Stacked structures and semiconductor devices

Abstract

To provide a laminated structure that includes a crystalline oxide film having a corundum structure with a smooth surface and has an excellent semiconductor property when being applied to a semiconductor device.SOLUTION: A laminated structure includes: a base substrate; and a crystalline oxide film having a corundum structure. The crystalline oxide film includes at least carbon (C) as an impurity and has root mean square roughness (RMS) of 0.1 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminated structure, a semiconductor device, and a method for manufacturing a laminated structure. [Background technology]

[0002] As a method for forming highly crystalline gallium oxide-based thin films on a sample to be coated, a film deposition method using water microparticles, such as the mist CVD method, is known (Patent Document 1). In this method, a gallium compound such as gallium acetylacetonate is dissolved in an acid such as hydrochloric acid to create a raw material solution, and raw material microparticles are generated by atomizing this raw material solution. These raw material microparticles are then supplied to the film deposition surface of the sample to be coated using a carrier gas, and the raw material mist reacts to form a thin film on the film deposition surface, thereby forming a highly crystalline gallium oxide-based thin film on the sample to be coated.

[0003] To form semiconductor devices using gallium oxide-based thin films, it is essential to control the conductivity of the gallium oxide-based thin film. Patent Document 1 and Non-Patent Document 1 disclose a technique for doping α-gallium oxide thin films with impurities. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2013-28480 [Patent Document 2] Japanese Patent Publication No. 2015-199649 [Non-Patent Document 1] Electrical Conductive Corundum-Structured α-Ga2O3 Thin Films on Sapphire with Tin-Doping Grown by Spray-Assisted Mist Chemical Vapor Deposition(Japanese Journal of Applied Physics 51 (2012) 070203) [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] According to the methods described in Patent Document 1 and Non-Patent Document 1, it is possible to form a thin film of α-gallium oxide (hereinafter sometimes referred to as "α-Ga2O3") with excellent conductivity. However, there are specific problems such as the film surface not being smooth, and it is still not satisfactory for use in semiconductor devices. Furthermore, surface treatment such as etching can be considered in order to smooth the film surface, but in this case, problems such as the thin film being removed or the semiconductor properties being impaired arise.

[0006] To address this problem, Patent Document 2 discloses a method for reducing average roughness (Ra). However, even using this method, the surface flatness was not sufficient, and the semiconductor device characteristics using the resulting film were not satisfactory.

[0007] The present invention has been made to solve the above problems and aims to provide a laminated structure that includes a crystalline oxide film having a smooth corundum structure on its surface and exhibits excellent semiconductor properties when applied to a semiconductor device, further providing a laminated structure having a crystalline oxide film with reduced crystal defects, and providing a method for manufacturing the laminated structure. [Means for solving the problem]

[0008] The present invention has been made to achieve the above objective, and provides a laminated structure having a base substrate and a crystalline oxide film having a corundum structure, wherein the crystalline oxide film contains at least carbon (C) as an impurity, and the root mean square roughness (RMS) of the crystalline oxide film is 0.1 μm or less.

[0009] Such a layered structure has a smooth crystalline oxide film on its surface, and when applied to a semiconductor device, it exhibits excellent semiconductor properties.

[0010] At this time, the C concentration in the crystalline oxide film is 2×10 17 ~2×10 20 / cm 3 and a laminated structure can be obtained.

[0011] As a result, the surface becomes smoother, and when applied to a semiconductor device, the semiconductor characteristics become more excellent.

[0012] At this time, a laminated structure can be obtained in which the film thickness of the crystalline oxide film is 1 μm or more.

[0013] As a result, it has a smooth surface and becomes a thick-film laminated structure.

[0014] At this time, a laminated structure can be obtained in which the underlying substrate is a c-plane sapphire substrate.

[0015] As a result, a laminated structure having a crystalline oxide film with a better-quality cordierite structure is obtained.

[0016] At this time, a laminated structure can be obtained in which the area of the crystalline oxide film is 100 mm 2 or more.

[0017] As a result, it becomes a large-area structure that is more useful for semiconductor devices.

[0018] Also, a method for manufacturing a laminated structure in which raw material fine particles generated by atomizing a raw material solution are transported to a substrate by a carrier gas, and the raw material fine particles are thermally reacted on the substrate to form a crystalline oxide film having a cordierite structure. By mixing a surface smoothing agent containing at least carbon (C) into the raw material solution, doping treatment of C into the crystalline oxide film is performed, and a method for manufacturing a laminated structure in which the root mean square roughness (RMS) of the surface of the crystalline oxide film is 0.1 μm or less can be provided.

