Laminated structure and method for manufacturing the same, electronic device, electronic equipment, and system

Abstract

To provide a crystal formed by an epitaxial crystal growing layer having an excellent adhesion, a laminate structure containing the crystal, an electronic device, electronic equipment, and a manufacturing method capable of gaining them in an industrial advantage.SOLUTION: When a first epitaxial crystal growing layer including a cubic system crystal structure, and containing Hf and / or Zr crystal metal oxide is formed onto a crystal substrate, a second epitaxial crystal growing layer is formed onto the first epitaxial crystal growing layer, in addition, a third epitaxial crystal growing layer is formed onto the second epitaxial crystal growing layer, the formation of the first epitaxial crystal growing layer is performed by forming an oxide film onto the crystal substrate and forming the first epitaxial crystal growing layer by using an oxide atom in the oxide film, and thus, a volume of a crystal growing direction of the first epitaxial crystal growing layer is increased as compared with a volume at a crystal growing by 15% or more, and then, a laminate structure is manufactured.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a crystal, a layered structure, an electronic device, an electronic apparatus, and a method for manufacturing these. [Background technology]

[0002] Thin films made of lead zirconate titanate (Pb(Zr,Ti)O3) (hereinafter referred to as PZT), which has excellent piezoelectric and ferroelectric properties, are used in memory elements such as non-volatile memory (FeRAM), as well as MEMS (Micro Electro Mechanical Systems) technology such as inkjet heads and acceleration sensors, taking advantage of their ferroelectric properties.

[0003] In recent years, it has been studied to form a piezoelectric film with good piezoelectric properties on a (200)-oriented Pt film by forming a (200)-oriented ZrO2 film or the like on a (100)-oriented Si substrate (Patent Document 1). However, the adhesion and crystallinity at the interface are still not satisfactory, and there has been a need for a method to improve the adhesion and crystallinity at the interface and further improve the piezoelectric properties of the piezoelectric film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-154015 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a crystal comprising an epitaxial crystal growth layer having good adhesion, a layered structure containing the crystal, 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 into achieving the above-mentioned object, the inventors have discovered that, when a compound film is formed on a crystal substrate, an epitaxial crystal growth layer is formed using the compound elements in the oxide film, and the resulting epitaxial crystal growth layer is then used as a buffer layer, the volume expansion coefficient increases significantly in the direction of crystal growth, making it possible to easily obtain an extremely excellent functional film. They have also found that a crystal made of such an epitaxial crystal growth layer 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 crystal consisting of an epitaxial crystal growth layer having a cubic crystal structure, characterized in that the epitaxial crystal growth layer contains a crystalline metal compound of Hf and / or Zr and has a volume expansion coefficient in the crystal growth direction of 15% or more. [2] The crystal according to [1], wherein the volume expansion coefficient in the crystal growth direction relative to the volume expansion coefficient in a direction perpendicular to the crystal growth direction is less than 0.1. [3] The crystal according to [1] or [2], wherein the crystalline metal compound contains Hf. [4] The crystal according to [3], wherein the volume expansion coefficient in the crystal growth direction is 30% or more. [5] The crystal according to any one of [1] to [4], 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. [6] The crystal according to any one of [1] to [5] above, which is in the form of a film. [7] A method for manufacturing a laminated structure, comprising: forming a first epitaxial crystal growth layer on a crystal substrate, the first epitaxial crystal growth layer having a cubic crystal structure and containing a crystalline metal compound of Hf and / or Zr; forming a second epitaxial crystal growth layer on the first epitaxial crystal growth layer; and further forming a third epitaxial crystal growth layer on the second epitaxial crystal growth layer, wherein the formation of the first epitaxial crystal growth layer is carried out by forming a compound film on the crystal substrate and using a compound element in the compound film to form the first epitaxial crystal growth layer, thereby increasing the volume of the first epitaxial crystal growth layer in the crystal growth direction by 15% or more compared to the volume of the first epitaxial crystal growth layer during crystal growth. [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 crystal substrate and an epitaxial crystal growth layer, wherein the epitaxial crystal growth layer contains a crystalline metal compound of Hf and / or Zr and has a volume expansion coefficient in the crystal growth direction of 15% or more.

[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 the compound element, and / or one or more embedded layers containing the constituent metals and the compound element 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 the constituent metal of the epitaxial film and the compound element, and / or one or more embedded layers embedded in a part of the crystal substrate and containing the constituent metal of the epitaxial film and the compound element.

[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 the constituent metal of the epitaxial film and / or the crystal substrate and the compound element, and one or more embedded layers embedded in a portion of the crystal substrate and containing the constituent metal and the compound element.

