JP2021080127A - Peeling method and method for manufacturing crystalline oxide film - Google Patents

Abstract

To provide a method for manufacturing a crystalline oxide film, capable of industrially, advantageously obtaining a crystalline oxide self-supporting film having a corundum structure useful for a semiconductor device and the like, and a peeling method.SOLUTION: The method for manufacturing a crystalline oxide film comprises: depositing a crystalline oxide film including a main component different from the main component of a crystal growth substrate through a peeling sacrificial layer by crystal growth on the crystal growth substrate having a crystal growth surface and a corundum structure, having different linear thermal expansion coefficients in a first direction along the crystal growth surface and a second direction vertical or approximately vertical to the first direction along the crystal growth surface and having the linear thermal expansion coefficient in the first direction larger than that in the second direction; and peeling the crystalline oxide film from the crystal growth substrate from the second direction using the peeling sacrificial layer.SELECTED DRAWING: Figure 2

Description

The present invention relates to a peeling method for obtaining a crystalline oxide film useful for a semiconductor device and a method for producing the crystalline oxide film.

As a next-generation switching element capable of achieving high withstand voltage, low loss, and high heat resistance, _{semiconductor devices using gallium oxide (Ga 2} O ₃ ) having a large bandgap are attracting attention, and are used for power semiconductor devices such as inverters. Expected to be applied. Further, it is expected to be widely applied as a light receiving / receiving device such as an LED or a sensor due to a wide band gap. In particular, among gallium oxide, α-Ga ₂ O _{3 and the} like having a corundum structure can control the band gap by forming a mixed crystal of indium and aluminum, respectively, or in combination, according to Non-Patent Document 1. , InAlGaO-based semiconductors constitute an extremely attractive material system. Here InAlGaO based semiconductor and the _{In X Al Y Ga Z O 3} (0 ≦ X ≦ 2,0 ≦ Y ≦ 2,0 ≦ Z ≦ 2, X + Y + Z = 1.5~2.5) indicates (Patent Document 9 Etc.), it can be overlooked as the same material system containing gallium oxide.

However, since the most stable phase of gallium oxide has a β-Galia structure, it is difficult to form a crystal film having a corundum structure, which is a semi-stable phase, unless a special film forming method is used. For example, hetero Crystal growth conditions are often restricted by epitaxial growth and the like, and therefore the dislocation density tends to be high. In addition to the crystal film having a corundum structure, there are still many problems in improving the film formation rate and crystal quality, suppressing cracks and abnormal growth, suppressing twins, and cracking the substrate due to warpage. Under such circumstances, some studies are currently being conducted on the formation of crystalline semiconductors having a corundum structure.

Patent Document 1 describes a method for producing an oxide crystal thin film by a mist CVD method using a bromide or iodide of gallium or indium. Patent Documents 2 to 4 describe a multilayer structure in which a semiconductor layer having a corundum-type crystal structure and an insulating film having a corundum-type crystal structure are laminated on a base substrate having a corundum-type crystal structure. .. Further, as in Patent Documents 5 to 7, film formation by mist CVD using an ELO substrate or void formation is also being studied.
Patent Document 8 describes that at least a gallium oxide having a corundum structure is formed by a halide vapor deposition method (HVPE method) using a gallium raw material and an oxygen raw material. Further, Patent Documents 10 and 11 describe that ELO crystal growth is carried out using a PSS substrate to obtain a crystal film having ^{a surface area of 9 μm 2} or more and a dislocation density of ^{less than 5 × 10 6} cm- ^2. ing. However, gallium oxide has a problem in heat dissipation, and in order to solve the problem in heat dissipation, for example, it is necessary to reduce the thickness of gallium oxide to 30 μm or less, but the polishing process becomes complicated and the cost increases. In addition, there is a problem that it is difficult to obtain a large-area gallium oxide film while maintaining the film thickness distribution when the film is thinned by polishing. In addition, the series resistance in the case of a vertical device was not sufficiently satisfactory. Therefore, in order to fully demonstrate the performance of gallium oxide as a power device, it is important to easily obtain a high-quality self-supporting film of gallium oxide, and a method for easily obtaining a high-quality self-supporting film of gallium oxide is desired. It was.
All of Patent Documents 1 to 11 are publications relating to patents or patent applications by the applicants, and are still under study.

Patent No. 5397794 Patent No. 5343224 Patent No. 5397795 Japanese Unexamined Patent Publication No. 2014-72533 Japanese Unexamined Patent Publication No. 2016-100592 Japanese Unexamined Patent Publication No. 2016-98166 Japanese Unexamined Patent Publication No. 2016-100593 Japanese Unexamined Patent Publication No. 2016-155714 International Publication No. 2014/050793 US Publication No. 2019/0057865 Japanese Unexamined Patent Publication No. 2019-034883

Kentaro Kaneko, "Growth and Physical Properties of Corundum Structure Gallium Oxide Mixed Crystal Thin Film", Doctoral Dissertation, Kyoto University, March 2013

An object of the present invention is to provide a method for producing a crystalline oxide film and a method for peeling off a crystalline oxide film capable of industrially obtaining a self-supporting film of a crystalline oxide having a corundum structure useful for a semiconductor device or the like.

As a result of diligent studies to achieve the above object, the present inventors have a crystal growth substrate having a crystal growth plane and a corundum structure, and the first substrate along the crystal growth plane. The first direction and the second direction along the crystal growth plane and perpendicular to or substantially perpendicular to the first direction have different linear thermal expansion coefficients. Crystalline oxidation containing a main component different from the main component of the crystal growth substrate via a peeling sacrificial layer on a crystal growth substrate whose linear thermal expansion coefficient in the direction is larger than the linear thermal expansion coefficient in the second direction. Production of a crystalline oxide film including forming a film by crystal growth and peeling the crystalline oxide film and the crystal growth substrate from the second direction using the peeling sacrificial layer. According to the method, it was found that the peeling proceeded cleanly from a certain direction and a free-standing film of crystalline oxide having a corundum structure could be easily obtained, and such a method solved the above-mentioned conventional problems at once. Found to get.

