JP2022047720A - Method for growing crystal film and crystalline oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for growing a crystal film having a reduced in-plane rotation domain, a crystalline oxide film and its use.
A method of supplying a raw material to a substrate 1 provided with a mask 3 having a plurality of windows 4 to grow a crystal film, wherein the crystal film has a plurality of in-plane rotation domains. The plurality of windows 4 are arranged linearly, and the growth rate along the linear direction d1 of the window 4 of one of the in-plane rotation domains of the plurality of in-plane rotation domains is the other in-plane rotation domains. A method comprising forming a mask 3 on a substrate 1 to grow a crystal film so that the growth rate is greater than the growth rate along the linear direction of the group. The crystal film comprises a material selected from the group consisting of oxides, nitrides and oxynitrides, the width D _W of the window 4 is in the range 0.1-20 μm and the width D _M of the mask 3 is. The method, which is in the range of 5 to 500 μm and the width D _W of the window 4 is smaller than the width of the mask 3 _DM . A semiconductor device provided with a crystalline oxide film.
[Selection diagram] FIG. 11

Description

The present invention relates to a method for growing a high-quality crystal film having a reduced in-plane rotation domain, a crystalline oxide film, and an application using the same.

It has recently been reported that gamma oxide has a crystal structure of κ in addition to the five crystal structures of α, β, δ, ε and γ. Similar to β-Ga ₂ O ₃ and α-Ga ₂ O ₃ , κ-Ga ₂ O ₃ has a large bandgap of 4.9 eV and is promising as a next-generation power semiconductor material with high withstand voltage and low power consumption. (See, for example, Non-Patent Document 1). According to Non-Patent Document 1, since κ-Ga ₂ O ₃ has spontaneous polarization, high-concentration two-dimensional electrons are present at a hetero interface such as κ-Ga ₂ O ₃ / (Al _x Ga _1-x ) ₂ O ₃ . It has been pointed out that gas can be formed, and the realization of high-performance power devices using it is expected.

Epi-growth technology must be established for device application of κ-Ga ₂ O ₃ . However, since κ-Ga ₂ O ₃ is a metastable phase, there is no single crystal κ-Ga ₂ O ₃ substrate. Therefore, heteroepic growth on heterogeneous substrates has been attempted exclusively (see, for example, Non-Patent Documents 2-4). However, according to Non-Patent Documents 2 to 4, the epitaxy film of κ-Ga ₂ O ₃ was rotated by 120 ° in the (001) plane by any of the MOCVD method, the mist CVD method, and the HVPE method. It consists of three types of domains, and it has been reported that these domains are mixed at the nanoscale (5-10 nm).

When such a domain is mixed, the domain boundary scatters electrons, which may reduce the mobility or cause a current leak to reduce the withstand voltage of the power device. Therefore, it is desired to reduce such rotation domains and preferably realize a single crystal film having a single in-plane orientation.

Sung Beam Cho et al., Appl. Phys. Let. , 112, 162101, 2018 Ildiko Cora et al., CrystEngComm, 2017, 19, 1509 Hiroyuki Nishinaka et al., Jpn. J. Apple. Phys. , 57,115601,2018 Edited by Masaka Higashiwaki et al., Springer Sciences in Medicals Science 293, Gallium Oxide, pp. 223, section 11.3.1.

From the above, it is an object of the present invention to provide a method for growing a high-quality crystal film having a reduced in-plane rotation domain, a crystalline oxide film, and an application thereof.

As a result of diligent studies to achieve the above object, the present inventors have a rectangular crystal structure by using a method for growing a crystal film using ELO having a specific mask pattern, and have a surface more than the conventional one. We have succeeded in creating a crystalline film and / or a crystalline oxide film with a reduced internal rotation domain, and the obtained crystal film and / or the crystalline oxide film will be excellent in quality such as crystallinity. We have found that such a method for growing a crystal film can solve the above-mentioned conventional problems at once.

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

[1] A method of supplying a raw material to a substrate provided with a mask having a plurality of windows to grow a crystal film, wherein the crystal film has a plurality of in-plane rotation domains and the plurality of in-plane rotation domains. The window is linearly arranged and has a striped shape, and is along the linear direction of the window of the in-plane rotation domain group of one of the plurality of in-plane rotation domain groups. A method comprising forming the mask on the substrate and growing the crystal film such that the growth rate is higher than the growth rate along the linear direction of the other in-plane rotation domains. ..
[2] The method according to the above [1], wherein the crystal film contains a material selected from the group consisting of oxides, nitrides and oxynitrides.
[3] The oxides are κ- (Al _x In _y Ga _1-xy ) ₂ O ₃ , β- (Al _x In _y Ga _1-xy ) ₂ O ₃ and γ- (Al). _x In _y Ga _1-xy ) ₂ O ₃ (where x, y and z satisfy 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) are selected from the group. The method according to the above [2].
[4] The method according to any one of [1] to [3] above, wherein a method selected from the group consisting of an HVPE method, a mist CVD method and a MOCVD method is used for the growth of the crystal film.
[5] The method according to any one of [1] to [4] above, wherein the width of the window is in the range of 0.1 μm or more and 20 μm or less.
[6] The method according to any one of [1] to [5] above, wherein the width of the mask is in the range of 5 μm or more and 500 μm or less.
[7] The method according to any one of [1] to [6], wherein the width of the window is smaller than the width of the mask.
[8] A method of supplying a raw material to a substrate provided with a mask having a plurality of windows to grow a crystal film, wherein the crystal film has a plurality of in-plane rotation domains and the plurality of in-plane rotation domains. The window is linearly arranged and has a dot-like shape, and is along the linear direction of the window of the in-plane rotation domain group of one of the plurality of in-plane rotation domain groups. Including forming the mask on the substrate and growing the crystal film so that the growth rate is higher than the growth rate along the linear direction of the other in-plane rotation domains, further. Assuming that the distance between the centers of two adjacent dots in the linear direction of the window is p, the distance q between the centers of the two adjacent dots in the direction perpendicular to the linear direction of the window is p. A method that satisfies × 2 / √3 or more and 500 μm or less.
[9] The method according to the above [8], wherein each of the plurality of windows has a circular shape and / or a polygonal shape.
[10] The circle and / or the polygon is a substantially perfect circle and / or a substantially regular polygon, and the substantially perfect circle and / or the substantially regular in a direction parallel to the linear direction of the window. Assuming that the center-to-center distance of the polygon is p, the center-to-center distance q of the substantially perfect circle and / or the substantially regular polygon in the direction perpendicular to the linear direction of the window is p × 2 / √3. The method according to the above [9], which satisfies the above 500 μm or less.
[11] The diameter of the substantially perfect circle and / or the substantially regular polygon is within the range of 0.1 μm or more and 10 μm or less, and the substantially perfect circle and / or the direction parallel to the linear direction of the window. The method according to [10] above, wherein the distance between the centers of the substantially regular polygon is within the range of 0.3 μm or more and 25 μm or less.
[12] The method according to any one of [1] to [11] above, wherein the mask comprises a material selected from the group consisting of oxides, nitrides, oxynitrides, and metals.
[13] The method according to any one of [1] to [12], wherein the mask is made of an amorphous material.
[14] The method according to any one of [1] to [13], wherein the substrate further includes a buffer layer between the mask and the substrate.
[15] The method according to [14], further comprising growing the crystal film on the buffer layer.
[16] The mask as the first mask is formed on the substrate, and the crystal film as the first crystal film is grown, and then the second mask is formed on the first crystal film. Including forming and further growing a second crystal film, the second mask has a plurality of windows arranged linearly, and the second mask is the second mask. The method according to any one of [1] to [15], wherein the plurality of windows of the first mask and the plurality of windows of the first mask are formed on the first crystal film so as not to overlap each other.
[17] The crystal film is κ- (Al _x In _y Ga _1-xy ) ₂ O ₃ (where x, y and z are 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦. x + y ≦ 1),
The substrate is a substrate selected from the group consisting of a sapphire substrate, a GaN substrate, an AlN substrate, a 6H-SiC substrate and a 4H-SiC substrate.
The mask is formed so that the angle formed by the linear direction of the window and the [11-20] direction of the substrate is -5 ° or more and 5 ° or less. The method described in either.
[18] The method according to the above [17], wherein the surface index of the substrate is a (0001) surface.
[19] A crystalline oxide film having a rectangular crystal structure and containing at least one or more metals selected from aluminum, gallium and indium, which is rotated in the crystalline oxide film. A crystalline oxide film characterized by a domain content of 30% or less.
[20] The main component of the crystalline oxide film is (001) plane-oriented κ- (Al _x In _y Ga _1-xy ) ₂ O ₃ (where x, y and z are 0 ≦). The crystalline oxide film according to the above [19], which satisfies x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1).
[21] The semiconductor device provided with the crystalline oxide film according to claim 19 or 20.
[22] A semiconductor layer provided on a crystal substrate having a crystal structure including an [11-20] axis or a [10-10] axis, and a first arranged on the first surface side of the semiconductor layer, respectively. A semiconductor element having at least one of the above electrodes and a second electrode, and configured such that a current flows in the first direction from the first electrode to the second electrode in the semiconductor layer. A semiconductor element in which the semiconductor layer has a crystal structure different from that of the crystal substrate and the first direction is parallel to the [11-20] axis or the [10-10] axis of the crystal substrate. ..
[23] The semiconductor device according to the above [22], wherein the crystal substrate has a corundum structure.
[24] The semiconductor element according to any one of [21] to [23], wherein the semiconductor element is selected from the group consisting of a diode, an ultraviolet ray detecting element, and a transistor.
[25] The semiconductor device according to the above [23] or [24], which is a high electron mobility transistor (HEMT).

