Method for manufacturing a laminated structure and film forming apparatus

Abstract

To provide a laminate structure including an epitaxial film having good adhesion and crystallinity, an electronic device, an electronic instrument, and a manufacturing method by which these can be obtained in an industrially advantageous manner.SOLUTION: In a method for manufacturing a laminated structure in which an epitaxial layer is laminated on a crystal substrate via at least a compound film, the lamination is performed by a step of providing a compound element supply sacrificial layer containing a compound element on the crystal substrate, and a step of forming the epitaxial layer using the compound element of the compound element supply sacrificial layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laminated structure including an epitaxial film, an electronic device, an electronic apparatus, and methods for manufacturing these.

Background Art

[0002] A thin film made of lead zirconate titanate (Pb(Zr,Ti)O3) (hereinafter also referred to as PZT) having excellent piezoelectricity and ferroelectricity is applied to memory elements such as non-volatile memories (FeRAM) by taking advantage of its ferroelectricity, and to MEMS (Micro Electro Mechanical Systems) technologies such as inkjet heads and acceleration sensors.

[0003] In recent years, on a Si substrate oriented in (100), by forming a Pt film oriented in (200) via a ZrO2 film oriented in (200) or the like, it has been studied to form a piezoelectric film having good piezoelectric characteristics on the Pt film (Patent Document 1). However, the adhesion and crystallinity at the interface are still not satisfactory, and a measure that can improve the adhesion and crystallinity at the interface and further improve the piezoelectric characteristics of the piezoelectric film has been awaited.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a laminated structure including an epitaxial film having good adhesion and crystallinity, an electronic device, an electronic apparatus, and a manufacturing method by which these can be obtained industrially advantageously.

Means for Solving the Problems

[0006] As a result of intensive studies to achieve the above object, the present inventors have found that, in a method for manufacturing a laminate structure in which an epitaxial layer containing a crystalline compound is laminated on a crystal substrate, the lamination is performed by a step of providing a compound element supply sacrificial layer containing a compound element on the crystal substrate, and a step of forming the epitaxial layer using the compound element of the compound element supply sacrificial layer. Thus, a laminate structure including an epitaxial film having excellent adhesion and crystallinity can be easily obtained even with different compositions. The present inventors have found that such a laminate structure and a method for manufacturing the same can solve the above-described conventional problems at once. Further, after obtaining the above findings, the present inventors repeated studies and completed the present invention.

[0007] That is, the present invention relates to the following inventions. [1] A method for manufacturing a laminate structure in which an epitaxial layer containing a crystalline compound is laminated on a crystal substrate, the method including a step of providing a compound element supply sacrificial layer containing an oxygen-containing compound element on the crystal substrate, and a step of forming the epitaxial layer using the compound element of the compound element supply sacrificial layer. [2] The manufacturing method according to [1], wherein after using the compound element, a compound element gas is introduced and the epitaxial layer is formed in the presence of the compound element gas. [3] The manufacturing method according to claim 1 or 2, wherein the lamination is performed by vapor deposition or sputtering. [4] The manufacturing method according to [1] or [2], wherein the lamination is performed by vapor deposition. [5] The manufacturing method according to any one of [1] to [4], wherein the compound element supply sacrificial layer is a compound film provided on the crystal substrate. [6] A laminate structure in which an epitaxial layer is laminated on a crystal substrate, wherein the epitaxial layer is formed by incorporating a compound element in a compound element supply sacrificial layer provided on the crystal substrate. [7] The laminate structure according to [6], wherein the crystal substrate is a crystalline Si substrate. [8] The compound element supply sacrificial layer is the laminated structure according to [6] or [7] above, which includes a compound film. [9] The laminated structure according to [8] above, wherein the film thickness of the compound film exceeds 1 nm and is less than 100 nm.

[10] The epitaxial layer is the laminated structure according to any one of [6] to [9] above, which includes a metal.

[11] The laminated structure according to

[10] above, wherein the metal includes a d-block metal in the periodic table.

[12] The epitaxial layer is the laminated structure according to any one of [6] to [9] above, which includes a metal compound.

[13] The epitaxial layer is the laminated structure according to any one of [6] to [9] above, which includes a dielectric.

[14] Further, on the epitaxial layer, directly or via another layer, a second epitaxial layer having a composition different from that of the epitaxial layer is laminated, which is the laminated structure according to any one of [6] to

[13] above.

[15] The laminated structure according to

[14] above, wherein the epitaxial layer includes a dielectric and the second epitaxial layer includes a single crystal film of a conductive metal.

