Shape memory material, laminated structure and method for manufacturing the same, electronic device, electronic equipment and system

Abstract

To provide: a new shape memory material consisting of a compound excellent in corrosion resistance; a laminated structure including the shape memory material; an electronic device; an electronic apparatus; and a method for manufacturing them, capable of industrially advantageously obtaining them.SOLUTION: When forming at least a compound film on a crystal substrate, laminating an epitaxial film including a crystalline compound and laminating a second epitaxial film having a composition different from that of the epitaxial film directly or through the other layer on the epitaxial film, the lamination of the epitaxial film performed by forming the epitaxial film using compound elements in the compound film can obtain a film-like shape memory material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shape memory material, a laminate structure, an electronic device, an electronic apparatus, and a method for manufacturing these. [Background technology]

[0002] Shape memory materials (also called superelastic materials) that exhibit shape memory or superelastic phenomena (also called pseudoelastic phenomena) have been known, and their practical application is being promoted in various industrial, medical, and other fields to utilize their unique functions. Shape memory materials include shape memory alloys (SMA) and shape memory polymers (SMP). Known examples of SMAs include nitinol, an alloy of nickel and titanium (Patent Document 1). Nitinol has excellent shape memory effects and superelastic properties, and is used in medical guide wires, eyeglasses, and the like. Known SMPs include 1) polyurethane-based shape memory polymers containing ionic or mesogenic components, and 2) polyethylene terephthalate-polyethylene oxide (PET-PEO) block copolymers cross-linked with maleic anhydride.

[0003] However, conventional shape memory materials have problems such as oxidation degradation and temperature dependency. In recent years, shape memory materials with oxidation resistance have been investigated to solve these problems (for example, Patent Document 2), but they are still not satisfactory, and shape memory materials with excellent corrosion resistance, such as oxidation resistance, have been long awaited. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-097790 [Patent Document 2] International Publication No. WO2018-047787 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a novel shape memory material made of an oxide having excellent corrosion resistance, a laminate structure, an electronic device, an electronic equipment, and a manufacturing method by which these can be obtained in an industrially advantageous manner. [Means for solving the problem]

[0006] As a result of intensive research to achieve the above-mentioned object, the present inventors have found that, when at least a compound film is formed on a crystal substrate, an epitaxial film containing a crystalline oxide is then laminated, and a second epitaxial film having a composition different from that of the first epitaxial film is laminated on the first epitaxial film, either directly or via another layer, by forming the epitaxial film using a compound element in the compound film, a regular transformation matching the lattice constant of the second epitaxial film occurs without dislocations or slip deformation, and the epitaxial film, although made of an oxide, exhibits a shape memory phenomenon or a superelastic phenomenon, and have discovered that such an epitaxial film is a novel shape memory material that can solve all of the above-mentioned conventional problems at once. Furthermore, after obtaining the above findings, the present inventors conducted further studies and completed the present invention.

[0007] That is, the present invention relates to the following inventions. [1] A shape memory material in the form of a film, characterized in that it is made of a crystalline metal oxide. [2] The shape memory material according to [1], wherein the crystalline metal compound is a crystalline metal oxide. [3] The shape memory material according to [1] or [2], wherein the crystalline metal compound contains Hf. [4] The shape memory material according to any one of [1] to [3], wherein the crystalline metal compound contains, among its constituent metals, 50 atomic % or more of Hf and / or Zr, and 0.1 atomic % to 50 atomic % of one or more metals selected from Al, Ti, Y and Ce. [5] The shape memory material according to any one of [1] to [4] above, which has a transformation temperature of 350°C to 1000°C. [6] The shape memory material according to any one of [1] to [5], which exhibits superelasticity of 10% or more when deformed at a transformation temperature or higher. [7] A method for manufacturing a laminated structure, which comprises forming at least a compound film on a crystal substrate, and then laminating an epitaxial film containing a crystalline compound, wherein the epitaxial film is formed by using a compound element in the compound film to form the epitaxial film, thereby obtaining a film-like shape memory material. [8] The manufacturing method according to [7], wherein after using the compound element in the compound film, a compound element gas is introduced to form the epitaxial film in the presence of the compound element gas. [9] A laminated structure including at least a crystalline substrate and an epitaxial film, wherein the epitaxial film contains a shape memory material made of a crystalline metal compound.

[10] The layered structure according to [9], wherein the epitaxial film constitutes a part or all of a buffer layer and is a substrate for crystal growth.

[11] A piezoelectric element including a laminated structure, characterized in that the laminated structure is the laminated structure according to [9] or

[10] above.

[12] A method for manufacturing a piezoelectric element using a laminated structure, characterized in that the laminated structure is the laminated structure according to [9] or

[10] above.

[13] An electronic device including a laminated structure, characterized in that the laminated structure is the laminated structure according to [9] or

[10] above.

[14] The electronic device according to

[13] above, which is a piezoelectric device.

[15] A method for manufacturing an electronic device using a laminated structure, characterized in that the laminated structure is the laminated structure described in [9] or

[10] above.

[16] An electronic device including an electronic device, characterized in that the electronic device is the electronic device described in

[14] or

[15] above.

[17] A method for manufacturing an electronic device using a laminated structure or an electronic device, wherein the laminated structure is the laminated structure described in [9] or

[10] above, and the electronic device is the electronic device described in

[14] or

[15] above.

[18] A system including an electronic device, wherein the electronic device is the electronic device described in

[16] .

[19] The laminated structure according to [9], wherein, between the crystal substrate and the epitaxial film, there is provided one or more amorphous thin films containing the constituent metals of the epitaxial film and / or the crystal substrate and / or embedded layers containing the constituent metals embedded in a portion of the crystal substrate.

