Laminated structure, and device for use and manufacturing thereof

Abstract

Provided is a laminated structure in which epitaxial growth of a functional thin film can be achieved, problems such as interlayer peeling can be suppressed, and crack progression of the functional thin film can be suppressed. This laminated structure is provided with: a substrate, at least the surface of which is composed of a single crystal; a crystalline orientation control film that contains zirconium oxide (ZrO2) as a main component provided on the single crystal surface of the substrate; and a functional thin film provided on the crystalline orientation control film. The liquid crystal display device is further provided with a buffer layer containing a mixed phase of a crystalline phase and an amorphous phase, and the buffer layer is interposed between the substrate and the orientation control film. In addition, the crack penetration degree is 80% or less as determined by the ratio of the depth of the crack in the vertical direction to the film thickness of the functional film.

Description

TECHNICAL FIELD

[0001] The present application relates to a laminated structure, and a device for use and manufacture thereof. BACKGROUND

[0002] MEMS (Micro Electro Mechanical Systems) is a device configured of a laminated structure in which mechanical components, electronic circuits are integrated on a substrate such as a silicon substrate by microfabrication technology. By forming a functional thin film such as a piezoelectric film on a substrate using the MEMS technology, a small and integrated device such as a sensor, an actuator can be produced.

[0003] The characteristics of the functional thin film such as a piezoelectric film vary depending on the crystallinity and orientation of the thin film. Therefore, in order to obtain a high characteristic device, it is effective to control the crystallinity and orientation by epitaxial growth of the functional thin film. However, generally, the lattice of the functional thin film does not match the lattice of the substrate. Therefore, it is difficult to epitaxially grow the functional thin film on the substrate in a state of being kept unchanged.

[0004] In order to solve such a problem, a technology of providing an orientation control film (buffer film) such as a ZrO2 film between the substrate and the functional thin film of the laminated structure has been proposed. By providing the orientation control film, lattice mismatch can be suppressed, and stable epitaxial growth of the functional thin film can be achieved.

[0005] As a document disclosing such a technology, Patent Documents 1 to 3 are cited. In Patent Document 1, a structure in which a thin film of PZT is formed on a buffer layer formed by sequentially stacking a film of YSZ (8% Y2O3 + 92% ZrO2), CeO2, LaSrCoO3 on a silicon substrate (Si) in advance is disclosed (Patent Document 1,

[0035] to

[0037] , etc.). In Patent Document 2, a structure in which a ZrO2 film is formed on a Si substrate by a vapor deposition method, and a lower electrode, a PbZrO2 film (PZO film), and a Pb(Zr 1-x Ti x )O3 film (PZT film) are sequentially formed on the ZrO2 film is disclosed (Patent Document 2,

[0023] to

[0039] , etc.).

[0006] In Patent Document 3, the following is disclosed: In a film structure having a substrate 11, an orientation film 12, a conductive film 13, a conductive film 14, and a piezoelectric film 15, since the orientation film 12 contains zirconia (ZrO2), the orientation film 12 is epitaxially grown on the substrate 11, the conductive film 13 is epitaxially grown on the orientation film 12, and therefore, the conductive film 14 can be epitaxially grown on the conductive film 13, and further, the piezoelectric film 15 can be epitaxially grown on the conductive film 14 (Patent Document 3,

[0035] to

[0041] , etc.).

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2014-084494

[0010] Patent Document 2: International Publication No. 2016 / 009698

[0011] Patent Document 3: Japanese Patent Application Publication No. 2018-081974 SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] Thus, although it has been proposed to produce a layered structure body having an orientation control film using MEMS technology, the conventional layered structure body has room for improvement. That is, although the lattice mismatch between the substrate and the functional thin film is suppressed to some extent by using the orientation control film, it is not completely eliminated. On the other hand, since the functional thin film is epitaxially grown, the problem of lattice mismatch and film stress resulting therefrom cannot be ignored. That is, although a film with high crystallinity is obtained by stabilizing the epitaxial growth, since the crystallinity of each film becomes high, the difference in lattice constant is significantly expressed, which causes a large film stress.

[0014] When such a film stress remains after being generated, the interlayer adhesion of each layer constituting the layered structure body decreases, and film peeling sometimes occurs. In addition, even if film peeling does not occur, the characteristics of the functional thin film can deteriorate. This problem is particularly significant in the case where a single-crystal substrate such as a silicon (Si) substrate or a sapphire (Al2O3) substrate is used. This is because, since the single-crystal substrate has high crystallinity, the problem of lattice mismatch is easily caused.

[0015] The present inventors have conducted intensive research in view of such a problem. As a result, the following insight has been obtained: in a layered structure body having a specific substrate, a crystallinity orientation control film, and a functional thin film, by interposing a buffer layer containing a mixed phase of a crystal phase and an amorphous phase between the substrate and the orientation control film, epitaxial growth of a functional thin film with high crystallinity can be achieved, and problems such as interlayer peeling can be suppressed.

[0016] The present inventors have further conducted research, and as a result, the following insight has been obtained: at the time of layered structure body production, by providing a prescribed maturation process after the film formation of the crystallinity orientation control film, the progress of cracks of the functional thin film provided on the crystallinity orientation control film can be suppressed.

[0017] The present application has been achieved based on the insight that it is an object to provide a layered structure capable of realizing epitaxial growth of a functional thin film while suppressing problems such as interlayer peeling and suppressing the progress of cracks in the functional thin film, and a device for use and manufacture thereof.

[0018] Means for solving the problem

[0019] The present application includes the following (1) to (9). Note that in this specification, the expression "to" includes both numerical values. That is, "X to Y" has the same meaning as "X or more and Y or less". In addition, in this specification, any combination of preferred embodiments can be adopted as long as technical matching is achieved. For example, one side and the other side of a preferred numerical range can be arbitrarily combined. Furthermore, in this specification, the expression "above A" includes the concept of "the upper portion of A separated from A" as well as "directly above A" unless otherwise noted. That is, the expression "providing B above A" includes not only the manner of "directly providing B above A", but also the manner of "sandwiching other members (layers, films, etc.) between A and B".

[0020] (1) A layered structure, wherein

[0021] The layered structure includes:

[0022] a substrate whose at least a surface is composed of a single crystal;

[0023] a crystal orientation control film including zirconium oxide (ZrO2) as a main component provided on a single-crystal surface of the substrate; and

[0024] a functional thin film provided on the crystal orientation control film,

[0025] the layered structure further includes a buffer layer including a mixed phase of a crystal phase and an amorphous phase, the buffer layer being interposed between the substrate and the orientation control film,

[0026] a crack penetration degree defined by a ratio of a vertical direction depth of a crack to a film thickness of the functional thin film is 80% or less.

[0027] (2) The layered structure according to the above (1), wherein

[0028] the substrate is a single-crystal Si substrate, an SOI substrate, a stainless steel (SUS) substrate, a quartz glass substrate, a single-crystal gallium nitride (GaN) substrate, a single-crystal silicon carbide (SiC) substrate, or a sapphire substrate provided with a single-crystal gallium nitride (GaN) on a surface.

[0029] (3) The layered structure according to the above (1) or (2), wherein

[0030] The buffer layer contains zirconium oxide (ZrO2) as a main component.

[0031] (4) The layered structure according to any one of the above (1) to (3), wherein

[0032] The thickness of the buffer layer is 2 nm or more and 10 nm or less.

[0033] (5) The layered structure according to any one of the above (1) to (4), wherein

[0034] The layered structure further has a first electrode layer interposed between the orientation control film and the functional thin film, and a second electrode layer provided on the functional thin film.

[0035] (6) The layered structure according to the above (5), wherein

[0036] The first electrode layer is a single-crystal film.

