piezoelectric layer detaching from the inner walls or similar surfaces of the deposition chamber. Furthermore, if the substrate is heated in the deposition chamber, the thermal stress on the piezoelectric layer deposition device, which contains the deposition chamber, increases.Since in the present invention the substrate is held for the predetermined period, being placed in the heat treatment furnace, which is separate from the deposition chamber, and is in a heated state, it is possible to prevent the generation of particles that can impair the performance of the piezoelectric film substrate and at the same time to prevent an increase in the load on the device which has the deposition chamber for applying the piezoelectric layer.

[0010] In this configuration, it is preferable to hold the substrate for the predetermined period by holding a plurality of substrates together for the predetermined period, with the majority of substrates placed in a heated state in the heat treatment furnace. According to this configuration, it is possible to reduce the time required to produce a plurality of piezoelectric film substrates compared to a case in which the piezoelectric film substrates are held individually in a heated state.

[0011] In the process for producing the piezoelectric film substrate according to the aforementioned first aspect, it is preferable that the formation of the lower adaptation layer comprises: forming a lower adaptation layer containing strontium and ruthenium as lower adaptation elements, or lanthanum and nickel as lower adaptation elements, to adapt the crystal orientation of the piezoelectric layer; and that the formation of the upper adaptation layer comprises forming an upper adaptation layer containing strontium and ruthenium as upper adaptation elements, or lanthanum and nickel as upper adaptation elements. According to this configuration, the crystallinity of the piezoelectric layer can be improved, since the crystal orientation of the piezoelectric layer is adapted by depositing the piezoelectric layer on or above the lower adaptation layer.Here, strontium, ruthenium, lanthanum, and nickel each tend to form cations with a lower valence than the titanium and zirconium contained in the lead zirconate titanate of the piezoelectric layer. Therefore, when titanium and zirconium in the piezoelectric layer are substituted by elemental diffusion with any of the strontium, ruthenium, lanthanum, and nickel, the overall charge of the piezoelectric layer tends to decrease, thus reducing the number of lead vacancies in the piezoelectric layer to increase the charge and maintain electrical neutrality.Furthermore, if lead in the piezoelectric layer is replaced by elemental diffusion with a higher-valence metal element, such as lanthanum, the oxygen vacancies in the piezoelectric layer are reduced, thus decreasing the overall charge of the piezoelectric layer and maintaining electrical neutrality. Since the piezoelectric layer is positioned between the lower matching layer and the upper matching layer, which contains strontium and ruthenium or lanthanum and nickel, vacancies in the piezoelectric layer can consequently be reduced by inducing elemental diffusion at both an upper and a lower interface of the piezoelectric layer, thereby improving its dielectric strength. This makes it possible to further enhance the dielectric strength of the piezoelectric layer.

[0012] In this configuration, it is preferable for the upper matching layer to be formed as follows: The upper matching layer contains the same metal elements as the lower matching elements in the lower matching layer and has an identical composition to the lower matching layer. According to this configuration, both the upper and lower matching layers can be made of the same material. Consequently, compared to a case where the upper and lower matching layers contain different metal elements, the types of materials used to manufacture the piezoelectric film substrate can be reduced, thereby decreasing the manufacturing effort for the piezoelectric film substrate.

[0013] In the process for producing the piezoelectric film substrate according to the aforementioned first aspect, it is preferable that the substrate be held in a heated state for a predetermined period of at least five minutes and at least sixty minutes. If the period during which the substrate is held in a heated state is too short, the improvement in the dielectric strength of the piezoelectric layer will be insufficient due to the difficulty in inducing element diffusion from the lower and upper conditioning layers.Furthermore, if the period during which the substrate is kept in a heated state is too long, the properties of the piezoelectric layer deteriorate due to excessive element substitution caused by element diffusion from the lower and upper matching layers. In contrast, with the present invention, the substrate can be kept in a heated state for a predetermined period of at least five and at least sixty minutes. Consequently, the dielectric strength of the piezoelectric layer can be further improved compared to cases where the maintenance time is too short or too long.

[0014] In the method for producing the piezoelectric film substrate according to the aforementioned first aspect, it is preferable that the application of the piezoelectric layer comprises the application of the piezoelectric layer onto or over the lower matching layer by sputtering, wherein the substrate is in a heated state at a predetermined application setting temperature using a heating device, and that the holding of the substrate for the predetermined period comprises holding the substrate for the predetermined period, wherein the substrate is in a heated state at a temperature higher than the predetermined application setting temperature during sputtering to apply the piezoelectric layer.Since substitution by elemental diffusion progresses with increasing temperature, the substrate can be kept at a sufficiently high temperature during sputtering to deposit the piezoelectric layer by maintaining it in a heated state at a temperature higher than the predetermined deposition temperature. Consequently, it is possible to prevent insufficient elemental diffusion due to an excessively low heating temperature and thus avoid an inadequate improvement in dielectric strength.

[0015] To achieve the aforementioned objective, a piezoelectric film substrate according to a second aspect of the present invention comprises: a lower electrode layer formed on or above a substrate, a lower matching layer formed on or above the lower electrode layer and comprising a lower matching element as a predetermined metal element, a piezoelectric layer applied on or above the lower matching layer and comprising lead zirconate titanate with a perovskite structure, an upper matching layer formed on or above the piezoelectric layer and comprising an upper matching element as a predetermined metal element, and an upper electrode layer formed on or above the upper matching layer, wherein the piezoelectric layer comprises a lower diffusion layer formed along an interface with the lower matching layer, and an upper diffusion layer.which is formed along an interface with the upper matching layer, wherein the lower diffusion layer has a thickness of less than or equal to 10% of the film thickness of the entire piezoelectric layer, at least one of titanium, zirconium, or lead contained in the piezoelectric layer is substituted in the lower diffusion layer by elemental diffusion with the lower matching element contained in the lower diffusion layer, the lower diffusion layer has a region in which a detection intensity ratio of the lower matching element contained in the lower diffusion layer is 10% or more greater than in a section of the piezoelectric layer that is not the upper diffusion layer and the lower diffusion layer in the piezoelectric layer, the upper diffusion layer has a thickness of less than or equal to 10% of the film thickness of the entire piezoelectric layer,at least one of titanium, zirconium or lead contained in the piezoelectric layer is substituted in the upper diffusion layer by elemental diffusion with the upper matching element contained in the upper matching layer, and the upper diffusion layer has a region in which a detection intensity ratio of the upper matching element contained in the upper diffusion layer is 10% or more greater than that in the section of the piezoelectric layer that is not the upper diffusion layer and the lower diffusion layer in the piezoelectric layer.

