Crystal film

Abstract

To provide a high-quality crystal film useful for a semiconductor device or the like and having impurities such as Si reduced.SOLUTION: In a production method of a crystal film for forming a crystal film on a substrate by crystal growth from a raw material, the raw material contains GaCl3 and a rugged part composed of concavities or protrusions is formed directly or with another layer in-between on the substrate for crystal growth. A crystal film is then formed on the rugged part under the crystal growth condition of a partial pressure of the raw material of 1 kPa or higher. The crystal film contains gallium-containing crystalline metal oxide as its main component and has an Si content of 2×1015 cm-3 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a crystalline film useful for semiconductor devices. [Background technology]

[0002] Semiconductor devices using gallium oxide (Ga2O3), which has a large band gap, are attracting attention as next-generation switching elements that can achieve high breakdown voltage, low loss, and high heat resistance, and are expected to be applied to power semiconductor devices such as inverters. In addition, due to the wide band gap, a wide range of applications as light emitting and receiving devices such as LEDs and sensors are also expected. In particular, among gallium oxides, α-Ga2O3 and the like, which have a corundum structure, can control the band gap by mixing indium and aluminum, individually or in combination, according to Non-Patent Document 1, and constitute an extremely attractive material system as an InAlGaO-based semiconductor. Here, InAlGaO-based semiconductors are defined as In X Al Y Ga Z O3 (0≦X≦2, 0≦Y≦2, 0≦Z≦2, X+Y+Z=1.5 to 2.5) (Patent Document 9, etc.), and can be viewed as the same material family containing gallium oxide.

[0003] However, because the most stable phase of gallium oxide is the β-gallium structure, it is difficult to form a crystalline film with the metastable corundum structure without using a special deposition method. Furthermore, α-Ga2O3, which has a corundum structure, is a metastable phase, making it impossible to use bulk substrates grown by melt growth. Therefore, sapphire, which has the same crystalline structure as α-Ga2O3, is currently used as the substrate. However, due to the large lattice mismatch between α-Ga2O3 and sapphire, α-Ga2O3 crystalline films grown heteroepitaxially on sapphire substrates tend to have a high dislocation density. Furthermore, many challenges remain, not only in the formation of corundum-structured crystalline films, but also in improving deposition rate and crystalline quality, suppressing cracks and abnormal growth, suppressing twinning, and preventing substrate cracking due to warping. Given these circumstances, several studies are currently being conducted on the deposition of crystalline semiconductors with a corundum structure.

[0004] Patent Document 1 describes a method for producing an oxide crystal thin film by mist CVD using gallium or indium bromide or iodide. Patent Documents 2 to 4 describe a multilayer structure in which a semiconductor layer having a corundum crystal structure and an insulating film having a corundum crystal structure are stacked on a base substrate having a corundum crystal structure. Furthermore, as in Patent Documents 5 to 7, film formation by mist CVD using an ELO substrate or void formation has also been investigated. However, none of these methods are yet satisfactory in terms of film formation rate, and a film formation method with an excellent film formation rate has been awaited. Patent Document 8 describes the formation of a gallium oxide film having a corundum structure by halide vapor phase epitaxy (HVPE) using at least a gallium source and an oxygen source. However, since α-Ga2O3 is a metastable phase, it is difficult to form a film like β-Ga2O3, and there are still many problems to be solved industrially. Furthermore, Patent Documents 10 and 11 describe the formation of a gallium oxide film having a surface area of ​​9 μm2 by ELO crystal growth using a PSS substrate. 2 and the dislocation density is 5×10 6 cm -2However, to fully utilize the performance of gallium oxide in power devices, it is necessary to reduce not only the dislocation density but also impurities such as Si, that is, the Si content is reduced to 1×10 16 cm -3 It is necessary to satisfy the following requirements, and a method for easily producing such impurity-free crystalline films is desired. Patent Documents 1 to 11 are all patents or patent application publications by the present applicants, and are currently under investigation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5397794 [Patent Document 2] Patent No. 5343224 [Patent Document 3] Patent No. 5397795 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-72533 [Patent Document 5] Japanese Patent Application Laid-Open No. 2016-100592 [Patent Document 6] Japanese Patent Application Laid-Open No. 2016-98166 [Patent Document 7] Japanese Patent Application Laid-Open No. 2016-100593 [Patent Document 8] Japanese Patent Application Laid-Open No. 2016-155714 [Patent Document 9] International Publication No. 2014 / 050793 [Patent Document 10] U.S. Publication No. 2019 / 0057865 [Patent Document 11] Japanese Patent Application Publication No. 2019-034883 [Non-patent literature]

