Crystalline laminated structure and semiconductor device

Abstract

To provide a crystalline laminated structure including a high quality crystal layer, and a semiconductor device including such a crystalline laminated structure.SOLUTION: A crystalline laminated structure is obtained by laminating a second crystal layer including a second crystal on a first crystal layer including a first crystal is applied to a semiconductor device. The first crystal includes a κ-Ga2O3 polycrystal, and the second crystal is a crystalline oxide single crystal.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a crystalline layered structure and a semiconductor device that are useful for the manufacture of semiconductor devices. [Background technology]

[0002] As a next-generation switching element that can achieve high voltage resistance, low loss, and high heat resistance, semiconductor devices using gallium oxide (Ga2O3), which has a large band gap, are attracting attention, and it is expected that they will be applied to power semiconductor devices such as inverters. In addition, due to their wide band gap, a wide range of applications are expected as light receiving and emitting devices such as LEDs and sensors. In particular, α-Ga2O3, which has a corundum structure among gallium oxides, can control the band gap by mixing indium and aluminum, either individually or in combination, and constitutes an extremely attractive material system as an InAlGaO-based semiconductor. Here, InAlGaO-based semiconductors are 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 being in the same material family that contains gallium oxide.

[0003] However, since the most stable phase of gallium oxide is the β-gallium structure, it is difficult to form a crystalline film with a corundum structure, which is a metastable phase, unless a special film formation method is used. In addition, α-Ga2O3, which has a corundum structure, is a metastable phase, and bulk substrates grown from a melt cannot be used. Therefore, sapphire, which has the same crystal structure as α-Ga2O3, is currently used as a substrate. However, since there is a large lattice mismatch between α-Ga2O3 and sapphire, the dislocation density of α-Ga2O3 crystalline films grown heteroepitaxially on sapphire substrates tends to be high. In addition to the corundum structure crystalline film, there are still many challenges to be overcome, such as improving the film formation rate and crystal quality, suppressing cracks and abnormal growth, suppressing twins, and cracking of the substrate due to warping. Under these circumstances, several studies are currently being conducted on the formation 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 laminated on a base substrate having a corundum crystal structure. In addition, as in Patent Documents 5 to 7, film formation by mist CVD using an ELO substrate or void formation is also being considered. However, none of these methods are yet satisfactory in terms of achieving both crystal quality and large area, and a crystal film with a large area and excellent crystal quality 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 raw material and an oxygen raw material. Non-Patent Document 1 describes the formation of a gallium oxide film on an ELO substrate by HVPE. However, since α-Ga2O3 is a metastable phase, it is difficult to form a film like β-Ga2O3, and in particular, it is difficult to form a thick film with low dislocation density, and there are still many problems to be solved industrially. Patent Documents 1 to 8 are all publications related to patents or patent applications filed 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] JP 2014-72533 A [Patent Document 5] JP 2016-100592 A [Patent Document 6] JP 2016-98166 A [Patent Document 7] JP 2016-100593 A [Patent Document 8] JP 2016-155714 A [Patent Document 9] International Publication No. 2014 / 050793 [Non-patent literature]

[0006] [Non-Patent Document 1] Oshima, Y., et al. "Epitaxial lateral overgrowth of α-Ga2O3 by halide vapor phase epitaxy." APL Materials 7.2 (2019): 022503. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a crystalline laminated structure having a high-quality crystal layer, and a semiconductor device having such a crystalline laminated structure. [Means for solving the problem]

[0008] As a result of intensive research into achieving the above-mentioned object, the inventors have discovered that when manufacturing a crystalline laminated structure in which a second crystal layer containing a second crystal is laminated on a first crystal layer containing a first crystal, if a polycrystal of κ-Ga2O3 is formed as the first crystal and a single crystal of a crystalline oxide is formed as the second crystal, the quality of the second crystal layer in the obtained crystalline laminated structure, such as the crystallinity, will be excellent, and they have found that such a crystalline laminated structure can solve the above-mentioned conventional problems in one fell swoop.