[0016] As explained above, the piezoelectric film substrate according to the second aspect of the present invention has an upper matching layer formed on or above the piezoelectric layer and comprising an upper matching element as a predetermined metal element. Since the upper matching layer acts as a barrier, it is accordingly possible to prevent the release of lead from the surface of the piezoelectric layer even when the substrate is heated. For this reason, it is possible to prevent a reduction in the dielectric strength of the piezoelectric layer due to released lead even when the substrate is heated in a space that does not have a lead-containing atmosphere.Furthermore, according to the second aspect of the present invention, as explained above, the piezoelectric film substrate comprises: a piezoelectric layer applied on or above the lower matching layer, comprising lead zirconate titanate with a perovskite structure, and an upper matching layer formed on or above the piezoelectric layer, comprising an upper matching element as a predetermined metal element. Accordingly, the titanium, zirconium, and lead atoms contained in the piezoelectric layer can be substituted by elemental diffusion with the metal element contained in the upper and lower matching layers by heating the substrate, wherein the piezoelectric layer is positioned between the upper and lower matching layers.For this reason, it is possible to improve the dielectric strength of the piezoelectric layer, as lattice defects such as oxygen vacancies and lead vacancies in the piezoelectric layer can be reduced by substituting titanium, zirconium, and lead in the piezoelectric layer with a metal element having different valences at both interfaces on the top and bottom surfaces of the piezoelectric layer. Since this improves the dielectric strength of the piezoelectric layer while preventing the release of lead elements even without heating the substrate in a lead-containing atmosphere, it is possible to provide a piezoelectric film substrate capable of easily improving the dielectric strength of the lead-zirconate-titanate piezoelectric layer and simultaneously preventing lead from adhering to a heating device used to heat the substrate. Effect of the invention

[0017] As explained above, according to the present invention it is possible to easily improve the dielectric strength of a piezoelectric layer comprising lead zirconate titanate. Brief description of the drawings

[0018] They show: Fig. 1 a sectional view showing a piezoelectric film substrate according to one embodiment, Fig. 2 a diagram schematically showing a perovskite structure of lead zirconate titanate in a piezoelectric layer, Fig. 3 a diagram showing an upper diffusion layer and a lower diffusion layer contained in the piezoelectric layer, Fig. 4 a diagram schematically showing a configuration of a sputtering device, Fig. 5 a diagram that schematically shows a configuration of a heat treatment furnace, Fig. 6 a flowchart showing a method for producing the piezoelectric film substrate according to the embodiment. Types of embodiments of the invention

[0019] The following description describes embodiments according to the present invention with reference to the drawings. (Configuration of a piezoelectric film substrate)

[0020] A configuration of a piezoelectric film substrate 100 according to an embodiment of the present invention is described with reference to Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5 described.

[0021] The piezoelectric film substrate 100 is a piezoelectric film substrate that can be divided into a plurality of parts, which are considered devices. Each of these parts becomes a device. For example, a MEMS (Micro Electro Mechanical Systems) device can be used as a sensor or actuator.

[0022] As in Fig. As shown in Figure 1, the piezoelectric film substrate 100 comprises: a substrate 1, an electrically insulating layer 2, a lower electrode layer 3, a lower matching layer 4, a piezoelectric layer 5, an upper matching layer 6, and an upper electrode layer 7. In the piezoelectric film substrate 100, the electrically insulating layer 2, the lower electrode layer 3, the lower matching layer 4, the piezoelectric layer 5, the upper matching layer 6, and the upper electrode layer 7 are laminated onto the substrate 1 in that order. In the piezoelectric film substrate 100, the electrically insulating layer 2, the lower electrode layer 3, and the lower matching layer 4 form a multilayer film lower electrode located beneath the piezoelectric layer 5.Furthermore, in the piezoelectric film substrate 100, the upper matching layer 6 and the upper electrode layer 7 form a multilayer film upper electrode on the piezoelectric layer 5.

[0023] Substrate 1 is a silicon substrate. The electrically insulating layer 2 is a thin film formed from an electrically insulating material on substrate 1. For example, the electrically insulating layer 2 is formed from silicon dioxide (SiO2). The electrically insulating layer 2 can be formed from a material such as zirconium oxide (ZrO2) or yttrium oxide-stabilized zirconium oxide (YSZ). For example, the electrically insulating layer 2 has a silicon oxide layer formed by thermal oxidation of the silicon substrate 1 on the surface of substrate 1. The thickness of substrate 1 is, for example, not less than approximately 300 µm and not more than approximately 725 µm. The thickness of the electrically insulating layer 2 is, for example, not less than approximately 100 nm and not more than approximately 500 nm.

[0024] The lower electrode layer 3 is formed on the electrically insulating layer 2 on the substrate 1. Specifically, the lower electrode layer 3 is grown epitaxially as a single crystal. For example, the lower electrode layer 3 is made of a material such as platinum (Pt) or iridium (Ir). The thickness of the lower electrode layer 3 is, for example, no less than approximately 50 nm and no more than approximately 200 nm.

[0025] The lower matching layer 4 is formed on the lower electrode layer 3 above the substrate 1. The lower matching layer 4 has lower matching elements that are predetermined metal elements. The lower matching layer 4 comprises a metal oxide. The lower matching layer 4 has strontium (Sr) and ruthenium (Ru) as lower matching elements that are predetermined metal elements, or it has lanthanum (La) and nickel (Ni) as lower matching elements that are predetermined metal elements. The lower matching layer 4 is formed from a material such as strontium ruthenate (SrRuO3: SRO), which contains strontium and ruthenium, or lanthanum nickel oxide (LaNiO3: LNO), which contains lanthanum and nickel. The lower matching layer 4 matches the crystal orientation of the piezoelectric layer 5. In particular, the metal oxide forming the lower matching layer 4 is crystalline.The lower matching layer 4 functions as a seed layer (seed crystal layer) to achieve the desired crystal orientation of the piezoelectric layer 5. The thickness of the lower matching layer 4 is, for example, no less than approximately 2 nm and no more than approximately 40 nm.

