WO2024048710A1

WO2024048710A1 - Crystal film, and method for producing crystal film

Info

Publication number: WO2024048710A1
Application number: PCT/JP2023/031776
Authority: WO
Inventors: 耕史雨堤; 満沖川; 裕之安藤; 勇次加藤; 悟大田
Original assignee: 株式会社Flosfia
Priority date: 2022-08-31
Filing date: 2023-08-31
Publication date: 2024-03-07

Abstract

Provided are: a crystal film which is reduced in dislocation extending along the thickness direction; and a method for producing the crystal film with excellent relative yield.　The crystal film has a corundum structure and contains a crystalline oxide containing gallium, and a cross-section of the crystal film which is cut in the thickness direction has a linear first crystal defect extending along the thickness direction and a linear second crystal defect including an inclining part that inclines from the thickness direction, in which an upper end of the first crystal defect is connected to the inclining part or is positioned below the inclining part.

Description

Crystal film and crystal film manufacturing method

The present disclosure relates to a crystal film and a method for manufacturing the crystal film.

In Patent Document 1, an uneven part consisting of a recess or a convex part is formed directly or through another layer on the crystal growth surface of a crystal substrate, and an epitaxial layer is formed on the uneven part. A crystalline stacked structure in which the epitaxial layer contains a crystalline semiconductor having a corundum structure as a main component is disclosed.

Patent Document 2 discloses that ELO film formation is performed using an m-plane sapphire substrate in which striped ELO masks extending in the a-axis direction are arranged on the substrate surface, with the supply rate being controlled.

Patent No. 6945119 International Publication No. 2020-004250

When a crystalline oxide having a corundum structure and containing gallium is heteroepitaxially grown on a substrate, there is a risk that a plurality of dislocations extending along the thickness direction will occur in the resulting film. If a crystalline film is formed by homoepitaxial growth on a film having such dislocations, there is a risk that a plurality of dislocations extending along the thickness direction will occur in the film as well.

On the other hand, when an ELO mask is used, the ELO mask is embedded in the obtained film and needs to be removed together with a part of the lower end of the obtained film.

An object of the present disclosure is to provide a crystal film in which dislocations extending along the thickness direction are reduced, and a method for manufacturing such a crystal film with a relatively high yield.

In order to solve the above problems, in one aspect of the present disclosure, the crystal film has a corundum structure and includes a crystalline oxide containing gallium, and a cross section cut in the thickness direction is formed along the thickness direction. a linear first crystal defect extending in the direction of the thickness; and a linear second crystal defect including an inclined part inclined from the thickness direction, and an upper end of the first crystal defect is connected to the inclined part. Or it is located below the inclined part.

In order to solve the above problems, in one aspect of the present disclosure, a method for manufacturing a crystal film includes a method for manufacturing a crystal film in which stripe-like irregularities are formed on the main surface of a first crystal layer that has a corundum structure and includes a crystalline oxide containing gallium. A second crystal layer having a corundum structure and containing a crystalline oxide containing gallium is grown in the recessed portion of the uneven portion, and at this time, in a cross section cut in the thickness direction, A linear crystal defect having an inclined portion is formed.

According to the present disclosure, it is possible to provide a crystal film in which dislocations extending along the thickness direction are reduced, and a method for manufacturing such a crystal film with a relatively high yield.

FIG. 1 is a schematic perspective view illustrating a crystal film according to a first embodiment. FIG. 1 is a schematic cross-sectional view illustrating a crystal film according to a first embodiment. 1 is a flowchart schematically showing a method for manufacturing a crystal film according to a first embodiment. 1 is a diagram schematically showing a method for manufacturing a crystal film according to a first embodiment; FIG. 1 is a diagram schematically showing a method for manufacturing a crystal film according to a first embodiment; FIG. 1 is a diagram schematically showing a method for manufacturing a crystal film according to a first embodiment; FIG. FIG. 3 is a schematic perspective view illustrating a crystal film according to a second embodiment. FIG. 3 is a schematic cross-sectional view illustrating a crystal film according to a second embodiment. FIG. 7 is a schematic perspective view illustrating a crystal film according to a third embodiment. FIG. 7 is a schematic cross-sectional view illustrating a crystal film according to a third embodiment. 7 is a flowchart schematically showing a method for manufacturing a crystal film according to a third embodiment. FIG. 7 is a diagram schematically showing a method for manufacturing a crystal film according to a third embodiment. FIG. 7 is a diagram schematically showing a method for manufacturing a crystal film according to a third embodiment. 3 is a schematic cross-sectional view illustrating a crystal film according to Modification Example 1. FIG. FIG. 7 is a schematic cross-sectional view illustrating a crystal film according to Modification Example 2. FIG. FIG. 7 is a schematic cross-sectional view illustrating a crystal film according to Modification Example 4; 1 is a schematic cross-sectional view showing an example of a Schottky barrier diode (SBD) according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view showing an example of a high electron mobility transistor (HEMT) according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view showing an example of a metal oxide semiconductor field effect transistor (MOSFET) according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view showing an example of a junction field effect transistor (JFET) according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view showing an example of an insulated gate bipolar transistor (IGBT) according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view showing an example of a light emitting diode (LED) according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view showing an example of a light emitting diode (LED) according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view showing an example of a junction barrier Schottky diode (JBS) according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view showing an example of a junction barrier Schottky diode (JBS) according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view showing an example of a metal oxide semiconductor field effect transistor (MOSFET) according to an embodiment of the present disclosure. FIG. 1 is a block configuration diagram illustrating an example of a control system that employs a semiconductor device according to an embodiment of the present disclosure. 1 is a circuit diagram illustrating an example of a control system that employs a semiconductor device according to an embodiment of the present disclosure. FIG. 1 is a block configuration diagram illustrating an example of a control system that employs a semiconductor device according to an embodiment of the present disclosure. 1 is a circuit diagram illustrating an example of a control system that employs a semiconductor device according to an embodiment of the present disclosure. FIG. 7 is a diagram showing an example of observation of a cross section of a crystal film according to a second embodiment. FIG. 7 is a partially enlarged view of a diagram showing an observation example of a cross section of a crystal film according to a second embodiment. FIG. 7 is a diagram showing an example of observation of a cross section of a crystal film according to an example of Modification Example 7; 12 is a partially enlarged view of a diagram showing an example of observation of a cross section of a crystal film according to an example of Modification 7. FIG.

Hereinafter, embodiments of the present disclosure will be described using drawings, but the claimed invention is not limited to these embodiments. Further, not all of the combinations of configurations described in the embodiments are essential to solving the problem and are not limited to them. Further, each configuration of the present disclosure is described within a range that does not hinder solving the problems of the present disclosure. Note that the same components are given the same reference numerals to omit redundant explanations.

Additionally, as will be apparent to those skilled in the art, features not described herein or illustrated in the drawings are not necessarily drawn to scale. Note also that one feature in one form may be used in another form. Descriptions of well-known elements and processing techniques may be omitted so as not to unnecessarily obscure the present disclosure. The examples used herein are merely to aid in understanding the disclosure and to further enable one skilled in the art to practice forms of the disclosure. Therefore, the forms and examples herein should not be construed as limiting the scope of this disclosure, which is defined only by the claims and applicable law.

Although terms such as "first", "second", etc. are used to describe various elements used herein, the elements are not limited by these terms. The terms first, second, etc. are only used to distinguish one element from another. For example, a first element can be referred to as a second element, and a second element can be referred to as a first element, without departing from the scope of this disclosure. As used herein, the term "and/or" encompasses any or all combinations of one or more of the listed items.

In the present disclosure, one side in a direction parallel to the thickness direction Z (see FIG. 1) of the crystal film is referred to as "upper" and the other side is referred to as "lower." In particular, "upper" and "lower" are defined as the upper side of the crystal layer 12 of the crystal film 10 in FIG. 1 when viewed from the crystal layer 11, and the lower side when viewed from the crystal layer 12. Of the two main surfaces of a layer, substrate, or other member, the surface located above will be described as an upper surface, and the surface located below will be described as a lower surface. These "up" and "down" directions are not limited to the direction of gravity or the direction of attachment to a substrate or the like during mounting of the semiconductor device. Further, in the present disclosure, the direction in which the uneven portion extends, which is perpendicular to the thickness direction Z of the crystal film, will be described as the front-rear direction Y. In addition, in the present disclosure, a direction perpendicular to the thickness direction Z and the front-back direction Y will be described as a left-right direction X. Note that although this specification will be described using the term "top view," it may be translated as "planar view."

When an element, such as a layer, region, or substrate, is referred to as being "on" another element, it may be directly on top of the other element, or there may be intervening elements. I hope you understand that. When an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to another element, or there may be intervening elements. I hope you understand that.

The terminology used herein is for the purpose of describing particular forms only and is not intended to limit the disclosure. As used herein, the terms "comprising" and "comprising" refer to the presence of the listed element and do not exclude the presence of one or more other elements.

Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms used herein are to be interpreted to have meanings consistent with the context of this specification and the relevant art. It is also understood that, unless otherwise defined herein, terms used herein are not to be construed in an idealized or overly formal sense.

(First embodiment)
FIG. 1 is a schematic perspective view illustrating a crystal film 10 according to the first embodiment. FIG. 2 is a schematic cross-sectional view illustrating the crystal film 10 according to the first embodiment, and is a cross-sectional view taken along the line II-II in FIG. The crystal film 10 according to the first embodiment is used, for example, as a semiconductor film of a semiconductor device or the like. As shown in FIGS. 1 and 2, the crystal film 10 includes a crystal layer 11 and a crystal layer 12 located on the crystal layer 11. Note that the crystal film 10 shown in FIG. 1 may be, for example, a part of a disc-shaped crystal film. The crystal layer 11 is an example of a first crystal layer, and the crystal layer 12 is an example of a second crystal layer.

(Crystal layer 11)
The crystal layer 11 is, for example, an n-type semiconductor layer. The crystal layer 11 is, for example, an epitaxial growth film that is heteroepitaxially grown on a sapphire substrate. The crystal layer 11 contains a crystalline oxide semiconductor as a main component. Note that the crystalline oxide semiconductor is an example of a crystalline oxide. The crystal layer 11 may be a film grown on a sapphire substrate via another layer such as a buffer layer.

The crystalline oxide semiconductor included in the crystal layer 11 has a corundum structure. In this embodiment, the a-axis direction of the crystalline oxide semiconductor is along the left-right direction X. The c-axis direction of the crystalline oxide semiconductor is along the front-back direction Y. The m-axis direction of the crystalline oxide semiconductor is along the thickness direction Z. That is, the plane orientation of the main surface of the crystal layer 11 is the m-plane in a region where the normal line is along the thickness direction Z. In the first embodiment, the left-right direction X is sometimes referred to as the a-axis direction, the front-rear direction Y is sometimes referred to as the c-axis direction, and the thickness direction is sometimes referred to as the m-axis direction.

The crystalline oxide semiconductor included in the crystal layer 11 includes gallium. The crystalline oxide semiconductor is a metal oxide containing, in addition to gallium, one or more metals selected from, for example, aluminum, indium, iron, chromium, vanadium, titanium, rhodium, nickel, cobalt, and iridium. There may be. In an embodiment of the present disclosure, it is also preferable that the crystalline oxide semiconductor further contains at least one metal selected from aluminum and indium in addition to gallium, and α-Ga ₂ O ₃ or a mixture thereof. Most preferably, it is crystalline. According to the present disclosure, a multilayer film with reduced dislocations can be obtained even when using α-Ga ₂ O ₃ or its mixed crystal, which is a thermally metastable phase, for example.

Note that the "main component" means, for example, when the crystalline oxide semiconductor is Ga ₂ O ₃ , the atomic ratio of gallium among all the metal elements in the crystal layer 11 is 0.5 or more. This means that the layer 11 contains Ga ₂ O ₃ . In the present disclosure, the atomic ratio of gallium among all metal elements in the crystal layer 11 is preferably 0.7 or more, and more preferably 0.9 or more. Although the crystal layer 11 is single crystal in this embodiment, it may be polycrystalline.

The carrier density of the crystal layer 11 can be appropriately set by adjusting the doping amount. Preferably, the crystal layer 11 contains a dopant. The dopant may be a known dopant. In the embodiment of the present disclosure, when the crystal layer 11 is mainly composed of a crystalline oxide semiconductor containing gallium, preferable examples of the dopant include tin, germanium, silicon, titanium, zirconium, vanadium, or Examples include n-type dopants such as niobium. In embodiments of the present disclosure, the n-type dopant is preferably Sn, Ge, or Si. The content of the dopant in the composition of the crystal layer 11 is preferably 0.00001 atomic% or more, more preferably 0.00001 atomic% to 20 atomic%, and 0.00001 atomic% to 10 atomic%. Most preferably. More specifically, the concentration of the dopant may typically be about 1×10 ¹⁶ /cm ³ to 1×10 ²² /cm ³ , and the concentration of the dopant may be, for example, about 1×10 ¹⁷ /cm 3 . The concentration may be as low as ³ or less.

The crystal layer 11 has, on the upper surface 21 (see FIG. 2), uneven portions 22 arranged, for example, in the a-axis direction. The uneven portion 22 has a stripe shape and extends along the c-axis direction (front-back direction Y). The uneven portion 22 has a concave portion 23 and a convex portion 24 . The concave portion 23 and the convex portion 24 are adjacent to each other. Adjacent recesses 23 and protrusions 24 are continuous at equal intervals along the a-axis direction (left-right direction X). Note that the upper surface 21 refers to the upper surface of the main surface of the crystal layer 11.

The recess 23 is formed, for example, on the upper surface 21 by etching or the like. In this case, the uneven portion 22 does not include other materials such as a mask, but constitutes a part of the crystal layer 11 (constituted of substantially the same material as the crystal layer 11). The recess 23 has a plurality of growth surfaces on which the crystal layer 12 grows. The recess 23 has, for example, side surfaces 23a, 23b and a bottom surface 23c as the growth surfaces. In this embodiment, the side surfaces 23a and 23b are crystal growth surfaces for lateral growth, and the bottom surface 23c is a crystal growth surface for vertical growth.

The side surfaces 23a and 23b are planes extending in the front-rear direction Y and the thickness direction Z. The side surfaces 23a and 23b are, for example, a-planes. The bottom surface 23c is a plane that extends in the front-rear direction Y and the left-right direction X. The bottom surface 23c is, for example, an m-plane. The bottom surface 23c is located between the side surface 23a and the side surface 23b. The side surface 23a is located on the left side of the bottom surface 23c, and the side surface 23b is located on the right side of the bottom surface 23c. Note that in the present disclosure, the side surfaces 23a, 23b and the bottom surface 23c are part of the top surface 21. In FIG. 2, the portion where the bottom surface 23c and the side surface 23a or the side surface 23b are connected is shown as a corner, but may have other shapes such as a circular arc.

The side surface 23a may have an angle θ1 of 60 degrees or more with the upper surface 25 of the convex portion 24. The angle θ1 between the side surface 23a and the top surface 25 is, for example, 90 degrees. The side surface 23b only needs to have an angle θ2 of 60 degrees or more with the top surface 25. The angle θ2 between the side surface 23b and the top surface 25 is, for example, 90 degrees. Note that in this embodiment, the top surface 21 and the bottom surface 23c are parallel. The angle between the side surfaces 23a, 23b and the bottom surface 23c is 90 degrees.

The ratio of the depth d1 of the recess 23 to the width w1 of the recess 23 is preferably within a range such that the upper end of the vertically grown film growing in the thickness direction Z from the bottom surface 23c is located below the upper surface of the crystal layer 12. , more preferably within the range located within the recess 23. The ratio of the depth d1 to the width w1 is preferably 0.125 or more and less than 2.0, more preferably 0.57 or more and less than 2.0. In the embodiment, for example, the ratio of the depth d1 to the width w1 is greater than or equal to any value within the range of 0.57 or more and 0.69 or less, and is a value within the range of 0.57 or more and 0.69 or less. Even more preferably.

