JP6478020B2 - SUBSTRATE FOR CRYSTAL GROWING, CRYSTALLINE LAMINATED STRUCTURE, METHOD FOR PRODUCING THEM, AND EPITAXIAL GROWTH METHOD - Google Patents

Description

  The present invention relates to a crystal growth substrate, a crystalline multilayer structure, a manufacturing method thereof, and an epitaxial growth method useful for manufacturing a semiconductor device.

  Conventionally, there is a problem that cracks and lattice defects occur when crystals are grown on different substrates. In order to solve this problem, matching the lattice constant and the thermal expansion coefficient of the substrate and the film has been studied. In addition, when mismatching occurs, a film forming method such as ELO has been studied.

  Patent Document 1 describes a method in which a buffer layer is formed on a different substrate, and a zinc oxide based semiconductor layer is crystal-grown on the buffer layer. Patent Document 2 describes that a nanodot mask is formed on a heterogeneous substrate, and then a single crystal semiconductor material layer is formed. Non-Patent Document 1 describes a technique for crystal growth of GaN on sapphire via a GaN nanocolumn. Non-Patent Document 2 describes a method of reducing defects such as pits by growing GaN on Si (111) using a periodic SiN intermediate layer.

  However, in any technique, the film formation speed is bad, cracks, dislocations, warpage, etc. occur in the substrate, or dislocations, cracks, etc. occur in the epitaxial film, and a high quality epitaxial film can be obtained. This is difficult, and there has been a problem in increasing the diameter of the substrate and increasing the thickness of the epitaxial film.

JP 2010-232623 A Special table 2010-516599 gazette

Kazuhide Kusakabe., Et al., “Overgrowth of GaN layer on GaN nano-columns by RF-molecular beam epitaxy”, Journal of Crystal Growth 237-239 (2002) 988-992 K. Y. Zang., Et al., “Defect reduction by periodic SiNx containings in gallium nitride grown on Si (111)”, Journal of Applied Physics 101, 093502 (2007)

  An object of the present invention is to provide a crystal growth substrate and an epitaxial growth method capable of forming an epitaxial layer industrially advantageously even on different types of substrates.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have a concavo-convex portion formed of a convex portion or a concave portion on a crystal growth substrate that is perpendicular to the crystal axis direction where the thermal expansion coefficient of the crystal substrate is high. Surprisingly, it has been found that the growth rate of epitaxial growth is dramatically improved when formed in the direction, and it has been found that the conventional problems described above can be solved at once.

  In addition, after obtaining the above knowledge, the present inventors have further studied and completed the present invention.

That is, the present invention relates to the following inventions.
[1] A crystal growth substrate in which a concavo-convex portion including a convex portion or a concave portion is formed on a crystal growth surface of a crystal substrate directly or via another layer, wherein the crystal substrate has a crystal growth direction. First and second crystal axes perpendicular to or substantially perpendicular to the first crystal axis, the thermal expansion coefficient in the first crystal axis direction being larger than the thermal expansion coefficient in the second crystal axis direction, A substrate for crystal growth, wherein the concavo-convex portion is formed in part or all in a direction perpendicular or substantially perpendicular to the first crystal axis.
[2] The crystal growth substrate according to [1], wherein the uneven portions are periodically formed.
[3] The crystal growth substrate according to [1] or [2], wherein the uneven portion is in a stripe shape, a dot shape, a mesh shape, or a random shape.
[4] The crystal growth substrate according to any one of [1] to [3], wherein the concave portion is a void layer provided on the crystal growth surface of the crystal substrate.
[5] The thermal expansion coefficient difference in the first and second crystal axis directions is 0.5 × 10 ⁻⁶ K ⁻¹ or more at the crystal growth temperature, and any one of [1] to [4] Substrate for crystal growth.
[6] A crystalline stacked structure, wherein an epitaxial film is formed on the crystal growth surface of the crystal growth substrate according to any one of [1] to [5].
[7] The crystalline laminated structure according to [6], wherein the epitaxial film has a corundum structure.
[8] The crystalline multilayer structure according to [6] or [7], wherein the epitaxial film includes an oxide semiconductor as a main component.
[9] The crystalline multilayer structure according to [8], wherein the oxide semiconductor contains at least gallium.
[10] The crystalline multilayer structure according to any one of [1] to [9], wherein the crystal substrate is a sapphire substrate.
[11] A method for producing a crystal growth substrate in which a concavo-convex portion consisting of a convex portion or a concave portion is formed on a crystal growth surface of a crystal substrate directly or via another layer,
The formation of the concavo-convex portion has first and second crystal axes perpendicular or substantially perpendicular to the crystal growth direction, and the thermal expansion coefficient in the first crystal axis direction is the second crystal axis direction. In the crystal growth substrate, the concavo-convex portion is formed in a part of or all of the crystal growth surface of the crystal substrate having a thermal expansion coefficient larger than the first crystal axis in a direction perpendicular or substantially perpendicular to the first crystal axis. Production method.
[12] A crystal growth substrate is manufactured by forming an uneven portion including a convex portion or a concave portion on the crystal growth surface of the crystal substrate directly or via another layer, and then an epitaxial film is formed. A method for producing a crystalline laminated structure, comprising:
The formation of the concavo-convex portion has first and second crystal axes perpendicular or substantially perpendicular to the crystal growth direction, and the thermal expansion coefficient in the first crystal axis direction is the second crystal axis direction. A manufacturing method characterized by forming the concavo-convex portion in a direction perpendicular or substantially perpendicular to the first crystal axis on part or all of a crystal growth surface of a crystal substrate having a thermal expansion coefficient larger than that. .
[13] An epitaxial growth method using the crystal growth substrate according to any one of [1] to [5].
[14] A semiconductor device comprising the crystalline multilayer structure according to any one of [6] to [10].

