Laminated structure

Abstract

To provide a crystal film formed of an epitaxial film having good adhesion and crystallinity, a laminated structure including the crystal film, an electronic device, electronic equipment, and a manufacturing method capable of industrially advantageously obtaining them.SOLUTION: When a laminated structure is manufactured by forming at least a compound film on a crystal substrate, laminating an epitaxial film containing a crystalline compound, and laminating a second epitaxial film having a composition different from that of the epitaxial film directly or via another layer on the epitaxial film, the epitaxial film is formed by using a compound element in the compound film. Thus, at an interface between the epitaxial film and the second epitaxial film, the first epitaxial film is regularly transformed so as to have substantially the same lattice constant as that of the second epitaxial film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to crystalline films made of epitaxial films, multilayer structures, electronic devices, electronic equipment, and methods for manufacturing the same. [Background technology]

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

[0003] In recent years, studies have been conducted to form a piezoelectric film with good piezoelectric properties on a Pt film by creating a Pt film oriented to (200) via a ZrO2 film oriented to (200) on a Si substrate oriented to (100) (Patent Document 1). However, the adhesion and crystallinity at the interface are still not satisfactory, and there has been a strong demand for measures that can 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 Publication No. 2015-154015 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a crystalline film comprising an epitaxial film having good adhesion and crystallinity, a laminated structure including the crystalline film, an electronic device, an electronic device, and a manufacturing method that can produce these in an industrially advantageous manner. [Means for solving the problem]

[0006] The present inventors, through diligent research to achieve the above objectives, have found a method for manufacturing a laminated structure comprising forming at least a compound film on a crystalline substrate, then laminating an epitaxial film containing a crystalline compound, and further laminating a second epitaxial film having a different composition from the first epitaxial film directly or via another layer on the epitaxial film, wherein the lamination of the epitaxial films is performed by forming the epitaxial film using compound elements in the compound film, and it has been found that the first epitaxial film can be regularly transformed at the interface between the first epitaxial film and the second epitaxial film so that its lattice constant is substantially the same as that of the second epitaxial film. By regularly transforming the films in this way, a laminated structure containing epitaxial films with excellent adhesion and crystallinity can be easily obtained, even if they have different compositions. The inventors have found that such a laminated structure and method for manufacturing the same can solve the above-mentioned conventional problems all at once. Furthermore, after obtaining the above findings, the inventors conducted further studies and completed the present invention.

[0007] In other words, the present invention relates to the following invention. [1] A single layer crystalline film comprising a first crystal plane and a second crystal plane on the opposite side of the first crystal plane, characterized in that the first crystal plane is regularly transformed to have a fixed lattice constant different from that of the second crystal plane. [2] The crystalline film according to [1], wherein the transformation is a transformation in which the shape changes to a mountain-valley structure. [3] The crystal film according to [2], wherein the angles between adjacent vertices and bases of the peak-valley structure are different. [4] The crystal film according to any one of [1] to [3], wherein the difference in lattice constants between the first crystal plane and the second crystal plane is in the range of 0.1% to 20%. [5] A crystalline film according to any one of [1] to [4] above, comprising one or more elements of the d block of the periodic table. [6] A crystalline film according to any one of [1] to [5], comprising a metal compound containing one or more metals selected from the elements of block d of the periodic table. [7] A crystalline film according to any one of [1] to [6], comprising a metal compound containing one or more metals selected from Group 3, Group 4 and Group 13 of the periodic table. [8] A crystalline film according to any one of [1] to [7], comprising a metal compound containing one or more metals selected from Group 4 of the periodic table. [9] A crystalline film according to any one of the above [1] to [8] having a cubic crystal structure.

[10] The crystalline film according to any one of [1] to [9], which is a single crystal film containing a crystalline compound.

[11] A laminated structure comprising an epitaxial film laminated on a crystalline substrate, wherein the epitaxial film is a single layer crystalline film including a first crystal plane and a second crystal plane on the opposite side of 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.

[12] The laminated structure according to

[11] , wherein the crystal substrate is a crystalline Si substrate.

[13] The laminated structure according to

[11] or

[12] , wherein the epitaxial film is made in which compound elements in a compound film laminated on the crystalline substrate are incorporated into the crystalline compound.

[14] The laminated structure according to

[13] , wherein the compound film comprises the compound material of the crystalline substrate.

[15] The laminated structure according to

[13] or

[14] , wherein the thickness of the compound film is greater than 1 nm and less than 100 nm.

[16] The laminated structure according to any one of

[11] to

[15] , further comprising a second epitaxial film having a different composition from the epitaxial film, laminated on the epitaxial film directly or via another layer.