[0037] (7) The layered structure according to any one of the above (1) to (6), wherein

[0038] The functional thin film is a single-crystal film.

[0039] (8) The layered structure according to any one of the above (1) to (7), wherein

[0040] The functional thin film is a piezoelectric film, and the layered structure is a piezoelectric device.

[0041] (9) The layered structure according to the above (8), wherein

[0042] The piezoelectric film contains at least one compound selected from the group consisting of Pb(Zr,Ti)O3, BaTiO3, (Pb,La)(Zr,Ti)O3, LiNbO3, LiTaO3, (K,Na)NbO3, AlN, and ZnO as a main component.

[0043] (10) Use of the layered structure according to the above (1) or (2) for a piezoelectric device.

[0044] (11) An apparatus for manufacturing a layered structure, the layered structure being the layered structure according to the above (1) or (2), wherein

[0045] The apparatus for manufacturing the layered structure has a vacuum transfer apparatus, and has a multi chamber having a vacuum evaporation apparatus and a spattering apparatus.

[0046] Effects of the Invention

[0047] According to the present application, there are provided a layered structure capable of realizing epitaxial growth of a functional thin film while suppressing problems such as interlayer peeling and suppressing progress of cracks in the functional thin film, and a device using and manufacturing the same. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 A cross-sectional schematic view of a layered structure is shown.

[0049] Figure 2-1 A cross-sectional TEM image of a layered structure (Example Al) is shown.

[0050] Figure 2-2 A cross-sectional TEM image of a layered structure (Example Al) is shown.

[0051] Figure 3-1 A cross-sectional TEM image of a layered structure (Example A2) is shown.

[0052] Figure 3-2 A cross-sectional TEM image of a layered structure (Example A2) is shown.

[0053] Figure 4 A cross-sectional TEM image of a layered structure (Example A3) is shown.

[0054] Figure 5 A cross-sectional SEM image and a cross-sectional TEM image of a piezoelectric device (Example Bl) are shown.

[0055] Figure 6 A cross-sectional SEM image and a cross-sectional TEM image of a piezoelectric device (Example B2) are shown.

[0056] Figure 7 A cross-sectional SEM image and a cross-sectional TEM image of a piezoelectric device (Example B3) are shown.

[0057] Figure 8 A cross-sectional SEM image and a cross-sectional TEM image of a piezoelectric device (Example B4) are shown.

[0058] Figure 9 An XRD spectrum (ω-2θ scan) of a piezoelectric device (Example B3) is shown.

[0059] Figure 10 An XRD spectrum (Φ scan) of an AlN film (Example B3) is shown.

[0060] Figure 11 An XRD spectrum (Φ scan) of a Pt film (Example Bl) is shown.

[0061] Figure 12 An XRD spectrum (Φ scan) of a PZT film (Example Bl) is shown.

[0062] Figure 13 A cross-sectional SEM image of a piezoelectric device (Example Cl) is shown.

[0063] Figure 14 A cross-sectional SEM image of a piezoelectric device (Example C2) is shown. DETAILED DESCRIPTION

[0064] A specific embodiment of the present application (hereinafter referred to as "the present embodiment") will be described below. However, the present application is not limited to the following embodiment, and various modifications can be made within the scope of the gist of the present application.

[0065] <<1. Laminated structure>>

[0066] The laminated structure of the present embodiment has a substrate whose surface is composed of a single crystal, a crystal orientation control film containing zirconium oxide (Zr02) provided on the single crystal surface of the substrate as a main component, and a functional thin film provided on the crystal orientation control film. The laminated structure also has a buffer layer containing a mixed phase of a crystal phase and an amorphous phase, which is interposed between the substrate and the orientation control film. The crack penetration degree defined by the ratio of the vertical direction depth of a crack to the film thickness of the functional thin film is 80% or less.

[0067] Figure 1 An example of a cross-sectional schematic diagram of a laminated structure is shown. The laminated structure (100) has at least a substrate (2), a buffer layer (4) provided on the substrate (2), an orientation control film (6) provided on the buffer layer (4), and a functional thin film (12) provided on the orientation control film (6). The laminated structure (100) can also have a first electrode layer (8), a first metal oxide film (10) between the orientation control film (6) and the functional thin film (12). The laminated structure (100) can also have a second metal oxide film (14), a second electrode layer (16) on the functional thin film (12). In addition, the functional thin film (100) can also have a take-out electrode (18), a protective film (20), and / or a hollow portion (22).

[0068] <Substrate>

[0069] The substrate functions as a base of the laminated structure. As the substrate, a substrate whose surface is composed of a single crystal is used. By using such a substrate, epitaxial growth and single crystallization of the functional thin film such as an electrode layer, a piezoelectric film, and the like provided thereon can be promoted. As the substrate, there is no limitation, and a single crystal Si substrate, an SOI substrate, a stainless steel (SUS) substrate, a quartz glass substrate, a single crystal gallium nitride (GaN) substrate, a single crystal silicon carbide (SiC) substrate, or a sapphire substrate on the surface of which a single crystal gallium nitride (GaN) is provided is cited.

[0070] Preferably, the substrate is a single-crystal Si substrate or an SOI substrate, and particularly preferably a single-crystal Si (100) substrate, a single-crystal Si (111) substrate, a (100) SOI substrate, or a (111) SOI substrate. Here, the SOI substrate is a substrate having a Si bulk portion and a surface Si layer, and having a configuration in which an insulating film such as a SiO2 film is interposed between the Si bulk portion and the surface Si layer. The surface Si layer is single-crystallized, and other layers (films) such as a buffer layer are provided on the surface Si layer. In addition, the (100) substrate and the (111) substrate are substrates in which a (100) plane or a (111) plane of the crystal lattice faces the main surface. By using such a substrate, the buffer layer, the orientation control film, or the functional thin film can be epitaxially grown on the substrate while sufficiently achieving lattice matching, and thus the crystallinity of these films can be improved.

[0071] <Buffer Layer>

[0072] In the layered structure of the present embodiment, the buffer layer including the mixed phase of the crystalline phase and the amorphous phase is interposed between the substrate and the orientation control film. By providing such a buffer layer, epitaxial growth of the functional thin film can be achieved, and problems such as interlayer peeling can be suppressed. That is, the buffer layer includes both the fine region having a crystalline configuration and the fine region having an amorphous configuration in a mixed manner. In the crystalline phase (fine region having a crystalline configuration), atoms are arranged in alignment with the crystal configuration of the single-crystal portion of the substrate located in the lower portion of the buffer layer. That is, the crystalline phase is epitaxially grown. In addition, since the crystalline phase has a regular atomic arrangement, it has an effect of promoting epitaxial growth of the crystal orientation control film provided in the upper portion of the buffer layer. On the other hand, since the fine region having an amorphous configuration has an irregular atomic arrangement, it has an effect of relaxing the constraint from the substrate and the stress generated by the substrate. Therefore, by providing the buffer layer including the mixed phase of the crystalline phase and the amorphous phase, epitaxial growth of the buffer film and the functional thin film provided thereon can be promoted to improve their crystallinity, and stress can be relaxed to suppress interlayer peeling.

[0073] The distribution manner of the crystalline phase and the amorphous phase in the buffer layer is not particularly limited. For example, it can be a manner in which the crystalline phase and the amorphous phase are uniformly distributed. Note that the amorphous phase includes not only a state in which no crystal configuration is present at all, but also a state in which a crystal configuration is present but the atomic arrangement deviates from a completely regular arrangement.