[0009] After obtaining the above findings, the inventors conducted further studies and completed the present invention.

[0010] That is, the present invention relates to the following inventions. [1] A crystalline layered structure in which a second crystal layer containing a second crystal is layered on a first crystal layer containing a first crystal, the first crystal comprising a polycrystal of κ-Ga2O3, and the second crystal being a single crystal of a crystalline oxide. [2] The crystalline layered structure according to [1], wherein the first crystal layer is formed on a mask layer. [3] The dislocation density of the second crystal layer is 1×10 7 / cm 2 The crystalline layered structure according to the above [1] or [2], [4] The crystalline layered structure according to any one of [1] to [3] above, wherein the crystalline oxide contains at least one metal selected from aluminum, indium and gallium. [5] The crystalline layered structure according to any one of [1] to [4], wherein the crystalline oxide contains at least gallium. [6] The crystalline layered structure according to any one of [1] to [5], wherein the crystalline oxide has a corundum structure. [7] A crystalline layered structure in which a second crystal layer containing a second crystal is layered on a crystal substrate via a first crystal layer containing a first crystal, wherein the first crystal comprises a polycrystal of κ-Ga2O3, and the second crystal is a single crystal of a crystalline oxide. [8] The crystalline layered structure according to [7], wherein the first crystalline layer is layered on the crystalline substrate via a mask layer. [9] A semiconductor device using the crystalline layered structure according to any one of [1] to [8] above.

[10] A semiconductor system including a semiconductor device, the semiconductor device being the semiconductor device described in [9] above. Effect of the Invention

[0011] The crystalline layered structure of the present invention comprises a high-quality crystal layer. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a halide vapor phase epitaxy (HVPE) apparatus preferably used in the present invention. [Diagram 2] FIG. 2 is a diagram showing a schematic view of the surface of a concave-convex portion formed on the surface of a substrate preferably used in the present invention. [Diagram 3] FIG. 2 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] FIG. 2 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. [Diagram 5] 1 shows SEM observation results in an example, where (a) and (b) show a bird's-eye view and a cross-sectional view after 40 minutes, (c) and (d) show a bird's-eye view and a cross-sectional view after 2 hours, and (e) and (f) show a bird's-eye view and a cross-sectional view after 5 hours. [Figure 6]1 shows photographs and SEM observation results in an example and a comparative example, where (a) is an SEM bird's-eye view of the comparative example, (b) is an external photograph of the comparative example, (c) is an SEM bird's-eye view of the example, and (d) is an external photograph of the example. [Figure 7] FIG. 1 is a diagram illustrating a preferred example of a power supply system. [Figure 8] FIG. 1 is a diagram illustrating a preferred example of a system device. [Figure 9] FIG. 1 is a diagram illustrating a preferred example of a power supply circuit diagram of a power supply device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The crystalline laminated structure of the present invention is a crystalline laminated structure in which a second crystal layer containing a second crystal is laminated on a first crystal layer containing a first crystal, and the first crystal contains a polycrystal of κ-Ga2O3, and the second crystal is a single crystal of a crystalline oxide. In the present invention, it is preferable that the second crystal layer is laminated so that at least a part of the second crystal layer is in contact with the first crystal layer. Here, the term "single crystal" refers to a crystal consisting of a single crystallite whose crystal plane and crystal axis are aligned. In addition, the term "polycrystal" refers to a crystal formed by joining or accumulating two or more crystallites having different crystal planes and crystal axes via grain boundaries.

[0014] (First crystal layer) The first crystal layer includes a first crystal. The first crystal is not particularly limited as long as it includes a polycrystal of κ-Ga2O3. In the present invention, it is preferable that the first crystal layer includes the polycrystal as a main component. Here, the "main component" means, for example, when the first crystal layer includes Ga2O3 as a main component, that Ga2O3 is included at a ratio of 0.5 or more of gallium in the metal elements in the first crystal layer. In the present invention, it is preferable that the atomic ratio of gallium in the metal elements in the first crystal layer is 0.7 or more, and more preferably 0.8 or more. The thickness of the first crystal layer is not particularly limited, and may be 1 μm or more, or may be 1 μm or less. In the present invention, the first crystal layer may include an amorphous portion.