  According to the present invention, the deposition rate of epitaxial crystal growth is improved, and an epitaxial layer can be formed industrially advantageously.

1 schematically shows a crystal substrate used in the present invention. It is a schematic diagram which shows the suitable one aspect | mode of the board | substrate for crystal growth in this invention. It is a schematic diagram which shows another suitable one aspect | mode of the board | substrate for crystal growth in this invention. It is a schematic diagram which shows another suitable one aspect | mode of the board | substrate for crystal growth in this invention. It is a schematic diagram which shows another suitable one aspect | mode of the board | substrate for crystal growth in this invention. It is a block diagram of the mist epitaxy apparatus used in the Example. The cross-sectional image by the optical microscope in an Example is shown. The cross-sectional image by the optical microscope in a comparative example is shown.

  The crystal growth substrate of the present invention is a crystal growth substrate in which a concavo-convex portion including a convex portion or a concave portion is formed on a crystal growth surface of the crystal substrate, and the crystal substrate is perpendicular or substantially perpendicular to the crystal growth direction. The first and second crystal axes are perpendicular to each other, and the thermal expansion coefficient in the first crystal axis direction is larger than the thermal expansion coefficient in the second crystal axis direction, and part or all of the crystal growth surface Further, the uneven portion is formed in a direction perpendicular or substantially perpendicular to the first crystal axis.

<Crystal growth substrate>
The “crystal growth substrate” is capable of supporting an epitaxial film, and at least a part or all of the crystal growth surface has a protrusion or a recess in a direction perpendicular or substantially perpendicular to the first crystal axis. If the uneven | corrugated | grooved part which consists of is formed, it will not specifically limit. The “crystal growth surface” is a main surface of the crystal growth substrate and refers to a surface on which an epitaxial film is formed.

<Crystal substrate>
The crystal substrate has first and second crystal axes perpendicular or substantially perpendicular to the crystal growth direction, and the thermal expansion coefficient in the first crystal axis direction is the thermal expansion coefficient in the second crystal axis direction. If it is larger than, it will not specifically limit. The substrate may be a known substrate, an insulator substrate, a conductive substrate, or a semiconductor substrate. “Crystal growth direction” refers to a vector direction in which the distance from the reference point to the surface of the epitaxial film is the shortest when a specific point on the surface of the crystal substrate is used as a reference point. Examples of the crystal substrate include a substrate containing a crystalline material having a corundum structure as a main component, a substrate containing a crystal material having a β-gallia structure as a main component, and a substrate having a hexagonal crystal structure. The “main component” means a composition ratio in the substrate that includes 50% or more of the crystalline material, preferably 70% or more, and more preferably 90% or more.

Examples of the substrate containing the crystalline material having the 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-gallia structure as a main component include a β-Ga ₂ O ₃ substrate or a mixed crystal substrate containing β-Ga ₂ O ₃ and Al ₂ O _3. . In addition, as a mixed crystal substrate containing β-Ga ₂ O ₃ and Al ₂ O ₃ , for example, a mixed crystal substrate in which Al ₂ O ₃ is more than 0 wt% and not more than 60 wt% can be cited as a suitable example. . Examples of the substrate having the hexagonal crystal structure include a SiC substrate, a ZnO substrate, and a GaN substrate. Examples of other crystal substrates include, for example, Si substrates. In the present invention, the crystal substrate is preferably a sapphire substrate. The sapphire substrate may have an off angle. The off angle is not particularly limited, but is preferably 0 ° to 15 °.