[0026] The piezoelectric layer 5 is formed on the lower matching layer 4, which is positioned above the substrate. Furthermore, the piezoelectric layer 5 contains lead zirconate titanate (PZT), which exhibits ferroelectricity. The piezoelectric layer 5 is made of polycrystalline lead zirconate titanate (PZT). The thickness of the piezoelectric layer 5 is, for example, no less than approximately 0.75 µm and no more than approximately 5 µm.

[0027] As in Fig. As shown in Figure 2, the piezoelectric layer 5 has a lead zirconate titanate structure with a perovskite structure. In the perovskite structure, metallic elements are positioned at all A-sites, which are the vertices of the cubic crystal lattice, and at the B-site, which is the body center, while oxygen atoms (O) occupy all face centers of the surfaces around the B-site. In lead zirconate titanate, lead atoms (Pb) occupy the A-sites of the perovskite structure, and a titanium atom (Ti) or zirconium atom (Zr) occupies the B-site.

[0028] As in Fig. As shown in Figure 1, the upper matching layer 6 is formed on the piezoelectric layer 5, which is arranged above the substrate 1. The upper matching layer 6 has: upper matching elements that are predetermined metal elements common to the lower matching layer 4, or upper matching elements that are different metal elements than those of the lower matching layer 4. In other words, the upper matching layer 6 has a metal oxide. The upper matching layer 6 has: strontium (Sr) and ruthenium (Ru) as upper matching elements that are predetermined metal elements, or lanthanum (La) and nickel (Ni) as upper matching elements that are predetermined metal elements. The upper matching layer 6 is formed from a material such as strontium ruthenate (SrRuO3: SRO), which contains strontium and ruthenium, or lanthanum nickel oxide (LaNiO3: LNO), which contains lanthanum and nickel.For example, the upper matching layer 6 contains the upper matching elements, which are metallic elements common to the lower matching elements, where these are predetermined metallic elements contained in the lower matching layer 4, and is a thin film with a composition identical to that of the lower matching layer 4. In one example, both the lower matching layer 4 and the upper matching layer 6 have a common combination of metallic elements and are formed from strontium ruthenate (SrRuO3: SRO). The upper matching layer 6 functions as a barrier layer that prevents the movement (diffusion) of elements such as oxygen or lead from the piezoelectric layer 5 toward the side of the upper electrode layer 7. The upper matching layer 6 can be crystalline or amorphous.The upper matching layer 6 is designed to have a thickness of, for example, not less than about 2 nm and not more than about 40 nm.

[0029] The upper electrode layer 7 is formed on the upper matching layer 6, which is arranged above 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 thickness of the upper electrode layer 7 is, for example, no less than approximately 50 nm and no more than approximately 500 nm. The upper electrode layer 7 can be made of a material common to the lower electrode layer 3 or of a material different from the lower electrode layer 3. The materials of the upper matching layer 6, the upper electrode layer, and the upper electrode layer 7 are not particularly restricted. Additionally, an insulating layer, such as a silicon dioxide layer, can be formed on the upper electrode layer 7.

[0030] In the piezoelectric film substrate 100 according to this embodiment, after the formation of the upper electrode layer 7, an annealing process is carried out to reduce lattice defects in the piezoelectric layer 5 by keeping the substrate 1, on which the piezoelectric layer 5 is applied, in a heated state. During the annealing process, titanium, zirconium, and lead contained in the piezoelectric layer 5 are substituted by thermal elemental diffusion with the metallic elements (strontium and ruthenium or lanthanum and nickel) contained in the lower matching layer 4 and the upper matching layer 6. The substitution by elemental diffusion occurs in a region of the piezoelectric layer 5 along the interface with the lower matching layer 4 and in a region of the piezoelectric layer 5 along the interface with the upper matching layer 6.

[0031] As in Fig. As shown in Figure 3, the piezoelectric layer 5 in the piezoelectric film substrate 100 has a lower diffusion layer 5a and an upper diffusion layer 5b. In the lower diffusion layer 5a, at least one of the titanium, zirconium, or lead contained in the piezoelectric layer is substituted by elemental diffusion with the predetermined metal elements (lower matching elements) contained in the lower matching layer 4 by keeping the substrate in a heated state after the formation of the upper electrode layer 7. The lower diffusion layer 5a is formed on the underside of the piezoelectric layer 5, which has an upper and a lower surface, along the interface with the lower matching layer 4.The lower diffusion layer 5a has a region where the detection intensity ratio of the lower matching elements, which are predetermined metal elements (strontium and ruthenium or lanthanum and nickel) contained in the lower diffusion layer 5a, is 10% or more greater than that in a section of the piezoelectric layer 5 that is not the lower diffusion layer 5a and the upper diffusion layer 5b of the piezoelectric layer. In the upper diffusion layer 5b, at least one of the titanium, zirconium, or lead contained in the piezoelectric layer 5 is substituted by elemental diffusion with the predetermined metal elements (upper matching elements) contained in the upper matching layer 6 by maintaining the substrate in a heated state after the formation of the upper electrode layer 7.The upper diffusion layer 5b is formed on the top surface of the piezoelectric layer 5, which has a top and a bottom surface, along the interface with the upper matching layer 6. The upper diffusion layer 5b has a region where the detection intensity ratio of the upper matching elements, which are predetermined metallic elements (strontium and ruthenium or lanthanum and nickel) contained in the upper diffusion layer 5b, is 10% or more greater than that in a section of the piezoelectric layer 5 that is not the lower diffusion layer 5a and the upper diffusion layer 5b of the piezoelectric layer. The detection intensity ratios of the upper and lower matching elements are detected, for example, by SIMS (secondary ion mass spectrometry). <sputtervorrichtung>

[0032] As in Fig. As shown in Figure 4, in this embodiment the piezoelectric layer 5 is deposited by sputtering using a sputtering device 101. The sputtering device 101 is configured to eject target particles (sputter particles) from a target material 102 containing titanium (Ti), zirconium (Zr), and lead (Pb), which are the materials of the piezoelectric layer 5, and to deposit the ejected sputtered particles onto the substrate 1 to form a thin film of sputtered particles from the target material 102 on the substrate (the piezoelectric film substrate 100). The sputtering device 101 comprises a substrate stage 11, a heating device 12, a deposition chamber 13, and a vacuum pump 14.

