Membrane structure, method for manufacturing membrane structure, and apparatus for manufacturing membrane structure

Abstract

The present invention provides a film structure (10) which sequentially comprises a substrate (1), a film (2) containing zirconia, a sacrificial layer (3) and a piezoelectric film (4) in this order, wherein: the substrate, the film containing zirconia, the sacrificial layer and the piezoelectric film are respectively single-crystallized; and the sacrificial layer can be selectively removed. The present invention also provides: a method for producing this film structure; and an apparatus for producing this film structure.

Description

Technical Field

[0001] The present invention relates to a film structure, a method for manufacturing a film structure, and a manufacturing apparatus for a film structure.

Background Art

[0002] In the current era of the Internet of Things (IoT) where all kinds of things are connected to the Internet, sensors play an important role. In particular, efforts in MEMS (Micro Electro Mechanical Systems) sensor technology using piezoelectric materials such as lead zirconate titanate (PZT) are in full swing, and their applications are spreading to various fields such as gyro sensors for autonomous driving, piezoelectric microphones, high-frequency filters for 5G communication, and vibration power generation elements. With the development of IoT technology, MEMS sensor technology using such piezoelectric materials has been required to be smaller, thinner, and more sensitive year by year, and a technology for obtaining a piezoelectric material as a thin-film single crystal by epitaxial growth has been proposed. For example, Patent Document 1 discloses a film structure including a substrate, a buffer film having a cubic crystal structure containing zirconia formed on the substrate, a metal film containing an epitaxially grown platinum group element formed on the buffer film, and a film containing Sr(Ti 1-x ,Ru x )O3 (0 ≦ x ≦ 1) formed on the metal film. Further disclosed is a film structure in which a single-crystalline piezoelectric film and a conductive film are further formed on the epitaxially grown film containing Sr(Ti 1-x ,Ru x )O3.

[0003] In addition, as a device using a piezoelectric film, a Film Bulk Acoustic Resonator (FBAR) is known. An FBAR generally has a lower electrode, a piezoelectric film, and an upper electrode in this order on a substrate, and an air gap is formed under the lower electrode. For example, as described in Patent Document 2, the air gap is formed by etching the substrate from the back surface or etching a sacrificial layer provided on the surface of the substrate. However, it is difficult to improve the crystallinity of the piezoelectric film formed on the lower electrode of the FBAR. For this reason, for example, Patent Document 3 discloses a method of epitaxially growing a piezoelectric film on a different substrate and transferring it onto a substrate on which an air gap is formed to form a piezoelectric film with excellent crystallinity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] As in Patent Document 1, by making each film such as a piezoelectric film included in the film structure into a single crystal, the characteristics as a device are improved. However, there is no known film structure that has an air gap between the substrate and the electrode film and in which each film included in the film structure is single-crystallized.

[0006] An object of the present invention is to provide a film structure that can be used for manufacturing a film structure in which each film is single-crystallized and there is an air gap between the substrate and the electrode film. Furthermore, an object of the present invention is to provide a method for manufacturing the film structure and an apparatus for manufacturing the film structure.

Means for Solving the Problem

[0007] As a result of intensive studies, the present inventors have found that the above problems can be solved by the means shown below.

[0008] [1] A film structure having a substrate, a film containing zirconia, a sacrificial layer, and a piezoelectric film in this order, wherein the substrate, the film containing zirconia, the sacrificial layer, and the piezoelectric film are each single-crystallized, and the sacrificial layer can be selectively removed. [2] Furthermore, the film structure according to [1], which has an electrode film between the piezoelectric film and the sacrificial layer. [3] The film structure according to [1] or [2], wherein the piezoelectric film contains at least one selected from the group consisting of lead zirconate titanate, barium titanate, bismuth ferrite, aluminum nitride, lithium niobate, potassium sodium niobate, and lithium tantalate. [4] The film structure according to [2], wherein the electrode film is single-crystallized. [5] The film structure according to any one of [1] to [4], wherein the sacrificial layer contains at least one selected from the group consisting of strontium ruthenate, magnesium oxide, strontium titanate, chromium, gold, and titanium. [6] The film structure according to [2] or [4], wherein the electrode film contains at least one selected from the group consisting of platinum, copper, ruthenium, rhodium, palladium, osmium, molybdenum, and iridium. [7] The film structure according to [2], [4] or [6], wherein the electrode film is thicker than the sacrificial layer. [8] The film structure according to any one of [1] to [7], wherein the thickness of the sacrificial layer is 10 to 70 nm. [9] Furthermore, a film structure according to any one of [1] to [8], having a second electrode film between the film containing zirconia and the sacrificial layer.

