Crystalline stacked structure, semiconductor device, and method for manufacturing a crystalline stacked structure

Abstract

To provide a crystalline laminated structure excellent in crystallinity and excellent in semiconductor properties, especially, pressure resistance when applied to a semiconductor device, and a method for manufacturing the crystalline laminated structure, capable of obtaining such a crystalline laminated structure by an industrially advantageous method.SOLUTION: A crystalline laminated structure includes a crystalline oxide film using aluminum and one or more metal elements except aluminum as a main component and including a first crystalline oxide film having a corundum structure and an a-axis lattice constant of 4.94-5.02 Å and a second crystalline oxide film served as a crystalline oxide film formed on the first crystalline oxide film and using gallium as a main component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, gallium oxide (Ga2O3) has attracted attention as a semiconductor material. Gallium oxide is known to have five crystal forms: α, β, γ, δ, and ε. Among these, the metastable phase α-Ga2O3 has a very large band gap of 5.3 eV and is attracting attention as a material for power semiconductors.

[0003] For example, Patent Document 1 discloses a semiconductor device formed from a substrate having a corundum-type crystal structure, a semiconductor layer having a corundum-type crystal structure, and an insulating film having a corundum-type crystal structure, in which an α-Ga2O3 film is deposited as a semiconductor layer on a sapphire substrate. Furthermore, Patent Document 2 discloses a semiconductor device comprising an n-type semiconductor layer mainly composed of a crystalline oxide semiconductor having a corundum structure, a p-type semiconductor layer mainly composed of an inorganic compound having a hexagonal crystal structure, and electrodes, in which, in an example, a diode is fabricated by forming an α-Ga2O3 film having a metastable phase corundum structure as the n-type semiconductor layer and an α-Rh2O3 film having a hexagonal crystal structure as the p-type semiconductor layer on a c-plane sapphire substrate.

[0004] Incidentally, it is known that in these semiconductor devices, better properties can be obtained when there are fewer crystal defects in the material. In particular, power semiconductors require excellent dielectric strength, so it is desirable to reduce crystal defects. This is because the dielectric breakdown field characteristics are affected by the number of crystal defects. However, since α-Ga2O3 is a metastable phase, single crystal substrates have not been put into practical use, and it is generally formed by heteroepitaxial growth on a sapphire substrate. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-72533 [Patent Document 2] Japanese Patent Publication No. 2016-25256 [Patent Document 3] Patent No. 6784870 [Patent Document 4] Japanese Patent Publication No. 2021-31358 [Patent Document 5] International Publication No. 2020 / 194802 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in such cases, it is known that a large number of crystal defects are present due to the difference in lattice constants with sapphire. To reduce such crystal defects in α-Ga2O3, a method of forming a buffer layer between the sapphire and α-Ga2O3 layers has been reported. However, since power semiconductors require high voltage resistance, further reduction of crystal defects is necessary. In response to this, Patent Document 3 discloses a method of reducing crystal defects in α-Ga2O3 by using α-Cr2O3 as a buffer layer. However, this method is not yet industrially satisfactory because it requires many steps, such as heating the substrate to a very high temperature of over 1000°C and polishing the surface after the buffer layer is formed. Furthermore, Patent Documents 3, 4, and 5 also disclose solid solutions consisting of α-Al2O3 and α-Fe2O3 as buffer layer materials. However, effective compositions and specific manufacturing methods for Ga2O3 systems have not been disclosed, and have not even been considered.

[0007] The present invention has been made to solve the above problems, and aims to provide a crystalline multilayer structure that has excellent crystallinity and semiconductor properties, particularly excellent voltage resistance, when applied to semiconductor devices, and a method for manufacturing such a crystalline multilayer structure that can be obtained in an industrially advantageous way.

Means for Solving the Problem

[0008] The present invention has been made to achieve the above object, and is a crystalline oxide film mainly composed of aluminum and one or more metal elements other than aluminum, having a corundum structure, and having a lattice constant of the a-axis of 4.94 to 5.02 Å. And a crystalline laminated structure including a second crystalline oxide film on the first crystalline oxide film and mainly composed of gallium.

[0009] According to such a crystalline laminated structure, there are few crystal defects and dislocations, excellent crystallinity, excellent surface smoothness, and excellent semiconductor characteristics, particularly breakdown voltage characteristics, when applied to a semiconductor device.

[0010] At this time, the one or more metal elements other than aluminum in the first crystalline oxide film can be any of iron, titanium, indium, and rhodium.

[0011] Thereby, a crystalline laminated structure having more excellent crystallinity and surface smoothness is obtained.

[0012] At this time, the crystal defect density on the surface of the second crystalline oxide film is 1.0×10 , , 2 ,

[0015] , / cm 2 The following crystalline laminated structure can be obtained.

[0013] Further, a crystalline laminated structure in which the X-ray rocking curve half-value width of the (104) plane of the second crystalline oxide film is 500 seconds or less can be obtained.

[0014] The crystalline laminated structure according to the present invention has such excellent crystal quality, few crystal defects, small mosaicity, and small warpage, and becomes a high-quality film having even higher dielectric breakdown field characteristics and the like.

[0015] At this time, the surface area of the second crystalline oxide film is 100 mm 2The crystalline laminated structure may be of the above size, or have a diameter of 2 inches (50 mm) or more.

[0016] This results in a large-area crystalline oxide film with excellent crystallinity.

[0017] In this case, the semiconductor device can include the above-described crystalline layered structure.

[0018] This provides semiconductor devices with excellent semiconductor properties, particularly in terms of voltage resistance.

[0019] The present invention also provides a method for manufacturing a crystalline laminated structure, comprising the steps of: using a solution containing aluminum, one or more metal elements other than aluminum, and acetylacetone as raw materials, forming a first crystalline oxide film having a corundum structure and mainly composed of aluminum and one or more metal elements other than aluminum on a substrate, either directly or via another layer, by a mist CVD method, wherein the steps include: adjusting the ratio of aluminum and one or more metal elements other than aluminum in the solution to form the first crystalline oxide film having a lattice constant of 4.94 to 5.02 Å along the a-axis; and forming a second crystalline oxide film mainly composed of gallium on the first crystalline oxide film, either directly or via another layer.

[0020] This method for manufacturing crystalline laminated structures allows for the inexpensive and industrially advantageous production of crystalline laminated structures that exhibit excellent crystallinity with few crystal defects and dislocations, as well as excellent surface smoothness, and superior semiconductor properties, particularly voltage resistance, when applied to semiconductor devices, without requiring high-temperature processes exceeding 1000°C.

[0021] In this case, one or more metallic elements other than aluminum can be any of iron, titanium, indium, or rhodium.