[0006] [Non-Patent Document 1] Kentaro Kaneko, "Growth and Properties of Gallium Oxide-Based Alloy Thin Films with Corundum Structure," Doctoral Dissertation, Kyoto University, March 2013 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a high-quality crystal film useful for semiconductor devices and the like. [Means for solving the problem]

[0008] As a result of extensive research to achieve the above object, the present inventors have found that when Ga2O3 is formed using GaCl3 at a partial pressure of 1 kPa or more, the Si content is 2×10 15 cm -3 It has been found that the following crystalline film can be easily obtained, and that such a crystalline film can solve all of the above-mentioned conventional problems at once.

[0009] Furthermore, after obtaining the above findings, the present inventors conducted further studies and have now completed the present invention.

[0010] That is, the present invention relates to the following inventions. [1] A crystalline film containing crystalline metal oxide containing gallium as the main component, with a Si content of 2×10 15 cm -3 A crystalline film characterized by the following: [2] The crystalline film according to [1] above, wherein the crystalline metal oxide has a corundum structure. [3] C content is 5×10 16 cm -3 The crystal film according to [1] or [2] above, which is: [4] The crystal film according to any one of [1] to [3] above, having a thickness of 10 μm or more. [5] The crystal film according to any one of [1] to [4] above, having a thickness of 25 μm or more. [6] Surface area is 10 cm 2 The crystal film according to any one of the above [1] to [5]. [7] The crystalline film according to any one of [1] to [6] above, wherein the crystalline film is a semiconductor film. [8] A semiconductor device including a crystalline film, wherein the crystalline film is the crystalline film according to any one of [1] to [7] above. [9] The semiconductor device according to [8] above, which is a power device.

[10] A semiconductor system including a semiconductor device, wherein the semiconductor device is the semiconductor device described in [8] or [9]. [Effects of the Invention]

[0011] The crystalline film of the present invention is a high-quality crystalline film useful for semiconductor devices and the like. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a halide vapor phase epitaxy (HVPE) apparatus that is preferably used in the present invention. [Figure 2] 1 is a diagram schematically showing the surface of a concave-convex portion formed on the surface of a substrate preferably used in the present invention. [Figure 3] 1 is a schematic diagram showing the surface of a concave-convex portion formed on the surface of a substrate preferably used in the present invention. [Figure 4] 1 is a schematic diagram showing one embodiment of a concave-convex portion formed on the surface of a substrate suitably used in the present invention. [Figure 5] FIG. 1 is a photograph of a crystal film in an example. [Figure 6] FIG. 10 is a diagram showing the results of SEM observation in a comparative example. [Figure 7] FIG. 10 is a diagram showing the results of SEM observation in a comparative example. [Figure 8] FIG. 1 is a diagram showing the results of SEM observation in an example. [Figure 9] FIG. 1 is a diagram schematically illustrating a preferred example of a power supply system. [Figure 10] FIG. 1 is a diagram schematically illustrating a preferred example of a system device. [Figure 11] FIG. 1 is a diagram schematically illustrating a preferred example of a power supply circuit diagram of a power supply device. DETAILED DESCRIPTION OF THE INVENTION

[0013] The crystal film of the present invention is a crystal film containing a crystalline metal oxide containing gallium as a main component, and the Si content is 2×10 15 cm -3 The present invention is characterized in that the Si content is a value measured by SIMS. In the present invention, it is preferable that the crystalline metal oxide has a corundum structure. In addition, in the present invention, the C content is 5×10 16 cm -3 The C content is a value measured by SIMS. In the present invention, the thickness of the crystal film is preferably 10 μm or more, more preferably 25 μm or more. The surface area of ​​the crystal film is preferably 10 cm or more. 2 It is preferable that it is 20cm or more. 2 In the present invention, the crystal film is preferably a semiconductor film.

[0014] The above-mentioned preferred crystalline film can be easily obtained by a method for producing a crystalline film in which a crystalline film containing a crystalline metal oxide containing gallium as a main component is formed on a substrate by crystal growth from a raw material, the raw material containing GaCl3, and the crystal growth is carried out under crystal growth conditions in which the partial pressure of the raw material is 1 kPa or more. A preferred method for producing the crystalline film will now be described.