[0015] (Second crystal layer) The second crystal is not particularly limited as long as it is a single crystal of a crystalline oxide. It is preferable that the second crystal layer contains the second crystal as a main component. In the present invention, the crystalline oxide may be a semiconductor. Examples of the crystalline oxide include a crystal of a metal oxide containing one or more metals selected from aluminum, gallium, indium, iron, chromium, vanadium, titanium, rhodium, nickel, cobalt, and iridium. In the present invention, the crystalline oxide preferably contains at least one metal selected from aluminum, indium, and gallium, more preferably contains at least gallium, and most preferably is crystalline gallium oxide or a mixed crystal thereof. The crystal structure of the crystalline oxide is not particularly limited as long as it does not impede the object of the present invention. Examples of the crystal structure of the crystalline oxide include a corundum structure, a β-gallia structure, a hexagonal structure (e.g., an ε-type structure, etc.), an orthorhombic structure (e.g., a κ-type structure, etc.), a cubic structure, or a tetragonal structure. In the present invention, the crystalline oxide preferably has a corundum structure, a β-gallia structure, or a hexagonal crystal (e.g., an ε-type structure, etc.), and more preferably has a corundum structure. By combining such a preferred second crystal layer with the above-mentioned preferred first crystal layer, the quality of the second crystal layer, such as crystallinity, can be improved. The term "main component" means that the second crystal is preferably contained in an atomic ratio of 50% or more, more preferably 70% or more, and even more preferably 90% or more of the total components of the second crystal layer, and may be 100%. The thickness of the second crystal layer is not particularly limited, but is preferably 10 μm or more, more preferably 30 μm or more, and most preferably 50 μm or more. In the present invention, the second crystal layer preferably includes a laterally grown portion. The laterally grown portion is not particularly limited as long as it is a portion that has grown laterally or approximately laterally with respect to the thickness direction of the second crystal layer.Furthermore, in the present invention, when the first crystal layer contains a single crystal, it is preferable that the crystal structure of the crystalline oxide is the same as the crystal structure of the single crystal in the first crystal layer, since this can improve the quality of the laterally grown portion of the second crystal layer, and it is even more preferable that the constituent material of the crystalline oxide is the same as the constituent material of the single crystal in the first crystal layer.

[0016] The second crystal layer may contain a dopant. The dopant is not particularly limited and may be a known one, and may be 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 is 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 % in the second crystal layer.

[0017] The crystalline laminated structure can be preferably obtained, for example, by forming a first crystal layer containing polycrystals of κ-Ga2O3 on the crystal substrate in a method for manufacturing the crystalline laminated structure by forming a first crystal layer and a second crystal layer on the crystal substrate, and further forming a second crystal layer containing a single crystal of a crystalline oxide on the first crystal layer. The formation of the first crystal layer and the second crystal layer can be performed by using a known means.

[0018] (Crystal Substrate) The crystal substrate is not particularly limited as long as it is a substrate containing a crystalline substance as a main component, and may be a 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 crystal substrate include a substrate containing a crystalline substance having a corundum structure as a main component, a substrate containing a crystalline substance having a β-gallium structure as a main component, and a substrate containing a crystalline substance having a hexagonal structure as a main component. The "main component" refers to a substrate containing the crystalline substance in a composition ratio of 50% or more, preferably 70% or more, and more preferably 90% or more.