[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 crystal, the layered structure, the electronic device, and the electronic equipment of the present invention include an epitaxial crystal growth layer having excellent adhesion, and the manufacturing method of the present invention has the effect of making it possible to obtain the crystal, the layered 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] FIG. 1 is a diagram showing the results of XRD measurements in Examples. [Figure 12] FIG. 1 is a diagram showing the results of XRD measurements in Examples. [Figure 13] FIG. 2 is a diagram schematically illustrating a film forming apparatus preferably used in the examples. [Figure 14] 1 shows a cross-sectional STEM image measured in an example. [Figure 15] 1 shows STEM images measured in an example. [Figure 16] 1 shows a STEM image of the buried layer measured in the example. DETAILED DESCRIPTION OF THE INVENTION

[0010] The crystal of the present invention is a crystal comprising an epitaxial crystal growth layer having a cubic crystal structure, characterized in that the epitaxial crystal growth layer contains a crystalline metal compound of Hf and / or Zr and exhibits a volume expansion coefficient of 15% or more in the crystal growth direction. The volume expansion coefficient refers to the ratio of volume expansion due to expansion of the crystal lattice in the epitaxial crystal growth layer accompanying crystal growth, expressed as a percentage, when the epitaxial crystal growth layer is used as a buffer layer, for example. In the present invention, the volume expansion coefficient in the crystal growth direction is preferably 30% or more. The crystal may be single crystal or polycrystalline. Furthermore, in the present invention, the crystal is preferably in the form of a film.

[0011] In the present invention, the crystal is a film-like crystal (hereinafter also referred to as a "crystal film") consisting of a single epitaxial crystal growth layer including a first crystal plane and a second crystal plane on the opposite side of the first crystal plane. Preferably, the first crystal plane is regularly transformed to have a constant lattice constant different from that of the second crystal plane. More preferably, the transformation is 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 from each other. It is also preferable that the lattice constant difference between the first crystal plane and the second crystal plane is within a range of 0.1% to 20%. This preferred range allows the crystal to be used as an excellent buffer layer, and not only can it improve the adhesion between the crystal film and a substrate or a crystal film of a different composition formed on the crystal film by crystal growth, and the crystallinity of the crystal film, but it can also improve the properties of the crystal film as a functional film.

[0012] In the present invention, the epitaxial crystal growth layer typically contains a crystalline metal compound of Hf and / or Zr, but may also contain one or more other d-block metals. In the present invention, the crystalline metal compound preferably contains Hf. This preferred range makes it easier to increase the volume of the epitaxial crystal growth layer in the crystal growth direction by 30% or more compared to the volume at the time of crystal growth. In the present invention, the crystalline metal 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. This preferred mixed crystal not only enhances the stress relaxation effect of the buffer layer, but also enhances the film quality and functional properties of the crystal film.

[0013] The method for manufacturing the laminated structure is not particularly limited, but is preferably a method for manufacturing a laminated structure in which a first epitaxial crystal growth layer having a cubic crystal structure and containing a crystalline metal compound of Hf and / or Zr is formed on a crystal substrate, a second epitaxial crystal growth layer is formed on the first epitaxial crystal growth layer, and a third epitaxial crystal growth layer is further formed on the second epitaxial crystal growth layer, in which the formation of the first epitaxial crystal growth layer is carried out by forming a compound film on the crystal substrate and using the compound elements in the compound film to form the first epitaxial crystal growth layer, thereby increasing the volume of the first epitaxial crystal growth layer (hereinafter also referred to as "epitaxial layer" or "epitaxial film") in the crystal growth direction by 15% or more compared to the volume of the first epitaxial crystal growth layer during crystal growth, and such a manufacturing method is also encompassed by the present invention. This manufacturing method can easily produce crystals in which the ratio of the volume expansion coefficient in the crystal growth direction to the volume expansion coefficient in the direction perpendicular to the crystal growth direction is less than 0.1 compared to the volume expansion coefficient during crystal growth. The crystalline metal compound may also be a known compound, such as an oxide, nitride, oxynitride, sulfide, oxysulfide, boride, oxyboride, carbide, oxycarbide, borocarbide, boronitride, borosulfide, carbonitride, carbosulfide, or carboboride. In the present invention, an oxide or nitride can be used as a buffer layer, for example, to achieve better stress relaxation and warpage reduction during heteroepitaxial growth. In the present invention, the crystalline metal compound is preferably a crystalline oxide, the compound film is preferably an oxide film, and the compound element is preferably oxygen, which is preferable because it can further improve electrical properties (particularly the interface between the conductive layer and the insulating layer). In the present invention, the crystalline metal compound is preferably a crystalline metal oxide, the compound film is preferably an oxide film, and the compound element is preferably oxygen. Also, in the present invention, the crystalline metal compound is preferably a crystalline nitride, the compound film is preferably a nitride film, and the compound element is preferably nitrogen.