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

That is, the present invention relates to the following invention.
[1] A crystal growth substrate having a crystal growth plane and having a corundum structure, in a first direction along the crystal growth plane, along the crystal growth plane, and said. The second direction, which is perpendicular to or substantially perpendicular to the first direction, has different linear thermal expansion coefficients, and the linear thermal expansion coefficient in the first direction is the line in the second direction. A crystalline oxide film containing a main component different from the main component of the crystal growth substrate is formed on the crystal growth substrate larger than the thermal expansion coefficient through the peel sacrifice layer by crystal growth, and the peel sacrifice is formed. A method for producing a crystalline oxide film, which comprises peeling the crystalline oxide film and the crystal growth substrate from the second direction using a layer.
[2] The production method according to the above [1], wherein the crystal growth substrate contains an oxide.
[3] The production method according to the above [1] or [2], wherein the crystalline oxide film has a corundum structure.
[4] The production method according to any one of the above [1] to [3], wherein the crystalline oxide film contains at least gallium oxide.
[5] The production method according to any one of [1] to [4], wherein the peeling sacrificial layer has uneven portions arranged in the c-axis direction of the crystal growth substrate.
[6] The manufacturing method according to the above [5], wherein the uneven portion has a striped shape and extends in a direction within a range of 30 ° to 150 ° with respect to the c-axis direction of the crystal growth substrate.
[7] The above-mentioned [5], wherein the uneven portion has a striped shape and extends in a direction within a range of 0.2 ° to 60 ° with respect to a direction perpendicular to the c-axis direction of the crystal growth substrate. Manufacturing method.
[8] The manufacturing method according to the above [6] or [7], wherein the stripes of the uneven portion are arranged so as to be parallel to each other.
[9] The production method according to any one of [5] to [8], wherein the uneven portion includes a mask.
[10] The manufacturing method according to the above [9], wherein the uneven portion has a convex portion and the convex portion is a mask.
[11] The manufacturing method according to the above [8], wherein the uneven portion has at least two or more convex portions.
[12] The production method according to any one of [8] to [10] above, wherein the mask contains an oxide.
[13] The production method according to any one of the above [1] to [12], wherein the crystal growth plane is the m-plane or the r-plane.
[14] A crystal growth substrate having a crystal growth plane and having a corundum structure, in a first direction along the crystal growth plane, along the crystal growth plane, and said. The crystal growth substrate is formed on the crystal growth substrate having different linear thermal expansion coefficients in the second direction, which is perpendicular to the first direction or substantially perpendicular to the first direction, via a peeling sacrificial layer. A crystalline oxide film containing a main component different from the main component is formed by crystal growth, and the crystal growth sacrificial layer is used to form the crystalline oxide film and the crystal growth substrate from the second direction. A peeling method that involves peeling.

According to the production method of the present invention, it is possible to obtain an industrially advantageous self-supporting film of a crystalline oxide film having a corundum structure useful for semiconductor devices and the like.

It is a schematic diagram explaining a part of the manufacturing process in embodiment of this invention. It is a schematic diagram explaining a part of the manufacturing process in embodiment of this invention. It is a schematic diagram explaining a part of the manufacturing process in embodiment of this invention. It is a schematic diagram explaining a part of the manufacturing process in embodiment of this invention. It is a figure explaining the halide vapor deposition (HVPE) apparatus used in embodiment of this invention. It is a schematic diagram which shows one aspect of the concavo-convex portion formed on the surface of the substrate used in the embodiment of this invention. It is a schematic diagram which shows one aspect of the concavo-convex portion formed on the surface of the substrate used in the embodiment of this invention. It is a schematic diagram which shows one aspect of the concavo-convex portion formed on the surface of the substrate used in the embodiment of this invention. It is a schematic diagram which shows one aspect of the concavo-convex portion formed on the surface of the substrate used in the embodiment of this invention. It is a schematic diagram which shows one aspect of the concavo-convex portion formed on the surface of the substrate used in the embodiment of this invention. It is a schematic diagram which shows the relationship between the uneven part formed on the surface of the substrate used in embodiment of this invention, and a crystal growth layer in cross section. It is a schematic diagram which cross-sectionally shows the relationship between the concavo-convex portion formed on the surface of the substrate used in the embodiment of this invention, a buffer layer and a crystal growth layer. It is a figure explaining the mist CVD apparatus used in embodiment of this invention. It is a photograph which shows the crack which causes spontaneous peeling in an Example of this invention. FIG. 5 is a photomicrograph showing the flatness of facets in the examples of the present invention. It is a micrograph which shows the flatness of each facet in the reference example of this invention. The numbers in the figure indicate the angle (°) between the extending direction of the uneven portion having each elongated shape and the c-axis, and the vertical direction in the vertical direction is the c-axis direction.

Each of the manufacturing method and the peeling method of the present invention is a crystal growth substrate having a crystal growth surface and a colland structure, and has a first direction along the crystal growth surface and the above. It has different linear thermal expansion coefficients along the crystal growth plane and in a direction perpendicular to or substantially perpendicular to the first direction, and has different linear thermal expansion coefficients in the first direction. Is a crystalline oxide film containing a main component different from the main component of the crystal growth substrate via a peeling sacrificial layer on the crystal growth substrate having a greater than the linear thermal expansion coefficient in the second direction (hereinafter, simply A "crystal growth layer" or "crystal film") is formed by crystal growth, and the crystal growth oxide film and the crystal growth substrate are formed from the second direction using the peeling sacrificial layer. It is characterized by including peeling. The peeling may be performed by peeling the crystalline oxide film and the crystal growth substrate, and at the time of the peeling, at least one of the crystalline oxide film and the crystal growth substrate is used. The peeling sacrificial layer or the like may or may not be attached, but in the present invention, it is preferable that the peeling sacrificial layer is attached to the crystal growth substrate.

(Substrate for crystal growth)
The crystal growth substrate (hereinafter, also simply referred to as “crystal substrate” or “substrate”) is a crystal growth substrate having a crystal growth surface and a colland structure, and the crystal growth. The first direction along the plane and the second direction along the crystal growth plane and perpendicular to or substantially perpendicular to the first direction have different linear thermal expansion coefficients. The crystal growth substrate is not particularly limited as long as the linear thermal expansion coefficient in the first direction is larger than the linear thermal expansion coefficient in the second direction. "Approximately vertical" is a direction preferably within a range of about ± 40 degrees, more preferably a range of about ± 20 degrees with respect to an axis perpendicular to the first direction along the crystal growth plane. The direction is inward, most preferably within the range of about ± 10 degrees. The "coefficient of thermal expansion" refers to a value measured in accordance with JIS R1618. Here, to give an example of a sapphire substrate suitable in the present invention, for example, in the case of an m-plane sapphire substrate, the c-axis direction may be the first method and the a-axis direction may be the second direction. Preferably, in the case of an r-plane sapphire substrate, the substantially c-axis direction (for example, the direction in which the c-axis is projected onto the r-plane) is used as the first method, and the substantially a-axis direction (for example, the a-axis is projected on the r-plane). The direction) is preferably the second direction.

The crystal growth substrate is not particularly limited as long as it is a substrate containing a crystal having a corundum structure as a main component, and may be a known substrate. The crystal growth substrate may be an insulator substrate, a conductive substrate, or a semiconductor substrate. The crystal growth substrate may be a single crystal substrate or a polycrystalline substrate. The "main component" refers to a composition ratio in the substrate containing 50% or more of the crystals, preferably 70% or more, and more preferably 90% or more. Examples of the substrate containing the crystal having a corundum structure as a main component include a sapphire substrate, an α-type gallium oxide substrate, and an α-type AlGaO substrate.

In the embodiment of the present invention, the crystal substrate is preferably an m-plane sapphire substrate or an r-plane sapphire substrate. Further, the crystal 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. The area of the crystal substrate is not particularly limited ^{, but is preferably 15 cm 2} or more, and more preferably 100 cm ² or more.

