Silicon carbide single-crystal substrate, silicon carbide epitaxy substrate and method for fabricating a silicon carbide semiconductor device

Abstract

Silicon carbide single-crystal substrate (10) comprising: a first principal surface (11); and an orientation flattening (31) extending in a <11-20> direction, wherein the first principal surface (11) has an end region (103) extending by at most 5 mm from an outer circumference of the first principal surface (11), and wherein, in a direction perpendicular to the first principal surface (11), a degree of curvature (101) of the end region (103) extending to the orientation flattening (31) is not greater than 3 µm, wherein, when viewed in the direction perpendicular to the first principal surface (11), a cross-section in the direction of the orientation flattening (31) divides the orientation flattening (31) perpendicularly into two equal sections, the end region (103) curves upwards in a direction away from a surface (13) opposite the first principal surface (11).and the degree of curvature (101) represents a distance between a contact point (7) between the orientation flat (31) and the first principal surface (11) and a point (6) at which a smallest square line (4), calculated from a cross-sectional profile (15) of the first principal surface (11) in a region (102) extending from a position 3 mm from the orientation flat (31) to a midpoint (5) of the first principal surface (11) to a position 5 mm from the orientation flat, intersects the orientation flat (31).

Description

Technical field The present invention relates to a silicon carbide single-crystal substrate, a silicon carbide epitaxy substrate and a method for producing a silicon carbide semiconductor device. State of the art Document JP 2014 - 170 891 A (PTD 1) discloses a method for epitaxial growth of a silicon carbide layer on a silicon carbide single crystal substrate. Document EP 3 010 034 A1 relates to a process for manufacturing a silicon carbide semiconductor device and corresponding device structures. It describes in particular the formation of a silicon carbide substrate with functional layers deposited on it to create a power device. A key focus is on the design and formation of insulating and oxide layers, especially a silicon dioxide layer, to improve the electrical properties of the device. The aim is, among other things, to optimize the reliability, breakdown strength, and electrical characteristics of the device. Document JP 2015-135902A concerns a control method, a control unit, and a circuit arrangement for a power converter, specifically for use in a railway vehicle. A first switching network of the power converter is connected to a supply branch that includes at least one inductive element, such as a transformer winding. Based on a dynamic current-voltage model of the supply branch, parameters are determined that depend on the self-inductance, mutual inductance, or resistance of the supply branch. The switching network is controlled according to these parameters, thereby achieving fast and precise control in both steady-state operation and transient processes. Summary of the invention A silicon carbide single-crystal substrate according to the present invention comprises a first principal surface and an orientation flattening. The orientation flattening extends in a <11-20> direction. The first principal surface comprises an end region extending at most 5 mm from an outer circumference of the first principal surface. In a direction perpendicular to the first principal surface, the curvature of the end region extending to the orientation flattening is not more than 3 µm. If a cross-section in the direction of the orientation flattening, viewed in the direction perpendicular to the first principal surface, divides the orientation flattening perpendicularly into two equal sections, the end region curves upward in a direction away from a surface opposite the first principal surface.The degree of curvature represents a distance between a contact point between the orientation flat and the first principal surface and a point where a smallest square line, calculated from a cross-sectional profile of the first principal surface in an area extending from a position 3 mm away from the orientation flat to a center point of the first principal surface to a position 5 mm away from the orientation flat, intersects the orientation flat. Brief description of the drawings Fig. 1 shows a schematic perspective view illustrating the setup of a silicon carbide single-crystal substrate according to the present embodiment. Fig. 2 shows a schematic top view illustrating the setup of the silicon carbide single-crystal substrate according to the present embodiment. Fig. 3 shows a diagram illustrating a first example of a relationship between the relative height of a first principal surface and a position on the first principal surface. Fig. 4 shows an enlarged view of region IV in Fig. 3. Fig. 5 shows a diagram illustrating a second example of a relationship between the relative height of the first