  The crystal substrate has first and second crystal axes that are perpendicular or substantially perpendicular to the crystal growth direction. Here, “vertical or substantially perpendicular” is preferably within a range of about ± 20 degrees, more preferably within a range of about ± 10 degrees, and most preferably with respect to an axis perpendicular to the crystal growth direction. Is in the range of about ± 5 degrees.

FIG. 1 schematically shows a crystal substrate used in the present invention. The crystal substrate of FIG. 1 has at least a crystal growth surface 1 and crystal axes different from each other in the X, Y, and Z axes, and the arrow direction of the Y axis is the crystal growth direction. Further, the thermal expansion coefficient in the X-axis direction is larger than the thermal expansion coefficient in the Z-axis direction. Therefore, the X axis is the first crystal axis, and the Z axis is the second crystal axis. The thermal expansion coefficient in the first crystal axis direction is not particularly limited as long as it is larger than the thermal expansion coefficient in the second crystal axis direction. In the present invention, the difference in thermal expansion coefficient between the first crystal axis and the second crystal axis is preferably 0.5 × 10 ⁻⁶ K ⁻¹ or more, and 0.8 × 10 ⁻⁶ K ^{−. It} is more preferably ¹ or more, and most preferably 1.0 × 10 ⁻⁶ K ⁻¹ or more.

  The thickness of the crystal substrate is not particularly limited, but is preferably 50 to 2000 μm, more preferably 200 to 800 μm.

<Uneven portion>
The concavo-convex portion is not particularly limited as long as it is composed of a convex portion or a concave portion, and may be a concavo-convex portion composed of a convex portion, a concavo-convex portion composed of a concave portion, or a convex portion and a concave portion. The uneven | corrugated | grooved part which consists of may be sufficient. Moreover, the said uneven | corrugated | grooved part may be formed from the regular convex part or a recessed part, and may be formed from the irregular convex part or recessed part. In the present invention, it is preferable that the plurality of uneven portions be formed periodically. The shape of the concavo-convex portion is not particularly limited and may be a stripe shape, a dot shape, a mesh shape or a random shape. In the present invention, a stripe shape or a dot shape is preferable. Examples of the surface shape of the dot include a triangle, a quadrangle (for example, a square, a rectangle, or a trapezoid), a polygon such as a pentagon or a hexagon, a circle, and an ellipse. The shape of the concave portion or convex portion of the concavo-convex portion is not particularly limited. For example, a U-shape, U-shape, inverted U-shape, wave shape, triangle, quadrangle (eg, square, rectangle, trapezoid, etc.) And polygons such as pentagons and hexagons.

  The constituent material of the convex portion is not particularly limited and may be a known material. An insulator material, a conductor material, or a semiconductor material may be used, but a material capable of inhibiting crystal growth in the vertical direction is preferable. The constituent material may be amorphous, single crystal, or polycrystalline. Examples of the constituent material of the convex portion include oxides such as Si, Ge, Ti, Zr, Hf, Ta, and Sn, nitrides or carbides, carbine, diamond, metal, and mixtures thereof. More specifically, a Si-containing compound containing SiO2, SiN or polycrystalline silicon as a main component, a metal having a melting point higher than the crystal growth temperature of the crystalline semiconductor (for example, platinum, gold, silver, palladium, rhodium, Noble metals such as iridium and ruthenium). The content of the constituent material is preferably 50% or more, more preferably 70% or more, and most preferably 90% or more in terms of the composition ratio in the convex portion.

  As the means for forming the convex portions, known means may be used, for example, known patterning means such as photolithography, electron beam lithography, laser patterning, and subsequent etching (for example, dry etching or wet etching). Can be mentioned. In the present invention, the convex portion is preferably in a stripe shape or a dot shape, and more preferably in a stripe shape.

  Although the said recessed part is not specifically limited, The same thing as the constituent material of the said convex part may be sufficient, and a crystal substrate may be sufficient. In this invention, it is preferable that the said recessed part is dot shape, and it is more preferable that the dot-shaped recessed part is provided in the mask layer which consists of the said silicon containing compound. As the means for forming the concave portion, the same means as the means for forming the convex portion can be used. It is also preferable that the recess is a void layer provided on the crystal growth surface of the crystal substrate. The void layer can be formed on the crystal growth surface of the crystal substrate by providing a groove in the crystal substrate by a known groove processing means. The groove width, groove depth, terrace width, and the like of the void layer are not particularly limited as long as the object of the present invention is not impaired, and can be appropriately set. Further, the void layer may contain air or may contain an inert gas or the like.

  In the present invention, the concavo-convex portion is formed in a part or all of the crystal growth surface in a direction perpendicular or substantially perpendicular to the first crystal axis. Here, “perpendicular or substantially perpendicular” is preferably within a range of about ± 20 degrees with respect to an axis perpendicular to the first crystal axis direction, and more preferably within a range of about ± 10 degrees. Most preferably within the range of about ± 5 degrees.