According to the method for growing a crystal film of the present invention, only a single in-plane rotation domain group can be preferentially grown. As a result, it is possible to provide a high-quality crystal film and / or a crystalline oxide film with a reduced in-plane rotation domain.

It is a figure which shows the flowchart which grows a crystal film in embodiment of this invention. It is a figure which shows the flowchart which grows a crystal film in embodiment of this invention. It is a figure which shows typically the process of forming a buffer layer and a mask on a substrate which concerns on embodiment of this invention. It is a schematic diagram which shows the crystal film which has a plurality of in-plane rotation domains to which the method of growing a crystal film which concerns on embodiment of this invention is applied. It is a schematic diagram for demonstrating the difference in the crystal film obtained by the difference in the growth rate of a plurality of in-plane rotation domain groups in the embodiment of the present invention. It is a schematic diagram which shows the exemplary mask in the growth method which concerns on embodiment of this invention. It is a schematic diagram which shows the transistor provided with the crystal film which concerns on embodiment of this invention. It is a schematic diagram which shows the ultraviolet ray detecting element provided with the crystal film which concerns on embodiment of this invention. It is a schematic diagram which shows the high electron mobility transistor (HEMT) provided with the crystal film which concerns on embodiment of this invention. It is a figure explaining the halide vapor deposition (HVPE) apparatus which concerns on embodiment of this invention. It is a figure which shows typically the substrate in which the mask is formed through the buffer layer in the embodiment of this invention. It is a figure which shows typically the substrate in which the mask is formed through the buffer layer in the embodiment of this invention. It is a figure which shows typically the substrate in which the mask is formed through the buffer layer in the comparative example 2. It is a figure which shows the SEM observation result after the film formation in Example 1. FIG. It is a figure which shows the observation result after the film formation in Example 1. FIG. 15 (A) is a TEM image, and FIGS. 15 (B) and 15 (C) are diagrams showing a SAED (Selected Area Electron Diffraction) pattern. It is a figure which shows the result of the XRD122 diffraction φ scan in Example 1. FIG. It is a figure which shows the result of the EBSD (Electron Backscatter Diffraction Patterns) analysis in Example 1. FIG. It is a figure which shows the SEM observation result after the film formation in the comparative example 1. FIG. It is a figure which shows the result of the XRD122 diffraction φ scan in the comparative example 1. FIG. It is a figure which shows the result of the EBSD (Electron Backscatter Diffraction Patterns) analysis in the comparative example 1. FIG. It is a figure which shows the SEM observation result in Example 2. FIG. (A) shows a bird's-eye view after 5 minutes, (b) shows a bird's-eye view after 15 minutes, and (c) shows a bird's-eye view after 2 hours. It is a figure which shows the result of the XRD122 diffraction φ scan in Example 2. FIG. It is a figure which shows the result of the EBSD (Electron Backscatter Diffraction Patterns) analysis in Example 2. FIG. It is a figure which shows the SEM observation result after the film formation in the comparative example 2. FIG. It is a figure which shows the result of the EBSD (Electron Backscatter Diffraction Patterns) analysis in the comparative example 2. FIG. It is a figure which shows the result of the XRD122 diffraction φ scan in the comparative example 3. FIG.

The method for growing a crystal film according to an embodiment of the present invention is a method in which a raw material is supplied onto a substrate provided with a mask having a plurality of windows to grow the crystal film, and the crystal film is rotated in a plurality of planes. The plurality of windows have a domain group, and the plurality of windows are arranged linearly and have a striped shape, and the plurality of windows have an in-plane rotation domain of one of the in-plane rotation domain groups. The mask was formed on the substrate so that the growth rate of the window of the group along the linear direction was higher than the growth rate of the other in-plane rotation domain group along the linear direction. It is characterized by including growing the crystal film. Further, the method for growing a crystal film in the embodiment of the present invention is a method in which a raw material is supplied to a substrate provided with a mask having a plurality of windows to grow the crystal film, and the crystal film is in-plane. It has a rotation domain group, and the plurality of windows are arranged linearly and have a dot-like shape, and one of the plurality of in-plane rotation domain groups is an in-plane rotation domain. The mask was formed on the substrate so that the growth rate of the window of the group along the linear direction was higher than the growth rate of the other in-plane rotation domain group along the linear direction. Including the growth of the crystal film, and further assuming that the distance between the centers of two adjacent dots in the linear direction of the plurality of windows is p, it is perpendicular to the linear direction of the plurality of windows. The distance q between the centers of two adjacent dots in the above direction is characterized by satisfying p × 2 / √3 or more and 500 μm or less.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Of course, it is also possible to combine a plurality of embodiments according to the present invention or to apply some components to other embodiments, and such a component also belongs to the embodiment of the present invention.

FIG. 1 is a diagram showing an example of a flowchart for growing a crystal film in an embodiment of the present invention. In step S110, a buffer layer is formed on the substrate. In an embodiment of the invention, the mask may be formed directly on the substrate (without interposing the buffer layer) and then the crystal film may be grown, or the mask may be formed on the substrate via the buffer layer, and then. The crystal film may be grown. In an embodiment of the present invention, as shown in step S110 of FIG. 1, it is preferable to form the mask on the substrate via a buffer layer, and then grow the crystal film on the buffer layer.

(Buffer layer)
The constituent material of the buffer layer is not particularly limited and may be a known material. Examples of the constituent material of the buffer layer include oxides, nitrides, oxynitrides and the like. Examples of the oxide include aluminum (Al), gallium (Ga), indium (In), iron (Fe), chromium (Cr), vanadium (V), titanium (Ti), rhodium (Rh), and iridium ( Ir), cobalt (Co), zinc (Zn), tin (Sn), zirconium (Zr), silicon (Si), tungsten (W), tantalum (Ta), hafnium (Hf), scandium (Sc), ittrium ( Examples thereof include metal oxides containing one or more kinds of metals selected from Y). Examples of the nitride include nitrides containing one or more metals selected from aluminum (Al), gallium (Ga) and indium (In). More specifically, examples of the nitride include gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), and mixed crystals thereof. Examples of the oxynitride include SiON, AlON, TiON and the like. In the embodiment of the present invention, the buffer layer preferably contains an oxide, more preferably titanium oxide. By using such a preferable buffer layer, the crystal film having an orthorhombic crystal structure (for example, a κ type crystal structure) having excellent crystal quality can be grown more satisfactorily. The method for forming the buffer layer is not particularly limited and may be a known method. Examples of the method for forming the buffer layer include a vacuum vapor deposition method, a CVD method, a sputtering method, and the like.