Further, in one of the embodiments of the present invention, it is preferable that the substrate has concave-convex portions or convex portions formed on the surface thereof, and such uneven portions are used as the peeling sacrificial layer. , More efficient and higher quality crystal growth layer can be obtained. The peeling sacrificial layer may be the concavo-convex portion, and 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 or an uneven portion composed of a concave portion. It may be a portion, or it may be an uneven portion composed of a convex portion and a concave portion. Further, the uneven portion may be formed from a regular convex portion or a concave portion, or may be formed from an irregular convex portion or a concave portion. In the present invention, it is preferable that the uneven portion is formed periodically, and it is more preferable that the uneven portion is periodically and regularly patterned. The mask is a mask in which the uneven portion is formed of the convex portion. Most preferably, the masks are patterned periodically and regularly. The pattern of the uneven portion is not particularly limited, and examples thereof include a striped shape, a dot shape, a mesh shape, and a random shape. In the present invention, the dot shape or the striped shape is preferable, and the dot shape is more preferable. The dot shape or the stripe shape may be the shape of the opening of the convex portion. When the uneven portion is patterned periodically and regularly, 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. The shape is preferably circular or elliptical. When forming the uneven portion in a dot shape, the lattice shape of the dots is preferably a lattice shape such as a square lattice, an oblique lattice, a triangular lattice, or a hexagonal lattice, and the lattice shape of the triangular lattice is used. Is more preferable. The cross-sectional shape of the concave or convex portion of the uneven portion is not particularly limited, and is, for example, U-shaped, U-shaped, inverted U-shaped, corrugated, or triangular, quadrangular (for example, square, rectangular, trapezoidal, etc.). ), Polygons such as pentagons and hexagons, etc.

In the present invention, it is preferable that the uneven portion has a striped shape and extends in a direction within a range of 30 ° to 150 ° with respect to the c-axis direction of the crystal growth substrate, and the crystal growth. The direction within the range of 0.2 ° to 60 ° with respect to the direction perpendicular to the c-axis direction of the substrate, that is, + 0.2 ° to + 60 ° with respect to the direction perpendicular to the c-axis direction of the crystal growth substrate. More preferably, it extends in a direction within the range of −0.2 ° to −60 °, and from 20 ° to a direction perpendicular to the c-axis direction of the crystal growth substrate. It extends in the direction of 40 °, that is, in the range of + 20 ° to + 40 ° or in the range of -20 ° to -40 ° with respect to the direction perpendicular to the c-axis direction of the crystal growth substrate. Is the most preferable. By using such a preferable striped uneven portion as the peeling sacrificial layer, the facet can be made flatter and the crystal growth can be made higher in quality.

The constituent material of the convex portion is not particularly limited, and may be a known mask material. It may be an insulator material, a conductor material, or a semiconductor material. Further, 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, Sn, nitrides or carbides, carbon, diamond, metal, and mixtures thereof. More specifically, _{a Si-containing compound containing SiO 2} , SiN or polycrystalline silicon as a main component, and a metal having a melting point higher than the crystal growth temperature of the crystalline oxide semiconductor (for example, platinum, gold, silver, palladium). , Rhodium, iridium, precious metals such as ruthenium, etc.). The content of the constituent material is preferably 50% or more, more preferably 70% or more, and most preferably 90% or more in the convex portion in terms of composition ratio. In the present invention, it is preferable that the mask contains an oxide.

The method for forming the convex portion may be a known method, and examples thereof include known patterning processing 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 striped or dot-shaped, and more preferably dot-shaped. The dot shape or the stripe shape may be the shape of the opening of the convex portion. Further, in the present invention, it is also preferable that the crystal substrate is 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 hemispherical shape, a square or triangular pyramid shape, and the like, but in the present invention, the pattern shape is preferably a cone shape. The pitch interval of the pattern shape is also not particularly limited, but in the embodiment of the present invention, it is preferably 100 μm or less, and more preferably 1 μm to 50 μm.

The concave portion is not particularly limited, but may be the same as the constituent material of the convex portion, or may be a substrate. In the present invention, the recess may be a void layer provided on the surface of the substrate. As the method for forming the concave portion, the same method as the method for forming the convex portion can be used. The void layer can be formed on the surface of the substrate by providing a groove on the substrate by a known grooving method. The groove width, groove depth, terrace width, etc. of the void layer are not particularly limited and can be appropriately set as long as the object of the present invention is not impaired. Further, the void layer may contain air, or may contain an inert gas or the like.

In the present invention, it is preferable that the peeling sacrificial layer has uneven portions arranged in the c-axis direction. According to such a preferable peeling sacrificial layer, cracks more suitable for natural peeling can be generated from a direction perpendicular to or substantially vertical to the c-axis direction, and it is easy to obtain a self-standing film of a higher quality crystal film. Become.

Hereinafter, an example of an embodiment of a substrate preferably used in the present invention will be described with reference to the drawings, but the present invention is not limited to these substrates.

FIG. 6 shows one aspect of the uneven portion provided on the crystal growth plane (m plane) of the crystal substrate in the present invention. The uneven portion in FIG. 6 is an uneven portion formed from the crystal substrate 1 and the convex portion 2a on the crystal growth surface 1a. On the crystal growth surface 1a of the crystal substrate 1, a plurality of elongated convex portions 2a extending in the a-axis direction are arranged in the c-axis direction. As shown in FIG. 6, a plurality of convex portions and concave portions are striped, and the stripes extend in the a-axis direction, and the stripes are arranged in the c-axis direction. Incidentally, the convex portion 2a is made of a silicon-containing compound and TiO ₂ such as titanium-containing compounds such as SiO ₂ can be formed using a known method such as photolithography.

FIG. 7 shows one aspect of the uneven portions arranged in the c-axis direction provided on the crystal growth plane (m plane) of the crystal substrate in the present invention. The uneven portion of FIG. 7 is formed of the crystal substrate 1 and the concave portion 2b. The recesses 2b are a plurality of grooves extending in the a-axis direction, and the plurality of grooves are arranged in the c-axis direction. The recess 2b can be formed by a known grooving method.

Further, FIG. 8 also shows one aspect of the uneven portion provided on the crystal growth surface 1a of the crystal substrate 1 in the present invention. In the plurality of uneven portions shown in FIG. 8, the width of the interval between the recesses 2b is smaller than that in the recesses 2b of FIG. That is, the terrace width of the recess 2b is wide in FIG. 7 and narrow in FIG. The recess 2b of FIG. 8 can also be formed by using a known grooving method, similarly to the recess of FIG.