[16] Further, on the second epitaxial layer, directly or via another layer, a third epitaxial layer having a composition different from that of the epitaxial layer and the second epitaxial layer is laminated, which is the laminated structure according to

[14] or

[15] above.

[17] The laminated structure according to

[16] above, wherein the third epitaxial layer includes a dielectric, a semiconductor, or a conductor.

[18] The laminated structure according to

[16] above, wherein the third epitaxial layer includes a dielectric.

[19] The laminated structure according to

[16] above, wherein the third epitaxial layer includes a piezoelectric body.

[20] A piezoelectric element including a laminated structure, wherein the laminated structure is the laminated structure according to any one of [6] to

[19] above.

[21] A method for manufacturing a piezoelectric element using a laminated structure, wherein the laminated structure is the laminated structure according to any one of [6] to

[19] .

[22] An electronic device including a laminated structure, wherein the laminated structure is the laminated structure according to any one of [1] to

[14] .

[23] The electronic device according to

[22] , which is a piezoelectric device.

[24] A method for manufacturing an electronic device using a laminated structure, wherein the laminated structure is the laminated structure according to any one of [6] to

[19] .

[25] An electronic apparatus including an electronic device, wherein the electronic device is the electronic device according to

[22] or

[23] .

[26] A method for manufacturing an electronic apparatus using a laminated structure or an electronic device, wherein the laminated structure is the laminated structure according to any one of [6] to

[19] , and the electronic device is the electronic device according to

[22] or

[23] .

[27] A system including an electronic apparatus, wherein the electronic apparatus is the electronic apparatus according to

[25] .

[28] A laminated structure in which an epitaxial layer is laminated on a crystal substrate, and an amorphous thin film containing a constituent metal of the epitaxial layer and / or the crystal substrate and / or one or more embedded layers containing the constituent metal are embedded in a part of the crystal substrate between the crystal substrate and the epitaxial layer.

[29] The laminated structure according to

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

[30] The laminated structure according to

[28] above, having, between the crystalline substrate and the epitaxial layer, an amorphous thin film containing a constituent metal of the epitaxial layer and / or the crystalline substrate, and an embedded layer that is embedded in part of the crystalline substrate and contains the constituent metal.

[31] The laminated structure according to any one of

[28] to

[30] above, wherein the constituent metal contains Hf.

[32] The laminated structure according to any one of

[28] to

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

[33] The laminated structure according to

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

[32] above.

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

[28] to

[33] above. An electronic device, electronic apparatus, or system characterized by this.

Advantages of the Invention

[0008] The 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, there is an effect that the laminated structure, the electronic device, and the electronic apparatus can be obtained industrially advantageously.

Brief Description of the Drawings

[0009]

Figure 1

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Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Mode for Carrying Out the Invention

[0010] The manufacturing method of the laminate structure of the present invention is a method for manufacturing a laminate structure in which an epitaxial layer containing a crystalline compound is laminated on a crystal substrate, and includes the steps of providing a compound element supply sacrificial layer containing a compound element on the crystal substrate, and forming the epitaxial layer using the compound element of the compound element supply sacrificial layer. The crystalline compound is not particularly limited and may be a known crystalline compound. In the present invention, it is preferably a metal compound, and the metal of the metal compound may also be a known metal. Examples of the metal include D-block metals in the periodic table. The compound of the metal compound may also be a known compound. Examples of the compound in the crystalline compound include, for example, oxides, nitrides, oxynitrides, sulfides, oxysulfides, borides, oxyborides, carbides, oxycarbides, borocarbides, boron nitrides, borosulfides, carbonitrides, carbosulfides, or borocarbonides. In the present invention, oxides or nitrides are preferable because, for example, they can be made more excellent as a buffer layer for stress relaxation and warp reduction in heteroepitaxial growth, and can also make the electrical characteristics (especially the interface between the conductor layer and the insulating layer) more excellent. Further, 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 compound element supply sacrificial layer is preferably an oxygen supply sacrificial layer, and it is preferable to form the epitaxial layer using the oxygen of the oxygen supply sacrificial layer. By the manufacturing method, a laminate structure including an epitaxial film having good adhesion and crystallinity in which the compound element in the compound element supply sacrificial layer provided on the crystal substrate is incorporated into the epitaxial layer can be easily obtained, and such a laminate structure is also included in the present invention.