[17] The laminated structure according to

[16] , wherein the epitaxial film is a dielectric and the second epitaxial film is a single crystal film of a conductive metal.

[18] The laminated structure according to

[16] or

[17] , wherein the first crystal plane is substantially the same as the lattice constant of the second epitaxial film.

[19] The laminated structure according to any one of

[16] to

[18] , further comprising a third epitaxial film having a different composition from the epitaxial film and the second epitaxial film, laminated on the second epitaxial film, either directly or via other layers.

[20] The laminated structure according to claim 19, wherein the third epitaxial film is a piezoelectric material.

[21] A method for manufacturing a laminated structure comprising forming at least a compound film on a crystalline substrate, then laminating an epitaxial film containing a crystalline compound, and further laminating a second epitaxial film having a different composition from the first epitaxial film directly or via another layer on the first epitaxial film, characterized in that the lamination of the epitaxial films is carried out by forming the epitaxial film using compound elements in the compound film, and regularly transforming the first epitaxial film at the interface between the first epitaxial film and the second epitaxial film so that the lattice constant is substantially the same as that of the second epitaxial film.

[22] The manufacturing method according to

[21] , wherein after using the compound element in the compound film, a compound element gas is introduced and the epitaxial film is formed in the presence of the compound element gas.

[23] A piezoelectric element comprising a crystalline film or a multilayer structure, wherein the crystalline film is a crystalline film according to any one of [1] to

[10] above, and the multilayer structure is a multilayer structure according to any one of

[11] to

[20] above.

[24] A method for manufacturing a piezoelectric element using a crystalline film or a multilayer structure, characterized in that the crystalline film is a crystalline film according to any one of [1] to

[10] above, and the multilayer structure is a multilayer structure according to any one of

[11] to

[20] above.

[25] An electronic device comprising a crystalline film or a multilayer structure, wherein the crystalline film is a crystalline film according to any one of [1] to

[10] above, and the multilayer structure is a multilayer structure according to any one of

[11] to

[20] above.

[26] The electronic device described in

[25] , which is a piezoelectric device.

[27] A method for manufacturing an electronic device using a crystalline film or a multilayer structure, characterized in that the crystalline film is a crystalline film according to any one of [1] to

[10] above, and the multilayer structure is a multilayer structure according to any one of

[11] to

[20] above.

[28] Electronic equipment comprising a crystalline film, a multilayer structure, or an electronic device, wherein the crystalline film is a crystalline film according to any of [1] to

[10] , the multilayer structure is a multilayer structure according to any of

[11] to

[20] , and the electronic device is an electronic device according to

[26] or

[27] .

[29] A method for manufacturing an electronic device using a crystalline film, a multilayer structure, or an electronic device, characterized in that the crystalline film is a crystalline film according to any of [1] to

[10] , the multilayer structure is a multilayer structure according to any of

[11] to

[20] , and the electronic device is an electronic device according to

[26] or

[27] .

[30] A system including electronic equipment, wherein the electronic equipment is the electronic equipment described in

[24] .

[31] The laminated structure according to

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

[32] The laminated structure according to

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

[33] The laminated structure according to

[31] , having an amorphous thin film containing constituent metals of the epitaxial film and / or the crystal substrate between the crystal substrate and the epitaxial film, and an embedded layer that is embedded in part of the crystal substrate and contains the constituent metals.

[34] The laminated structure according to any one of

[31] to

[33] , wherein the constituent metal contains Hf.

[35] The laminated structure according to any one of

[31] to

[34] , wherein the film thickness of the amorphous thin film is 1 nm to 10 nm.

[36] The laminated structure according to any one of

[31] to

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

[37] An electronic device, electronic apparatus, or system including the laminated structure, wherein the laminated structure is the laminated structure according to any one of

[31] to

[36] . [Advantages of the Invention]

[0008] The crystal film, laminated structure, electronic device, and electronic apparatus of the present invention include an epitaxial film having good adhesion and crystallinity. According to the manufacturing method of the present invention, the crystal film, the laminated structure, the electronic device, and the electronic apparatus can be advantageously obtained industrially. [Brief Description of the Drawings]