[0019] According to this method for manufacturing a laminated structure, a laminated structure can be manufactured that includes a crystalline oxide film having a corundum structure with a smooth surface, and which exhibits excellent semiconductor properties when applied to a semiconductor device.

[0020] In this case, the method for manufacturing the laminated structure can be one or more alcohols or diketones as the surface smoothing agent.

[0021] This makes it possible to manufacture laminated structures with smoother surfaces more effectively and stably.

[0022] Furthermore, the present invention provides a laminated structure comprising a first crystalline oxide film having a corundum structure and a second crystalline oxide film having a corundum structure, wherein the first crystalline oxide film is located on the second crystalline oxide film, and the second crystalline oxide film contains at least carbon (C) as an impurity.

[0023] In such a multilayer structure, the surface of the second crystalline oxide film having a corundum structure becomes smooth, thus reducing the crystal defects in the first crystalline oxide film having a corundum structure. Such a multilayer structure exhibits excellent semiconductor properties.

[0024] At this time, the C concentration in the second crystalline oxide film is 2 × 10 17 ~2×10 20 / cm 3 It can be a laminated structure.

[0025] This results in a smoother surface, leading to improved semiconductor properties when applied to semiconductor devices.

[0026] In this case, the laminated structure can be made in which the thickness of the first crystalline oxide film is 1 μm or more. Furthermore, the area of ​​the first crystalline oxide film is 100 mm². 2 The above can be used to construct a laminated structure.

[0027] This will make semiconductor devices more useful.

[0028] In this case, the semiconductor device can include the above-described laminated structure.

[0029] This results in a semiconductor device with superior properties. [Effects of the Invention]

[0030] As described above, the laminated structure of the present invention has a crystalline oxide film having a smooth surface corundum structure, and when applied to a semiconductor device, it becomes a laminated structure with excellent semiconductor properties. Furthermore, the method for manufacturing the laminated structure of the present invention makes it possible to manufacture a laminated structure having a crystalline oxide film having a smooth surface corundum structure, and when applied to a semiconductor device, it becomes a laminated structure with excellent semiconductor properties. Moreover, the laminated structure of the present invention includes a crystalline oxide film having a corundum structure with reduced crystal defects in the film, and when applied to a semiconductor device, it becomes a laminated structure with excellent semiconductor properties. [Brief explanation of the drawing]

[0031] [Figure 1] This is a schematic diagram showing an example of a film deposition apparatus used in the film deposition method according to the present invention. [Figure 2] This is a schematic diagram showing an example of a laminated structure according to the present invention. [Modes for carrying out the invention]

[0032] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0033] As described above, there was a need to provide a laminated structure that includes a crystalline oxide film having a corundum structure with a smooth surface and exhibits excellent semiconductor properties when applied to a semiconductor device, a method for manufacturing the laminated structure, and a laminated structure that includes a crystalline oxide film having a corundum structure with reduced crystal defects in the film and exhibits excellent semiconductor properties when applied to a semiconductor device.

[0034] As a result of diligent research into the above-mentioned problems, the present inventors have found that a laminated structure having a substrate and a crystalline oxide film having a corundum structure, wherein the crystalline oxide film contains at least carbon (C) as an impurity, and the root mean square roughness (RMS) of the crystalline oxide film is 0.1 μm or less, results in a crystalline oxide film with a smooth surface, and when applied to a semiconductor device, it becomes a laminated structure with excellent semiconductor properties, thus completing the present invention.

[0035] Furthermore, the present inventors have discovered that a method for manufacturing a laminated structure, comprising atomizing a raw material solution to produce raw material fine particles, transporting these fine particles to a substrate using a carrier gas, and thermally reacting the raw material fine particles on the substrate to form a crystalline oxide film having a corundum structure, wherein the method involves mixing a surface smoothing agent containing at least carbon (C) into the raw material solution to perform a C doping treatment on the crystalline oxide film, thereby reducing the root mean square roughness (RMS) of the surface of the crystalline oxide film to 0.1 μm or less, and thereby producing a laminated structure having a crystalline oxide film with a smooth surface and excellent semiconductor properties when applied to a semiconductor device, can be manufactured, thus completing the present invention.