[10] The film structure according to [9], wherein the second electrode film is single-crystallized.

[11] A method for manufacturing a film structure according to any one of [1] to

[10] , comprising: a step of preparing a substrate; a step of forming a film containing zirconia, a sacrificial layer, and a piezoelectric film on the substrate in this order; having a method for manufacturing a film structure, wherein the deposition temperature of the sacrificial layer is 565 to 665 °C.

[12] An apparatus for manufacturing a film structure according to any one of [1] to

[10] , comprising: a film forming apparatus A for forming a film containing zirconia, a film forming apparatus B for forming a sacrificial layer, and a film forming apparatus C for forming a piezoelectric film; a manufacturing apparatus for a film structure, comprising a control unit for controlling the film forming apparatus A, the film forming apparatus B, and the film forming apparatus C.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a film structure in which each film is single-crystallized and which can be used for manufacturing a film structure having a gap between a substrate and an electrode film. Furthermore, according to the present invention, it is possible to provide a method for manufacturing the above film structure and an apparatus for manufacturing the above film structure.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited thereto. Note that the disclosure in this specification is merely an example of an embodiment of the present invention, and those that can be easily conceived by those skilled in the art with appropriate modifications while maintaining the gist of the invention are naturally included in the scope of the present invention. In addition, for the purpose of making the explanation clearer, the drawings may schematically show the width, thickness, shape, etc. of each part compared with the embodiments, but this is merely an example and does not limit the interpretation of the present invention. In this specification and each drawing, elements similar to those described above with respect to the already shown drawings may be given the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0012] <Film structure> The film structure of the present invention has a substrate, a film containing zirconia, a sacrificial layer, and a piezoelectric film in this order, the substrate, the film containing zirconia, the sacrificial layer, and the piezoelectric film are each single-crystallized, and is a film structure capable of selectively removing the sacrificial layer.

[0013] Figure 1 is a cross-sectional view of an example of the film structure of the present invention. The film structure 10 in Figure 1 has a substrate 1, a film 2 containing zirconia, a sacrificial layer 3, and a piezoelectric film 4 in this order. The substrate 1, the film 2 containing zirconia, the sacrificial layer 3, and the piezoelectric film 4 are each single-crystallized. In Figure 1, the substrate 1 and the film 2 containing zirconia are in contact. The film structure of the present invention may have another film between the substrate and the film containing zirconia, but it is preferable that the substrate and the film containing zirconia are in contact (without having another film therebetween). In Figure 1, the sacrificial layer 3 and the piezoelectric film 4 are in contact. The film structure of the present invention may have another film between the sacrificial layer and the piezoelectric film. For example, it may have an electrode film (also referred to as the "first electrode film") between the sacrificial layer and the piezoelectric film. In Figure 1, the film 2 containing zirconia and the sacrificial layer 3 are in contact. The film structure of the present invention may have another film between the film containing zirconia and the sacrificial layer. For example, it may have an electrode film (also referred to as the "second electrode film") between the film containing zirconia and the sacrificial layer.

[0014] The film structure of the present invention has a substrate, a film containing zirconia, a sacrificial layer, and a piezoelectric film in this order, but in addition to these, it may have other films. Figure 2 is a cross-sectional view of an example of the film structure of the present invention. The film structure 11 in Figure 2 is the same as the film structure 10 in Figure 1 except that it has an electrode film (first electrode film) 5 between the piezoelectric film 4 and the sacrificial layer 3. The electrode film 5 is preferably crystallized.

[0015] Figure 3 is a cross-sectional view of an example of the film structure of the present invention. The film structure 12 in Figure 3 is the same as the film structure 11 in Figure 2 except that it has a second electrode film 6 between the film 2 containing zirconia and the sacrificial layer 3. The second electrode film 6 is preferably crystallized.

[0016] The sacrificial layer 3 can be selectively removed. When the sacrificial layer 3 of the film structure 11 in FIG. 2 is selectively removed, the film structure 21 in FIG. 4 is obtained. The film structure 21 has a void 3a formed by selectively removing the sacrificial layer 3. When the sacrificial layer 3 of the film structure 12 in FIG. 3 is selectively removed, the film structure 22 in FIG. 5 is obtained. The film structure 22 has a void 3a formed by selectively removing the sacrificial layer 3. Note that the laminate of the piezoelectric film 4 and the electrode film 5 in FIGS. 4 and 5 may be supported by a portion not shown.