  FIG. 2 shows a preferred embodiment of the crystal growth substrate in the present invention. The crystal growth substrate 11 of FIG. 2 includes a crystal substrate 10 and a convex portion 2. The crystal substrate 10 has at least a crystal growth surface 1 and crystal axes different from the X axis, the Y axis, and the Z axis, and the arrow direction of the Y axis is the crystal growth direction. Further, the thermal expansion coefficient in the X-axis direction is larger than the thermal expansion coefficient in the Z-axis direction. Therefore, the X axis is the first crystal axis, and the Z axis is the second crystal axis. Further, the crystal growth surface 1 of the crystal substrate 10 is provided with a convex portion 2, and the convex portion 2 is formed in a stripe shape in a direction perpendicular to the first crystal axis.

  FIG. 3 shows another preferred embodiment of the crystal growth substrate in the present invention. The crystal growth substrate 11 of FIG. 3 includes the crystal substrate 10 and the convex portion 2 as in FIG. The crystal substrate 10 has at least a crystal growth surface 1 and crystal axes different from the X axis, the Y axis, and the Z axis, and the arrow direction of the Y axis is the crystal growth direction. Further, the thermal expansion coefficient in the X-axis direction is larger than the thermal expansion coefficient in the Z-axis direction. Therefore, the X axis is the first crystal axis, and the Z axis is the second crystal axis. Further, the crystal growth surface 1 of the crystal substrate 10 is provided with a convex portion 2, and the convex portion 2 is formed in a dot shape so as to face a direction perpendicular to the first crystal axis.

FIG. 4 shows another preferred embodiment of the crystal growth substrate in the present invention. The crystal growth substrate 11 of FIG. 4 includes a crystal substrate 10 and a mask layer 5. The crystal substrate 10 has at least a crystal growth surface 1 and crystal axes different from the X axis, the Y axis, and the Z axis, and the arrow direction of the Y axis is the crystal growth direction. Further, the thermal expansion coefficient in the X-axis direction is larger than the thermal expansion coefficient in the Z-axis direction. Therefore, the X axis is the first crystal axis, and the Z axis is the second crystal axis. The mask layer 5 has a recess 3 formed in a direction perpendicular to the first crystal axis. The recess 3 is formed by forming a dot-like hole in the mask layer 5, and the crystal substrate 10 is exposed from the hole. The mask layer 5 is not particularly limited as long as it is a layer that can inhibit the crystal growth in the vertical direction. Examples of the constituent material of the mask layer 5 include known materials such as a silicon-containing compound such as SiO ₂ , and the mask layer 5 can be formed using a known means such as photolithography.

  FIG. 5 shows another preferred embodiment of the crystal growth substrate in the present invention. The crystal growth substrate 11 of FIG. 5 includes a recess 3 in the crystal substrate 10. The crystal substrate 10 has at least a crystal growth surface 1 and crystal axes different from the X axis, the Y axis, and the Z axis, and the arrow direction of the Y axis is the crystal growth direction. Further, the thermal expansion coefficient in the X-axis direction is larger than the thermal expansion coefficient in the Z-axis direction. Therefore, the X axis is the first crystal axis, and the Z axis is the second crystal axis. In addition, a groove is provided as a recess 3 in the crystal growth surface 1 of the crystal substrate 10, and the recess 3 is formed in a stripe shape in a direction perpendicular to the first crystal axis. In addition, formation of the said recessed part 3 can be performed using a well-known groove processing means.

  “Thermal expansion coefficient” refers to a value measured according to JIS R1618. Here, as an example of a sapphire substrate suitable for the present invention, for example, when the crystal substrate is an a-plane sapphire substrate, the c-axis is the first crystal axis and the m-axis is the second crystal axis. Is most preferable.

  In the present invention, other layers such as a buffer layer and a stress relaxation layer may be provided on the crystal substrate. Thus, when providing other layers, the other layers may be provided on the other layers. However, although the said uneven part may be formed, Preferably, the said uneven part is formed on another layer.

  The crystal growth substrate is preferably used as a substrate for epitaxial crystal growth. Using the crystal growth substrate, an epitaxial film can be formed by epitaxial crystal growth on the crystal growth surface of the crystal growth substrate to produce a crystalline laminated structure, thus obtained. Crystalline laminated structures are also included in the present invention.

  The crystalline stacked structure is not particularly limited as long as an epitaxial film formed by epitaxial crystal growth is formed on the crystal growth surface of the crystal growth substrate.