[20] The laminated structure according to

[19] , which has, between the crystal substrate and the epitaxial film, an amorphous thin film containing a constituent metal of the epitaxial film and / or one or more buried layers embedded in a portion of the crystal substrate and containing a constituent metal of the epitaxial film.

[21] The laminated structure according to

[19] , having an amorphous thin film between the crystal substrate and the epitaxial film, the amorphous thin film containing a constituent metal of the epitaxial film and / or the crystal substrate, and one or more embedded layers embedded in a portion of the crystal substrate and containing the constituent metal.

[22] The laminate structure according to any one of

[19] to

[21] , wherein the constituent metal contains Hf.

[23] The laminate structure according to any one of

[19] to

[22] above, wherein the amorphous thin film has a thickness of 1 nm to 10 nm.

[24] The multilayer structure according to any one of

[19] to

[23] , wherein the embedded layer has a cross-sectional shape of a substantially inverted triangle.

[25] An electronic device, an electronic equipment, or a system including a laminated structure, characterized in that the laminated structure is the laminated structure according to any one of

[19] to

[24] . [Effects of the Invention]

[0008] The shape memory material, the laminated structure, the electronic device, and the electronic equipment of the present invention contain an epitaxial film having excellent corrosion resistance, and the manufacturing method of the present invention has the effect of making it possible to obtain the shape memory material, the laminated structure, the electronic device, and the electronic equipment in an industrially advantageous manner. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram schematically illustrating an example of a preferred embodiment of the laminated structure of the present invention. [Figure 2] FIG. 2 is a diagram schematically illustrating an example of another preferred embodiment of the laminated structure of the present invention. [Figure 3] 1A and 1B are diagrams schematically illustrating an example of an oxide film forming step in a preferred method for producing a laminated structure of the present invention. [Figure 4] 1A and 1B are diagrams schematically illustrating an example of an epitaxial film formation step in a preferred method for producing a stacked structure of the present invention. [Figure 5] 1 shows cross-sectional STEM images observed in Examples. [Figure 6] 1 shows cross-sectional STEM images observed in Examples. [Figure 7] 1 shows STEM images observed in the examples. [Figure 8] 1 shows STEM images observed in the examples. [Figure 9] 1A and 1B are diagrams schematically illustrating a preferred example of an embodiment of a MEMS transducer according to the present invention. [Figure 10] FIG. 1 is a diagram showing an example of a cross section of a portion of a wafer provided with a piezoelectric actuator, as a suitable application example of the present invention to a fluid discharge device. [Figure 11] 1 shows cross-sectional STEM images observed in the examples, where (b) shows a bright-field (BF) STEM image of (a). [Figure 12] 1 shows the results of XRD measurements showing crystal symmetry in an example. [Figure 13] 1 shows the results of XRD measurements showing crystal symmetry in an example. [Figure 14] FIG. 2 is a diagram schematically illustrating a film forming apparatus preferably used in the examples. [Figure 15] 1 shows a cross-sectional STEM image measured in an example. [Figure 16] 1 shows STEM images measured in an example. [Figure 17] 1 shows a STEM image of the buried layer measured in the example. DETAILED DESCRIPTION OF THE INVENTION

[0010] The shape memory material of the present invention is a film-like shape memory material characterized by being composed of a crystalline compound, preferably a crystalline metal oxide. The term "shape memory material" generally refers to a material that, even if deformed below a predetermined temperature, recovers its original shape upon heating above the predetermined temperature. However, in the present invention, the term "shape memory material" refers to any material that can be partially or completely deformed and recover its shape above its transformation temperature, including superelastic materials with superelastic properties. The term "superelastic property" refers to the property of recovering to its original shape upon unloading even if the shape memory material is deformed (including bending, tension, compression, etc.) at a use temperature above the transformation temperature. In the present invention, the shape memory material preferably has a transformation temperature of 350°C or higher, more preferably 350°C to 1000°C, and most preferably 350°C to 750°C. Furthermore, in the present invention, the shape memory material preferably exhibits superelasticity of 5% or higher, more preferably 10% or higher, upon deformation above the transformation temperature. The crystalline compound is not particularly limited and may be a known crystalline compound. However, in the present invention, the crystalline compound is preferably a metal compound, and the metal of the metal compound may also be a known metal. Examples of the metal include metals containing d-block elements of the periodic table. The metal compound may also be a known compound. Examples of the compound in the crystalline compound include oxides, nitrides, oxynitrides, sulfides, oxysulfides, borides, oxyborides, carbides, oxycarbides, borocarbides, boronitrides, borosulfides, carbonitrides, carbosulfides, and carboborides. In the present invention, oxides or nitrides are preferred because they can, for example, provide better stress relaxation and warpage reduction as a buffer layer during heteroepitaxial growth, and further improve electrical properties (particularly the interface between the conductive layer and the insulating layer). Furthermore, the crystalline compound is preferably a crystalline oxide, the compound film is preferably an oxide film, and the compound element is preferably oxygen. In the present invention, the crystalline compound is preferably a crystalline nitride, the compound film is preferably a nitride film, and the compound element is preferably nitrogen.

[0011] In the present invention, the shape-memory material preferably comprises a single-layer crystalline film including a first crystal plane and a second crystal plane opposite the first crystal plane, and the first crystal plane is regularly transformed to have a constant lattice constant different from that of the second crystal plane. The transformation is more preferably a transformation resulting in a peak-valley structure. Furthermore, in the present invention, the angles formed by adjacent peaks and valleys of the peak-valley structure are preferably different, and the difference in lattice constant between the first crystal plane and the second crystal plane is preferably within a range of 0.1% to 20%. This preferred range allows the material to be used as an excellent buffer layer, and not only can it improve the adhesion between the crystalline film and a substrate or a crystalline film of a different composition formed on the crystalline film by crystal growth, but also the crystallinity of the crystalline film. This also improves the properties of the crystalline film as a functional film.