[0011] The oxygen supply sacrificial layer may be a sacrificial layer that contains oxygen and in which part or all of the layer disappears or is destroyed when oxygen atoms are incorporated. In the present invention, it is preferable that the oxide film is an oxygen supply sacrificial layer in which oxygen atoms are incorporated during the crystal growth of the epitaxial layer and the oxide film itself disappears. In the present invention, it is also preferable that the oxygen supply sacrificial layer is an oxide film provided on the crystal substrate.

[0012] FIG. 1 shows a preferred example of the laminated structure. In the laminated structure of FIG. 1, 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.

[0013] The laminated structure of the present invention can be easily manufactured, for example, as shown in FIG. 3, by forming an oxide film 2 of the crystal substrate 1 on the crystal substrate 1, and then using the oxygen in the oxide film 2 to form an epitaxial film 3 made of a crystalline oxide on the crystal substrate 1 as shown in FIG. 4. In the present invention, the laminated structure may have the oxide film 2 on the crystal substrate 1, but all of the oxygen in the oxide film 2 may be incorporated during the formation of the epitaxial film 3 and the oxide film 2 may disappear. In this specification, the terms "film" and "layer" may be interchanged with each other depending on the case or situation. Further, as a preferred example of the laminated structure, examples of oxides are given, but the present invention is not limited to these preferred examples, and the present invention can be preferably applied to various compounds such as nitrides. Hereinafter, each will be described more specifically, but the present invention is not limited to these specific examples.

[0014] The above-mentioned crystal substrate (hereinafter also simply referred to as "substrate") is not particularly limited as long as it does not inhibit the object of the present invention, such as the substrate material, and may be a known crystal substrate. It may be an organic compound or an inorganic compound. In the present invention, it is preferable that the crystal 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 a crystal substrate having crystals on part or all of the 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 inhibit the object of the present invention, and the crystal structure and the like are not particularly limited either, but it is preferably a crystal of a cubic system, a tetragonal system, a trigonal system, a hexagonal system, an orthorhombic system or a monoclinic system, and more preferably a crystal oriented in (100) or (200). Further, the crystal substrate may 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 formed between the substrate surface and the crystal growth surface. The shape of the substrate is plate-like and is not particularly limited as long as it serves as a support for the epitaxial film. It may be an insulator substrate or a semiconductor substrate, but in the present invention, it is preferable that the substrate is a Si substrate, more preferably a crystalline Si substrate, and most preferably a crystalline Si substrate oriented in (100). In addition, examples of the substrate material include, for example, in addition to the 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 it may be substantially circular (for example, circular, elliptical, etc.), or polygonal (for example, triangular, square, rectangular, pentagonal, hexagonal, heptagonal, octagonal, nonagonal, etc.), and various shapes can be suitably used. Also, 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.

[0015] In the present invention, it is preferable that the crystal substrate has a flat surface. However, it is also preferable that the crystal substrate has unevenness on a part or all of its surface because it can make the quality of crystal growth of the epitaxial film better. The crystal substrate having such unevenness only needs to have uneven portions formed by concave portions or convex portions on a part or all of its surface. The uneven portions are not particularly limited as long as they are composed of convex portions or concave portions, and may be uneven portions composed of convex portions, uneven portions composed of concave portions, or uneven portions composed of convex portions and concave portions. Further, the uneven portions may be formed from regular convex portions or concave portions, or may be formed from irregular convex portions or concave portions. In the present invention, it is preferable that the uneven portions are formed periodically, and more preferably, they are patterned periodically and regularly. The shape of the uneven portions is not particularly limited, and examples thereof include stripe shape, dot shape, mesh shape, or random shape. In the present invention, dot shape or stripe shape is preferable, and dot shape is more preferable. When the uneven portions are patterned periodically and regularly, the pattern shape of the uneven portions is preferably a polygonal shape such as a triangle, a quadrilateral (e.g., square, rectangle, or trapezoid, etc.), a pentagon, or a hexagon, a circular shape, an elliptical shape, etc. When forming the uneven portions in a dot shape, it is preferable to make the lattice shape of the dots into a lattice shape such as a square lattice, an oblique lattice, a triangular lattice, or a hexagonal lattice, and more preferably, into a triangular lattice shape. The cross-sectional shape of the concave portion or convex portion of the uneven portions is not particularly limited, and examples thereof include U-shaped, inverted U-shaped, wavy, or polygonal shapes such as a triangle, a quadrilateral (e.g., square, rectangle, or trapezoid, etc.), 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.