[0033] The sputtering device 101 introduces gases such as argon (Ar) and oxygen (O2) into the deposition chamber 13, which has been emptied, for example, by a vacuum pump 14. The sputtering device 101 then applies a voltage to the target material 102 arranged in the deposition chamber 13 to generate plasma in the deposition chamber 13. Through the collision of charged particles in the plasma (e.g., argon ions) with the target material 102, sputtered particles containing titanium (Ti), zirconium (Zr), and lead (Pb) are ejected from the target material 102. The ejected sputtered particles are deposited onto the substrate 1 (piezoelectric film substrate 100), which is mounted on the substrate stage 11, to form a thin film on the surface of the substrate 1 and thereby deposit the piezoelectric layer 5.

[0034] The heating device 12 is configured to heat the substrate 1, which is mounted on the substrate table 11, within the sputtering device 101. 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 located. The heating device 12 may, for example, have an electric heating wire. Sputtering is performed in the sputtering device 101 while the substrate 1 is located in the deposition chamber 13 in a heated state at the application set temperature, which is a predetermined temperature. The heating device 12 is controlled to maintain the substrate 1 at the predetermined application set temperature during the sputtering process.In other words, the power of the heating device 12 is controlled to maintain the substrate 1 at the predetermined constant deposition temperature during the sputtering process. For example, when the piezoelectric layer 5 is being applied with a thickness of 2 µm, the sputtering process takes approximately 20 minutes.

[0035] Furthermore, the sputtering device 101 includes a control unit 15. The control unit 15 controls components of the sputtering device 101. The control unit 15 includes: a processing unit comprising a CPU (Central Processing Unit) and memory, for example, flash memory. The control unit 15 controls the sputtering process by the sputtering device 101 based on a program and parameters stored in the memory. In particular, the control unit 15 controls the application of a voltage to the target material 102, the operation of the vacuum pump 14, and the operation of the heating device 12. <Wärmebehandlungsofen>

[0036] As in Fig. As shown in Figure 5, in this embodiment an annealing process is carried out by holding the substrate 1 (piezoelectric film substrate 100), on which the upper electrode layer 7 has been formed, in a heated state for a predetermined period in a heat treatment furnace 103, which is distinct from the deposition chamber 13 of the sputtering device 101. Furthermore, during the annealing process, batch processing is performed on a plurality of substrates 1 together in a heat treatment furnace 103. A heating device 21 is arranged in the heat treatment furnace 103. In addition, the heat treatment furnace 103 is configured to allow a plurality of substrates 1 (a plurality of piezoelectric film substrates 100) to be placed in it. The plurality of substrates 1 are arranged side by side in the heat treatment furnace 103 in directions along their main surfaces.In the heat treatment furnace 103, the majority of adjacent substrates 1 are kept together in a heated state, so that the annealing treatment is carried out on the majority of substrates 1 in a stacked manner. In the heat treatment furnace 103, the substrates 1 are heated, for example, in an oxygen-containing atmosphere into which oxygen is supplied. (Method for producing the piezoelectric film substrate)

[0037] A method for producing the piezoelectric film substrate 100 is now described with reference to Fig. 6 described. The method for producing the piezoelectric film substrate 100 is a method for producing a piezoelectric film substrate which can be divided into a plurality of parts as devices.

[0038] As in Fig. Figure 6 shows the manufacturing process for the piezoelectric film substrate 100, comprising: step S1 for providing the substrate 1, step S2 for forming the electrically insulating layer 2, step S3 for forming the lower electrode layer 3 arranged over the substrate 1, step S4 for forming the lower matching layer 4, step S5 for applying the piezoelectric layer 5 to the lower matching layer 4, step S6 for forming the upper matching layer 6 on the piezoelectric layer 5, step S7 for forming the upper electrode layer 7 arranged over the substrate 1, and step S8 for holding the piezoelectric film substrate 100 for a predetermined period. In the method for manufacturing the piezoelectric film substrate 100 according to this embodiment, steps S1 to S8 are carried out in this order.

[0039] First, in step S1, during the process of providing substrate 1, the substrate 1, which is a silicon substrate, is provided. Then, in step S2, during the process of forming the electrically insulating layer 2, the silicon (Si) substrate that forms substrate 1 is thermally oxidized at a temperature of approximately 700 °C to form the electrically insulating layer 2, which is a silicon oxide layer formed from SiO2, on the surface of substrate 1.

[0040] Subsequently, in step S3, during the formation of the lower electrode layer 3, which is arranged above the substrate 1, the lower electrode layer 3 is formed by sputtering onto the electrically insulating layer 2, which is arranged above the substrate 1. Then, in step S4, during the formation of the lower matching layer 4, after the formation of the lower electrode layer 3, the lower matching layer 4 is formed by sputtering onto the lower electrode layer 3, which is arranged above the substrate 1. During the formation of the lower matching layer 4, the substrate 1 is heated to approximately 500 °C. This causes the metal oxide of the lower matching layer 4 to crystallize. Here, the lower electrode layer 3 and the lower matching layer 4 can be formed using a common sputtering device or they can be formed using separate sputtering devices.

[0041] In step S5, during the process of depositing the piezoelectric layer 5 onto the lower matching layer 4, the piezoelectric layer 5 is deposited onto the lower matching layer 4, which is formed over the substrate 1, by sputtering in a state heated to the predetermined deposit temperature. In this case, the sputtering used to deposit the piezoelectric layer 5 is performed by a sputtering device 101 that is different from the sputtering device used to form the lower electrode layer 3 and the lower matching layer 4.