[0022] This makes it possible to more reliably obtain crystalline laminated structures with excellent crystallinity and surface smoothness. [Effects of the Invention]

[0023] As described above, the crystalline laminated structure of the present invention exhibits excellent crystallinity with few crystal defects and dislocations, as well as excellent surface smoothness, resulting in superior semiconductor properties, particularly in breakdown voltage, when applied to semiconductor devices. The manufacturing method of the crystalline laminated structure of the present invention makes it possible to obtain a crystalline laminated structure with excellent crystallinity with few crystal defects and dislocations, as well as excellent surface smoothness, resulting in superior semiconductor properties, particularly in breakdown voltage, when applied to semiconductor devices. [Brief explanation of the drawing]

[0024] [Figure 1] This is a schematic diagram of a cross-section of a crystalline laminated structure according to the present invention. [Figure 2] This is a schematic diagram showing an example of a semiconductor device according to the present invention. [Figure 3] This is a schematic diagram showing an example of a film deposition apparatus (mist CVD apparatus) suitably used for manufacturing crystalline laminated structures according to the present invention. [Figure 4] This figure illustrates an example of a misting section used in a film deposition apparatus (mist CVD apparatus) according to the present invention. [Figure 5] This is an AFM image of the surface of the crystalline layered structure obtained in the present invention. [Modes for carrying out the invention]

[0025] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0026] As described above, there has been a need for crystalline multilayer structures with excellent crystallinity and semiconductor properties, particularly excellent voltage resistance, when applied to semiconductor devices, as well as a method for manufacturing such crystalline multilayer structures that can be obtained in an industrially advantageous manner.

[0027] As a result of diligent research into the above-mentioned problems, the present inventors have discovered that a crystalline laminated structure comprising a first crystalline oxide film mainly composed of aluminum and one or more metal elements other than aluminum, having a corundum structure and a lattice constant of 4.94 to 5.02 Å in the a-axis, and a second crystalline oxide film mainly composed of gallium, on the first crystalline oxide film, results in a structure with fewer crystal defects and dislocations, excellent crystallinity, excellent surface smoothness, and excellent semiconductor properties, particularly withstand voltage, when applied to a semiconductor device, thus completing the present invention.

[0028] The present inventors have also discovered that a method for manufacturing a crystalline laminated structure, comprising the steps of: using a solution containing aluminum, one or more metal elements other than aluminum, and acetylacetone as raw materials, and forming a first crystalline oxide film having a corundum structure mainly composed of aluminum and one or more metal elements other than aluminum on a substrate, either directly or via other layers, by mist CVD, wherein the first crystalline oxide film has an a-axis lattice constant of 4.94 to 5.02 Å by adjusting the ratio of aluminum and one or more metal elements other than aluminum in the solution; and forming a second crystalline oxide film mainly composed of gallium on the first crystalline oxide film, either directly or via other layers, makes it possible to obtain a crystalline laminated structure with few crystal defects and dislocations, excellent crystallinity, and excellent surface smoothness, and excellent semiconductor properties, particularly withstand voltage, when applied to a semiconductor device, and thus completed the present invention.

[0029] The following explanation will be given with reference to the drawings.

[0030] [Crystalline layered structure] The crystalline laminated structure according to the present invention comprises a first crystalline oxide film and a second crystalline oxide film. The first crystalline oxide film is a crystalline oxide film mainly composed of aluminum and one or more metal elements other than aluminum, having a corundum structure and a lattice constant of 4.94 to 5.02 Å along the a-axis. The second crystalline oxide film is provided on the first crystalline oxide film and is a crystalline oxide film mainly composed of gallium.

[0031] As shown in Figure 1(a), the first embodiment of the crystalline laminated structure 500 according to the present invention includes the first crystalline oxide film 502 and the second crystalline oxide film 501. Since the a-axis lattice constant of the first crystalline oxide film 502 is close to that of the second crystalline oxide film 501, it has fewer crystal defects and dislocations, exhibits excellent crystallinity, and also has excellent surface smoothness.

[0032] There are no particular restrictions on the size of the crystalline layered structure, but the surface area of ​​the crystalline oxide film must be 100 mm². 2 If the diameter is 2 inches (50 mm) or larger, a large-area film with good crystallinity can be obtained, which is preferable.

[0033] A second embodiment of the crystalline laminated structure 500 according to the present invention may include a substrate 503, as shown in Figure 1(b). Since the first crystalline oxide film 502 is thermodynamically stable, it can be grown without being excessively affected by the substrate. As a result, the first crystalline oxide film 502 has few defects and dislocations. Therefore, when a second crystalline oxide film 501 is heteroepitaxially grown on this film, the second crystalline oxide film 501 has few defects and dislocations and is of high quality.

[0034] The substrate 503 is not particularly limited as long as it serves as a support for the crystalline oxide film described above. The material is not particularly limited, and known substrates can be used, and may be organic compounds or inorganic compounds. Examples include polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluororesin, metals such as iron, aluminum, stainless steel, and gold, quartz, glass, calcium carbonate, gallium oxide, and ZnO. In addition to these, single crystal substrates such as silicon, sapphire, lithium tantalate, lithium niobate, SiC, GaN, iron oxide, and chromium oxide can be used, and such single crystal substrates are desirable in the crystalline laminated structure according to the present invention. This allows for the creation of a higher quality crystalline laminated structure. In particular, sapphire substrates, lithium tantalate substrates, and lithium niobate substrates are relatively inexpensive and industrially advantageous. When using a single crystal substrate, the plane orientation of the main surface (film deposition surface) of the substrate is not particularly limited. When using a substrate with a crystalline structure such as a sapphire substrate, the surface orientation of the main surface to which the film is deposited can be the c-plane, a-plane, r-plane, m-plane, etc. Furthermore, these planes may have an off-angle. The range of the off-angle is not particularly limited, but it can be within ±12° of the just-plane.

[0035] The thickness of the substrate 503 is preferably 100 to 5000 μm. Within this range, handling is easy, and thermal resistance during film formation can be suppressed, making it easier to obtain a high-quality film.

[0036] As shown in Figure 1(c), another layer 504 may be interposed between the substrate 503 and the first crystalline oxide film 502. Also, as shown in Figure 1(d), another layer 504 may be interposed between the first crystalline oxide film 502 and the second crystalline oxide film 501. Furthermore, the first crystalline oxide film 502 may be sandwiched between the other layer 504. The other layer is a layer with a different composition from the substrate and is also called a buffer layer. The other layer 504 (buffer layer) may be any of the following: a crystalline oxide film, a semiconductor film, an insulating film, a metal film, etc. Suitable materials include, for example, Al2O3, Ga2O3, Cr2O3, Fe2O3, In2O3, Rh2O3, V2O3, Ti2O3, Ir2O3, etc., and solid solutions of these may also be used. The thickness of the other layer 504 is preferably 0.1 μm to 2 μm.