Then, in step S120, a mask having a plurality of windows arranged linearly is formed on the substrate on which the buffer layer is formed on the surface obtained in step S110, and on the obtained substrate, the mask is formed. Form a crystal film.

(substrate)
The substrate is provided with a mask having a plurality of windows, and is not particularly limited as long as it serves as a support for the crystal film. Examples of the substrate include a substrate selected from the group consisting of a sapphire substrate, a GaN substrate, an AlN substrate, a 6H-SiC substrate, and a 4H-SiC substrate. In the embodiment of the present invention, it is preferable that the substrate is a crystalline substrate. The crystal substrate is not particularly limited as long as it is a substrate containing a crystal as a main component, and may be a known substrate. It may be an insulator substrate, a conductive substrate, or a semiconductor substrate. It may be a single crystal substrate or a polycrystalline substrate. The crystal substrate includes, for example, a substrate containing a crystal having a corundum structure as a main component, a substrate containing a crystal having a β-galia structure as a main component, or a substrate containing a crystal having a hexagonal structure as a main component. And so on. In the embodiment of the present invention, it is preferable that the crystal substrate has a crystal structure including a [11-20] axis (a axis) or a [10-10] axis (m axis). Examples of the crystal structure including the [11-20] axis (a axis) or the [10-10] axis (m axis) include a corundum structure, a hexagonal structure (for example, a ε-type structure, a wurtzite-type structure, etc.) and the like. Can be mentioned. 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. The surface index of the main surface of the substrate is not particularly limited, but in the embodiment of the present invention, it is preferably the (0001) surface (c surface).

Examples of the substrate containing a crystal having a corundum structure as a main component include a sapphire substrate and an α-type gallium oxide substrate. Examples of the substrate containing the crystal having a β-Galia 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 . .. As the mixed crystal substrate containing β-Ga ₂ O ₃ and Al ₂ O ₃ , for example, a mixed crystal substrate containing Al ₂ O ₃ in an atomic ratio of more than 0% and 60% or less is preferable. Is mentioned as. Examples of the substrate having the hexagonal structure include a SiC substrate, a ZnO substrate, a GaN substrate, an AlN substrate, and the like. Examples of other crystal substrates include Si substrates.

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

The mask has a plurality of windows, and is not particularly limited as long as the plurality of windows are linearly arranged. The constituent material of the mask is also not particularly limited and may be a known material. It may be an insulator material, a conductor material, or a semiconductor material. Further, the constituent material may be amorphous, single crystal, or polycrystal. Examples of the constituent material of the convex portion include oxides such as Si, Ge, Ti, Zr, Hf, Ta, Sn, and Al, 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, ruthenium and other precious metals, etc.). In the embodiment of the present invention, it is preferable that the constituent material of the mask is at least one selected from oxides, nitrides or oxynitrides and metals. Further, in the embodiment of the present invention, the constituent material of the mask may be an amorphous material. Examples of the oxide, nitride or oxynitride include oxides such as Si, Ge, Ti, Zr, Hf, Ta and Sn, nitrides or oxynitrides. Examples of the metal include precious metals such as platinum, gold, silver, palladium, rhodium, iridium, and ruthenium.

Further, the shape of the plurality of windows arranged linearly is not particularly limited, and may be striped or dot-shaped. In the embodiment of the present invention, when the shape of the plurality of windows is dot-shaped, the distance between the centers of two adjacent dots in the linear direction of the plurality of windows is usually p, and the plurality of windows are described. The distance between the centers of two adjacent dots in the direction perpendicular to the linear direction of is q, which satisfies the condition of p × 2 / √3 or more and 500 μm or less. When the shape of the plurality of windows is dot-shaped, a single in-plane oriented domain can be preferentially grown by arranging such dimensions. The surface shape of the dots is not particularly limited, and may be a circular shape or a polygonal shape (for example, a triangle, a quadrangle, a pentagon, a hexagon, etc.). In the embodiment of the present invention, it is preferable that the shape of the plurality of windows is striped because a crystal film having a single in-plane orientation can be obtained better and more easily. Further, in the embodiment of the present invention, when the shape of the plurality of windows is a dot shape, it is preferable that the shape of the plurality of windows is a substantially perfect circle and / or a substantially regular polygon. In this case, where p is the distance between the centers of the adjacent substantially perfect circles and / or the adjacent substantially regular polygons in the direction parallel to the linear direction of the window, the linear direction of the window. The distance q between the centers of the adjacent substantially perfect circles and / or the adjacent substantially regular polygons in the direction perpendicular to the center satisfies p × 2 / √3 or more and 500 μm or less. Furthermore, in the embodiment of the present invention, the diameter of the substantially perfect circle and / or the substantially regular polygon is within the range of 0.1 μm or more and 10 μm or less, and the direction parallel to the linear direction of the window. The distance between the centers of the substantially perfect circle and / or the substantially regular polygon in the above is preferably in the range of 0.3 μm or more and 25 μm or less. FIG. 6 shows a mask and a top view of the windows as an example of a mask in which a plurality of windows are arranged linearly. 6 (A) is a stripe shape, FIG. 6 (B) is a dot shape (circular shape), FIG. 6 (C) is a dot shape (triangular shape), and FIG. 6 (D) is a dot shape (square shape). Shows.

The mask forming means may be a known means, 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). Be done. Further, 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, more preferably 0.5 μm to 50 μm, and 0.5 μm to 10 μm ”. Most preferably.

FIG. 3 is a diagram schematically showing a manufacturing process of forming a mask on a substrate via a buffer layer in an embodiment of the present invention. FIG. 3A shows the substrate 1. The buffer layer 2 is formed on the substrate 1 of FIG. 3A by a known method to obtain the laminate of FIG. 3B. Then, a mask layer is formed on the obtained laminate (b) by a known film forming method (for example, vacuum vapor deposition method, CVD method or sputtering method), and then processed by a known patterning processing method. Therefore, the masks 3 arranged linearly are formed to obtain the laminated body of FIG. 3 (c). Examples of the patterning processing method include known patterning processing methods such as photolithography, electron beam lithography, laser patterning, and subsequent etching (for example, dry etching or wet etching).

FIG. 11 is a perspective view schematically showing a substrate on which a mask is formed on the surface via a buffer layer. The substrate 1 of FIG. 11 has a mask 3 having a plurality of striped windows formed on the surface thereof via a buffer layer 2, and the plurality of windows 4 of the mask are arranged linearly. In the embodiment of the present invention, when a crystal film having a rectangular structure (for example, a κ type crystal structure) is formed as the crystal film, for example, a c-plane sapphire substrate is used as the substrate, and the plurality of the crystals are used. By forming the mask so that the linear direction d1 of the window 4 is parallel to the [11-20] axis (a-axis) direction of the sapphire substrate, a plurality of in-plane rotation domains of the crystal film can be formed. The growth rate of one of the in-plane rotation domain groups along the linear direction of the window can be made higher than the growth rate of the other in-plane rotation domain group along the linear direction. .. In the embodiment of the present invention, when the substrate is a substrate selected from the group consisting of a sapphire substrate, a GaN substrate, an AlN substrate, a 6H-SiC substrate and a 4H-SiC substrate, the linear shape of the window 4 is used. The angle formed by the direction d1 and the [11-20] direction of the substrate is preferably in the range of −5 ° or more and 5 ° or less.