FIG. 9 shows one aspect of the uneven portions arranged in the c-axis direction provided on the crystal growth plane of the crystal substrate (m plane) in the present invention. The uneven portion of FIG. 9 is formed of a crystal substrate 1 and a convex portion 2a provided on the crystal growth surface 1a. The convex portion 2a is a dot-shaped mask, and the dot-shaped convex portions 2a are periodically and regularly arranged on the crystal growth surface 1a of the crystal substrate 1. The dots of the convex portion 2a are arranged more densely in the a-axis direction than in the c-axis direction. Further, the convex portion 2a is made _{of a silicon-containing compound such as SiO 2} , and can be formed by using a known method such as photolithography.

FIG. 10 shows one aspect of the uneven portions arranged in the c-axis direction provided on the crystal growth plane of the crystal substrate (m plane) in the present invention. FIG. 10 has a concave portion 2b instead of a convex portion. The recess in FIG. 10 is formed of the crystal substrate 1 and the mask layer 4. The mask layer 4 is formed on the crystal substrate 1 and has a plurality of dots-like holes. The crystal substrate 1 is exposed from the plurality of dot-shaped holes of the mask layer 4, and the plurality of dot-shaped holes of the mask layer 4 are located on the crystal growth surface 1a of the crystal substrate 1 and a plurality of recesses 2b are formed. It is formed. The dot-shaped holes of the mask layer 4 are arranged more densely in the a-axis direction than in the c-axis direction. The recess 2b can be obtained by forming a hole in the mask layer 4 by using a known method such as photolithography. Further, the mask layer 4 is not particularly limited as long as it is a layer capable of inhibiting crystal growth in the vertical direction. Examples of the constituent material of the mask layer 4 include known materials such as silicon-containing compounds such as _{SiO 2.}

The width and height of the convex portion of the uneven portion, the width and depth of the concave portion, the interval, and the like are not particularly limited, but in the present invention, each is in the range of, for example, about 10 nm to about 1 mm, preferably about 10 nm to about 10 nm. It is about 300 μm, more preferably about 10 nm to about 1 μm, and most preferably about 100 nm to about 1 μm.

Next, the relationship between the uneven portion formed on the surface of the substrate preferably used in the embodiment of the present invention and the crystal growth layer will be described. FIG. 11 is a cross-sectional view showing the relationship between the uneven portion formed on the surface of the substrate and the crystal growth layer, which is preferably used in the embodiment of the present invention. In the crystalline laminated structure of FIG. 11, a convex portion 5 is formed on the crystal substrate 1, and an epitaxial layer 8 is further formed by crystal growth. In the epitaxial layer 8, a crystalline semiconductor having a corundum structure is crystal-grown in the lateral direction due to the convex portion 5, and the crystal film having the corundum structure thus obtained has a corundum structure without uneven portions. It is a high-quality crystal film that is completely different from the crystal film that it has. Further, FIG. 12 shows an example in which a buffer layer is provided. In the crystalline laminated structure of FIG. 12, the buffer layer 7 is formed on the crystal substrate 1, and the convex portion 5 is formed on the buffer layer 7. Then, the epitaxial layer 8 is formed on the convex portion 5. Similarly to FIG. 11, in the crystalline laminated structure of FIG. 12, a crystal film having a corundum structure is crystal-grown in the lateral direction due to the convex portion 5, and a crystal film having a high-quality corundum structure is formed. There is.

The crystal growth layer (hereinafter, the crystal growth layer obtained by crystal growth including lateral crystal growth on the crystal substrate is also simply referred to as “transverse crystal growth layer”) is, for example, laterally placed on the crystal growth substrate. It can be formed by crystal growth including directional crystal growth. "Crystal growth in the lateral direction" usually means that the crystal grows in a direction other than the direction that becomes the crystal growth axis of the crystal growth plane (that is, the crystal growth direction) with respect to the crystal growth substrate. In the present invention, the crystal grows. It is preferable to grow the crystal in a direction having an angle of 0.1 ° to 178 ° with respect to the growth direction, and more preferably to grow the crystal in a direction having an angle of 1 ° to 175 °. It is most preferable to grow the crystal in the direction of the angle of. In the present invention, it is preferable that the crystal growth layer has a corundum structure, and it is also preferable that the crystal growth layer contains a crystalline oxide as a main component. Further, in the present invention, the crystal growth layer preferably contains at least gallium, and more preferably contains _{Ga 2} O _3. In the present invention, since a crystal film useful for a semiconductor device can be obtained, it is preferable that the crystal growth layer (hereinafter, also referred to as “crystal film”) is a semiconductor film, and a wide band gap semiconductor film is preferable. More preferred. For each crystal growth, it is preferable to apply a CVD method such as HVPE or mist CVD using a substrate having concave or convex portions formed on the surface thereof. A groove may be provided on the substrate, or an ELO mask (hereinafter, also simply referred to as “mask”) that exposes at least a part of the surface of the substrate may be arranged on the substrate in the lateral direction. The crystal growth layer can be formed by crystal growth including growth. The film thickness of the crystal film is not particularly limited, but according to the production method, the film thickness of the crystal film can be easily reduced. Therefore, for example, the thermal conductivity of the crystal film is 100 W / When it is less than m · K, it is preferably 30 μm or less, and more preferably 1 μm to 30 μm.

Hereinafter, an example of a method for forming the crystal growth layer by using the HVPE method will be described.

As one of the embodiments of the HVPE method, for example, using the HVPE apparatus shown in FIG. 5, a metal source containing a metal is gasified to obtain a metal-containing raw material gas, and then the metal-containing raw material gas and an oxygen-containing raw material are used. When the gas is supplied onto the substrate in the reaction chamber to form a film, the reactive gas is supplied onto the substrate by using a substrate having concave or convex portions formed on the surface thereof. The film formation may be performed under the flow of the reactive gas.

(Metal source)
The metal source is not particularly limited as long as it contains a metal and can be gasified, and may be a simple substance of a metal 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, iridium and the like. 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 gallium alone. Most preferred. Further, the metal source may be a gas, a liquid, or a solid, but in the embodiment of the present invention, for example, when gallium is used as the metal, the metal source may be a gas, a liquid, or a solid. , The metal source is preferably a liquid.

The gasification method is not particularly limited and may be a known method as long as the object of the present invention is not impaired. In the embodiment of the present invention, the gasification method is preferably carried out by halogenating the metal source. The halogenating agent used for the halogenation is not particularly limited as long as the metal source can be halogenated, and may be a known halogenating agent. Examples of the halogenating agent include halogens and hydrogen halides. Examples of the halogen include fluorine, chlorine, bromine, iodine and the like. Examples of the hydrogen halide include hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide and the like. In the embodiment of the present invention, it is preferable to use hydrogen halide for the halogenation, and it is more preferable to use hydrogen chloride. In the present invention, the gasification is carried out by supplying halogen or hydrogen halide as a halogenating agent to the metal source and reacting the metal source with halogen or hydrogen halide at a temperature equal to or higher than the vaporization temperature of the metal halide. It is preferable to carry out the process by forming a metal halide. The halogenation reaction temperature is not particularly limited, but in the embodiment of the present invention, for example, the crystal growth substrate has a corundum structure, the metal of the metal source is gallium, and the halogenating agent is used. In the case of HCl, 900 ° C. or lower is preferable, 700 ° C. or lower is more preferable, and 400 ° C. to 700 ° C. is most preferable. Further, for example, when the crystal growth substrate has a β-gaul structure, the metal source is gallium, and the halogenating agent is HCl, the halogenation reaction temperature is preferably 500 ° C. or higher. , 500 ° C to 1100 ° C, more preferably 600 ° C to 110 ° C. The metal-containing raw material gas is not particularly limited as long as it is a gas containing the metal of the metal source. Examples of the metal-containing raw material gas include halides (fluoride, chloride, bromide, iodide, etc.) of the metal.