  The “crystalline stacked structure” is a structure including one or more crystal layers, and may include a layer other than the crystal layer (eg, an amorphous layer). The crystal layer is preferably a single crystal layer, but may be a polycrystalline layer.

  The epitaxial film is not particularly limited as long as it is a crystal-grown film, but in the present invention, the epitaxial film preferably has a corundum structure. The epitaxial film is preferably a crystalline semiconductor film. Examples of the semiconductor that is a main component of the crystalline semiconductor film include silicon-based semiconductors such as Si, SiGe, and SiC, gallium-based semiconductors such as GaAs, GaN, and GaP, and indium-based semiconductors such as InP and InAs. . In the present invention, the semiconductor is preferably a semiconductor containing gallium (Ga) or silicon (Si), more preferably an oxide semiconductor, and most preferably at least gallium.

  The epitaxial crystal growth means is not particularly limited as long as the object of the present invention is not impaired, and may be a known means. Examples of the epitaxial crystal growth means include CVD, MOCVD, MOVPE, mist CVD, mist / epitaxy, MBE, HVPE, and pulse growth. In the present invention, the epitaxial crystal growth means is preferably a mist CVD method or a mist epitaxy method.

  Hereinafter, as a preferred example of the present invention, the present invention will be described in more detail with reference to an example in which a crystalline oxide thin film is formed on the crystal growth substrate as the epitaxial film using a mist CVD method. .

  The crystalline oxide thin film is preferably a crystalline oxide semiconductor thin film, and the crystalline oxide semiconductor thin film may be subjected to an annealing treatment, so that the crystalline thin film is interposed between the crystalline thin film and the ohmic electrode. A metal oxide film in which the ohmic electrode is alloyed / mixed may be formed. Examples of the ohmic electrode include aluminum (Al), titanium (Ti), nickel (Ni), gold (Au), chromium (Cr), tungsten (W) and vanadium (V), and platinum (Pt), Examples include palladium (Pd), gold (Au) chromium (Cr), nickel (Ni), copper (Cu), and cobalt (Co).

  The crystalline oxide thin film may contain a dopant. The dopant is not particularly limited and may be a known one. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium or niobium, or p-type dopants. In the present invention, the dopant is preferably Ge or Si. The Ge or Si content is preferably 0.00001 atomic% or more, more preferably 0.00001 atomic% to 20 atomic% in the composition of the crystalline oxide thin film, and 0.00001. Most preferably, it is from atomic percent to 10 atomic percent.

  Further, the crystalline oxide thin film does not substantially contain carbon. “Substantially free of carbon” specifically means that the carbon content is 0.1 atomic% or less in the composition of the crystalline oxide thin film, preferably 0. 0.01 atomic percent or less, more preferably 0.001 atomic percent or less.

  Further, the crystalline oxide thin film preferably has a half width of 50 arcsec or less, and more preferably 40 arcsec or less. The half width is the half width of X-ray measurement (out-of-plane measurement).

<Crystalline oxide thin film>
The crystalline oxide thin film preferably contains a crystalline oxide having a corundum structure or a crystalline oxide having a β-gallia structure as a main component, and the crystalline oxide is α-Ga ₂ O. More preferably, ₃ or β-Ga ₂ O ₃ is contained as a main component. The "main component", when crystalline oxide is α-Ga ₂ O _3, the atomic ratio of gallium in a metal element of the thin film contains α-Ga ₂ O ₃ at a ratio of more than 0.5 If so, that's fine. In the present invention, the atomic ratio of gallium in the metal element in the thin film is preferably 0.7 or more, and more preferably 0.8 or more. The thickness of the crystalline oxide semiconductor thin film is not particularly limited, and may be 1 μm or less or 1 μm or more. In the present invention, it is preferably 3 μm or more, and 5 μm. More preferably, it is more preferably 10 μm or more. The crystalline oxide thin film is usually a single crystal, but may be polycrystalline.

  The crystalline oxide thin film may be formed directly on the crystal substrate or may be formed via another layer. As another layer, a corundum structure crystal thin film having a different composition, a crystal thin film other than the corundum structure, an amorphous thin film, or the like can be given. The structure may be a single layer structure or a multi-layer structure. Two or more crystal phases may be mixed in the same layer. In the case of a multi-layer structure, the crystalline oxide thin film is configured by, for example, laminating an insulating thin film and a conductive thin film, but is not limited to this in the present invention. In addition, when an insulating thin film and an electroconductive thin film are laminated | stacked and a multiple layer structure is comprised, the composition of an insulating thin film and an electroconductive thin film may be the same, or may mutually differ. The ratio of the thickness of the insulating thin film to the conductive thin film is not particularly limited. For example, the ratio of (thickness of the conductive thin film) / (thickness of the insulating thin film) is 0.001 to 100. Preferably, 0.1-5 is more preferable. This more preferable ratio is specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, 5 and illustrated here It may be within a range between any two of the numerical values.