[0016] The oxide film is not particularly limited as long as it can incorporate oxygen atoms into the epitaxial film as the oxygen supply sacrificial layer, and usually contains an oxidation material. The oxidation material is not particularly limited as long as it does not inhibit the object of the present invention, and may be a known oxidation material. Examples of the oxidation material include oxides of metals or semimetals. In the present invention, it is preferable that the oxide film contains the oxidation material of the crystal substrate, and examples of such an oxide film include a thermal oxide film or a natural oxide film of the crystal substrate. Further, the oxide film may be patterned, for example, patterned in a stripe shape, a dot shape, a mesh shape, or a random shape. Note that the film thickness of the oxide film is not particularly limited, but is preferably more than 1 nm and less than 100 nm.

[0017] The epitaxial layer is not particularly limited as long as it includes an epitaxial film in which oxygen atoms in the oxide film are incorporated. Note that the "epitaxial film in which oxygen atoms in the oxide film are incorporated" means that oxygen atoms in the oxide film are taken away 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 crystallographically by incorporating oxygen atoms in the oxide film. In the present invention, however, it preferably contains a metal or a metal oxide. The metal preferably includes, for example, one or more metals belonging to the d-block of the periodic table. The metal oxide preferably includes, for example, oxides of one or more metals belonging to the d-block of the periodic table. In the present invention, it is preferable that the epitaxial film contains a dielectric. Also, in the present invention, it is preferable that the epitaxial film contains a neutron absorber. The neutron absorber may be a known neutron absorber. In the present invention, by using such a neutron absorber to take in oxygen in the oxide film, the adhesion, crystallinity, and characteristics of the functional film can be made more excellent. As the neutron absorber, for example, hafnium (Hf) etc. can be mentioned as a preferable example. Also, the epitaxial layer may be composed of one or more epitaxial films. 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 composition different from that of the epitaxial film is laminated directly or via another layer on the epitaxial film. By laminating in this way, at the interface between the epitaxial layer and the second epitaxial layer (hereinafter also referred to as the "first epitaxial layer"), the first epitaxial layer can be regularly distorted so as to be substantially the same as the lattice constant of the second epitaxial layer.As the above-described regular transformation modes, for example, a transformation in which the shape is deformed into a valley structure is a preferred example. In the present invention, it is preferable that the angles formed by the adjacent vertices and bottom points of the valley structure are different from each other, and it is more preferable that the angles are each within the range of 30° to 45°. Here, although the epitaxial layer usually has a first crystal plane and a second crystal plane, a lattice constant difference may occur between the first crystal plane and the second crystal plane due to the transformation. Therefore, it is preferable that the lattice constant difference between the first crystal plane and the second crystal plane is within the range of 0.1% to 20%. In the present invention, since the first crystal plane can be substantially the same as the lattice constant of the second epitaxial film, it is easily possible to make the lattice constant difference between the first epitaxial layer and the second epitaxial layer within the range of 0.1% to 20%.

[0018] Further, 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 the adhesion and crystallinity at the interface be further improved, but also, for example, the characteristics of the element can be made more excellent. Further, according to the present invention, when the second epitaxial layer is made of a single crystal film of a conductive metal, a defect-free film with a large area can be easily obtained, and not only the function as an electrode but also the characteristics of an element or the like can be made more excellent. The conductive metal is not particularly limited as long as it does not inhibit the object of the present invention. For example, gold, silver, platinum, palladium, silver palladium, copper, nickel, or an alloy thereof can be mentioned. In the present invention, it is preferable to contain platinum. In the present invention, according to the above-described manufacturing method, preferably, a defect-free single crystal film can be obtained as an electrode in an area of 100 nm 2 or more, and more preferably, a defect-free single crystal film can be easily obtained in an area of 1000 nm 2 or more. Also, a single crystal film with a thickness of preferably 100 nm or more can be easily obtained as an electrode.

[0019] In the present invention, further, on the second epitaxial film, directly or via another layer, a third epitaxial film and / or a fourth epitaxial film having a composition different from that of the epitaxial film and the second epitaxial film are preferably laminated. FIG. 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. The laminated structure of FIG. 2 has a first epitaxial layer 3 laminated on a crystal substrate 1 using an oxide film, and further, 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. Note that 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. Also, 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 film thickness of each of the epitaxial films is not particularly limited, but is preferably 10 nm to 1000 μm, and more preferably 10 nm to 100 μm.