[0042] In this embodiment, the piezoelectric layer 5 is applied to the lower matching layer 4 by sputtering sputtered particles from the target material 102. The substrate 1 (piezoelectric film substrate 100) is arranged in the deposition chamber 13 of the sputtering device 101 and is heated to a predetermined application temperature using the heating device 12. The sputtering is performed in a state where the deposition chamber 13 is emptied by the vacuum pump 14. It should be noted that the term "vacuum" refers to a pressure lower than atmospheric pressure. In the sputtering device 101, the control unit 15 heats the substrate 1, over which the lower matching layer 4 is formed, to a predetermined application temperature using the heating device 12.The control unit 15 then starts sputtering to deposit the piezoelectric layer 5 onto the substrate 1 in a heated state at the deposition setting temperature. The control unit 15 performs the sputtering by applying voltage to the target material 102 for a predetermined period until the piezoelectric layer 5 is deposited with a predetermined film thickness. During the period in which the piezoelectric layer 5 is deposited by sputtering, the control unit 15 controls the operation of the heating device 12 to maintain the substrate 1 at a predetermined deposition setting temperature. After a predetermined time (e.g., 20 minutes), the sputtering is stopped. Here, the predetermined deposition setting temperature is not lower than approximately 560 °C and not higher than approximately 700 °C. For example, the predetermined deposition setting temperature is approximately 600 °C.Here, the predetermined application temperature refers to the temperature of substrate 1, which is set as the target temperature for heating by the heating device 12. In other words, the predetermined application temperature is a value that does not account for temperature fluctuations of substrate 1 caused by factors other than the heating device 12. Consequently, the actual temperature of substrate 1 may deviate from the predetermined application temperature target due to factors such as the presence or absence of plasma during sputtering. Furthermore, if the sputtering device 101 is equipped with a display to show the temperature of substrate 1, the actual temperature of substrate 1 may differ from the temperature displayed.The "predetermined application setpoint temperature" is a target temperature that does not exhibit temperature fluctuations of substrate 1 due to factors other than the heating device. Such factors other than the heating device can lead to an error between the predetermined application setpoint temperature and the actual temperature of substrate 1. Substrate 1 is heated so that lead zirconate titanate, which has a perovskite structure, crystallizes.

[0043] Subsequently, in step S6, during the process of forming the upper matching layer 6 on the piezoelectric layer 5, the upper matching layer 6 is formed for sputtering and laminated onto the piezoelectric layer 5, which is positioned over the substrate 1. Then, in step S7, during the process of forming the upper electrode layer 7, which is positioned over the substrate 1, the upper matching layer 6 is formed, and the upper electrode layer 7 is then sputtered onto the upper matching layer 6, which is positioned over the substrate 1. For example, the process of forming the upper matching layer 6 and the upper electrode layer 7 is performed without heating the substrate 1 (piezoelectric film substrate 100).Here, the upper matching layer 6 and the upper electrode layer 7 can be formed by a common sputtering device or can be formed by different sputtering devices.

[0044] Subsequently, after the formation of the upper matching layer 6 (step S6) and the formation of the upper electrode layer 7 (step S7), in step S8, the substrate 1 (the piezoelectric film substrate 100), over which the piezoelectric layer 5 (piezoelectric film substrate 100) has been applied, is held for a predetermined period while the substrate 1 is in a heated state. In other words, after the upper matching layer 6 and the upper electrode layer 7 have been formed, an annealing process is carried out in step S8 to hold the substrate 1 in place for a predetermined period.Furthermore, in the process of holding the substrate 1 for a predetermined period in step S8, the substrate 1, which is located in the heat treatment furnace 103 (different from the deposition chamber 13 in which the piezoelectric layer 5 is deposited), is held for a predetermined period, with the substrate 1 being in a heated state at a temperature higher than the predetermined deposition temperature during sputtering. During the process of holding the substrate 1 in the heat treatment furnace 103 in step S8, the interior of the heat treatment furnace 103 is in an oxygen atmosphere due to the oxygen supply. In the heat treatment furnace 103, the operation of the heating device 21 is controlled by a control device (not shown) to maintain the substrate 1 heated at a temperature higher than the predetermined deposition temperature.In step S8, the substrate 1 is held in a heated state at not less than 550 °C and not more than 650 °C. In the heat treatment furnace 103, for example, the substrate 1 is held in a heated state at approximately 650 °C, which is higher than the application setting temperature of approximately 600 °C. The predetermined period during which the substrate 1 is held in a heated state at the predetermined application setting temperature by the annealing process in step S8 after application is a period that is not less than five minutes and less than sixty minutes, preferably a period that is not less than twenty minutes and not more than forty minutes, and even more preferably thirty minutes.

[0045] In this embodiment, the annealing process in step S8 reduces lattice defects such as oxygen vacancies and lead vacancies contained in the piezoelectric layer 5. During the annealing process following the deposition of the piezoelectric layer 5, metallic elements (lower matching elements) contained in the lower matching layer 4 below the piezoelectric layer 5 and metallic elements (upper matching elements) contained in the upper matching layer 6 on top of the piezoelectric layer 5 diffuse into the piezoelectric layer 5 by elemental diffusion. As a result of this elemental diffusion, titanium (Ti), zirconium (Zr), and lead (Pb) in the lead zirconate titanate of the piezoelectric layer 5 are substituted by strontium and ruthenium (Sr and Ru) or lanthanum and nickel (La and Ni) contained in each of the lower matching layer 4 and the upper matching layer 6.For example, if the lower matching layer 4 and the upper matching layer 6 are formed from lanthanum nickel oxide (LaNiO3), titanium (Ti) or zirconium (Zr), which occupy the B sites of the piezoelectric layer 5, is substituted with lanthanum (La) or nickel (Ni) contained in the lower matching layer 4 and the upper matching layer 6. When titanium (Ti) or zirconium (Zr) with a valence of 4+ is substituted with lanthanum (La) or nickel (Ni) with a valence of 2+ or 3+ to maintain electrical neutrality, lead vacancies, which can be considered anionic, are reduced. Furthermore, if lead (Pb) with a valence of 2+, which occupies A-sites of the piezoelectric layer 5, is substituted with lanthanum (La) with a valence of 3+, the oxygen vacancies, which can be considered as cations, are reduced in order to maintain electrical neutrality.As described above, lattice defects such as oxygen vacancies and lead vacancies in the piezoelectric layer 5 are reduced by substituting titanium, zirconium and lead in the piezoelectric layer 5 with metal elements with different valences.

[0046] Furthermore, in this embodiment, the annealing process is carried out on a plurality of substrates 1 (piezoelectric film substrates 100) together in the process of holding the substrate 1 (piezoelectric film substrate 100) for a predetermined period in step S8. In particular, a plurality of substrates 1 are held together for the predetermined period, wherein the plurality of substrates 1 are placed in the heat treatment furnace 103 in a heated state.In other words, by repeatedly performing the processes from step S1 to step S7, or by providing a plurality of production lines, a plurality of substrates 1 are produced, on which the upper electrode layers 7 are formed. Subsequently, the process in step S8 is carried out such that the plurality of substrates 1, on which the upper electrode layers 7 are formed, 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 processes from step S1 to step S8 produce the piezoelectric film substrate 100.