[0037] (First crystalline oxide film) The first crystalline oxide film according to the present invention has a corundum-type crystal structure. Due to its translational symmetry, the corundum-type crystal structure is characterized by lattice constants of the a-axis and c-axis. In the present invention, the lattice constant of the a-axis is characterized by being 4.94 to 5.02 Å. The lattice constant can be appropriately determined by X-ray diffraction (XRD). Furthermore, the lattice constants used herein are values ​​at around room temperature (20 to 30°C).

[0038] The first crystalline oxide film according to the present invention also mainly comprises at least aluminum and one or more metal elements other than aluminum. The metal elements other than aluminum can be appropriately selected from iron, indium, vanadium, titanium, chromium, rhodium, iridium, nickel, cobalt, and the like.

[0039] In this invention, iron, titanium, indium, and rhodium are particularly preferred. If iron is selected, the composition formula should be (Al x Fe 1-x When )2O3 is used, it is preferable that the range of x is 0.06 to 0.34. If titanium is selected, the composition formula is (Al x Ti 1-x)When it is Al₂O₃, the range of x is preferably 0.33 to 0.54. When indium is selected, the composition formula is (Al x In 1-x )₂O₃, and when rhodium is selected, the composition formula is (Al x Rh 1-x )₂O₃, and the range of x is preferably 0.28 to 0.51. Within such a range, it is possible to more reliably and stably make the lattice constant of the a-axis of the first crystalline oxide film be 4.94 to 5.02 Å. These compositions can be determined by known methods such as atomic emission spectrometry, mass spectrometry, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, energy-dispersive X-ray fluorescence spectrometry, etc.

[0040] In the present invention, "mainly composed of aluminum and one or more metal elements other than aluminum" means that 50 to 100% of the components other than oxygen in the film consist of aluminum and one or more metal elements other than aluminum.

[0041] The thickness of the first crystalline oxide film is preferably 0.1 μm to 2 μm. Within such a range, it is possible to more reliably and stably make the lattice constant of the a-axis of the first crystalline oxide film be 4.94 to 5.02 Å.

[0042] (Second crystalline oxide film) The second crystalline oxide film according to the present invention is a crystalline oxide film mainly composed of gallium. In the present invention, "mainly composed of gallium" means that 50 to 100% of the components other than oxygen in the film are gallium. The metal components other than gallium may include, for example, one or more metals selected from iron, indium, aluminum, vanadium, titanium, chromium, rhodium, iridium, nickel, and cobalt.

[0043] The crystalline oxide film may contain dopant elements. Examples include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium, or p-type dopants such as copper, silver, tin, iridium, rhodium, or magnesium, but are not particularly limited. The concentration of the dopant is, for example, about 1 × 10⁻⁶ 16 / cm 3 ~1 × 10 22 / cm 3 It may be approximately 1 × 10 17 / cm 3 Even at the following low concentrations, approximately 1 × 10⁻⁶ 20 / cm 3 Higher concentrations than those mentioned above are also acceptable.

[0044] The thickness of the second crystalline oxide film is not particularly limited, but is preferably 1 μm or more. The upper limit is not particularly limited. The upper limit may be, for example, 100 μm or less, preferably 50 μm or less, and more preferably 20 μm or less.

[0045] The crystal structure of the second crystalline oxide film is not particularly limited, but a corundum structure is preferred. Multiple crystal structures may be present, or it may be polycrystalline, but a single crystal or a uniaxially oriented film is preferred.

[0046] The crystal defect density on the surface of the second crystalline oxide film is 1.0 × 10⁻⁶. 6 / cm 2 The following is preferable: The surface crystal defect density can be evaluated by planar TEM observation (plan view). For example, when performing planar TEM observation of a semiconductor film surface, a general transmission electron microscope can be used. The test specimen used for TEM observation is the surface of the semiconductor film, for example, a measurement field of view of 50 × 50 μm. 2 A device that allows observation of the range is preferable. More specifically, a measurement field of view of 4.1 × 3.1 μm. 2The specimen can be processed by ion milling so that eight or more areas are observable and the thickness around the measurement field of view is 150 nm. The crystal defect density can then be evaluated from the planar TEM image of the surface of the specimen obtained in this way. If the crystal defect density is low and it is difficult to observe crystal defects with planar TEM observation, other known methods, such as etch pit evaluation by wet etching, can also be used.

[0047] Furthermore, a known method for evaluating crystal defects and domains involves performing X-ray rocking curve (XRC) measurements on the (006) and (104) planes and evaluating them using their full width at half maximum (FWHM). In XRC measurements, it is common to correct the warp of the sample using a vacuum chuck or the like before measurement, but correction is often difficult when the amount of warp is large. For this reason, the X-ray rocking curve FWHM (hereinafter referred to as "XRC FWHM") can be said to reflect not only crystal defects and domains but also the amount of warp. In particular, the XRC FWHM of the (104) plane is suitable as an evaluation method for semiconductor films because it reflects all kinds of defects such as through-edge dislocations and through-helix dislocations, the presence of regions (domains) with different tilt (inclination of the crystal axis in the growth orientation) and twist (rotation of the crystal axis within the surface plane) (mosaicity), and the state of warp. The XRC full width at half maximum (FWHM) of the (104) plane on the surface of the semiconductor film of the present invention is preferably small, more preferably 500 seconds or less, more preferably 150 seconds or less, even more preferably 100 seconds or less, particularly preferably 50 seconds or less, and most preferably 40 seconds or less. The XRC FWHM of the (104) plane may be the same as the FWHM specific to the X-ray source used for measurement, but in practice, 30 seconds or less is preferable. An XRC FWHM within the above range results in fewer crystal defects, less mosaicism, and less warping, and as a result, a high-quality film with even higher dielectric breakdown field characteristics can be obtained.

[0048] The XRC profile of the (10⁴) plane can be measured using a general XRD instrument. After adjusting 2θ, ω, χ, and φ on the XRD instrument to align it so that the peak of the (10⁴) plane of α-Ga₂O₃ is obtained, the measurement can be performed under conditions such as ω = 15.5 to 19.5°, ω step size of 0.005°, and counting time of 0.5 seconds. This measurement is preferably performed after converting the CuKα line to parallel monochromatic light using a Ge(O₂₂) asymmetric reflection monochromator. The XRC full width at half maximum in the (10⁴) plane XRC profile can then be determined by performing a peak search after smoothing the profile using XRD analysis software.