In the embodiment of the present invention, the metal source containing a metal is gasified to obtain a metal-containing raw material gas, and then the metal-containing raw material gas and the oxygen-containing raw material gas are supplied onto the substrate in the reaction chamber. Further, in the embodiment of the present invention, the reactive gas is supplied onto the substrate. Examples of the oxygen-containing raw material gas include O ₂ gas, CO ₂ gas, NO gas, NO ₂ gas, N ₂ O gas, H ₂ O gas, O ₃ gas and the like. In the embodiment of the present invention, the oxygen-containing raw material gas is preferably one kind or two or more kinds of gases selected from the group consisting of _{O 2} , H ₂ O and N ₂ O, and contains _{O 2.} Is more preferable. As one of the embodiments, the oxygen-containing raw material gas may contain _{CO 2.} The reactive gas is usually a reactive gas different from the metal-containing raw material gas and the oxygen-containing raw material gas, and does not include the inert gas. The reactive gas is not particularly limited, and examples thereof include an etching gas and the like. The etching gas is not particularly limited and may be a known etching gas as long as the object of the present invention is not impaired. In the embodiment of the present invention, the reactive gas is a halogen gas (for example, fluorine gas, chlorine gas, bromine gas, iodine gas, etc.), hydrogen halide gas (for example, phosphoric acid gas, hydrochloric acid gas, hydrogen bromide, etc.). Gas, hydrogen iodide gas, etc.), hydrogen gas, or a mixed gas of two or more of these, and the like, preferably containing hydrogen halide gas, and most preferably containing hydrogen chloride. The metal-containing raw material gas, the oxygen-containing raw material gas, and the reactive gas may contain a carrier gas. Examples of the carrier gas include an inert gas such as nitrogen and argon. The partial pressure of the metal-containing raw material gas is not particularly limited, but in the embodiment of 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 raw material gas is not particularly limited, but in the embodiment of the present invention, it is preferably 0.5 to 100 times the partial pressure of the metal-containing raw material gas, and 1 to 20 times. Is more preferable. The partial pressure of the reactive gas is also not particularly limited, but in the embodiment of the present invention, it is preferably 0.1 to 5 times the partial pressure of the metal-containing raw material gas, and 0.2 to 3 times. It is more preferable to double.

In the embodiment of the present invention, it is also preferable to supply the dopant-containing raw material gas to the substrate. The dopant-containing raw material gas is not particularly limited as long as it contains a dopant. The dopant is also not particularly limited, but in the embodiment of the present invention, it is preferable that the dopant contains one or more elements selected from germanium, silicon, titanium, zirconium, vanadium, niobium and tin. , Germanium, silicon, or tin is more preferred, and germanium is most preferred. By using the dopant-containing raw material gas in this way, the conductivity of the obtained film can be easily controlled. The dopant-containing raw material gas preferably has the dopant in the form of a compound (for example, a halide, an oxide, etc.), and more preferably in the form of a halide. The partial pressure of the dopant-containing raw material gas is not particularly limited, but in the embodiment of the present invention, it is preferably 1 × 10 ^-7 times to 0.1 times the partial pressure of the metal-containing raw material gas. More preferably, it is ^{5.5 × 10-6} times to 7.5 × 10 ^{−2 times.} In the embodiment of the present invention, it is preferable to supply the dopant-containing raw material gas together with the reactive gas onto the substrate.

Further, as a preferred embodiment of the present invention, mist CVD can also be suitably applied. Hereinafter, the mist CVD film forming apparatus 19 preferably used in the embodiment of the present invention will be described with reference to the drawings. The film forming apparatus 19 of FIG. 13 supplies a carrier gas source 22a for supplying a carrier gas, a flow control valve 23a for adjusting the flow rate of the carrier gas sent out from the carrier gas source 22a, and a carrier gas (diluted). A carrier gas (diluted) source 22b, a flow control valve 23b for adjusting the flow rate of the carrier gas (diluted) sent out from the carrier gas (diluted) source 22b, a mist generation source 24 containing the raw material solution 24a, and the like. A container 25 in which water 25a is placed, an ultrasonic transducer 26 attached to the bottom surface of the container 25, a film forming chamber 30, and a quartz supply pipe 27 connecting the mist generation source 24 to the film forming chamber 30. It is provided with a hot plate (heater) 28 installed in the film forming chamber 30. A substrate 20 is installed on the hot plate 28.

Then, as shown in FIG. 13, the raw material solution 24a is housed in the mist generation source 24. Next, the substrate 20 is installed on the hot plate 28, and the hot plate 28 is operated to raise the temperature in the film forming chamber 30. Next, the flow rate control valves 23 (23a, 23b) are opened to supply the carrier gas into the film forming chamber 30 from the carrier gas source 22 (22a, 22b), and the atmosphere of the film forming chamber 30 is sufficiently replaced with the carrier gas. After that, the flow rate of the carrier gas and the flow rate of the carrier gas (dilution) are adjusted respectively. Next, the ultrasonic vibrator 26 is vibrated and the vibration is propagated to the raw material solution 24a through the water 25a to atomize the raw material solution 24a and generate atomized droplets 24b. The atomized droplets 24b are introduced into the film forming chamber 30 by a carrier gas and transported to the substrate 20, and the atomized droplets 24b thermally react in the film forming chamber 30 under atmospheric pressure to cause a thermal reaction on the substrate 20. A film is formed on the 20.

In the embodiment of the present invention, a buffer layer including a stress relaxation layer or the like may be provided on the substrate. The buffer layer preferably has a thermal conductivity of 100 W / m · K or more at room temperature. Further, in the embodiment of the present invention, it is preferable that the substrate has the buffer layer on a part or all of the surface. The method for forming the buffer layer is not particularly limited, and may be a known method. Examples of the forming method include a spray method, a mist CVD method, an HVPE method, an MBE method, a MOCVD method, a sputtering method and the like. Hereinafter, a preferred embodiment in which the buffer layer is formed by the mist CVD method will be described in more detail.

The buffer layer is preferably used, for example, by atomizing or dropletizing the raw material solution using the mist CVD apparatus shown in FIG. 13 (atomization step), and using a carrier gas to atomize the obtained atomized droplets. It can be formed by transporting to the substrate (conveying step) and then thermally reacting the atomized droplets on a part or all of the surface of the substrate (buffer layer forming step). In the embodiment of the present invention, the crystal growth layer can be formed in the same manner.