  The conductive thin film may be doped with an impurity so as to impart conductivity to the extent that the object of the present invention is not impaired. The insulating thin film normally does not require impurity doping, but may be doped to such an extent that conductivity does not appear.

  The crystalline laminated structure is formed by supplying raw material fine particles generated by atomizing a raw material solution to a film forming chamber by a carrier gas, and placing the crystalline oxide thin film on the base substrate disposed in the film forming chamber. Manufactured by forming. In the present invention, the doping treatment is preferably performed by including an abnormal grain inhibitor in the raw material solution. By manufacturing the raw material solution with an abnormal grain inhibitor and performing a doping treatment, a crystalline laminated structure having a crystalline oxide thin film having a surface roughness of 0.1 μm or less is produced industrially advantageously. Can do. The doping amount is not particularly limited as long as it does not hinder the object of the present invention, but is preferably 0.01 to 10%, more preferably 0.1 to 5% by volume in the raw material solution. . In the present invention, non-doping is also preferable.

  The abnormal grain inhibitor refers to those having an effect of suppressing generation of particles by-produced during the film formation process, and is not particularly limited as long as the surface roughness of the crystalline oxide thin film can be 0.1 μm or less. In the present invention, the abnormal grain inhibitor is preferably composed of at least one selected from Br, I, F and Cl. When Br or I is introduced into the thin film as an abnormal grain inhibitor for stable film formation, deterioration of the surface roughness due to abnormal grain growth can be suppressed. The amount of the abnormal grain inhibitor added is not particularly limited as long as abnormal grains can be suppressed, but in the raw material solution, the volume ratio is preferably 50% or less, more preferably 30% or less, and 1 to 20%. Most preferably within the range. By using the abnormal grain inhibitor in such a preferable range, it can function as an abnormal grain inhibitor, and thus the growth of abnormal grains of the crystalline oxide thin film can be suppressed and the surface can be smoothed. .

  The method for forming the crystalline oxide thin film is not particularly limited as long as the object of the present invention is not impaired. For example, a gallium compound and, if desired, an indium compound, an aluminum compound, or an iron compound are matched to the composition of the crystalline oxide thin film. It can be formed by subjecting the combined raw material compounds to an oxidation reaction. Thus, the crystalline oxide semiconductor thin film can be grown on the base substrate from the base substrate side. The gallium compound may be a gallium compound that is changed to a gallium compound immediately before film formation using gallium metal as a starting material. Examples of gallium compounds include gallium organometallic complexes (eg, acetylacetonate complexes) and halides (fluorides, chlorides, bromides, or iodides). In the present invention, halides (fluorides) are used. , Chloride, bromide, or iodide).

  The film formation temperature of the crystalline oxide thin film is not particularly limited, but is preferably 800 ° C. or lower, and more preferably 700 ° C. or lower. Further, the film formation may be performed under vacuum, non-oxygen atmosphere, reducing gas atmosphere, or oxygen atmosphere, as long as the object of the present invention is not impaired. The reaction may be performed under any conditions of atmospheric pressure, increased pressure, and reduced pressure, but in the present invention, it is preferably performed under normal pressure or atmospheric pressure. The film thickness can be set by adjusting the film formation time.

  Further, the type of carrier gas is not particularly limited as long as the object of the present invention is not impaired. For example, an inert gas such as oxygen, ozone, nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas is preferable. An example. Further, the type of carrier gas may be one type, but may be two or more types, and a diluent gas (for example, a 10-fold diluted gas) whose carrier gas concentration is changed is used as the second carrier gas. Further, it may be used. Further, the supply location of the carrier gas is not limited to one location but may be two or more locations. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min, and more preferably 1 to 10 L / min.

  More specifically, the crystalline oxide thin film is formed by supplying mist-like raw material fine particles generated from a raw material solution in which the raw material compound is dissolved to the film forming chamber and reacting the raw material compound in the film forming chamber. Can be formed. The solvent of the raw material solution is not particularly limited, but is preferably water, hydrogen peroxide solution or an organic solvent. In the present invention, the raw material compound is usually subjected to an oxidation reaction in the presence of a dopant raw material. The dopant raw material is preferably included in the raw material solution and atomized together with the raw material compound.

  Examples of the dopant material include a simple metal or a compound to be doped (eg, halide, oxide).

  According to the present invention, not only the crystallinity of the crystalline oxide thin film can be improved, but also the limit value of the film thickness can be extended. In the present invention, annealing may be performed after film formation.