[0009] [Figure 1] It is a diagram schematically showing an example of a preferred embodiment of the laminated structure of the present invention. [Figure 2] It is a diagram schematically showing an example of another preferred embodiment of the laminated structure of the present invention. [Figure 3] It is a diagram schematically showing an example of an oxide film formation step of a preferred manufacturing method of the laminated structure of the present invention. [Figure 4] It is a diagram schematically showing an example of an epitaxial film formation step of a preferred manufacturing method of the laminated structure of the present invention. [Figure 5] It shows a cross-sectional STEM image observed in the examples. [Figure 6] The cross-sectional STEM images observed in the example are shown. [Figure 7] The STEM images observed in the example are shown. [Figure 8] The STEM images observed in the example are shown. [Figure 9] This figure schematically shows a preferred example of an embodiment of the MEMS transducer in the present invention. [Figure 10] As a suitable application example to the fluid discharge device of the present invention, this figure schematically shows an example of a cross-sectional view of a part of a wafer equipped with a piezoelectric actuator. [Figure 11] These are the XRD measurement results showing the crystal symmetry in the example. [Figure 12] These are the XRD measurement results showing the crystal symmetry in the example. [Figure 13] This figure schematically shows a film deposition apparatus preferably used in the examples. [Figure 14] The cross-sectional STEM images measured in the example are shown. [Figure 15] The STEM images measured in the example are shown. [Figure 16] The STEM image of the embedded layer measured in the example is shown. [Modes for carrying out the invention]

[0010] The crystalline film of the present invention is a single-layer crystalline film including a first crystal plane and a second crystal plane on the opposite side of the first crystal plane, characterized in that the first crystal plane is regularly transformed to have a fixed lattice constant different from that of the second crystal plane.

[0011] In the present invention, it is preferable that the transformation is one in which the shape changes to a peak-and-valley structure. Furthermore, in the present invention, it is preferable that the angles between adjacent vertices and bases of the peak-and-valley structure are different, and it is also preferable that the difference in lattice constants between the first crystal plane and the second crystal plane is within the range of 0.1% to 20%. Such a preferred range not only improves the adhesion between the crystal film and the substrate or a crystal film of a different composition provided on the crystal film by crystal growth, and improves the crystallinity of the crystal film, but also improves the properties of the crystal film as a functional film.

[0012] Furthermore, in the present invention, the crystalline film preferably contains one or more elements from block d of the periodic table, and preferably contains a metal compound containing one or more metals selected from the elements from block d of the periodic table. The metal compound is not particularly limited as long as it does not hinder the objective of the present invention, but it 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. Furthermore, the crystal structure of the crystalline film is not particularly limited, but it is preferably a cubic crystal structure. The crystalline film is preferably a single crystal film containing a crystalline compound, and is also preferably an epitaxial film.

[0013] The laminated structure of the present invention is a laminated structure in which an epitaxial film is laminated on a crystalline substrate, wherein the epitaxial film is a single layer crystalline film including a first crystal plane and a second crystal plane on the opposite side of the first crystal plane, and the first crystal plane is regularly transformed to have a certain lattice constant different from that of the second crystal plane. The crystalline compound is not particularly limited and may be a known crystalline compound, but in the present invention, it is preferable that the crystalline compound is a metallic compound, and the metal of the metallic compound may also be a known metal. Examples of the metal include metals containing elements of block d of the periodic table. The metal compound may also be a known compound. Examples of compounds in the crystalline compound include oxides, nitrides, oxynitrides, sulfides, oxysulfides, borides, oxyborides, carbides, oxycarbides, bocarbides, bonitrides, borosulfides, carbonitrides, carbonusulfides, or carbonoborides. However, in the present invention, oxides or nitrides are preferred because they can provide superior stress relaxation and warping reduction in heteroepitaxial growth as a buffer layer, and further improve electrical properties (especially 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. The method for manufacturing the laminated structure is not particularly limited, but it is a method for manufacturing a laminated structure in which at least a compound film is formed on a crystalline substrate, then an epitaxial film containing a crystalline compound is laminated, and further, a second epitaxial film having a different composition from the first epitaxial film is laminated on the first epitaxial film, either directly or via another layer, wherein the lamination of the epitaxial films is carried out by forming the epitaxial film using the compound elements in the compound film, and the first epitaxial film is regularly transformed at the interface between the first epitaxial film and the second epitaxial film so that the lattice constant is substantially the same as that of the second epitaxial film, 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. Figure 1 shows a preferred example of the laminated structure, in which an epitaxial layer 3 is laminated on a crystalline 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 interchanged depending on the case or situation. Furthermore, although an example of an oxide is given as a preferred example of the laminated structure, the present invention is not limited to these preferred examples, and the present invention can be suitably applied to various compounds such as nitrides. The laminated structure can be easily manufactured, for example, by forming an oxide film 2 on a crystalline substrate 1, as shown in Figure 3, then using the oxygen in the oxide film 2 to form an epitaxial film 3 made of crystalline oxide on the crystalline substrate 1, as shown in Figure 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 crystalline substrate 1, but the oxide film 2 may disappear when all the oxygen in the oxide film 2 is incorporated during the formation of the epitaxial film 3. The present invention will be described in more detail below, but the present invention is not limited to these specific examples.