[0019] Examples of the substrate containing a crystal having a corundum structure as a main component include a sapphire substrate and an α-type gallium oxide substrate. Examples of the substrate containing a crystal having a β-gallium structure as a main component include a β-Ga2O3 substrate, or a mixed crystal substrate containing β-Ga2O3 and Al2O3. A suitable example of the mixed crystal substrate containing β-Ga2O3 and Al2O3 is a mixed crystal substrate containing Al2O3 in an atomic ratio of more than 0% and 60% or less. Examples of the substrate having a hexagonal crystal structure include a SiC substrate, a ZnO substrate, and a GaN substrate. Examples of other crystal substrates include a Si substrate.

[0020] 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-angle. The off-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.

[0021] In the present invention, it is preferable to form an uneven portion consisting of recesses or protrusions on the crystal substrate directly or via another layer, and form a first crystal layer on the uneven portion, since this allows the crystalline laminated structure to be obtained more efficiently. 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 an uneven portion consisting of protrusions. The uneven portion may be formed of regular recesses or protrusions, or may be formed of irregular recesses or protrusions. In the present invention, it is preferable that the uneven portion is formed periodically, and it is more preferable that the uneven portion is patterned periodically and regularly. The shape of the uneven portion is not particularly limited, and examples include stripes, dots, meshes, and random shapes, but in the present invention, dots or stripes are preferable. In addition, 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 (for example, a square, a rectangle, or a trapezoid), a pentagon, or a hexagon, a circle, an ellipse, or the like. When the unevenness 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 parts of the unevenness is not particularly limited, and examples thereof include a U-shape, an inverted U-shape, a wave shape, or a polygonal shape such as a triangle, a quadrangle (for example, a square, a rectangle, or a trapezoid), a pentagon, or a hexagon.

[0022] The material of the convex portion 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 the material of the convex portion include oxides, nitrides, or carbides of Si, Ge, Ti, Zr, Hf, Ta, Sn, etc., carbon, diamond, metals, and mixtures thereof. More specifically, examples of the material 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). In the present invention, the material of the convex portion preferably contains a metal oxide of a metal of Group 4 of the periodic table (e.g., Ti, Zr, Hf, etc.) because the first layer can be formed more efficiently, and more preferably contains a metal oxide of Ti. The content of the constituent material in the convex portion is preferably 50% or more, more preferably 70% or more, and most preferably 90% or more, in terms of composition ratio.

[0023] The means for forming the convex portions may be known means, and examples thereof include known patterning processing 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-shaped 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 a known pattern shape. Examples of the pattern shape include a cone shape, a bell shape, a dome shape, a hemisphere shape, a square or a triangular pyramid shape, and the like. In the present invention, the pattern shape is preferably a cone shape. 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 portion is preferably performed by forming a mask layer on the crystal substrate. The mask layer can be suitably formed by forming a film of a constituent material of the mask layer by a known film forming means such as a vacuum deposition method, a CVD method, or a sputtering method, and then processing it by the above-mentioned known pattern processing means. Examples of the constituent material of the mask layer include the materials exemplified as the constituent material of the convex portion. In the present invention, when a crystalline laminated structure is manufactured using the mask layer, it is preferable to form a first crystal layer on the mask layer, and it is more preferable to form the first crystal layer on the mask layer having a thickness of 100 nm or less, since a thicker second crystal layer with reduced dislocations can be obtained, and it is more preferable to form the first crystal layer on the mask layer having a thickness of 50 nm or less, since a dislocation density of the second crystal layer can be reduced to 1×10 7 / cm 2 The dislocations are edge dislocations, screw dislocations, or a mixture of these. In this case, the material constituting the mask layer preferably contains a metal oxide of a transition metal, more preferably contains a metal oxide of a metal in Group 4 of the periodic table, and most preferably contains titanium oxide. By using such a preferable material for the mask layer, polycrystals of κ-Ga2O3 can be formed more easily, and the crystallinity of the second crystal layer can be improved.

[0024] The recess is not particularly limited, but may be the same as the constituent material of the protrusion, or may be a substrate. In the present invention, it is preferable that the recess is a void layer provided on the surface of the substrate. The means for forming the recess can be the same as the means for forming the protrusion. The void layer can be formed on the surface of the substrate by providing a groove 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 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.