[0074] The composition of the buffer layer is not limited. It can be the same composition as the orientation control film, or it can be a different composition from the orientation control film. However, the buffer layer preferably contains zirconium oxide (Zr02) as a main component. Thereby, the epitaxial growth of the orientation control film containing zirconium oxide (Zr02) as a main component can be more effectively promoted. In the case where the buffer layer contains Zr02, Zr02has a crystal structure of monoclinic system, tetragonal system, or cubic crystal. In addition, the buffer layer can contain only Zr02, or it can contain other components. For example, it can contain rare earth elements, alkaline earth elements. In addition, Zr02may contain oxygen defects. Furthermore, in order to improve the characteristics, transition metal elements such as aluminum (Al), scandium (Sc), manganese (Mn), iron (Fe), cobalt (Co), and / or nickel (Ni) can be contained.

[0075] The thickness of the buffer layer is preferably 2 nm or more and 10 nm or less. If the thickness is 2 nm or more, the stress relaxation function of the amorphous phase contained in the buffer layer can be more effectively exerted. Therefore, the problem of interlayer peeling can be more effectively suppressed. In addition, if the thickness is 10 nm or less, the epitaxial growth of the orientation control film and the functional thin film provided on the upper portion of the buffer layer is more effectively promoted. From the viewpoint of improving the effects of epitaxial growth promotion and interlayer film peeling suppression, the thickness of the buffer layer is more preferably 2 nm or more and 10 nm or less, and further preferably 3 nm or more and 5 nm or less. In addition, other layers (films) can be interposed between the buffer layer and the substrate. However, from the viewpoint of promoting the epitaxial growth of the buffer layer or other layers (films) provided thereon, it is preferable to directly provide the buffer layer on the substrate.

[0076] <Orientation control film>

[0077] The orientation control film is provided on the single-crystal surface of the substrate through the buffer layer. That is, it is provided on the buffer layer. The orientation control film is a crystalline film containing zirconium oxide (Zr02) as a main component, and is also referred to as a buffer film. By providing such an orientation control film, when an electrode layer and a functional thin film are provided on the orientation control film, the single crystallization of the electrode layer and the functional thin film can be promoted.

[0078] The orientation control film can contain only Zr02, or it can contain rare earth elements, alkaline earth elements. In addition, Zr02may contain oxygen defects. Furthermore, in order to improve the characteristics, transition metal elements such as aluminum (Al), scandium (Sc), manganese (Mn), iron (Fe), cobalt (Co), and / or nickel (Ni) can be contained.

[0079] The thickness of the orientation control film is preferably 10 nm or more and 1500 nm or less, more preferably 20 nm or more and 1200 nm or less, and further preferably 30 nm or more and 1000 nm or less. In addition, the orientation control film is preferably an epitaxial film formed on the buffer layer, and further preferably an epitaxial film of (100) orientation. In addition, other layers (films) can be interposed between the orientation control film and the buffer layer. However, from the viewpoint of promoting epitaxial growth of the orientation control film and other layers (films) provided thereon, it is preferable to directly provide the orientation control film on the buffer layer.

[0080] <First electrode layer>

[0081] The laminated structure can also have a first electrode layer as needed. The first electrode layer is provided on the orientation control film. The first electrode layer functions as an electrode of the functional thin film. For example, in the case where the functional thin film is a piezoelectric film, a potential difference based on a surface potential of the piezoelectric film generated by a positive piezoelectric effect can be detected by the electrode layer. Alternatively, a potential difference can be applied to the piezoelectric film by the electrode layer, and a deformation occurs based on a reverse piezoelectric effect generated thereby. The first electrode layer only needs to have conductivity, and the material thereof is not limited. For example, it contains at least one selected from the group consisting of platinum (Pt), molybdenum (Mo), ruthenium (Ru), aluminum (Al), and copper (Cu).

[0082] The thickness of the first electrode layer is preferably 10 nm or more and 500 nm or less, more preferably 30 nm or more and 300 nm or less, and further preferably 50 nm or more and 200 nm or less. In addition, the first electrode layer is preferably an epitaxial film formed on the orientation control film, and further preferably an epitaxial film of (100) orientation. In addition, preferably, the first electrode layer is a single-crystal film composed of a single crystal. By providing the first electrode layer as a single-crystal film, the first metal oxide film and the functional thin film formed thereon can be single-crystal films.

[0083] <First metal oxide film>

[0084] The layered structure body can also have a first metal oxide film as needed. The first metal oxide film is provided on the orientation control film and / or the first electrode layer. The first metal oxide film is preferably composed of strontium ruthenate (SrRuO3; SRO). SRO has electrical conductivity. Therefore, the SRO film (first metal oxide film) can be used as part of the electrode layer (first electrode layer). In addition, the lattice constant of SRO is similar to that of a perovskite compound such as PZT, BT, or KNN. Therefore, in the case where a functional thin film including such a perovskite compound is used, by providing the SRO film between the first electrode layer and the functional thin film, the crystallinity of the functional thin film formed thereon can be further improved. In particular, a functional thin film having a film thickness of submicron size is likely to have crystal defects. By providing the first metal oxide film, a functional thin film having few crystal defects can be formed even if the film thickness is submicron size. However, the first metal oxide film is not an essential component. In the case where the thickness of the functional thin film is sufficiently large, a functional thin film having few crystal defects can be obtained even if the first metal oxide film is not present.

[0085] The thickness of the first metal oxide film (SRO film) is preferably 1 nm or more and 100 nm or less, more preferably 3 nm or more and 80 nm or less, and further preferably 5 nm or more and 60 nm or less. In addition, the first metal oxide film is preferably an epitaxial film formed on the first electrode layer, and further preferably a (100)-oriented epitaxial film. In addition, preferably, the first metal oxide film is a single-crystal film.

[0086] <FUNCTIONAL THIN FILM>

[0087] The functional thin film is provided on the orientation control film. That is, it can be provided directly above the orientation control film, or it can be provided on the orientation control film with other layers such as the first electrode layer and / or the first metal oxide film interposed therebetween. The functional thin film is a layer that becomes the main body of the function of the layered structure body. The type of the functional thin film can be determined as appropriate in accordance with the use of the layered structure body. For example, as the functional thin film, a piezoelectric film, a dielectric film, a ferroelectric film, a magnetic film, a resistive film, or an optical film, or the like is exemplified.

[0088] In the layered structure body of the present embodiment, the crack penetration degree of the functional thin film is 80% or less. The crack penetration degree is an index indicating the degree to which a crack penetrates the functional thin film, and is defined by the ratio (percentage) of the crack depth in the film thickness direction of the functional film thickness to the film thickness of the functional thin film. In the case where a crack that progresses in the entire thickness of the functional thin film in a manner connecting the two opposing surfaces (front and back surfaces) of the functional thin film is present, the crack penetration degree is 100%. On the other hand, in the case where no crack is present in the functional thin film, the crack penetration degree is 0%. By suppressing the crack penetration degree to a relatively small value, various problems based on the crack, such as problems of occurrence of a leakage current, and the like, can be avoided.

[0089] Note that, in the layered structure body having the functional film, a crack can sometimes occur in the functional film due to a difference in physical properties of each layer constituting the layered structure body. For example, a stress can occur in the orientation control film at the time of film formation or after film formation due to a difference in physical property values (lattice constant, coefficient of thermal expansion, etc.) of the substrate, the buffer layer, and the orientation control film, and a crack can occur in the orientation control film. Then, when the orientation control film has a crack, the crack can sometimes extend to the functional film provided above the orientation control film.

[0090] When a long (deep) crack is present in the functional film, a problem such as appearance failure or characteristic failure can occur. For example, when a crack that penetrates the front and back surfaces of the functional film is present, a leakage current flowing in the crack can sometimes occur when a voltage is applied to the functional film for functional presentation, and the functional presentation can be hindered. In addition, even when the crack does not penetrate the front and back surfaces, the voltage resistance of the functional film can sometimes decrease when a long (deep) crack is present. Therefore, it is not desirable that a long (deep) crack be present.