[0015] The crystalline substrate (hereinafter also simply referred to as "substrate") is not particularly limited as long as it does not hinder the objectives of the present invention, and may be a known crystalline substrate. It may be an organic compound or an inorganic compound. In the present invention, it is preferable that the crystalline substrate contains an inorganic compound. In the present invention, it is preferable that the substrate has crystals on part or all of its surface, more preferably that it is a crystalline substrate having crystals on all or part of the main surface on the crystal growth side, and most preferably that it is a crystalline substrate having crystals on all of the main surface on the crystal growth side. The crystal is not particularly limited as long as it does not hinder the objectives of the present invention, and the crystal structure is not particularly limited, but it is preferable that it is a cubic, tetragonal, trigonal, hexagonal, orthorhombic, or monoclinic crystal, and more preferably that it is a crystal oriented to (100) or (200). The crystalline substrate may also have an off-angle, and examples of the off-angle include an off-angle of 0.2° to 12.0°. Here, "off-angle" refers to the angle between the substrate surface and the crystal growth surface. The substrate shape 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, but in the present invention, the substrate is preferably a Si substrate, more preferably a crystalline Si substrate, and most preferably a crystalline Si substrate oriented to (100). Examples of the substrate material include, in addition to a Si substrate, 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 by using such a large-area substrate, the area of ​​the epitaxial film can be increased.

[0016] Furthermore, in the present invention, it is preferable that the crystal substrate has a flat surface, but it is also preferable that the crystal substrate has an uneven shape on part or all of its surface, as this can improve the quality of crystal growth of the epitaxial film. The crystal substrate having the uneven shape only needs to have an uneven portion consisting of recesses or protrusions on part or all of its surface, and the uneven portion is not particularly limited as long as it consists of protrusions or recesses, and may be an uneven portion consisting of protrusions, an uneven portion consisting of recesses, or an uneven portion consisting of both protrusions and recesses. In addition, the uneven portion may be formed from regular protrusions or recesses, or from irregular protrusions or recesses. In the present invention, it is preferable that the uneven portion is formed periodically, and more preferably that it is patterned periodically and regularly. The shape of the uneven portion is not particularly limited, and examples include stripe-like, dot-like, mesh-like, or random-like, but in the present invention, dot-like or stripe-like is preferred, and dot-like is more preferred. Furthermore, if the uneven surfaces are patterned periodically and regularly, it is preferable that the pattern shape of the uneven surfaces be a polygonal shape such as a triangle, quadrilateral (e.g., square, rectangle, or trapezoid), pentagon or hexagon, circular, or elliptical. When the uneven surfaces are formed in a dot shape, it is preferable that the lattice shape of the dots be a grid shape such as a square grid, rhombic grid, triangular grid, or hexagonal grid, and more preferably a triangular grid. The cross-sectional shape of the recesses or protrusions of the uneven surfaces is not particularly limited, but examples include a U-shape, inverted U-shape, wave shape, or a polygonal shape such as a triangle, quadrilateral (e.g., square, rectangle, or trapezoid), pentagon or 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 usually contains an oxidizing material. The oxidizing material is not particularly limited as long as it does not hinder the objective of the present invention, and may be a known oxidizing material. Examples of the oxidizing material include oxides of metals or metalloids. In the present invention, it is preferable that the oxide film contains an oxidizing material of the crystal substrate, and examples of such oxide films include the thermal oxide film of the crystal substrate and the native oxide film. Furthermore, in the present invention, the oxide film may be a sacrificial layer in which part or all of the film disappears or is destroyed when oxygen atoms are incorporated, and in the present invention, it is preferable that the oxide film is an oxygen-supplying sacrificial layer in which oxygen atoms are incorporated during the crystal growth of the epitaxial layer and the oxide film itself disappears. Furthermore, the oxide film may be patterned, for example, it may be patterned in the shape of stripes, dots, mesh, or random shapes. 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 into which oxygen atoms from the oxide film are incorporated. Note that "an epitaxial film into which oxygen atoms from the oxide film are incorporated" means that during the crystal growth of the epitaxial film, oxygen atoms from the oxide film were removed by the epitaxial film. The epitaxial film is not particularly limited as long as it is an epitaxial film grown by incorporating oxygen atoms from the oxide film, but in the present invention, it is preferable that it includes a metal or a metal oxide. Suitable metals include, for example, one or more metals belonging to block d of the periodic table. Suitable metal oxides include, for example, oxides of one or more metals belonging to block d of the periodic table. In the present invention, it is preferable that the epitaxial film includes a dielectric. Furthermore, in the present invention, it is preferable that the epitaxial film includes a neutron absorber. The neutron absorber may be a known neutron absorber, and in the present invention, by using such a neutron absorber to incorporate oxygen into the oxide film, the adhesion, crystallinity, and other properties of the functional film can be improved. For example, hafnium (Hf) is a suitable example of the neutron absorber. The epitaxial layer may be composed of one or more epitaxial films, and in the present invention, it is preferable that the epitaxial layer contains two or more of the epitaxial films. More specifically, for example, it is preferable that a second epitaxial film having a different composition from the epitaxial film is laminated on the epitaxial film, either directly or via another layer. By stacking in this manner, the first epitaxial layer can be regularly transformed at the interface between the epitaxial layer and the second epitaxial layer, so that the lattice constant of the first epitaxial layer (hereinafter also referred to as "the first epitaxial layer") becomes approximately the same as that of the second epitaxial layer.As an example of the aforementioned regular transformation, a transformation in which the shape changes to a peak-valley structure is a suitable example. In the present invention, it is preferable that the angles between adjacent vertices and bases of the peak-valley structure are different, and it is more preferable that the angles are within the range of 30° to 45°. Here, the epitaxial layer usually has a first crystal plane and a second crystal plane, but the transformation may cause a difference in lattice constants between the first crystal plane and the second crystal plane. Therefore, it is preferable that the difference in lattice constants between the first crystal plane and the second crystal plane be within the range of 0.1% to 20%. In the present invention, since the lattice constant of the first crystal plane can be made substantially the same as that of the second epitaxial film, it is easy to achieve a difference in lattice constants 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 the characteristics of the device can also be made better. In addition, 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 made better. The conductive metal is not particularly limited as long as it does not hinder the objective of the present invention, and examples include gold, silver, platinum, palladium, silver-palladium, copper, nickel, or alloys thereof, but in the present invention, it is preferable that it contains platinum. In the present invention, according to the above manufacturing method, preferably 100 nm 2 A defect-free single crystal film can be obtained as an electrode over the above area, more preferably 1000 nm. 2 A defect-free single-crystal film can be easily obtained over the above area. Furthermore, a single-crystal film with a thickness of preferably 100 nm or more can be easily obtained as an electrode.