[0049] [Semiconductor device] Figure 2 shows an example of a semiconductor device according to the present invention. In the example of the semiconductor device 100 shown in Figure 2, a crystalline oxide film 103 is formed on a substrate 101. The crystalline oxide film 103 is constructed by stacking an insulating thin film 103a and a conductive thin film 103b in order from the substrate 101 side. A gate insulating film 105 is formed on the conductive thin film 103b. A gate electrode 107 is formed on the gate insulating film 105. In addition, source and drain electrodes 109 are formed on the conductive thin film 103b so as to sandwich the gate electrode 107. With this configuration, the depletion layer formed on the conductive thin film 103b can be controlled by the gate voltage applied to the gate electrode 107, enabling transistor operation (FET device).

[0050] When the crystalline laminated structure according to the present invention is applied to a semiconductor device, at least a portion of the second crystalline oxide film according to the present invention can be used as the crystalline oxide film 103 in the semiconductor device 100 shown in Figure 2. The second crystalline oxide film according to the present invention also has excellent surface smoothness and exhibits excellent semiconductor properties, particularly withstand voltage, when applied to a semiconductor device, resulting in a semiconductor device with excellent semiconductor properties, especially withstand voltage.

[0051] Semiconductor devices formed using the crystalline 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 crystalline multilayer structure according to the present invention is useful for improving the characteristics of these devices.

[0052] [Method for manufacturing crystalline laminated structures] The crystalline laminated structure according to the present invention, as described above, is manufactured by forming a first crystalline oxide film on a substrate directly or via another layer using a mist CVD method, with a solution containing at least aluminum, one or more metal elements other than aluminum, and acetylacetone as raw materials, and then forming a second crystalline oxide film mainly composed of gallium oxide on the crystalline oxide film directly or via another layer. The method for manufacturing the crystalline laminated structure according to the present invention will be described in detail below. Here, "mist" as used in the present invention refers to a general term for fine liquid particles dispersed in a gas, and includes what are called fog, droplets, etc.

[0053] (Film forming equipment) First, let's describe the film deposition apparatus. Figure 3 shows an example of a film deposition apparatus used in the mist CVD method, which is necessary for depositing the first crystalline oxide film. The film deposition apparatus 201 includes at least a misting unit 220 that atomizes the raw material solution 204a to generate mist, a carrier gas supply unit 230 that supplies a carrier gas to transport the mist, a supply pipe 209 that connects the misting unit 220 and the film deposition chamber 207 and through which the mist is transported by the carrier gas, and a film deposition chamber 207 that heat-treats the mist supplied from the supply pipe 209 along with the carrier gas to deposit a film on the film deposition substrate 210.

[0054] (Misting section) In the misting unit 220, the raw material solution 204a is atomized to generate mist. The misting means is not particularly limited as long as it can atomize the raw material solution 204a, and any known misting means may be used, but it is preferable to use a misting means using ultrasonic vibration, because it can atomize more stably.

[0055] An example of such a misting unit 220 is shown in Figure 4. The misting unit 220 may include a mist generating source 204 containing a raw material solution 204a, a container 205 containing a medium capable of transmitting ultrasonic vibrations, such as water 205a, and an ultrasonic transducer 206 attached to the bottom of the container 205. More specifically, the mist generating source 204, consisting of the container containing the raw material solution 204a, can be housed in the container 205 containing the water 205a using a support (not shown). The ultrasonic transducer 206 may be installed at the bottom of the container 205, and the ultrasonic transducer 206 may be connected to an oscillator 216. When the oscillator 216 is activated, the ultrasonic transducer 206 vibrates, and ultrasonic waves are transmitted into the mist generating source 204 via the water 205a, causing the raw material solution 204a to be atomized.

[0056] (Raw material solution) The first raw material solution for forming a crystalline oxide film contains aluminum and one or more metal elements other than aluminum. As the metal elements other than aluminum, for example, one or more metals selected from iron, indium, vanadium, titanium, chromium, rhodium, nickel, and cobalt can be used. These metal elements can be dissolved or dispersed in the solvent in the form of complexes or salts. Examples of salt forms include metal chloride salts, metal bromide salts, metal iodide salts, and other halide salts. Alternatively, solutions of the above metals dissolved in hydrogen halides such as hydrobromic acid, hydrochloric acid, and hydroiodic acid can also be used as salt solutions. Examples of complex forms include acetylacetonate complexes, carbonyl complexes, ammine complexes, and hydride complexes. The metal concentration in the raw material solution 204a is not particularly limited and can be 0.005 to 1 mol / L, for example. By appropriately adjusting the mixing ratio of the metal elements, a crystalline oxide film of a desired composition can be obtained.

[0057] The first raw material solution for forming a crystalline oxide film also contains acetylacetone. Acetylacetone may be supplied as a solution, as a salt such as an ammonium salt, or as an acetylacetonate complex of the above metal.

[0058] The solvent for the first crystalline oxide film formation raw material solution is not particularly limited in material as long as it can be atomized, and may be an inorganic or organic material. Examples include organic solvents or water.

[0059] The raw material solution for forming the first crystalline oxide film may contain additives such as hydrohalic acid and oxidizing agents. Examples of hydrohalic acid include hydrobromic acid, hydrochloric acid, and hydroiodic acid, with hydrobromic acid or hydroiodic acid being preferred. Examples of oxidizing agents include peroxides such as hydrogen peroxide (H2O2), sodium peroxide (Na2O2), barium peroxide (BaO2), and benzoyl peroxide (C6H5CO)2O2, as well as organic peroxides such as hypochlorous acid (HClO), perchloric acid, nitric acid, ozonated water, peracetic acid, and nitrobenzene.

[0060] It is preferable that the temperature during the preparation, mixing, and dissolution of the raw material solutions described above be 20°C or higher.

[0061] Alternatively, one solution containing only aluminum as a metallic element and another containing only other metallic elements can be prepared separately, and these can be mixed after atomization to form a film. In this case, the composition of the resulting crystalline oxide film can be controlled not only by the concentration of metal in the solution as described above, but also by the flow rate of the carrier gas, improving the flexibility of film formation. Furthermore, it is possible to prevent unnecessary reactions caused by the coexistence of two or more metallic elements in the solution.