The depth d1 of the recess 23 is preferably 0.5 μm or more. The depth d1 is, for example, 1.51 μm. The depth d1 refers to the length from the upper end to the lower end of the recess 23 in the thickness direction Z. In this embodiment, the depth d1 is equal to the height of the convex portion 24. The width w1 of the recess 23 may be determined as appropriate depending on the ratio to the depth d1. The width w1 is, for example, 2.5 μm. The width w1 refers to the length along the left-right direction X from the left end to the right end of the recessed portion 23. The width w1 is equal to the distance in the left-right direction X between the convex portions 24 adjacent to each other. In this embodiment, the value obtained by dividing half the length of the width w1 by the depth d1 is smaller than 4.

The ratio of the width w1 of the recesses 23 to the distance w2 in the left-right direction X between mutually adjacent recesses 23 is preferably 1 or more, and more preferably 2 or more. The larger the ratio of the width w1 to the distance w2, the better. The larger the value of the width w1, the more the number of recesses 23 can be reduced. The shorter the distance w2, the more the amount of crystal layer 12 stacked on the convex portion 24 can be reduced. In this embodiment, for example, the ratio of the width w1 to the distance w2 is 10. In this embodiment, the distance w2 is equal to the length along the left-right direction X from the left end to the right end of the upper surface of the convex portion 24. The shorter the distance w2, the better.

The convex portion 24 refers to, for example, the upper end portion of the crystal layer 11 where the concave portion 23 is not formed. The side surfaces of the convex portion 24 are common to the side surfaces 23a and 23b of the recessed portion 23. That is, the side surfaces 23a and 23b may be defined as the side surfaces of the convex portion 24. Note that the upper surface 21 includes the upper surface 25 of the convex portion 24 .

When the crystal layer 11 is an epitaxially grown film grown by heteroepitaxial growth, it may include dislocations along the thickness direction Z. The dislocations can be observed as dislocation lines 26 in a cross section of the crystal film 10 taken in the thickness direction Z, as shown in FIG. The cross section of the crystal layer 11 includes a plurality of dislocation lines 26. Each dislocation line 26 may be continuous, for example, from the lower surface 27 of the crystal layer 11 to the upper surface 25 of the convex portion 24 or the bottom surface 23c of the concave portion 23. Although the dislocation line 26 is schematically shown as a straight line in FIG. 2, it is sufficient that it is generally along the thickness direction Z, and at least a portion thereof may be inclined, or at least a portion may be a curved line. There may be. In the present disclosure, each dislocation line, each grain boundary, boundary between crystal layers, boundary between films, etc. can be observed by a known method such as a cross-sectional TEM (transmission electron microscope) image or a cross-sectional SEM (scanning electron microscope) image. . Furthermore, each dislocation line, each grain boundary, each crystal layer boundary, each film boundary, etc. may be observed as linear crystal defects.

The thickness of the crystal layer 11 may be 1 μm or less or 1 μm or more. In the embodiment of the present disclosure, the thickness of the crystal layer 11 is preferably 1 μm or more, and preferably 3 μm or more. The thickness of the crystal layer 11 is greater than the depth d1 of the recess 23, and in this embodiment is thicker than 1.51 μm. Note that the thickness of the crystal layer 11 refers to the length along the thickness direction Z from the lower surface 27 to the upper surface 25 of the crystal layer 11 in the embodiment of the present disclosure.

(Crystal layer 12)
The crystal layer 12 is, for example, an n-type semiconductor layer. Crystal layer 12 is placed directly on crystal layer 11 . The crystal layer 12 is in contact with the uneven portions 22 of the crystal layer 11 . Crystal layer 12 has the same conductivity type as crystal layer 11. The crystal layer 12 is, for example, an epitaxially grown film that is homoepitaxially grown on the crystal layer 11 . The crystal layer 12 contains a crystalline oxide semiconductor as a main component. Note that the crystalline oxide semiconductor is an example of a crystalline oxide.

The crystalline oxide semiconductor included in the crystal layer 12 has a corundum structure. The crystalline oxide semiconductor has the same structure as the crystalline oxide semiconductor included in the crystal layer 11. In this embodiment, the a-axis direction of the crystalline oxide semiconductor included in the crystal layer 12 is along the left-right direction X. The c-axis direction of the crystalline oxide semiconductor is along the front-back direction Y. The m-axis direction of the crystalline oxide semiconductor is along the thickness direction Z. That is, the plane orientation of the main surface of the crystal layer 12 is the m-plane in a region where the normal line is along the thickness direction Z.

The crystalline oxide semiconductor included in the crystal layer 12 includes gallium. The crystalline oxide semiconductor is a metal oxide containing, in addition to gallium, one or more metals selected from, for example, aluminum, indium, iron, chromium, vanadium, titanium, rhodium, nickel, cobalt, and iridium. There may be. The crystalline oxide semiconductor is preferably the same metal oxide as the crystalline oxide semiconductor contained in the crystal layer 11. In the embodiment of the present disclosure, it is preferable that the crystalline oxide semiconductor contained in the crystal layer 12 further contains at least one metal selected from aluminum and indium in addition to gallium. ₂ O ₃ or a mixed crystal thereof is most preferred. According to the present disclosure, a multilayer film with reduced dislocations can be obtained even when using α-Ga ₂ O ₃ or its mixed crystal, which is a thermally metastable phase, for example.

Note that the "main component" means, for example, when the crystalline oxide semiconductor is Ga ₂ O ₃ , the atomic ratio of gallium among all the metal elements in the crystal layer 12 is 0.5 or more. This means that the layer 12 contains Ga ₂ O ₃ . In the present disclosure, the atomic ratio of gallium among all metal elements in the crystal layer 12 is preferably 0.7 or more, and more preferably 0.9 or more. Although the crystal layer 12 is single crystal in this embodiment, it may be polycrystalline.

The carrier density of the crystal layer 12 can be appropriately set by adjusting the doping amount. Although the carrier density of the crystal layer 12 may be different from the carrier density of the crystal layer 11, it is preferable that the carrier density is about the same. Preferably, the crystal layer 12 contains a dopant. The dopant may be a known dopant. The dopant may be different from the dopant contained in the crystal layer 11, but is preferably the same. In the embodiment of the present disclosure, when the crystal layer 12 is mainly composed of a crystalline oxide semiconductor containing gallium, preferable examples of the dopant include tin, germanium, silicon, titanium, zirconium, vanadium, or Examples include n-type dopants such as niobium. In embodiments of the present disclosure, the n-type dopant is preferably Sn, Ge, or Si. The content of the dopant in the composition of the crystal layer 11 is preferably 0.00001 atomic% or more, more preferably 0.00001 atomic% to 20 atomic%, and 0.00001 atomic% to 10 atomic%. Most preferably. More specifically, the concentration of the dopant may typically be about 1×10 ¹⁶ /cm ³ to 1×10 ²² /cm ³ , and the concentration of the dopant may be, for example, about 1×10 ¹⁷ /cm 3 . The concentration may be as low as ³ or less.

As shown in FIG. 2, the lower surface 31 of the crystal layer 12 is joined to the upper surface 21 of the crystal layer 11. The lower surface 31 and the upper surface 21 are also interfaces between the crystal layers 12 and 11. The crystal layer 12 has, on the lower surface 31, an uneven portion 32 having a shape corresponding to the uneven portion 22 on the upper surface 21. That is, the uneven portions 32 are striped and arranged in the a-axis direction. The uneven portion 32 is in contact with the uneven portion 22. The uneven portion 32 has a concave portion 33 and a convex portion 34 . In addition to the uneven portions 32 , the crystal layer 12 includes a region 43 directly above the convex portion 24 of the crystal layer 11 and a region 44 directly above the convex portion 34 . Note that the lower surface 31 refers to the lower surface of the main surface of the crystal layer 12.

The recess 33 is formed, for example, as a result of the formation of the protrusion 34. The inner space of the recess 33 is filled with the protrusion 24 . The crystal layer 12 located on the concave portion 33 is, for example, an epitaxial growth film grown on the upper surface 25 of the convex portion 24 .

The convex portion 34 is formed in the internal space of the concave portion 23. The convex portion 34 is, for example, an epitaxially grown film grown from the growth surface of the concave portion 23 . At this time, the convex portion 34 includes horizontally grown films 34a and 34b and a vertically grown film 34c. The laterally grown film 34a is a film grown laterally (in the a-axis direction) from the side surface 23a of the recess 23. The laterally grown film 34b is a film grown laterally (in the a-axis direction) from the side surface 23b of the recess 23. The direction of growth of the laterally grown film 34a is opposite to the direction of growth of the laterally grown film 34b. The vertically grown film 34c is a film grown in the thickness direction Z (vertical direction) from the bottom surface 23c, and the growth direction is upward.

The convex portion 34 includes a grain boundary 37 within the concave portion 23, which is an interface between the laterally grown film 34a and the laterally grown film 34b. The grain boundaries 37 may appear as dislocations 38 in the crystal layer 12 above the recesses 23 . In FIG. 2, a line indicating the grain boundary 37 and a line indicating the dislocation 38 are shown continuously. Although the boundary between the grain boundary 37 and the dislocation 38 does not have to be clear, in this embodiment, for convenience, the position in the thickness direction Z is assumed to be the same as the upper surface 25 of the convex portion 24 .

Note that the grain boundaries 37 and dislocations 38 do not need to be continuous, and the boundaries may be near the top surface of the crystal layer 12. Furthermore, there may be no dislocations 38, and the grain boundaries 37 may reach the upper surface of the crystal layer 12. Furthermore, the dislocations 38 may be continuous or intermittent in the front-rear direction Y. Note that although the grain boundaries 37 and dislocations 38 are schematically represented as straight lines in FIG. The portion may be a curved line. The grain boundary 37 is an example of a third crystal defect.

The grain boundary 37 may be located within the recess 23 in the left-right direction X. The position of the grain boundary 37 in the left-right direction X depends on the growth rate of the laterally grown film 34a and the laterally grown film 34b. If the growth rate of the laterally grown film 34a is faster than the growth rate of the laterally grown film 34b, the grain boundary 37 is located closer to the side surface 23b than the center of the recess 23 in the left-right direction X. If the growth rate of the laterally grown film 34a is slower than the growth rate of the laterally grown film 34b, the grain boundary 37 is located closer to the side surface 23a than the center of the recess 23 in the left-right direction X. If the growth rate of the laterally grown film 34a is comparable to that of the laterally grown film 34b, the grain boundary 37 will be located near the center of the recess 23 in the left-right direction X.

The convex portion 34 includes a grain boundary 39 within the concave portion 23, which is an interface between the horizontally grown films 34a, 34b and the vertically grown film 34c. The grain boundary 39 has an inclined portion inclined from the thickness direction Z. The grain boundaries 39 include a grain boundary 39a that is an interface between the horizontally grown film 34a and the vertically grown film 34c, and a grain boundary 39b that is the interface between the horizontally grown film 34b and the vertically grown film 34c. has. Note that the grain boundaries 39, 39a, and 39b are each an example of a second crystal defect.

A plurality of grain boundaries 39 are arranged along the left-right direction X (lateral direction), for example, depending on the number of recesses 23. The grain boundaries 39 have a triangular shape in the cross section shown in FIG. The grain boundary 39 is connected to the lower end of the grain boundary 37. In this embodiment, the ratio of the dimension of the grain boundary 39 along the thickness direction Z to the dimension along the left-right direction X is within a range of 0.57 or more and 0.69 or less, for example. Note that the grain boundary 39 is an example of a convex portion in which the inner side is located higher than both outer sides in the lateral direction (horizontal direction X). The grain boundary 37 is an example of a portion extending along the thickness direction Z above the inclined portion.

The ratio of the dimension of the grain boundaries 39 along the left-right direction X to the distance between mutually adjacent grain boundaries 39 among the grain boundaries 39 arranged in the left-right direction X is preferably 1 or more. The larger the ratio, the better. The larger the ratio, the more the number of dislocation lines 26 located between grain boundaries 39 can be reduced. In this embodiment, the distance between the grain boundaries 39 is equal to the distance w2 of the recess 23, but may be larger than the distance w2.

As shown in FIG. 2, the grain boundaries 39a and 39b appear linearly in a cross section cut in the thickness direction Z. For example, the left end or lower end of the grain boundary 39a is located at the lower end of the side surface 23a or the left end of the bottom surface 23c. For example, the right end or the upper end of the grain boundary 39a is located directly above the center of the bottom surface 23c in the left-right direction X. For example, the right end or lower end of the grain boundary 39b is located at the lower end of the side surface 23b or the right end of the bottom surface 23c. For example, the left end or the upper end of the grain boundary 39b is located directly above the center of the bottom surface 23c in the left-right direction X. The right end or upper end of the grain boundary 39a is connected to the left end or upper end of the grain boundary 39b. Although the grain boundaries 39 are schematically shown as straight lines in FIG. 2, at least a portion thereof may be curved lines. Since the grain boundaries 39a and 39b have opposite inclinations in the left-right direction X, the grain boundaries 39 have a triangular shape.

The grain boundaries 39a are inclined with respect to the thickness direction Z and the left-right direction X so that the farther to the right from the side surface 23a, the higher the grain boundaries are located. The grain boundaries 39b are inclined with respect to the thickness direction Z and the left-right direction X so that they are located higher as they leave the side surface 23b to the left. In this embodiment, the entire grain boundaries 39a, 39b are sloped portions, but a portion of the grain boundaries 39a, 39b may be sloped portions. That is, a portion of the grain boundaries 39a, 39b may extend along the thickness direction Z or the left-right direction X. In this embodiment, the inclined portion is inclined from the a-axis direction. Note that the grain boundary 39 includes a plurality of inclined parts. In this embodiment, the grain boundary 39 includes two inclined parts.

The grain boundaries 39a have an inclination angle θ3 from the thickness direction Z. The inclination angle θ3 correlates, for example, with the ratio of the growth rate of the horizontally grown film 34a to the growth rate of the vertically grown film 34c. For example, when the growth rate of the horizontally grown film 34a is faster than the growth rate of the vertically grown film 34c, the inclination angle θ3 becomes greater than 45 degrees. When the growth rate of the horizontally grown film 34a is slower than the growth rate of the vertically grown film 34c, the inclination angle θ3 becomes smaller than 45 degrees. When the growth rate of the horizontally grown film 34a is the same as the growth rate of the vertically grown film 34c, the inclination angle θ3 is about 45 degrees. In this embodiment, the inclination angle θ3 is about 36 degrees to 42 degrees.

The grain boundaries 39b have an inclination angle θ4 from the thickness direction Z. The inclination angle θ4 correlates, for example, with the ratio of the growth rate of the horizontally grown film 34b and the growth rate of the vertically grown film 34c. For example, when the growth rate of the horizontally grown film 34b is faster than the growth rate of the vertically grown film 34c, the inclination angle θ4 is greater than 45 degrees. When the growth rate of the horizontally grown film 34b is slower than the growth rate of the vertically grown film 34c, the inclination angle θ4 is smaller than 45 degrees. When the growth rate of the horizontally grown film 34b is the same as the growth rate of the vertically grown film 34c, the inclination angle θ4 is about 45 degrees. In this embodiment, the tilt angle θ4 is about 36 degrees to 42 degrees.

The vertically grown film 34c may include dislocations along the thickness direction Z. The dislocations are, for example, inherited dislocations along the thickness direction Z of the crystal layer 11 (dislocation lines 26 in FIG. 2). As shown in FIG. 2, dislocations in the vertically grown film 34c can be observed as dislocation lines 41 in a cross section of the crystal film 10 taken in the thickness direction Z. The cross section of the vertically grown film 34c includes dislocation lines 41. In this embodiment, a plurality of dislocation lines 41 are located within the recess 23 . The vertically grown film 34c has a triangular shape in the cross section shown in FIG. Note that the dislocation line 41 is an example of a first crystal defect.

The lower end of the dislocation line 41 is located at the lower end of the convex portion 34. The upper end of the dislocation line 41 is connected to the grain boundary 39, for example. The upper end of the dislocation line 41 may not be connected to the grain boundary 39 and may be located below the grain boundary 39.

The region 43 directly above the convex portion 24 is, for example, an epitaxially grown film grown from the upper surface 25 of the convex portion 24. The length of the region 43 along the left-right direction X from the left end to the right end is equal to the length along the left-right direction X from the left end to the right end of the upper surface of the convex portion 24 . Region 43 is a vertically grown film. The region 43 may include dislocations along the thickness direction Z. The dislocations are, for example, inherited dislocations along the thickness direction Z of the crystal layer 11 (dislocation lines 26 in FIG. 2). As shown in FIG. 2, the dislocations in the region 43 can be observed as dislocation lines 42 in a cross section of the crystal film 10 taken in the thickness direction Z. Although only one dislocation line 42 is shown in the cross section of the region 43 in FIG. 2, it may include a plurality of dislocation lines 42.