[0012] In the present invention, the crystalline film preferably contains one or more d-block elements, and also preferably contains a metal compound containing one or more metals selected from the d-block elements of the periodic table. The metal compound is not particularly limited as long as it does not impair the object of the present invention, but is preferably a metal compound containing one or more metals selected from Groups 3, 4, and 13 of the periodic table, and more preferably a metal compound containing one or more metals selected from Group 4 of the periodic table. More specifically, the metal compound is preferably a crystalline metal compound, and the crystalline metal compound preferably contains Hf and / or Zr, and more preferably contains Hf. The crystalline metal compound may contain metals other than Hf and Zr. When the crystalline metal compound contains the other metals, the crystalline compound preferably contains 50 atomic % or more of Hf and / or Zr and 0.1 atomic % to 50 atomic % of one or more metals selected from Al, Ti, Y, and Ce among its constituent metals. This preferred range facilitates the production of a shape memory material exhibiting superelasticity of 5% or more, more preferably 10% or more, upon deformation at or above its transformation temperature. Furthermore, this preferred range facilitates crystal growth and improves the quality of the crystal, particularly as a buffer layer. The crystalline structure of the crystalline film is not particularly limited, but preferably has a cubic crystalline structure. The crystalline film is preferably a single-crystal film containing the crystalline compound, and more preferably an epitaxial film.

[0013] The laminated structure of the present invention is a laminated structure including at least a crystalline substrate and an epitaxial film, characterized in that the epitaxial film contains a shape memory material made of a crystalline metal compound. The method for manufacturing the laminated structure is not particularly limited, but is preferably a method for manufacturing a laminated structure in which at least a compound film is formed on a crystal substrate, and then an epitaxial film containing a crystalline compound is laminated thereon, and the epitaxial film is laminated by forming the epitaxial film using a compound element in the compound film, thereby obtaining a film-like shape memory material, and such a manufacturing method is also included in the present invention.

[0014] Preferred embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these preferred embodiments. FIG. 1 shows a preferred example of the laminated structure, in which an epitaxial layer 3 is laminated on a crystal substrate 1 using an oxide film 2, and a second epitaxial layer 4 is further laminated on the epitaxial layer 3. In this specification, the terms "film" and "layer" may be interchangeable depending on the case or situation. Furthermore, although oxides are given as preferred examples of the laminated structure, the present invention is not limited to these preferred examples, and the present invention can also be suitably applied to various compounds such as nitrides. The laminated structure can be easily manufactured by, for example, forming an oxide film 2 of the crystal substrate 1 on the crystal substrate 1 as shown in Fig. 3, then using oxygen in the oxide film 2 to form an epitaxial film 3 made of a crystalline oxide on the crystal substrate 1 as shown in Fig. 4, and then further forming the second epitaxial film on the epitaxial film 3. In the present invention, the laminated structure may have the oxide film 2 on the crystal substrate 1, or the oxide film 2 may disappear when all the oxygen in the oxide film 2 is taken in during the formation of the epitaxial film 3. Each of these will be described in more detail below, but the present invention is not limited to these specific examples.

[0015] The crystal substrate (hereinafter simply referred to as "substrate") is not particularly limited in terms of substrate material, etc., as long as it does not impede the objectives of the present invention, and may be a known crystal substrate. It may be an organic compound or an inorganic compound. In the present invention, the crystal substrate preferably contains an inorganic compound. In the present invention, the substrate preferably has crystals on a portion or all of its surface, more preferably a crystal substrate having crystals on all or a portion of its main surface on the crystal growth side, and most preferably a crystal substrate having crystals on the entire main surface on the crystal growth side. The crystal is not particularly limited as long as it does not impede the objectives of the present invention, and the crystal structure is also not particularly limited. However, crystals of a cubic, tetragonal, trigonal, hexagonal, orthorhombic, or monoclinic system are preferred, and crystals oriented in a (100) or (200) plane are more preferred. The crystal substrate may also have an off-angle, and examples of the off-angle include an off-angle of 0.2° to 12.0°. Here, the "off-angle" refers to the angle between the substrate surface and the crystal growth surface. The shape of the substrate is not particularly limited as long as it is plate-shaped and serves as a support for the epitaxial film. It may be an insulating substrate or a semiconductor substrate. However, in the present invention, the substrate is preferably a Si substrate, more preferably a crystalline Si substrate, and most preferably a (100)-oriented crystalline Si substrate. Examples of the substrate material include Si substrates and one or more metals belonging to Groups 3 to 15 of the periodic table, or oxides of these metals. The shape of the substrate is not particularly limited and may be substantially circular (e.g., circular, elliptical, etc.) or polygonal (e.g., triangular, square, rectangular, pentagonal, hexagonal, heptagonal, octagonal, nonagonal, etc.), and various shapes can be suitably used. Furthermore, in the present invention, a large-area substrate can be used, and the use of such a large-area substrate allows for a larger area of ​​the epitaxial film.