[0015] In the present invention, the crystal growth is preferably carried out by the HVPE method. Also, in the present invention, the crystal growth is preferably carried out under crystal growth conditions with a film formation rate of 90 μm / hour or more, and more preferably under crystal growth conditions with a film formation rate of 100 μm / hour or more. In the present invention, for example, when the crystal growth is carried out by the HVPE method, it is preferable that the partial pressure of the source gas (GaCl gas or its precursor gas, etc.) is 1 kPa or more, and the partial pressure of the oxygen-containing source gas is 1.25 kPa or more. Also, in the present invention, the crystal growth is preferably carried out in an oxygen-containing atmosphere.

[0016] (substrate) The substrate is usually a crystalline substrate. The crystalline substrate is not particularly limited as long as it contains a crystalline material as a main component, and may be any known substrate. It may be an insulating substrate, a conductive substrate, or a semiconductor substrate. It may be a single crystal substrate or a polycrystalline substrate. Examples of the crystalline substrate include a substrate containing a crystalline material having a corundum structure as a main component, a substrate containing a crystalline material having a β-gallium structure as a main component, and a substrate containing a crystalline material having a hexagonal structure as a main component. The term "main component" refers to a substrate containing 50% or more of the crystalline material, preferably 70% or more, and more preferably 90% or more, of the crystalline material in terms of composition ratio in the substrate.

[0017] Examples of substrates containing a corundum-structured crystal as a main component include sapphire substrates and α-type gallium oxide substrates. Examples of substrates containing a β-gallium structured crystal as a main component include β-Ga2O3 substrates and mixed crystal substrates containing β-Ga2O3 and Al2O3. A suitable example of a mixed crystal substrate containing β-Ga2O3 and Al2O3 is a mixed crystal substrate containing more than 0% and 60% or less Al2O3 in atomic ratio. Examples of substrates having a hexagonal crystal structure include SiC substrates, ZnO substrates, and GaN substrates. Examples of other crystal substrates include Si substrates.

[0018] In the present invention, the crystal substrate is preferably a sapphire substrate. Examples of the sapphire substrate include a c-plane sapphire substrate, an m-plane sapphire substrate, and an a-plane sapphire substrate. The sapphire substrate may have an off-axis angle. The off-axis angle is not particularly limited, but is preferably 0° to 15°. The thickness of the crystal substrate is not particularly limited, but is preferably 50 to 2000 μm, and more preferably 200 to 800 μm.

[0019] In the present invention, it is preferable to form an uneven portion consisting of recesses or protrusions on the substrate directly or via another layer, and then form the crystal film on the uneven portion. The uneven portion is not particularly limited as long as it is composed of recesses or protrusions, and may be an uneven portion consisting of recesses or protrusions. Furthermore, the uneven portion may be formed of regular recesses or protrusions, or irregular recesses or protrusions. In the present invention, it is preferable that the uneven portion is formed periodically, and more preferably, it is patterned periodically and regularly. The shape of the uneven portion is not particularly limited, and examples include stripes, dots, meshes, and random shapes. In the present invention, dots or stripes are preferred. Furthermore, when the uneven portion is patterned periodically and regularly, it is preferable that the pattern shape of the uneven portion is a polygonal shape such as a triangle, a quadrangle (e.g., a square, rectangle, or trapezoid), a pentagon, or a hexagon, a circle, or an ellipse. When the concave-convex portion is formed in a dot pattern, the lattice shape of the dots is preferably a lattice shape such as a square lattice, an oblique lattice, a triangular lattice, a hexagonal lattice, etc., and more preferably a triangular lattice shape. The cross-sectional shape of the concave or convex portions of the concave-convex portion is not particularly limited, and examples thereof include a U-shape, an inverted U-shape, a wave shape, or a polygon such as a triangle, a quadrangle (for example, a square, a rectangle, or a trapezoid), a pentagon, or a hexagon.