principal surface and a position on the first principal surface. Fig. 6 shows a schematic diagram illustrating the setup of a device for measuring the relative height of the first principal surface of the silicon carbide single-crystal substrate.Figure 7 shows a schematic perspective view illustrating the setup of a silicon carbide epitaxy substrate according to the present embodiment. Figure 8 shows a schematic top view of a setup of a first modification of the silicon carbide single-crystal substrate according to the present embodiment. Figure 9 shows a schematic top view of a setup of a second modification of the silicon carbide single-crystal substrate according to the present embodiment. Figure 10 shows a schematic top view of a setup of a third modification of the silicon carbide single-crystal substrate according to the present embodiment. Figure 11 shows a schematic perspective view of a first step of a process for producing a silicon carbide single-crystal substrate according to the present embodiment.Figure 12 shows a schematic cross-sectional view of a second step of the process for producing a silicon carbide single-crystal substrate according to the present embodiment. Figure 13 shows a schematic perspective view of a third step of the process for producing a silicon carbide single-crystal substrate according to the present embodiment. Figure 14 shows a schematic cross-sectional view of a fourth step of the process for producing a silicon carbide single-crystal substrate according to the present embodiment. Figure 15 shows a schematic perspective view of a fifth step of the process for producing a silicon carbide single-crystal substrate according to the present embodiment. Figure 16 shows a schematic cross-sectional view of a sixth step of the process for producing a silicon carbide single-crystal substrate according to the present embodiment.Figure 17 shows a schematic cross-sectional view of a seventh step of the process for producing a silicon carbide single-crystal substrate according to the present embodiment. Figure 18 shows a schematic cross-sectional view of a process for producing a silicon carbide epitaxy substrate according to the present embodiment. Figure 19 shows a flowchart schematically illustrating a process for producing a silicon carbide semiconductor device according to the present embodiment. Figure 20 shows a schematic cross-sectional view illustrating a first step of the process for producing a silicon carbide semiconductor device according to the present embodiment. Figure 21 shows a schematic cross-sectional view illustrating a second step of the process for producing a silicon carbide semiconductor device according to the present embodiment.Figure 22 shows a schematic cross-sectional view representing a third step of the method for manufacturing a silicon carbide semiconductor device according to the present embodiment. Description of the embodiments [Overview of the embodiment of the present invention] First, an overview of one embodiment of the present invention is described. In the subsequent description, identical or corresponding elements have the same reference numerals, and their descriptions are not repeated. With regard to the crystallographic designation used herein, a single orientation, a group orientation, a single plane, and a group plane are each represented by [ ], < >, ( ) and {}. A crystallographically negative index is usually represented by a number with a bar “-” above it, wherein a number is provided with a negative sign. A silicon carbide single-crystal substrate 10 according to the present invention comprises a first main surface 11 and an orientation flattening 31. The orientation flattening 31 extends in a <11-20> direction. The first main surface 11 comprises an end region 103 extending by a maximum of 5 mm from an outer circumference 105 of the first main surface 11. In a direction perpendicular to the first main surface 11, the curvature 101 of the end region 103, extending to the orientation flattening 31, is not greater than 3 µm. A silicon carbide single-crystal substrate is typically obtained by cutting a silicon carbide single-crystal ingot with a wire saw. Ideally, when cutting the silicon carbide ingot with a wire saw, the wire saw is inserted substantially perpendicular to a side face of the silicon carbide single-crystal ingot. However, at the start of the cutting process, the angle of insertion of the wire saw relative to the side face of the silicon carbide single-crystal ingot is unstable, and it can happen that the wire saw is inserted obliquely into the side face. A carbon plane is physically easier to cut than a silicon plane. Thus, the wire saw tends to move in the direction of the carbon plane.Consequently, a cut surface of the silicon carbide single-crystal ingot (in other words, a front surface and a back surface of the cut silicon carbide single-crystal substrate) tends to be curved towards the carbon plane at the start of the cutting process. Thus, an outer edge of the front surface of the cut silicon carbide single-crystal