[0016] In the present invention, the crystal substrate preferably has a flat surface. However, it is also preferable for the crystal substrate to have an uneven surface on part or all of its surface, as this can improve the quality of the crystal growth of the epitaxial film. The crystal substrate having an uneven surface may have an uneven surface consisting of concave or convex portions formed on part or all of its surface. The uneven surface is not particularly limited as long as it consists of convex or concave portions. It may be an uneven surface consisting of convex portions, an uneven surface consisting of concave portions, or an uneven surface consisting of convex and concave portions. The uneven surface may be formed of regular convex or concave portions, or irregular convex or concave portions. In the present invention, the uneven surface is preferably formed periodically, and more preferably in a periodic and regularly patterned form. The shape of the uneven surface is not particularly limited, and examples thereof include stripes, dots, meshes, and random patterns. In the present invention, a dot or stripe pattern is preferred, and a dot pattern is more preferred. Furthermore, when the concave-convex portions are patterned periodically and regularly, the pattern shape of the concave-convex portions is preferably a polygonal shape such as a triangle, a quadrangle (e.g., a square, a rectangle, or a trapezoid), a pentagon, or a hexagon, or a circle, an ellipse, or the like. When the concave-convex portions are formed in a dotted pattern, the lattice shape of the dots is preferably a lattice shape such as a square lattice, an oblique lattice, a triangular lattice, or a hexagonal lattice, and more preferably a triangular lattice. The cross-sectional shape of the concave or convex portions of the concave-convex portions is not particularly limited, but examples thereof include a U-shape, an inverted U-shape, a wave shape, or a polygonal shape such as a triangle, a quadrangle (e.g., a square, a rectangle, or a trapezoid), a pentagon, or a hexagon. The thickness of the crystal substrate is not particularly limited, but is preferably 50 to 2000 μm, and more preferably 100 to 1000 μm.

[0017] The oxide film is not particularly limited as long as it is an oxide film that can incorporate oxygen atoms into the epitaxial film, and typically contains an oxide material. The oxide material is not particularly limited as long as it does not impede the objectives of the present invention, and may be a known oxide material. Examples of the oxide material include metal or semimetal oxides. In the present invention, the oxide film preferably contains the oxide material of the crystal substrate. Examples of such oxide films include a thermally oxidized film or a natural oxide film of the crystal substrate. In addition, in the present invention, the oxide film may be a sacrificial layer that is partially or completely lost or destroyed when oxygen atoms are absorbed. In the present invention, the oxide film is preferably an oxygen-supplying sacrificial layer that absorbs oxygen atoms and loses the oxide film itself during the crystal growth of the epitaxial layer. In addition, the oxide film may be patterned, for example, in a striped, dotted, mesh, or random pattern. The thickness of the oxide film is not particularly limited, but is preferably greater than 1 nm and less than 100 nm.

[0018] The epitaxial layer preferably includes an epitaxial film incorporating oxygen atoms from the oxide film. The phrase "an epitaxial film incorporating oxygen atoms from the oxide film" means that oxygen atoms from the oxide film are taken by the epitaxial film during the crystal growth of the epitaxial film. The epitaxial film is not particularly limited as long as it is an epitaxial film that has grown by incorporating oxygen atoms from the oxide film. In the present invention, however, it preferably includes a metal or a metal oxide. Suitable examples of the metal include one or more metals belonging to the d-block of the periodic table. Suitable examples of the metal oxide include oxides of one or more metals belonging to the d-block of the periodic table. In the present invention, the epitaxial film preferably includes a dielectric. Furthermore, in the present invention, the epitaxial film preferably includes a neutron absorbing material. The neutron absorber may be a known neutron absorber. In the present invention, by using such a neutron absorber to capture oxygen from the oxide film, it is possible to improve adhesion, crystallinity, and other functional film properties. A suitable example of the neutron absorber is hafnium (Hf). The epitaxial layer may be composed of one or more types of epitaxial films. In the present invention, it is preferable that the epitaxial layer includes two or more types of epitaxial films. More specifically, it is preferable that a second epitaxial film having a different composition from the epitaxial film is stacked on the epitaxial film, either directly or via another layer. By stacking in this manner, the first epitaxial layer (hereinafter also referred to as "first epitaxial layer") can be regularly transformed at the interface between the epitaxial layer and the second epitaxial layer so that the lattice constant thereof becomes approximately the same as that of the second epitaxial layer.A preferred example of the regular transformation is a transformation in which the shape is transformed into a peak-valley structure. In the present invention, the angles formed by adjacent peaks and valleys in the peak-valley structure are preferably different, and more preferably, each angle is within the range of 30° to 45°. The epitaxial layer typically has a first crystal plane and a second crystal plane. The transformation can cause a difference in lattice constant between the first crystal plane and the second crystal plane. Therefore, the difference in lattice constant between the first crystal plane and the second crystal plane is preferably within the range of 0.1% to 20%. In the present invention, the first crystal plane can be substantially identical to the lattice constant of the second epitaxial film, making it easy to achieve a difference in lattice constant between the first epitaxial layer and the second epitaxial layer within the range of 0.1% to 20%.

[0019] Furthermore, in the present invention, it is more preferable that the epitaxial film is a dielectric and the second epitaxial film is an electrode. By using the second epitaxial layer as an electrode, not only can adhesion and crystallinity at the interface be further improved, but also, for example, the characteristics of the device can be improved. Furthermore, according to the present invention, when the second epitaxial layer is made of a single crystal film of a conductive metal, a large-area defect-free film can be easily obtained, and not only the function as an electrode but also the characteristics of the device can be improved. The conductive metal is not particularly limited as long as it does not impede the object of the present invention, and examples thereof include gold, silver, platinum, palladium, silver-palladium, copper, nickel, and alloys thereof, but in the present invention, it is preferable that it contains platinum. Note that, in the present invention, according to the above-mentioned manufacturing method, a thickness of 100 nm or more can be preferably obtained. 2 A defect-free single crystal film can be obtained as an electrode with an area of ​​1000 nm or more. 2 A defect-free single crystal film can be easily obtained with this area. In addition, a single crystal film having a thickness of preferably 100 nm or more can be easily obtained as an electrode.