[0062] When a second crystalline oxide film is formed by the mist CVD method, the raw material solution for forming the second crystalline oxide film is not particularly limited as long as it contains gallium and can be atomized; it may be an inorganic or organic material. Besides gallium, metals or metal compounds are preferably used as materials. For example, a solution containing one or more metals selected from iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, and cobalt may be used. As such a raw material solution, a solution in which the metal is dissolved or dispersed in an organic solvent or water in the form of a complex or salt is preferably used. Examples of salt forms include metal chloride salts, metal bromide salts, metal iodide salts, and other halide salts. Furthermore, a solution of the above metal dissolved in a hydrogen halide such as hydrobromic acid, hydrochloric acid, or hydroiodic acid can also be used as a salt solution. Examples of complex forms include acetylacetonate complexes, carbonyl complexes, ammine complexes, and hydride complexes. An acetylacetonate complex can also be formed by mixing acetylacetone with the aforementioned salt solution. The metal concentration in the starting material solution 204a is not particularly limited and can be 0.005 to 1 mol / L, for example. The mixing and dissolution temperature is preferably 20°C or higher.

[0063] The raw material solution for forming the second crystalline oxide film may contain additives such as hydrohalic acid and oxidizing agents. Examples of hydrohalic acid include hydrobromic acid, hydrochloric acid, and hydroiodic acid, with hydrobromic acid or hydroiodic acid being preferred. Examples of oxidizing agents include peroxides such as hydrogen peroxide (H2O2), sodium peroxide (Na2O2), barium peroxide (BaO2), and benzoyl peroxide (C6H5CO)2O2, as well as organic peroxides such as hypochlorous acid (HClO), perchloric acid, nitric acid, ozonated water, peracetic acid, and nitrobenzene.

[0064] The second raw material solution for forming the crystalline oxide film may contain a dopant. The dopant is not particularly limited. Examples include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium, or p-type dopants such as copper, silver, iridium, rhodium, or magnesium.

[0065] The above-mentioned raw material solution for forming the second crystalline oxide film shows an example of how the second crystalline oxide film is produced by the mist CVD method. However, in the present invention, the second crystalline oxide film may be formed by a known method other than the mist CVD method.

[0066] (Carrier gas supply department) As shown in Figure 3, the carrier gas supply unit 230 has a carrier gas source 202a for supplying carrier gas. In this case, it may also be equipped with a flow control valve 203a for adjusting the flow rate of carrier gas discharged from the carrier gas source 202a. Furthermore, a dilution carrier gas source 202b for supplying dilution carrier gas and a flow control valve 203b for adjusting the flow rate of dilution carrier gas discharged from the dilution carrier gas source 202b may also be provided as needed.

[0067] The type of carrier gas is not particularly limited and can be appropriately selected depending on the film to be deposited. Examples include inert gases such as oxygen, ozone, nitrogen, and argon, or reducing gases such as hydrogen gas and foaming gas. Furthermore, there may be one type of carrier gas or two or more types. For example, as a second carrier gas, a dilution gas obtained by diluting the same gas as the first carrier gas with another gas (for example, diluted 10 times) may be used, or air may be used. The flow rate of the carrier gas is not particularly limited. For example, when depositing a film on a substrate with a diameter of 2 inches (approximately 50 mm), the flow rate of the carrier gas is preferably 0.05 to 50 L / min, and more preferably 5 to 20 L / min.

[0068] (supply pipe) The film deposition apparatus 201 has a supply pipe 209 connecting the atomizing unit 220 and the film deposition chamber 207. In this case, the mist is transported from the mist source 204 of the atomizing unit 220 via the supply pipe 209 by a carrier gas and supplied into the film deposition chamber 207. The supply pipe 209 can be, for example, a quartz tube, a glass tube, or a resin tube.

[0069] (Film forming chamber) A film deposition substrate 210 is installed inside the film deposition chamber 207, and a heater 208 for heating the film deposition substrate 210 may be provided. The heater 208 may be located outside the film deposition chamber 207, as shown in Figure 3, or it may be located inside the film deposition chamber 207. The mist supplied from the supply pipe 209 passes through the piping inside the film deposition chamber 207 and is ejected from the nozzle towards the film deposition substrate 210 along with the carrier gas. An exhaust port 212 for exhaust gas may also be provided in the film deposition chamber 207 at a position that does not affect the supply of mist to the film deposition substrate 210. The film deposition substrate 210 may be placed on the top surface of the film deposition chamber 207 in a face-down configuration, or it may be placed on the bottom surface of the film deposition chamber 207 in a face-up configuration.

[0070] (Film deposition by mist CVD method) As described above, in the production of the crystalline laminated structure according to the present invention, at least a first crystalline oxide film is formed by the mist CVD method. The mist CVD method will be described below. The mist CVD method consists of a mist generation step in which a raw material solution is atomized in a misting section to generate mist; a carrier gas supply step in which a carrier gas for transporting the mist is supplied to the misting section; a transport step in which the mist is transported by the carrier gas from the misting section to the film formation chamber via a supply pipe connecting the misting section and the film formation chamber; and a film formation step in which the transported mist is heat-treated to form a film on a substrate.

[0071] The raw material solution 204a is placed in the mist generator 204, the film deposition substrate 210 is placed in the film deposition chamber 207, and the heater 208 is heated. Next, the flow control valves 203a and 203b are opened to supply carrier gas from carrier gas sources 202a and 202b into the film deposition chamber 207. After the atmosphere in the film deposition chamber 207 has been sufficiently replaced with carrier gas, the flow rate of the carrier gas and the flow rate of the dilution carrier gas are adjusted, respectively.

[0072] Next, in the mist generation process, the ultrasonic transducer 206 is vibrated, and the vibration is transmitted to the raw material solution 204a through the water 205a, thereby atomizing the raw material solution 204a and generating mist.

[0073] Next, as a carrier gas supply process, a carrier gas for transporting the mist is supplied to the misting unit 220.

[0074] Next, in the transport process, the mist is transported from the misting unit 220 to the film deposition chamber 207 by a carrier gas via a supply pipe 209 that connects the misting unit 220 and the film deposition chamber 207.

[0075] Next, in the film deposition process, the mist transported to the deposition chamber 207 is heated to generate a thermal reaction, thereby depositing a film on part or all of the surface of the film deposition substrate 210.

[0076] Thermal reactions require heating to advance the reaction of metals and other substances contained in the mist. Therefore, the temperature of the substrate surface during the reaction must be at least 400°C. However, unlike other CVD methods, the mist CVD method requires the raw materials to reach the substrate surface in a liquid mist state. As a result, the temperature of the substrate surface drops significantly. Consequently, the temperature of the substrate surface during the reaction differs from the temperature set in the apparatus. It is preferable to measure and control the temperature of the substrate surface during the reaction, but if this is difficult, the reaction can be simulated by introducing only a carrier gas or a water mist without solute, and the temperature can be measured as a substitute.