[0091] The functional film in the layered structure body of the present embodiment does not have a crack, or even when it has a crack, the length thereof is relatively small. Therefore, a problem caused by a crack can be suppressed. It is desirable that the crack penetration degree be small, and more preferably 70% or less. The lower limit of the crack penetration degree is not particularly limited. However, the crack penetration degree can be 0.1% or more, 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, or 60% or more.

[0092] Note that the crack penetration degree is found by observing the cross section of the functional film using a scanning electron microscope (SEM). Specifically, the fractured surface of the layered structure body is observed using SEM. Then, the film thickness (d) of the functional film and the crack depth (1) in the film thickness direction of the functional film are found, respectively. Here, the crack depth is not the actual length of the crack, but the length in the thickness direction of the portion in which the crack is present in the functional film. Furthermore, the crack penetration degree is calculated according to the following formula (1).

[0093] [Formula 1]

[0094]

[0095] Preferably, the functional thin film is a piezoelectric film. That is, preferably, the laminated structure is a piezoelectric device. The piezoelectric film is a constituent element that becomes a main body that exhibits a piezoelectric effect, and has a function of converting electric energy and mechanical energy. When a pressure (force) is applied to the piezoelectric film, surface charges are generated in the upper and lower portions of the piezoelectric film by a direct piezoelectric effect, and thus a potential difference (voltage) is generated. Therefore, the piezoelectric film can be used as a sensor. In addition, when a potential difference (voltage) is applied to the upper and lower portions of the piezoelectric film, the piezoelectric film is displaced by an inverse piezoelectric effect. Therefore, the piezoelectric film can be used as an actuator.

[0096] Preferably, the piezoelectric film contains at least one compound selected from the group consisting of lead zirconate titanate (Pb(Zr,Ti)O3; PZT), barium titanate (BaTiO3; BT), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O3; PLZT), lithium niobate (LiNbO3; LN), lithium tantalate (LiTaO3; LT), potassium sodium niobate ((K,Na)NbO3; KNN), aluminum nitride (AIN), and zinc oxide (ZnO) as a main component. These compounds exhibit excellent piezoelectric properties.

[0097] Particularly preferably, the piezoelectric film contains lithium niobate as a main component. Since lithium niobate has a large thermal expansion coefficient, when cooled after film formation at high temperature, deformation caused by heating becomes a major cause of a difference in the thermal expansion coefficient from the substrate, and cracks are more likely to be formed. The laminated structure of the present embodiment has the following feature: even if the piezoelectric film (functional thin film) containing lithium niobate, which is likely to form cracks, as a main component is provided, the progress of cracks in the piezoelectric film can be suppressed. Note that, in the present specification, the main component refers to a component that is the heaviest in the object, that is, a component having a content of 50% by mass or more.

[0098] Preferably, the functional thin film is a single crystal film composed of a single crystal. By being a single crystal film, sometimes the function of the functional thin film can be improved. For example, in the case where the functional thin film is a piezoelectric film, the polarization directions of the entire film can be made completely uniform. Therefore, the electric properties and the mechanical properties can be improved. Specifically, the piezoelectric constant can be improved. In addition, compared to a polycrystal film, the dielectric constant can be suppressed, and thus the power consumption can be reduced, and in the case of being used as a sensor, the output can be made highly accurate. Furthermore, by being single-crystallized, the atomic bonding force is improved, and thus the temperature properties and the reliability of the piezoelectric film are improved.

[0099] The thickness of the functional thin film is preferably 0.1 μm or more and 10 μm or less. When the functional thin film is excessively thin, it is difficult to sufficiently exert the function of the functional thin film. For example, in the case where the functional thin film is a piezoelectric film, the amount of displacement obtained can be small. On the other hand, when the functional thin film is excessively thick, it can be difficult to obtain a sufficiently single-crystallized functional thin film. The thickness is more preferably 0.3 μm or more and 6 μm or less, and further preferably 0.5 μm or more and 4 μm or less.

[0100] As to whether the functional thin film is a single-crystal film, it can be confirmed by in-plane scanning measurement using an X-ray diffraction method. That is, if a symmetrical peak is confirmed by in-plane scanning, it can be judged that the functional thin film is a single-crystal film. For example, if it is a cubic crystal (100), a peak of 4-fold symmetry can be confirmed, and if it is a hexagonal crystal (110), a peak of 6-fold symmetry can be confirmed. That is, if a symmetrical peak for a specific plane is confirmed by in-plane scanning, it can be judged that the functional thin film is a single-crystal film.

[0101] <Second Metal Oxide Film>

[0102] As needed, the laminated structure can also have a second metal oxide film on the functional thin film. The second metal oxide film is composed of strontium ruthenate (SrRuO3; SRO). SrO has conductivity. Therefore, the SRO film (second metal oxide film) can be used as part of the electrode layer (second electrode layer).

[0103] The thickness of the second metal oxide film (SRO film) is preferably 1 nm or more and 60 nm or less, more preferably 3 nm or more and 30 nm or less, and further preferably 5 nm or more and 20 nm or less. In addition, the second metal oxide film is preferably an epitaxial film formed on the functional thin film, and further preferably a (100)-oriented epitaxial film.

[0104] <Second Electrode Layer>

[0105] As needed, the laminated structure can also have a second electrode layer on the functional thin film and / or the second metal oxide film. The second electrode layer only needs to have conductivity, and the material thereof is not limited. For example, it is preferable to contain at least one selected from the group consisting of platinum (Pt), molybdenum (Mo), ruthenium (Ru), aluminum (Al), and copper (Cu).

[0106] The thickness of the second electrode layer is preferably 1 nm or more and 200 nm or less, more preferably 3 nm or more and 150 nm or less, and further preferably 10 nm or more and 120 nm or less. In addition, the second electrode layer is preferably an epitaxial film formed on the functional thin film and / or the second metal oxide film, and further preferably an epitaxial film of (100) orientation.

[0107] The laminated structure can also have a constituent element other than the substrate, the buffer layer, the orientation control layer, the first electrode layer, the first metal oxide film, the functional thin film, the second metal oxide film, and the second electrode layer. For example, it can have an extraction electrode that is in conduction with the first electrode layer and the second electrode layer, and a protective film provided on the upper portion of the device.

[0108] In addition, the laminated structure can also have a hollow portion in which a part of the substrate is missing. The constituent elements (the buffer layer, the orientation control layer, the first electrode layer, the first metal oxide film, the functional thin film, the second metal oxide film, and the second electrode layer) present on the hollow portion form a diaphragm structure. By providing the hollow portion, the characteristics of the functional thin film are sometimes improved. For example, in the case where the functional thin film is a piezoelectric film, by providing the hollow portion, displacement based on the piezoelectric film can be effectively exhibited.

[0109] <<2. Method for manufacturing the laminated structure>>

[0110] The laminated structure of the present embodiment satisfies the above-described requirements, and the method for manufacturing the same is not limited. However, a preferred method for manufacturing the same has the following steps: a step of preparing a substrate whose at least a surface is composed of a single crystal (substrate preparation step); a step of forming a buffer layer on the single crystal surface of the substrate (buffer layer formation step); a step of forming an orientation control film containing zirconium oxide (Zr02) as a main component on the buffer layer after the formation (orientation control film formation step); a step of aging the substrate on which the buffer layer and the orientation control film are formed by keeping it at a temperature of 500°C or higher and 600°C or lower for a time of 30 minutes or more and 1 hour or less (aging step); and a step of forming a functional thin film on the orientation control film after the aging (functional thin film formation step). In addition, the formation of the buffer layer is performed at a film formation rate of 5 nm / min or more and 50 nm / min or less, and the formation of the orientation control film is performed at a film formation rate of 1 nm / min or more and 5 nm / min or less. Further, other steps of forming the first electrode layer, the first metal oxide film, the second metal oxide film, the second electrode layer, and the like can be provided as needed. The details of each step are described below.