[0047] Subsequently, during the processing to form the device shape, photolithography is applied to the substrate to structure the lower electrode (lower electrode layer 3 and lower matching layer 4), the piezoelectric layer 5, and the upper electrode (upper matching layer 6 and upper electrode layer 7) into the device shapes. In the case of photolithography, the processing is carried out on the piezoelectric film substrate 100 to structure the lower electrode, the piezoelectric film, and the upper electrode into the device shapes by removing unnecessary sections and obtaining required sections by wet etching using an etching solution or dry etching using an etching gas.Furthermore, when the piezoelectric film substrate 100 is divided into parts for the devices, the piezoelectric film substrate 100 is cut into parts for the devices, for example using a blade. (Advantages of the design)

[0048] This embodiment offers the following advantages.

[0049] In this embodiment, as described above, the manufacturing process for a piezoelectric film substrate 100 comprises, after a step of forming the upper electrode layer 7 while the substrate 1 is in a heated state (step S7), a step of holding the substrate 1 for a predetermined period (step S8). Since the upper conformal layer 6 located beneath the upper electrode layer 7 acts as a barrier, it is possible to prevent the release of lead from the surface of the piezoelectric layer 5, even when the substrate 1 is heated. Therefore, it is possible to prevent a reduction in the dielectric strength of the piezoelectric layer 5 due to released lead, even when the substrate 1 is heated in a space without a lead-containing atmosphere.Furthermore, the method for producing a piezoelectric film substrate 100 in this embodiment comprises: a step of applying the piezoelectric layer 5, which has a lead zirconate titanate structure with a perovskite structure, to the lower matching layer 4, which has lower matching elements as predetermined metal elements (step S5), and a step of forming the upper matching layer 6, which has upper matching elements as predetermined metal elements, onto the piezoelectric layer 5 (step S6). Accordingly, titanium, zirconium, and lead atoms contained in the piezoelectric layer 5 can be substituted by elemental diffusion with the metal elements contained in the upper matching layer 6 and the lower matching layer 4 by heating the substrate 1, wherein the piezoelectric layer 5 is arranged between the upper matching layer 6 and the lower matching layer 4.For this reason, it is possible to improve the dielectric strength of the piezoelectric layer 5, since lattice defects such as oxygen vacancies and lead vacancies in the piezoelectric layer 5 can be reduced by substituting titanium, zirconium, and lead in the piezoelectric layer 5 with metal elements of different valences at both interfaces on the top and bottom surfaces of the piezoelectric layer 5. Since the dielectric strength of the piezoelectric layer 5 can be improved while preventing the release of lead elements even without heating the substrate 1 in a lead-containing atmosphere, it is consequently possible to easily improve the dielectric strength of the lead-zirconate-titanate piezoelectric layer 5 and simultaneously prevent the adhesion of lead to a heating device (heat treatment furnace 103) used to heat the substrate 1.

[0050] In this embodiment, the manufacturing process of a piezoelectric film substrate 100, as described above, includes a step of applying the piezoelectric layer 5 to the lower leveling layer 4 formed over the substrate 1, which is arranged in the deposition chamber 13 (step S5). The process for manufacturing a piezoelectric film substrate 100 includes a step of holding the substrate 1 for a predetermined period, wherein the substrate 1 is arranged in the heat treatment furnace 103, which is separate from the deposition chamber 13 (step S8). When the substrate 1 is held in a heated state to improve the crystallinity in the deposition chamber 13, in which the piezoelectric layer 5 is applied, it is conceivable that particles may be generated, as materials of the piezoelectric layer 5 detach from the inner walls or the like of the deposition chamber 13.Furthermore, if the substrate 1 is heated in the deposition chamber 13, the thermal load on the device for applying the piezoelectric layer 5, which comprises the deposition chamber 13, increases. However, since in this embodiment the substrate 1 is held for the predetermined period in the heat treatment furnace 103, which is separate from the deposition chamber 13, and is in a heated state, it is possible to prevent the generation of particles that could impair the performance of the piezoelectric film substrate 100 and simultaneously prevent an increase in the load on the device comprising the deposition chamber 13 for applying the piezoelectric layer 5.Furthermore, in this embodiment, a step of holding the substrate 1 in a heated state for a predetermined period (step S8) is performed in the heat treatment furnace 103, which differs from the device for forming the upper electrode layer 7 (sputtering device). Since the upper electrode layer 7 is generally formed at room temperature without heating the substrate 1, performing a step of holding the substrate 1 in a heated state in a device for forming the upper electrode layer 7 would require an additional heating device in the device for forming the upper electrode layer 7.For this reason, it becomes necessary to equip the device with a heating function and heat resistance that are unnecessary for forming the upper electrode layer 7, and the thermal load on the device for forming the upper electrode layer 7 also increases. In contrast, as in this embodiment, by carrying out the step of keeping the substrate 1 in a heated state for a predetermined period (step S8) in the heat treatment furnace 103, which is separate from the device for forming the upper electrode layer 7 (sputtering device), it is possible to prevent the provision of components that are not required for forming the upper electrode layer 7 in the device for forming the upper electrode layer 7 and also to prevent an increase in the load on the device for forming the upper electrode layer 7.

[0051] In this embodiment, the method for producing a piezoelectric film substrate 100, as described above, includes a step of holding a plurality of the substrates 1 together for a predetermined period, wherein the plurality of substrates 1 are placed in the heat treatment furnace 103 in a heated state (step S8). According to this configuration, it is possible to reduce the time required for producing a plurality of substrates 1 (piezoelectric film substrates 100) compared to a case in which the piezoelectric film substrates 100 are held individually in a heated state.