[0077] Furthermore, the thermal reaction also depends on the ambient temperature around the substrate. Therefore, it is desirable that the temperature of the nozzle and the inner wall of the deposition chamber be higher than room temperature. This is because it stabilizes the thermal reaction. For example, the nozzle temperature can be set to 50-250°C.

[0078] 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.

[0079] (Formation of a buffer layer) As described above, other layers (hereinafter referred to as "buffer layers") may be appropriately provided between the substrate and the first crystalline oxide film. The method for forming the buffer layer is not particularly limited, and it can be formed by known methods such as sputtering and vapor deposition. However, when using the mist CVD method described above, it is convenient as it can be formed simply by appropriately changing the raw material solution. Specifically, one or more metals selected from aluminum, gallium, chromium, iron, indium, rhodium, vanadium, titanium, and iridium can be suitably used as the raw material aqueous solution by dissolving or dispersing them in water in the form of a complex or salt. Examples of complex forms include acetylacetonate complexes, carbonyl complexes, ammine complexes, and hydride complexes. Examples of salt forms include metal chloride salts, metal bromide salts, and metal iodide salts. In addition, solutions of the above metals dissolved in hydrobromic acid, hydrochloric acid, hydroiodic acid, etc., can also be used as the aqueous salt solution. In this case as well, the solute concentration is preferably 0.005 to 1 mol / L, and the dissolution temperature is preferably 20°C or higher. For other conditions, the buffer layer can be formed in the same manner as described above. After depositing the buffer layer to a predetermined thickness, the film is deposited using the method described above.

[0080] In a special case of the buffer layer formation method, the same material as the second crystalline oxide film may be used. In this case, the deposition temperature of the buffer layer may be higher than that of the second crystalline oxide film. For example, the deposition temperature of the buffer layer may be 450°C and the deposition temperature of the second crystalline oxide film may be 400°C, or the buffer layer may be deposited at 500°C and the second crystalline oxide film at 450°C. Doing so will further improve the crystallinity of the second crystalline oxide film.

[0081] (Deposition of a second crystalline oxide film) When depositing a second crystalline oxide film by mist CVD, a gallium-based second crystalline oxide film, such as a gallium oxide film, can be deposited by using a raw material solution for the second crystalline oxide film and following the same procedure as for depositing the first crystalline oxide film. However, the second crystalline oxide film may also be deposited by known methods other than mist CVD.

[0082] (Heat treatment) The crystalline laminated structure according to the present invention may be heat-treated at 200 to 600°C. This further removes unreacted species in the film, resulting in a higher quality crystalline laminated structure. The heat treatment may be carried out in air, an oxygen atmosphere, or under an inert gas atmosphere such as nitrogen or argon. The heat treatment time can be determined as appropriate, but for example, it can be 5 to 240 minutes.

[0083] (Peeling) In the crystalline laminated structure according to the present invention, the first and second crystalline oxide films may be peeled off from the underlying substrate. Alternatively, the first crystalline oxide film can be peeled off from the crystalline laminated structure according to the present invention to obtain only the first crystalline oxide film or only the second crystalline oxide film. The peeling means is not particularly limited and may be 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 such peeling, a crystalline laminated structure consisting only of the first and second crystalline oxide films can be obtained, and each of the first and second crystalline oxide films can also be obtained as a self-supporting film. [Examples]

[0084] The present invention will be described in detail below with reference to examples, but this is not intended to limit the present invention.

[0085] [Example 1] Figure 3 is a schematic diagram of the film deposition apparatus 201 used in this embodiment. The film deposition apparatus 201 comprises a carrier gas source 202a for supplying carrier gas, a flow control valve 203a for adjusting the flow rate of carrier gas discharged from the carrier gas source 202a, a dilution carrier gas source 202b for supplying dilution carrier gas, a flow control valve 203b for adjusting the flow rate of dilution carrier gas discharged from the dilution carrier gas source 202b, a mist generator 204 containing raw material solution 204a, a container 205 containing water 205a, an ultrasonic transducer 206 attached to the bottom of the container 205, a film deposition chamber 207 equipped with a heater 208, and a quartz supply pipe 209 connecting the mist generator 204 to the film deposition chamber 207.

[0086] (Deposition of AlFeO film) A 4-inch (100 mm) c-plane sapphire substrate 210 was prepared for film deposition. This substrate was placed in the deposition chamber 207, the heater 208 was set to 450°C, the temperature was raised, and it was left for 30 minutes to stabilize the temperature inside the deposition chamber, including the nozzle.

[0087] Ultrapure water was used as the solvent, and AlCl3 and FeCl3 as the solutes. After mixing them to achieve concentrations of 0.012 mol / L for Al and 0.008 mol / L for Fe, 0.06 mol / L of a mixed solution of ammonia and acetylacetone (molar ratio 1:1) was added and the mixture was stirred at 60°C for 60 minutes to obtain the raw material solution 204a. Subsequently, flow control valves 203a and 203b were opened to supply carrier gas from carrier gas sources 202a and 202b into the deposition chamber 207. After thoroughly replacing the atmosphere in the deposition chamber 207 with carrier gas, the flow rate of the carrier gas was adjusted to 2 L / min and the flow rate of the dilution carrier gas to 4 L / min. Nitrogen was used as the carrier gas and oxygen as the dilution carrier gas.

[0088] Next, the ultrasonic transducer 206 was vibrated at 2.4 MHz, and the vibrations were propagated through water 205a to the raw material solution 204a, thereby atomizing the raw material solution 204a and generating a mist. This mist was introduced into the deposition chamber 207 via the supply pipe 209 using a carrier gas, and the mist was subjected to a thermal reaction on the deposition substrate 210 to form a thin film of AlFeO (the first crystalline oxide film) on the deposition substrate 210. The deposition time was 60 minutes.

[0089] (evaluation) The obtained thin film was evaluated using an XRD instrument (D8-DISCOVER, Bruker-AXS Corporation), and a peak separate from the substrate was observed at a lower angle than the substrate. The lattice constant of the a-axis, assuming a corundum structure, was 4.98 Å. Furthermore, elemental analysis by energy-dispersive X-ray fluorescence spectrometry revealed that the metallic components were approximately 20% Al and 80% Fe. The film thickness was measured using an optical interferometer and was approximately 200 nm.

[0090] (Deposition of GaO film) The film deposition substrate 210 obtained above was placed in the film deposition chamber 207, the heater 208 was set to 550°C and the temperature was raised, and it was left for 30 minutes to stabilize the temperature inside the film deposition chamber, including the nozzle.