Note that the dislocation lines 41 and 42 may or may not be continuous with the dislocation line 26. Although the dislocation lines 41 and 42 are schematically shown as straight lines in FIG. 2, they only need to be approximately along the thickness direction Z, and may be at least partly inclined, or at least partly curved. There may be.

The region 44 directly above the convex portion 34 is, for example, an epitaxially grown film grown from the upper surface 21 of the crystal layer 11. The length of the region 44 from the left end to the right end along the left-right direction X is equal to the width w1 of the recess 23.

The thickness of the crystal layer 12 may be 1 μm or less, or 1 μm or more. In the embodiment of the present disclosure, the thickness of the crystal layer 12 is preferably 1 μm or more, and preferably 3 μm or more. The thickness of the crystal layer 12 is preferably larger than the depth of the recess 33, that is, the depth d1 of the recess 23, and in this embodiment, it is thicker than 1.51 μm. Note that the thickness of the crystal layer 12 refers to the length along the thickness direction Z from the lower end of the convex portion 34 to the upper surface of the crystal layer 12 in the embodiment of the present disclosure.

According to such a configuration, it is possible to obtain a crystal film in which dislocations extending along the thickness direction Z are reduced. The laterally grown film 34a and the laterally grown film 34b may be combined. Since the laterally grown film 34a and the laterally grown film 34b can meet within the recess 23, the possibility that the laterally grown film 34a and the laterally grown film 34b will not come together within the crystal layer 12 is suppressed. Furthermore, the volume of the vertically grown film 34c can be reduced. The vertically grown film 34c can be a homoepitaxially grown film.

The grain boundary 39a, which is the interface between the horizontally grown film 34a and the vertically grown film 34c, and the grain boundary 39b, which is the interface between the horizontally grown film 34b and the vertically grown film 34c, can be continuous. The grain boundaries 39 may be formed to cover the entire vertically grown film 34c. Even if the dislocation lines 26 of the crystal layer 11 cause the dislocation lines 41 of the vertically grown film 34c, dislocation lines extending along the thickness direction Z are suppressed from being caused in the horizontally grown films 34a, 34b. be able to. Furthermore, it is possible to suppress the occurrence of dislocations extending along the thickness direction Z in the region 44 directly above the convex portion 34 .

According to such a configuration, the number of convex portions 24 of the crystal layer 11 can be made relatively small, and the region 43 of the crystal layer 12 can be reduced. By narrowing the width of the convex portion 24, the width of the region 43 can be narrowed. The number of dislocation lines 42 that may occur in the crystal layer 12 can be reduced.

According to such a configuration, the upper ends of the dislocation lines 26 and 41 that vertically overlap the recesses 23 can be located below the upper surface 25 of the protrusion 24 that is the upper end of the crystal layer 11.

According to such a configuration, the crystal film 10 can be used in semiconductor devices and the like as a semiconductor layer that does not include a mask such as SiO2. Further, the device characteristics of a semiconductor device using the crystal film 10 can be improved.

(Method for manufacturing crystal film 10)
An example of a method for manufacturing the crystal film 10 will be described below with reference to FIGS. 3 to 6. FIG. 3 is a diagram illustrating an outline of a method for manufacturing the crystal film 10.

As shown in FIG. 3, the method for manufacturing the crystal film 10 includes, for example, a step S1 of forming the crystal layer 11 on the substrate 13, a step S2 of forming the uneven portion 22 on the upper surface 21 of the crystal layer 11, and a step S2 of forming the uneven portion 22 on the upper surface 21 of the crystal layer 11. The method includes a step S3 of forming the crystal layer 12 on the upper surface 21 of the layer 11, and a step S4 of removing the substrate 13.

As shown in FIG. 4, in step S1, the crystal layer 11 is laminated on the substrate 13 by, for example, a mist CVD method. Note that the crystal layer 11 may be laminated on the substrate 13 by a known method. Examples of methods for forming the crystal layer 11 include, in addition to the mist CVD method, a CVD method, MOCVD method, MOVPE method, mist epitaxy method, MBE method, HVPE method, pulse growth method, or ALD method. In the embodiment of the present disclosure, it is preferable that the method for forming the crystal layer 11 is a mist CVD method or a mist epitaxy method. In the mist CVD method or the mist epitaxy method, for example, a raw material solution is atomized (atomization step), droplets are suspended, and after atomization, the resulting atomized droplets are transported onto the substrate using a carrier gas. (Transportation step) Next, by thermally reacting the atomized droplets near the substrate, a semiconductor film having a corundum structure and containing a crystalline oxide semiconductor containing gallium as a main component is laminated on the substrate 13. (Film forming process) A crystal layer 11 is formed by this.

The substrate 13 is, for example, a plate-shaped sapphire substrate. The substrate 13 may be any substrate as long as it can support the semiconductor film. Although the substrate 13 may be an insulating substrate, a semiconductor substrate, a metal substrate, or a conductive substrate, it is preferable that the substrate 13 is an insulating substrate. It is also preferable that the substrate has a metal film on its surface. The substrate 13 may be, for example, a base substrate containing a substrate material having a corundum structure as a main component, a base substrate containing a substrate material having a β-gallium structure as a main component, or a base substrate containing a substrate material having a hexagonal structure as a main component. Examples include a base substrate. Here, the term "main component" means that the substrate material having the specific crystal structure preferably accounts for 50% or more, more preferably 70% or more, and still more preferably 90% of the total components of the substrate material in terms of atomic ratio. % or more, and may be 100%.

The substrate material may be any known material. As the substrate material having the corundum structure, for example, α-Al ₂ O ₃ (sapphire substrate) or α-Ga ₂ O ₃ is preferably mentioned, and a-plane sapphire substrate, m-plane sapphire substrate, r-plane sapphire substrate More preferable examples include a c-plane sapphire substrate, an α-type gallium oxide substrate (a-plane, m-plane, or r-plane). As a base substrate mainly composed of a substrate material having a β-Galia structure, for example, a β-Ga ₂ O ₃ substrate, or a substrate containing Ga ₂ O ₃ and Al ₂ O ₃ and containing more than 0 wt% of Al ₂ O ₃ and Examples include a mixed crystal substrate having a content of 60 wt% or less. Further, examples of the base substrate mainly composed of a substrate material having a hexagonal crystal structure include a SiC substrate, a ZnO substrate, and a GaN substrate.

Preferably, the substrate 13 has a diameter of 2 inches or more, or 4 inches or more. Preferably, the area of the substrate 13 is about 15.9 cm ² or more or about 31.9 cm ² or more.

As shown in FIG. 5, in step S2, the uneven portion 22 is formed, for example, on the upper surface 21 of the crystal layer 11 stacked on the substrate 13 by etching or the like. As a method for forming the uneven portion 22, for example, using a known photolithography technique, patterning is performed so as to have a striped uneven shape arranged in the a-axis direction, and then etching is performed. Examples of etching include dry etching and wet etching. Note that the uneven portion 22 may be formed by other known means, such as known patterning means such as electron beam lithography, laser patterning, and subsequent etching (for example, dry etching or wet etching). There may be. Further, although the convex portions 24 may be formed of the same material as the crystal layer 11 to form the concave and convex portions 22, it is preferable to form the concave and convex portions 22 by forming the concave portions 23. Step S2 is an example of arranging striped depressions and depressions in the a-axis direction on the main surface of the first crystal layer that has a corundum structure and includes a crystalline oxide containing gallium.

In this embodiment, the recess 23 is formed such that, for example, the ratio of the depth d1 to the width w1 is within the range of 0.57 or more and 0.69 or less.

As shown in FIG. 6, in step S3, the crystal layer 12 is laminated on the crystal layer 11 on which the uneven portions 22 are formed, for example, by a mist CVD method. Crystal layer 12 can be stacked in the same way as crystal layer 11. Note that, like the crystal layer 11, the crystal layer 12 may be laminated on the crystal layer 11 by the known forming means. The crystal layer 12 is formed of the same material and composition as the crystal layer 11, for example. The crystal layer 12 has the same conductivity type as the crystal layer 11, for example, and is formed to be n-type.

In step S3, a convex portion 34 is formed as the crystal layer 12 in the internal space of the concave portion 23 of the crystal layer 11. As a result, uneven portions 32 are formed on the lower surface 31 of the crystal layer 12 in accordance with the shape of the uneven portions 22 of the crystal layer 11 .

At this time, the lateral growth film 34a of the convex portion 34 moves from the side surface 23a of the concave portion 23 to the right, and the lateral growth film 34b of the convex portion 34 moves from the side surface 23b of the concave portion 23 to the left, The directional growth films 34c grow upward from the bottom surface 23c of the recess 23, respectively. By simultaneously growing the laterally grown films 34a, 34b and the vertically grown film 34c from different growth surfaces, the grain boundary 39a is formed between the laterally grown film 34a and the vertically grown film 34c, and the grain boundary 39b is formed between the laterally grown film 34a and the vertically grown film 34c. These are generated between the horizontally grown film 34b and the vertically grown film 34c.

Since the horizontally grown films 34a and 34b do not grow from the vertically grown film 34c, the upper end of the dislocation line 41 (see FIG. 2) should be connected to the grain boundary 39 or located below the grain boundary 39. be able to.

As described above, the inclination angle θ3 of the grain boundary 39a correlates with the ratio of the growth rate of the horizontally grown film 34a to the growth rate of the vertically grown film 34c. In this embodiment, since the growth rate of the horizontally grown film 34a is faster than the growth rate of the vertically grown film 34c, the inclination angle θ3 is larger than 45 degrees. Similar to the inclination angle θ3, the inclination angle θ4 of the grain boundary 39b is larger than 45 degrees because the growth rate of the horizontally grown film 34b is faster than the growth rate of the vertically grown film 34c. . The grain boundaries 39 are convex portions in which the inner side is located higher than both the outer sides in the lateral direction (horizontal direction X). Since the grain boundaries 39a and 39b have opposite inclinations in the left-right direction X, the grain boundaries 39 have a triangular shape.

Since the length of the vertically grown film 34c along the thickness direction Z increases, that is, the thickness increases as the distance from the side surfaces 23a and 23b increases, inclined portions are formed at the grain boundaries 39a and 39b, respectively. When the vertically grown film 34c grows from the bottom surface 23c, dislocation lines 41 may be formed due to the dislocation lines 26 of the crystal layer 11.

The lateral growth film 34a and the lateral growth film 34b grow along the left-right direction X at the same time. The width of growth of the laterally grown film 34a along the left-right direction X correlates with the ratio of the growth rate of the laterally grown film 34a to the growth rate of the laterally grown film 34b. In this embodiment, since the growth rate of the laterally grown film 34a and the growth rate of the laterally grown film 34b are approximately the same, the width of the growth of the laterally grown film 34a in the left-right direction The width is about the same as the growth width of the groove 34b in the left-right direction X, and about half the width w1 of the recess 23. At this time, the laterally grown film 34a and the laterally grown film 34b meet within the internal space of the recess 23.

Note that after the crystal layer 12 is formed, known means such as polishing may be used to make the upper surface of the crystal layer 12 flat.

In step S4, the substrate 13 is removed, resulting in the crystal film 10 shown in FIG. 2. The substrate 13 is removed by known means such as polishing.

According to such a manufacturing method, the above-described crystal film 10 can be manufactured. Since a mask such as SiO2 is not used when forming the crystal layer 12, there is no need to remove the mask inside the crystal film. Since there is no partial loss of each crystal layer due to the removal of the mask, the yield is superior compared to the case where the mask is used.

Furthermore, the laterally grown film 34a and the laterally grown film 34b, which grow along the a-axis direction at a certain growth rate, can come together.

Since the width along the left-right direction X directly above the convex portion 24 can be narrowed, the width of the convex portion 24 along the left-right direction X can be shortened. Thereby, when the crystal layer 12 is formed, it is possible to reduce the number of dislocation lines 42 that appear due to the dislocation lines 26 in the convex portions 24. In addition, in the crystal layer 12 after formation and before the top surface is flattened, the position in the thickness direction Z of the top end of the crystal layer 12 on the convex portion 24 and the bottom end of the top surface of the crystal layer 12 on the concave portion 23 are also determined. It is possible to suppress the difference from the position in the thickness direction Z from increasing.

According to such a manufacturing method, the number of dislocation lines 41 in the vertically grown film 34c can be suppressed.

(Second embodiment)
In the first embodiment, the a-axis direction of the crystalline oxide semiconductor included in the crystal layer 11 is along the left-right direction X, but in the second embodiment, the a-axis direction of the crystalline oxide semiconductor included in the crystal layer 11 is An example of a crystal film 110 whose c-axis direction is along the left-right direction X will be described. Note that the description of the crystal film 110 having the same structure as the crystal film 10 of the first embodiment may be omitted.

In this embodiment, the a-axis direction of the crystalline oxide semiconductor included in the crystal layer 11 is along the front-back direction Y. The m-axis direction of the crystalline oxide semiconductor is along the thickness direction Z. In the second embodiment, the left-right direction X may be referred to as the c-axis direction, the front-rear direction Y may be referred to as the a-axis direction, and the thickness direction Z may be referred to as the m-axis direction.

FIG. 7 is a schematic perspective view illustrating the crystal film 110 according to the second embodiment. FIG. 8 is a schematic cross-sectional view illustrating the crystal film 110 according to the second embodiment, and is a cross-sectional view taken along the line XIII-XIII in FIG. As shown in FIGS. 7 and 8, the crystal layer 11 has uneven portions 122 arranged in the c-axis direction, for example, on the upper surface 21, which is one of the main surfaces. The uneven portion 122 has a stripe shape and extends along the a-axis direction. The uneven portion 122 has a concave portion 123 and a convex portion 124. The concave portion 123 and the convex portion 124 are adjacent to each other. Adjacent concave portions 123 and convex portions 124 are continuous at equal intervals along the c-axis direction.

The recess 123 has, for example, side surfaces 123a, 123b and a bottom surface 123c as growth surfaces on which the crystal layer 12 grows. The side surfaces 123a and 123b are crystal growth surfaces for lateral growth, and the bottom surface 123c is a crystal growth surface for vertical growth.

The side surfaces 123a and 123b are planes extending in the front-rear direction Y and the thickness direction Z. The side surfaces 123a and 123b are, for example, c-planes. The bottom surface 123c is a plane that extends in the front-rear direction Y and the left-right direction X. The bottom surface 123c is, for example, an m-plane. The bottom surface 123c is located between the side surfaces 123a and 123b. The side surface 123a is located on the left side of the bottom surface 123c, and the side surface 123b is located on the right side of the bottom surface 123c.

The ratio of the depth d2 of the recess 123 to the width w3 of the recess 123 is preferably such that the upper end of the film grown in the thickness direction Z from the bottom surface 123c is located below the upper surface of the crystal layer 12. It is more preferable that the range is within the range. The ratio of the depth d2 to the width w3 is preferably 0.12 or more and less than 2.0, more preferably 0.17 or more and less than 2.0. In this embodiment, for example, the ratio of the depth d2 to the width w3 is greater than or equal to any value within the range of 0.17 or more and 0.26 or less, and is a value within the range of 0.17 or more and 0.26 or less. Even more preferably.

The depth d2 of the recess 123 is preferably 0.5 μm or more. The depth d2 is, for example, 1.53 μm. The depth d2 refers to the length from the upper end to the lower end of the recess 123 in the thickness direction Z. In this embodiment, the depth d2 is equal to the height of the convex portion 124. The width w3 of the recess 123 may be determined as appropriate depending on the ratio to the depth d2. The width w3 is, for example, 4.5 μm. The width w3 is equal to the distance in the left-right direction X between the convex portions 124 adjacent to each other. In this embodiment, the value obtained by dividing half the length of the width w3 by the depth d2 is smaller than 4.