[0025] Hereinafter, preferred embodiments of the crystal substrate suitably used in the present invention will be described with reference to the drawings. FIG. 2 shows one embodiment of the uneven portion provided on the crystal growth surface of the crystal substrate in the present invention. The uneven portion in FIG. 2 is composed of a crystal substrate 1 and a mask layer 4. FIG. 3 shows the surface of the uneven portion shown in FIG. 2 as viewed from the zenith direction. As can be seen from FIG. 2 and FIG. 3, the mask layer 4 is formed on the crystal growth surface of the crystal substrate 1, and has holes in the form of dots. The crystal substrate 1 is exposed from the dot holes in the mask layer 4, and dot-shaped recesses 2b are formed in a triangular lattice shape. The dot circles are provided at intervals of a certain period a. The period a is not particularly limited, but is preferably 1 μm to 1 mm, and more preferably 5 μm to 300 μm in the present invention. Here, the period a refers to the distance between the ends of the adjacent dot circles. The mask layer 4 can be formed by forming a film of the constituent material of the mask layer 4, and then processing it into a predetermined shape using a known means such as photolithography. In addition, examples of the constituent material of the mask layer 4 include oxides, nitrides or carbides of Si, Ge, Ti, Zr, Hf, Ta, Sn, Al, carbon, diamond, metal, or mixtures thereof. In the present invention, the mask layer 4 preferably contains a metal oxide of a transition metal, more preferably contains a metal oxide of a metal of group 4 of the periodic table, and most preferably contains titanium oxide. By using such a preferable constituent material of the mask layer, polycrystals of κ-Ga2O3 can be more easily formed, and the crystallinity of the second crystal layer can be more excellent. In addition, the film formation means of the mask layer 4 is not particularly limited and may be a known means. Examples of the film formation means of the constituent material of the mask layer 4 include vacuum deposition, CVD, and sputtering. In the present invention, when the mask layer contains titanium oxide, it is preferable to use a sputtering method, and it is more preferable to use a reactive sputtering method, since polycrystals can be more suitably formed on the mask layer 4.

[0026] FIG. 4 shows one embodiment of the uneven portion provided on the crystal growth surface of the 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 stripe shape on the crystal growth surface of the crystal substrate 1, and the mask layer 4 forms the recesses (grooves) 2b in a stripe shape. The mask layer 4 can be formed by a known method such as photolithography. Examples of the material constituting the mask layer 4 include oxides, nitrides or carbides of Si, Ge, Ti, Zr, Hf, Ta, Sn, Al, carbon, diamond, metals, or mixtures thereof. In the present invention, the mask layer 4 preferably contains a metal oxide of a transition metal, more preferably contains a metal oxide of a metal in Group 4 of the periodic table, and most preferably contains titanium oxide. By using such a preferable material for the mask layer, polycrystals of κ-Ga2O3 can be formed more easily, and the crystallinity of the second crystal layer can be improved. The width and height of the convex portions (mask layer) of the uneven portion, the width and depth of the concave portions, the intervals, etc. 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 recess 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 uneven portion have these preferable depths, a better crystalline laminated structure can be obtained more easily. The uneven portion may be formed directly on the crystal substrate, or may be provided via another layer.

[0027] In the present invention, a buffer layer including a stress relaxation layer or the like may be provided on the crystal substrate, and when a buffer layer is provided, the uneven portion may also be formed on the buffer layer. In addition, in the present invention, it is preferable that the substrate has a buffer layer on a part or the whole of the surface. The means for forming the buffer layer is not particularly limited and may be a known means. Examples of the forming means include a spray method, a mist CVD method, a HVPE method, a MBE method, a MOCVD method, and a sputtering method. In the present invention, it is preferable that the buffer layer is formed by a mist CVD method, since the quality of the crystal film formed on the buffer layer can be improved, and in particular, crystal defects such as tilt can be suppressed.