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

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

[0022] In the present invention, it is preferable to deposit the epitaxial film using oxygen gas after using oxygen atoms in the oxide film, and by depositing the film in this manner, the deposition rate and other properties are improved. Furthermore, by depositing the film in this manner, a laminated structure in which an epitaxial layer is laminated on a crystalline substrate can be easily obtained, wherein between the crystalline substrate and the epitaxial layer, there is an amorphous thin film containing the constituent metal of the epitaxial layer and / or the crystalline substrate and / or an embedded layer embedded in a part of the crystalline substrate in one or more layers and containing the constituent metal. In the present invention, it is preferable that the laminated structure has both the amorphous layer and the embedded layer, as this can further improve the functionality of the epitaxial film. Furthermore, it is preferable that the amorphous layer and the embedded layer each contain the constituent metal of the epitaxial layer, as this improves the crystallinity of the epitaxial film and the like. Furthermore, in the present invention, it is preferable that the constituent metal contains Hf, as this promotes stress relaxation and enables multi-stage stress relaxation. In addition, in the present invention, it is preferable that the thickness of the amorphous thin film be 1 nm to 10 nm, as this can further improve the crystallinity of the epitaxial film, and such an amorphous thin film of 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 shape of the embedded layer has a substantially inverted triangular cross-sectional shape, as this can further improve the functionality of the epitaxial film. These preferred laminated structures can be easily obtained by appropriately adjusting the thickness of the oxide film and the timing of oxygen gas introduction.

[0023] In the lamination process described above, the means for forming the epitaxial film is usually preferred, and the means for forming the film may be any known means. In the present invention, the means for forming the film is preferably vapor deposition or sputtering, and more preferably vapor deposition.