(Atomization process)
The atomization step atomizes the raw material solution to obtain the atomized droplets. The method for atomizing the raw material solution is not particularly limited as long as the raw material solution can be atomized, and may be a known method. However, in the embodiment of the present invention, the atomizing method using ultrasonic waves is used. preferable. Atomized droplets obtained using ultrasonic waves have a zero initial velocity and are preferable because they float in the air. For example, instead of spraying them like a spray, they float in space and are transported as gas. Since it is a possible mist, it is not damaged by collision energy, so it is very suitable. The droplet size of the atomized droplet is not particularly limited and may be a droplet of about several mm, but is preferably 50 μm or less, and more preferably 0.1 to 10 μm.

(Raw material solution)
The raw material solution is not particularly limited as long as it can be atomized into droplets and the buffer layer can be obtained by mist CVD. Examples of the raw material solution include an aqueous solution of an organic metal complex of an atomizing metal (for example, an acetylacetonate complex) and a halide (for example, fluoride, chloride, bromide, iodide, etc.). The atomizing metal is not particularly limited, and such atomizing metal is selected from, for example, aluminum, gallium, indium, iron, chromium, vanadium, titanium, rhodium, nickel, cobalt, iridium and the like1 Species or two or more kinds of metals and the like can be mentioned. In the embodiment of the present invention, the atomizing metal preferably contains at least gallium, indium or aluminum, and more preferably at least gallium. The content of the atomizing metal in the raw material solution is not particularly limited as long as the object of the present invention is not impaired, but is preferably 0.001 mol% to 50 mol%, and more preferably 0.01 mol% to 0.01 mol%. It is 50 mol%.

It is also preferable that the raw material solution contains a dopant. By including the dopant in the raw material solution, the conductivity of the buffer layer can be easily controlled without breaking the crystal structure without performing ion implantation or the like. In embodiments of the present invention, the dopant is preferably tin, germanium, or silicon, more preferably tin, or germanium, and most preferably tin. The concentration of the dopant may be usually about 1 × 10 ¹⁶ / cm ³ to 1 × 10 ²² / cm ³ , and the concentration of the dopant is, for example, a low concentration of ^{about 1 × 10 17} / cm ^{3 or less.} Alternatively, the dopant may be contained in a high concentration of ^{about 1 × 10 20} / cm ^{3 or more.} In the embodiment of the present invention, the concentration of the dopant ^{is preferably 1 × 10 20} / cm ³ or less, and more preferably 5 × 10 ¹⁹ / cm ³ or less.

The solvent of the raw material solution is not particularly limited, and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solvent of the inorganic solvent and the organic solvent. In the embodiment of the present invention, the solvent preferably contains water, more preferably water or a mixed solvent of water and alcohol, and most preferably water. More specific examples of the water include pure water, ultrapure water, tap water, well water, mineral spring water, mineral water, hot spring water, spring water, fresh water, seawater, and the like. In the above, ultrapure water is preferable.

(Transport process)
In the transport step, the atomized droplets are transported into the film forming chamber by using a carrier gas. The carrier gas is not particularly limited as long as the object of the present invention is not impaired, and examples thereof include an inert gas such as oxygen, ozone, nitrogen and argon, and a reducing gas such as hydrogen gas and forming gas. .. Further, the type of carrier gas may be one type, but may be two or more types, and a diluted gas having a reduced flow rate (for example, a 10-fold diluted gas) or the like is further used as the second carrier gas. May be good. Further, the carrier gas may be supplied not only at one location but also at 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. In the case of a diluting gas, the flow rate of the diluting gas is preferably 0.001 to 2 L / min, more preferably 0.1 to 1 L / min.

(Buffer layer forming process)
In the buffer layer forming step, the buffer layer is formed on the substrate by thermally reacting the atomized droplets in the film forming chamber. The thermal reaction may be such that the atomized droplets react with heat, and the reaction conditions and the like are not particularly limited as long as the object of the present invention is not impaired. In this step, the thermal reaction is usually carried out at a temperature equal to or higher than the evaporation temperature of the solvent, but is preferably not too high (for example, 1000 ° C.) or lower, more preferably 650 ° C. or lower, and most preferably 400 ° C. to 650 ° C. preferable. Further, the thermal reaction may be carried out under any atmosphere of vacuum, non-oxygen atmosphere, reducing gas atmosphere and oxygen atmosphere as long as the object of the present invention is not impaired, and the thermal reaction may be carried out under atmospheric pressure or pressure. It may be carried out under either reduced pressure or reduced pressure, but in the present invention, it is preferably carried out under atmospheric pressure. The thickness of the buffer layer can be set by adjusting the formation time.

After forming the buffer layer on a part or all of the surface on the substrate as described above, the method for forming the preferable lateral crystal growth layer or the method for forming the buffer layer on the buffer layer is used. By forming the lateral crystal growth layer, defects such as tilt in the lateral crystal growth layer can be further reduced, and the film quality can be made more excellent.

The buffer layer is not particularly limited, but in the present invention, it is preferable that the buffer layer contains a metal oxide as a main component. Examples of the metal oxide include metal oxides containing one or more metals selected from aluminum, gallium, indium, iron, chromium, vanadium, titanium, rhodium, nickel, cobalt, iridium and the like. Be done. In the invention, the metal oxide preferably contains one or more elements selected from indium, aluminum and gallium, more preferably at least indium and / and gallium, and at least gallium. Is most preferable to contain. As one of the embodiments of the film forming method of the present invention, the buffer layer may contain a metal oxide as a main component, and the metal oxide contained in the buffer layer may contain gallium and a smaller amount of aluminum than gallium. .. By using a buffer layer containing a smaller amount of aluminum than gallium, not only good crystal growth but also good high temperature growth can be realized. Further, as one of the embodiments of the film forming method of the present invention, the buffer layer may include a superlattice structure. By using the buffer layer including the superlattice structure, not only good crystal growth can be realized, but also warpage during crystal growth can be suppressed more easily. Here, the "main component" is preferably 50% or more, more preferably 70% or more, still more preferably 90% or more of the metal oxide in terms of atomic ratio with respect to all the components of the buffer layer. It means that it is included, and it means that it may be 100%. The crystal structure of the crystalline oxide semiconductor is not particularly limited, but in the present invention, a corundum structure is preferable. Further, the lateral crystal growth layer and the buffer layer may have the same main components or different components as long as the object of the present invention is not impaired, but in the present invention, they are the same. Is preferable.