[0036] Furthermore, the present inventors have found that a laminated structure comprising a first crystalline oxide film having a corundum structure and a second crystalline oxide film having a corundum structure, wherein the first crystalline oxide film is placed on the second crystalline oxide film, and the second crystalline oxide film contains at least carbon (C) as an impurity, results in a crystalline oxide film with reduced crystal defects in the film, and when applied to a semiconductor device, it becomes a laminated structure with excellent semiconductor properties, thus completing the present invention.

[0037] The following explanation will be given with reference to the drawings.

[0038] As a result of diligent research to achieve the above objective, the inventors of the present invention discovered that a crystalline laminated structure with a smooth surface can be obtained by doping treatment using a surface smoothing agent, and after further research, completed the present invention.

[0039] According to a first embodiment of the present invention, a crystalline laminated structure is provided comprising a substrate and a crystalline oxide film having a corundum structure, either directly thereon or via another layer, wherein the root mean square roughness (RMS) of the crystalline oxide film is 0.1 μm or less.

[0040] Furthermore, according to a second embodiment of the present invention, a crystalline laminated structure is provided comprising at least a first crystalline oxide film having a corundum structure and a second crystalline oxide film having a corundum structure, wherein the first crystalline oxide film is provided on the second crystalline oxide film, and the second crystalline oxide film contains at least carbon (C) as an impurity.

[0041] The root mean square roughness (RMS) is not particularly limited as long as it is 0.1 μm or less, but is preferably 30 nm or less, and more preferably 10 nm or less. The root mean square roughness (RMS) refers to the value obtained by using the surface shape measurement results of a 10 μm square area by atomic force microscopy (AFM) and calculating it in accordance with JIS B0601 (corresponding to Rq in the same standard).

[0042] The laminated structure according to the present invention is a structure comprising one or more crystalline oxide films. For example, it may be a laminate of one or more crystalline oxide films and a substrate or thin film. It may also contain films (layers) other than crystalline oxide films (e.g., amorphous layers). It may also be a laminate consisting of multiple films (layers) from which the substrate has been removed.

[0043] The crystalline oxide film may be annealed, which may result in the formation of a metal oxide film between the crystalline oxide film and the ohmic electrode, where the ohmic electrode has been oxidized. Examples of ohmic electrodes include indium and titanium.

[0044] The lower substrate is not particularly limited as long as it can serve as a support for the above-mentioned crystalline oxide film. The material is not particularly limited, and known substrates can be used, which may be organic compounds or inorganic compounds. For example, polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyimide, polyether imide, fluororesin, metals such as iron, aluminum, stainless steel, gold, silicon, sapphire, quartz, glass, calcium carbonate, gallium oxide, SiC, ZnO, GaN, etc. can be mentioned, but it is not limited thereto. In the laminate according to the present invention, a substrate having a corundum structure is preferable. Examples of the substrate having a corundum structure include a sapphire substrate (e.g., c-plane sapphire substrate) and an α-type gallium oxide substrate. In particular, it is preferable to use a c-plane sapphire substrate. This is because a crystalline oxide film having a better quality corundum structure can be obtained. The thickness of the lower substrate is not particularly limited, but preferably 10 to 2000 μm, more preferably 50 to 800 μm. Its area is preferably 100 mm 2 or more, and more preferably the diameter is 2 inches (50 mm) or more.

[0045] The crystalline oxide film is not particularly limited as long as it is a thin film having a corundum structure and containing an oxide semiconductor as a main component. Further, the crystalline oxide film is preferably a single crystal, but may be a polycrystal. Regarding the composition of the crystalline oxide film, it is preferable that the total atomic ratio of gallium, indium, aluminum, and iron among the metal elements in the film is 0.5 or more, and it is more preferable that the atomic ratio of gallium among the metal elements is 0.5 or more. Specifically, this preferable atomic ratio is, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1, and it may be within the range between any two of the values exemplified herein. In the present invention, it is more preferable that the atomic ratio of gallium among the metal elements is 0.5 or more, because the function of the surface smoothing agent in the raw material solution can be more suitably exhibited, and the surface roughness of the crystalline oxide film can be further reduced.