substrate can curve upwards in a direction away from the back surface of the silicon carbide single-crystal substrate, or conversely, downwards in a direction towards the back surface. If, in particular, an end region of the front surface of the silicon carbide single-crystal substrate, extending to an orientation flat, is strongly curved (especially by more than 3 µm), a stacking fault tends to form from the orientation flat into a silicon carbide layer if the silicon carbide layer is formed by epitaxial growth on the silicon carbide single-crystal substrate. Therefore, it is desirable to reduce the degree of curvature of the end region (that is, the extent of upward or downward curvature), especially to 3 µm or less. As a result of their investigations, the inventors devised a method of placing a protective section in the form of a plate on the orientation flattening of a silicon carbide single-crystal ingot when cutting the ingot with a wire saw. They then proceed to cut the protective section first, followed by the silicon carbide single-crystal ingot. Although a cut surface of the protective section, which is cut first, may be curved with respect to a side face of the protective section, the cut surface will gradually become substantially perpendicular to that side face. Thus, the silicon carbide ingot cut after the protective section will be cut substantially perpendicular to its side face. Consequently, the degree of warping of the end region can be reduced. In particular, the degree of warping of the end region can be reduced to no greater than 3 µm.Consequently, a stacking fault that forms during the epitaxial growth of the orientation flattening in the silicon carbide layer can be reduced. If a cross-section in the direction of the orientation flat 31, viewed in the direction perpendicular to the first principal surface 11, divides the orientation flat 31 perpendicularly into two equal sections, the end region 103 bulges upwards in a direction away from a surface 13 opposite the first principal surface 11. The degree of curvature 101 can represent a distance between a contact point 7 between the orientation flat 31 and the first principal surface 11 and a point 6 where a least square line 4, calculated from a cross-sectional profile 15 of the first principal surface 11 in a region 102 extending from a position 3 mm away from the orientation flat 31 to a center point 5 of the first principal surface 11 to a position 5 mm away from that center point, intersects the orientation flat 31. [Details of the embodiment of the present invention] Details of the embodiment of the present invention are described below. (Silicon carbide single crystal substrate) First, the structure of a silicon carbide single-crystal substrate according to the present embodiment is described. As shown in Figs. 1 and 2, the silicon carbide single-crystal substrate 10 comprises the first main surface 11, a third main surface 13 opposite the first main surface 11, and a side end surface 30 located between the first main surface 11 and the third main surface 13. The side end surface 30 is formed from a planar orientation flat 31 and a curved curvature section 32. The orientation flat 31 extends in an <11-20> direction. The orientation flat 31 is substantially rectangular. A longitudinal direction of the orientation flat 31 is the <11-20> direction. A direction perpendicular to the orientation flat 31 can be a <1-100> direction. As shown in Fig. 2, when viewed in a direction perpendicular to the first principal surface 11, the end face 30 comprises the linear orientation flattening 31 and the arcuate curvature section 32. The center of a circumcircle of a triangle formed by any three points on the curvature section 32 can be defined as the center 5 of the first principal surface 11. The silicon carbide single-crystal substrate 10 (hereinafter abbreviated as "single-crystal substrate") is formed from a silicon carbide single crystal. The polytype of the silicon carbide single crystal is, for example, 4H-SiC. 4H-SiC exhibits higher electron mobility and dielectric strength compared to other polytypes. The silicon carbide single-crystal substrate 10 contains an n-type impurity, such as nitrogen (N). The silicon carbide single-crystal substrate 10 exhibits, for example, an n-type conductivity. The first principal surface 11 is, for example, a {0001} plane or a surface inclined at most 8° from the {0001} plane. If the first principal surface 11 is inclined from the {0001} plane, an inclination direction of a normal to the first principal surface 11 (a deviation direction) is, for example, the <11-20> direction. An inclination angle (deviation angle) from the {0001} plane is not less than 1° or not less than 2°. The deviation angle is not greater than 7° or not greater than 6°. The first principal surface 11 has a maximum diameter (a diameter) of, for example, not less than 100 mm. The maximum diameter is not less than 150 mm, not less than 200 mm, or not less than 250 mm. The upper limit of the maximum diameter is not restricted