In the embodiment of the present invention, a metal-containing raw material gas, an oxygen-containing raw material gas, a reactive gas and, if desired, a dopant-containing raw material gas are supplied onto the substrate on which the buffer layer may be provided, and the reactive gas is supplied. The film is formed under the distribution of. In the present invention, it is preferable that the film formation is performed on a heated substrate. The film formation temperature is not particularly limited as long as the object of the present invention is not impaired, but is preferably 900 ° C. or lower, more preferably 700 ° C. or lower, and most preferably 400 ° C. to 700 ° C. Further, the film formation may be carried out under any of vacuum, non-vacuum, reducing gas atmosphere, inert gas atmosphere and oxidizing gas atmosphere as long as the object of the present invention is not impaired. Further, it may be carried out under normal pressure, atmospheric pressure, pressurization or reduced pressure, but in the above-described embodiment of the present invention, it is preferably carried out under normal pressure or atmospheric pressure. The film thickness can be set by adjusting the film formation time.

The lateral crystal growth layer usually contains a crystalline metal oxide as a main component. Examples of the crystalline metal oxide include metal oxides containing one or more metals selected from aluminum, gallium, indium, iron, chromium, vanadium, titanium, rhodium, nickel, cobalt, iridium and the like. Can be mentioned. In the present invention, the crystalline metal oxide preferably contains one or more elements selected from indium, aluminum and gallium, more preferably at least indium and / and gallium. , Crystalline gallium oxide or a mixed crystal thereof is most preferable. In the lateral crystal growth layer according to the embodiment of the present invention, the "main component" is preferably 50% of the crystalline metal oxide in terms of atomic ratio with respect to all the components of the lateral crystal growth layer. As described above, it means that it is more preferably contained in an amount of 70% or more, further preferably 90% or more, and may be 100% or more. In the embodiment of the present invention, a crystal growth film having a corundum structure can be obtained by performing the film formation using a substrate containing a corundum structure as the substrate. The crystalline metal oxide may be a single crystal or a polycrystal, but in the embodiment of the present invention, it is preferably a single crystal. The upper limit of the thickness of the lateral crystal growth layer is not particularly limited, but is, for example, 100 μm, and the lower limit of the thickness of the lateral crystal growth layer is not particularly limited, but is preferably 3 μm, preferably 10 μm. It is more preferably present, and most preferably 20 μm. In the present invention, the thickness of the lateral crystal growth layer is preferably 3 μm to 100 μm, more preferably 10 μm to 100 μm, and most preferably 20 μm to 100 μm.

In the present invention, it is preferable to form the convex portion as a mask on the lateral crystal growth layer. By forming the mask on the lateral crystal growth layer in this way, not only the crystallinity is simply improved, but also the dislocation density is reduced more satisfactorily, and the area of the crystal film is increased. can do. The mask may be the same as the convex portion. In the present invention, it is preferable that the lateral crystal growth layer includes two or more lateral crystal portions, and the masks are arranged on the two or more lateral crystal portions. In the two or more transverse crystal portions, two or more lateral crystal growth portions are formed in the transverse crystal growth, and two or more before the respective lateral crystal growth portions meet with each other. It may be a lateral crystal portion. By providing the mask on the lateral crystal portion in this way, it is possible to suppress warpage, cracks, and the like due to thermal stress generated by the association of the lateral crystals. The masks on the transverse crystal growth layer are preferably patterned periodically and regularly, and the spacing between the masks on the transverse crystal growth layer is greater than the spacing between the masks on the substrate. Is also preferably short. With such an interval, thermal stress and the like can be further relaxed, and a large-area and excellent crystalline crystal film can be obtained more easily. The distance between the masks on the lateral growth layer is not particularly limited, but is preferably 1 μm to 50 μm. In the present invention, it is preferable to peel off using the convex portion from the second direction having a small coefficient of linear thermal expansion because a more transparent and better quality self-supporting film can be obtained.

Hereinafter, the preferred production method of the present invention will be described in more detail with reference to the drawings.

As shown in FIG. 1, an ELO mask is formed on the surface of the substrate for crystal growth. An m-plane sapphire substrate is used as the crystal growth substrate. FIG. 1A shows a crystal growth substrate 1. As shown in FIG. 1 (b), the ELO mask 5 is formed on the crystal growth surface of the crystal growth substrate 1. The ELO mask 5 is not particularly limited, but preferably has a striped or dot-shaped pattern. A crystal growth layer is formed using the crystal growth substrate of FIG. 1 (b), and the laminated structure of FIG. 1 (c) is obtained. In the laminated structure (c), a crystal growth layer (transverse crystal growth layer) 8 is formed on a crystal growth substrate 1 having an ELO mask 5 on the surface, and the crystal growth is continued. As shown in 2 (d), the crystal growth substrate is peeled off. The crystalline oxide film of FIG. 3 (e) is obtained by peeling of FIG. 3 (d). The crystalline oxide film (e) thus obtained can have a large area as a self-supporting film, has a good film quality, and is excellent in semiconductor characteristics. Further, in the present invention, after the crystalline oxide film (e) is obtained, the support 9 is attached to the obtained crystalline oxide film (e) as shown in FIG. 4, and the laminated structure (f) is attached. ), For example, according to a conventional method such as CMP, the peeled surface of the crystalline oxide film of the laminated structure (f) can be polished to obtain the laminated structure (g) of FIG. 4 (g). , Such a laminated structure can also be used as a crystalline oxide film.

The crystalline oxide film obtained by the production method of the present invention can be particularly suitably used for a semiconductor device including at least an electrode and a semiconductor layer, and is particularly useful for a power device. In the present invention, it is preferable that the crystalline oxide film is a semiconductor film and the semiconductor film is used as the semiconductor layer. Examples of the semiconductor device formed by using the crystalline oxide film include transistors and TFTs such as MIS and HEMT, Schottky barrier diodes using semiconductor-metal junctions, and PN or PIN diodes combined with other P layers. A light receiving / receiving element can be mentioned. In the present invention, the crystalline oxide film may be used as it is in a semiconductor device or the like, or may be applied to a semiconductor device or the like after using a known method such as peeling from the substrate or the like.

Hereinafter, examples of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

(Example 1)
1. 1. Formation of buffer layer 1-1. Film-forming device In this example, the film-forming device 19 shown in FIG. 13 was used.

1-2. Preparation of Raw Material Solution To a _{0.1 M aqueous solution of gallium bromide (GaBr 3} ), 20% by volume of hydrobromic acid (HBr) was added, and this was used as a raw material solution.

1-3. Preparation for film formation 1-2. The raw material solution 24a obtained in 1) was housed in the mist generation source 24. Next, as the substrate 20, an m-plane sapphire substrate was used and installed on the hot plate 28, and the hot plate 28 was operated to raise the substrate temperature to 550 ° C. Next, the flow control valves 23a and 23b are opened to supply the carrier gas into the film forming chamber 30 from the carrier gas supply devices 22a and 22b which are the carrier gas sources, and the atmosphere of the film forming chamber 30 is sufficiently filled with the carrier gas. After the replacement, the flow rate of the carrier gas was adjusted to 1 L / min. Nitrogen was used as the carrier gas.