[0020] In the method for manufacturing a laminated structure in which an epitaxial layer is laminated on a crystal substrate via at least an oxide film, the above lamination can be easily obtained by forming an epitaxial film using oxygen atoms in the oxide film at 350°C to 700°C. When it is in the range of 350°C to 700°C, it is possible to easily incorporate oxygen atoms in the oxide film into the epitaxial film and cause crystal growth.

[0021] In the present invention, it is preferable that after using oxygen atoms in the oxide film for the above-mentioned lamination, an epitaxial film is formed using oxygen gas. By forming the film in this way, the film formation rate and the like become more excellent. Further, by forming the film in this way, a laminated structure in which an epitaxial layer is laminated on a crystal substrate, and an amorphous thin film containing the constituent metal of the epitaxial layer and / or the crystal substrate and / or one or more parts of the crystal substrate are embedded between the crystal substrate and the epitaxial layer, and a laminated structure having an embedded layer containing the constituent metal can be easily obtained. In the present invention, it is preferable that the laminated structure has both the amorphous layer and the embedded layer because the functionality of the epitaxial film and the like can be further improved. Further, it is preferable that the amorphous layer and the embedded layer each contain the constituent metal of the epitaxial layer because the crystallinity of the epitaxial film and the like becomes more excellent. Further, in the present invention, it is preferable that the constituent metal contains Hf because it promotes stress relaxation and the like, and further enables stress relaxation and the like in multiple stages. Further, in the present invention, it is preferable that the film thickness of the amorphous thin film is 1 nm to 10 nm because the crystallinity of the epitaxial film and the like can be further improved. Such an amorphous thin film with a preferable film thickness can be easily obtained by the preferable manufacturing method of the present invention. Further, in the present invention, it is preferable that the shape of the embedded layer has a substantially inverted triangular cross-sectional shape because the functionality of the epitaxial film can be further improved. These preferable laminated structures can be easily obtained by appropriately adjusting the film thickness of the oxide film, the timing of introducing the oxygen gas, and the like.

[0022] As the lamination means used in the above lamination, usually, the film formation means of the epitaxial film is preferably used, and the film formation means may be a known film formation means. In the present invention, it is preferable that the film formation means is evaporation or sputtering, and more preferably evaporation.

[0023] The laminated structure obtained as described above is suitably used for electronic devices according to a conventional method. For example, the laminated structure can be used as a piezoelectric element and connected to a power source or an electric / electronic circuit, and mounted or packaged on a circuit board 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, for example, as a piezoelectric device in electronic devices such as an inkjet printer head, a micro actuator, a gyroscope, and a motion sensor. Further, for example, by connecting and packaging an amplifier and a rectifier circuit, it can be used for various sensors such as a magnetic sensor. It can also be applied to a memory driven by a constant voltage. For example, by connecting a power storage element and a rectifying 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 is incorporated and used in a power supply system or a wearable terminal (such as an earphone / hearable device, a smart watch, smart glasses (eyeglasses), a smart contact lens, an artificial inner ear, a cardiac pacemaker, etc.). In the present invention, it is preferable to use the laminated structure for, for example, smart glasses, an AR headset, a MEMS mirror for a LiDAR system, a piezoelectric MEMS ultrasonic transducer (PMUT) for advanced medical use, a piezo head for an industrial and commercial 3D printer, etc.

[0024] The electronic device is suitably used for electronic equipment according to a conventional method. As the electronic equipment, in addition to the above-described electronic equipment, it can be applied to various electronic equipment. More specifically, for example, a liquid ejection head, a liquid ejection device, a vibration wave motor, an optical device, a vibration device, an imaging device, a piezoelectric acoustic component, and an audio reproduction device having the piezoelectric acoustic component, an audio recording device, a mobile phone, various information terminals, etc. are preferable examples.

[0025] Further, the electronic equipment is also applied to a system according to a conventional method, and examples of such a system include a sensor system, etc.

Example

[0026] (Example 1) The crystal growth surface side of the Si substrate (100) was processed by RIE, heated in the presence of oxygen to form a thermal oxide film, and then, without using oxygen, the metal of the evaporation source and the oxygen in the oxide film on the Si substrate were thermally reacted by an evaporation method to form a single crystal of a crystalline metal oxide on the Si substrate. Subsequently, oxygen was flowed, the temperature was lowered, and the pressure was increased to form a single crystal film of a crystalline metal oxide by an evaporation method. The conditions of each evaporation method at the time of this film formation were as follows. Evaporation source: Hf, Zr Voltage: 3.5 - 4.75 V Pressure: 3×10 -2 ~6×10 -2 Pa Substrate temperature: 450 - 700 °C