The width D _W of the window is not particularly limited as long as the object of the present invention is not impaired. In the embodiment of the present invention, the width of the window is preferably in the range of 0.1 μm or more and 20 μm or less, more preferably in the range of 1 μm or more and 15 μm or less, and more preferably in the range of 3 μm or more and 7 μm or less. Is most preferable. Further, the width _DM of the mask is not particularly limited as long as the object of the present invention is not impaired. In the embodiment of the present invention, the width _DM of the mask is preferably in the range of 5 μm or more and 500 μm or less, more preferably in the range of 5 μm or more and 200 μm or less, and more preferably in the range of 10 μm or more and 50 μm or less. Is the most preferable. The width D _W of the window is preferably smaller than the width D _M of the mask. By setting the width of the window and the width of the mask to values within such a preferable range, the quality of the crystal film can be further improved.

FIG. 12 is a perspective view schematically showing a substrate in which a mask is formed on the surface via a buffer layer in another embodiment of the present invention. The substrate 1 of FIG. 12 has a mask 3 having a plurality of dot-shaped (circular) windows formed on the surface thereof via a buffer layer 2, and the plurality of windows 4 of the mask are arranged linearly. There is. In the embodiment of the present invention, when a crystal film having a rectangular structure (for example, a κ type crystal structure) is formed as the crystal film, for example, a c-plane sapphire substrate is used as the substrate, and the plurality of the crystals are used. By forming the mask so that the linear direction of the window 4 is parallel to the [11-20] axis (a-axis) direction of the sapphire substrate, the crystal film has a plurality of in-plane rotation domains. The growth rate of one in-plane rotation domain group along the linear direction of the window can be made higher than the growth rate of the other in-plane rotation domain group along the linear direction. In the embodiment of the present invention, where p is the center-to-center distance in the direction parallel to the linear direction of the window 4, the center-to-center distance q in the direction perpendicular to the linear direction of the window 4 is. Satisfy "p × 2 / √3 ≦ q ≦ 500 μm". Further, in the embodiment of the present invention, the diameter R of the window 4 is within the range of 0.1 μm or more and 10 μm or less, and the center-to-center distance p in the direction parallel to the linear direction of the window 4 is 0.3 μm. It is preferably within the range of 25 μm or more. By keeping the width of the window and the width of the mask within such a preferable range, the quality of the crystal film can be further improved.

(Crystal film)
The crystal film is not particularly limited as long as it has a plurality of in-plane rotation domains. Here, the in-plane rotation domain group means, for example, three types of domains rotated by 120 ° in the (001) plane when the crystal film is the (001) plane κ-Ga ₂ O ₃ . .. In the embodiment of the present invention, it is preferable that the crystal film contains at least one selected from the group consisting of oxides, nitrides and oxynitrides as a main component. Examples of the oxide include aluminum (Al), gallium (Ga), indium (In), iron (Fe), chromium (Cr), vanadium (V), titanium (Ti), rhodium (Rh), and iridium ( Ir), cobalt (Co), zinc (Zn), tin (Sn), zirconium (Zr), silicon (Si), tungsten (W), tantalum (Ta), hafnium (Hf), scandium (Sc), ittrium ( Examples thereof include metal oxides containing one or more kinds of metals selected from Y). Examples of the nitride include nitrides containing one or more metals selected from aluminum (Al), gallium (Ga) and indium (In). More specifically, examples of the nitride include gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), and mixed crystals thereof. Examples of the oxynitride include SiON, AlON, TiON and the like.

In the embodiment of the present invention, it is preferable that the crystal film contains an oxide. Further, in the embodiment of the present invention, the oxide is κ- (Al _x In _y Ga _1-xy ) ₂ O ₃ , β- (Al _x In _y Ga _1-x-y ) ₂ O ₃ , And γ- (Al _x In _y Ga _1-xy ) ₂ O ₃ (where x, y and z satisfy 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1 ) Is preferably at least one selected from the group consisting of. The crystal structure of the oxide is not particularly limited as long as the object of the present invention is not impaired. The crystal structure of the oxide includes, for example, a corundum structure, a β-galia structure, a hexagonal structure (for example, ε-type structure, etc.), a rectangular crystal structure (for example, a κ-type structure, etc.), a cubic structure, or a rectangular structure. And so on. In the embodiment of the present invention, the crystal structure of the oxide is preferably a corundum structure, a hexagonal structure or a rectangular structure, preferably a rectangular structure, and most preferably a κ type structure.

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

(material)
The raw material is not particularly limited as long as it contains a substance that is a material for the crystal film, and may contain an inorganic material or an organic material. In the embodiment of the present invention, it is preferable that the raw material contains a metal. Examples of the metal include gallium (Ga), iridium (Ir), indium (In), rhodium (Rh), aluminum (Al), gold (Au), silver (Ag), platinum (Pt), and copper (Cu). ), Iron (Fe), Manganese (Mn), Nickel (Ni), Palladium (Pd), Cobalt (Co), Ruthenium (Ru), Chromium (Cr), Molybdenum (Mo), Tungsten (W), Tantal (Ta) ), Zinc (Zn), Lead (Pb), Ruthenium (Re), Titanium (Ti), Tin (Sn), Gallium (Ga), Magnesium (Mg), Calcium (Ca) and Zirconium (Zr) 1 Seeds or two or more metals and the like.

The method for growing the crystal film is not particularly limited and may be a known method. Examples of the method for growing the crystal film include an HVPE method, a mist CVD method, a MOCVD method, and the like. In the embodiment of the present invention, it is preferable to grow the crystal film by using the HVPE method.

Hereinafter, embodiments of the present invention will be described in more detail by using the HVPE method as a method for growing the crystal film and exemplifying a case where κ-Ga ₂ O ₃ is grown as the crystal film. Specifically, in the HVPE method, for example, a metal source containing a metal is gasified into a metal halide gas, and then the metal halide gas and the oxygen-containing raw material gas are supplied to the crystal substrate in the reaction chamber. It is preferable to form a film. Further, in the embodiment of the present invention, it is also preferable to supply the reactive gas onto the crystal substrate and perform the film formation 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 embodiment of 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 preferably. 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. , It is preferable that the metal source is a liquid.

The gasification means is not particularly limited and may be a known means as long as the object of the present invention is not impaired. In the embodiment of the present invention, it is preferable that the gasification means is 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 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 an embodiment of the present invention, the gasification is carried out by supplying a halogen or hydrogen halide as a halogenating agent to the metal source, and the metal source and the halogen or hydrogen halide are vaporized at the vaporization temperature of the metal halide. It is preferable to carry out the reaction by reacting as described above to obtain a metal halide. The halogenation reaction temperature is not particularly limited, but in the embodiment of the present invention, for example, when the metal source is gallium and the halogenating agent is HCl, 900 ° C. or lower is preferable, and 700. The temperature is more preferably 40 ° C or lower, and most preferably 400 ° C to 700 ° C. The metal halide gas is not particularly limited as long as it is a gas containing a metal halide of the metal source. Examples of the metal halide gas include halides of the metal (fluoride, chloride, bromide, iodide, etc.).

In the embodiment of the present invention, the metal source containing a metal is gasified to obtain a metal halide gas, and then the metal halide 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. The formation temperature of the crystal layer is not particularly limited, but in the embodiment of the present invention, for example, when the metal source is gallium and the halogenating agent is HCl, 900 ° C. or lower is preferable. It is more preferably 700 ° C. or lower, and most preferably 400 ° C. to 700 ° C. The oxygen-containing raw material gas may be, for example, one or more gas selected from O ₂ gas, CO ₂ gas, NO gas, NO ₂ gas, N ₂ O gas, H ₂ O gas or O ₃ gas. be. In the embodiment of the present invention, the oxygen-containing raw material gas is preferably one or more gas selected from the group consisting of O ₂ , H ₂ O and N ₂ O, and preferably contains O ₂ . Is more preferable. The reactive gas is usually a reactive gas different from the metal halide 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, hydrofluoric acid gas, hydrochloric acid gas, hydrogen bromide, etc.). Gas or 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 halide 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 halide gas is not particularly limited, but in the embodiment of the present invention, it is preferably 0.5 Pa to 1 kPa, 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 halide 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, preferably 0.2 to 3 times the partial pressure of the metal halide gas. 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. It is more preferably 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 onto the substrate together with the reactive gas.