[0024] The crystalline film or laminated structure obtained as described above can be suitably used in electronic devices according to conventional methods. For example, the laminated structure can be used as a piezoelectric element, connected to a power supply or electrical / electronic circuit, mounted on a circuit board, or packaged to constitute various electronic devices. In the present invention, it is preferable that the electronic device is a piezoelectric device, and it 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 them, it can be used in various sensors such as magnetic sensors. It can also be applied to constant voltage driven memory, and for example, by connecting an energy storage element and a rectifier power management circuit, it becomes an energy conversion device (energy harvester) that generates power from an external magnetic field or vibration. The energy conversion device can be incorporated and used in power supply systems and wearable terminals (earphones / hearable devices, smartwatches, smart glasses, smart contact lenses, cochlear implants, cardiac pacemakers, etc.). In the present invention, it is preferable to use the laminated structure in applications such as 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 aforementioned electronic device is suitably used in electronic devices in accordance with conventional methods. Besides the electronic devices described above, the device can be applied to a variety of other electronic devices. More specifically, suitable examples include liquid dispensing heads, liquid dispensing devices, vibration wave motors, optical instruments, vibration devices, imaging devices, piezoelectric acoustic components, and audio playback devices, audio recording devices, mobile phones, and various information terminals.

[0026] Furthermore, the aforementioned electronic devices can also be applied to systems in accordance with conventional laws, and such systems include, for example, sensor systems. [Examples]

[0027] (Example 1) The crystal growth surface of the Si substrate (100) was treated with RIE, and after heating in the presence of oxygen to form a thermal oxide film, a single crystal of crystalline metal oxide was formed on the Si substrate by a vapor deposition method without using oxygen, causing a thermal reaction between the metal of the deposition source and the oxygen in the oxide film on the Si substrate. Then, by flowing oxygen, lowering the temperature, and increasing the pressure, a single crystal film of crystalline metal oxide was deposited by vapor deposition. The conditions for the vapor deposition method during this film deposition 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 a single crystal film of crystalline metal oxide by sputtering. The conditions used for this process are shown below. Equipment: ULVAC QAM-4 sputtering system 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. The conditions used for this process are shown below. Equipment: ULVAC QAM-4 sputtering system Power: 150W (RF) Gas: Ar Pressure: 1.8 Pa Substrate temperature: 600℃ Thickness: 20nm

[0030] Next, on the SRO film, a piezoelectric film of Pb(Zr) 0.52 Ti 0.48 The O3 film (PZT film) was formed by a coating method. The conditions used are as follows.

[0031] Lead acetate was used as the raw material for Pb, zirconyl nitrate was used as the raw material for Zr, and titanium isopropoxide was used as the raw material for Ti. Also, each raw material of Pb, Zr, and Ti was mixed so that the composition ratio became Pb:Zr:Ti = 100 + δ:52:48. The solvent was pure water considering the solubility of the raw materials, and acetic acid was added to control hydrolysis. Furthermore, ethanol (0.5 - 3.0 mol with respect to 1 mol of PZT) in which polyvinylpyrrolidone powder was mixed and dissolved for viscosity adjustment was added and used. Finally, an appropriate amount of 2-n-butoxyethanol was mixed for wettability adjustment during coating, and a sol-gel solution as a raw material solution was prepared.

[0032] Next, the prepared sol-gel solution was dropped onto the substrate and rotated at 2000 rpm for 1 minute, and the sol-gel solution was spin-coated (applied) onto the substrate to form a film containing the precursor. Then, the substrate was placed on a hot plate at a temperature of 150 °C, and further placed on a hot plate at a temperature of 350 °C to evaporate the solvent and dry the film. This process was repeated 5 times to stack 5 layers under the same conditions, and then heat-treated at 650 °C for 3 minutes in an oxygen (O2) atmosphere to oxidize and crystallize the precursor. The above process was repeated 10 times to fabricate a Pb(Zr 0.52 Ti 0.48 )O3 film (PZT film). The total film thickness at this time was 10 μm.

[0033] The obtained laminated structure was a laminated structure containing an epitaxial film with good adhesion and crystallinity. Cross-sectional STEM images of the obtained laminated structure are shown in Figures 5 and 6. From Figure 6, it can be seen that a very high-quality laminated structure was obtained, and in particular, in Figure 5, it can be seen that a regular peak-and-valley structure is provided at the interface between the crystalline metal oxide single crystal film and the conductive film, and that the angles between adjacent vertices and bases of the peak-and-valley structure differ within the range of 30° to 45°. Furthermore, X-ray crystal lattice images of the conductive film are shown in Figures 7 and 8. From Figures 7 and 8, it can be seen that a defect-free large-area conductive film is present, and that it exhibits excellent effects in electrode properties and the piezoelectric properties of the piezoelectric film laminated thereon. Conventionally, piezoelectric films deposited by spin coating have had difficulty exhibiting piezoelectric properties, but in this embodiment, the piezoelectric film (PZT film) deposited by spin coating had good piezoelectric properties. In addition, the crystals of the crystalline substrate, the crystalline metal oxide single crystal film, and the conductive film of the laminated structure were measured using an X-ray diffractometer. Figure 11 shows the XRD measurement results. 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.