[0046] Furthermore, the composition of the crystalline oxide film is, for example, the general formula: In X Al Y Ga Z Fe V It is preferable that O3(0≦X≦2.5, 0≦Y≦2.5, 0≦Z≦2.5, 0≦V≦2.5, X+Y+Z+V=1.5~2.5), and more preferably that 1≦Z. In this general formula, preferred X, Y, Z, and V are specifically, for example, 0, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, and 2.5. Furthermore, preferred X+Y+Z+V values ​​are, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, and 2.5. Note that X, Y, Z, and V, as well as X+Y+Z+V, may each be within the range of any two of the values ​​exemplified here. It should also be noted that the above general formula represents the composition of atoms on the lattice points forming the corundum structure, and as is clear from the fact that it is not written as "X+Y+Z+V=2", it may also include non-stoichiometric oxides, which may include metal-deficient oxides and oxygen-deficient oxides.

[0047] The crystalline oxide film may be formed directly on the substrate or via another layer. Examples of the other layer include a crystalline film having a corundum structure of a different composition, a crystalline film other than a corundum structure, or an amorphous film. For example, a laminated structure can be formed in which an undoped crystalline oxide film is interposed between a carbon-doped, surface-smoothed crystalline oxide film and the substrate.

[0048] The crystalline oxide film is preferably doped with impurities in at least a portion of its structure (more specifically, a portion in the thickness direction), but its structure may be a single layer or a multi-layer structure. In the case of a multi-layer structure, the crystalline oxide film is composed of, for example, an insulating thin film and a conductive thin film laminated together, but the present invention is not limited to this. When an insulating thin film and a conductive thin film are laminated together to form a multi-layer structure, the compositions of the insulating thin film and the conductive thin film may be the same or different from each other. The ratio of the thickness of the insulating thin film to the thickness of the conductive thin film is not particularly limited, but for example, the ratio of (thickness of the conductive thin film) / (thickness of the insulating thin film) is preferably 0.001 to 100, and more preferably 0.1 to 5. These even more preferred ratios are, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, and 5, and may be within the range of any two of the numbers exemplified here.

[0049] The conductive thin film may be doped with impurities to impart conductivity. By adjusting the conductivity as appropriate, a crystalline oxide semiconductor film can be obtained. The doping concentration of the impurities to impart conductivity is appropriately determined according to the properties required for the conductive thin film, but preferably 1 × 10⁻⁶. 15 / cm 3 From 1 x 10 22 / cm 3 Furthermore, the type of impurities used for doping is not particularly limited, but examples include dopants consisting of at least one selected from Ge, Sn, Si, Ti, Zr, Hf, V, Nb, Rh, Ag, and Cu. Insulating thin films usually do not require impurity doping, but they may be doped to an extent that conductivity does not appear.

[0050] The thickness of the crystalline oxide film is not particularly limited and may be 1 μm or less, or 1 μm or more. However, in the present invention, the thickness of the crystalline oxide film is preferably 1 μm or more, and more preferably 1 to 50 μm. By using such a preferred film thickness, not only is the surface smoothness improved without impairing semiconductor properties, but electrical resistance can also be reduced during annealing, resulting in even better semiconductor properties.

[0051] The laminated structure according to the present invention is manufactured by supplying raw material fine particles, which are generated by atomizing a raw material solution, to a film deposition chamber using a carrier gas to form a crystalline oxide film having a corundum structure on a substrate placed in the film deposition chamber, and then doping the crystalline oxide film with a surface smoothing agent to reduce the root mean square roughness (RMS), which is the surface roughness of the crystalline oxide film, to 0.1 μm or less.

[0052] Figure 1 shows an example of a film deposition apparatus 101 that can be used to manufacture a laminated structure according to the present invention. The film deposition apparatus 101 includes a misting unit 120 that atomizes a raw material solution to generate mist, a carrier gas supply unit 130 that supplies a carrier gas to transport the mist, a film deposition unit 140 that heat-treats the mist to deposit a film on a substrate, and a transport unit 109 that connects the particle atomization unit 120 and the film deposition unit 140 and transports the mist by the carrier gas. Furthermore, the operation of the film deposition apparatus 101 may be controlled by a control unit (not shown) that controls the whole or a part of the film deposition apparatus 101. Details of the film deposition apparatus 101 will be described in the embodiments described later.

[0053] More specifically, a crystalline oxide film can be formed by supplying raw material fine particles generated from a raw material solution in which the raw material compound is dissolved into a film deposition chamber and reacting the raw material compound in the film deposition chamber. The solvent of the raw material solution is preferably water or hydrogen peroxide. When impurity doping is performed on the thin film, the raw material compound can be subjected to a thermal reaction in the presence of a dopant raw material. The dopant raw material is preferably included in the raw material solution and is atomized together with the raw material compound. In this application, in addition to n-type and p-type dopants for exhibiting conductivity, elements that provide a surface smoothing effect are also referred to as dopants.