[0111] <Substrate preparation step>

[0112] In the substrate preparation step, a substrate whose surface is composed of a single crystal is prepared. Details of the substrate are as described above. That is, as the substrate, there is no limitation, and a single crystal Si substrate, an SOI substrate, a stainless steel (SUS) substrate, a quartz glass substrate, a single crystal gallium nitride (GaN) substrate, a single crystal silicon carbide (SiC) substrate, or a sapphire substrate provided with a single crystal gallium nitride (GaN) on the surface is exemplified. Preferably, the substrate is a single crystal Si substrate or an SOI substrate, and particularly preferably, it is a single crystal Si (100) substrate, a single crystal Si (111) substrate, a (100) SOI substrate, or a (111) SOI substrate. By using such a substrate, an orientation control film excellent in crystallinity can be easily obtained.

[0113] <Buffer layer film formation step>

[0114] In the buffer layer film formation step, a buffer layer is formed on the single crystal surface of the prepared substrate. The film formation can be performed by an electron beam evaporation method. In the case where the film formation is performed by the electron beam evaporation method, for example, the substrate is disposed in a vacuum chamber of an evaporation device. Then, under a condition where the pressure in the vacuum chamber is set to a fixed high vacuum atmosphere, oxygen (O2) gas is flown, and under this state, the buffer layer is formed while heating the substrate.

[0115] The film formation of the buffer layer by the electron beam evaporation method is performed at a relatively large film formation speed (rate) of 5 nm / min or more and 50 nm / min or less. When the film formation is performed at a large rate, migration of particles on the substrate is appropriately suppressed, and thus, a fine structure including both a crystal phase and an amorphous phase is realized. In the buffer layer film formation, the substrate is preferably heated to a temperature of 200°C or more and 450°C or less. By performing the film formation under a condition where the substrate is heated to a temperature in this range, formation of the above-described fine structure is promoted.

[0116] <Orientation control film formation step>

[0117] In the orientation control film formation step, an orientation control film containing zirconium oxide (ZrO2) as a main component is formed on the buffer layer. As in the buffer layer film formation step, the film formation can be performed by an electron beam evaporation method. In addition, the film formation of the buffer layer and the film formation of the orientation control film can be continuously performed using the same device, or the film formation of the buffer layer and the film formation of the orientation control film can be separately performed.

[0118] The orientation control film is formed by an electron beam evaporation method at a relatively small film formation rate (speed) of 1 nm / min or more and 5 nm / min or less. When the film is formed at a relatively small rate, migration of the particles on the substrate surface progresses by the heat energy generated by heating of the substrate, and an orientation control film with high crystallinity is obtained. When the orientation control film is formed, the substrate is preferably heated to a temperature of 450°C or higher and 650°C or lower. By forming the film while the substrate is heated to a temperature within this range, an increase in crystallinity can be achieved.

[0119] <Maturation Step>

[0120] In the maturation step, the substrate on which the buffer layer and the orientation control film are formed is maintained at a temperature of 500°C or higher and 600°C or lower for a time of 30 minutes or more and 1 hour or less. The substrate is left as it is in the maturation step. That is, no operation such as film formation is performed. By providing the maturation step, the degree of penetration of cracks in the functional thin film can be suppressed to be small. This is considered to be because migration of the particles constituting the orientation control film progresses at the time of maturation, and thus, stress in the inside of the orientation control film becomes small, as a result, the progress of cracks in the orientation control film and the functional thin film provided thereon is suppressed.

[0121] When the maturation temperature is excessively low or the maturation time is excessively short, migration of the particles does not sufficiently progress. Thus, it can be difficult to sufficiently exert the effect of suppression of the progress of cracks. When the maturation temperature is excessively high or the maturation time is excessively long, the cycle time becomes long, and the production efficiency can deteriorate. Note that the surrounding atmosphere at the time of maturation is preferably an oxygen-containing atmosphere.

[0122] <First Electrode Layer Formation Step>

[0123] A step of forming the first electrode layer on the orientation control film can also be provided as needed. The first electrode layer contains, for example, at least one selected from the group consisting of platinum (Pt), molybdenum (Mo), ruthenium (Ru), aluminum (Al), and copper (Cu). The formation of the first electrode layer can be performed by a publicly known method such as a sputtering method. In the case of sputtering film formation, for example, the first electrode layer after epitaxial growth can be formed on the orientation control film as a part of the base electrode by a sputtering method while the substrate is heated. Alternatively, a photolithography technique can be used, and patterning processing of partially removing the first electrode layer after film formation can be performed.

[0124] <First Metal Oxide Film Formation Step>

[0125] If necessary, a step of forming a first metal oxide film on the orientation control film and / or the first electrode layer can also be provided. The first metal oxide film is preferably composed of strontium ruthenate (SrRu03; SRO). The formation of the first metal oxide film can be performed by a publicly known method such as sputtering. In the case of sputtering film formation, for example, the epitaxially grown first metal oxide film can be formed on the substrate while heating the substrate. Alternatively, patterning processing of partially removing the formed first metal oxide film can be performed using a photolithography technique.

[0126] <Functional thin film formation step>

[0127] In the functional thin film formation step, a functional thin film is formed on the aged orientation control film. The formation of the functional thin film can be performed by a publicly known method. For example, the film formation can be performed by a sputtering method or a sol-gel method or the like. Alternatively, patterning processing of partially removing the formed functional thin film can be performed using a photolithography technique.

[0128] <Second metal oxide film formation step>

[0129] If necessary, a second metal oxide film can also be formed on the functional thin film. The second metal oxide film is composed of strontium ruthenate (SrRu03; SRO). The formation of the second metal oxide film can be performed by a publicly known method such as sputtering. In the case of sputtering film formation, for example, the epitaxially grown second metal oxide film can be formed on the functional thin film by sputtering as a part of the lower electrode. Alternatively, patterning processing of partially removing the formed second metal oxide film can be performed using a photolithography technique.

[0130] <Second electrode layer formation step>

[0131] If necessary, a second electrode layer can also be formed on the functional thin film and / or the second metal oxide film. The second electrode layer contains, for example, at least one selected from the group consisting of platinum (Pt), molybdenum (Mo), ruthenium (Ru), aluminum (Al), and copper (Cu). The formation of the second electrode layer can be performed by a publicly known method such as sputtering. For example, the second electrode layer containing the epitaxially grown Pt can be formed on the functional thin film or the second metal oxide film by sputtering as a part of the lower electrode. Alternatively, patterning processing of partially removing the formed second electrode layer can be performed using a photolithography technique.

[0132] <Lead electrode formation step>

[0133] If necessary, a lead electrode can also be formed on the second electrode layer. The formation of the lead electrode can be performed by a publicly known method such as sputtering. Alternatively, patterning processing of partially removing the formed lead electrode layer can be performed using a photolithography technique.

[0134] <Protection film forming step>

[0135] If necessary, the protection film can be formed on the second electrode layer and / or the extraction electrode. There is no limitation on the protection film, and tetraethyl orthosilicate (TEOS) or the like can be used. The protection film can be formed by sputtering or the like. Alternatively, a photolithography technique can be used to perform patterning processing for partially removing the protection film after the film formation.