[0017] (Substrate) The substrate is, for example, a silicon substrate made of a single crystal of silicon (Si). In addition to Si, for example, an SOI (Silicon on Insulator) substrate, a substrate made of various semiconductor crystals other than Si, a substrate made of various oxide single crystals such as sapphire, garnet (Al3Fe2Si3O 12 ) substrate, or a glass substrate having a polysilicon film formed on its surface may also be used. The substrate is single-crystallized. That the substrate is single-crystallized means that the main component (the component with the highest content rate) constituting the substrate is a single crystal. The orientation of the substrate may be any, and in the case of an Si substrate, for example, Si(100), Si(110), Si(111), etc. can be mentioned.

[0018] The size of the substrate is not particularly limited, and it may be 4 inches, or may be 6 inches or 8 inches. The thickness of the substrate is not particularly limited.

[0019] (Film containing zirconia) The film containing zirconia (hereinafter also referred to as "zirconia film") typically contains zirconia (ZrO2) epitaxially grown on the substrate. The zirconia film is single-crystallized. That the zirconia film is single-crystallized means that the zirconia contained in the zirconia film is a single crystal. It is known that zirconia undergoes a phase transition in the crystal system from monoclinic to tetragonal to cubic with the addition of energy, but in the present invention, any crystal structure may be used.

[0020] The thickness of the zirconia film is not particularly limited, but it is preferably 5 to 40 nm, and more preferably 10 to 30 nm. The zirconia film may be a flat film or may be composed of a flat portion and a protruding portion. The shape of the protruding portion is not particularly limited, and examples include a pyramid structure (in this case, it is preferable that the bottom surface of the pyramid structure is in contact with the flat portion). When the zirconia film is composed of a flat portion and a protruding portion, the thickness of the flat portion is not particularly limited, but it is preferably 5 to 25 nm, and more preferably 10 to 20 nm. The height of the protruding portion (the distance from the flat portion to the apex of the protruding portion) is not particularly limited, but it is preferably 3 to 10 nm, and more preferably 4 to 8 nm.

[0021] In addition to zirconia, the zirconia film may contain other components (for example, rare earth elements or alkaline earth elements). Zirconia may contain oxygen defects. Also, for property improvement, it may contain transition metal elements such as Al, Sc, Mn, Fe, Co, Ni, etc.

[0022] (sacrificial layer) The sacrificial layer is a film that can be selectively removed. For example, it is preferably a film that can be selectively removed by an etchant, and more preferably a film that can be selectively removed by a liquid etchant. By selectively removing the sacrificial layer of the film structure of the present invention, a film structure in which each film is single-crystallized can be obtained. The sacrificial layer preferably contains at least one selected from the group consisting of strontium ruthenate (SRO), magnesium oxide (MgO), strontium titanate, chromium, gold, and titanium. The sacrificial layer preferably contains strontium ruthenate (SRO), magnesium oxide (MgO), strontium titanate, chromium, gold, and titanium, which typically grow epitaxially on the zirconia film or the second electrode film. The sacrificial layer is single-crystallized. The fact that the sacrificial layer is single-crystallized means that the main component (the component with the highest content rate) constituting the sacrificial layer is a single crystal. The crystal structure of the single crystal of the sacrificial layer is not particularly limited. The thickness of the sacrificial layer is not particularly limited, but is preferably 10 to 70 nm, and more preferably 20 to 60 nm. When the thickness of the sacrificial layer is 10 nm or more, it is easy to selectively remove the sacrificial layer using an etchant. When the thickness of the sacrificial layer is 70 nm or less, the first electrode film formed on the sacrificial layer can be efficiently single-crystallized. Also, when a piezoelectric film is further formed on the first electrode film, the piezoelectric film can be efficiently single-crystallized.