[0027] Next, a metal film of platinum (Pt) was formed as a conductive film on the single crystal film of the crystalline metal oxide by a sputtering method. The conditions at this time are shown below. Apparatus: Sputtering apparatus QAM - 4 manufactured by ULVAC Pressure: 1.20×10 -1 Pa Target: Pt Power: 100 W (DC) Thickness: 100 nm Substrate temperature: 450 - 600 °C

[0028] Next, a SRO (strontium ruthenate) film was formed on the conductive film by a sputtering method. The conditions at this time are shown below. Apparatus: Sputtering apparatus QAM - 4 manufactured by ULVAC Power: 150 W (RF) Gas: Ar Pressure: 1.8 Pa Substrate temperature: 600 °C Thickness: 20 nm

[0029] Next, a Pb(Zr 0.52 Ti 0.48 )O3 film (PZT film) was formed as a piezoelectric film by a coating method. The conditions at this time are shown below.

[0030] 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 as to have a composition ratio of 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 to 3.0 mol per 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.

[0031] 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.

[0032] The obtained laminated structure was a laminated structure including an epitaxial film having good adhesion and crystallinity. Further, the cross-sectional STEM images of the obtained laminated structure are shown in FIGS. 5 and 6. It can be seen from FIG. 6 that a very high-quality laminated structure was obtained. In particular, in FIG. 5, a regular valley structure is provided at the interface between the single crystal film of the crystalline metal oxide and the conductive film, and it can be seen that the angles formed by the adjacent vertices and bottom points of the valley structure are different within the range of 30° to 45°. Further, the X-ray crystal lattice images of the conductive film are shown in FIGS. 7 and 8. It can be seen from FIGS. 7 and 8 that a defect-free large-area conductive film is obtained, and it can be seen that it exhibits excellent effects in the electrode characteristics and the piezoelectric characteristics of the piezoelectric film laminated thereon. Conventionally, it has been difficult for a piezoelectric film formed by spin coating to exhibit piezoelectric characteristics, but the piezoelectric film (PZT film) formed by spin coating in this example had good piezoelectric characteristics. Further, the crystal substrates, the single crystal films of the crystalline metal oxides, and the conductive films of the laminated structure were measured using an X-ray diffractometer for each crystal. FIG. 11 shows the XPS measurement results. As is clear from FIG. 11, a (Hf, Zr)O2 film and a Pt single crystal film having good crystallinity were formed on the Si crystal substrate.

[0033] (Example 2) A metal film of platinum (Pt) was formed as a conductive film on the single crystal film of the crystalline metal nitride in the same manner as in Example 1, except that nitrogen gas was used instead of oxygen gas. Then, the crystal substrates, the single crystal films of the crystalline metal nitrides, and the conductive films of the laminated structure were measured using an X-ray diffractometer for each. FIG. 12 shows the XPS measurement results. As is clear from FIG. 12, a (Hf, Zr)N film and a Pt single crystal film having good crystallinity were formed on the Si crystal substrate. Incidentally, when measured by the four-terminal method, the obtained single crystal film of the crystalline metal nitride had good conductivity.

[0034] The vapor deposition film forming apparatus used in Example 1 is shown in FIG. 13. The film forming apparatus of FIG. 13 includes at least a crucible with metal sources 101a - 101b, grounds 102a - 102h, ICP electrodes 103a - 103b, cut filters 104a - 104b, DC power supplies 105a - 105b, RF power supplies 106a - 106b, lamps 107a - 107b, an Ar source 108, a reactive gas source 109, a power supply 110, a substrate holder 111, a substrate 112, a cut filter 113, an ICP ring 114, a vacuum chamber 115, and a rotating shaft 116. Note that the ICP electrodes 103a - 103b in FIG. 13 have a substantially concave curved surface shape or a parabolic shape curved toward the center of the substrate 112.

[0035] As shown in FIG. 13, the substrate 112 is locked onto the substrate holder 111. Then, the rotating shaft 116 is rotated using the power supply 110 and a rotation mechanism (not shown) to rotate the substrate 112. Also, the substrate 112 is heated by the lamps 107a - 107b, and the inside of the vacuum chamber 115 is evacuated by a vacuum pump (not shown) to be under vacuum or reduced pressure. Thereafter, Ar gas is introduced from the Ar source 108 into the vacuum chamber 115, and argon plasma is formed on the substrate 112 using the DC power supplies 105a - 105b, RF power supplies 106a - 106b, ICP electrodes 103a - 103b, cut filters 104a - 104b, and grounds 102a - 102h, thereby cleaning the surface of the substrate 112.