In the embodiment of the present invention, the mask as the first mask is formed on the substrate, and the crystal film as the first crystal film is grown, and then the first crystal film is formed as step S130. It is also preferable to form a second mask on the crystal film and further grow the second crystal film. By further growing the second crystal film in this way, it is possible to obtain a second crystal film having a reduced in-plane rotation domain as compared with the first crystal film. In this case, the second mask has a plurality of windows arranged linearly like the first mask, and the plurality of windows of the second mask and the first mask. It is preferable that the mask is formed so as not to overlap with a plurality of windows of the mask.

FIG. 2 is a diagram showing another suitable example of the flowchart for growing a crystal film in the embodiment of the present invention. The growth method shown in FIG. 2 is different from the growth method shown in FIG. 1 in that a step of growing a flat film on the buffer layer is provided as step S210 between steps S110 and S120. The material of the flat film is not particularly limited, but in the embodiment of the present invention, it is preferable that the material is the same as the material of the crystal film. Further, the method for forming the flat film may be the same as the method for forming the crystal film.

In an embodiment of the present invention, the crystal film has a plurality of in-plane rotation domain groups, and the line of the window of the in-plane rotation domain group of one of the plurality of in-plane rotation domain groups. The mask is formed on the substrate so that the growth rate along the linear direction is higher than the growth rate along the linear direction of the other in-plane rotation domain groups. The method of forming the mask and growing the crystal film in this way will be described in more detail below with reference to the drawings.

FIG. 4 is a surface view schematically showing a crystal film having a plurality of in-plane rotation domains to which the method for growing a crystal film according to the embodiment of the present invention is applied. FIG. 4 schematically shows how the crystal film grown from the window 310 grows laterally on the mask when the crystal film is grown on a substrate having a striped mask. For the sake of simplicity, the crystal film growing on the window 310 is not shown. The crystal film typically contains a plurality of in-plane rotation domains 320a, 320b, and 320c as it grows from the window 310 and grows laterally when grown using ELO, as shown in FIG. In FIG. 4, for convenience, a plurality of in-plane rotation domains 320a, 320b, and 320c are shown to grow evenly in a specific order, but the crystal film obtained by the conventional method for growing a crystal film is a crystal film. Usually, these three types of in-plane rotation domains are distributed in random size and order.

FIG. 5 is a schematic diagram for explaining the difference in the crystal film obtained by the difference in the growth rate of the plurality of in-plane rotation domain groups in the embodiment of the present invention. In FIG. 5A, the growth rate of the in-plane rotation domain 320b along the linear direction (hereinafter, also simply referred to as “growth rate”) is higher than the growth rate of the in-plane rotation domain 320c, and the in-plane rotation The case where the growth rate of the domain 320a is higher than the growth rate of the in-plane rotation domain 320b is shown. Further, FIG. 5B shows a case where the in-plane rotation domain 320b and the in-plane rotation domain 320c have the same growth rate, and the in-plane rotation domain 320a has a higher growth rate than the in-plane rotation domains 320b and 320c. show. As shown in FIGS. 5 (A) and 5 (B), the growth rate of one in-plane rotation domain group among the plurality of in-plane rotation domain groups is higher than that of the other in-plane rotation domain groups. In some cases, it is possible to obtain a crystal film having a single in-plane orientation in the lateral growth portion. This is the finding that the present inventors actually obtained for the first time by an experiment, as shown in Examples described later. On the other hand, FIG. 5C shows a case where the growth rates of the in-plane rotation domains 320a, 320b and 320c are all equal. FIG. 5D shows a case where the growth rate of the in-plane rotation domain 320b is higher than the growth rate of the in-plane rotation domain 320a, and the growth rate of the in-plane rotation domain 320b is equal to the growth rate of the in-plane rotation domain 320c. Is shown. In the case of FIGS. 5 (C) and 5 (D), it becomes difficult to obtain a crystal film having a single in-plane orientation.

According to the growth method according to the above-described embodiment of the present invention, for example, a crystal film having a rectangular crystal structure and containing at least one or two or more metals selected from aluminum, gallium and indium (hereinafter referred to as “crystallinity”). , Also referred to as “crystalline oxide film”), wherein the crystalline oxide film is characterized in that the content of the rotational domain in the crystalline oxide film is 30% or less. Further, according to the above-mentioned suitable growth method, a crystalline oxide film having a content of the rotational domain of 20% or less can be obtained. Here, the content of the rotation domain can be calculated from, for example, an image of the result of EBSD (Electron backscattered diffraction) measured from the surface side of the crystal film. In the embodiment of the present invention, the main component of the crystalline oxide film is preferably a crystalline oxide having a rectangular structure, and (001) plane-oriented κ- (Al _x In _y Ga _1- ). _xy ) ₂ O ₃ (where x, y and z satisfy 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) is more preferable. Here, the "main component" means, for example, when the crystalline oxide film contains κ-Ga ₂ O ₃ as a main component, κ-Ga ₂ O ₃ is an atomic ratio of all the components of the crystal film. On the other hand, it means that it is preferably contained in an amount of 50% or more, more preferably 70% or more, still more preferably 90% or more, and may be 100% or more.

Further, the crystalline oxide film is particularly a semiconductor layer provided on a crystal substrate having a crystal structure including a [11-20] axis (a axis) or a [10-10] axis (m axis). It has at least a first electrode and a second electrode arranged on the first surface side of the semiconductor layer, respectively, and in the semiconductor layer, from the first electrode to the second electrode. A semiconductor element configured such that a current flows in a first direction toward which the semiconductor layer has a crystal structure different from that of the crystal substrate, and the first direction is the a-axis of the crystal substrate. It can be suitably used as the semiconductor layer in a semiconductor element parallel to the direction or the m-axis direction, and the semiconductor element thus obtained is also included in one of the embodiments of the present invention. In the embodiment of the present invention, it is preferable that the crystal substrate has a corundum structure. Here, the parallel to the [11-20] axis (a axis) or the [10-10] axis (m axis) does not have to be completely parallel, and may be slightly deviated from it. It means that it is good (for example, the angle formed by the first direction and the a-axis or the m-axis may be larger than 0 ° and 10 ° or less).

The crystalline film or crystalline oxide film according to the embodiment of the present invention can be particularly preferably used for a semiconductor device, and is particularly useful for a power device. Examples of the semiconductor element formed by using the crystal film or the crystalline oxide film include a semiconductor element selected from the group consisting of a diode, an ultraviolet ray detecting element, and a transistor, and more specifically, for example. , MIS, HEMT, MOS and other transistors and TFTs, shotkey barrier diodes using semiconductor-metal junctions, PN or PIN diodes combined with other P layers, and light emitting and receiving elements. In the embodiment of the present invention, the semiconductor device is preferably HEMT. Further, in the embodiment of the present invention, the crystal film or the crystalline oxide film may be used as it is for a semiconductor device or the like, or the substrate and / or the mask may be peeled off by a known means. , It may be applied to a semiconductor element or the like.

FIG. 7 is a schematic view showing a transistor provided with a crystal film or a crystalline oxide film (hereinafter, also simply referred to as “crystal film”) according to the embodiment of the present invention. The transistor 900 includes a crystal film 910 according to at least an embodiment of the present invention, a source 920 formed on a part of one main surface of the crystal film 910, a drain 930 formed so as to face the source 920, and a source. It includes a channel 940 formed between the 920 and the drain 930, an insulating film 950 formed on the channel 940, and a gate electrode 960 formed on the insulating film 950.

The crystal film 910 is preferably a single crystal film containing κ-Ga ₂ O ₃ or a mixed crystal thereof according to the embodiment of the present invention. In the embodiment of the present invention, it is preferable that the crystal film 910 exhibits n-type conductivity. The thickness of the crystal film is, for example, 0.1 μm or more and 10 μm or less.