The convex portion 124 refers to, for example, the upper end portion of the crystal layer 11 where the concave portion 123 is not formed. The side surfaces of the convex portion 124 are common to the side surfaces 123a and 123b of the recessed portion 123. That is, the side surfaces 123a and 123b may be defined as the side surfaces of the convex portion 124.

The thickness of the crystal layer 11 is greater than or equal to the depth d2 of the recess 123.

In this embodiment, the crystal layer 12 is in contact with the uneven portion 122 of the crystal layer 11. The c-axis direction of the crystalline oxide semiconductor included in the crystal layer 12 is along the left-right direction X. The a-axis direction of the crystalline oxide semiconductor is along the front-back direction Y. The m-axis direction of the crystalline oxide semiconductor is along the thickness direction Z. That is, the plane orientation of the main surface of the crystal layer 12 is the m-plane in a region where the normal line is along the thickness direction Z.

The convex portion 134 of the crystal layer 12 formed in the internal space of the concave portion 123 of the crystal layer 11 is an epitaxially grown film grown from the growth surface of the concave portion 123. At this time, the convex portion 134 includes horizontally grown films 134a and 134b and a vertically grown film 134c. The laterally grown film 134a is a film grown laterally (c-axis direction) from the side surface 123a of the recess 123. The laterally grown film 134b is a film grown laterally (c-axis direction) from the side surface 123b of the recess 123. The direction of growth of the laterally grown film 134a is opposite to the direction of growth of the laterally grown film 134b. The vertically grown film 134c is a film grown in the thickness direction Z (vertical direction) from the bottom surface 123c, and the growth direction is upward. The vertically grown film 134c has a triangular shape in the cross section shown in FIG.

In this embodiment, the inclined portion is inclined from the c-axis direction. In this embodiment, the inclination angle θ3 of the grain boundary 39a and the inclination angle θ4 of the grain boundary 39b are approximately 63 degrees to 71 degrees.

In this embodiment, the ratio of the dimension of the grain boundary 39 along the thickness direction Z to the dimension along the left-right direction X (lateral direction) is within the range of 0.17 or more and 0.26 or less.

FIG. 31 shows an example of the crystal film 110 according to the second embodiment, in which α-Ga ₂ O ₃ is used as the first crystal layer (crystal layer 11) and the second crystal layer (crystal layer 12). This is a TEM (transmission electron microscope) image of a portion of a longitudinal section. FIG. 32 is a partially enlarged view of FIG. 31. Note that, like the cross section in FIG. 7, FIG. 31 shows a cross section extending along the left-right direction X and the thickness direction Z.

The side surfaces 123a and 123b of the recess 123 in FIG. 31 are c-planes, and the bottom surface 123c is m-plane. In this example, the depth d2 of the recess 123 is approximately 1.53 μm, the width w3 is approximately 4.55 μm, and the distance w2 is approximately 0.25 μm. In this example, the ratio of the depth d2 to the width w3 is about 0.34, and the ratio of the width w3 to the distance w2 is about 18. In this example, the inclination angle θ3 is approximately 71 degrees and the inclination angle θ4 is approximately 70 degrees.

Even with such a configuration, it is possible to obtain an excellent crystal film as in the first embodiment described above, and a crystal film in which dislocations extending along the thickness direction Z are reduced. Although FIG. 31 shows an example in which a structure in which the unevenness is arranged in the c-axis direction is actually manufactured, a structure in which the unevenness is arranged in the a-axis direction (first embodiment) is also shown in FIG. 31. An excellent crystalline film can be obtained in the same manner as in the case of this method. In this way, by establishing a specific relationship between the first crystal defect and the second crystal defect, a crystal film with reduced dislocations can be obtained.

(Method for manufacturing crystal film 110)
The crystal film 110 can be manufactured through the same steps S1 to S4 as the crystal film 10. In the crystal film 110, description of the same points as in the method for manufacturing the crystal film 10 of the first embodiment may be omitted.

In step S2, the uneven portion 122 is formed, for example, on the upper surface 21 of the crystal layer 11 stacked on the substrate 13 by etching or the like. Step S2 is an example of arranging stripe-like unevenness in the c-axis direction on the main surface of the first crystal layer containing a crystalline oxide containing gallium and having a corundum structure. In this embodiment, the recess 123 is formed such that, for example, the ratio of the depth d2 to the width w3 is within a range of 0.17 or more and 0.26 or less.

In step S3, the crystal layer 12 is laminated on the crystal layer 11 on which the uneven portions 122 are formed. Crystal layer 12 can be stacked in the same way as crystal layer 11.

In step S3, a convex portion 134 is formed as the crystal layer 12 in the internal space of the concave portion 123 of the crystal layer 11. As a result, uneven portions 132 are formed on the lower surface 31 of the crystal layer 12 in accordance with the shape of the uneven portions 122 of the crystal layer 11 .

At this time, the lateral growth film 134a of the convex portion 134 moves from the side surface 123a of the concave portion 123 to the right, and the lateral growth film 134b of the convex portion 134 moves from the side surface 123b of the concave portion 123 to the left, The directional growth films 134c grow upward from the bottom surface 123c of the recess 123, respectively. By simultaneously growing the laterally grown films 134a, 134b and the vertically grown film 134c from different growth surfaces, the grain boundary 39a is formed between the laterally grown film 134a and the vertically grown film 134c, and the grain boundary 39b is formed between the laterally grown film 134a and the vertically grown film 134c. These are generated between the horizontally grown film 134b and the vertically grown film 134c, respectively.

Since the laterally grown films 134a and 134b do not grow from the vertically grown film 134c, the upper ends of the dislocation lines 41 (see FIG. 7) either appear connected to the grain boundaries 39 or are located below the grain boundaries 39. It will appear as if it were located at .

The length of the vertically grown film 134c along the thickness direction Z increases as it moves away from the side surfaces 123a and 123b, that is, the thickness increases, so that inclined portions are formed at the grain boundaries 39a and 39b, respectively. When the vertically grown film 134c grows from the bottom surface 123c, dislocation lines 41 may be formed due to the dislocation lines 26 of the crystal layer 11.

According to such a manufacturing method, the above-described crystal film 110 can be manufactured. Since the width along the left-right direction X directly above the convex portion 124 can be narrowed, the width of the convex portion 124 along the left-right direction X can be shortened. Thereby, when the crystal layer 12 is formed, the number of dislocation lines 42 caused by the dislocation lines 26 in the convex portions 124 can be reduced. Further, the laterally grown film 34a and the laterally grown film 34b, which grow along the c-axis direction at a certain growth rate, can join together.

(Third embodiment)
In the above embodiment, an example including the crystal layer 11 and the crystal layer 12 has been described, but in the third embodiment, the crystal layer 211 is used instead of the crystal layer 11, and the crystal layer 12 is replaced with a crystal layer 211. An example of a crystalline film 210 in which a layer 212 is used and a crystalline layer 213 is provided on the crystalline layer 212 will be described. The crystal layer 213 has unevenness on its main surface that is shifted in the left-right direction X by about half a pitch from the unevenness on the main surface of the crystal layer 211 . Note that the description of the crystal film 210 having the same structure as the crystal film 10 of the first embodiment or the crystal film 110 of the second embodiment may be omitted. The crystal layer 212 is an example of a second crystal layer, and the crystal layer 213 is an example of a third crystal layer. The composition of the crystal layer 211 may be the same as the composition of the crystal layer 11, and the composition of the crystal layer 212 may be the same as the composition of the crystal layer 12.

FIG. 9 is a schematic perspective view illustrating a crystal film 210 according to the third embodiment. FIG. 10 is a schematic cross-sectional view illustrating a crystal film 210 according to the third embodiment. The crystal film 210 according to the third embodiment is used, for example, as a semiconductor film of a semiconductor device or the like. As shown in FIGS. 9 and 10, the crystal film 210 includes a crystal layer 211, a crystal layer 212 located on the crystal layer 211, and a crystal layer 213 located on the crystal layer 212. Note that the crystal film 210 shown in FIG. 9 may be, for example, a part of a disk-shaped crystal film.

(Crystal layer 211)
The crystal layer 211 is, for example, an n-type semiconductor layer. The crystal layer 211 is, for example, an epitaxial growth film that is heteroepitaxially grown on a sapphire substrate. The crystal layer 211 contains a crystalline oxide semiconductor as a main component. Note that the crystalline oxide semiconductor is an example of a crystalline oxide. The crystal layer 211 may be a film grown on a sapphire substrate via another layer such as a buffer layer.

The crystalline oxide semiconductor included in the crystal layer 211 has a corundum structure. In this embodiment, the plane orientation of the crystalline oxide semiconductor is arbitrary. The crystalline oxide semiconductor included in the crystal layer 211 includes gallium. The crystalline oxide semiconductor may be a metal oxide similar to the crystalline oxide semiconductor of the crystal layer 11.

Note that the "main component" means, for example, when the crystalline oxide semiconductor is Ga ₂ O ₃ , the atomic ratio of gallium among all the metal elements in the crystal layer 211 is 0.5 or more. This means that the layer 211 contains Ga ₂ O ₃ . In the present disclosure, the atomic ratio of gallium among all metal elements in the crystal layer 211 is preferably 0.7 or more, and more preferably 0.9 or more. Although the crystal layer 211 is single crystal in this embodiment, it may be polycrystalline.

The crystal layer 211 has stripe-shaped uneven portions 222 on the upper surface 221 (see FIG. 10). The uneven portion 222 extends, for example, along the front-rear direction Y. The uneven portion 222 has a recessed portion 223 and a convex portion 224. The concave portion 223 and the convex portion 224 are adjacent to each other. Adjacent recesses 223 and protrusions 224 are continuous along the left-right direction X at equal intervals. Note that the upper surface 221 refers to the upper surface of the main surface of the crystal layer 211.

The recess 223 is formed, for example, on the upper surface 221 by etching or the like. The recess 223 has a plurality of growth surfaces on which the crystal layer 212 grows. The recess 223 has, for example, side surfaces 223a, 223b and a bottom surface 223c as the growth surfaces. In this embodiment, the side surfaces 223a and 223b are crystal growth surfaces for lateral growth, and the bottom surface 223c is a crystal growth surface for vertical growth.

The side surfaces 223a and 223b are planes extending in the front-rear direction Y and the thickness direction Z. The bottom surface 223c is a plane that extends in the front-rear direction Y and the left-right direction X. The bottom surface 223c is located between the side surface 223a and the side surface 223b. The side surface 223a is located on the left side of the bottom surface 223c, and the side surface 223b is located on the right side of the bottom surface 223c. Note that the side surfaces 223a, 223b and the bottom surface 223c are part of the top surface 221.

The side surface 223a may have an angle θ5 of 60 degrees or more with the upper surface 225 of the convex portion 224. The angle θ5 between the side surface 223a and the top surface 225 is, for example, 90 degrees. The side surface 223b only needs to have an angle θ6 of 60 degrees or more with the top surface 225. The angle θ6 between the side surface 223b and the top surface 225 is, for example, 90 degrees. Note that in this embodiment, the top surface 221 and the bottom surface 223c are parallel. The angle between the side surfaces 223a, 223b and the bottom surface 223c is 90 degrees.

The ratio of the depth d3 of the recess 223 to the width w5 of the recess 223 is preferably such that the upper end of the film grown in the thickness direction Z from the bottom surface 223c is located below the upper surface of the crystal layer 212. It is more preferable that the range is within the range. It is more preferable that the ratio of the depth d3 to the width w5 is within a range of 0.125 or more and less than 2.0.

The depth d3 of the recess 223 refers to the length from the upper end to the lower end of the recess 223 in the thickness direction Z. In this embodiment, the depth d3 is equal to the height of the convex portion 224. The width w5 of the recess 223 refers to the length along the left-right direction X from the left end to the right end of the recess 223. The width w5 is equal to the distance in the left-right direction X between the convex portions 224 adjacent to each other. In this embodiment, the value obtained by dividing half the length of the width w5 by the depth d3 is smaller than 4.

It is preferable that the ratio of the width w5 of the recess 223 to the distance w6 between the adjacent recesses 223 is 1 or more. It is more preferable that the width w5 has a ratio of 1 to the distance w6. In this embodiment, the distance w6 is equal to the length along the left-right direction X from the left end to the right end of the upper surface of the convex portion 224.

The convex portion 224 refers to, for example, the upper end portion of the crystal layer 211 where the concave portion 223 is not formed. The side surfaces of the convex portion 224 are common to the side surfaces 223a and 223b of the recessed portion 223. That is, the side surfaces 223a and 223b may be defined as the side surfaces of the convex portion 224. Note that the upper surface 21 includes an upper surface 225 of the convex portion 224.

When the crystal layer 211 is an epitaxially grown film grown by heteroepitaxial growth, it may include dislocations along the thickness direction Z. The dislocations can be observed as dislocation lines 26 in a cross section of the crystal film 210 taken in the thickness direction Z, as shown in FIG. The cross section of the crystal layer 211 includes a plurality of dislocation lines 26. Each dislocation line 26 may be continuous, for example, from the lower surface 227 of the crystal layer 211 to the upper surface 225 of the convex portion 224 or the bottom surface 223c of the recessed portion 223.

(Crystal layer 212)
The crystal layer 212 is, for example, an n-type semiconductor layer. Crystal layer 212 is placed directly on crystal layer 211. The crystal layer 212 is in contact with the uneven portion 222 of the crystal layer 211 . Crystal layer 212 has the same conductivity type as crystal layer 211. The crystal layer 212 is, for example, an epitaxially grown film that is homoepitaxially grown on the crystal layer 211. The crystal layer 212 contains a crystalline oxide semiconductor as a main component. Note that the crystalline oxide semiconductor is an example of a crystalline oxide.

The crystalline oxide semiconductor included in the crystal layer 212 has a corundum structure. In this embodiment, the plane orientation of the crystalline oxide semiconductor is arbitrary. The crystalline oxide semiconductor included in the crystal layer 212 includes gallium. The crystalline oxide semiconductor may be a metal oxide similar to the crystalline oxide semiconductor of the crystal layer 12.

Note that the "main component" means, for example, when the crystalline oxide semiconductor is Ga ₂ O ₃ , the atomic ratio of gallium among all the metal elements in the crystal layer 212 is 0.5 or more. This means that the layer 212 contains Ga ₂ O ₃ . In the present disclosure, the atomic ratio of gallium among all metal elements in the crystal layer 212 is preferably 0.7 or more, and more preferably 0.9 or more. Although the crystal layer 212 is single crystal in this embodiment, it may be polycrystalline.

As shown in FIG. 10, the lower surface 231 of the crystal layer 212 is joined to the upper surface 221 of the crystal layer 211. The lower surface 231 and the upper surface 221 are also the interface between the crystal layer 212 and the crystal layer 211. The crystal layer 212 has, on the lower surface 231, an uneven portion 232 having a shape corresponding to the uneven portion 222 on the upper surface 221. That is, the uneven portion 232 has a stripe shape. The uneven portion 232 is in contact with the uneven portion 222. The uneven portion 232 has a concave portion 233 and a convex portion 234. In addition to the uneven portions 232 , the crystal layer 212 includes a region 243 directly above the convex portion 224 of the crystal layer 211 and a region 244 directly above the convex portion 234 . Note that the lower surface 231 refers to the lower surface of the main surface of the crystal layer 212.

The recess 233 is formed, for example, as a result of the formation of the protrusion 234. The inner space of the recess 233 is filled with the protrusion 224 . The crystal layer 212 located on the concave portion 233 is, for example, an epitaxial growth film grown on the upper surface 225 of the convex portion 224.

The convex portion 234 is formed in the internal space of the concave portion 223. The convex portion 234 is, for example, an epitaxially grown film grown from the growth surface of the concave portion 223. At this time, the convex portion 234 includes horizontally grown films 234a and 234b and a vertically grown film 234c. The laterally grown film 234a is a film grown laterally (left-right direction X) from the side surface 223a of the recess 223. The laterally grown film 234b is a film grown laterally (left-right direction X) from the side surface 223b of the recess 223. The direction of growth of the laterally grown film 234a is opposite to the direction of growth of the laterally grown film 234b. The vertically grown film 234c is a film grown in the vertical direction (thickness direction Z) from the bottom surface 223c, and the growth direction is upward. The vertically grown film 234c has a triangular shape in the cross section shown in FIG.