[0028] The means for forming the first crystal layer and the second crystal layer are not particularly limited and may be known means. Examples of the forming means include CVD, MOCVD, MOVPE, mist CVD, mist epitaxy, MBE, HVPE, pulse growth, ALD, and sputtering. In the present invention, the forming means is preferably mist CVD, mist epitaxy, or HVPE, and more preferably HVPE. In the present invention, it is preferable that the forming means for the first crystal layer and the second crystal layer are the same, since the first crystal layer and the second crystal layer can be formed continuously and efficiently.

[0029] The present invention will be described in more detail below by taking as an example the case where the HVPE method is used as a means for forming the first crystal layer or the second crystal layer (hereinafter, collectively referred to as "crystal layer"). Specifically, the HVPE method is, for example, a metal source containing a metal is gasified to form a metal halide gas, and then, when the metal halide gas and an oxygen-containing source gas are supplied to the crystal substrate in a reaction chamber to form a film, it is preferable that a reactive gas is supplied onto the crystal substrate and the film is formed under the flow of the reactive gas.

[0030] (metal source) The metal source is not particularly limited as long as it contains a metal and can be gasified, and may be a metal element or a metal compound. Examples of the metal include one or more metals selected from gallium, aluminum, indium, iron, chromium, vanadium, titanium, rhodium, nickel, cobalt, and iridium. In the present invention, the metal is preferably one or more metals selected from gallium, aluminum, and indium, more preferably gallium, and the metal source is most preferably gallium element. The metal source may be gas, liquid, or solid, but in the present invention, for example, when gallium is used as the metal, the metal source is preferably liquid.

[0031] The gasification means is not particularly limited and may be a known means as long as it does not impede the object of the present invention. In the present invention, the gasification means is preferably carried out by halogenating the metal source. The halogenating agent used for the halogenation is not particularly limited and may be a known halogenating agent as long as it can halogenate the metal source. 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 more preferably 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 form a metal halide. 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 less, more preferably 700°C or less, and most preferably 400°C to 700°C. The metal halide gas is not particularly limited as long as it is a gas containing a halide of the metal source. Examples of the metal halide gas include halides of the metal (fluorides, chlorides, bromides, iodides, etc.).

[0032] In the present invention, a metal source containing a metal is gasified to form a metal halide gas, and then the metal halide gas and the oxygen-containing source gas are supplied onto the substrate in the reaction chamber. In addition, in the present invention, a reactive gas is supplied onto the substrate. The temperature for forming the crystal layer 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 less, more preferably 700°C or less, and most preferably 400°C to 700°C. In addition, in the present invention, it is also preferable to form the first crystal layer at a low temperature (for example, less than 500°C) and the second crystal layer at a high temperature (for example, 500°C or more), since the first crystal layer and the second crystal layer can be more favorably formed separately. The oxygen-containing source gas is, for example, one or more gases selected from O2 gas, CO2 gas, NO gas, NO2 gas, N2O gas, H2O gas, and O3 gas. In the present invention, the oxygen-containing source gas is preferably one or more gases selected from the group consisting of O2, H2O, and N2O, and more preferably contains O2. The reactive gas is usually a gas having a different reactivity from the metal halide gas and the oxygen-containing source gas, and does not contain an inert gas. The reactive gas is not particularly limited, but may be, for example, an etching gas. The etching gas is not particularly limited as long as it does not impede the object of the present invention, and may be a known etching gas. In the present invention, the reactive gas is preferably a halogen gas (for example, fluorine gas, chlorine gas, bromine gas, or iodine gas), a hydrogen halide gas (for example, 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, and preferably contains a hydrogen halide gas, and most preferably contains hydrogen chloride. The metal halide gas, the oxygen-containing source gas, and the reactive gas may contain a carrier gas. The carrier gas may be, for example, an inert gas such as nitrogen or argon. Further, the partial pressure of the metal halide gas is not particularly limited, but in the present invention, it is preferably 0.5 Pa to 1 kPa, and more preferably 5 Pa to 0.5 kPa.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.