  In the present invention, an oxide semiconductor layer and / or a nitride semiconductor layer (for example, a GaN-based semiconductor layer) may be provided directly or via another layer on the crystalline oxide thin film. .

The crystalline laminated structure is useful for a semiconductor device. Semiconductor devices formed using the crystalline stacked structure include transistors and TFTs such as MIS and HEMT, Schottky barrier diodes using semiconductor-metal junctions, PN or PIN diodes combined with other P layers, A light emitting / receiving element may be mentioned. In the present invention, the crystalline laminated structure can be used in a semiconductor device as it is or after the crystal substrate and the crystalline oxide thin film are peeled off.
In the present invention, a Schottky electrode is provided directly or via another layer on the crystalline oxide thin film of the crystalline multilayer structure, and directly or separately on the base substrate of the crystalline multilayer structure. A semiconductor device provided with an ohmic electrode is preferable through the layer, and the reliability of the semiconductor device itself can be improved by the semiconductor characteristics of the crystalline oxide thin film.
The Schottky electrode and the ohmic electrode may be known ones, and these can be provided in the crystalline laminated structure using a known means. In addition, as another layer in the case of passing through another layer, a well-known semiconductor layer, an insulator layer, a conductor layer, etc. are mentioned, These layers may be a well-known thing, In this invention, it is well-known. By these means, these layers can be laminated.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

1. Mist / Epitaxial Device First, the mist / epitaxy device 19 used in this embodiment will be described with reference to FIG. The mist / epitaxy device 19 adjusts the flow rate of the carrier gas sent from the carrier stage 22, the carrier gas source 22 for supplying the carrier gas, and the sample stage 21 on which the deposition target sample 20 such as the base substrate is placed. A flow rate adjusting valve 23, a mist generating source 24 in which a raw material solution 24a is stored, a container 25 in which water 25a is placed, an ultrasonic transducer 26 attached to the bottom surface of the container 25, and a quartz tube having an inner diameter of 40 mm. And a heater 28 installed in the periphery of the film forming chamber 27. The sample stage 21 is made of quartz, and the surface on which the deposition target sample 20 is placed is inclined from the horizontal plane. Both the film formation chamber 27 and the sample stage 21 are made of quartz, so that impurities derived from the apparatus are prevented from being mixed into the thin film formed on the film formation target sample 20.

2. Production of substrate for crystal growth <Example 1>
An a-plane sapphire substrate was used as the crystal substrate. The crystal growth surface is a-plane, the first crystal axis is c-axis, the second crystal axis is m-axis, SOG is applied with a spin coater, and is perpendicular to the c-axis by photolithography. A stripe of SiO ₂ was formed on the a-plane sapphire substrate. The thermal expansion coefficient of the sapphire substrate is higher in thermal expansion coefficient parallel to the c-axis than the thermal expansion coefficient perpendicular to the c-axis. For example, the thermal expansion coefficient parallel to the c-axis at 40 to 400 ° C. is 7.7 × 10 ⁻⁶ / K, and the thermal expansion coefficient perpendicular to the c-axis is 7.0 × 10 ⁻⁶ / K.

<Comparative Example 1>
A c-plane sapphire substrate was used as the crystal substrate. The crystal growth surface is the c-plane, the first crystal axis is the a-axis, the second crystal axis is the m-axis, SOG is applied by a spin coater, and after firing, becomes perpendicular to the a-axis using a photolithography method. Thus, a stripe of SiO ₂ was formed on the c-plane sapphire substrate.

<Comparative example 2>
A c-plane sapphire substrate was used as the crystal growth substrate.

3. Preparation of Raw Material Solution An aqueous solution of gallium bromide 0.1 mol / L was prepared. At this time, a 48% hydrobromic acid solution was further added so as to be 10% by volume, and this was used as a raw material solution.

4). Preparation of film formation The raw material solution 24a obtained in the above was accommodated in the mist generating source 24. Next, a square crystal growth substrate having a side of 10 mm is placed on the sample stage 21 as the film formation sample 20, and the heater 28 is operated to raise the temperature in the film formation chamber 27 to 580 ° C. I let you. Next, the flow rate adjusting valve 23 is opened to supply the carrier gas from the carrier gas source 22 into the film forming chamber 27, and the atmosphere in the film forming chamber 27 is sufficiently replaced with the carrier gas. Adjusted to min. Note that oxygen was used as a carrier gas.

5. Next, the ultrasonic vibrator 26 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 24a through the water 25a, whereby the raw material solution 24a was made fine to produce raw material fine particles. The raw material fine particles were introduced into the film forming chamber 27 by the carrier gas, and reacted in the film forming chamber 27 at 580 ° C. to form a thin film on the film forming sample 20. The film formation time was 6 hours.