[0054] The method for forming a crystalline oxide film is not particularly limited, but for example, it can be formed by thermally reacting a raw material compound that combines one or more metals selected from gallium compounds, iron compounds, indium compounds, aluminum compounds, vanadium compounds, titanium compounds, chromium compounds, rhodium compounds, iridium compounds, nickel compounds, and cobalt compounds in accordance with the composition of the crystalline oxide film. This allows for the crystal growth of a crystalline oxide film on a substrate from the substrate side. The above metal compounds may be organometallic complexes (e.g., acetylacetonate complexes, carbonyl complexes, ammine complexes, hydride complexes) or halides (fluoride, chloride, bromide, or iodide) for each metal, or, for example, metallic gallium or metallic indium may be used as starting materials and converted into gallium compounds and indium compounds immediately before film formation. In addition, gallium dissolved in an acid such as hydrochloric acid or hydrobromic acid can also be used as a gallium compound.

[0055] Furthermore, an acid may be mixed into the raw material solution. Examples of the acid include hydrogen halides such as hydrobromic acid, hydrochloric acid, and hydroiodic acid; halogen oxoacids such as hypochlorous acid, chlorous acid, hypobromous acid, bromous acid, hypoiodic acid, and iodic acid; formic acid; nitric acid; and the like. A base may also be mixed into the raw material solution. Examples of the base include potassium hydroxide, sodium hydroxide, ammonia, calcium hydroxide, barium hydroxide, magnesium hydroxide, copper hydroxide, and iron hydroxide. Among these, ammonia is particularly preferred because it has a low boiling point and therefore leaves no residue when the solution is heated.

[0056] In the laminated structure and method for manufacturing the laminated structure according to the present invention, the doping treatment is performed by including a surface smoothing agent in the raw material solution. By performing the doping treatment by including a surface smoothing agent in the raw material solution, a crystalline laminated structure having a crystalline oxide film with a surface roughness of 0.1 μm or less can be manufactured efficiently and industrially advantageously.

[0057] The surface smoothing agent is not particularly limited as long as it can reduce the root mean square roughness (RMS) of the crystalline oxide film to 0.1 μm or less. However, in the method for producing a laminated structure according to the present invention, it is preferably an organic compound, and more preferably an alcohol or a diketone. A laminated structure having a smoother surface can be produced more effectively and stably. Here, examples of alcohols include methanol, ethanol, propanol, as well as diols such as ethylene glycol, propylene glycol, and diethylene glycol, and triols such as glycerin, and any of these may be used. Examples of diketones include diacetyl, acetylacetone, 2,5-hexanedione, and dimedone, and any of these may be used.

[0058] When alcohols or diketones are used as surface smoothing agents, carbon (C) is introduced into the film, suppressing the deterioration of surface roughness. It is thought that C enters the intercellular spaces of the crystal lattice, thereby easing lattice distortion. It is also possible that the surface smoothing agent molecules induce steric hindrance on the substrate surface, promoting planar crystal growth.

[0059] The surface smoothing agent may be added directly to the aqueous solution containing the raw material compound, or it may be added to the aqueous solution containing the raw material compound after the surface smoothing agent has been dissolved in water and the pH has been adjusted beforehand.

[0060] In the laminated structure according to the present invention, the C content in the crystalline oxide film is 2 × 10 17 ~2×10 20 (atoms / cm 3 ) is preferable, 3 × 10 17 ~1 × 10 20 (atoms / cm 3 ) is more preferable, 4 × 10 17 ~8×10 19 (atoms / cm 3 ) is the most preferable.

[0061] Furthermore, in the method for manufacturing a laminated structure according to the present invention, methanol or acetylacetone is most preferably used as a surface smoothing agent. By using methanol or acetylacetone, the surface of a crystalline oxide film mainly composed of α-Ga2O3 can be made extremely smooth. The amount of surface smoothing agent added is not particularly limited, but it is preferably 10% or less by volume in the raw material solution, more preferably 7% or less, and most preferably in the range of 3 to 0.001%. By using it within this preferred range, it can function as a surface smoothing agent, thereby making the surface of the crystalline oxide film smooth.