[0020] The material constituting the protrusions is not particularly limited and may be a known material. It may be an insulating material, a conductive material, or a semiconductor material. The material may be amorphous, single crystal, or polycrystalline. Examples of materials constituting the protrusions include oxides, nitrides, or carbides of Si, Ge, Ti, Zr, Hf, Ta, Sn, etc., carbon, diamond, metals, and mixtures thereof. More specifically, examples include Si-containing compounds containing SiO2, SiN, or polycrystalline silicon as a main component, and metals having a melting point higher than the crystal growth temperature of the crystalline oxide (e.g., noble metals such as platinum, gold, silver, palladium, rhodium, iridium, and ruthenium). The content of the constituting material in the protrusions is preferably 50% or more, more preferably 70% or more, and most preferably 90% or more, in terms of composition ratio.

[0021] The convex portions may be formed by known means, such as photolithography, electron beam lithography, laser patterning, and subsequent etching (e.g., dry etching or wet etching). In the present invention, the convex portions are preferably stripe- or dot-shaped, and more preferably dot-shaped. In the present invention, the crystal substrate is also preferably a PSS (patterned sapphire substrate) substrate. The pattern shape of the PSS substrate is not particularly limited and may be any known pattern shape. Examples of the pattern shape include a cone, a bell, a dome, a hemisphere, a square, or a triangular pyramid. In the present invention, the pattern shape is preferably a cone. In addition, the pitch interval of the pattern shape is not particularly limited, but in the present invention, it is preferably 5 μm or less, and more preferably 1 μm to 3 μm. In the present invention, the formation of the convex portions is preferably carried out by forming a mask layer on the crystal substrate. The mask layer can be suitably formed by depositing a film of the mask layer material using a known film formation method such as vacuum deposition, CVD, or sputtering, and then processing it using the known patterning method described above. Examples of the material of the mask layer include the materials exemplified as the material of the convex portions. In the present invention, when a crystal film is produced using the mask layer, it is preferable to form the polycrystal at least on the mask layer, since this allows for a thicker and larger-area crystalline oxide layer to be obtained.

[0022] The recesses are not particularly limited, and may be made of the same material as the convex portions, or may be the substrate. In the present invention, the recesses are preferably a void layer provided on the surface of the substrate. The same means as the means for forming the convex portions can be used as the means for forming the recesses. The void layer can be formed on the surface of the substrate by providing grooves in the substrate using a known groove processing means. In the present invention, the void layer can be suitably formed, for example, by providing a mask layer by sputtering, and then patterning the mask layer using a known patterning processing means such as photolithography. The groove width, groove depth, terrace width, etc. of the void layer are not particularly limited and can be set appropriately as long as they do not impede the object of the present invention.

[0023] Preferred embodiments of the crystal substrate that can be suitably used in the present invention will be described below with reference to the drawings. FIG. 2 shows one embodiment of a concave-convex portion formed on the crystal growth surface of a crystal substrate according to the present invention. The concave-convex portion in FIG. 2 is composed of a crystal substrate 1 and a mask layer 4. FIG. 3 shows the surface of the concave-convex portion shown in FIG. 2 as viewed from the zenith direction. As can be seen from FIGS. 2 and 3, the mask layer 4 is formed on the crystal growth surface of the crystal substrate 1 and has dot-shaped holes. The crystal substrate 1 is exposed through the dot holes in the mask layer 4, and dot-shaped recesses 2b are formed in a triangular lattice pattern. The dot circles are spaced at regular intervals a. The period a is not particularly limited, but in the present invention, it is preferably 1 μm to 1 mm, and more preferably 5 μm to 300 μm. Here, the period a refers to the distance between the ends of adjacent dot circles. The mask layer 4 can be formed by depositing a material constituting the mask layer 4 and then processing it into a predetermined shape using a known method such as photolithography. Examples of materials constituting the mask layer 4 include oxides, nitrides, or carbides of Si, Ge, Ti, Zr, Hf, Ta, Sn, Al, etc., carbon, diamond, metals, and mixtures thereof. The method for forming the mask layer 4 is not particularly limited and may be a known method. Examples of methods for forming the mask layer 4 include vacuum deposition, CVD, and sputtering.

[0024] FIG. 4 shows one embodiment of the uneven portion provided on the crystal growth surface of a crystal substrate in the present invention. The uneven portion in FIG. 4 is composed of a crystal substrate 1 and a mask layer 4. The mask layer is formed in a striped pattern on the crystal growth surface of the crystal substrate 1, and the mask layer 4 forms recesses (grooves) 2b in a striped pattern. The mask layer 4 can be formed using known means such as photolithography. Examples of materials that can be used to form the mask layer 4 include oxides, nitrides, or carbides of Si, Ge, Ti, Zr, Hf, Ta, Sn, Al, etc., carbon, diamond, metals, or mixtures thereof.