[0136] <Formation of hollow portion>

[0137] If necessary, a step of removing at least a portion of the substrate and forming a hollow portion directly below the functional thin film can be provided when the layered structure is manufactured. Thus, a movable portion having a cantilever structure or a diaphragm structure can be formed. If the layered structure having such a movable portion is applied to a piezoelectric device, for example, a device having a large displacement amount can be obtained. The formation of the hollow portion is preferably performed after the formation of the buffer layer, the orientation control film, the first electrode layer, the first metal oxide film, the functional thin film, the second metal oxide film, and the second electrode layer on the substrate.

[0138] The formation of the hollow portion can be performed in combination with a photolithography technique and an etching technique. Specifically, a mask having an opening portion is closely disposed on the back surface of the substrate. Then, the substrate is etched and removed from the mask opening portion using an alkaline etching solution. For example, the Si substrate or the SOI substrate is anisotropically etched using the alkaline etching solution to form a hollow portion having a quadrangular pyramid shape. In the case where the Si substrate is used, the buffer film (ZrO2 film) on the Si substrate functions as an etching stopper layer. Thus, a layered structure having no substrate directly below the functional thin film can be manufactured. The insulating film (SiO2 film) included in the SOI substrate functions as an etching stopper layer. In addition, the insulating film can be removed using an etching solution such as hydrofluoric acid. Thus, a layered structure having a surface Si layer or a surface Si layer and an insulating film (SiO2 film) directly below the functional thin film can be manufactured.

[0139] <3. Manufacturing apparatus for layered structure>

[0140] The manufacturing apparatus for the layered structure of the present application is characterized by including a vacuum transfer apparatus and a multi-chamber having a vacuum evaporation apparatus and a sputtering apparatus. By using the apparatus, continuous film formation in which the evaporation step and the sputtering step can be continuously performed can be achieved, and the productivity is improved.

[0141] [Examples]

[0142] The present application will be described in more detail using the following examples and comparative examples. However, the present application is not limited to the following examples.

[0143] [Experimental Example A (Reference Experimental Example)]

[0144] In Experimental Example A, a layered structure body having a substrate, a buffer layer, and an orientation control film was produced, and evaluation thereof was performed.

[0145] (1) Production of Layered Structure Body

[0146] [Example Al]

[0147] In Example Al, an SOI (100) wafer was used as a substrate, and after a buffer layer and an orientation control film were formed thereon, annealing was performed.

[0148] First, an SOI (100) wafer having a diameter of 6 inches was prepared. This SOI wafer had a three-layer structure of a Si base portion, an insulating film (SiO2 film), and a surface Si layer. In addition, the main surface was a (100) surface. That is, the surface Si layer was subjected to (100) orientation.

[0149] Next, a zirconia (ZrO2) film was formed on the surface Si layer of the prepared SOI substrate by an electron beam evaporation method. The formation was performed in two stages with changed conditions, and the ZrO2 film after formation in each stage was set as a buffer layer and an orientation control film, respectively. The ZrO2 film after formation had a crystal structure of a cubic system with (100) orientation. The formation conditions of the buffer layer and the orientation control film are shown below.

[0150] <Buffer Layer Formation Conditions>

[0151] - Apparatus: Electron beam evaporation apparatus

[0152] - Pressure: 7.00 x 10 -3 Pa

[0153] - Evaporation source: ZrO2

[0154] - Acceleration voltage: 7.5 kV

[0155] - Emission current: 1.80 mA

[0156] - Oxygen flow rate: 10 seem

[0157] - Substrate temperature: 300 to 400°C

[0158] - Film formation rate: 10 nm / min

[0159] - Film thickness: 4 nm

[0160] <Orientation Control Film Formation Conditions>

[0161] - Apparatus: Electron beam evaporation apparatus

[0162] - Pressure: 7.00 x 10-3 Pa

[0163] - Evaporation source: ZrO2

[0164] - Acceleration voltage: 7.5 kV

[0165] - Emission current: 1.80 mA

[0166] - Oxygen flow rate: 10 seem

[0167] - Substrate temperature: 500 to 600°C

[0168] - Film formation rate: 3 nm / min

[0169] - Film thickness: 60 nm

[0170] Next, the substrate on which the buffer layer and the orientation control film were formed was subjected to ripening to produce a layered structure. The ripening was performed under the following conditions.

[0171] < Ripening Conditions >

[0172] - Substrate temperature: 550°C

[0173] - Holding time: 45 minutes

[0174] - Oxygen flow rate: 10 seem

[0175] [Example A2]

[0176] In Example A2, a Si (111) wafer was used as the substrate instead of the SOI (100) wafer. In addition, the film thickness of the orientation control film was set to 1.0 μm. Other than this, the layered structure was produced in the same manner as in Example Al.

[0177] [Example A3]

[0178] In Example A3, the formation of the buffer layer was not performed, and the orientation control film was formed directly on the substrate. Other than this, the production of the layered structure was performed in the same manner as in Example A2.

[0179] (2) Evaluation and Results

[0180] The layered structures produced were evaluated for various characteristics.

[0181] < TEM Observation >

[0182] The cross sections of the layered structures obtained in Examples Al to A3 were observed by transmission electron microscopy (TEM). Specifically, the cross sections of the samples thinned to a thickness of 0.1 micrometer or less were observed under the condition of an acceleration voltage of 200 kV. Note that the transmission electron microscopy is a kind of electron microscopy, and is a method in which the spatial distribution of electron transmissivity in an observation object is observed by irradiating a sample thinned to a thickness of 0.1 micrometer or less with electron beams and by the intensity of the transmitted electron beams, whereby the internal structure is analyzed. The magnification range can cover observation of objects of several tens of micrometers (a few hundred times) to observation of atomic arrangement structures of sub-nanometers (a few million times), and thus, atomic-level fine structure analysis of the cross sections / interfaces of thin film layered structures can be performed.

[0183] Figure 2-1 and Figure 2-2 A cross-sectional TEM image of the layered structure of Example Al is shown. In addition, Figure 3-1 and Figure 3-2 A cross-sectional TEM image of the layered structure of Example A2 is shown. Here, Figure 2-1 and Figure 3-1 is a TEM image at a magnification of 2 million times, Figure 2-2 and Figure 3-2 is a TEM image at a magnification of 4 million times.

[0184] Example Al and Example A2 each have a buffer layer (a layer having a thickness of about 4 nm) interposed between the substrate and the orientation controlling film. Figure 2-1 and Figure 3-1 In addition, a region in which the lattice image is blurred (an amorphous region) and a region in which the lattice image is clearly observed (a crystal region) are confirmed in the buffer layer. Figure 2-2 and Figure 3-2

[0185] Figure 4 A cross-sectional TEM image of the layered structure of Example A3 is shown. The substrate and the orientation controlling film are in contact with each other, and no buffer layer is observed between them.

[0186] [Experimental Example B (Reference Experiment)]

[0187] In Experimental Example B, a piezoelectric device composed of a layered structure having a piezoelectric film as a functional film was fabricated, and evaluation thereof was performed. Specifically, the crystal state of each layer (a buffer layer, an orientation controlling film, a piezoelectric film, and the like) constituting the layered structure was investigated.

[0188] (1) Fabrication of Layered Structure

[0189] [Example Bl]

[0190] ​In Example B1, a Pt film (first electrode layer), an SRO film (first metal oxide film), and a PZT film (piezoelectric film) were sequentially formed on the ZrO2 film (orientation control film) formed in Example Al to produce a piezoelectric device (laminated structure).

[0191] First, a Pt film (first electrode layer) was sputter-deposited on the ZrO2 film formed in Example Al. The deposited Pt film had a crystal structure of cubic crystal system with (100) orientation, and had a film thickness of 150 nm. The deposition was performed under the following conditions.