[0062] Examples of dopant raw materials for inducing conductivity in crystalline oxide films include elemental metals or compounds of impurities to be doped (e.g., halides, oxides, hydroxides). For controlling electronic conductivity, n-type dopants such as Ge, Sn, Si, Ti, Zr, Hf, V, and Nb, and p-type dopants such as Cu, Ir, Rh, Sn, and Ag can be considered, but are not limited to these.

[0063] The thermal reaction only requires that the raw material fine particles react upon heating, and the reaction conditions are not particularly limited. They can be appropriately set depending on the raw materials and the resulting film. For example, the heating temperature can be in the range of 100 to 600°C, preferably in the range of 200 to 600°C, and more preferably in the range of 300 to 550°C.

[0064] The thermal reaction may be carried out under any of the following conditions: vacuum, non-oxygen atmosphere, reducing gas atmosphere, air atmosphere, or oxygen atmosphere, and should be set appropriately depending on the material to be deposited. The reaction pressure may also be atmospheric pressure, pressurized pressure, or reduced pressure, but deposition under atmospheric pressure is preferred because it simplifies the apparatus configuration.

[0065] As described above, a crystalline oxide film with a root mean square roughness (RMS) of 0.1 μm or less can be used as a buffer layer. That is, a first crystalline oxide film is further deposited on a substrate on which a second crystalline oxide film with a root mean square roughness (RMS) of 0.1 μm or less has been deposited. Because the surface of the second crystalline oxide film is flat, defects and dislocations in the film formed on this film are greatly reduced. If the obtained first crystalline oxide film is used in a semiconductor device, a semiconductor device with excellent semiconductor properties can be obtained. The C concentration in the second crystalline oxide film is 2 × 10⁻¹⁶ 17 ~2×10 20 (atoms / cm 3 It is preferable that the C concentration in the first crystalline oxide film is 2 × 10. 17 ~2×10 20 (atoms / cm 3) or 2 × 10 17 (atoms / cm 3 The following is also acceptable. This is because while C is necessary to achieve surface flatness, it is not particularly necessary to achieve excellent semiconductor properties.

[0066] In the crystalline oxide according to the present invention, annealing treatment may be performed after film formation. The temperature of the annealing treatment is not particularly limited, but is preferably 600°C or lower, more preferably 550°C or lower, and most preferably 500°C or lower. By performing the annealing treatment at such a preferred temperature, the electrical resistance of the crystalline oxide film can be more preferably reduced. The treatment time for the annealing treatment is not particularly limited, but is preferably 10 seconds to 10 hours, and more preferably 10 seconds to 1 hour.

[0067] In the laminated structure according to the present invention, the crystalline oxide film may be peeled off from the substrate. The peeling means is not particularly limited and may be a known means. Examples of peeling methods include peeling by applying mechanical impact, peeling by applying heat and utilizing thermal stress, peeling by applying vibration such as ultrasonic waves, and peeling by etching. By peeling, the crystalline oxide film can be obtained as a self-supporting film.

[0068] (Example of a crystalline layered structure) Figure 2 shows a preferred example of a laminated structure according to the present invention and a semiconductor device using the same. In the example in Figure 2, a crystalline oxide film 203 is formed on a substrate 201. The crystalline oxide film 203 is constructed by laminating an insulating thin film 203a and a conductive thin film 203b in order from the substrate 1 side. A gate insulating film 205 is formed on the conductive thin film 203b. A gate electrode 207 is formed on the gate insulating film 205. In addition, source and drain electrodes 209 are formed on the conductive thin film 203b so as to sandwich the gate electrode 207. With this configuration, the depletion layer formed on the conductive thin film 203b can be controlled by the gate voltage applied to the gate electrode 207, enabling transistor operation (FET device).

[0069] Semiconductor devices formed using the multilayer structure according to the present invention include transistors such as MIS, HEMT, and IGBT, TFTs, Schottky barrier diodes utilizing semiconductor-metal junctions, PN or PIN diodes combined with other P layers, and light-emitting / receiving elements. The multilayer structure according to the present invention is useful for improving the characteristics of these devices. [Examples]

[0070] The present invention will be described in detail below with reference to examples, but this is not intended to limit the present invention.

[0071] (Example 1) The film deposition apparatus 101 used in this embodiment will be explained with reference to Figure 1. The film deposition apparatus 101 includes a hot plate 108 on which a substrate 110, which is the sample to be deposited on, is placed and heated; carrier gas sources 102a and 102b for supplying carrier gas; flow control valves 103a and 103b for adjusting the flow rate of carrier gas sent from the carrier gas sources 102a and 102b; a particulate source 104 in which the raw material solution 104a is contained; a container 105 in which water 105a is placed; an ultrasonic transducer 106 attached to the bottom of the container 105; and a film deposition chamber 107 made of quartz. By making the film deposition chamber 107 out of quartz, the inclusion of impurities originating from the apparatus into the thin film formed on the substrate 110 is suppressed.