The convex portion 234 includes a grain boundary 37 within the concave portion 223, which is an interface between the laterally grown film 234a and the laterally grown film 234b. The grain boundaries 37 may appear as dislocations 38 in the crystal layer 212 above the recesses 223. In FIG. 10, a line indicating the grain boundary 37 and a line indicating the dislocation 38 are shown continuous with the line indicating the grain boundary 37.

It is preferable that the grain boundary 37 is located within the recess 223 in the left-right direction X. The position of the grain boundary 37 in the left-right direction X depends on the growth rate of the laterally grown film 234a and the laterally grown film 234b.

The convex portion 234 includes a grain boundary 39 in the concave portion 223, which is an interface between the horizontally grown films 234a, 234b and the vertically grown film 234c. The grain boundaries 39 include a grain boundary 39a that is an interface between the horizontally grown film 234a and the vertically grown film 234c, and a grain boundary 39b that is the interface between the horizontally grown film 234b and the vertically grown film 234c. has. As shown in FIG. 10, the grain boundaries 39a and 39b appear linear in a cross section cut in the thickness direction Z.

A plurality of grain boundaries 39 are arranged along the left-right direction X (horizontal direction), for example, depending on the number of recesses 223. The grain boundaries 39 have a triangular shape in the cross section shown in FIG. In this embodiment, the ratio of the dimension of the grain boundary 39 along the left-right direction X to the distance between adjacent grain boundaries 39 among the grain boundaries 39 arranged in the left-right direction X is 1 or more is preferred. It is more preferable that the size of the grain boundaries 39 along the left-right direction X has a ratio of 1 to the distance between adjacent grain boundaries 39 among the grain boundaries 39 arranged in the left-right direction X. Further, the distance between the grain boundaries 39 is equal to the distance w6 of the recess 223, but may be larger than the distance w6.

The vertically grown film 234c may include dislocations along the thickness direction Z. The dislocations are, for example, inherited dislocations along the thickness direction Z of the crystal layer 211 (dislocation lines 26 in FIG. 10). As shown in FIG. 10, dislocations in the vertically grown film 234c can be observed as dislocation lines 41 in a cross section of the crystal film 210 taken in the thickness direction Z. The cross section of the vertically grown film 234c includes a plurality of dislocation lines 41. In this embodiment, the dislocation line 41 is located within the recess 223.

The region 244 directly above the convex portion 234 is, for example, an epitaxially grown film grown from the upper surface 221 of the crystal layer 211. The length of the region 244 from the left end to the right end along the left-right direction X is equal to the width w3 of the recess 223.

The crystal layer 212 has stripe-shaped uneven portions 252 on the upper surface 251. Although the uneven portion 252 may extend in a direction different from that of the uneven portion 222, it extends, for example, along the front-rear direction Y, and preferably extends along the same direction as the uneven portion 222. The uneven portion 252 has a recessed portion 253 and a convex portion 254. The concave portion 253 and the convex portion 254 are adjacent to each other. The adjacent concave portions 253 and convex portions 254 are continuous along the left-right direction X at equal intervals. Note that the upper surface 251 refers to the upper surface of the main surface of the crystal layer 212.

The recess 253 is formed, for example, on the upper surface 251 by etching or the like. The recess 253 is located, for example, directly above the protrusion 224 of the crystal layer 211. The recess 253 only needs to vertically overlap at least a portion of the protrusion 224 , and it is preferable that the recess 253 be located so as to cover the entire protrusion 224 . It is preferable that the positions of the concave portion 253 and the convex portion 224 in the left-right direction X are the same. The recess 253 has a plurality of growth surfaces on which the crystal layer 213 grows. The recess 253 has, for example, side surfaces 253a, 253b and a bottom surface 253c as the growth surfaces. In this embodiment, the side surfaces 253a and 253b are crystal growth surfaces for lateral growth, and the bottom surface 253c is a crystal growth surface for vertical growth.

The side surfaces 253a and 253b are planes that extend in the front-rear direction Y and the thickness direction Z and are parallel to the side surfaces 223a and 223b of the crystal layer 211. The bottom surface 253c is a plane that extends in the front-rear direction Y and the left-right direction X. The bottom surface 253c is located between the side surfaces 253a and 253b. The bottom surface 253c is located directly above the top surface 225 of the convex portion 224 of the crystal layer 211. Note that the side surfaces 253a, 253b and the bottom surface 253c are part of the top surface 251.

The angle θ9 of the side surface 253a with the upper surface 255 of the convex portion 254 may be 60° C. or more. The angle θ9 between the side surface 253a and the top surface 255 is, for example, 90 degrees. The side surface 253b only needs to have an angle θ10 of 60 degrees or more with the top surface 255. The angle θ10 between the side surface 253b and the top surface 255 is, for example, 90 degrees. Note that in this embodiment, the top surface 255 and the bottom surface 253c are parallel. The angle between the side surfaces 253a, 253b and the bottom surface 253c is 90 degrees.

The ratio of the depth d4 of the recess 253 to the width w7 of the recess 253 is preferably such that the upper end of the film grown in the thickness direction Z from the bottom surface 253c is located below the upper surface of the crystal layer 213. It is more preferable that the range is within the range. It is more preferable that the ratio of the depth d4 to the width w7 is within a range of 0.125 or more and less than 2.0. The ratio between the depth d4 and the width w7 is, for example, the same as the ratio between the depth d3 and the width w5 of the recess 223, but may be different or may be a reciprocal. The width w7 is preferably the same as or larger than the width of the convex portion 224.

The depth d4 of the recess 253 refers to the length from the upper end to the lower end of the recess 253 in the thickness direction Z. In this embodiment, the depth d4 is equal to the height of the convex portion 254. The width w7 of the recess 253 refers to the length along the left-right direction X from the left end to the right end of the recess 253. The width w7 is equal to the distance in the left-right direction X between the convex portions 254 adjacent to each other. In this embodiment, the value obtained by dividing half the length of the width w7 by the depth d4 is smaller than 4.

It is preferable that the ratio of the width w7 of the recess 253 to the distance w8 between the adjacent recesses 223 is 1 or more. It is more preferable that the width w7 has a ratio of 1 to the distance w8. The ratio is, for example, the same as the ratio between the width w5 of the recess 223 and the distance w6. The distance w8 is equal to the length along the left-right direction X from the left end to the right end of the upper surface of the convex portion 254.

The convex portion 254 refers to, for example, the upper end portion of the crystal layer 212 where the concave portion 253 is not formed. The side surfaces of the convex portion 254 are common to the side surfaces 253a and 253b of the concave portion 253. That is, the side surfaces 253a and 253b may be defined as the side surfaces of the convex portion 254. Convex portion 254 may include dislocations 38 . Note that the upper surface 251 includes an upper surface 255 of the convex portion 254.

The region 243 directly above the convex portion 224 is, for example, an epitaxial growth film grown from the upper surface 225 of the convex portion 224. The length of the region 243 along the left-right direction X from the left end to the right end is equal to the length along the left-right direction X from the left end to the right end of the upper surface of the convex portion 224 . Region 243 is a vertically grown film. Region 243 may include dislocations along the thickness direction Z. The dislocations can be observed as dislocation lines 42, as shown in FIG. The number of dislocation lines 42 may increase as the width of the convex portion 224 increases.

(Crystal layer 213)
The crystal layer 213 is, for example, an n-type semiconductor layer. Crystal layer 213 is placed directly on crystal layer 212. The crystal layer 213 is in contact with the uneven portion 252 of the crystal layer 212. Crystal layer 213 has the same conductivity type as crystal layers 211 and 212. The crystal layer 213 is, for example, an epitaxially grown film that is homoepitaxially grown on the crystal layer 212. The crystal layer 213 contains a crystalline oxide semiconductor as a main component.

The crystalline oxide semiconductor included in the crystal layer 213 has a corundum structure. The crystalline oxide semiconductor has the same structure as the crystalline oxide semiconductor included in the crystal layers 211 and 212. In this embodiment, the plane orientation of the crystalline oxide semiconductor included in the crystal layer 213 is arbitrary. The composition of the crystalline oxide semiconductor included in the crystal layer 213 may be the same as that of the crystal layers 211 and 212.

As shown in FIG. 10, the lower surface 261 of the crystal layer 213 is joined to the upper surface 251 of the crystal layer 212. The lower surface 261 and the upper surface 251 are also the interface between the crystal layer 213 and the crystal layer 212. The crystal layer 213 has an uneven portion 262 on the lower surface 261, which has a shape corresponding to the uneven portion 252 on the upper surface 251. That is, the uneven portion 262 has a stripe shape. The uneven portions 262 may be arranged in a different direction from the uneven portions 222 of the crystal layer 211, but preferably they are arranged in the same direction. The uneven portion 262 is positioned offset from the uneven portion 222 by a half pitch in the left-right direction X.

The uneven portion 262 is in contact with the uneven portion 252. The uneven portion 262 has a recessed portion 263 and a convex portion 264. In addition to the uneven portion 262 , the crystal layer 213 includes a region 273 directly above the convex portion 254 of the crystal layer 212 and a region 274 directly above the convex portion 264 . Note that the lower surface 261 refers to the lower surface of the main surface of the crystal layer 213.

The recess 263 is formed, for example, as a result of the formation of the protrusion 264. The inner space of the recess 263 is filled with the protrusion 254 . The crystal layer 213 located on the concave portion 263 is, for example, an epitaxial growth film grown on the upper surface 255 of the convex portion 254. The recess 263 is placed in a position that vertically overlaps the recess 223 of the crystal layer 211 .

The convex portion 264 is formed in the internal space of the concave portion 253. The convex portion 264 is located at a position in the left-right direction X that vertically overlaps at least a portion of the convex portion 224 of the crystal layer 211 . In this embodiment, for example, the position of the convex portion 264 is such that it vertically overlaps all of the convex portions 224. The width of the protrusion 264 is preferably the same as or greater than the width of the protrusion 224.

The convex portion 264 is, for example, an epitaxially grown film grown from the growth surface of the concave portion 253. At this time, the convex portion 264 includes horizontally grown films 264a and 264b and a vertically grown film 264c. The laterally grown films 264a and 264b are located vertically overlapping the convex portion 224 of the crystal layer 211. The laterally grown film 264a is a film grown laterally (left-right direction X) from the side surface 253a of the recess 253. The laterally grown film 264b is a film grown laterally (left-right direction X) from the side surface 253b of the recess 253. The growth direction of the laterally grown film 264a is opposite to the growth direction of the laterally grown film 264b. The vertically grown film 264c is a film grown in the vertical direction (thickness direction Z) from the bottom surface 253c, and the growth direction is upward.

The convex portion 264 includes a grain boundary 237 within the concave portion 253, which is an interface between the laterally grown film 264a and the laterally grown film 264b. The grain boundaries 237 may appear as dislocations 238 in the crystal layer 213 above the recesses 253. In FIG. 10, a line indicating the grain boundary 237 and a line indicating the dislocation 238 are shown continuous with the line indicating the grain boundary 237. Although the boundary between the grain boundary 237 and the dislocation 238 does not have to be clear, in the present disclosure, for convenience, it is assumed to be at the same position in the thickness direction Z as the upper surface 255 of the convex portion 254. Note that the grain boundaries 237 and dislocations 238 do not need to be continuous. Further, the dislocation 238 may be continuous or intermittent in the front-rear direction Y. Note that although the grain boundaries 237 and dislocations 238 are schematically represented as straight lines in FIG. The portion may be a curved line. Note that the grain boundary 237 is an example of a third crystal defect.

The grain boundary 237 may be located within the recess 253 in the left-right direction X. The position of the grain boundary 237 in the left-right direction X depends on the growth rate of the laterally grown film 264a and the laterally grown film 264b. The position of the grain boundary 237 has the same relationship with the film growth rate as the position of the grain boundary 37 in the left-right direction X.

The convex portion 264 includes a grain boundary 269 in the concave portion 253, which is an interface between the horizontally grown films 264a, 264b and the vertically grown film 264c. The grain boundaries 269 are located vertically overlapping the convex portions 224 of the crystal layer 211. The grain boundaries 269 include a grain boundary 269a that is an interface between the horizontally grown film 264a and the vertically grown film 264c, and a grain boundary 269b that is the interface between the horizontally grown film 264b and the vertically grown film 264c. has. Note that the grain boundaries 269 and 269b are each an example of a second crystal defect.

A plurality of grain boundaries 269 are arranged along the left-right direction X (horizontal direction), for example, depending on the number of recesses 253. The grain boundaries 269 have a triangular shape in the cross section shown in FIG. Note that the grain boundary 269 is an example of a convex portion in which the inner side is located higher than both the outer sides in the lateral direction (left-right direction X).

In this embodiment, the ratio of the dimension of the grain boundary 269 along the left-right direction X to the distance between mutually adjacent grain boundaries 269 among the grain boundaries 269 arranged in the left-right direction is preferred. It is more preferable that the size of the grain boundaries 269 along the left-right direction X has a ratio of 1 to the distance between adjacent grain boundaries 269 among the grain boundaries 269 arranged in the left-right direction X. Further, the distance between the grain boundaries 269 is equal to the distance w8 of the recess 253, but may be larger than the distance w8.

In this embodiment, the grain boundary 269 is located above the grain boundary 39. That is, the plurality of grain boundaries 39 lined up in the left-right direction X and the plurality of grain boundaries 269 lined up in the left-right direction X are located in two levels, upper and lower. The grain boundaries 269 and the grain boundaries 39 are alternately located in the left-right direction X. It is preferable that the grain boundaries 269 and the grain boundaries 39 overlap in the left-right direction X when viewed from above, or are continuous without gaps.

As shown in FIG. 10, the grain boundaries 269a and 269b appear linearly in a cross section taken in the thickness direction Z. For example, the left end or lower end of the grain boundary 269a is located at the lower end of the side surface 253a or the left end of the bottom surface 253c. For example, the right end or the upper end of the grain boundary 269a is located directly above the center of the bottom surface 253c in the left-right direction X. For example, the right end or lower end of the grain boundary 269b is located at the lower end of the side surface 253b or the right end of the bottom surface 253c. For example, the left end or the upper end of the grain boundary 269b is located directly above the center of the bottom surface 253c in the left-right direction X. The right end or upper end of the grain boundary 269a is connected to the left end or upper end of the grain boundary 269b. Note that although the grain boundaries 269 are schematically represented as straight lines in FIG. 10, at least a portion thereof may be curved lines. Since the grain boundary 269a and the grain boundary 269b have opposite inclinations in the left-right direction X, the grain boundary 269 has a triangular shape.

The grain boundaries 269a are inclined with respect to the thickness direction Z and the left-right direction X so that the farther to the right from the side surface 253a, the higher the grain boundaries are located. The grain boundaries 269b are inclined with respect to the thickness direction Z and the left-right direction X so that the farther left from the side surface 253b, the higher the grain boundaries are located. The entire grain boundaries 269a and 269b may be sloped portions, or a portion thereof may be sloped portions. Note that the grain boundary 269 includes a plurality of inclined parts. In this embodiment, grain boundary 269 includes two slopes.

The grain boundary 269a has an inclination angle θ7 from the thickness direction Z. The inclination angle θ7 correlates with, for example, the ratio of the growth rate of the horizontally grown film 264a to the growth rate of the vertically grown film 264c. The inclination angle θ7 may be the same as the inclination angle θ3 of the grain boundary 39a. The grain boundary 269b has an inclination angle θ8 from the thickness direction Z. The inclination angle θ8 correlates with, for example, the ratio of the growth rate of the horizontally grown film 264b to the growth rate of the vertically grown film 264c. The inclination angle θ8 may be the same as the inclination angle θ4 of the grain boundary 39b.

The vertically grown film 264c may include dislocations along the thickness direction Z. The dislocations are, for example, inherited dislocations along the thickness direction Z of the crystal layer 212 (dislocation lines 42 in FIG. 10). As shown in FIG. 10, dislocations in the vertically grown film 264c can be observed as dislocation lines 271 in a cross section of the crystal film 210 taken in the thickness direction Z. The cross section of the vertically grown film 264c includes a plurality of dislocation lines 271. In this embodiment, the dislocation line 271 is located within the recess 253. The lower end of the dislocation line 271 is located at the lower end of the convex portion 264 . The upper end of the dislocation line 271 is connected to, for example, a grain boundary 269. The upper end of the dislocation line 271 may not be connected to the grain boundary 269 and may be located below the grain boundary 269. The vertically grown film 34c has a triangular shape in the cross section shown in FIG.