[0052] In this embodiment, the method for producing the piezoelectric film substrate 100, as described above, includes a step of forming the lower matching layer 4, which contains strontium and ruthenium as lower matching elements or lanthanum and nickel as lower matching elements to match the crystal orientation of the piezoelectric layer 5 (step S4). The method for producing a piezoelectric film substrate 100 includes a step of forming the upper matching layer 6, which contains strontium and ruthenium as upper matching elements or lanthanum and nickel as upper matching elements (step S6). Accordingly, the crystallinity of the piezoelectric layer 5 can be improved because the crystal orientation of the piezoelectric layer 5 is matched by depositing the piezoelectric layer 5 onto the lower matching layer 4.Here, strontium, ruthenium, lanthanum, and nickel each tend to form cations with a lower valence than the titanium and zirconium contained in the lead zirconate titanate of piezoelectric layer 5. For this reason, the charge of the entire piezoelectric layer 5 tends to decrease when titanium and zirconium in the piezoelectric layer 5 are substituted by elemental diffusion with strontium, ruthenium, lanthanum, and nickel. Consequently, the number of lead vacancies contained in the piezoelectric layer 5 is reduced to increase the charge and maintain electrical neutrality.Furthermore, if lead in the piezoelectric layer 5 is replaced by elemental diffusion with a metal element of higher valence, such as lanthanum, the oxygen vacancies in the piezoelectric layer 5 are reduced, thus reducing the overall charge of the piezoelectric layer 5 and maintaining electrical neutrality. Since the piezoelectric layer 5 is positioned between the lower matching layer 4 and the upper matching layer 6, which contain strontium and ruthenium or lanthanum and nickel, the vacancies in the piezoelectric layer 5 can be further reduced by inducing elemental diffusion at both an upper and a lower interface of the piezoelectric layer 5, thereby improving its dielectric strength. Consequently, it is possible to further enhance the dielectric strength of the piezoelectric layer 5.

[0053] In this embodiment, the method for producing a piezoelectric film substrate 100, as described above, includes a step of forming the upper matching layer 6, which has the upper matching elements being metal elements common to the lower matching elements contained in the lower matching layer 4, and which has a composition identical to that of the lower matching layer 4 (step S6). According to this configuration, both the upper matching layer 6 and the lower matching layer 4 can be formed from the same material.Consequently, compared to a case in which the upper matching layer 6 and the lower matching layer 4 contain metal elements that are different from each other, the types of materials used to manufacture the piezoelectric film substrate 100 can be reduced, thereby reducing the manufacturing effort for the piezoelectric film substrate 100.

[0054] In this embodiment, the method for producing a piezoelectric film substrate 100, as described above, includes a step of holding the substrate 1 in a heated state for a predetermined period of at least five and at least sixty minutes (step S8). If the period during which the substrate 1 is held in a heated state is too short, the improvement in the dielectric strength of the piezoelectric layer 5 will be insufficient, as it will be difficult to induce element diffusion from the lower matching layer 4 and the upper matching layer 6. If the period during which the substrate 1 is held in a heated state is too long, the properties of the piezoelectric layer 5 will deteriorate due to excessive element substitution caused by element diffusion from the lower matching layer 4 and the upper matching layer 6.In contrast, in this embodiment, the substrate 1 can be kept in a heated state for a predetermined period of at least five and at least sixty minutes. Consequently, the dielectric strength of the piezoelectric layer 5 can be further improved compared to a case where the maintenance time is too short or too long.

[0055] In this embodiment, the method for producing a piezoelectric film substrate 100, as described above, comprises: a step of depositing the piezoelectric layer 5 onto the lower matching layer 4 by sputtering, wherein the substrate 1 is heated to a predetermined deposition temperature using the heating device 12 (step S5). Furthermore, the method for producing a piezoelectric film substrate 100 comprises a step of holding the substrate 1 for a predetermined period, wherein the substrate 1 is heated to a temperature higher than the predetermined deposition temperature during sputtering to deposit the piezoelectric layer 5 (step S8).Since substitution by element diffusion progresses with increasing temperature, the substrate 1 can be maintained at a sufficiently high temperature in a heated state by keeping it at a temperature higher than the predetermined deposition temperature during sputtering to deposit the piezoelectric layer 5 for the predetermined period. Consequently, it is possible to prevent a situation where element diffusion becomes insufficient due to an excessively low heating temperature, thus preventing an inadequate improvement in dielectric strength. (Modified embodiments)

[0056] It is noted that the embodiment disclosed herein is to be regarded in all respects as explanatory and not limiting. The scope of protection of the present invention is not defined by the above description of the embodiments, but rather by the scope of protection defined in the patent claims, and furthermore, all modifications (modified embodiments) within the meaning and scope corresponding to the scope of the patent claims are included.

[0057] While, for example, the aforementioned embodiment shows an example in which the lower adaptation layer 4 and the upper adaptation layer 6 contain strontium and ruthenium or lanthanum and nickel, the present invention is not limited thereto. In the present invention, the lower adaptation layer and the upper adaptation layer can be configured to include metallic elements other than strontium and ruthenium or lanthanum and nickel.

[0058] Furthermore, the lower matching layer does not necessarily have to function to adjust the crystal orientation of the piezoelectric layer. In addition, the lower and upper matching layers can contain different combinations of metallic elements. For example, the lower matching layer can be lanthanum nickel oxide (LaNiO3: LNO), and the upper matching layer can be strontium ruthenate (SrRuO3: SRO). Furthermore, the lower and upper matching layers can be multilayer films.

[0059] Although the aforementioned embodiment shows an example in which the lower electrode layer 3, the lower matching layer 4, the piezoelectric layer 5, the upper matching layer 6, and the upper electrode layer 7 are deposited by sputtering, the present invention is not limited to this. In the present invention, each of the lower electrode layer 3, the lower matching layer 4, the piezoelectric layer 5, the upper matching layer 6, and the upper electrode layer 7 can be formed by a method other than sputtering. For example, the lower electrode layer or the upper electrode layer can be formed by vacuum coating. Furthermore, the piezoelectric layer can be deposited by a method such as PLD (pulsed laser deposition), CVD (chemical vapor deposition), or sol-gel deposition.Furthermore, the lower electrode layer, the lower matching layer, the piezoelectric layer, the upper matching layer, and the upper electrode layer can be formed (deposited) using a common sputtering device. The piezoelectric layer can also be a single crystal or a polycrystal.

[0060] While the aforementioned embodiment showed an example in which a plurality of substrates 1 are held together in a heated state in the heat treatment furnace 103, which is separate from the deposition chamber 13 for depositing the piezoelectric layer 5, the present invention is not limited thereto. In the present invention, the substrates 1 can be held individually in a heated state. In this case, each substrate can be held in a heated state for a predetermined period in a device in which the upper electrode layer has been formed.When forming (depositing) the piezoelectric layer, the top matching layer, and the top electrode layer using a common sputtering device, the substrate can be held in a heated state in the common sputtering device for a predetermined period of time, which deposits the piezoelectric layer after the top electrode layer has been formed.