[0072] An aqueous solution of gallium bromide and tin chloride was prepared so that the atomic ratio of tin to gallium was 1:0.05. The concentration of gallium bromide was 0.1 mol / L. To promote the dissolution of tin chloride, 10% by volume of 48% hydrobromic acid solution was added. Furthermore, 0.016% methanol was mixed in as a surface smoothing agent.

[0073] As the substrate 110, a c-plane sapphire substrate with a diameter of 4 inches (100 mm) was placed on a hot plate 108 and heated until the substrate temperature reached 500°C. Next, flow control valves 103a and 103b were opened to supply carrier gas from carrier gas sources 102a and 102b into the deposition chamber 107. After the atmosphere in the deposition chamber 107 was sufficiently replaced with carrier gas, the total flow rate of the carrier gas was adjusted to 26 L / min. Oxygen gas was used as the carrier gas.

[0074] Next, the ultrasonic transducer 106 was vibrated at 2.4 MHz, and the vibrations were propagated through water 105a to the raw material solution 104a, thereby atomizing the raw material solution 104a and generating raw material nanoparticles. These raw material nanoparticles were introduced into the deposition chamber 107 by a carrier gas, and a thin film was formed on the sample 110 by a CVD reaction on the deposition surface of the sample 110. The deposition time was 180 minutes.

[0075] The phase of the deposited thin film was identified. Identification was performed using a thin-film XRD diffractometer by performing a 2θ / ω scan at an angle of 15 to 95 degrees. The measurement was performed using CuKα radiation. As a result, the formed thin film was found to be α-Ga2O3 with a corundum structure. Furthermore, the film thickness of the thin film in this example was measured using an interferometric film thickness gauge and was found to be 6.0 μm.

[0076] (Comparative example) Film formation was carried out without mixing methanol into the raw material solution. Specifically, an aqueous solution was prepared by adding tin chloride to 0.1 mol / L gallium bromide so that the atomic ratio of tin to gallium was 1:0.05, and a 48% hydrobromic acid solution was added at a volume ratio of 10%. Film formation was carried out in the same manner as in Example 1, except that this was used as the raw material solution. As a result of evaluation, it was confirmed that the film was α-Ga2O3 with a corundum structure, and the film thickness was 5.8 μm.

[0077] (Reference example 2) As the raw material solution, an aqueous solution of tin chloride was prepared by mixing 0.02 mol / L gallium iodide with tin chloride so that the atomic ratio of tin to gallium was 1:0.007, and 2% by volume of a 35% hydrochloric acid solution was added. Furthermore, 0.003% methanol was mixed in as a surface smoothing agent. Film formation was carried out in the same manner as in Example 1, except that this was used as the raw material solution. As a result of evaluation, it was confirmed that the film was α-Ga2O3 with a corundum structure, and the film thickness was 1.3 μm.

[0078] (Example 3) As a raw material solution, metallic gallium was dissolved in hydrochloric acid to prepare a gallium solution with a concentration of 0.05 mol / L. To this, an aqueous solution of tin chloride was prepared so that the atomic ratio of tin to gallium was 1:0.01, and a 35% hydrochloric acid solution was added by volume to 1%. Furthermore, 0.008% methanol was mixed in as a surface smoothing agent. Film formation was carried out in the same manner as in Example 1, except that this was used as the raw material solution. As a result of evaluation, it was confirmed that the film was α-Ga2O3 with a corundum structure, and the film thickness was 3.1 μm.

[0079] (Example 4) In Example 1, ethanol was used instead of methanol for film formation. Otherwise, the film formation was carried out in the same manner as in Example 1. As a result of evaluation, it was confirmed that the film was α-Ga2O3 having a corundum structure, and the film thickness was 6.1 μm.

[0080] (Example 5) In Example 1, oxalic acid was used instead of methanol for film formation. Otherwise, the film was formed using the same method as in Example 1. Evaluation confirmed that the film was α-Ga2O3 with a corundum structure, and the film thickness was 6.3 μm.