The region 274 directly above the convex portion 264 is, for example, an epitaxially grown film grown from the upper surface 251 of the crystal layer 212. The length of the region 274 from the left end to the right end along the left-right direction X is equal to the width w7 of the recess 253.

The thickness of the crystal layer 213 may be 1 μm or less, or 1 μm or more. In the embodiment of the present disclosure, the thickness of the crystal layer 213 is preferably 1 μm or more, and preferably 3 μm or more. The thickness of the crystal layer 213 is greater than or equal to the depth d4 of the recess 253. Note that the thickness of the crystal layer 213 refers to the length along the thickness direction Z from the lower end of the convex portion 264 to the upper surface 265 of the crystal layer 213 in the embodiment of the present disclosure.

Even with such a configuration, it is possible to obtain a crystal film in which dislocations extending along the thickness direction Z are reduced. In particular, in the region 273 of the crystal layer 213, dislocations extending along the thickness direction Z can be further reduced.

(Method for manufacturing crystal film 210)
An example of a method for manufacturing the crystal film 210 will be described below with reference to FIGS. 10 to 13. FIG. 11 is a diagram illustrating an overview of a method for manufacturing the crystal film 210.

As shown in FIG. 11, the method for manufacturing the crystal film 210 includes, for example, a step S11 of forming a crystal layer 211 on a substrate 13, a step S12 of forming an uneven portion 222 on an upper surface 221 of the crystal layer 211, and a step S12 of forming a crystal layer 211 on a substrate 13. Step S13 of forming the crystal layer 212 on the upper surface 221 of the layer 211, Step S14 of forming the uneven portion 252 on the upper surface 251 of the crystal layer 212, and Step S15 of forming the crystal layer 213 on the upper surface 251 of the crystal layer 212. and step S16 of removing the substrate 13. Note that steps S11 to S13 are the same as steps S1 to S3, and step S16 is the same as step S4, so a description thereof will be omitted.

As shown in FIG. 12, in step S14, the uneven portion 252 is formed, for example, on the upper surface 251 of the crystal layer 212 stacked on the crystal layer 211 by etching or the like. The method for forming the uneven portion 252 may be the same as the method for forming the uneven portion 22. The uneven portion 252 is located at a position where the recessed portion 253 vertically overlaps with the convex portion 224 of the crystal layer 211, and the convex portion 254 is located at a position where the recessed portion 223 of the crystal layer 211 vertically overlaps. The uneven portion 252 is formed to be shifted by a half pitch from the uneven portion 222.

As shown in FIG. 13, in step S15, the crystal layer 213 is laminated on the crystal layer 212 on which the uneven portions 252 are formed, for example, by a mist CVD method. Crystal layer 213 can be stacked in the same manner as crystal layers 211 and 212. Note that, like the crystal layers 211 and 212, the crystal layer 213 may be laminated on the crystal layer 212 by the known forming means. For example, the crystal layer 213 is formed of the same material and the same composition as the crystal layer 212. For example, the crystal layer 213 has the same conductivity type as the crystal layers 211 and 212, and is formed to be n-type.

At this time, the lateral growth film 264a of the convex portion 264 of the crystal layer 213 moves to the right from the side surface 253a of the concave portion 253 of the crystal layer 212, and the lateral growth film 264b of the convex portion 264 moves to the left from the side surface 253b of the concave portion 253 of the crystal layer 212. In this direction, the vertically grown film 264c of the convex portion 264 grows upward from the bottom surface 253c of the concave portion 253, respectively. By simultaneously growing the laterally grown films 264a, 264b and the vertically grown film 264c from different growth surfaces, the grain boundary 269a is formed between the laterally grown film 264a and the vertically grown film 264c, and the grain boundary 269b is formed between the laterally grown film 264a and the vertically grown film 264c. These are generated between the horizontally grown film 264b and the vertically grown film 264c, respectively.

Since the laterally grown films 264a and 264b do not grow from the vertically grown film 264c, the upper ends of the dislocation lines 271 (see FIG. 10) either appear connected to the grain boundaries 269 or are located below the grain boundaries 269. It will appear as if it were located at .

As described above, the inclination angle θ7 of the grain boundary 269a correlates with the ratio of the growth rate of the horizontally grown film 264a to the growth rate of the vertically grown film 264c. The inclination angle θ8 of the grain boundary 269b correlates with the ratio of the growth rate of the horizontally grown film 264b to the vertically grown film 264c. The grain boundary 269 becomes a convex portion in which the inner side is located higher than both the outer sides in the lateral direction (horizontal direction X). Since the grain boundary 269a and the grain boundary 269b have opposite inclinations in the left-right direction X, the grain boundary 269 has a triangular shape.

The length of the vertically grown film 264c along the thickness direction Z increases as the distance from the side surfaces 253a and 253b increases. That is, since the thickness increases, inclined portions are formed at each of the grain boundaries 269a and 269b. When the vertically grown film 264c grows from the bottom surface 253c, dislocation lines 271 may be formed due to the dislocation lines 42 of the crystal layer 212.

The lateral growth film 264a and the lateral growth film 264b grow along the left-right direction X at the same time. The width of growth of the laterally grown film 264a along the left-right direction X correlates with the ratio of the growth rate of the laterally grown film 264a to the growth rate of the laterally grown film 264b. At this time, the laterally grown film 264a and the laterally grown film 264b meet within the internal space of the recess 253.

Note that after the crystal layer 213 is formed, known means such as polishing may be used so that the upper surface 265 of the crystal layer 213 becomes flat.

According to such a manufacturing method, the above-described crystal film 210 can be manufactured. Since a mask such as SiO ₂ is not used when forming the crystal layers 212 and 213, there is no need to remove the mask inside the crystal film. Since there is no loss of a portion of each crystal layer due to removal of the mask, the yield is superior to the case where the mask is used. Even if the crystal layer 212 has dislocations caused by dislocations within the crystal layer 211, the dislocations in the crystal layer 213 caused by the dislocations can be reduced.

(Modification 1)
In the first embodiment, the angle θ1 between the side surface 23a and the upper surface 25 of the convex portion 24 was 90 degrees, but as shown in FIG. 14, the angle θ1 may be smaller than 90 degrees, for example, It may be 60 degrees. Similarly, in the first embodiment, the angle θ2 between the side surface 23b and the top surface 25 was 90 degrees, but as shown in FIG. 14, the angle θ2 may be smaller than 90 degrees, for example, 60 degrees. It may be degree.

(Modification 2)
In the first embodiment, the bottom surface 23c is a plane extending along the left-right direction X and the front-back direction Y, but as shown in FIG. It's okay. Note that in FIG. 15, the internal structure of the crystal layer 12 is omitted.

(Modification 3)
In the above embodiment, the substrate 13 is removed to form the crystal films 10, 110, 210, but the crystal films 10, 110, 210 may also include the substrate 13, for example, as shown in FIG. The crystal films 10, 110, and 210 may include the substrate 13. The crystal films 10, 110, and 210 including the substrate 13 are an example of a multilayer structure.

(Modification 4)
In the third embodiment, the crystal layer 213 is stacked on the crystal layer 212 with the uneven portion 252 formed on the upper surface 251, but the crystal layer 213 is stacked on the crystal layer 212 without the uneven portion 252 formed. It may be laminated. As shown in FIG. 16, in the crystal film of Modification Example 4, a portion of the crystal layer 213 that is at the same position as the convex portion 224 of the crystal layer 211 in the left-right direction X and the front-back direction Y is a laterally grown film 364a, 364b and a vertically grown film 364c.

The method for manufacturing a crystal film of Modification Example 4 does not include the step S14 of forming the uneven portions 262 on the upper surface 251 of the crystal layer 212, and after forming the crystal layer 213 (after step S15), forming the uneven portions 262 directly above the projecting portions 224 is not included. This step includes a step of removing a portion of the crystal layer 213 located therein by etching or the like, and a step of epitaxially growing laterally grown films 364a, 364b and a vertically grown film 364c between the remaining crystal layers 213. The removing step may be performed by a known method similarly to step S12 and step S14.

The lateral growth film 364a grows rightward from the side surface 353a of the crystal layer 213 left in the removal step. The side surface 353a is a plane that extends along the front-rear direction Y and the thickness direction Z and faces rightward. The lateral growth film 364b grows leftward from the side surface 353b of the crystal layer 213 left in the removal process. The side surface 353b is a plane that extends along the front-rear direction Y and the thickness direction Z and faces leftward. The vertically grown film 364c grows upward from the upper surface 353c of the crystal layer 212 exposed in the removal process.

The method of forming the horizontally grown films 364a, 364b and the vertically grown film 364c is the same as that of the horizontally grown films 264a, 264b and the vertically grown film 264c of the third embodiment. By simultaneously growing the laterally grown films 364a, 364b and the vertically grown film 364c from different growth surfaces, the grain boundary 369a is formed between the laterally grown film 364a and the vertically grown film 364c, and the grain boundary 369b is formed between the laterally grown film 364a and the vertically grown film 364c. These are generated between the horizontally grown film 364b and the vertically grown film 364c, respectively.

The horizontally grown films 364a and 364b do not grow from the vertically grown film 364c, so even if the vertically grown film 364c contains a dislocation line caused by the dislocation line 42 of the crystal layer 212, the upper end of the dislocation line is , appear connected to the grain boundary 369 (369a, 369b), or appear located below the grain boundary 369.

(Modification 5)
In the embodiments described above, the vertically grown films 34c, 134c, and 234c were included in the crystal films 10, 110, and 210; 134c and 234c may be removed to form the crystal films 10, 110, and 210 that do not include the portions. Note that, in the crystal films 10, 110, 210, a portion of the vertically grown films 34c, 134c, 234c is removed, or a portion upward from the lower surface 27 of the crystal layer 11, 211 is removed so as to leave the entire film. It's okay. The removal in Modification 5 may be performed together with the substrate 13 or after the substrate 13 is removed.

(Modification 6)
In the embodiments described above, the upper ends of the vertically grown films 34c, 134c, 234c, and 264c are located within the recesses 23, 123, 223, and 253; It may be located above the top surfaces 25, 225, 255 of 224, 254 and below the top surfaces of the crystal layers 12, 212, 213. Even with such a configuration, dislocations extending along the thickness direction Z are reduced.

FIG. 33 shows an example of the crystal film according to Modification Example 6, and is a TEM (transmission electron microscope) image of a part of the longitudinal section. FIG. 34 is a partially enlarged view of FIG. 33. The example in FIG. 33 is one of the modifications of the first embodiment. Note that, like the cross section in FIG. 2, FIG. 33 shows a cross section extending along the left-right direction X and the thickness direction Z. In FIG. 33, explanation will be made based on the configuration described in the first embodiment for convenience.

The side surfaces 23a and 23b of the recess 23 in FIG. 33 are the a-plane, and the bottom surface 23c is the m-plane, as in the first embodiment. In this example, the depth d1 of the recess 23 is about 1.51 μm, the width w1 is about 2.55 μm, and the distance w2 is about 0.6 μm. In this example, the ratio of depth d1 to width w1 is about 0.59, and the ratio of width w1 to distance w2 is about 4.3. In this example, the tilt angle θ3 is approximately 37 degrees, and the tilt angle θ4 is approximately 36 degrees.

(Application examples of crystal films 10, 110, 210)
The crystalline film is useful for semiconductor devices, especially power devices. Semiconductor devices formed using the crystal film include transistors such as MISFETs and HEMTs, TFTs, Schottky barrier diodes using semiconductor-metal junctions, JBSs, PN or PIN diodes combined with other P layers, and receivers. Examples include light emitting elements. In embodiments of the present disclosure, the crystal film can be peeled off from the crystal substrate, if desired, and used in a semiconductor device.

The semiconductor device may be either a horizontal element in which an electrode is formed on one side of a semiconductor layer (horizontal device) or a vertical element in which electrodes are formed on both the front and back sides of the semiconductor layer (vertical device). However, in the embodiment of the present disclosure, it is particularly preferable to use it for a vertical device. Suitable examples of the semiconductor device include, for example, a Schottky barrier diode (SBD), a junction barrier Schottky diode (JBS), a metal semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), and a metal oxide film. Examples include semiconductor field effect transistors (MOSFETs), static induction transistors (SITs), junction field effect transistors (JFETs), insulated gate bipolar transistors (IGBTs), and light emitting diodes (LEDs).

Hereinafter, a preferred example of the semiconductor device in which the crystal film of the present disclosure is applied to an n-type semiconductor layer (an n + type semiconductor layer, an n- type semiconductor layer, etc.) will be described using drawings. , but are not limited to these examples. Further, the semiconductor device according to the example may include, for example, a structure in which the crystal film of the present disclosure is an n+ type semiconductor layer and an n- type semiconductor layer is formed on the crystal film. Further, for example, at least a portion of the second crystal layer of the crystal film of the present disclosure may be used as an n-type semiconductor layer. With such a configuration, a semiconductor device with higher reliability can be obtained.

FIG. 17 shows an example of a Schottky barrier diode (SBD) according to an embodiment of the present disclosure. The SBD in FIG. 17 includes an n-type semiconductor layer 401a, an n+-type semiconductor layer 401b, a Schottky electrode 405a, and an ohmic electrode 405b.

The material of the Schottky electrode and the ohmic 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, Metals such as Pt, V, Mn, Ni, Cu, Hf, W, Ir, Zn, In, Pd, Nd or Ag, or alloys thereof, tin oxide, zinc oxide, rhenium oxide, indium oxide, indium tin oxide (ITO) ), metal oxide conductive films such as indium zinc oxide (IZO), organic conductive compounds such as polyaniline, polythiophene or polypyrrole, mixtures thereof, and laminates.

The Schottky electrode and the ohmic electrode can be formed by, for example, a known method such as a vacuum evaporation method or a sputtering method. More specifically, for example, when forming a Schottky electrode using two types of metals, a first metal and a second metal, a layer made of the first metal and a layer made of the second metal are formed. This can be done by laminating the layers and subjecting the layer made of the first metal and the layer made of the second metal to patterning using a photolithography technique.

When a reverse bias is applied to the SBD in FIG. 17, a depletion layer (not shown) spreads into the n-type semiconductor layer 401a, resulting in a high breakdown voltage SBD. Further, when a forward bias is applied, a current flows from the ohmic electrode 405b to the Schottky electrode 405a. In this way, the SBD using the semiconductor structure is excellent in high voltage and large current applications, has a fast switching speed, and is excellent in voltage resistance and reliability.

(HEMT)
FIG. 18 illustrates an example of a high electron mobility transistor (HEMT) according to an embodiment of the present disclosure. The HEMT in FIG. 18 includes a wide bandgap n-type semiconductor layer 421a, a narrow bandgap n-type semiconductor layer 421b, an n+ type semiconductor layer 421c, a semi-insulator layer 424, a buffer layer 428, a gate electrode 425a, a source electrode 425b, and A drain electrode 425c is provided.

(MOSFET)
FIG. 19 shows an example in which the semiconductor device of the present disclosure is a MOSFET. The MOSFET in FIG. 19 is a trench type MOSFET, which includes an n-type semiconductor layer 431a, n+-type semiconductor layers 431b and 431c, a p-type semiconductor layer 432, a gate insulating film 434, a gate electrode 435a, a source electrode 435b, and a drain electrode 435c. It is equipped with

(JFET)
FIG. 20 shows a junction field effect transistor (JFET) comprising an n-type semiconductor layer 441a, a first n+-type semiconductor layer 441b, a second n+-type semiconductor layer 441c, a gate electrode 445a, a source electrode 445b, and a drain electrode 445c. ) is shown below.

(IGBT)
FIG. 21 shows an insulator including an n-type semiconductor layer 451, an n-type semiconductor layer 451a, an n+-type semiconductor layer 451b, a p-type semiconductor layer 452, a gate insulating film 454, a gate electrode 455a, an emitter electrode 455b, and a collector electrode 455c. A suitable example of a gated bipolar transistor (IGBT) is shown.