[0020] In the present invention, it is also preferable that a third epitaxial film and / or a fourth epitaxial film having a composition different from that of the second epitaxial film be stacked on the second epitaxial film, either directly or via another layer. Figure 2 shows a preferred example of a stacked structure in which the third epitaxial layer 5 and the fourth epitaxial layer 6 are stacked on the second epitaxial layer 4. The stacked structure of Figure 2 includes a first epitaxial layer 3 stacked on a crystal substrate 1 using an oxide film. Furthermore, a second epitaxial layer 4 is stacked on the first epitaxial layer 3, a third epitaxial layer 5 is stacked on the second epitaxial layer 4, and a fourth epitaxial layer 6 is stacked on the third epitaxial layer 5. The third epitaxial film in the third epitaxial layer is preferably a dielectric, semiconductor, or conductor, more preferably a dielectric, and most preferably a piezoelectric. The fourth epitaxial film in the fourth epitaxial layer is preferably a dielectric, semiconductor, or conductor, more preferably a dielectric, and most preferably a piezoelectric. The thickness of each of the epitaxial films is not particularly limited, but is preferably 10 nm to 100 μm, and more preferably 50 nm to 30 μm.

[0021] The laminated structure can be easily obtained by a method for manufacturing a laminated structure in which an epitaxial layer is laminated on a crystal substrate via at least an oxide film, by forming the epitaxial film using oxygen atoms in the oxide film at 350° C. to 700° C. If the temperature is in the range of 350° C. to 700° C., the oxygen atoms in the oxide film can be easily incorporated into the epitaxial film, causing crystal growth.

[0022] In the present invention, it is preferable to form the epitaxial film using oxygen atoms in the oxide film and then using oxygen gas to form the laminate. This method of film formation improves the film formation rate, etc. Furthermore, this method of film formation makes it possible to easily obtain a laminate structure in which an epitaxial layer is laminated on a crystal substrate, and the laminate structure has, between the crystal substrate and the epitaxial layer, an amorphous thin film containing a constituent metal of the epitaxial layer and / or the crystal substrate, and / or one or more buried layers embedded in a portion of the crystal substrate and containing the constituent metal. In the present invention, it is preferable for the laminate structure to have both the amorphous layer and the buried layer, since this can further improve the functionality, etc. of the epitaxial film. It is also preferable for the amorphous layer and the buried layer to each contain a constituent metal of the epitaxial layer, since this improves the crystallinity of the epitaxial film, etc. Furthermore, in the present invention, it is preferable that the constituent metals contain Hf, since this further promotes stress relaxation and enables multi-stage stress relaxation. Furthermore, in the present invention, it is preferable that the amorphous thin film has a thickness of 1 nm to 10 nm, since this can further improve the crystallinity of the epitaxial film, and an amorphous thin film of such a preferred thickness can be easily obtained by the preferred manufacturing method of the present invention. Furthermore, in the present invention, it is preferable that the buried layer has a cross-sectional shape that is approximately an inverted triangle, since this can further improve the functionality of the epitaxial film. These preferred stacked structures can be easily obtained by appropriately adjusting the thickness of the oxide film, the timing of introducing the oxygen gas, and the like.

[0023] As the lamination means used in the lamination, the deposition means for the epitaxial film is usually suitably used, and the deposition means may be a known deposition means. In the present invention, the deposition means is preferably vapor deposition or sputtering, and more preferably vapor deposition.

[0024] The crystalline film or laminate structure obtained as described above can be suitably used in electronic devices according to conventional methods. For example, various electronic devices can be constructed by connecting the laminate structure as a piezoelectric element to a power source or an electric / electronic circuit, mounting it on a circuit board, or packaging it. In the present invention, the electronic device is preferably a piezoelectric device, and can be used as a piezoelectric device in electronic devices such as inkjet printer heads, microactuators, gyroscopes, and motion sensors. Furthermore, for example, by connecting an amplifier and a rectifier circuit and packaging it, it can be used as various sensors such as magnetic sensors. It can also be applied to constant-voltage-driven memories, and, for example, by connecting a storage element and a rectifier power management circuit, it can become an energy conversion device (energy harvester) that generates power from external magnetic fields or vibrations. The energy conversion device can be incorporated into power supply systems and wearable devices (e.g., earphones / hearable devices, smart watches, smart glasses, smart contact lenses, cochlear implants, cardiac pacemakers, etc.). In the present invention, the laminated structure is preferably used in, for example, smart glasses, AR headsets, MEMS mirrors for LiDAR systems, piezoelectric MEMS ultrasonic transducers (PMUTs) for advanced medical applications, and piezo heads for commercial and industrial 3D printers.

[0025] The electronic device is suitably used in electronic devices in the usual manner, and can be applied to various electronic devices in addition to the above-mentioned electronic devices, and more specific examples of suitable electronic devices include liquid ejection heads, liquid ejection apparatuses, vibration wave motors, optical devices, vibration devices, imaging devices, piezoelectric acoustic components, and audio playback devices, audio recording devices, mobile phones, and various information terminals that have such piezoelectric acoustic components.