in any particular way. The upper limit of the maximum diameter may, for example, be set to 300 mm.If the first principal surface 11 is located on one side of a (0001) plane, the third principal surface 13 is located on one side of a (000-1) plane. Conversely, if the first principal surface 11 is located on the side of the (000-1) plane, the third principal surface 13 is located on the side of the (0001) plane. The first principal surface 11 comprises the end region 103 (a first end region), which extends at most 5 mm from the outer circumference 105 of the first principal surface 11 in the direction of the center point 5, and a middle region 104, which is surrounded by the end region 103. The end region 103 extends to the orientation flattening 31. The following describes the degree of curvature of the end region. Fig. 3 shows a cross-sectional profile 15 of the first principal surface 11 when considering a cross-section that perpendicularly divides the orientation flattening 31 into two equal sections when viewed in the direction perpendicular to the first principal surface 11. In Fig. 3, the y-axis shows a relative height of the first principal surface 11 and the x-axis shows a position on the first principal surface in a direction perpendicular to the orientation flattening 31. A method for measuring a relative height is described later. A first position 1 relates to a position at the center of an orientation flattening when viewed in the direction perpendicular to the first principal surface 11. A second position 2 relates to a position of the curvature section 32 relative to the first section 1 from the perspective of the center 5 of the first principal surface 11. As shown in Fig.As shown in Figure 3, in a cross-sectional view in the direction of the orientation flattening 31, the end section 103 can be curved upwards in a direction away from the third principal surface 13, which is opposite the first principal surface 11. The relative height of the first principal surface 11 can be lowest at the second position 2. The relative height of the first principal surface 11 can gradually increase from the second position 2 to the first position 1. Fig. 4 is an enlarged view of area IV in Fig. 3. The x-axis in Fig. 4 shows a distance from the orientation surface 31 in the direction perpendicular to the orientation flattening 31. A position 0 on the x-axis relates to the position of the orientation flattening 31. The smallest square line 4, calculated from the cross-sectional profile 15 of the first principal surface 11 in the area 102, which extends from a position 3 mm away from the orientation flattening 31 in the direction of the center of the first principal surface 11 to a position 5 mm away from it, is estimated. The degree of curvature 101 represents a distance between a point 6, where the smallest square line 4 intersects the orientation flattening 31, and a contact point 7 between the orientation flattening 31 and the first principal surface 11. The contact point 7 can be a highest position of the orientation flattening 31 in the direction perpendicular to the first principal surface 11.As shown in Fig. 5, in a cross-sectional view in the direction of the orientation flat 31, the end region 103 can be curved downwards in a direction towards the third principal surface 13, which is opposite the first principal surface 11. The x-axis in Fig. 5 shows a distance from the orientation flat 31 in the direction perpendicular to the orientation flat 31. Position 0 on the x-axis relates to the position of the orientation flat 31. The smallest square line 4, calculated from the cross-sectional profile 15 of the first principal surface 11 in the region 102 extending from a position 3 mm away from the orientation flat 31 in the direction of the center point 5 of the first principal surface 11 to a position 5 mm away from it, is estimated.The degree of curvature 101 represents a distance between a point 8, where the smallest square line 4 intersects a virtual plane 36 extending along the orientation flattening 31, and the contact point 7 between the orientation flattening 31 and the first principal surface 11. The contact point 7 can be a lowest position in the orientation flattening 31 in the direction perpendicular to the first principal surface 11. As previously described, in the direction of the outer circumference 105, the end region 103 can be convex upwards away from the third principal surface 13 of the silicon carbide single-crystal substrate 10, or conversely, convex downwards towards the third principal surface 13. The third principal surface 13 includes a second end region extending at most 5 mm from an outer circumference of the third principal surface 13. The second end region extends to the orientation flattening 31. If the first end region 103 is convex upwards, the second end region can be convex downwards. Conversely, if the first end region 103 is convex downwards, the second end region can be convex upwards. In the direction perpendicular to the first principal surface 11, the degree of