[0034] (Example 2) Except for using nitrogen gas instead of oxygen gas, 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. The crystalline substrate of the laminated structure, the single-crystal film of crystalline metal nitride, and the conductive film were then measured using an X-ray diffractometer. Figure 12 shows the XRD measurement results. 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 crystalline substrate. Furthermore, when measured using the four-terminal method, the obtained single-crystal film of crystalline metal nitride had good conductivity.

[0035] Figure 13 shows the deposition apparatus used in Example 1. The deposition apparatus in Figure 13 is equipped with at least a crucible containing metal sources 101a to 101b, grounds 102a to 102h, ICP electrodes 103a to 103b, cut filters 104a to 104b, DC power supplies 105a to 105b, RF power supplies 106a to 106b, lamps 107a to 107b, Ar source 108, reactive gas source 109, power supply 110, substrate holder 111, substrate 112, cut filter 113, ICP ring 114, vacuum chamber 115, and rotating shaft 116. Note that the ICP electrodes 103a to 103b in Figure 13 have a substantially concave or parabolic shape that curves toward the center of the substrate 112.

[0036] As shown in Figure 13, the substrate 112 is secured on the substrate holder 111. Then, the rotating shaft 116 is rotated using the power supply 110 and a rotating mechanism (not shown) to rotate the substrate 112. The substrate 112 is also heated by lamps 107a to 107b, and the inside of the vacuum chamber 115 is evacuated to create a vacuum or reduced pressure using a vacuum pump (not shown). After that, Ar gas is introduced into the vacuum chamber 115 from the Ar source 108, and the surface of the substrate 112 is cleaned by forming argon plasma on the substrate 112 using DC power supplies 105a to 105b, RF power supplies 106a to 106b, ICP electrodes 103a to 103b, cut filters 104a to 104b, and grounds 102a to 102h.

[0037] Ar gas is introduced into the vacuum chamber 115, and a reactive gas is also introduced using the reactive gas source 109. At this time, the lamp heaters, lamps 107a to 107b, are alternately turned on and off, which allows for the formation of a higher quality crystal growth film.

[0038] STEM analysis was performed on the laminated structure obtained in the same manner as in Example 1. The results are shown in Figures 14 to 16. From Figure 14, it can be seen that an embedded layer 1004 is formed between the crystalline substrate 1011 and the epitaxial layer 1001, and further, amorphous layers 1002 and 1003 are formed. From Figure 15, it can be seen that the first amorphous layer 1002 on the crystalline substrate 1011 contains Si from the crystalline substrate and Zr, which is a constituent metal of the epitaxial layer 1001. From Figure 16, it can be seen that the embedded layer 1004 has a roughly inverted triangular cross-sectional shape and is an oxide containing Hf and Si.

[0039] (Examples of application) Examples of applications of the obtained laminated structure will be described in more detail below with reference to the figures, but the present invention is not limited to these examples. In addition, unless otherwise specified, piezoelectric devices and the like can be manufactured from the laminated structure using known means.

[0040] Figure 9 shows an embodiment of an acoustic MEMS transducer constituting a MEMS microphone in which the laminated structure is suitably used in the present invention. The MEMS transducer can constitute an acoustic emission device (for example, a speaker).

[0041] The MEMS microphone configured in the acoustic MEMS transducer shown in Figure 9 is a cantilever-type MEMS microphone and comprises 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, and a gap 9 is provided between the cantilever beams 8A and 8B. The cantilever beams 8A and 8B are formed by a multilayer structure including, for example, multiple piezoelectric layers (PZT films) 26a and 26b, and are arranged alternately 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 crystalline oxide) 23 electrically insulates the cantilever beams 8A and 8B from the crystalline substrate 21. In Figure 9, a neutron-absorbing material (e.g., HfO2 or its mixed crystal) is used in the dielectric layer (single-crystal film of crystalline oxide) 23. Compared to cases where SiO2 or SiN is used, it exhibits superior adhesion to the Si substrate and crystallinity, as well as superior piezoelectric properties and durability.