[0023] (Piezoelectric film) The piezoelectric film preferably contains at least one selected from the group consisting of lead zirconate titanate (PZT), barium titanate (BaTiO3), bismuth ferrite (BiFeO3), aluminum nitride (AlN), lithium niobate (LiNbO3), potassium sodium niobate, and lithium tantalate (LiTaO3). The piezoelectric film preferably contains components that typically grow epitaxially on the first electrode film. The piezoelectric film is preferably single-crystallized. The fact that the piezoelectric film is single-crystallized means that the main component (the component with the highest content rate) constituting the piezoelectric film is a single crystal. The crystal structure of the single crystal of the piezoelectric film is not particularly limited. For example, lead zirconate titanate (PZT), barium titanate (BaTiO3), and potassium sodium niobate may have a perovskite structure. Bismuth ferrite (BiFeO3), lithium niobate (LiNbO3), and lithium tantalate (LiTaO3) may have a trigonal crystal system. Aluminum nitride (AlN) may have a hexagonal crystal system.

[0024] (First electrode film) The membrane structure of the present invention may have a first electrode film between the piezoelectric film and the sacrificial layer. The first electrode film preferably contains a metal, and more preferably contains at least one selected from the group consisting of platinum, copper, ruthenium, rhodium, palladium, osmium, molybdenum, and iridium. Typically, the first electrode film preferably contains a metal epitaxially grown on the sacrificial layer. The first electrode film is preferably single-crystallized. That the first electrode film is single-crystallized means that the main component (the component with the highest content rate) constituting the first electrode film is a single crystal. The crystal structure of the single crystal of the first electrode film is not particularly limited. The thickness of the first electrode film is not particularly limited, but is preferably 30 to 500 nm, more preferably 50 to 450 nm, and still more preferably 100 to 400 nm. The first electrode film is preferably thicker than the sacrificial layer.

[0025] (Second Electrode Film) The membrane structure of the present invention may have a second electrode film between the film containing zirconia and the sacrificial layer. The second electrode film preferably contains a metal, and more preferably contains at least one selected from the group consisting of platinum, copper, ruthenium, rhodium, palladium, osmium, molybdenum, and iridium. Typically, the second electrode film preferably contains a metal epitaxially grown on the film containing zirconia. The second electrode film is preferably single-crystallized. That the second electrode film is single-crystallized means that the main component (the component with the highest content rate) constituting the second electrode film is a single crystal. The crystal structure of the single crystal of the second electrode film is not particularly limited. The thickness of the second electrode film is not particularly limited, but is preferably 30 to 500 nm, more preferably 50 to 450 nm, and still more preferably 100 to 400 nm.

[0026] <Method for Manufacturing Membrane Structure> The manufacturing method of the film structure of the present invention is not particularly limited, but a step of preparing a substrate, and a step of forming a film containing zirconia, a sacrificial layer, and a piezoelectric film on the substrate in this order, is preferably included. Each film is preferably formed by a vapor deposition method or a sputtering method.

[0027] The film formation temperature of the sacrificial layer is preferably 565 to 665 °C. By setting the film formation temperature of the sacrificial layer within the above range, the piezoelectric film formed on the sacrificial layer can be efficiently single-crystallized. Also, when forming the first electrode film on the sacrificial layer, the first electrode film and the piezoelectric film formed thereon can be efficiently single-crystallized.

[0028] The film formation temperature of the first electrode film is preferably 300 to 700 °C, more preferably 450 to 700 °C, and particularly preferably 600 to 700 °C. By setting the film formation temperature of the first electrode film within the above range, when forming the piezoelectric film on the first electrode film, the piezoelectric film can be efficiently single-crystallized.

[0029] <Manufacturing apparatus for film structure> The manufacturing apparatus for the film structure of the present invention is not particularly limited, but preferably includes a film forming apparatus A for forming a film containing zirconia, a film forming apparatus B for forming a sacrificial layer, and a film forming apparatus C for forming a piezoelectric film, and a control unit for controlling the film forming apparatus A, the film forming apparatus B, and the film forming apparatus C. The film forming apparatus A, the film forming apparatus B, and the film forming apparatus C are apparatuses for forming each film by a vapor deposition method or a sputtering method. The control unit preferably includes a computer. The computer is equipped with a CPU, a RAM, a ROM, a hard disk drive, etc., and executes programs such as film forming processes to control the film forming apparatus A, the film forming apparatus B, and the film forming apparatus C. The manufacturing apparatus of the film structure of the present invention may further include at least one of a film-forming apparatus D for forming a first electrode film and a film-forming apparatus E for forming a second electrode film. The film-forming apparatus D and the film-forming apparatus E are preferably apparatuses for forming each film by a vapor deposition method or a sputtering method. The control unit preferably further controls the film-forming apparatus D and the film-forming apparatus E.