[0036] Ar gas is introduced into the vacuum chamber 115 and a reactive gas is introduced using the reactive gas source 109. At this time, it is configured such that a higher quality crystal growth film can be formed by alternately repeating turning on and off the lamps 107a - 107b which are lamp heaters.

[0037] The STEM analysis was performed on the laminated structure 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 the buried layer 1004 is formed between the crystal substrate 1011 and the epitaxial layer 1001, and further, the amorphous layers 1002 and 1003 are formed. Also, 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 which is a constituent metal of the epitaxial layer 1001. Also, it can be seen that the second amorphous layer contains Si of the crystal substrate and Hf and Zr which are constituent metals of the epitaxial layer 1001. Further, from FIG. 16, it can be seen that the buried layer 1004 has a substantially inverted triangular cross-sectional shape and is an oxide containing Hf and Si.

[0038] (Application Example) Application examples of the obtained laminated structure will be described more specifically below with reference to the drawings, but the present invention is not limited to these application examples. In the present invention, unless otherwise specified, a piezoelectric device or the like can be manufactured from the laminated structure using known means.

[0039] FIG. 9 shows an embodiment of an acoustic MEMS transducer that constitutes a MEMS microphone in which the laminated structure is preferably used in the present invention. Note that the MEMS transducer can constitute an acoustic emission device (for example, a speaker or the like).

[0040] The MEMS microphone composed of the acoustic MEMS transducer of FIG. 9 shows a cantilever type MEMS microphone, and includes a Si substrate 21 having two cantilever beams 28A and 28B and a cavity 30. Each of the cantilever beams 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. Note that the cantilever beams 8A and 8B are formed by a laminated structure including, for example, a plurality of piezoelectric layers (PZT films) 26a and 26b, and are alternately arranged with a plurality of electrode layers, namely Pt films 24a, 24b, 24c and SRO films 25a, 25b, 25c, 25d. The dielectric layer (single crystal film of crystalline oxide) 23 electrically insulates the cantilever beams 8A and 8B from the crystal substrate 21. In FIG. 9, a neutron absorber (for example, HfO2 or its mixed crystal) is used for the dielectric layer (single crystal film of crystalline oxide) 23, and it is excellent in adhesion and crystallinity to the Si substrate compared with the case where SiO2, SiN, etc. are used, and furthermore, it is also excellent in piezoelectric characteristics and durability.

[0041] FIG. 10 shows an application example to a fluid discharge device that can be preferably used for a printing application, particularly in the form of an inkjet print head, in which the laminated structure of the present invention is used. Specifically, as an electrode layer, it includes Pt films 34a and 34b and SRO films 35a and 35b, and shows a partial cross-sectional view of a wafer provided with a piezoelectric actuator including a PZT film 36 as a piezoelectric film. The wafer of FIG. 10 includes, in addition to the piezoelectric actuator, a chamber 41 for accommodating a fluid. The chamber 41 is configured to take in a fluid from a tank (not shown) through a flow path 40. Further, the wafer of FIG. 10 includes a Si substrate 31, and on it, as a first epitaxial layer, a dielectric layer (single crystal film of crystalline oxide) 33 is provided and faces the chamber 41. In FIG. 10, a neutron absorber (for example, HfO2 or its mixed crystal) is used for the dielectric layer (single crystal film of crystalline oxide) 23, and it is excellent in adhesion and crystallinity to the Si substrate compared to the case where SiO2, SiN, etc. are used. Furthermore, it is also excellent in piezoelectric characteristics and durability. Note that the single crystal film 33 of the crystalline oxide has, for example, a rectangular shape in a top view (not shown), and such a shape may be any of, for example, a square, a rectangle, a rectangle with rounded corners, a parallelogram, etc.