The source 920 includes an n + type region 970a in which a dopant element is injected into a part of the crystal film 910 at a high concentration, and an electrode 980a formed on the n + region 970a. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, niobium, or two or more of these elements. The carrier concentration of the n + type region 970a is, for example, in the range of 1 × 10 ¹⁵ / cm ³ or more and 1 × 10 ²⁰ / cm ³ or less. The n + type region 970a may be formed not only by injection but also by, for example, a known patterning method and a known film forming method. Examples of the electrode 980a include a metal material selected from the group consisting of Al, Ti, Pt, Ru, Au and alloys thereof.

The drain 430 includes an n + type region 970b in which a dopant element is injected into a part of the crystal film 910 at a high concentration, and an electrode 980b formed on the n + type region 970b. Similar to the n + type region 970a, examples of the dopan include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, niobium, or two or more of these elements. The carrier concentration of the n + type region 970b is, for example, in the range of 1 × 10 ¹⁵ / cm ³ or more and 1 × 10 ²⁰ / cm ³ or less. The n + type region 970b may be formed not only by injection but also by, for example, a known patterning method and a known film forming method. Examples of the electrode 980b include a metal material selected from the group consisting of Al, Ti, Pt, Ru, Au and alloys thereof.

The insulating film 950 is an insulating material selected from the group consisting of Al ₂ O ₃ , SiO ₂ , HfO ₂ , SiN, and SiON. The gate electrode 906 is, for example, a metal material selected from the group consisting of Al, Ti, Pt, Ru, Au, and alloys thereof. The thickness of the insulating film 950 is, for example, 1 nm or more and 100 nm or less.

A method for manufacturing such a transistor 900 will be described. The transistor 900 is manufactured by an existing LSI manufacturing process. For example, the transistor 900 forms n + regions 970a and 970b by ion implantation on the α _- Ga ₂ O3 single crystal 910 obtained in the first embodiment by ion implantation, and then a vapor phase epitaxial growth method. An insulating film 950 is formed using existing growth techniques such as liquid phase epitaxial growth method, halide vapor deposition method, metalorganic chemical vapor deposition (MOCVD), and then existing electrodes such as vacuum deposition and sputtering. It is manufactured by forming the electrodes 980a and 980b and the gate electrode 460 by a forming technique.

Although not shown, a diode can be manufactured by forming a pn junction (which may be a heterojunction) using the crystal film according to the embodiment of the present invention as an n-type semiconductor.

FIG. 8 is a schematic view showing an ultraviolet detection element provided with a crystal film according to an embodiment of the present invention.

As shown in FIGS. 8A and 8B, the ultraviolet detection elements 1000a and 1000b include at least the crystal film 1010 of the present invention, the shotkey electrode 1020 formed on the crystal film 1010, and the crystal film 1010. It is provided with an ohmic electrode 1030 formed in. Specifically, according to the ultraviolet detection element 1000a of FIG. 8A, the Schottky electrode 1020 is formed on one main surface of the α-Ga ₂ O ₃ single crystal 1010, and the ohmic electrode 1030 is a crystal film. It is formed on the other main surface (back surface in FIG. 8) of 1010. On the other hand, according to the ultraviolet detection element 1000b of FIG. 8B, since the crystal film 1010 is located on the substrate (for example, sapphire substrate or the like) 1040 as described later, the Schottky electrode 1020 and the ohmic electrode 1030 are Both are formed on the same main surface of the crystal film 1010.

The crystal film 1010 is preferably a single crystal film containing κ-Ga ₂ O ₃ or a mixed crystal thereof according to the embodiment of the present invention. In the embodiment of the present invention, it is preferable that the crystal film 910 exhibits n-type conductivity. The thickness of the crystal film is, for example, 0.1 μm or more and 10 μm or less.

The Schottky electrode 1020 may be a metal material selected from the group consisting of Ni, Pt, Au, and alloys thereof. The ohmic electrode 1030 can be a metallic material selected from the group consisting of Ti, In, and alloys thereof.

A method for manufacturing such an ultraviolet detection element 1000 will be described. The ultraviolet detection element 1000 is manufactured by an existing large-scale integrated circuit (LSI) manufacturing process. For example, the ultraviolet detection element 1000 has a shotkey electrode 1020 and an ohmic electrode 1030 on the main surface and the back surface of the crystal film 1010 according to the embodiment of the present invention, respectively, with existing metal film forming techniques such as vacuum deposition and sputtering, and photolithography. Manufactured by forming with. Similarly, in the ultraviolet detection element 1000b, the Schottky electrode 1020 and the ohmic electrode 1030 are formed on the main surface of the α _- Ga ₂ O3 single crystal 1010 formed on the substrate (for example, a sapphire substrate) 1040. It may be formed by film forming technology and photolithography.

FIG. 9 shows an example of a high electron mobility transistor (HEMT) according to the present invention. The HEMT of FIG. 9 includes an n-type semiconductor layer 121a with a wide bandgap, an n-type semiconductor layer 121b with a narrow bandgap, an n + type semiconductor layer 121c, a semi-insulator layer 124, a buffer layer 128, a gate electrode 125a, a source electrode 125b and the like. A drain electrode 125c is provided.

The material of each electrode may be a known electrode material, and examples of the electrode material include Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, Pt, and the like. Metals such as V, Mn, Ni, Cu, Hf, W, Ir, Zn, In, Pd, Nd or Ag or alloys thereof, tin oxide, zinc oxide, renium oxide, indium oxide, indium tin oxide (ITO), Examples thereof include metal oxide conductive films such as indium tin oxide (IZO), organic conductive compounds such as polyaniline, polythiophene or polypyrrole, or mixtures and laminates thereof. The electrode can be formed by a known means such as a vacuum vapor deposition method or a sputtering method.

The n + type semiconductor layer is not particularly limited, but it is preferable that the main component is a semiconductor that is the same as or similar to the main component of the n-type semiconductor layer 121a having a wide bandgap or the n-type semiconductor layer 121b having a narrow bandgap. ..

The crystal film can be used for the n-type semiconductor layer 121a having a wide bandgap and the n-type semiconductor layer 121b having a narrow bandgap, respectively. By using it in this way, it is possible to realize a semiconductor device which is superior in high temperature and high frequency characteristics and further excellent in semiconductor characteristics such as high temperature and high withstand voltage.

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

(Example 1)
1. 1. Formation of buffer layer and mask (0001) A TiO _x film (thickness 2 nm) was formed as a buffer layer on a (0001) plane sapphire substrate by RF sputtering. A SiO _x mask was formed on the obtained titanium oxide film by using RF sputtering and photolithography. The mask pattern was as shown in FIG. 11 and was formed so that the [11-20] axial direction of the sapphire and the linear direction of the plurality of windows 4 (the direction of d1 in FIG. 11) were parallel to each other. In this case, the direction of d2 in FIG. 11 is the [10-10] direction of sapphire. The width D _W of the window was 5 μm, and the width D _M of the mask was 20 μm.

2. 2. Crystal film growth 2-1. HVPE device The halide vapor deposition (HVPE) device 50 used in this embodiment will be described with reference to FIG. The HVPE apparatus 50 includes a reaction chamber 51, a heater 52a for heating the metal source 57, and a heater 52b for heating the substrate fixed to the substrate holder 56, and further supplies oxygen-containing raw material gas into the reaction chamber 51. It includes a pipe 55b, a reactive gas supply pipe 54b, and a board holder 56 on which a board is installed. A metal-containing raw material gas supply pipe 53b is provided in the reactive gas supply pipe 54b to form a double pipe structure. The oxygen-containing raw material gas supply pipe 55b is connected to the oxygen-containing raw material gas supply source 55a, and the oxygen-containing raw material gas is a substrate holder from the oxygen-containing raw material gas source 55a via the oxygen-containing raw material gas supply pipe 55b. The flow path of the oxygen-containing raw material gas is configured so that it can be supplied to the substrate fixed to 56. Further, the reactive gas supply pipe 54b constitutes a flow path of the reactive gas so that the reactive gas can be supplied to the substrate fixed to the substrate holder 56. The metal-containing raw material gas supply pipe 53b is connected to the halogen-containing raw material gas supply pipe 53a, and the halogen-containing raw material gas is supplied to the metal source to become the metal-containing raw material gas, and the metal-containing raw material gas discharge unit 59 is provided. ..