[0081] (Example 6) In Example 1, acetylacetone was used instead of methanol for film formation. Otherwise, the film was formed using the same method as in Example 1. Evaluation confirmed that the film was α-Ga2O3 with a corundum structure, and the film thickness was 6.0 μm.

[0082] (Example 7) In Example 6, the film was formed using acetylacetone at a concentration of 2.9%. Otherwise, the film was formed using the same method as in Example 1. Evaluation confirmed that the film was α-Ga2O3 with a corundum structure, and the film thickness was 5.9 μm.

[0083] (Example 8) Prior to the experiment, an aqueous solution of acetylacetone and ammonia was prepared with a molar ratio of acetylacetone:ammonia = 1:1. This aqueous solution was used as the acetylacetone in Example 7 to form the film. Otherwise, the film was formed using the same method as in Example 1. As a result of the evaluation, it was confirmed that the material was α-Ga2O3 with a corundum structure, and the film thickness was 6.4 μm.

[0084] (Example 9) The film was fabricated in the same manner as in Example 1, except that the film deposition time was set to 20 minutes. As a result of the evaluation, it was confirmed that the material was α-Ga2O3 with a corundum structure, and the film thickness was 0.55 μm.

[0085] (evaluation) The root mean square surface roughness (RMS) of α-Ga2O3 thin film samples obtained in Examples 1, 3-9, Reference Example 2, and Comparative Example was measured using an atomic force microscope (AFM). Furthermore, the carbon content in the films was investigated using SIMS. The results are shown in Table 1.

[0086] [Table 1]

[0087] As shown in Table 1, the sample without the surface smoothing agent exhibited significant surface irregularities, while the sample with the surface smoothing agent showed an RMS value of several nm, indicating a film with excellent surface smoothness. Simultaneously, the C concentration in the film was very high, which is thought to have contributed to the surface smoothing effect.

[0088] (Example 10) Except for a film deposition time of 10 minutes, the film was deposited in the same manner as in Example 1, and the resulting film was designated as the second crystalline oxide film. Subsequently, the raw material solution was changed to one that did not contain methanol, and film deposition was carried out to deposit a 5.4 μm thick α-Ga2O3 film as the first crystalline oxide film. X-ray diffraction measurements were performed on the obtained sample to evaluate its crystallinity. Specifically, the rocking curve of the (0006) plane diffraction peak of α-Ga2O3 was measured, and its full width at half maximum was determined. The obtained full width at half maximum was 11 seconds, confirming that the film had excellent crystallinity.

[0089] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0090] 101...Film deposition apparatus, 102a...Carrier gas source, 102b... Dilution carrier gas source, 103a... Flow control valve, 103b...Flow control valve, 104...Particulate matter source, 104a...Raw material solution, 105...Container, 105a...Water, 106...Ultrasonic transducer, 107...Film deposition chamber, 108...Hot plate, 109...Conveying unit, 109a...Supply pipe, 110...Substrate (crystalline substrate), 112...Exhaust port, 116...Oscillator, 120...Microparticle formation section, 130...Carrier gas supply section, 140...Film formation section, 201...Underlayment substrate, 203...Crystalline oxide film, 203a...Insulating thin film 203b...conductive thin film, 205...gate insulating film, 207...gate electrode, 209…Source and drain electrodes.

Claims

1. A laminated structure comprising a first crystalline oxide film having a corundum structure and a second crystalline oxide film having a corundum structure, The first crystalline oxide film is located on the second crystalline oxide film, The first and second crystalline oxide films contain a metal element, and the atomic ratio of gallium in the metal element is 0.5 or more. The second crystalline oxide film contains at least carbon (C) as an impurity, The C concentration in the second crystalline oxide film is 7.1 × 10 １７ ~2 x 10 ２０ / cm ３ And, The laminated structure is characterized in that the first crystalline oxide film is formed on the second crystalline oxide film, which has a surface root mean square roughness (RMS) of 0.1 μm or less, by thermally reacting raw material fine particles generated by micronizing a raw material solution.

2. The laminated structure according to claim 1, characterized in that the thickness of the first crystalline oxide film is 1 μm or more.

3. The area of ​​the first crystalline oxide film is 100 mm². ２ The laminated structure according to claim 1, characterized in that it is as described above.

4. The laminated structure according to claim 1, characterized in that the thickness of the second crystalline oxide film is 6 μm or less.

5. The laminated structure according to claim 1, further comprising a base substrate, wherein the base substrate is a c-plane sapphire substrate.

6. A semiconductor device comprising the laminated structure described in claim 1.

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