Examples

[0030] Hereinafter, the present invention will be specifically described using examples, but the present invention is not limited thereto.

[0031] In Examples 1 to 29 and Comparative Examples 1 to 6, the film structure 12 having the configuration shown in FIG. 3 was manufactured. As the substrate 1, a wafer made of a 6-inch single crystal silicon was used.

[0032] (Example 1) On the substrate 1, a zirconia film 2 was formed by an electron beam evaporation method. Next, on the zirconia film 2, a platinum (Pt) film was formed as the second electrode film 6 by a sputtering method. Next, on the second electrode film 6, an SRO film was formed as the sacrificial layer 3 by a sputtering method. The film formation temperature of the sacrificial layer 3 was 665°C. The thickness of the sacrificial layer 3 was 10 nm. Next, on the sacrificial layer 3, a platinum (Pt) film was formed as the electrode film (first electrode film) 5 by a sputtering method. The film formation temperature of the first electrode film 5 was 700°C. The thickness of the first electrode film 5 was 50 nm. Next, on the electrode film (first electrode film) 5, an AlN film was formed as the piezoelectric film 4 by a sputtering method. The formation of each film was performed with reference to the description of the examples in Japanese Patent No. 6498821.

[0033] In this way, the film structure of Example 1 was manufactured.

[0034] (Examples 2 to 18, Comparative Examples 1 to 6) Except for changing the thickness of the sacrificial layer 3 and the thickness of the first electrode film 5 to the values shown in Table 1 below, the film structures of Examples 2 to 18 and Comparative Examples 1 to 6 were produced in the same manner as in Example 1.

[0035] [Table 1]

[0036] (Examples 19 to 29) Except for changing the film formation temperature of the sacrificial layer 3 and the film formation temperature of the first electrode film 5 to the values shown in Table 2 below, and changing the thickness of the sacrificial layer 3 and the thickness of the first electrode film 5 as follows, the film structures of Examples 19 to 29 and Comparative Example 7 were produced in the same manner as in Example 1. Example 19: Thickness of sacrificial layer 40 nm, thickness of first electrode film 150 nm Example 20: Thickness of sacrificial layer 10 nm, thickness of first electrode film 150 nm Example 21: Thickness of sacrificial layer 10 nm, thickness of first electrode film 150 nm Example 22: Thickness of sacrificial layer 10 nm, thickness of first electrode film 150 nm Example 23: Thickness of sacrificial layer 40 nm, thickness of first electrode film 150 nm Example 24: Thickness of sacrificial layer 10 nm, thickness of first electrode film 150 nm Example 25: Thickness of sacrificial layer 10 nm, thickness of first electrode film 150 nm Example 26: Thickness of sacrificial layer 10 nm, thickness of first electrode film 150 nm Example 27: Thickness of sacrificial layer 10 nm, thickness of first electrode film 150 nm Example 28: Thickness of sacrificial layer 10 nm, thickness of first electrode film 150 nm Example 29: Thickness of sacrificial layer 10 nm, thickness of first electrode film 150 nm

[0037] [Table 2]

[0038] <Evaluation of crystallinity> (θ-2θ spectrum by XRD method) Graphs showing the θ-2θ spectra of the film structure of Example 1 by XRD method are shown in FIGS. 6 and 7. In FIG. 6, a peak corresponding to the (002) plane of AlN having a hexagonal crystal structure was observed, and in FIG. 7, a peak corresponding to the (200) plane of Pt having a cubic crystal structure was observed. Graphs showing the θ-2θ spectra of the film structure of Comparative Example 4 by XRD method are shown in FIGS. 8 and 9. In FIG. 8, the peak of AlN (002) was weaker than that of Example 1. When the peak of AlN (002) is weak, it can be said that the abundance ratio of AlN (002) is low and the crystallinity is low (many are not crystallized). Also, in FIG. 9, a peak of Pt (111) was observed, and since two peaks were observed, crystals are mixed and it cannot be said to be a single crystal. From the above, it was found that Example 1 has a better crystal structure than Comparative Example 4. When the θ-2θ spectra by XRD method were measured for Examples 2 to 29 and Comparative Examples 1 to 3, the results were the same as those of Example 1. When the θ-2θ spectra by XRD method were measured for Comparative Examples 5 and 6, the results were the same as those of Comparative Example 4.