[0025] The width and height of the convex portions (mask layer) of the uneven portion, the width and depth of the concave portions, and the spacing between them are not particularly limited, but in the present invention, the width of the convex portions (mask layer) is preferably about 1 μm to about 1 mm, more preferably about 5 μm to about 300 μm, and most preferably about 10 μm to about 100 μm. Also in the present invention, the height of the convex portions (mask layer) is preferably about 1 nm to about 10 μm, more preferably about 5 nm to about 1 μm, and most preferably about 10 nm to about 100 nm. Also in the present invention, the width of the concave portions is preferably about 1 μm to about 300 μm, more preferably about 3 μm to about 100 μm, and most preferably about 5 μm to about 50 μm. In the present invention, the depth of the recesses is preferably about 1 nm to about 1 mm, more preferably about 10 nm to about 300 μm, and most preferably about 20 nm to about 100 μm. By making the recesses and projections have these preferable depths, a better crystal film can be more easily obtained. The recesses and projections may be formed directly on the crystal substrate, or may be provided via another layer.

[0026] The crystal growth method is not particularly limited and may be any known method. Examples of the crystal growth method include CVD, MOCVD, MOVPE, mist CVD, mist epitaxy, MBE, HVPE, pulse growth, ALD, and sputtering. In the present invention, the crystal growth method is preferably mist CVD, mist epitaxy, or HVPE, and more preferably HVPE.

[0027] The present invention will be described in more detail below, taking as an example a case where the crystal film is formed using the HVPE method as the crystal growth means. Specifically, the HVPE method involves gasifying a metal source containing gallium and optionally reacting it with HCl gas to form GaCl gas, and then supplying the GaCl gas and an oxygen-containing source gas to the crystal substrate in a reaction chamber to form a film. When this gas is then supplied to the crystal substrate in a reaction chamber, it is preferable that a reactive gas is supplied to the crystal substrate and the film is formed under the flow of the reactive gas.

[0028] (metal source) The metal source is not particularly limited as long as it contains gallium and can be gasified, and may be a metal element or a metal compound. In the present invention, the metal source is most preferably gallium element. Furthermore, the metal source may be a gas, liquid, or solid, but in the present invention, the metal source is preferably a liquid.

[0029] The gasification means is not particularly limited and may be any known means as long as it does not impede the objectives of the present invention. In the present invention, the gasification is preferably carried out by halogenating the metal source. The halogenating agent used for the halogenation is not particularly limited as long as it can halogenate the metal source, and may be any known halogenating agent. Examples of the halogenating agent include halogen and hydrogen halide. Examples of the halogen include fluorine, chlorine, bromine, and iodine. Examples of the hydrogen halide include hydrogen fluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide. In the present invention, it is preferable to use hydrogen halide for the halogenation, and it is more preferable to use hydrogen chloride. In the present invention, it is preferable to carry out the gasification by supplying a halogen or hydrogen halide as a halogenating agent to the metal source and reacting the metal source with the halogen or hydrogen halide at a temperature equal to or higher than the vaporization temperature of the metal halide to produce a metal halide gas. The halogenation reaction temperature is not particularly limited, but in the present invention, for example, when the metal source is gallium and the halogenating agent is HCl, the temperature is preferably 900°C or lower, more preferably 700°C or lower, and most preferably 400°C to 700°C. The metal halide gas is not particularly limited as long as it contains a halide of the metal source gallium. Examples of the metal halide gas include gallium halides (fluorides, chlorides, bromides, iodides, etc.).