[0192] <First electrode layer deposition conditions>

[0193] - Apparatus: DC sputtering apparatus

[0194] - Target: Pt

[0195] - Power: 100 W

[0196] - Pressure: 3.20 x 10 -2 Pa

[0197] - Ar flow rate: 16 seem

[0198] - Substrate temperature: 400°C

[0199] - Deposition rate: 0.14 nm / sec

[0200] - Film thickness: 150 nm

[0201] Next, an SRO film (first metal oxide film) was sputter-deposited on the deposited Pt film. The deposited SRO film had a crystal structure of cubic crystal system with (100) orientation, and had a film thickness of 40 nm. The deposition was performed under the following conditions.

[0202] <First metal oxide film deposition conditions>

[0203] - Apparatus: RF magnetron sputtering apparatus

[0204] - Target: strontium ruthenate (SrRuO3; SRO)

[0205] - Power: 300 W

[0206] - Gas: Ar

[0207] - Pressure: 1.8 Pa

[0208] - Substrate temperature: 600°C

[0209] - Deposition rate: 0.11 nm / sec

[0210] - Film thickness: 40 nm

[0211] A PZT film (piezoelectric film) was formed on the SRO film (first metal oxide film) formed. The film formation was performed by a Sol-Gel method. Specifically, first, an organic metal compound of Pb, Zr, and Ti was dissolved in a mixed solvent of ethanol and 2-n-butoxyethanol to prepare a raw material solution. At this time, the organic metal compound of Pb, Zr, and Ti was prepared so as to have a composition ratio (molar ratio) of Pb:Zr:Ti = 100 + δ:52:48. Further, the raw material solution was prepared so that the concentration of Pb(Zr 0.52 Ti 0.48 )03 was 0.35 mol / 1. Here, δ is the amount of residual Pb taking into account the volatilization of Pb oxide during the subsequent heat treatment, and in this case, δ = 20. Then, polypyrrolidone having a K value of 27 to 33: 20 g was dissolved in the raw material solution.

[0212] Next, 3 ml of the prepared raw material solution was dropped onto the first metal oxide film (SRO film) of the substrate, and the substrate was rotated at 3000 rpm for 10 seconds to coat the raw material solution on the substrate. Thus, a film containing a precursor was formed. Then, the substrate on which the film containing the precursor was formed was placed on a hot plate at a temperature of 200°C for 30 seconds, and further placed on a hot plate at a temperature of 450°C for 30 seconds to dry the film. Thereafter, the film was subjected to heat treatment at 600 to 700°C for 60 seconds in an oxygen (02) atmosphere at 0.2 MPa to oxidize and crystallize the precursor. The process from the coating of the raw material solution to the crystallization was repeated any number of times until the desired film thickness was obtained to form a piezoelectric film (PZT film).

[0213] The PZT film after the film formation was oriented in the (001) direction, and the film thickness was 2 μm. Further, the composition of the PZT film was Pb(Zr 0.52 Ti 0.48 )03.

[0214] [Example B2]

[0215] In Example B2, a Pt film (first electrode layer) and a LiNb03 film (piezoelectric film) were further sequentially formed on the Zr02 film (orientation control film) formed in Example A2 to produce a piezoelectric device (laminated structure).

[0216] First, a Pt film (first electrode layer) was sputter-formed on the Zr02 film after the film formation in Example A2. The film formation was performed under the following conditions.

[0217] <First electrode layer film formation conditions>

[0218] - Apparatus: DC sputtering apparatus

[0219] - Target material: Pt

[0220] - Power: 100 W

[0221] - Pressure: 1.20 x 10 -1 Pa

[0222] - Substrate temperature: 450 to 600°C

[0223] - Film thickness: 150 nm

[0224] Next, a LiNbO3 film (piezoelectric film) was sputter-deposited on the Pt film. The deposition was performed under the following conditions.

[0225] < Piezoelectric film deposition conditions >

[0226] - Apparatus: RF sputtering apparatus

[0227] - Target material: LiNbO3

[0228] - Power: 1000 W

[0229] - Gas: Ar / O2

[0230] - Pressure: 2 Pa

[0231] - Substrate temperature: 450°C

[0232] - Film thickness: 500 nm

[0233] [Example B3]

[0234] In Example B3, a Pt film (first electrode layer) and an AlN film (piezoelectric film) were further sequentially deposited on the ZrO2 film (orientation control film) formed in Example A2 to produce a piezoelectric device (laminated structure).

[0235] First, a Pt film (first electrode layer) was sputter-deposited on the ZrO2 film formed after the deposition in Example A2. The deposition was performed under the following conditions.

[0236] < First electrode layer deposition conditions >

[0237] - Apparatus: DC sputtering apparatus

[0238] - Target material: Pt

[0239] - Power: 100 W

[0240] - Pressure: 1.20 x 10 -1 Pa

[0241] - Substrate temperature: 450 to 600°C

[0242] - Device: DC sputtering device

[0243] Next, the AlN film (piezoelectric film) was sputter-deposited on the Pt film. The deposition was performed under the following conditions.

[0244] < Piezoelectric film deposition conditions >

[0245] - Device: DC sputtering device

[0246] - Target: Al

[0247] - Power: 450 W

[0248] - Gas: Ar / N2

[0249] - Pressure: 2 Pa

[0250] - Substrate temperature: 450°C

[0251] - Film thickness: 600 nm

[0252] [Example B4]

[0253] In Example B4, a Pt film (first electrode layer) and a BaTiO3 film (piezoelectric film) were further sequentially deposited on the ZrO2 film (orientation control film) formed in Example A2 to produce a piezoelectric device (laminated structure).

[0254] First, the Pt film (first electrode layer) was sputter-deposited on the ZrO2 film formed after the deposition in Example A2. The deposition was performed under the following conditions.

[0255] < First electrode layer deposition conditions >

[0256] - Device: DC sputtering device

[0257] - Target: Pt

[0258] - Power: 100 W

[0259] - Pressure: 1.20 x 10 -1 Pa

[0260] - Substrate temperature: 450 to 600°C

[0261] - Film thickness: 150 nm

[0262] Next, the BaTiO3 film (piezoelectric film) was sputter-deposited on the Pt film. The deposition was performed under the following conditions.

[0263] < Piezoelectric film deposition conditions >

[0264] - Device: RF sputtering device

[0265] Target: BaTiO3

[0266] Power: 450 W

[0267] Gas: Ar / O2

[0268] Pressure: 2 Pa

[0269] Substrate temperature: 450°C

[0270] Film thickness: 600 nm

[0271] (2) Evaluation and Results

[0272] The following describes various evaluations of the layered structure (piezoelectric device) produced.

[0273] <SEM and TEM observation>

[0274] The cross sections of the layered structures obtained in Examples Bl to B4 were observed by transmission electron microscopy (TEM). The TEM observation was performed at an acceleration voltage of 200 kV with respect to the sample cross sections thinned to a thickness of 0.1 μm or less.

[0275] Figure 5 (Example Bl), Figure 6 (Example B2), Figure 7 (Example B3), and Figure 8 (Example B4) show the obtained TEM images.

[0276] In the layered structure of Example Bl, the respective layers of the substrate (Si (100)), the buffer layer (ZrO2), the orientation control film (ZrO2), the first electrode layer (Pt), the first metal oxide film (SRO), and the piezoelectric film (PZT) were clearly observed (left image of FIG. 10). In addition, in the buffer layer, a region in which the lattice image was blurred (amorphous region) and a region in which the lattice image was clearly observed (crystalline region) were confirmed (right image of FIG. 10). Figure 5 Figure 5 In the layered structures of Examples B2 to B4, the respective layers of the substrate (Si (111)), the buffer layer (ZrO2), the orientation control film (ZrO2), the first electrode layer (Pt), and the piezoelectric film (LiNbO3, AlN, BaTiO3) were clearly observed (left image of FIG. 11). In addition, in the buffer layer, a region in which the lattice image was blurred (amorphous region) and a region in which the lattice image was clearly observed (crystalline region) were confirmed (right image of FIG. 11).