[0039] (X-ray diffraction pattern by Φ scan) The X-ray diffraction pattern by Φ scan of the piezoelectric film of the film structure of Example 1 is shown in FIG. 10. From FIG. 10, it was found that the piezoelectric film of the film structure of Example 1 was single-crystallized. When the X-ray diffraction patterns by Φ scan of the piezoelectric films were measured for Examples 2 to 29 and Comparative Examples 1 to 3, the results were the same as those of Example 1. In Examples 1 to 29 and Comparative Examples 1 to 3, the substrates and all the films included in the film structure were single-crystallized. When the X-ray diffraction patterns by Φ scan of the piezoelectric films were measured for Comparative Examples 4 to 6, it was found that they were not single-crystallized.

[0040] (Evaluation of whether the sacrificial layer can be selectively removed (selective removal of the sacrificial layer)) Using an aqueous cerium nitrate solution as an etchant, attempts were made to selectively remove the sacrificial layers of the film structures of Examples 1 to 29 and Comparative Examples 1 to 6. The side etching rate (μm / min) was measured. The relationship between the thickness of the sacrificial layer and the side etching rate (μm / min) is shown in Table 3 below. In Table 3, "-" indicates that removal was not possible.

[0041]

Table 3

[0042] From Table 3, it was found that when the thickness of the sacrificial layer was 10 nm or more (Examples 1 to 29 and Comparative Examples 4 to 6), the side etching rate was good and selective removal was possible. When the thickness of the sacrificial layer was 5 nm (Comparative Examples 1 to 3), the side etching rate was small and it was found that the sacrificial layer could not be selectively removed.

[0043] The above results are summarized in Table 4 below. 〇 indicates that the result is good, △ indicates that it is inferior to 〇 but within the acceptable range, and × indicates that it is bad.

[0044]

Table 4

Industrial Applicability

[0045] The film structure of the present invention is a film structure having a gap between a substrate and an electrode film, and since each film contained in the film structure is single-crystallized, it can be used as various MEMS such as FBAR.

Explanation of Signs

[0046] 1: Substrate 2: Film containing zirconia 3: Sacrificial layer 4: Piezoelectric film 5: Electrode film 6: Second electrode film 3a: Gap 10, 11, 12: Membrane structure 21, 22: Membrane structure with voids

Claims

1. A film structure having a substrate, a film containing zirconia, a sacrificial layer, and a piezoelectric film in this order, wherein the substrate, the film containing zirconia, the sacrificial layer, and the piezoelectric film are each single-crystallized, the sacrificial layer can be selectively removed, and the sacrificial layer contains at least one selected from the group consisting of strontium ruthenate, magnesium oxide, strontium titanate, chromium, gold, and titanium.

2. The film structure according to claim 1, further comprising an electrode film between the piezoelectric film and the sacrificial layer.

3. The film structure according to claim 1 or 2, wherein the piezoelectric film contains at least one selected from the group consisting of lead zirconate titanate, barium titanate, bismuth ferrite, aluminum nitride, lithium niobate, potassium sodium niobate, and lithium tantalate.

4. The film structure according to claim 2, wherein the electrode film is single-crystallized.

5. The film structure according to claim 2 or 4, wherein the electrode film contains at least one selected from the group consisting of platinum, copper, ruthenium, rhodium, palladium, osmium, molybdenum, and iridium.

6. The film structure according to claim 2, 4, or 5, wherein the electrode film is thicker than the sacrificial layer.

7. The film structure according to any one of claims 1 to 6, wherein the thickness of the sacrificial layer is 10 to 70 nm.

8. The film structure according to any one of claims 1 to 7, further comprising a second electrode film between the film containing zirconia and the sacrificial layer.

9. The film structure according to claim 8, wherein the second electrode film is single-crystallized.

10. A method for manufacturing the film structure according to any one of claims 1 to 9, comprising: a step of preparing a substrate; a step of forming a film containing zirconia, a sacrificial layer, and a piezoelectric film in this order on the substrate. The method for manufacturing a film structure, wherein the film formation temperature of the sacrificial layer is 565 to 665 °C.

11. An apparatus for manufacturing the film structure according to any one of claims 1 to 9, comprising: [[ID=2�]]a film forming apparatus A for forming a film containing zirconia, a film forming apparatus B for forming a sacrificial layer, and a film forming apparatus C for forming a piezoelectric film, and a control unit for controlling the film forming apparatus A, the film forming apparatus B, and the film forming apparatus C. ​

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