[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 compound 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 above-mentioned stack using oxygen atoms in the oxide film and then deposit the epitaxial film using oxygen gas, which results in a superior film formation rate. Furthermore, by forming the film in this manner, it is possible to easily obtain a stacked structure in which an epitaxial film containing a crystalline compound is deposited on a crystal substrate, and the stacked structure has, between the crystal substrate and the epitaxial film, an amorphous thin film containing a constituent metal of the epitaxial film and / or the crystal substrate and a compound element of the crystalline compound, and / or one or more buried layers embedded in a portion of the crystal substrate and containing the constituent metal and the compound element. Furthermore, in the present invention, it is preferable to have, between the crystal substrate and the epitaxial film, an amorphous thin film containing a constituent metal of the epitaxial film and a compound element of the crystalline compound, and / or one or more buried layers embedded in a portion of the crystal substrate and containing the constituent metal and the compound element, because this improves the crystallinity of the epitaxial film. Furthermore, in the present invention, it is preferable to have an amorphous thin film between the crystal substrate and the epitaxial film, the amorphous thin film containing the constituent metals of the epitaxial film and / or the crystal substrate and the compound element of the crystalline compound, and one or more buried layers embedded in a portion of the crystal substrate and containing the constituent metals and the compound element, since this further improves the functionality of the epitaxial film. Furthermore, in the present invention, it is preferable that the constituent metals contain Hf, since this further promotes stress relaxation and further enables multi-stage stress relaxation. Furthermore, in the present invention, it is preferable that the amorphous thin film have a thickness of 1 nm to 10 nm, since this further improves the crystallinity of the epitaxial film. An amorphous thin film with 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 have a cross-sectional shape that is approximately an inverted triangle, since this further improves the functionality of the epitaxial film. These preferred stacked structures are:This can be easily achieved by appropriately adjusting the thickness of the oxide film and the timing of introducing the oxygen gas.

[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 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 the crystalline metal oxide was formed as the crystal 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, zirconium 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 volume expansion coefficient of the crystalline metal oxide single crystal film of the obtained laminate structure was measured and found to be 30% or more. Furthermore, the ratio of the volume expansion coefficient in the crystal growth direction to the volume expansion coefficient in the direction perpendicular to the crystal growth direction was less than 0.1. For reference, the crystal substrate of the laminate structure, the crystalline metal oxide single crystal film, and the conductive film, all prepared in the same manner as in Example 1, were analyzed for their crystallinity using an X-ray diffractometer. Figure 11 shows the results of the XRD analysis. As is clear from Figure 11, 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 each measured using an X-ray diffractometer. Figure 12 shows the results of the XRD measurement. As is clear from Figure 12, 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. 13. The film-forming apparatus in Fig. 13 includes at least metal sources 1101a-1101b in a crucible, earths 1102a-1102h, ICP electrodes 1103a-1103b, cut filters 1104a-1104b, DC power supplies 1105a-1105b, RF power supplies 1106a-1106b, lamps 1107a-1107b, an Ar source 1108, a reactive gas source 1109, a power supply 1110, a substrate holder 1111, a substrate 1112, a cut filter 1113, an ICP ring 1114, a vacuum chamber 1115, and a rotation shaft 1116. The ICP electrodes 1103a-1103b in Fig. 13 have a generally concave curved or parabolic shape curved toward the center of the substrate 1112.

[0037] As shown in FIG. 13, a substrate 1112 is secured on a substrate holder 1111. Next, a power supply 1110 and a rotation mechanism (not shown) are used to rotate a rotation shaft 1116, thereby rotating the substrate 1112. The substrate 1112 is heated by lamps 1107a-1107b, and a vacuum chamber 1115 is evacuated to a vacuum or reduced pressure by a vacuum pump (not shown). Thereafter, Ar gas is introduced from an Ar source 1108 into the vacuum chamber 1115, and argon plasma is formed on the substrate 1112 using DC power supplies 1105a-1105b, RF power supplies 1106a-1106b, ICP electrodes 1103a-1103b, cut filters 1104a-1104b, and earths 1102a-1102h, thereby cleaning the surface of the substrate 1112.