2-2. Preparation for film formation A gallium (Ga) metal source 57 (purity 99.99999% or more) is placed inside the metal-containing raw material gas supply pipe 53b, and the substrate is obtained as a substrate in 1 above on the substrate holder 56 in the reaction chamber 51. A buffer layer and a sapphire substrate with a mask were installed. After that, the heaters 52a and 52b were operated to raise the temperature in the reaction chamber 51 to 540 ° C.

Hydrogen chloride (HCl) gas (purity 99.999% or more) was supplied from the halogen-containing raw material gas supply source 53a to the gallium (Ga) metal 57 arranged inside the metal-containing raw material gas supply pipe 53b. Gallium chloride (GaCl / GaCl ₃ ) was produced by a chemical reaction between a Ga metal and hydrogen chloride (HCl) gas. The obtained gallium chloride (GaCl / GaCl ₃ ) and the O ₂ gas (purity 99.99995% or more) supplied from the oxygen-containing raw material gas supply source 55a are used in the metal-containing raw material supply pipe 53b and the oxygen-containing raw material gas, respectively. It was supplied onto the substrate through the supply pipe 55b. Then, gallium chloride (GaCl / GaCl ₃ ) and O ₂ gas were reacted on the substrate at atmospheric pressure at 540 ° C. to form a film on the substrate. The film formation time was 25 minutes. Here, the partial pressure of the HCl gas supplied from the halogen-containing raw material gas supply source 53a was maintained at 0.125 kPa, and the partial pressure of the _O2 gas supplied from the oxygen-containing raw material gas supply source 55 was maintained at 1.25 kPa. .. The obtained film was identified by performing a 2θ / ω scan at an angle of 15 to 95 degrees using an XRD diffractometer for thin films. The measurement was performed using CuKα ray. As a result, the obtained membrane was κ-Ga ₂ O ₃ . A bird's-eye view SEM image of the obtained crystal film is shown in FIG.

(evaluation)
The cross-sectional TEM image of the obtained crystal film is shown in FIG. 15 (A), and the SAED (Selective area electron diffraction) pattern observed from the [11-20] direction in the window portion and the lateral growth portion is shown in FIGS. 15 (B) and (1). It is shown in C) respectively. As is clear from FIG. 15 (A), in the lateral growth portion, dislocations due to domain mixing and streak-like contrast due to domain boundaries are not observed, and it can be seen that clean crystals are obtained. Further, as is clear from the SAED pattern of the lateral growth portion in FIG. 15 (B), a single crystal κ-Ga ₂ O ₃ was obtained in the lateral growth portion. Further, FIG. 16 shows the result of φ scan of κ-Ga ₂ O ₃ 122 diffraction by XRD. As is clear from FIG. 16, it can be seen that a crystal film in which the peak intensities of the four lines are overwhelmingly higher than those of the other eight lines and the rotational domain is reduced is obtained. Further, FIG. 17 shows the result of EBSD (Electron backscattered diffraction) in which the obtained crystal film was measured from the surface side. As is clear from FIG. 17, it can be seen that one rotation domain A occupies most of the area as compared with the other rotation domains B and C. As shown in FIG. 17, the rotation domain A is a domain in which the [010] direction is perpendicular to the [11-20] direction of the sapphire substrate. Further, it can be seen that a κ-Ga ₂ O ₃ single crystal having a single in-plane orientation is obtained in the lateral growth portion.

(Comparative Example 1)
The formation of the mask on the substrate is as shown in FIG. 11, and the [10-10] axial direction of the sapphire and the linear direction of the plurality of windows 4 (the direction of d1 in FIG. 11) are parallel to each other. The crystal film was grown in the same manner as in Example 1 except that it was formed as described above. The obtained film was identified by performing a 2θ / ω scan at an angle of 15 to 95 degrees using an XRD diffractometer for thin films. The measurement was performed using CuKα ray. As a result, the obtained membrane was κ-Ga ₂ O ₃ . A bird's-eye view SEM image of the obtained crystal film is shown in FIG. Further, FIG. 19 shows the result of φ scan of κ-Ga ₂ O ₃ 122 diffraction by XRD. As is clear from FIG. 19, eight strong peaks and four weak peaks are observed, indicating that there are a plurality of in-plane rotation domains. Further, FIG. 20 shows the measurement result of EBSD. As is clear from FIG. 20, it can be seen that two types of in-plane rotation domains are mixed in the lateral growth portion.

(Example 2)
The formation of the mask on the substrate is as shown in FIG. 12, the mask pattern is as shown in FIG. 12, the window width (diameter) D _W is 5 μm, and the center-to-center distance q in the direction d2 perpendicular to the linear direction in the plurality of windows 4 is 50 μm. The crystal film was grown in the same manner as in Example 1 except that the center-to-center distance p in the direction parallel to the linear direction d1 was set to 20 μm. The appearance of each crystal growth 5 minutes, 15 minutes, and 2 hours after the start of crystal growth was observed by SEM. The results are shown in FIG. As is clear from FIG. 21, hexagonal κ-Ga ₂ O ₃ islands were formed from each window portion of the dot pattern (FIG. 21 (a)). The κ-Ga ₂ O ₃ islands eventually met in the short-period direction of the mask to form a κ-Ga ₂ O ₃ stripe with sawtooth sides (FIG. 21 (b)). Further growth was followed by association of κ-Ga ₂ O ₃ stripes to form a continuous membrane (c). FIG. 22 shows the result of φ scan of κ-Ga ₂ O ₃ 122 diffraction by XRD of the obtained crystal film. As is clear from FIG. 22, it can be seen that a crystal film in which the peak intensities of the four lines are overwhelmingly higher than those of the other eight lines and the rotational domain is reduced is obtained. Further, FIG. 23 shows the result of EBSD (Electron backscattered diffraction) in which the obtained crystal film was measured from the surface side. As is clear from FIG. 23, it can be seen that one rotation domain A occupies most of the area as compared with the other rotation domains B and C. As shown in FIG. 23, the rotation domain A is a domain in which the [010] direction is perpendicular to the [11-20] direction of the sapphire substrate. Further, it can be seen that a κ-Ga ₂ O ₃ single crystal having a single in-plane orientation is obtained in the lateral growth portion.

(Comparative Example 2)
The formation of the mask on the substrate is such that the mask pattern is a regular triangular grid as shown in FIG. 13, and the [11-20] axial direction of sapphire and the linear direction of the plurality of windows 4 (the direction of d1 in FIG. 13) are The crystal film was grown in the same manner as in Example 1 except that it was formed so as to be parallel. The obtained film was identified by performing a 2θ / ω scan at an angle of 15 to 95 degrees using an XRD diffractometer for thin films. The measurement was performed using CuKα ray. As a result, the obtained membrane was κ-Ga ₂ O ₃ . A bird's-eye view SEM image of the obtained crystal film is shown in FIG. 24. In addition, FIG. 25 shows the measurement result of EBSD. As is clear from FIG. 25, it can be seen that three types of in-plane rotation domains are mixed in the lateral growth portion. This is because the stripes are arranged so that the growth rate in the parallel direction of the stripes is the fastest in the domain group shown in red, but the "center-to-center distance q is p × 2 / √3 or more". This is because the conditions were not met and sufficient lateral growth distance (d2 direction) was not secured for the red domain group to eliminate the blue and green domain groups.