[0030] In the present invention, a gallium-containing metal source is gasified to form GaCl gas, and then the GaCl gas and the oxygen-containing source gas are supplied onto the substrate in the reaction chamber. In the present invention, the gasified gallium-containing metal source may be GaCl gas, or, for example, GaCl gas may be reacted with HCl gas before being supplied onto the substrate to form GaCl gas. In the present invention, a reactive gas is preferably supplied onto the substrate. The temperature for forming the crystal film is not particularly limited. However, in the present invention, when the metal source is gallium and the halogenating agent is HCl, the temperature is preferably 900°C or less, more preferably 700°C or less, and most preferably 400°C to 700°C. The oxygen-containing source gas may be, for example, one or more gases selected from O gas, CO gas, NO gas, NO gas, NO gas, NO gas, HO gas, or O gas. In the present invention, the oxygen-containing source gas is preferably one or more gases selected from the group consisting of O2, HO, and NO, and more preferably contains O2. The reactive gas is typically a gas with a different reactivity from the metal halide gas and the oxygen-containing source gas, and does not include an inert gas. Examples of the reactive gas include, but are not limited to, an etching gas. The etching gas is not particularly limited as long as it does not impede the objectives of the present invention, and may be any known etching gas. In the present invention, the reactive gas is preferably a halogen gas (e.g., fluorine gas, chlorine gas, bromine gas, or iodine gas), a hydrogen halide gas (e.g., hydrofluoric acid gas, hydrochloric acid gas, hydrogen bromide gas, or hydrogen iodide gas), hydrogen gas, or a mixed gas of two or more of these, preferably a hydrogen halide gas, and most preferably hydrogen chloride. The metal halide gas, the oxygen-containing source gas, and the reactive gas may each contain a carrier gas. Examples of the carrier gas include an inert gas such as nitrogen or argon. The partial pressure of the metal halide gas is not particularly limited, but in the present invention, the partial pressure is usually 1 kPa or more.The partial pressure of the oxygen-containing source gas is not particularly limited, but in the present invention, it is preferably 0.5 to 100 times the partial pressure of the metal halide gas, and more preferably 1 to 20 times. The partial pressure of the reactive gas is also not particularly limited, but in the present invention, it is preferably 0.1 to 5 times the partial pressure of the metal halide gas, and more preferably 0.2 to 3 times.

[0031] In the present invention, it is also preferable to supply a dopant-containing source gas to the substrate. The dopant-containing source gas is not particularly limited as long as it contains a dopant. The dopant is also not particularly limited, but in the present invention, the dopant preferably contains one or more elements selected from germanium, silicon, titanium, zirconium, vanadium, niobium, and tin, more preferably germanium, silicon, or tin, and most preferably germanium. By using such a dopant-containing source gas, the conductivity of the resulting film can be easily controlled. The dopant-containing source gas preferably contains the dopant in the form of a compound (e.g., a halide, an oxide, etc.), more preferably in the form of a halide. The partial pressure of the dopant-containing source gas is not particularly limited, but in the present invention, it is preferable that the partial pressure of the dopant-containing source gas is 1×10 of the partial pressure of the metal-containing source gas. -7 Preferably, the ratio is 2.5 × 10 to 0.1 times. -6 times ~7.5×10 -2 In the present invention, it is preferable that the dopant-containing source gas is supplied onto the substrate together with the reactive gas.

[0032] (crystalline film) The crystalline film is a crystalline film containing a crystalline metal oxide containing gallium as a main component, and the Si content is 2×10 15 cm -3The present invention is characterized by the following. In the present invention, the crystalline film preferably contains a single crystal of the crystalline metal oxide as a main component. Furthermore, in the present invention, the crystalline oxide may be a semiconductor. In the present invention, the crystalline metal oxide is most preferably Ga2O3 or a mixed crystal thereof. The crystalline structure of the crystalline metal oxide is not particularly limited. Examples of the crystalline structure of the crystalline oxide include a corundum structure, a β-gallia structure, a hexagonal structure (e.g., an ε-type structure), an orthorhombic structure (e.g., a κ-type structure), a cubic structure, and a tetragonal structure. In the present invention, the crystalline oxide preferably has a corundum structure, a β-gallia structure, or a hexagonal structure (e.g., an ε-type structure), and more preferably has a corundum structure. Note that the term "main component" means that the crystalline oxide preferably accounts for 50% or more, more preferably 70% or more, and even more preferably 90% or more of the total components of the crystalline film, in atomic ratio, and may be 100%. The thickness of the crystal film is not particularly limited, but is preferably 10 μm or more, more preferably 25 μm or more, and most preferably 50 μm or more. The surface area of ​​the crystal film is not particularly limited, but is preferably 10 cm 2 It is preferable that it is 20cm or more. 2 More preferably, it is equal to or greater than this.