(LED)
FIG. 22 shows an example in which the semiconductor device of the present disclosure is a light emitting diode (LED). The semiconductor light emitting device of FIG. 22 includes an n-type semiconductor layer 461 on a second electrode 465b, and a light-emitting layer 463 is stacked on the n-type semiconductor layer 461. A p-type semiconductor layer 462 is stacked on the light emitting layer 463. A light-transmitting electrode 467 that transmits light generated by the light-emitting layer 463 is provided on the p-type semiconductor layer 462, and a first electrode 465a is laminated on the light-transmitting electrode 467. Note that the semiconductor light emitting device shown in FIG. 22 may be covered with a protective layer except for the electrode portion.

Examples of the material for the transparent electrode include conductive oxide materials containing indium (In) or titanium (Ti). More specifically, examples thereof include In ₂ O ₃ , ZnO, SnO ₂ , Ga ₂ O ₃ , TiO ₂ , CeO _{2 ,} a mixed crystal of two or more of these, or a doped material thereof. By providing these materials by known means such as sputtering, a transparent electrode can be formed. Further, after forming the light-transmitting electrode, thermal annealing may be performed for the purpose of making the light-transmitting electrode transparent.

According to the semiconductor light emitting device of FIG. 22, the first electrode 465a is used as a positive electrode, the second electrode 465b is used as a negative electrode, and a current is passed through the p-type semiconductor layer 462, the light-emitting layer 463, and the n-type semiconductor layer 461 through them. This causes the light emitting layer 463 to emit light.

Examples of the materials for the first electrode 465a and the second electrode 465b include Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, Pt, V, Mn, Ni, Cu, Metals such as Hf, W, Ir, Zn, In, Pd, Nd or Ag, or alloys thereof, tin oxide, zinc oxide, rhenium oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), etc. Examples include a metal oxide conductive film, an organic conductive compound such as polyaniline, polythiophene, or polypyrrole, or a mixture thereof. The electrode film forming method is not particularly limited, and may include wet methods such as printing, spraying, and coating, physical methods such as vacuum evaporation, sputtering, and ion plating, CVD, and plasma CVD. It can be formed on the substrate according to a method appropriately selected from chemical methods such as methods, etc., taking into consideration compatibility with the material.

Note that another embodiment of the light emitting element is shown in FIG. In the light-emitting element of FIG. 23, an n-type semiconductor layer 461 is stacked on a substrate 469, and the n-type semiconductor layer 462, the light-emitting layer 463, and the n-type semiconductor layer 461 are exposed by cutting out parts of the layer 462, the light emitting layer 463, and the n-type semiconductor layer 461. A second electrode 465b is laminated on a portion of the exposed semiconductor layer surface of the layer 461.

FIG. 24 shows a junction barrier Schottky diode (JBS), which is one of the preferred embodiments of the present disclosure. The JBS in FIG. 24 includes an n-type semiconductor layer 401a, an n+-type semiconductor layer 401b, a p-type semiconductor layer 402, a Schottky electrode 405a, and an ohmic electrode 405b. In the embodiment of the present disclosure, the p-type semiconductor layers 402 are preferably provided at regular intervals, and the p-type semiconductor layers 402 are preferably provided between both ends of the Schottky electrode 405a and the n-type semiconductor layer 401a. It is more preferable that 402 is provided respectively. With such preferred embodiments, the JBS is configured to have better thermal stability and adhesion, further reduce leakage current, and further have better semiconductor properties such as withstand voltage.

The means for forming each layer of the semiconductor device in FIG. 24 is not particularly limited as long as it does not impede the purpose of the present disclosure, and may be any known means. For example, after forming a film by a vacuum evaporation method, a CVD method, a sputtering method, various coating techniques, etc., patterning is performed by a photolithography method, or a method is directly patterned by using a printing technique.

FIG. 25 shows a junction barrier Schottky diode (JBS), which is one of the preferred embodiments of the present disclosure. The semiconductor device of FIG. 25 differs from the semiconductor device of FIG. 24 in that a guard ring in which a large number of p-type semiconductor layers 423 are arranged is provided at the outer periphery of the barrier electrode. With this configuration, it is possible to obtain a semiconductor device with more excellent semiconductor characteristics such as withstand voltage.

A material with a high barrier height may be used for the guard ring. Examples of the material used for the guard ring include a conductive material having a barrier height of 1 eV or more, and may be the same as the electrode material. Further, the shape of the guard ring is not particularly limited, and examples thereof include a square shape, a circle shape, a U shape, an L shape, a band shape, and the like. The number of guard rings is also not particularly limited, but is preferably 3 or more, more preferably 6 or more.

(MOSFET)
FIG. 26 shows an n-type semiconductor layer 431a, a first n+-type semiconductor layer 431b, a second n+-type semiconductor layer 431c, a p-type semiconductor layer 432, a p+-type semiconductor layer 432a, a gate insulating film 434, a gate electrode 435a, A suitable example of a metal oxide semiconductor field effect transistor (MOSFET) including a source electrode 435b and a drain electrode 435c is shown. Note that the p + -type semiconductor layer 432a may be a p-type semiconductor layer, or may be the same as the p-type semiconductor layer 432. Note that the p-type semiconductor may be the same material as the n-type semiconductor and may contain a p-type dopant, or may be a different p-type semiconductor.

The above-described crystal film or semiconductor device of the present disclosure can be applied to power conversion devices such as inverters and converters in order to exhibit the above-described functions. More specifically, diodes built into inverters and converters, thyristors that are switching elements, power transistors, IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal-Oxide-Semiconductor Field Effects) ect Transistor) etc. can. FIG. 13 is a block configuration diagram showing an example of a control system using a semiconductor device according to an embodiment of the present disclosure, and FIG. 14 is a circuit diagram of the control system, which is particularly suitable for installation in an electric vehicle. It is a control system with

As shown in FIG. 27, the control system 500 includes a battery (power source) 501, a step-up converter 502, a step-down converter 503, an inverter 504, a motor (driven object) 505, and a drive control section 506, which are installed in an electric vehicle. It becomes. The battery 501 is composed of a storage battery such as a nickel metal hydride battery or a lithium ion battery, and stores electric power through charging at a power supply station or regenerated energy during deceleration, and is necessary for the operation of the electric vehicle's running system and electrical system. Can output DC voltage. The boost converter 502 is a voltage conversion device equipped with, for example, a chopper circuit, and boosts the DC voltage of, for example, 200 V supplied from the battery 501 to, for example, 650 V by the switching operation of the chopper circuit, and outputs it to a driving system such as a motor. be able to. The step-down converter 503 is also a voltage conversion device equipped with a chopper circuit, but by stepping down the DC voltage of, for example, 200V supplied from the battery 501 to, for example, about 12V, it can be used for power windows, power steering, or in-vehicle electrical equipment. It can be output to the electrical system including the following.

The inverter 504 converts the DC voltage supplied from the boost converter 502 into a three-phase AC voltage by a switching operation, and outputs it to the motor 505. The motor 505 is a three-phase AC motor that constitutes the running system of the electric vehicle, and is rotationally driven by three-phase AC voltage output from the inverter 504, and the rotational driving force is applied to the wheels of the electric vehicle via a transmission (not shown) or the like. to communicate.

On the other hand, using various sensors (not shown), actual values such as wheel rotation speed, torque, and accelerator pedal depression amount (accelerator amount) are measured from the running electric vehicle, and these measurement signals are sent to the drive control unit 506. is input. At the same time, the output voltage value of the inverter 504 is also input to the drive control section 506. The drive control unit 506 has the function of a controller including a calculation unit such as a CPU (Central Processing Unit) and a data storage unit such as a memory, and generates a control signal using the input measurement signal and sends it to the inverter 504. By outputting it as a feedback signal, the switching operation by the switching element is controlled. As a result, the alternating current voltage applied by the inverter 504 to the motor 505 is instantaneously corrected, so that driving control of the electric vehicle can be executed accurately, and safe and comfortable operation of the electric vehicle can be realized. Note that it is also possible to control the output voltage to the inverter 504 by providing a feedback signal from the drive control unit 506 to the boost converter 502.

FIG. 28 shows a circuit configuration excluding the step-down converter 503 in FIG. 27, that is, only the configuration for driving the motor 505. As shown in the figure, the semiconductor device of the present disclosure is used, for example, as a Schottky barrier diode in a boost converter 502 and an inverter 504 to perform switching control. The boost converter 502 is incorporated into a chopper circuit to perform chopper control, and the inverter 504 is incorporated into a switching circuit including an IGBT to perform switching control. Note that the current is stabilized by intervening an inductor (such as a coil) in the output of the battery 501, and by interposing a capacitor (such as an electrolytic capacitor) between the battery 501, boost converter 502, and inverter 504. Efforts are being made to stabilize the voltage.

Furthermore, as shown by the dotted line in FIG. 28, the drive control section 506 is provided with a calculation section 507 consisting of a CPU (Central Processing Unit) and a storage section 508 consisting of a nonvolatile memory. The signal input to the drive control section 506 is given to the calculation section 507, which performs necessary calculations to generate a feedback signal for each semiconductor element. Further, the storage unit 508 temporarily holds the calculation results by the calculation unit 507, stores physical constants, functions, etc. necessary for drive control in the form of a table, and outputs the table to the calculation unit 507 as appropriate. The arithmetic unit 507 and the storage unit 508 can have a known configuration, and their processing capacity can be arbitrarily selected.

As shown in FIGS. 27 and 28, in the control system 500, diodes and switching elements such as thyristors, power transistors, IGBTs, MOSFETs, etc. are used for switching operations of the boost converter 502, buck converter 503, and inverter 504. . By using gallium oxide (Ga ₂ O ₃ ), particularly corundum-type gallium oxide (α-Ga ₂ O ₃ ) as a material for these semiconductor elements, the switching characteristics are significantly improved. Furthermore, by applying the semiconductor device or the like according to the present disclosure, extremely good switching characteristics can be expected, and further miniaturization and cost reduction of the control system 500 can be realized. In other words, each of the boost converter 502, the buck converter 503, and the inverter 504 can be expected to benefit from the effects of the present disclosure, and any one of these, a combination of two or more, or a configuration including the drive control unit 506 can also be used. The effects of the present disclosure can be expected in any of the above.

Note that the above-mentioned control system 500 is applicable not only to the control system of an electric vehicle, but also to a control system for all kinds of purposes, such as boosting and buckling power from a DC power supply, and converting power from DC to AC. It is possible to apply it to It is also possible to use a power source such as a solar cell as the battery.

FIG. 29 is a block configuration diagram showing another example of a control system that employs the semiconductor device according to the embodiment of the present disclosure, and FIG. 30 is a circuit diagram of the control system, which is infrastructure equipment that operates with power from an AC power source. This is a control system suitable for installation in home appliances and home appliances.

As shown in FIG. 29, the control system 600 receives power supplied from an external, for example, three-phase AC power source (power source) 601, and includes an AC/DC converter 602, an inverter 604, a motor (to be driven) 605, It has a drive control unit 606, which can be installed in various devices (described later). The three-phase AC power supply 601 is, for example, a power generation facility of a power company (a thermal power plant, a hydroelectric power plant, a geothermal power plant, a nuclear power plant, etc.), and its output is supplied as an AC voltage while being stepped down through a substation. Ru. Alternatively, the power may be installed in a building or a nearby facility in the form of a private generator, for example, and supplied via a power cable. The AC/DC converter 602 is a voltage converter that converts an alternating current voltage to a direct current voltage, and converts the alternating current voltage of 100 V or 200 V supplied from the three-phase alternating current power supply 601 into a predetermined direct current voltage. Specifically, the voltage is converted to a commonly used desired DC voltage such as 3.3V, 5V, or 12V. When the driven object is a motor, conversion to 12V is performed. Note that it is also possible to use a single-phase AC power source instead of the three-phase AC power source, and in that case, the same system configuration can be achieved by using a single-phase input AC/DC converter.

The inverter 604 converts the DC voltage supplied from the AC/DC converter 602 into a three-phase AC voltage by a switching operation, and outputs it to the motor 605. The motor 605 has different forms depending on the object to be controlled, but it is used to drive wheels when the object to be controlled is a train, a pump or various power sources in the case of factory equipment, and a compressor etc. in the case of home appliances. It is a three-phase AC motor, and is rotationally driven by three-phase AC voltage output from the inverter 604, and transmits its rotational driving force to a drive target (not shown).

Note that, for example, in home appliances, there are many drive targets to which the DC voltage output from the AC/DC converter 602 can be directly supplied (for example, personal computers, LED lighting equipment, video equipment, audio equipment, etc.), and in such cases, The control system 600 does not require an inverter 604, and as shown in FIG. 29, DC voltage is supplied from the AC/DC converter 602 to the driven object. In this case, for example, a 3.3V DC voltage is supplied to a personal computer, and a 5V DC voltage is supplied to an LED lighting device.

On the other hand, actual measured values such as the rotational speed and torque of the driven object, or the temperature and flow rate of the surrounding environment of the driven object are measured using various sensors (not shown), and these measurement signals are input to the drive control unit 606. At the same time, the output voltage value of the inverter 604 is also input to the drive control section 606. Based on these measurement signals, the drive control unit 606 provides a feedback signal to the inverter 604 to control the switching operation of the switching element. As a result, the alternating current voltage applied by the inverter 604 to the motor 605 is instantaneously corrected, thereby making it possible to accurately control the operation of the driven object and realizing stable operation of the driven object. Further, as described above, when the drive target can be driven with a DC voltage, it is also possible to perform feedback control of the AC/DC converter 602 instead of feedback to the inverter.

FIG. 30 shows an example of the circuit configuration of FIG. 29. As shown in the figure, the semiconductor device of the present disclosure is used, for example, as a Schottky barrier diode in an AC/DC converter 602 and an inverter 604 to perform switching control. The AC/DC converter 602 uses, for example, a Schottky barrier diode circuit configured in a bridge shape, and performs DC conversion by converting and rectifying the negative voltage portion of the input voltage into a positive voltage. Further, the inverter 604 is incorporated into the switching circuit of the IGBT to perform switching control. Note that an inductor (such as a coil) is interposed between the three-phase AC power supply 601 and the AC/DC converter 602 to stabilize the current, and a capacitor (electrolytic capacitor) is inserted between the AC/DC converter 602 and the inverter 604. etc.) to stabilize the voltage.

Further, as shown by the dotted line in FIG. 30, the drive control section 606 is provided with a calculation section 607 consisting of a CPU and a storage section 608 consisting of a nonvolatile memory. The signal input to the drive control unit 606 is given to the calculation unit 607, which performs necessary calculations to generate feedback signals for each semiconductor element. Furthermore, the storage unit 608 temporarily holds the calculation results by the calculation unit 607, stores physical constants, functions, etc. necessary for drive control in the form of a table, and outputs the table to the calculation unit 607 as appropriate. The arithmetic unit 607 and the storage unit 608 can have a known configuration, and their processing capacity can be arbitrarily selected.

In such a control system 600, similarly to the control system 500 shown in FIGS. 27 and 28, diodes, switching elements such as thyristors, and power transistors are used for the rectification and switching operations of the AC/DC converter 602 and the inverter 604. , IGBT, MOSFET, etc. are used. By using gallium oxide (Ga ₂ O ₃ ), particularly corundum-type gallium oxide (α-Ga ₂ O ₃ ) as a material for these semiconductor elements, switching characteristics are improved. Furthermore, by applying the semiconductor film and semiconductor device according to the present disclosure, extremely good switching characteristics can be expected, and further miniaturization and cost reduction of the control system 600 can be realized. In other words, the effects of the present disclosure can be expected for each of the AC/DC converter 602 and the inverter 604, and the effects of the present disclosure can be achieved with either one or a combination of these, or with the drive control unit 606 as well. can be expected.

Note that in FIGS. 29 and 30, the motor 605 is illustrated as an object to be driven, but the object to be driven is not necessarily limited to something that operates mechanically, and can be many devices that require AC voltage. The control system 600 can be applied as long as it inputs power from an AC power source to drive a driven object, and can be applied to infrastructure equipment (for example, power equipment in buildings and factories, communication equipment, traffic control equipment, water and sewage treatment equipment, etc.). It can be installed for drive control of devices such as equipment, system equipment, labor-saving equipment, trains, etc.) and home appliances (e.g., refrigerators, washing machines, computers, LED lighting equipment, video equipment, audio equipment, etc.) can.