[0026] Furthermore, the electronic device is also applied to a system in the usual manner, and examples of such a system include a sensor system. [Example]

[0027] Example 1 The crystal growth surface side of a Si substrate (100) was treated by RIE and heated in the presence of oxygen to form a thermal oxide film. Then, without oxygen, a metal vapor deposition method was used to thermally react with oxygen in the oxide film on the Si substrate, forming a single crystal of a crystalline metal oxide on the Si substrate. Next, oxygen was introduced, the temperature was lowered, and the pressure was increased, and a single crystal film of a crystalline metal oxide was formed as a shape memory material by vapor deposition. The vapor deposition conditions for this film formation were as follows: Vapor deposition source: Hf, Zr Voltage: 3.5~4.75V Pressure: 3×10 -2 ~6×10 -2 Pa Substrate temperature: 450~700℃

[0028] Next, a platinum (Pt) metal film was formed as a conductive film on the single crystal film of the crystalline metal oxide by sputtering under the following conditions. Equipment: ULVAC sputtering equipment QAM-4 Pressure: 1.20×10 -1 Pa Target: Pt Power: 100W(DC) Thickness: 100nm Substrate temperature: 450~600℃

[0029] Next, an SRO film was formed on the conductive film by sputtering under the following conditions. Equipment: ULVAC sputtering equipment QAM-4 Power: 150W(RF) Gas: Ar Pressure: 1.8Pa Substrate temperature: 600℃ Thickness: 20nm

[0030] Next, a Pb(Zr 0.52 Ti 0.48 The O3 film (PZT film) was formed by coating under the following conditions:

[0031] Lead acetate was used as the Pb raw material, zirconyl nitrate as the Zr raw material, and titanium isopropoxide as the Ti raw material. The Pb, Zr, and Ti raw materials were mixed in a composition ratio of Pb:Zr:Ti = 100 + δ:52:48. Purified water was used as the solvent to account for the solubility of the raw materials, and acetic acid was added to control hydrolysis. Furthermore, ethanol (0.5–3.0 mol per 1 mol of PZT) containing polyvinylpyrrolidone powder was added to adjust the viscosity. Finally, an appropriate amount of 2n-butoxyethanol was added to adjust the wettability during application, preparing a sol-gel solution as the raw material solution.

[0032] Next, the prepared sol-gel solution was dropped onto a substrate and rotated at 2000 rpm for 1 minute, spin-coating the sol-gel solution onto the substrate to form a film containing the precursor. The substrate was then placed on a hot plate at 150°C, and then on a hot plate at 350°C to evaporate the solvent and dry the film. This process was repeated five times to stack five layers under the same conditions, and then heat-treated in an oxygen (O2) atmosphere at 650°C for 3 minutes to oxidize and crystallize the precursor. The above process was repeated 10 times to obtain Pb(Zr 0.52 Ti 0.48 The total thickness of the PZT film was 10 μm.

[0033] The resulting laminate structure included an epitaxial film with excellent adhesion and crystallinity. Cross-sectional STEM images of the resulting laminate structure are shown in Figures 5 and 6. Figure 6 reveals that a very high-quality laminate structure was obtained. In particular, Figure 5 reveals that a regular peak-valley structure is formed at the interface between the crystalline metal oxide single crystal film and the conductive film, with the angles between adjacent peaks and valleys varying within a range of 30° to 45°. X-ray crystal lattice images of the conductive film are shown in Figures 7 and 8. Figures 7 and 8 reveal a defect-free, large-area conductive film, demonstrating excellent electrode properties and the piezoelectric properties of the piezoelectric film laminated thereon. Conventionally, piezoelectric films formed by spin coating have had difficulty exhibiting piezoelectric properties. However, the piezoelectric film (PZT film) formed by spin coating in this example exhibited excellent piezoelectric properties.

[0034] The epitaxial films obtained as shape memory materials in the same manner as described above were evaluated for stress-induced dislocation and slip deformation using metal particles at a temperature of 500°C, which is above the transformation temperature. The evaluation results are shown in Figure 11. As is clear from Figure 11, the example exhibited superelasticity of 10% or more when deformed above the transformation temperature. No dislocation or slip deformation occurred even after deformation, demonstrating good shape memory properties. Furthermore, the crystal substrate of the laminated structure, the single crystal film of the crystalline metal oxide, and the conductive film were analyzed for their respective crystallinity using an X-ray diffractometer. Figure 12 shows the results of the XRD analysis. As is clear from Figure 12, a (Hf,Zr)O2 film and a Pt single crystal film with good crystallinity were formed on the Si crystal substrate.

[0035] Example 2 A platinum (Pt) metal film was formed as a conductive film on a single crystal film of crystalline metal nitride in the same manner as in Example 1, except that nitrogen gas was used instead of oxygen gas. The crystal substrate of the stacked structure, the single crystal film of crystalline metal nitride, and the conductive film were then each measured using an X-ray diffractometer. Figure 13 shows the results of the XRD measurement. As is clear from Figure 13, a (Hf,Zr)N film and a Pt single crystal film with good crystallinity were formed on the Si crystal substrate. Furthermore, when measured using a four-terminal method, the resulting single crystal film of crystalline metal nitride had good conductivity.

[0036] The evaporation film-forming apparatus used in Example 1 is shown in Fig. 14. The film-forming apparatus in Fig. 14 includes at least metal sources 101a-101b in a crucible, earths 102a-102h, ICP electrodes 103a-103b, cut filters 104a-104b, DC power supplies 105a-105b, RF power supplies 106a-106b, lamps 107a-107b, an Ar source 108, a reactive gas source 109, a power supply 110, a substrate holder 111, a substrate 112, a cut filter 113, an ICP ring 114, a vacuum chamber 115, and a rotation shaft 116. The ICP electrodes 103a-103b in Fig. 14 have a generally concave curved or parabolic shape curved toward the center of the substrate 112.