[0033] The crystal film may contain a dopant. The dopant is not particularly limited and may be a known dopant, and may be either an n-type dopant or a p-type dopant. Examples of the n-type dopant include tin, germanium, silicon, titanium, zirconium, vanadium, niobium, or two or more elements thereof. Examples of the p-type dopant include Mg, H, Li, Na, K, Rb, Cs, Fr, Be, Ca, Sr, Ba, Ra, Mn, Fe, Co, Ni, Pd, Cu, Ag, Au, Zn, Cd, Hg, Ti, Pb, N, P, or two or more elements thereof. The content of the dopant in the crystal film is also not particularly limited, but is preferably 0.00001 atomic % or more, more preferably 0.00001 atomic % to 20 atomic %, and most preferably 0.00001 atomic % to 10 atomic %.

[0034] The crystalline film is particularly suitable for use in semiconductor devices, and is particularly useful in power devices. Examples of semiconductor devices formed using the crystalline film include MIS, HEMT, and MOS transistors, TFTs, Schottky barrier diodes using semiconductor-metal junctions, PN or PIN diodes combined with other P layers, and light-emitting and receiving elements. In the present invention, the crystalline film may be used directly together with the substrate in a semiconductor device, or may be peeled off from the substrate or other known means before being applied to the semiconductor device.

[0035] In addition to the above features, the semiconductor device can be suitably used as a power module, inverter, or converter using known means, and these semiconductor devices are also included in the present invention. The semiconductor device can also be suitably used in, for example, a semiconductor system using a power supply device. The power supply device can be fabricated from or as the semiconductor device by connecting it to a wiring pattern or the like using known means. FIG. 9 shows an example of a power supply system. FIG. 9 shows a power supply system configured using multiple power supply devices and a control circuit. The power supply system can be used in combination with an electronic circuit as shown in FIG. 10 for a system device. An example of a power supply circuit diagram for a power supply device is shown in FIG. 11. FIG. 11 shows the power supply circuit of a power supply device consisting of a power circuit and a control circuit. An inverter (composed of MOSFETs: A to D) switches DC voltage at high frequency to convert it to AC, then insulates and transforms it with a transformer, rectifies it with rectifier MOSFETs (A to B'), smooths it with DCLs (smoothing coils L1, L2) and a capacitor, and outputs a DC voltage. At this time, a voltage comparator compares the output voltage with a reference voltage, and a PWM control circuit controls the inverter and rectifier MOSFETs to achieve the desired output voltage. [Example]

[0036] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0037] Example 1 1. Formation of ELO mask A sapphire substrate (c-plane, off-angle 0.25°) with an α-Ga2O3 layer formed on its surface was used as the substrate, and a mask layer made of SiO2 was formed on the substrate using the sputtering method. The mask layer was then processed into a mask of the specified shape using photolithography. Specifically, the mask layer was processed so that openings (dots) (diameter: 5 μm) were arranged in a triangular lattice pattern on the substrate with a period (distance between the edges of adjacent dots) of 5 μm.

[0038] 2. Crystalline film formation 2-1.HVPE equipment The halide vapor phase epitaxy (HVPE) apparatus 50 used in this example will be described with reference to FIG. 1. The HVPE apparatus 50 includes a reaction chamber 51, a heater 52a for heating a metal source 57, and a heater 52b for heating a substrate secured to a substrate holder 56. The reaction chamber 51 also includes an oxygen-containing source gas supply pipe 55b, a reactive gas supply pipe 54b, and a substrate holder 56 for supporting the substrate. The reactive gas supply pipe 54b includes a metal-containing source gas (metal halide gas) supply pipe 53b, forming a double-pipe structure. The oxygen-containing source gas supply pipe 55b is connected to an oxygen-containing source gas supply source 55a, forming an oxygen-containing source gas flow path so that the oxygen-containing source gas can be supplied from the oxygen-containing source gas supply source 55a through the oxygen-containing source gas supply pipe 55b to the substrate secured to the substrate holder 56. Furthermore, reactive gas supply pipe 54b is connected to reactive gas supply source 54a, and forms a reactive gas flow path so that reactive gas can be supplied from reactive gas supply source 54a via reactive gas supply pipe 54b to a substrate fixed to substrate holder 56. Metal-containing source gas supply pipe 53b is connected to halogen-containing source gas supply source 53a, and the halogen-containing source gas is supplied to the metal source to become a metal-containing source gas, which is then supplied to the substrate fixed to substrate holder 56. Reaction chamber 51 is provided with a gas exhaust unit 59 that exhausts used gas, and further, a protective sheet 58 is attached to the inner wall of reaction chamber 51 to prevent precipitation of reactants.