[0033] 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 the dopant-containing source gas in this way, 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.), and 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 It is preferable that 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.

[0034] The crystalline laminated structure of the present invention can be particularly suitably used in semiconductor devices, and is particularly useful in power devices. Examples of semiconductor devices formed using the crystalline laminated structure include transistors and TFTs such as MIS, HEMT, and MOS, Schottky barrier diodes using semiconductor-metal junctions, PN or PIN diodes combined with other P layers, and light-emitting and receiving devices. In the present invention, the crystalline laminated structure may be used as is in a semiconductor device or the like, or may be applied to a semiconductor device or the like by peeling off the crystal substrate and / or the first crystal layer and the second crystal layer or the like using known means.

[0035] In addition to the above, the semiconductor device of the present invention can be suitably used as a power module, inverter, or converter by using known means, and these semiconductor devices are also included in the present invention. The semiconductor device of the present invention can also be suitably used in, for example, a semiconductor system using a power supply device. The power supply device can be manufactured from or as the semiconductor device by connecting to a wiring pattern or the like using known means. FIG. 7 shows an example of a power supply system. FIG. 7 shows a power supply system using a plurality of the power supplies and a control circuit. The power supply system can be used in a system device in combination with an electronic circuit as shown in FIG. 8. FIG. 9 shows an example of a power supply circuit diagram of a power supply device. FIG. 9 shows a power supply circuit of a power supply device consisting of a power circuit and a control circuit, in which a DC voltage is switched at high frequency by an inverter (composed of MOSFETs: A to D) to convert it to AC, then insulated and transformed by a transformer, rectified by a rectifier MOSFET (A to B'), smoothed by a DCL (smoothing coils L1, L2) and a capacitor, and a DC voltage is output. At this time, a voltage comparator compares the output voltage with a reference voltage, and a PWM control circuit controls the inverter and rectifier MOSFET so as to obtain a desired output voltage. EXAMPLES

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

[0037] Example 1 1.Mask formation 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 titanium oxide was formed on the substrate by sputtering. The formed mask layer was then processed into a mask of a predetermined shape by photolithography. In the sputtering method, a mask layer made of titanium oxide (thickness 50 nm) was formed using a Ti target while flowing O2 gas. Specifically, the mask layer was processed so that openings (dots) (diameter: 5 μm) were arranged on the substrate in a triangular lattice pattern with a period (distance between the ends of adjacent dots) of 20 μm.

[0038] 2. Formation of the first and second crystal layers 2-1.HVPE Equipment A halide vapor phase epitaxy (HVPE) apparatus 50 used in this embodiment 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 fixed to a substrate holder 56. The reaction chamber 51 further includes an oxygen-containing source gas supply pipe 55b, a reactive gas supply pipe 54b, and a substrate holder 56 for mounting a 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, and forms a flow path for the oxygen-containing source gas 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 fixed to the substrate holder 56. The reactive gas supply pipe 54b is connected to the reactive gas supply source 54a, and forms a flow path for the reactive gas so that the reactive gas can be supplied from the reactive gas supply source 54a through the reactive gas supply pipe 54b to the substrate fixed to the substrate holder 56. The metal-containing source gas supply pipe 53b is connected to the 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 the substrate holder 56. The reaction chamber 51 is provided with a gas exhaust unit 59 for exhausting the used gas, and further, a protective sheet 58 for preventing the precipitation of reactants is provided on the inner wall of the reaction chamber 51.