(Comparative Example 3)
The crystal film was grown in the same manner as in Example 1 except that the same TiOx buffer layer as in Example 1 was formed on the sapphire substrate and the crystal film was formed without forming the mask. The obtained crystal film was subjected to φ-scan measurement of κ-Ga ₂ O ₃ 122 diffraction by XRD. The results are shown in FIG. As is clear from FIG. 26, 12 peaks of similar intensity are observed, and it can be seen that the three types of in-plane rotation domains are mixed in the same ratio.

(Evaluation of rotation domain content)
For the crystal films obtained in Examples 1 and 2 and Comparative Examples 1 to 3, the content of the rotational domain was determined using the results of EBSD. Specifically, the content of the rotating domain was determined by calculating the ratio of the area of the in-plane rotating domain in the range of 150 μm square from the image of the result measured from the surface side of the obtained crystal film. For example, in the image of FIG. 17, the ratio of the total area of the two in-plane rotation domains B and C to the total area of the three in-plane rotation domains A, B, and C in a 160 μm square area is calculated. As a result, the content of the rotating domain was determined. The results are shown in Table 1. As is clear from Table 1, it can be seen that the crystal films obtained in Examples 1 and 2 have significantly reduced rotational domains.

By adopting the production method of the present invention, a crystal film having a single in-plane orientation of high quality, particularly a (001) plane-oriented κ-Ga ₂ O ₃ crystal film can be obtained. Such a crystal film can be applied to various semiconductor devices such as diodes, transistors (particularly HEMT), and ultraviolet detection devices. Further, the crystal film of κ-Ga ₂ O ₃ is effective for light emitting devices and electric power applications among semiconductor devices because of its large bandgap and excellent translucency.

1 Substrate (crystal substrate)
2 Buffer layer 3 Mask 4 Window 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 (metal halide 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 59 Gas discharge part 121a n-type semiconductor layer with wide band gap 121b n-type semiconductor layer 121c n + type with narrow band gap Semiconductor layer 124 Semi-insulator layer 125a Gate electrode 125b Source electrode 125c Drain electrode 128 Buffer layer 900 Transistor 920 Source 930 Drain 940 Channel 950 Insulation film 960 Gate electrode 970a n + region 970b n + region 980a Electrode 980b Electrode 1000a Ultraviolet detection element 1000b Ultraviolet detection Element 1010 Crystal film (crystalline oxide film)
1020 Schottky electrode 1030 Ohmic electrode 1040 substrate (sapphire substrate)

Claims (25)

A method of supplying a raw material to a substrate provided with a mask having a plurality of windows to grow a crystal film, wherein the crystal film has a plurality of in-plane rotation domain groups, and the plurality of windows have a plurality of in-plane rotation domains. It is linearly arranged and has a striped shape, and the growth rate of the window of the in-plane rotation domain group of one of the plurality of in-plane rotation domain groups along the linear direction is high. A method comprising forming the mask on the substrate and growing the crystal film so as to be greater than the growth rate of the other in-plane rotation domains along the linear direction. The method of claim 1, wherein the crystal film comprises a material selected from the group consisting of oxides, nitrides and oxynitrides. The oxides are κ- (Al _x In _y Ga _1-xy ) ₂ O ₃ , β- (Al _x In _y Ga _1-xy ) ₂ O ₃ , and γ- (Al _x In _y ). Ga _1-x-y ) ₂ O ₃ (where x, y and z satisfy 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), claimed. Item 2. The method according to item 2. The method according to any one of claims 1 to 3, wherein a method selected from the group consisting of an HVPE method, a mist CVD method and a MOCVD method is used for the growth of the crystal film. The method according to any one of claims 1 to 4, wherein the width of the window is in the range of 0.1 μm or more and 20 μm or less. The method according to any one of claims 1 to 5, wherein the width of the mask is in the range of 5 μm or more and 500 μm or less. The method according to any one of claims 1 to 6, wherein the width of the window is smaller than the width of the mask. A method of supplying a raw material to a substrate provided with a mask having a plurality of windows to grow a crystal film, wherein the crystal film has a plurality of in-plane rotation domains, and the plurality of windows have a plurality of in-plane rotation domains. It is arranged linearly and has a dot-like shape, and the growth rate of the window of the in-plane rotation domain group of one of the plurality of in-plane rotation domain groups along the linear direction is high. The mask is formed on the substrate to grow the crystal film so as to be larger than the growth rate of the other in-plane rotation domains along the linear direction, and further, the window. Assuming that the distance between the centers of two adjacent dots in the linear direction is p, the distance q between the centers of the two adjacent dots in the direction perpendicular to the linear direction of the window is p × 2 /. A method that satisfies √3 or more and 500 μm or less. 8. The method of claim 8, wherein the respective shapes of the plurality of windows are circular and / or polygonal. The circle and / or the polygon is a substantially perfect circle and / or a substantially regular polygon, and is of the substantially perfect circle and / or the substantially regular polygon in a direction parallel to the linear direction of the window. Assuming that the center-to-center distance is p, the center-to-center distance q of the substantially perfect circle and / or the substantially regular polygon in the direction perpendicular to the linear direction of the window is p × 2 / √3 or more and 500 μm or less. The method according to claim 9, which satisfies the above conditions. The diameter of the substantially perfect circle and / or the substantially regular polygon is within the range of 0.1 μm or more and 10 μm or less, and the substantially perfect circle and / or the substantially regular shape in a direction parallel to the linear direction of the window. The method according to claim 10, wherein the distance between the centers of the polygon is within the range of 0.3 μm or more and 25 μm or less. The method according to any one of claims 1 to 11, wherein the mask comprises a material selected from the group consisting of oxides, nitrides, oxynitrides, and metals. The method according to any one of claims 1 to 12, wherein the mask is made of an amorphous material. The method according to any one of claims 1 to 13, wherein the substrate further includes a buffer layer between the mask and the substrate. 14. The method of claim 14, further comprising growing the crystal film on the buffer layer. The mask as the first mask is formed on the substrate, the crystal film as the first crystal film is grown, and then the second mask is formed on the first crystal film. Including further growth of the second crystal film, the second mask has a plurality of windows arranged linearly, and the second mask is a plurality of the second mask. The method according to any one of claims 1 to 15, which is formed on the first crystal film so that the window and the plurality of windows of the first mask do not overlap each other. The crystal film is κ- (Al _x In _y Ga _1-xy ) ₂ O ₃ (where x, y and z are 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). Meet) and
The substrate is a substrate selected from the group consisting of a sapphire substrate, a GaN substrate, an AlN substrate, a 6H-SiC substrate and a 4H-SiC substrate.
According to any one of claims 1 to 16, the mask is formed so that the angle formed by the linear direction of the window and the [11-20] direction of the substrate is -5 ° or more and 5 ° or less. The method described. 17. The method of claim 17, wherein the surface index of the substrate is (0001) surface. A crystalline oxide film having a rectangular crystal structure and containing at least one or more metals selected from aluminum, gallium and indium, and containing a rotational domain in the crystalline oxide film. A crystalline oxide film having a ratio of 30% or less. The main component of the crystalline oxide film is (001) plane-oriented κ- (Al _x In _y Ga _1-xy ) ₂ O ₃ (where x, y and z are 0 ≦ x ≦ 1). , 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A semiconductor device comprising the crystalline oxide film according to claim 19 or 20. A semiconductor layer provided on a crystal substrate having a crystal structure including an [11-20] axis or a [10-10] axis, and a first electrode arranged on the first surface side of the semiconductor layer, respectively. A semiconductor element having at least a second electrode and configured in the semiconductor layer so that a current flows in the first direction from the first electrode to the second electrode. A semiconductor element in which the semiconductor layer has a crystal structure different from that of the crystal substrate and the first direction is parallel to the [11-20] axis or the [10-10] axis of the crystal substrate. The semiconductor device according to claim 22, wherein the crystal substrate has a corundum structure. The semiconductor element according to any one of claims 21 to 23, wherein the semiconductor element is selected from the group consisting of a diode, an ultraviolet ray detecting element, and a transistor. The semiconductor device according to claim 23 or 24, which is a high electron mobility transistor (HEMT).

Images