[0277] < XRD > Figure 6 to 8 Figure 6 to 8

[0278] < XRD >

[0279] ​​​For the layered structure obtained in Example B3, X-ray diffraction (XRD) analysis was performed using an X-ray diffractometer (Rigaku Corporation, SmartLab). At the time of analysis, ω-2θ scan and Φ scan were performed. Note that the Φ scan is a measurement method used to investigate whether the thin film is in-plane oriented.

[0280] Figure 9 The XRD spectrum obtained by the ω-2θ scan is shown. The horizontal axis of the spectrum (graph) indicates the angle 2θ (20°≤2θ≤60°) in the ω-2θ scan, and the horizontal axis indicates the X-ray intensity. According to Figure 9 , it was confirmed that the Pt film (first electrode layer) was a Pt (111) single orientation film, and the AlN film (piezoelectric film) was an AlN (002) single orientation film.

[0281] Figure 10 The XRD spectrum obtained by the Φ scan is shown. Six diffraction peaks at equal intervals were observed. This indicates that the AlN film is a 3-axis epitaxial film having not only c-axis orientation to the normal direction of the substrate but also in-plane orientation.

[0282] For the Pt film and the PZT film of Example Bl, the Φ scan was performed similarly to the AlN film of Example B3. Note that the Φ scan of the Pt film was performed before the film formation of the SRO film (first metal oxide film) and the PZT film (piezoelectric film).

[0283] Figure 11 The results obtained are shown in Table 1 (Pt film) and Figure 12 (PZT film). For the Pt film and the PZT film, diffraction peaks at equal intervals were also observed. Thus, similarly to the AlN film, it was confirmed that the Pt film and the PZT film also became 3-axis orientation epitaxial films.

[0284] [Experimental Example C]

[0285] In Experimental Example C, a piezoelectric device composed of a layered structure having a piezoelectric film as a functional thin film was produced, and evaluation thereof was performed. Specifically, the degree of crack progression in the functional thin film was investigated, and the crack penetration degree was evaluated. At the same time, a peeling test was also performed.

[0286] (1) Production of Layered Structure

[0287] [Example Cl]

[0288] In Example Cl, a piezoelectric device (layered structure) was produced by further sequentially forming a Pt film (first electrode layer) and a LiNbO3 film (piezoelectric film) on the ZrO2 film (orientation control film) formed in Example Al.

[0289] First, Pt film (first electrode layer) was sputter-deposited on the ZrO2 film after the film formation in Example Al. The film formation was performed under the following conditions.

[0290] <First electrode layer film formation conditions>

[0291] - Apparatus: DC sputtering apparatus

[0292] - Target: Pt

[0293] - Power: 100 W

[0294] - Pressure: 1.20 x 10 -1 Pa

[0295] - Substrate temperature: 450 to 600°C

[0296] - Film thickness: 150 nm

[0297] Next, LiNbO3 film (piezoelectric film) was sputter-deposited on the Pt film. The film formation was performed under the following conditions.

[0298] <Piezoelectric film film formation conditions>

[0299] - Apparatus: RF sputtering apparatus

[0300] - Target: LiNbO3

[0301] - Power: 1000 W

[0302] - Gas: Ar / O2

[0303] - Pressure: 2 Pa

[0304] - Substrate temperature: 450°C

[0305] - Film thickness: 500 nm

[0306] [Example C2]

[0307] In Example C2, the oriented control film was deposited without being subjected to the aging process when the layered structure was produced. Otherwise, the layered structure (piezoelectric device) was produced in the same manner as in Example Cl.

[0308] (2) Evaluation and Results

[0309] The layered structure (piezoelectric device) produced was evaluated for various characteristics.

[0310] <Peeling test>

[0311] A repeated peeling test was performed on the layered structure obtained in Example C1. A transparent pressure-sensitive adhesive tape having a width of 25 ± 1.5 mm and an adhesive force of 10 ± 1 N was used, and the test was performed in accordance with IEC 60454-2.

[0312] In the repeated peeling test, no clear peeling was observed even when the test was performed 10 or more times.

[0313] <SEM observation>

[0314] The cross sections of the layered structures obtained in Examples C1 and C2 were observed by scanning electron microscopy (SEM). SEM observation was performed using a field emission scanning electron microscope (FE-SEM) under conditions of an acceleration voltage of 10 kV. Figure 13 Example C1) and Figure 14 Example C2) show the obtained SEM images.

[0315] In the layered structure of Example C1, in which a maturation process was provided after the formation of the orientation control film, although cracks were observed in the piezoelectric film (functional thin film), the cracks did not penetrate the piezoelectric film. In the SEM image, the film thickness (d) of the piezoelectric film and the crack depth (1) along the film thickness direction of the piezoelectric film were determined, and the crack penetration degree was calculated in accordance with the above (1), in which case the value was 69.615%.

[0316] In contrast, in the layered structure of Example C2, in which a maturation process was provided after the formation of the orientation control film, the cracks penetrated the piezoelectric film. Therefore, the crack penetration degree was 100%.

[0317] According to the above results, the present application provides a layered structure that enables the epitaxial growth of a functional thin film, while suppressing problems such as interlayer peeling and suppressing the progress of cracks in the functional thin film.

Claims

1. A layered structure, wherein, The stacked structure comprises: A substrate, at least its surface of which is composed of single crystals; A crystal orientation control film comprising zirconium oxide (ZrO2) as the main component disposed on the single crystal surface of the substrate; as well as A functional thin film is disposed on the crystal orientation control film. The laminated structure further includes a buffer layer comprising a mixed phase of crystalline and amorphous phases, the buffer layer being sandwiched between the substrate and the alignment control film. The crack penetration rate, defined as the ratio of the vertical depth of the crack to the thickness of the functional film, is 80% or less.

2. The layered structure according to claim 1, wherein, The substrate is a single-crystal Si substrate, SOI substrate, stainless steel (SUS) substrate, quartz glass substrate, single-crystal gallium nitride (GaN) substrate, single-crystal silicon carbide (SiC) substrate, or a sapphire substrate with single-crystal gallium nitride (GaN) disposed on its surface.

3. The laminated structure according to claim 1 or 2, wherein, The buffer layer contains zirconium oxide (ZrO2) as the main component.

4. The laminated structure according to claim 1 or 2, wherein, The thickness of the buffer layer is greater than 2nm and less than 10nm.

5. The laminated structure according to claim 1 or 2, wherein, The laminated structure further includes a first electrode layer sandwiched between the orientation control film and the functional film, and a second electrode layer disposed on the functional film.

6. The layered structure according to claim 5, wherein, The first electrode layer is a single crystal film.

7. The laminated structure according to claim 1 or 2, wherein, The functional thin film is a monocrystalline film.

8. The laminated structure according to claim 1 or 2, wherein, The functional film is a piezoelectric film, and the laminated structure is a piezoelectric device.

9. The layered structure according to claim 8, wherein, The piezoelectric film comprises at least one compound selected from the group consisting of Pb(Zr,Ti)O3, BaTiO3, (Pb,La)(Zr,Ti)O3, LiNbO3, LiTaO3, (K,Na)NbO3, AlN, and ZnO as a main component.

10. Use of the laminated structure as described in claim 1 or 2 for a piezoelectric device.

11. An apparatus for manufacturing a laminated structure, wherein the laminated structure is the laminated structure according to claim 1 or 2, wherein, The manufacturing apparatus for the laminated structure includes a vacuum transport device and a multi-chamber assembly with a vacuum evaporation device and a sputtering device.

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