[0091] A solution of ultrapure water as the solvent, GaCl3 as the solute, and a concentration of 0.02 mol / L was mixed with a 1:1 molar ratio of ammonia and acetylacetone at a concentration of 0.06 mol / L. The mixture was stirred at a temperature of 60°C for 60 minutes to obtain raw material solution 204a.

[0092] The raw material solution 204a was placed inside the mist generating source 204. Next, flow control valves 203a and 203b were opened to supply carrier gas from carrier gas sources 202a and 202b into the deposition chamber 207. After the atmosphere in the deposition chamber 207 was sufficiently replaced with carrier gas, the flow rate of the carrier gas was adjusted to 2 L / min and the flow rate of the dilution carrier gas was adjusted to 4 L / min. Nitrogen was used as the carrier gas.

[0093] Next, the ultrasonic transducer 206 was vibrated at 2.4 MHz, and the vibrations were propagated through water 205a to the raw material solution 204a, thereby atomizing the raw material solution 204a and generating a mist. This mist was introduced into the deposition chamber 207 via the supply pipe 209 using a carrier gas, and the mist was subjected to a thermal reaction on the deposition substrate 210 to form a thin film of gallium oxide (a second crystalline oxide film) on the deposition substrate 210. The deposition time was 60 minutes.

[0094] (evaluation) XRD evaluation of the gallium oxide thin film of the crystalline multilayer structure obtained as described above confirmed the formation of α-Ga2O3. XRC measurement of the (006) plane of α-Ga2O3 showed an XRC full width at half maximum of 10 seconds, indicating excellent crystallinity. Furthermore, XRC measurement of the (104) plane was performed. In practice, the axial alignment was adjusted by adjusting 2θ, ω, χ, and φ to obtain the peak of the (104) plane of α-Ga2O3. The conditions used were a tube voltage of 40kV, a tube current of 40mA, a collimator diameter of 0.5mm, an anti-scattering slit of 3mm, an ω range of 15.5~19.5°, an ω step width of 0.005°, and a counting time of 0.5 seconds. In addition, a Ge(022) asymmetric reflection monochromator was used as the X-ray source to obtain parallel monochromatic CuKα rays. The XRC full width at half maximum (FWHM) of the obtained (10⁴) plane XRC profile was determined by performing a peak search after smoothing the profile using XRD analysis software (Bruker-AXS, "LEPTOS" Ver4.03). As a result, the (10⁴) plane XRC FWHM of the α-Ga₂O₃ film was 129 seconds.

[0095] Using AFM, the film surface was examined in 1 × 1 μm in size. 2 The area was observed. The observation results are shown in Figure 5. An atomic-level step structure was obtained on the film surface. The mean square roughness (RMS) was 0.68 nm, which is extremely good.

[0096] To evaluate the surface crystal defect density, planar TEM observation (plan view) was performed. The sample was processed by ion milling so that the thickness around the measurement field of view was 150 nm. The obtained section was observed using a transmission electron microscope (Hitachi H-90001UHR-I) at an acceleration voltage of 300 kV to evaluate the crystal defect density. The actual measurement field of view was 4.1 × 3.1 μm. 2 Eight TEM images were observed, and the number of defects found within each was calculated. The results showed no crystal defects in the obtained TEM images, and the crystal defect density was 9.9 × 10⁻⁶. 5 / cm 2 It was found to be less than [amount].

[0097] [Example 2] In Example 1, film deposition and evaluation were performed in the same manner as in Example 1, except that the solute was mixed to a concentration of 0.002 mol / L for Al and 0.018 mol / L for Fe. The composition of the AlFeO film was approximately 6% Al and 94% Fe. The lattice constant of the a-axis, assuming a corundum structure, was 5.02 Å.

[0098] The XRC full width at half maximum (FWHM) of the (006) plane of the α-Ga2O3 film was 10 seconds, and the XRC FWHM of the (104) plane was 131 seconds. The RMS was 0.88 nm, and the crystal defect density was 9.9 × 10⁻⁶. 5 / cm 2 It was less than [amount missing].

[0099] [Example 3] In Example 1, film deposition and evaluation were performed in the same manner as in Example 1, except that the solute was mixed to a concentration of 0.014 mol / L for Al and 0.006 mol / L for Fe. The composition of the AlFeO film was approximately 34% Al and 66% Fe. The lattice constant of the a-axis, assuming a corundum structure, was 4.94 Å.

[0100] The XRC full width at half maximum (FWHM) of the (006) plane of the α-Ga2O3 film was 11 seconds, and the XRC FWHM of the (104) plane was 145 seconds. The RMS was 0.73 nm, and the crystal defect density was 9.9 × 10⁻⁶. 5 / cm 2 It was less than [amount missing].

[0101] [Comparative Example 1] In Example 1, film deposition and evaluation were performed in the same manner as in Example 1, except that the solute was mixed to a concentration of 0.001 mol / L for Al and 0.019 mol / L for Fe. The composition of the AlFeO film was approximately 3% Al and 97% Fe. The lattice constant of the a-axis, assuming a corundum structure, was 5.03 Å.

[0102] The XRC full width at half maximum (FWHM) of the (006) plane of the α-Ga2O3 film was 43 seconds, and the XRC FWHM of the (104) plane was 635 seconds. The RMS was 2.11 nm, and the crystal defect density was 2.2 × 10⁻⁶. 7 / cm 2That was the case.

[0103] [Comparative Example 2] In Example 1, film deposition and evaluation were performed in the same manner as in Example 1, except that the solute was mixed to a concentration of 0.016 mol / L for Al and 0.004 mol / L for Fe. The composition of the AlFeO film was approximately 58% Al and 42% Fe. The lattice constant of the a-axis, assuming a corundum structure, was 4.87 Å.

[0104] The XRC full width at half maximum (FWHM) of the (006) plane of the α-Ga2O3 film was 51 seconds, and the XRC FWHM of the (104) plane was 567 seconds. The RMS was 2.57 nm, and the crystal defect density was 3.0 × 10⁻⁶. 7 / cm 2 That was the case.

[0105] [Example 4] In Example 1, film deposition and evaluation were performed in the same manner as in Example 1, except that the solutes were mixed to a concentration of 0.014 mol / L for AlCl3 and 0.006 mol / L for TiCl3. An AlTiO film was obtained, with a composition of approximately 41% Al and 59% Ti. The lattice constant of the a-axis, assuming a corundum structure, was 4.99 Å.

[0106] The XRC full width at half maximum (FWHM) of the (006) plane of the α-Ga2O3 film was 13 seconds, and the XRC FWHM of the (104) plane was 155 seconds. The RMS was 0.86 nm, and the crystal defect density was 9.9 × 10⁻⁶. 5 / cm 2 It was less than [amount missing].