[0038] Ar gas is introduced into the vacuum chamber 1115, and a reactive gas is introduced using a reactive gas source 1109. At this time, lamps 1107a to 1107b, 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 a layered structure of a single-crystal film of a crystalline metal oxide layered on a crystal substrate obtained in the same manner as in Example 1. The results are shown in FIGS. 14 to 16. From FIG. 14, it can be seen that a buried layer 1004 is formed between the crystal substrate 1011 and the epitaxial layer 1001, and amorphous layers 1002 and 1003 are also formed. From FIG. 15, it can be seen that the first amorphous layer 1002 on the crystal substrate 1011 contains Si of the crystal substrate and Zr, a constituent metal of the epitaxial layer 1001. From FIG. 16, it can be seen that the buried layer 1004 has a substantially inverted triangular cross section 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, etc.).

[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 crystal and layered structure of the present invention can be used in a variety of applications, but are particularly suitable for use as buffer layers and crystal growth substrates, for example, in the manufacture of electronic devices for 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 1001 epitaxial layer 1002 First amorphous layer 1003 Second amorphous layer 1004 buried layer 1011 board 1101a~101b Metal source 1102a~102j Earth 1103a~103b ICP electrode 1104a~104b Cut Filter 1105a~105b DC power supply 1106a~106b RF power supply 1107a~107b Lamps 1108 Ar source 1109 Reactive Gas Source 1110 Power supply 1111 PCB holder 1112 board 1113 Cut Filter 1114 ICP Ring 1115 Vacuum chamber 1116 Rotation axis

Claims

1. A method for manufacturing a stacked structure, comprising: forming a first epitaxial crystal growth layer on a crystal substrate; the first epitaxial crystal growth layer having a cubic crystal structure and containing a crystalline metal compound of Hf and / or Zr; forming a second epitaxial crystal growth layer on the first epitaxial crystal growth layer; and further forming a third epitaxial crystal growth layer on the second epitaxial crystal growth layer, wherein the formation of the first epitaxial crystal growth layer is carried out by forming a compound film on the crystal substrate and using a compound element in the compound film to form the first epitaxial crystal growth layer, thereby increasing the volume of the first epitaxial crystal growth layer in the crystal growth direction by 15% or more compared to the volume of the first epitaxial crystal growth layer during crystal growth.

2. 2. The method for producing a laminated structure according to claim 1, wherein after using the compound element in the compound film, a compound element gas is introduced and the first epitaxial crystal growth layer is formed in the presence of the compound element gas.

3. A laminated structure including at least a crystal substrate and an epitaxial crystal growth layer, wherein the epitaxial crystal growth layer contains a crystalline metal compound of Hf and / or Zr and has a volume expansion coefficient in the crystal growth direction of 15% or more; Between the crystal substrate and the epitaxial crystal growth layer, there is provided one or more amorphous thin films containing a constituent metal of the epitaxial crystal growth layer and / or the crystal substrate and / or one or more embedded layers containing the constituent metal embedded in a part of the crystal substrate, The buried layer has a cross-sectional shape of a substantially inverted triangle.

4. A laminated structure including at least a crystal substrate and an epitaxial crystal growth layer, wherein the epitaxial crystal growth layer contains a crystalline metal compound of Hf and / or Zr and has a volume expansion coefficient in the crystal growth direction of 15% or more; A laminated structure having, between the crystal substrate and the epitaxial crystal growth layer, an amorphous thin film containing a constituent metal of the epitaxial crystal growth layer and / or one or more buried layers embedded in a portion of the crystal substrate and containing a constituent metal of the epitaxial crystal growth layer.

5. A laminated structure including at least a crystal substrate and an epitaxial crystal growth layer, wherein the epitaxial crystal growth layer contains a crystalline metal compound of Hf and / or Zr and has a volume expansion coefficient in the crystal growth direction of 15% or more; A laminated structure having, between the crystal substrate and the epitaxial crystal growth layer, an amorphous thin film containing a constituent metal of the epitaxial crystal growth layer and / or the crystal substrate, and one or more buried layers embedded in a portion of the crystal substrate and containing the constituent metal.

6. 6. The laminate structure according to claim 3, wherein the crystalline metal compound contains Hf.

7. The laminate structure according to any one of claims 3 to 5, 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.

8. 6. The laminated structure according to claim 3, wherein the epitaxial crystal growth layer constitutes a part or the whole of a buffer layer and serves as a crystal growth substrate.

9. 6. The laminate structure according to claim 3, wherein the constituent metals include Hf.

10. 6. The laminated structure according to claim 3, wherein the amorphous thin film has a thickness of 1 nm to 10 nm.

11. 6. The laminated structure according to claim 4, wherein the buried layer has a cross-sectional shape of a substantially inverted triangle.

12. An electronic device, an electronic equipment, or a system including a laminate structure, wherein the laminate structure is the laminate structure according to any one of claims 3 to 5.

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