[0061] Although the aforementioned embodiment showed an example in which the substrate 1 is kept in a heated state for a predetermined period of not less than five minutes and not less than sixty minutes after the formation of the upper electrode layer 7, the present invention is not limited thereto. In the present invention, the substrate can be kept in a heated state for a predetermined period of not less than sixty minutes.

[0062] Although the aforementioned embodiment shows an example in which the predetermined deposition temperature, which is a setting temperature used for deposition of the piezoelectric layer 5, is not lower than 560 °C and not higher than 700 °C, and the substrate 1 is held for a predetermined period, being in a heated state, at a temperature higher than the predetermined deposition temperature for deposition of the piezoelectric layer 5, the present invention is not limited thereto. In the present invention, the deposition temperature used for deposition of the piezoelectric layer can be lower than 560 °C or not lower than 700 °C.Furthermore, after the upper adaptation layer has been formed, the substrate can be kept in a heated state for a predetermined period at a temperature lower than the application set temperature or at the same temperature as the application set temperature.

[0063] Although the aforementioned embodiment shows an example in which the lower electrode layer 3 and the upper electrode layer 7 are formed from a metallic material such as platinum (Pt) or iridium (Ir), the present invention is not limited thereto. In the present invention, the lower electrode layer and the upper electrode layer can be formed from a material containing titanium (Ti) or gold (Au). They can also be formed from cerium oxide (CeO2), a high-temperature copper oxide superconductor (LSCO), lanthanum (La), or strontium (Sr). The lower electrode layer and the upper electrode layer can also be formed from different materials. Description of reference symbols 1 substrate 2 electrically insulating layers 3 lower electrode layer 4 lower adaptation layer 5 piezoelectric layer 5a lower diffusion layer 5b upper diffusion layer 6 upper adaptation layer 7 upper electrode layer 12 Heating device 13th Separation Chamber 100 piezoelectric film substrate 101 Sputtering device 102 Target material 103 Heat treatment furnace QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 6030418 [0002, 0003, 0004]< / sputtervorrichtung>

Claims

A method for producing a piezoelectric film substrate, comprising: forming a lower electrode layer on or over a substrate; forming a lower matching layer having a lower matching element or lower matching elements as a predetermined metal element or metal elements, on or over the lower electrode layer; applying a piezoelectric layer having a lead zirconate titanate with a perovskite structure, on or over the lower matching layer; forming an upper matching layer having an upper matching element or upper matching elements as a predetermined metal element or metal elements, on or over the piezoelectric layer; forming an upper electrode layer on or over the upper matching layer; and holding the substrate for a predetermined period after forming the upper electrode layer, wherein the substrate is in a heated state. Method for producing the piezoelectric film substrate according to claim 1, wherein the application of the piezoelectric layer comprises: applying the piezoelectric layer onto or over the lower adaptation layer formed on or over the substrate which is arranged in a deposition chamber, and the holding of the substrate for the predetermined period comprises: holding the substrate for the predetermined period, wherein the substrate is arranged in a heat treatment furnace separate from the deposition chamber and is in a heated state. Method for producing the piezoelectric film substrate according to claim 2, wherein holding the substrate for the predetermined period comprises: holding a plurality of the substrates together for the predetermined period, wherein the plurality of substrates are arranged in the heat treatment furnace in a heated state. Method for producing the piezoelectric film substrate according to claim 1, wherein forming the lower matching layer comprises: forming the lower matching layer having strontium and ruthenium as the lower matching elements or having lanthanum and nickel as the lower matching elements, for matching the crystal orientation of the piezoelectric layer, and forming the upper matching layer comprises: forming the upper matching layer having strontium and ruthenium as the upper matching elements, or having lanthanum and nickel as the upper matching elements. Method for producing the piezoelectric film substrate according to claim 4, wherein forming the upper matching layer comprises: forming the upper matching layer which has the upper matching elements which are metal elements common to the lower matching elements contained in the lower matching layer, and which has a composition identical to that of the lower matching layer. Method for producing the piezoelectric film substrate according to claim 1, wherein holding the substrate for the predetermined period comprises: holding the substrate in a heated state for not less than five minutes and less than sixty minutes as the predetermined period. Method for producing the piezoelectric film substrate according to claim 1, wherein the application of the piezoelectric layer comprises: applying the piezoelectric layer onto or over the lower matching layer by sputtering, wherein the substrate is heated to a predetermined application setting temperature using a heating device, and the holding of the substrate for the predetermined period comprises: holding the substrate for the predetermined period, wherein the substrate is heated to a temperature higher than the predetermined application setting temperature during sputtering to apply the piezoelectric layer. A piezoelectric film substrate comprising: a lower electrode layer formed on or above a substrate; a lower matching layer formed on or above the lower electrode layer and comprising a lower matching element as a predetermined metal element; a piezoelectric layer applied on or above the lower matching layer comprising lead zirconate titanate with a perovskite structure; an upper matching layer formed on or above the piezoelectric layer and comprising an upper matching element as a predetermined metal element; and an upper electrode layer formed on or above the upper matching layer, wherein the piezoelectric layer comprises: a lower diffusion layer formed along an interface with the lower matching layer, and an upper diffusion layer formed along an interface with the upper matching layer.The lower diffusion layer has a thickness of less than or equal to 10% of the film thickness of the entire piezoelectric layer; at least one element of titanium, zirconium, or lead contained in the piezoelectric layer is substituted in the lower diffusion layer by elemental diffusion with the lower matching element contained in the lower matching layer; the lower diffusion layer has a region where the detection intensity ratio of the lower matching element contained in the lower diffusion layer is 10% or more greater than that in a section of the piezoelectric layer that is not the upper diffusion layer and the lower diffusion layer; the upper diffusion layer has a thickness of less than or equal to 10% of the film thickness of the entire piezoelectric layer; at least one element of titanium, zirconium, or lead contained in the piezoelectric layer.in the upper diffusion layer is substituted by element diffusion with the upper matching element contained in the upper matching layer, and the upper diffusion layer has a region in which a detection intensity ratio of the upper matching element contained in the upper diffusion layer is 10% or more greater than that in the section of the piezoelectric layer that is not the upper diffusion layer and the lower diffusion layer in the piezoelectric layer.

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