[0107] [Example 5] In Example 1, film deposition and evaluation were performed in the same manner as in Example 1, except that the solutes were mixed to a concentration of 0.018 mol / L for AlCl3 and 0.002 mol / L for InCl3. An AlInO film was obtained, with a composition of approximately 72% Al and 28% In. The lattice constant of the a-axis, assuming a corundum structure, was 4.96 Å.

[0108] The XRC full width at half maximum (FWHM) of the (006) plane of the α-Ga2O3 film was 14 seconds, and the XRC FWHM of the (104) plane was 164 seconds. The RMS was 0.88 nm, and the crystal defect density was 9.9 × 10⁻⁶. 5 / cm 2 It was less than [amount missing].

[0109] [Example 6] In Example 1, film deposition and evaluation were performed in the same manner as in Example 1, except that the solutes were mixed to a concentration of 0.014 mol / L for AlCl3 and 0.006 mol / L for RhCl3. An AlRhO film was obtained, with a composition of approximately 34% Al and 66% Rh. The lattice constant of the a-axis, assuming a corundum structure, was 5.00 Å.

[0110] The XRC full width at half maximum (FWHM) of the (006) plane of the α-Ga2O3 film was 12 seconds, and the XRC FWHM of the (104) plane was 133 seconds. The RMS was 0.76 nm, and the crystal defect density was 9.9 × 10⁻⁶. 5 / cm 2 It was less than [amount missing].

[0111] As described above, according to the embodiments of the present invention, a crystalline laminated structure was obtained that has few crystal defects and dislocations, excellent crystallinity, excellent surface smoothness, and excellent semiconductor properties, particularly withstand voltage, when applied to a semiconductor device.

[0112] This specification includes the following embodiments: [1]: A crystalline laminated structure comprising a first crystalline oxide film having a corundum structure and a lattice constant of 4.94 to 5.02 Å in the a-axis, and a second crystalline oxide film having gallium as the main component, which is a crystalline oxide film on the first crystalline oxide film. [2]: The crystalline laminated structure of [1], wherein one or more metallic elements other than aluminum in the first crystalline oxide film are iron, titanium, indium, and rhodium. [3]: The crystal defect density on the surface of the second crystalline oxide film is 1.0 × 10 6 / cm 2The crystalline laminated structure according to [1] or [2] above, which is as follows: [4]: The crystalline stacked structure according to [1], [2], or [3], wherein the X-ray rocking curve full width at half maximum of the (104) plane of the second crystalline oxide film is 500 seconds or less. [5]: The surface area of ​​the second crystalline oxide film is 100 mm² 2 A crystalline laminated structure of any of the above [1] to [4], which is 2 inches (50 mm) or larger in diameter. [6]: A semiconductor device characterized by including any of the crystalline layered structures described in [1] to [5] above. [7]: A method for producing a crystalline laminated structure, comprising the steps of: using a solution containing aluminum, one or more metal elements other than aluminum, and acetylacetone as raw materials, forming a first crystalline oxide film having a corundum structure mainly composed of aluminum and one or more metal elements other than aluminum on a substrate, either directly or via another layer, by a mist CVD method, wherein the steps include: adjusting the ratio of aluminum to one or more metal elements other than aluminum in the solution to form the first crystalline oxide film having a lattice constant of 4.94 to 5.02 Å along the a-axis; and forming a second crystalline oxide film mainly composed of gallium on the first crystalline oxide film, either directly or via another layer. [8]: A method for manufacturing the crystalline laminated structure described in [7] above, wherein one or more metal elements other than aluminum are iron, titanium, indium, and rhodium.

[0113] 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]

[0114] 500...Crystalline layered structure, 501...Second crystalline oxide film, 502...First crystalline oxide film, 503...Substrate, 504...Another layer, 100... Semiconductor equipment, 101... Substrate, 103... Crystalline oxide film, 103a...Insulating thin film, 103b...Conductive thin film, 105...Gate insulating film, 107...Gate electrode, 109...Source / drain electrodes, 110...Laminated structure, 201...Film deposition apparatus, 202a...Carrier gas source, 202b... Dilution carrier gas source, 203a... Flow control valve, 203b...Flow control valve, 204...Mist source, 204a...Raw material solution, 205...container, 205a...water, 206...ultrasonic vibrator, 207...film-forming chamber, 208...Heater, 209...Supply tube, 210...Substrate for film deposition, 216...Oscillator, 212...Exhaust port, 220...Misting unit, 230...Carrier gas supply unit.

Claims

1. A crystalline oxide film having aluminum and one or more metal elements other than aluminum as its main components, having a corundum structure and a lattice constant of 4.94 to 5.02 Å in the a-axis, and A crystalline oxide film on the first crystalline oxide film, comprising a second crystalline oxide film mainly composed of gallium, The crystalline laminated structure is characterized in that the first crystalline oxide film is one of the following: (Al x Fe 1-x) 2 O 3 (where x = 0.06 to 0.34), (Al x Ti 1-x) 2 O 3 (where x = 0.33 to 0.54), (Al x In 1-x) 2 O 3 (where x = 0.63 to 0.75), or (Al x Rh 1-x) 2 O 3 (where x = 0.28 to 0.51).

2. The crystal defect density on the surface of the second crystalline oxide film is 1.0 × 10⁻⁶. ６ / cm ２ The crystalline laminated structure according to claim 1, characterized in that it is as follows.

3. The crystalline laminated structure according to claim 1 or 2, characterized in that the X-ray rocking curve full width at half maximum of the (104) plane of the second crystalline oxide film is 500 seconds or less.

4. The surface area of ​​the second crystalline oxide film is 100 mm². ２ A crystalline laminated structure according to any one of claims 1 to 3, characterized in that it is 2 inches (50 mm) or larger in diameter.

5. A semiconductor device comprising a crystalline laminated structure as described in any one of claims 1 to 4.

6. A process for forming a first crystalline oxide film having a corundum structure and mainly composed of aluminum and one or more metal elements other than aluminum, directly or via another layer, on a substrate by mist CVD using a solution containing aluminum, one or more metal elements other than aluminum, and acetylacetone as raw materials, wherein the first crystalline oxide film has an a-axis lattice constant of 4.94 to 5.02 Å, and A method for manufacturing a crystalline laminated structure, comprising the step of forming a second crystalline oxide film mainly composed of gallium on the first crystalline oxide film directly or via another layer.

7. The method for manufacturing a crystalline laminated structure according to claim 6, characterized in that the one or more metal elements other than aluminum are iron, titanium, indium, and rhodium.

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