1-4. Film formation Next, the ultrasonic transducer 26 is vibrated at 2.4 MHz, and the vibration is propagated to the raw material solution 24a through water 25a to atomize the raw material solution 24a and mist (atomized droplets) 24b. Was generated. The mist 24b is introduced into the film forming chamber 30 by the carrier gas through the supply pipe 27, and the mist thermally reacts on the substrate 20 at 550 ° C. under atmospheric pressure and onto the substrate 20. A film was formed. The film formation time was 1 hour. The obtained film was an α-Ga ₂ O ₃ single crystal film when identified using an X-ray diffractometer.

2. Mask formation SOG is applied with a spin coater and photolithography is used to 1-4. On the m-plane sapphire substrate with the α-Ga ₂ O ₃ single crystal film obtained in FIG. 6, as shown in FIG. 6, a _{plurality of long masks of SiO 2} are placed on the sapphire substrate so as to be parallel to the a-axis. It was arranged so as to form a stripe with the upper surface (striped arrangement).

3. 3. Crystal growth and natural exfoliation of crystalline oxide film 1. _{In the same manner as in FIG. 13, a crystal growth layer made of α-Ga 2} O ₃ is formed by the mist CVD method using the mist CVD apparatus shown in FIG. 13, and by natural peeling due to cracks generated from the a-axis direction. The α-Ga ₂ O ₃ film and the crystal growth substrate were peeled off to obtain a self-supporting film of a crystalline oxide film. The evaluation of the obtained film was good as shown in Table 1. In the same manner as in Example 1, peeling was carried out for Examples 2 and 3 and Comparative Examples 1 and 2 under the conditions shown in Table 1, respectively, and evaluated. In Example 2, a photograph of a crack causing natural peeling could be clearly taken, which is shown in FIG. Peeling proceeds from the direction of the arrow in FIG. 14, and a self-supporting film can be easily obtained. Further, in Example 3, since the facets were flatter and the crystal growth was of higher quality, a micrograph is shown in FIG. 15 for reference. Regarding the third embodiment, the same applies not only to the stripe extending in the direction of 60 ° with respect to the c-axis direction but also to the ELO mask (striped arrangement) extending in the direction of 30 ° to 150 ° with respect to the c-axis direction. There was a tendency, and the ELO mask (striped arrangement) extending in the direction of 20 ° to 40 ° with respect to the direction perpendicular to the c-axis direction was particularly excellent in facet flatness.

(Reference example)
In the same manner as in Example 1 and Example 3, the ELO mask is applied to the stripe extending in the direction of + 60 ° with respect to the c-axis direction, the stripe extending in the direction perpendicular to the c-axis direction, and-with respect to the c-axis direction, respectively. Stripes extending in the direction of 60 ° were prepared, an α-Ga ₂ O ₃ film was formed, and the flatness of the facets in the crystal growth before natural peeling was evaluated. A photomicrograph is shown in FIG. As is clear from FIG. 16, there is no particular difference between the case of the stripe extending in the direction of + 60 ° with respect to the c-axis direction and the case of the stripe extending in the direction of -60 °, and ± 60 ° with respect to the c-axis direction. All of the stripes extending in the direction of were showing similar very good facet flatness.

The manufacturing method of the present invention can be used in all fields such as semiconductors (for example, compound semiconductor electronic devices, etc.), electronic parts / electrical equipment parts, optical / electrophotographic related devices, industrial parts, etc., but is particularly useful for semiconductor devices and the like. Is.

1 Crystal substrate (crystal growth substrate)
1a Substrate surface (crystal growth surface)
2a Convex part (peeling sacrificial layer)
2b recess (peeling sacrifice layer)
4 Mask layer (peeling sacrifice layer)
5 Peeling sacrifice layer (convex mask)
7 Buffer layer 8 Crystal growth layer (horizontal crystal growth layer)
9 Support 19 Mist device (deposition device)
20 Substrate 21 Suceptor 22a Carrier gas supply device 22b Carrier gas (dilution) supply device 23a Flow control valve 23b Flow control valve 24 Mist source 24a Raw material solution 25 Container 25a Water 26 Ultrasonic transducer 27 Supply pipe 28 Heater 29 Exhaust port 30 Formation chamber 50 Halide vapor phase growth (HVPE) device 51 Reaction chamber 52a Heater 52b Heater 53a Halogen-containing raw material gas supply source 53b Metal-containing raw material gas supply pipe 54a Reactive gas supply source 54b Reactive gas supply pipe 55a Oxygen-containing raw material gas Supply source 55b Oxygen-containing raw material gas supply pipe 56 Substrate holder 57 Metal source 58 Protective sheet 59 Gas discharge part

Claims (14)

A crystal growth substrate having a crystal growth plane and a corundum structure, the first direction along the crystal growth plane and the first direction along the crystal growth plane and the first one. The second direction, which is perpendicular to the direction or substantially perpendicular to the direction, has different linear thermal expansion coefficients, and the linear thermal expansion coefficient in the first direction is the linear thermal expansion coefficient in the second direction. A crystalline oxide film containing a main component different from the main component of the crystal growth substrate is formed by crystal growth on a larger crystal growth substrate via a peel sacrifice layer, and the peel sacrifice layer is used. A method for producing a crystalline oxide film, which comprises peeling the crystalline oxide film and the crystal growth substrate from the second direction. The production method according to claim 1, wherein the crystal growth substrate contains an oxide. The production method according to claim 1 or 2, wherein the crystalline oxide film has a corundum structure. The production method according to any one of claims 1 to 3, wherein the crystalline oxide film contains at least gallium oxide. The production method according to any one of claims 1 to 4, wherein the peeling sacrificial layer has uneven portions arranged in the c-axis direction of the crystal growth substrate. The manufacturing method according to claim 5, wherein the uneven portion has a striped shape and extends in a direction within a range of 30 ° to 150 ° with respect to the c-axis direction of the crystal growth substrate. The manufacturing method according to claim 5, wherein the uneven portion has a striped shape and extends in a direction within a range of 0.2 ° to 60 ° with respect to a direction perpendicular to the c-axis direction of the crystal growth substrate. The manufacturing method according to claim 6 or 7, wherein the stripes of the uneven portion are arranged so as to be parallel to each other. The manufacturing method according to any one of claims 5 to 8, wherein the uneven portion includes a mask. The manufacturing method according to claim 9, wherein the uneven portion has a convex portion, and the convex portion is a mask. The manufacturing method according to claim 8, wherein the uneven portion has at least two or more convex portions. The production method according to any one of claims 8 to 10, wherein the mask contains an oxide. The production method according to any one of claims 1 to 12, wherein the crystal growth plane is the m-plane or the r-plane. A crystal growth substrate having a crystal growth plane and a corundum structure, the first direction along the crystal growth plane and the first direction along the crystal growth plane and the first one. On the crystal growth substrate having different linear thermal expansion coefficients in the second direction which is perpendicular to the direction or substantially perpendicular to the direction, the main component of the crystal growth substrate is formed through the peel sacrificial layer. Is to form a crystalline oxide film containing different main components by crystal growth, and to peel off the crystalline oxide film and the crystal growth substrate from the second direction using the peeling sacrificial layer. Peeling method including.

Images