curvature 101 of the first end region 103 is not greater than 3 µm. The curvature degree 101 is preferably not greater than 2 µm and even more preferably not greater than 1 µm.Similarly, in the direction perpendicular to the third principal surface 13, the degree of curvature 101 of the second end region cannot be greater than 3 µm, greater than 2 µm or greater than 1 µm. The following describes a method for measuring the degree of curvature. The degree of curvature can be measured, for example, using a Dyvoce series surface profiling system manufactured by Kohzu Precision Co., Ltd. As shown in Fig. 6, a surface profiling system 57 essentially comprises, for example, a laser displacement meter 50 and an xy-axis traversing stage 55. The laser displacement meter 50 essentially comprises a light-emitting element 51 and a light-receiving element 52. The light-emitting element 51 is, for example, implemented by a semiconductor laser. As shown in Fig. 6, the silicon carbide single-crystal substrate 10 is arranged on the xy-movement stage 55. The first principal surface 11 of the silicon carbide single-crystal substrate 10 is irradiated with incident light 53 from the light-emitting element 51. Reflected light 54 from the first principal surface 11 is detected by the light-receiving element 52. A distance from the laser displacement meter 50 to the first principal surface 11 can thus be measured. By moving the xy-movement stage 55 within a two-dimensional plane, a profile of the relative height of a surface along a radial direction of the first principal surface 11 can be measured. For example, an angle θ between a straight line 58, perpendicular to the first principal surface 11, and a direction of incidence of the incident light 53 is not less than 0° and not greater than 60°. If the angle is greater than 60°, the noise due to diffusion increases, particularly around the outer circumference of the first principal surface 11, and it becomes difficult to accurately measure a surface profile of the silicon carbide single-crystal substrate 10. According to the present embodiment, a surface profile around the outer circumference of the first principal surface 11 (in particular, a profile around a tangent 7 between the first principal surface 11 and the end face 30) can be accurately measured by setting the angle smaller. For example, the relative height of the first principal surface 11 is measured along line segment 3 in Fig. 2. The silicon carbide single-crystal substrate 10 is then moved, for example, 10 mm in the <11-20> direction using the xy-track 55. Subsequently, the relative height of the first principal surface 11 is measured along a line segment parallel to line segment 3. As described above, a profile of the relative height of the first principal surface 11 is measured at 10 mm intervals. The value of the curvature 101 of the end region 103, which extends to the orientation flattening 31, of no more than 3 µm means that the curvature 101 of the end region 103 is not greater than 3 µm at all measurement positions when the curvature 101 of the end region 103 is measured at measurement positions at the 10-mm distance in an extension direction of the orientation flattening 31 (that is, the <11-20> direction), when viewed in the direction perpendicular to the first principal surface 11. (Silicon carbide epitaxy substrate) The following describes the structure of a silicon carbide epitaxy substrate according to the present embodiment. As shown in Fig. 7, the silicon carbide epitaxy substrate 100 comprises the silicon carbide single-crystal substrate 10 and the silicon carbide layer 20. The silicon carbide layer 20 is arranged on the first main surface 11. The silicon carbide layer 20 comprises a fourth main surface 14, which is in contact with the first main surface 11, and a second main surface 12, which is opposite the fourth main surface 14. The second main surface 12 is free of a stacking defect extending in the <1-100> direction from the orientation flat 31 and having a length of not less than 1 mm. The second main surface is preferably free of a stacking defect having a length of not less than 1.5 mm, and more preferably free of a stacking defect having a length of not less than 2 mm.The length of a stacking fault is defined as a length in the <1-100> direction. The second principal area 12 can include a stacking fault extending from an area different from the orientation flattening 31, a stacking fault extending in a direction different from the <1-100> direction, or a stacking fault with a length of less than 1 mm. The silicon carbide layer 20 is an epitaxial layer formed by epitaxial growth. The silicon carbide layer 20 contains an n-impurity, such as nitrogen. The concentration of this n-impurity in the silicon carbide layer 20 can be lower than the concentration in the silicon carbide single-crystal substrate 10. The silicon carbide layer 20 forms the second main surface 12. The silicon carbide layer 20 can have a thickness of, for example, not less than 5 µm, not less than 10 µm, or not less