6). Evaluation 5. The phase of the α-Ga ₂ O ₃ thin film obtained in (1) was identified. Identification was performed by performing 2θ / ω scanning at an angle of 15 to 95 degrees using an XRD diffractometer for thin films. The measurement was performed using CuKα rays. As a result, both the films of Example 1 and Comparative Examples 1 and 2 were α-Ga ₂ O ₃ .

  Moreover, the film-forming rate was computed from the film thickness about the film | membrane of Example 1 and Comparative Examples 1-2. The results are shown in Table 1.

  The cross section of the epitaxial film of Example 1 was examined using an optical microscope. The results are shown in FIG. The cross section of the epitaxial film of Comparative Example 1 was also examined using an optical microscope. The results are shown in FIG. As is apparent from FIG. 8, it can be seen that in most regions, there is not much growth in the lateral direction.

<Production example>
A periodic stripe-like groove structure having a terrace width of about 3 μm, a groove width of about 5 μm, and a groove depth of about 3 μm is formed on an a-plane sapphire substrate, and this is used as a recess. Using a sapphire substrate, a film was formed in the same manner as in Example 1. The phase of the film obtained by X-ray diffraction, films were confirmed to be α-Ga ₂ O ₃ film having a corundum structure. The half width was 83 arcsec.

  The crystal growth substrate of the present invention is useful for the production of a crystalline multilayer structure, and the crystalline multilayer structure is a semiconductor (for example, a compound semiconductor electronic device), an electronic component / electric equipment component, an optical / electrophotography. Although it can be used in various fields such as related devices and industrial members, it is particularly useful for semiconductor devices.

DESCRIPTION OF SYMBOLS 1 Crystal growth surface 2 Convex part 3 Concave part 5 Mask layer 10 Crystal substrate 11 Substrate for crystal growth 19 Mist / epitaxy apparatus 20 Film formation sample 21 Sample stage 22 Carrier gas source 23 Flow control valve 24 Mist generation source 24a Raw material solution 25 Container 25a Water 26 Ultrasonic vibrator 27 Deposition chamber 28 Heater

Claims (9)

On the crystal growth surface of the crystal substrate, a concavo-convex portion consisting of a convex portion or a concave portion is formed directly or via another layer to manufacture a crystal growth substrate, and then an epitaxial film is formed to form a crystalline laminate In the method for manufacturing a structure, the formation of the concavo-convex portion has first and second crystal axes perpendicular or substantially perpendicular to the crystal growth direction, and further heat in the first crystal axis direction. As the concavo-convex portion in a direction perpendicular to or substantially perpendicular to the first crystal axis on a part or all of the crystal growth surface of the crystal substrate having an expansion coefficient larger than the thermal expansion coefficient in the second crystal axis direction , There row by forming a plurality of uneven portions periodically, the deposition of the epitaxial layer, on the crystal growth surface of said crystal growth substrate, by forming an epitaxial film having a corundum structure as said epitaxial layer especially the line Ukoto Manufacturing method to. Uneven portion, the manufacturing method according to claim 1 Symbol placement crystalline layered structure in a striped shape. Thermal expansion coefficient difference between the first and second crystal axis direction, the crystal growth temperature, method for producing a crystalline layered structure according to claim 1 or 2 is 0.5 × 10 ^-6 K ^-1 or higher . A crystal growth substrate in which a concavo-convex portion including a convex portion or a concave portion is formed directly or via another layer on a crystal growth surface of the crystal substrate, wherein the crystal substrate is perpendicular to the crystal growth direction or The first and second crystal axes are substantially perpendicular, and the thermal expansion coefficient in the first crystal axis direction is larger than the thermal expansion coefficient in the second crystal axis direction, and a part of the crystal growth surface or Crystalline laminated structure in which an epitaxial film is formed on the crystal growth surface of the substrate for crystal growth in which the concavo-convex part is formed in a direction perpendicular or substantially perpendicular to the first crystal axis A crystalline laminated structure characterized in that the crystal growth direction of the epitaxial film is perpendicular or substantially perpendicular to the first crystal axis and the second crystal axis, and the epitaxial film has a corundum structure. . The crystalline multilayer structure according to claim 4 , wherein the epitaxial film has a thickness of 10 μm or more . The crystalline multilayer structure according to claim 4 or 5 , wherein the epitaxial film contains an oxide semiconductor as a main component. The crystalline stacked structure according to claim 6 , wherein the oxide semiconductor contains at least gallium. The crystalline multilayer structure according to any one of claims 4 to 7 , wherein the crystal substrate is a sapphire substrate. The semiconductor device using a crystalline layered structure according to any one of claims 4-8.