[0042] On the single crystal film 33 of the crystalline oxide, 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 to form a piezoelectric actuator. Further, the piezoelectric actuator further includes electrodes 34a and 35a, a piezoelectric film 36, and an insulating film 37 extending on the electrodes 34b and 35b. The insulating film 37 contains a dielectric material used for electrical insulation, and such a dielectric material may be a known dielectric material, for example, a SiO2 layer, a SiN layer, or an Al2O3 layer. Note that the thickness of the insulating layer including the insulating film as a constituent material is not particularly limited, but is preferably in the range of about 10 nm to about 10 μm. Further, the conductive path 39 is provided on the insulating layer (insulating film) 37 and contacts the electrodes 34a and 35a and the electrodes 34b and 35b, respectively, enabling selective access during use. Note that the constituent material of the conductive path may be a known conductive material, and examples of such a conductive material include aluminum (Al) and the like as suitable examples. Further, the passivation layer 42 is provided on the insulating layer 37, the electrodes 34b and 35b, and the conductive path 39. The passivation layer 42 only needs to be composed of a dielectric material used for passivation of the piezoelectric actuator, and such a dielectric material is not particularly limited and may be a known dielectric material. Examples of the dielectric material include SiN or SiON (silicon oxynitrate) and the like as suitable examples. The thickness of the passivation layer is not particularly limited, but is preferably in the range of about 0.1 μm to about 3 μm. Further, the conductive pad 38 is similarly provided along the piezoelectric actuator and is electrically connected to the conductive path 39. Note that the passivation layer 42 functions as a barrier layer that protects the piezoelectric body from humidity and the like.

Industrial Applicability

[0043] The laminated structure of the present invention is suitably used as an electronic device such as a piezoelectric device, for example, and is suitably used in electronic devices, sensor systems, and the like.

Explanation of Signs

[0044] 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 film of crystalline oxide 14 Conductive film 15 SRO film 16 PZT film 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 Tenth epitaxial layer (Pt film) 25a Third epitaxial layer (SRO film) 25b Fifth epitaxial layer (SRO film) 25c Seventh epitaxial layer (SRO film) 25d Ninth 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 Cavity 31 Crystal substrate (Si substrate) 33 (First) epitaxial layer (single crystal film of crystalline oxide) 34a Second epitaxial layer (Pt film) 34b Sixth epitaxial layer (Pt film) 35a Third epitaxial layer (SRO film) 35b Fifth epitaxial layer (SRO film) 36 Fourth epitaxial layer (PZT film) 37 Insulating film 38 Conductive pad 39 Conductive path 40 Flow path 41 Chamber 42 Passivation layer 101a~101b Metal source 102a~102j Ground 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 source 110 Power supply 111 Substrate holder 112 Substrate 113 Cut filter 114 ICP ring 115 Vacuum chamber 116 Rotation axis 1001 Epitaxial layer 1002 First amorphous layer 1003 Second amorphous layer 1004 Embedded layer 1011 Substrate

Claims

1. A method for manufacturing a laminated structure in which an epitaxial layer containing an oxide containing Hf and Zr is laminated on a crystal substrate that is a Si substrate, comprising: (a) forming an oxygen supply sacrificial layer containing oxygen on the crystal substrate; (b) forming the epitaxial layer using the oxygen of the oxygen supply sacrificial layer; (c) after step (b), introducing oxygen gas and forming the epitaxial layer in the presence of the oxygen gas. The laminated structure formed with the epitaxial layer in steps (b) and (c) has: a first amorphous layer containing Zr and Si, formed between the crystal substrate and the epitaxial layer; a second amorphous layer containing Hf, Zr and Si, formed between the first amorphous layer and the epitaxial layer; an embedded layer embedded in part of the crystal substrate and containing Hf and Si. A method for manufacturing a laminated structure, wherein the shape of the embedded layer has a substantially inverted triangular cross-sectional shape.

2. A film forming apparatus for laminating an epitaxial layer containing an oxide containing Hf and Zr on a crystal substrate that is a Si substrate, comprising: a first forming unit for forming an oxygen supply sacrificial layer containing oxygen on the crystal substrate; a second forming unit for forming the epitaxial layer using the oxygen of the oxygen supply sacrificial layer; a third forming unit for introducing oxygen gas after using the oxygen of the oxygen supply sacrificial layer and forming the epitaxial layer in the presence of the oxygen gas; a control unit for controlling the operations of the first forming unit, the second forming unit and the third forming unit. The control unit is configured such that: the laminated structure formed with the epitaxial layer by the second forming unit and the third forming unit has: a first amorphous layer containing Zr and Si, formed between the crystal substrate and the epitaxial layer; a second amorphous layer containing Hf, Zr and Si, formed between the first amorphous layer and the epitaxial layer; an embedded layer embedded in part of the crystal substrate and containing Hf and Si. A film forming apparatus that controls the operations of the second forming unit and the third forming unit such that the shape of the embedded layer has a substantially inverted triangular cross-sectional shape. ​ ​ ​ ​ ​

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