[0039] 2-2. Preparation for film deposition A gallium (Ga) metal source 57 (with a purity of 99.99999% or more) was placed inside metal-containing source gas supply pipe 53b, and the sapphire substrate with the mask layer obtained in 1 above was placed as a substrate on substrate holder 56 inside reaction chamber 51. Thereafter, heaters 52a and 52b were operated to raise the temperature inside reaction chamber 51 to 570°C (near the Ga metal source) and 520°C (near the substrate holder).

[0040] 2-3. Film formation Hydrogen chloride (HCl) gas (purity 99.999% or higher) was supplied from a halogen-containing source gas supply source 53a to gallium (Ga) metal 57 disposed inside a metal source-containing gas supply pipe 53b. Gallium chloride (GaCl / GaCl) was generated by a chemical reaction between the Ga metal and the hydrogen chloride (HCl) gas. The resulting gallium chloride (GaCl / GaCl) and O gas (purity 99.99995% or higher) supplied from an oxygen-containing source gas supply source 55a were supplied onto the substrate through a reactive gas supply pipe 54b. Then, under the flow of HCl gas, the gallium chloride (GaCl / GaCl) and O gas were reacted on the substrate at atmospheric pressure and 520°C, forming a film on the substrate. Here, the flow rates of the HCl gas supplied from the halogen-containing source gas supply source 53a, the HCl gas supplied from the reactive gas supply source 54a, and the O gas supplied from the oxygen-containing source gas supply source 55a were maintained at 1 kPa, 1 kPa, and 2.5 kPa, respectively.

[0041] 2-4.Evaluation The crystalline film obtained in 2-3 above was observed with an SEM. The results are shown in Figure 8. A photograph of the obtained crystalline film is shown in Figure 5. The obtained crystalline film was also subjected to SIMS measurement. The measurement results are shown in Table 1. As is clear from Table 1, the content of Si and other elements in the example product was below the detection limit compared to the comparative example product.

[0042] [Table 1]

[0043] (Comparative Example 1) A crystalline film was prepared in the same manner as in Example 1, except that the conditions were as shown in Table 2. The obtained crystalline film was observed by SEM. The results are shown in FIG.

[0044] (Comparative Example 2) A crystalline film was prepared in the same manner as in Example 1, except that the conditions were as shown in Table 2. The obtained crystalline film was observed by SEM. The results are shown in FIG.

[0045] [Table 2] [Industrial Applicability]

[0046] The crystalline film of the present invention can be used in a wide range of fields, including semiconductors (for example, compound semiconductor electronic devices), electronic and electrical equipment components, optical and electrophotographic related devices, and industrial materials, but is particularly useful in semiconductor devices and the like. [Explanation of symbols]

[0047] a period 1. Substrate (crystal substrate) 1a Surface of the substrate 2b Recess 4 Mask Layer 50 Halide Vapor Phase Epitaxy (HVPE) Equipment 51 Reaction chamber 52a Heater 52b Heater 53a Halogen-containing raw gas supply source 53b Metal-containing raw material gas (metal halide gas) supply pipe 54a Reactive gas supply source 54b Reactive gas supply pipe 55a Oxygen-containing raw gas supply source 55b Oxygen-containing raw gas supply pipe 56 PCB holder 57 Metal sources 58 Protective Sheet 59 Gas exhaust section

Claims

1. A crystalline film containing a crystalline metal oxide containing gallium as a main component, further containing a dopant other than Si, wherein the content of Si as a non-dopant is 1×10 １５ cm －３ The C content is 5×10 or less. １６ cm －３ A crystalline film characterized by the following:

2. The crystalline film of claim 1 , wherein the crystalline metal oxide has a corundum structure.

3. 3. The crystal film according to claim 1, wherein the film thickness is 10 μm or more.

4. The crystal film according to any one of claims 1 to 3, having a thickness of 25 µm or more.

5. Surface area is 10 cm ２ The crystal film according to any one of claims 1 to 4, wherein:

6. 6. The crystal film according to claim 1, wherein the crystal film is a semiconductor film.

7. A semiconductor device including a crystalline film, wherein the crystalline film is the crystalline film according to any one of claims 1 to 6.

8. 8. The semiconductor device according to claim 7, which is a power device.

9. 9. A semiconductor system comprising a semiconductor device, wherein the semiconductor device is the semiconductor device according to claim 7.

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