[0037] As shown in FIG. 14, the substrate 112 is secured on the substrate holder 111. Next, the rotary shaft 116 is rotated using the power supply 110 and a rotation mechanism (not shown), thereby rotating the substrate 112. The substrate 112 is heated by lamps 107a and 107b, and a vacuum chamber 115 is evacuated to a vacuum or reduced pressure using a vacuum pump (not shown). Thereafter, Ar gas is introduced from the Ar source 108 into the vacuum chamber 115, and argon plasma is formed on the substrate 112 using the DC power supplies 105a and 105b, the RF power supplies 106a and 106b, the ICP electrodes 103a and 103b, the cut filters 104a and 104b, and the earths 102a and 102h, thereby cleaning the surface of the substrate 112.

[0038] Ar gas is introduced into the vacuum chamber 115, and a reactive gas is introduced using a reactive gas source 109. At this time, lamps 107a to 107b, which are lamp heaters, are turned on and off alternately, thereby enabling the formation of a better quality crystal growth film.

[0039] STEM analysis was performed on the stacked structure obtained in the same manner as in Example 1. The results are shown in FIGS. 15 to 17. FIG. 15 shows that a buried layer 1004 is formed between the crystalline substrate 1011 and the epitaxial layer 1001, and that amorphous layers 1002 and 1003 are also formed. FIG. 16 shows that the first amorphous layer 1002 on the crystalline substrate 1011 contains Si from the crystalline substrate and Zr, a constituent metal of the epitaxial layer 1001. The second amorphous layer contains Si from the crystalline substrate and Hf and Zr, which are constituent metals of the epitaxial layer 1001. FIG. 17 shows that the buried layer 1004 has a cross-sectional shape that is approximately an inverted triangle and is an oxide containing Hf and Si.

[0040] (Application example) Examples of applications of the resulting laminated structure will be described in more detail below with reference to the drawings, but the present invention is not limited to these examples. In the present invention, unless otherwise specified, piezoelectric devices and the like can be manufactured from the laminated structure using known means.

[0041] 9 shows an embodiment of an acoustic MEMS transducer constituting a MEMS microphone in which the laminated structure of the present invention is preferably used. The MEMS transducer can constitute an acoustic emission device (for example, a speaker).

[0042] The MEMS microphone constructed using the acoustic MEMS transducer shown in Figure 9 is a cantilever-type MEMS microphone. It includes a Si substrate 21 having two cantilever beams 28A and 28B and a cavity 30. Each cantilever beam 28A and 28B is fixed to the substrate 21 at its respective end, with a gap 9 between the cantilever beams 8A and 8B. The cantilever beams 8A and 8B are formed, for example, by a laminated structure including multiple piezoelectric layers (PZT films) 26a and 26b, which are alternated with multiple electrode layers, namely, Pt films 24a, 24b, and 24c, and SRO films 25a, 25b, 25c, and 25d. A dielectric layer (single-crystal film of a crystalline oxide) 23 electrically insulates the cantilever beams 8A and 8B from the crystal substrate 21. In FIG. 9, a neutron absorbing material (e.g., HfO2 or its mixed crystal) is used for the dielectric layer (single crystal film of crystalline oxide) 23, which has superior adhesion to the Si substrate and crystallinity compared to when SiO2, SiN, etc. are used, and furthermore, has superior piezoelectric properties and durability.

[0043] FIG. 10 illustrates an example of a printing application for which the laminated structure of the present invention is suitable, particularly an application to a fluid ejection device that can be used in the form of an inkjet printhead. Specifically, it illustrates a cross-sectional view of a portion of a wafer equipped with a piezoelectric actuator including Pt films 34a, 34b and SRO films 35a, 35b as electrode layers and a PZT film 36 as a piezoelectric film. In addition to the piezoelectric actuator, the wafer in FIG. 10 also includes a chamber 41 for containing a fluid. The chamber 41 is configured to take in fluid from a tank (not shown) via a flow path 40. The wafer in FIG. 10 also includes a Si substrate 31 on which a dielectric layer (a single-crystal film of a crystalline oxide) 33 is provided as a first epitaxial layer, facing the chamber 41. 10, a neutron absorbing material (e.g., HfO2 or its mixed crystal) is used for the dielectric layer (single crystal film of crystalline oxide) 23, which has superior adhesion to the Si substrate and crystallinity, as well as superior piezoelectric properties and durability, compared to when SiO2, SiN, etc. are used. Note that the single crystal film of crystalline oxide 33 has, for example, a quadrangular shape in a top view (not shown), and the shape may be any of, for example, a square, a rectangle, a rectangle with rounded corners, a parallelogram, etc.

[0044] A Pt film 34a, an SRO film 35a, a piezoelectric film (PZT film) 36, an SRO film 35b, and a Pt film 34b are laminated in this order on a single-crystal film 33 of a crystalline oxide to form a piezoelectric actuator. The piezoelectric actuator further includes an insulating film 37 extending over the electrodes 34a and 35a, the piezoelectric film 36, and the electrodes 34b and 35b. The insulating film 37 includes a dielectric material used for electrical insulation. Such a dielectric material may be a known dielectric material, such as a SiO2 layer, a SiN layer, or an Al2O3 layer. The thickness of the insulating layer containing the insulating film as a constituent material is not particularly limited, but is preferably between about 10 nm and about 10 μm. Conductive paths 39 are provided on the insulating layer (insulating film) 37 and contact the electrodes 34a and 35a and the electrodes 34b and 35b, respectively, enabling selective access during use. The conductive path may be made of a known conductive material, and a suitable example of such a conductive material is aluminum (Al). A passivation layer 42 is provided on the insulating layer 37, the electrodes 34b and 35b, and the conductive path 39. The passivation layer 42 may be made of any dielectric material used for passivating the piezoelectric actuator. The dielectric material is not particularly limited and may be any known dielectric material. Suitable examples of the dielectric material include SiN and SiON (silicon oxynitrate). The thickness of the passivation layer is not particularly limited, but is preferably between approximately 0.1 μm and approximately 3 μm. A conductive pad 38 is also provided along the piezoelectric actuator and electrically connected to the conductive path 39. The passivation layer 42 functions as a barrier layer to protect the piezoelectric element from humidity and other factors. [Industrial Applicability]