[0042] Figure 10 shows an example of an application of the laminated structure in the present invention to a fluid discharge device that can be suitably used in printing applications, particularly in the form of an inkjet print head. Specifically, it shows a cross-sectional view of a part of a wafer equipped with a piezoelectric actuator that includes 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 Figure 10 is equipped with a chamber 41 for containing fluid. The chamber 41 is configured to take in fluid from a tank (not shown) via a flow path 40. The wafer in Figure 10 also includes a Si substrate 31, on which a dielectric layer (a single crystal film of crystalline oxide) 33 is provided as a first epitaxial layer, facing the chamber 41. In Figure 10, a neutron-absorbing material (e.g., HfO2 or its mixed crystal) is used in the dielectric layer (single crystal film of crystalline oxide) 23. Compared to cases where SiO2 or SiN is used, it exhibits superior adhesion to the Si substrate and crystallinity, as well as superior piezoelectric properties and durability. The single crystal film 33 of crystalline oxide has a rectangular shape in the top view (not shown), for example, and this shape may be any of the following: a square, a rectangle, a rectangle with rounded corners, a parallelogram, etc.

[0043] A piezoelectric actuator is constructed by sequentially laminating a Pt film 34a, an SRO film 35a, a piezoelectric film (PZT film) 36, an SRO film 35b, and a Pt film 34b on a single-crystal film 33 of a crystalline oxide. The piezoelectric actuator further comprises electrodes 34a and 35a, a piezoelectric film 36, and an insulating film 37 extending over electrodes 34b and 35b. The insulating film 37 contains a dielectric material used for electrical insulation, which may be a known dielectric material, such as an 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 approximately 10 nm and approximately 10 μm. The conductive path 39 is provided on the insulating layer (insulating film) 37 and contacts electrodes 34a and 35a and electrodes 34b and 35b, respectively, allowing selective access during use. The conductive path is composed of any known conductive material, and suitable examples of such conductive materials include aluminum (Al). The passivation layer 42 is provided on the insulating layer 37, electrodes 34b and 35b, and the conductive path 39. The passivation layer 42 is composed of a dielectric material used for passivation of the piezoelectric actuator, and such dielectric material is not particularly limited and may be any known dielectric material. Suitable examples of the dielectric material include SiN or 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. Similarly, the conductive pad 38 is provided along the piezoelectric actuator and is electrically connected to the conductive path 39. The passivation layer 42 functions as a barrier layer to protect the piezoelectric body from humidity and other elements. [Industrial applicability]

[0044] The crystalline film and laminated structure of the present invention are suitably used as electronic devices such as piezoelectric devices, and are suitably used in electronic devices, sensor systems, and the like. [Explanation of Symbols]

[0045] 1. Crystal substrate 2. Oxide film 3. (First) Epitaxial Layer 4. The second epitaxial layer 5. The third epitaxial layer 6. The fourth epitaxial layer 11 Si substrate 13. Single-crystal films of crystalline oxides 14 Conductive film 15 SRO membrane 16 PZT membrane 21. Crystal 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 The ninth epitaxial layer (SRO film) 26a Fourth epitaxial layer (PZT film) 26b Eighth epitaxial layer (PZT film) 28A Cantilever Beam 28B Cantilever Beam 29 gaps 30 cavities 31. Crystal Substrate (Si Substrate) 33. (First) Epitaxial layer (single crystal film of crystalline oxide) 34a Second epitaxial layer (Pt film) 34b The sixth epitaxial layer (Pt film) 35a Third epitaxial layer (SRO film) 35b Fifth epitaxial layer (SRO film) 36. The fourth epitaxial layer (PZT film) 37 Insulating Film 38 conductive pads 39 Conductive Path 40 flow channels 41 Chambers 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 Lamp 108 Ar source 109 Reactive gas sources 110 Power supply 111 PCB holder 112 circuit boards 113 Cut Filter 114 ICP rings 115 Vacuum chamber 116 Rotation axis 1001 Epitaxial layer 1002 The first amorphous layer 1003 Second amorphous layer 1004 Embedding layer 1011 circuit board

Claims

1. Crystal substrate and An epitaxial film stacked on the aforementioned crystal substrate, A second epitaxial film laminated on the aforementioned epitaxial film, It has, The epitaxial film is The first crystal plane is the interface with the second epitaxial film, The second crystal plane opposite to the first crystal plane, It is a single layer crystalline film containing, At the interface between the epitaxial film and the second epitaxial film, the lattice constant of the first crystal plane in the direction along the crystal substrate is the same as the lattice constant of the second epitaxial film in the direction along the crystal substrate. A laminated structure in which the difference between the lattice constant of the first crystal plane in the direction along the crystal substrate and the lattice constant of the second crystal plane in the direction along the crystal substrate is within the range of 0.1% to 20%.

2. The laminated structure according to claim 1, wherein the epitaxial film is formed by incorporating oxygen atoms in an oxide film laminated on the crystal substrate into the epitaxial film.

Images