(Other variations)
In the above embodiment, the width w1 and the distance w2 of the recess 23 are the same in each recess 23, but may be different for each recess 23.

Each of the main surfaces and each growth surface may have an off-angle.

In the above embodiment, the crystal layers 11 and 211 are formed on the substrate 13, but a buffer layer or other layer may be provided between the substrate 13 and the crystal layers 11 and 211.

The conductivity type of each of the crystal layers 11, 12, 211, 212, and 213 may be n+ type or n- type.

In the above embodiment, the bottom surfaces 23c and 123c are m-planes, but may be c-planes or a-planes. In the example of the crystal films 10 and 110, when the bottom surfaces 23c and 123c are c-planes, the ratio of the depth d1 to the width w1 is greater than or equal to any value within the range of 1.0 or more and less than 2.0, The value is preferably in the range of 1.0 or more and less than 2.0. In the example of the crystal films 10 and 110, when the bottom surfaces 23c and 123c are a-planes, the ratio of the depth d2 to the width w3 is greater than or equal to any value within the range of 0.1 or more and 0.5 or less, The value is preferably within the range of 0.1 or more and 0.5 or less. The value obtained by dividing the half length of the widths w1 and w3 by the depths d1 and d2 is smaller than 4.

In the first embodiment or the second embodiment, the inclination angles θ3 and θ4 were within the range of approximately 36 degrees to 42 degrees or approximately 63 degrees to 71 degrees, but the inclination angles θ3 and θ4 were approximately 14 degrees to 76 degrees. degree, and may be about 14 degrees to 24 degrees and/or about 65 degrees to 76 degrees.

In the above embodiment, the axial directions of the crystalline oxide semiconductors included in the crystal layer 11 and the crystal layer 12 are along the same direction (left-right direction X, front-back direction Y, and thickness direction Z), but they are different. You can leave it there. Further, each axial direction of each crystalline oxide semiconductor may be within a range of ±10° from any one of the left-right direction X, the front-back direction Y, and the thickness direction Z described in the above embodiments. However, it is not limited to this. Further, in the above embodiments, the crystal planes such as the a-plane, c-plane, and m-plane may have an off-angle or may have no off-angle. If an off-angle is present, the off-angle is, for example, within a range of 0.1° to 10°.

(Test examples 1 to 12)
In Test Examples 1 to 12, an α-Ga ₂ O ₃ semiconductor film was epitaxially grown as an example of α-Ga ₂ O ₃ or its mixed crystal, and each combination of growth planes of the a-plane, c-plane, or m-plane was grown. Next, the ratio of growth rates between the horizontally grown film and the vertically grown film was calculated and evaluated. Film formation was performed using a mist CVD method. In Test Examples 1 to 6, the temperature during film formation was 550°C. In Test Examples 7 to 12, the temperature during film formation was 450°C. In each test example, the plane orientation of the growth plane of the horizontally grown film, the plane orientation of the growth plane of the vertically grown film, and the ratio of the growth rate of the obtained horizontally grown film to the vertically grown film are shown in Table 1. That's right. Note that each value in Table 1 is rounded to the fourth decimal place.

From the results of Test Examples 1 to 12, when the depth and width of the recess with the growth surface are within a specific range, the lateral growth film and the lateral growth film grow in opposite directions from both sides of the recess. It was found that they could meet in the internal space of the recess. That is, from the ratio of the growth rates on each growth surface of the horizontally grown film and the vertically grown film, if the depth and width of the recess are within a specific range, the thickness of the vertically grown film will be the same as the depth of the recess. It was found that the width of the laterally grown film along the left-right direction X becomes equal to half the width of the recess before it becomes equal to the width of the recess. In particular, if the value obtained by dividing the length of half the width of the recess by the depth of the recess is smaller than 4, the lateral growth film and the lateral growth film can be formed in the internal space of the recess regardless of the orientation of the growth surface. I found out that we can meet at

Further, from the results of Test Examples 1 to 12, in the first embodiment, the ratio of the depth d1 of the unevenness to the width w1 is preferably 0.125 or more and less than 2.0, and 0.57 or more and less than 2.0. It can be seen that a value less than 0 is preferable from the viewpoint of reducing dislocations. Further, in the first embodiment, the ratio of the dimension of the convex portion along the thickness direction to the dimension of the second crystal defect along the lateral direction of the convex portion is 0.57 or more and 0.69. It can be seen that the following is preferable from the viewpoint of reducing dislocations. Further, from the results of Test Examples 1 to 12, in the second embodiment, the ratio of the depth d2 of the unevenness to the width w3 is preferably 0.12 or more and less than 2.0, and 0.17 It can be seen that a value of less than 2.0 is preferable from the viewpoint of reducing dislocations. Further, in the second embodiment, the dimension of the second crystal defect along the thickness direction of the convex portion has a ratio of 0.17 or more to the dimension along the lateral direction of the convex portion of 0.17 or more and 0.26. It can be seen that the following is preferable from the viewpoint of reducing dislocations. These preferable ranges are new findings obtained through actual epitaxial growth.

Further, it can be seen that when the growth plane of the vertically grown film is the m-plane, the depth of the recess having the growth surface relative to the width of the recess is preferably a value of 0.17 or more and 0.69 or less. . From the viewpoint of dislocation reduction, the ratio of the dimension of the convex portion along the thickness direction to the dimension of the second crystal defect along the lateral direction of the convex portion is 0.17 or more and 0.69 or less. It turns out that this is preferable.

The value obtained by dividing half the width of the recess by the depth of the recess is within the range of 2.3 to 4, within the range of 2.0 to 2.9, or within the range of 1.2 to 1.4. Among these, examples include values below any value within the range of 0.8 to 0.9, within the range of 0.3 to 0.6, or within the range of 0.3 to 0.5.

Hereinafter, additional notes will be made regarding the above-mentioned embodiments.

(Additional note 1)
It has a corundum structure and contains a crystalline oxide containing gallium,
The cross section cut in the thickness direction has a linear first crystal defect extending along the thickness direction, and a linear second crystal defect including an inclined part inclined from the thickness direction,
The upper end of the first crystal defect is a crystal film that is connected to the sloped portion or located below the sloped portion.

(Additional note 2)
The second crystal defect has a convex portion in which the inner side is located higher than both outer sides in the lateral direction,
The crystal film according to supplementary note 1, wherein the convex portion includes a plurality of the inclined portions.

(Appendix 3)
The crystal film according to appendix 2, wherein the convex portion has a triangular shape.

(Additional note 4)
Supplementary Note 2 or 3. The crystal film according to 3.

(Appendix 5)
The crystal film has a plurality of the convex portions arranged in the lateral direction,
5. The crystal film according to any one of Supplementary Notes 2 to 4, wherein a dimension of the convex portions in the lateral direction has a ratio of 1 or more to a distance between the adjacent convex portions.

(Appendix 6)
The a-axis direction or c-axis direction of the crystalline oxide is perpendicular to the thickness direction,
The crystal film according to any one of Supplementary Notes 1 to 5, wherein the inclined portion is inclined from the a-axis direction or the c-axis direction.

(Appendix 7)
7. The crystalline film according to any one of Supplementary Notes 1 to 6, wherein the m-axis direction of the crystalline oxide is along the thickness direction.

(Appendix 8)
The cross section has a third crystal defect extending along the thickness direction,
8. The crystal film according to any one of Supplementary Notes 2 to 7, wherein the second crystal defect is connected to the third crystal defect at an upper end of the convex portion.

(Appendix 9)
The crystalline film according to appendix 8, wherein the portion extending along the thickness direction is a boundary between laterally grown films.

(Appendix 10)
The crystal film according to any one of Supplementary Notes 1 to 9, wherein the inclined portion is a boundary between a horizontally grown film and a vertically grown film.

(Appendix 11)
11. The crystal film according to any one of Supplementary Notes 1 to 10, wherein the slope angle of the slope with respect to the thickness direction is 36 degrees or more and 42 degrees or less, or 63 degrees or more and 71 degrees or less.

(Appendix 12)
The crystal film according to any one of Supplementary Notes 1 to 11, which is an epitaxially grown film.

(Appendix 13)
13. The crystal film according to any one of Supplementary Notes 1 to 12, wherein the epitaxially grown film has a laterally grown film above the second crystal defect.

(Appendix 14)
A plurality of the second crystal defects are arranged in a horizontal direction and are located in upper and lower two stages,
14. The crystal film according to any one of Supplementary Notes 1 to 13, wherein the crystal grain boundaries in the upper and lower stages are located alternately in the lateral direction.

(Appendix 15)
15. The crystal film according to any one of appendices 1 to 14, wherein the first crystal defect is a dislocation, and the second crystal defect is a grain boundary.

(Appendix 16)
The crystal film is
a first crystal layer having stripe-like unevenness on its main surface;
a second crystal layer located on the first crystal layer and in contact with the unevenness,
16. The crystal film according to any one of Supplementary Notes 1 to 15, wherein the inclined portion is included in the second crystal layer located within the recess of the first crystal layer.

(Appendix 17)
17. The crystal film according to any one of Supplementary Notes 1 to 16, which is an n-type semiconductor.

(Appendix 18)
18. The crystal film according to any one of Supplementary Notes 1 to 17, wherein the main surface is an m-plane.

(Appendix 19)
a sapphire substrate,
A multilayer structure comprising the crystal film according to any one of Supplementary Notes 1 to 18.

(Additional note 20)
providing a striped uneven portion on the main surface of a first crystal layer having a corundum structure and containing a crystalline oxide containing gallium;
A second crystal layer having a corundum structure and containing a crystalline oxide containing gallium is grown in the concave portion of the uneven portion, and at this time, in a cross section cut in the thickness direction, an inclined portion is inclined from the thickness direction. A method for manufacturing a crystal film that forms linear crystal defects.

10, 110, 210 Crystal film 11, 211 Crystal layer (an example of the first crystal layer)
12,212 Crystal layer (an example of the second crystal layer)
13 Substrate 21, 221 Top surface (an example of the main surface)
22, 122, 222, 252 Uneven portions 23, 123, 223, 253 Recesses 23a, 23b, 123a, 123b, 223a, 223b, 253a, 253b, 353a, 353b Side surfaces 23c, 123c, 223c, 253c, 353c Bottom surface 24, 124 , 224, 254 Convex portion 25, 225, 255 Upper surface 26 Dislocation line 27, 227 Lower surface 31, 231, 261 Lower surface 32, 132, 232, 262 Concave and convex portion 33, 233, 263 Concave portion 34, 134, 234, 264 Convex portion 34a , 34b, 134a, 134b, 234a, 234b, 264a, 264b, 364a, 364b Laterally grown film 34c, 134c, 234c, 264c, 364c Vertically grown film 37 Grain boundary (an example of third crystal defect)
38 Dislocation 39, 39a, 39b, 269, 269a, 269b, 369, 369a, 369b Grain boundary (an example of second crystal defect)
41,271 Dislocation line 42 Dislocation line 43, 44, 243, 244, 273, 274 Region 213 Crystal layer (an example of the third crystal layer)
251 Upper surface 265 Upper surface 401a N- type semiconductor layer 401b N+-type semiconductor layer 402 P-type semiconductor layer 405a Schottky electrode 405b Ohmic electrode 421a N-type semiconductor layer with wide band gap 421b N-type semiconductor layer with narrow band gap 421c N+-type semiconductor layer 423 p-type semiconductor layer 424 semi-insulator layer 425a gate electrode 425b source electrode 425c drain electrode 428 buffer layer 431a n-type semiconductor layer 431b first n+-type semiconductor layer 431c second n+-type semiconductor layer 432 p-type semiconductor layer 432a P+ type semiconductor layer 434 Gate insulating film 435a Gate electrode 435b Source electrode 435c Drain electrode 441a N- type semiconductor layer 441b First n+ type semiconductor layer 441c Second N+ type semiconductor layer 445a Gate electrode 445b Source electrode 445c Drain electrode 451 n N-type semiconductor layer 451a N-type semiconductor layer 451b N+-type semiconductor layer 452 P-type semiconductor layer 454 Gate insulating film 455a Gate electrode 455b Emitter electrode 455c Collector electrode 461 N-type semiconductor layer 462 P-type semiconductor layer 463 Light-emitting layer 465a First electrode 465b Second electrode 467 Transparent electrode 469 Substrate 500 Control system 501 Battery (power source)
502 Boost converter 503 Buck converter 504 Inverter 505 Motor (driving target)
506 Drive control section 507 Arithmetic section 508 Storage section 600 Control system 601 Three-phase AC power supply (power supply)
602 AC/DC converter 604 Inverter 605 Motor (driving target)
606 Drive control unit 607 Calculation unit 608 Storage unit d1, d2, d3, d4 Depth w1, w3, w5, w7 Width w2, w6, w8 Distance θ1, θ2, θ5, θ6, θ9, θ10 Angle θ3, θ4, θ7 ,θ8 Tilt angle

Claims

It has a corundum structure and contains a crystalline oxide containing gallium,
The cross section cut in the thickness direction has a linear first crystal defect extending along the thickness direction, and a linear second crystal defect including an inclined part inclined from the thickness direction,
The upper end of the first crystal defect is a crystal film that is connected to the sloped portion or located below the sloped portion.
The second crystal defect has a convex portion in which the inner side is located higher than both outer sides in the lateral direction,
The crystal film according to claim 1, wherein the convex portion includes a plurality of the inclined portions.
The crystal film according to claim 2, wherein the convex portion has a triangular shape.
3. The ratio of the dimension along the thickness direction of the convex portion to the dimension along the lateral direction of the convex portion is 0.57 or more and 0.69 or less, or 0.17 or more and 0.26 or less. The crystalline film described in .
The crystal film has a plurality of the convex portions arranged in the lateral direction,
4. The crystal film according to claim 3, wherein the ratio of the dimension of the convex portions in the lateral direction to the distance between the adjacent convex portions is 1 or more.
The a-axis direction or c-axis direction of the crystalline oxide is perpendicular to the thickness direction,
The crystal film according to claim 1, wherein the inclined portion is inclined from the a-axis direction or the c-axis direction.
The crystalline film according to any one of claims 1 to 5, wherein the m-axis direction of the crystalline oxide is along the thickness direction.
The cross section has a third crystal defect extending along the thickness direction,
6. The crystal film according to claim 2, wherein the second crystal defect is connected to the third crystal defect at an upper end of the convex portion.
The crystal film according to claim 8, wherein the portion extending along the thickness direction is a boundary between laterally grown films.
The crystal film according to any one of claims 1 to 5, wherein the inclined portion is a boundary between a horizontally grown film and a vertically grown film.　
The crystal film according to any one of claims 1 to 5, wherein the angle of inclination of the inclined portion with respect to the thickness direction is 36 degrees or more and 42 degrees or less, or 63 degrees or more and 71 degrees or less.
The crystal film according to any one of claims 1 to 5, which is an epitaxially grown film.
6. The crystal film according to claim 1, wherein the epitaxially grown film has a laterally grown film above the second crystal defect.
A plurality of the second crystal defects are arranged in a horizontal direction and are located in upper and lower two stages,
6. The crystal film according to claim 1, wherein the upper and lower crystal grain boundaries are alternately located in the lateral direction.
6. The crystal film according to claim 1, wherein the first crystal defect is a dislocation, and the second crystal defect is a grain boundary.
The crystal film is
a first crystal layer having stripe-like unevenness on its main surface;
a second crystal layer located on the first crystal layer and in contact with the unevenness,
6. The crystal film according to claim 1, wherein the inclined portion is included in the second crystal layer located within the recess of the first crystal layer.
The crystal film according to any one of claims 1 to 5, which is an n-type semiconductor.
The crystal film according to any one of claims 1 to 5, wherein the main surface is an m-plane.
a sapphire substrate,
A multilayer structure comprising the crystal film according to any one of claims 1 to 5.
providing a striped uneven portion on the main surface of a first crystal layer having a corundum structure and containing a crystalline oxide containing gallium;
A second crystal layer having a corundum structure and containing a crystalline oxide containing gallium is grown in the concave portion of the uneven portion, and at this time, in a cross section cut in the thickness direction, an inclined portion is inclined from the thickness direction. A method for manufacturing a crystal film that forms linear crystal defects.