[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. Deposition of κ-Ga2O3 and α-Ga2O3 films Hydrogen chloride (HCl) gas (purity 99.999% or more) was supplied from the halogen-containing raw material gas supply source 53a to the gallium (Ga) metal 57 arranged inside the metal raw material-containing gas supply pipe 53b. Gallium chloride (GaCl / GaCl3) was generated by a chemical reaction between the Ga metal and the hydrogen chloride (HCl) gas. The obtained gallium chloride (GaCl / GaCl3) and O2 gas (purity 99.99995% or more) supplied from the oxygen-containing raw material gas supply source 55a were supplied onto the substrate through the reactive gas supply pipe 54b. Then, under the flow of HCl gas, the gallium chloride (GaCl / GaCl3) and the O2 gas were reacted on the substrate at atmospheric pressure and 520°C to form a film on the substrate. Here, the partial pressure of the HCl gas supplied from the halogen-containing raw material gas supply source 53a was set to 1.25×10 -1 kPa, and the partial pressure of the HCl gas supplied from the reactive gas supply source 54a is 1.25×10 -1 The partial pressure of the O2 gas supplied from the oxygen-containing raw material gas supply source 55a was maintained at 1.25 kPa.

[0041] 2-4.Evaluation In the above 2-3, the state of crystal growth after 40 minutes, 2 hours, and 5 hours was observed by SEM. The results are shown in Figure 5. The layered structure obtained in the above 2-3 had α-Ga2O3 single crystals formed as a crystalline film on κ-Ga2O3 polycrystals, and the obtained crystalline film had a dislocation density of 5×10 6 / cm 2 The crystal film was clean with no abnormal growth or cracks observed.

[0042] Example 2 A laminated structure was fabricated in the same manner as in Example 1, except that the period of the mask layers was set to 10 μm. The state of crystal growth and a photograph of the appearance of the obtained laminated structure are shown in Figure 6. In the obtained laminated structure, α-Ga2O3 single crystals were formed as a crystalline film on κ-Ga2O3 polycrystals, and the obtained crystalline film had a dislocation density of 5 × 10 6 / cm 2 No abnormal growth or cracks were observed, and the crystal film was clean.

[0043] Comparative Example 1 A laminated structure was fabricated in the same manner as in Example 1, except that SiO2 was used as the mask material. The state of crystal growth and a photograph of the appearance of the obtained laminated structure are shown in Figure 6. The crystal film of the obtained laminated structure had low crystallinity, and abnormal growth was visible to the naked eye. [Industrial Applicability]

[0044] The crystalline layered structure and semiconductor device of the present invention can be used in a wide range of fields, including semiconductors (e.g., compound semiconductor electronic devices), electronic components, electrical equipment components, optical and electrophotographic related devices, and industrial materials, but are particularly useful in the manufacture of semiconductor devices. [Explanation of symbols]

[0045] a period 1. Substrate (crystal substrate) 1a Surface of the board 2b Recess (groove) 4 Mask Layer 50 Halide Vapor Phase Epitaxy (HVPE) Equipment 51 Reaction chamber 52a Heater 52b Heater 53a Halogen-containing source gas supply source 53b Metal-containing source 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 laminated structure in which a second crystal layer including a second crystal is laminated on a first crystal layer including a first crystal, the first crystal being formed on a mask layer including titanium oxide and a κ-Ga ２ O ３ The second crystal is a single crystal of crystalline gallium oxide having a corundum structure, and the dislocation density of the second crystal layer is 1×10 ７ / cm ２ A crystalline laminated structure characterized by:

2. A crystalline laminated structure in which a second crystal layer including a second crystal is laminated on a crystal substrate via a first crystal layer including a first crystal, the first crystal being laminated on the crystal substrate via a mask layer including titanium oxide, and a κ-Ga ２ O ３ The second crystal is a single crystal of crystalline gallium oxide having a corundum structure, and the dislocation density of the second crystal layer is 1×10 ７ / cm ２ A crystalline laminated structure characterized by:

3. A semiconductor device comprising the crystalline laminated structure according to claim 1 or 2.

4. 4. A semiconductor system comprising a semiconductor device, the semiconductor device being the semiconductor device according to claim 3.

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