[0045] The shape memory material and laminate structure of the present invention can be used for various purposes, but are particularly suitable for use as buffer layers and crystal growth substrates, and are suitable for use in the manufacture of electronic devices for, for example, electronic equipment and sensor systems. [Explanation of symbols]

[0046] 1. Crystal substrate 2. Oxide film 3 (first) epitaxial layer 4 Second epitaxial layer 5 Third epitaxial layer 6 Fourth epitaxial layer 11. Si substrate 13 Single crystal films of crystalline oxides 14 Conductive film 15 SRO membrane 16 PZT membrane 21 Crystalline substrate (Si substrate) 23 (First) epitaxial layer (single crystal film of crystalline oxide) 24a Second epitaxial layer (Pt film) 24b Sixth epitaxial layer (Pt film) 24c 10th epitaxial layer (Pt film) 25a Third epitaxial layer (SRO film) 25b Fifth epitaxial layer (SRO film) 25c Seventh epitaxial layer (SRO film) 25d 9th epitaxial layer (SRO film) 26a Fourth epitaxial layer (PZT film) 26b Eighth epitaxial layer (PZT film) 28A Cantilever Beam 28B Cantilever Beam 29 Gap 30 cavities 31 Crystal substrate (Si substrate) 33 (First) epitaxial layer (single crystal film of crystalline oxide) 34a Second epitaxial layer (Pt film) 34b Sixth epitaxial layer (Pt film) 35a Third epitaxial layer (SRO film) 35b Fifth epitaxial layer (SRO film) 36 Fourth epitaxial layer (PZT film) 37 Insulating film 38 Conductive Pad 39 Conductive Path 40 Flow path 41 Chamber 42 Passivation Layer 101a~101b Metal source 102a~102j Earth 103a~103b ICP electrode 104a~104b Cut Filter 105a~105b DC power supply 106a~106b RF power supply 107a~107b Lamps 108 Ar source 109 Reactive Gas Source 110 Power supply 111 PCB holder 112 PCB 113 Cut Filter 114 ICP Ring 115 Vacuum chamber 116 Rotation axis 1001 epitaxial layer 1002 First amorphous layer 1003 Second amorphous layer 1004 buried layer 1011 board

Claims

1. A shape memory material in the form of a film, characterized in that it is composed of a crystalline metal compound.

2. The shape memory material according to claim 1, wherein the crystalline metal compound is a crystalline metal oxide.

3. The shape memory material according to claim 1, wherein the crystalline metal compound contains Hf.

4. The shape memory material according to any one of claims 1 to 3, wherein the crystalline metal compound contains 50 atomic% or more of Hf and / or Zr among the constituent metals and contains 0.1 atomic% to 50 atomic% of one or more metals selected from Al, Ti, Y, and Ce.

5. The shape memory material according to any one of claims 1 to 3, wherein the transformation temperature is 350°C to 1000°C.

6. The shape memory material according to any one of claims 1 to 3, which exhibits superelasticity of 10% or more by deforming at a temperature equal to or higher than the transformation temperature.

7. A method for manufacturing a laminated structure in which at least a compound film is formed on a crystal substrate and then an epitaxial film containing a crystalline compound is laminated, wherein the lamination of the epitaxial film is performed by forming the epitaxial film using the compound elements in the compound film, and a shape memory material in the form of a film is obtained.

8. The method for manufacturing a laminated structure according to claim 7, wherein after using the compound elements in the compound film, a compound element gas is introduced and the epitaxial film is formed in the presence of the compound element gas.

9. A laminated structure comprising at least a crystal substrate and an epitaxial film, wherein the epitaxial film contains a shape memory material composed of a crystalline metal compound.

10. The laminated structure according to claim 9, wherein the epitaxial film constitutes part or all of a buffer layer and is a substrate for crystal growth.

11. The laminated structure according to claim 9, having an amorphous thin film containing the constituent metal of the epitaxial film and / or the crystal substrate and / or an embedded layer containing the constituent metal and embedded in part of the epitaxial film and / or the crystal substrate.

12. The laminated structure according to claim 11, having an amorphous thin film containing the constituent metal of the epitaxial film and / or an embedded layer containing the constituent metal of the epitaxial film and embedded in part of the epitaxial film and / or the crystal substrate.

13. The stacked structure according to claim 11, having, between the crystalline substrate and the epitaxial film, an amorphous thin film containing a constituent metal of the epitaxial film and / or the crystalline substrate, and an embedded layer that is embedded in part of the crystalline substrate and contains the constituent metal.

14. The stacked structure according to any one of claims 11 to 13, wherein the constituent metal contains Hf.

15. The stacked structure according to any one of claims 11 to 13, wherein the film thickness of the amorphous thin film is 1 nm to 10 nm.

16. The stacked structure according to any one of claims 11 to 13, wherein the shape of the embedded layer has a substantially inverted triangular cross-sectional shape.

17. An electronic device, electronic apparatus, or system including the stacked structure, wherein the stacked structure is the stacked structure according to any one of claims 11 to 13.

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