than 15 µm. (Method for investigating stacking faults) The following describes a method for investigating a stacking fault. For example, a photoluminescence imaging device manufactured by Photon Design Corporation is used to investigate a stacking fault. When the second principal surface 12 of the silicon carbide epitaxy substrate 100 is irradiated with excitation light, photoluminescence is observed in the second principal surface 12. For example, white light is used as the excitation light. White light passes through, for example, a 313 nm bandpass filter and is emitted onto the second principal surface 12. The photoluminescence then passes through, for example, a 740 nm lowpass filter and reaches a light receiving element, such as a camera. As previously explained, a photoluminescence image of a measurement area on the second principal surface 12 is acquired. For example, by recording a photoluminescence image of the second principal surface 12 while the silicon carbide epitaxy substrate 100 is moved in a direction parallel to the second principal surface 12, the photoluminescence image is recorded over the entire second principal surface 12. White streaks extending linearly from the orientation flattening 31 are identified as stacking faults in the photoluminescence image. (First modification of the silicon carbide single crystal substrate) As shown in Fig. 8, an example is assumed in which the line segment 3, which perpendicularly divides the orientation flattening 31 into two equal sections, is divided into four equal sections when viewed in the direction perpendicular to the first principal surface 11 in the silicon carbide single-crystal substrate 10. The first principal surface 11 includes a lower region 41 extending from the orientation flattening 31 to a position 44 corresponding to 1 / 4 of the line segment 3. The line segment 3 is located on the first principal surface 11. The line segment 3 passes through the center point 5 of the first principal surface 11. The position 44 defines a line segment perpendicular to the line segment 3.Position 44 is located at a position that is a distance from the first position 1 by a length corresponding to ¼ of line segment 3, which represents a contact point between line segment 3 and orientation surface 31 when line segment 3 is divided into four equal sections. Viewed in the direction perpendicular to the first principal surface 11, the curved section 32, which has an arc shape, comprises a lower arc section 33, a middle arc section 34, and an upper arc section 35. The middle arc section 34 is located between the lower arc section 33 and the upper arc section 35. The lower arc section 33 is formed by the lower region 41. The degree of curvature 101 of the end region 103, which extends to the end section 33 of the lower region 41, is not greater than 3 µm. The value of the curvature 101 of the end region 103 of not greater than 3 µm means that the curvature degree 101 of the end region 103 is not greater than 3 µm at all measurement positions when the curvature degree 101 of the end region 103 is measured at measurement positions at the 10 mm distance in one direction along the end section 33 when viewed in the direction perpendicular to the first principal surface 11.The curvature degree 101 of the end region 103 is preferably not greater than 2 µm, and even more preferably not greater than 1 µm. (First modification of the silicon carbide epitaxy substrate) As shown in Fig. 7, the silicon carbide epitaxy substrate 100 according to a first modification comprises the silicon carbide single-crystal substrate 10 according to the first modification and the silicon carbide layer 20. The silicon carbide layer 20 is arranged on the first principal surface 11. The silicon carbide layer 20 comprises the fourth principal surface 14, which is in contact with the first principal surface 11, and the second principal surface 12, which is opposite the fourth principal surface 14. The second principal surface 12 is free of a stacking defect extending in the <1-100> direction from the end section 33 of the lower region 41 and having a length of not less than 1 mm.The second principal area 12 may include a stacking fault that is distinct from an area that differs from the end section 33 of the lower area 41, a stacking fault that extends in a direction different from the <1-100> direction, or a stacking fault with a length of less than 1 mm. (Second modification of the silicon carbide single crystal substrate) As shown in Fig. 9, an example is assumed in which the line segment 3, which divides the orientation flattening 31 perpendicularly into two equal sections, is subdivided into four equal sections in the silicon carbide single-crystal substrate 10 when viewed in the direction perpendicular to the first principal surface 11. The first principal surface 11 comprises an upper region 43 extending from an end section 35 opposite the orientation flattening 31 to a position 45 corresponding to 1 / 4 of the line segment. The line segment 3 is located on the first principal surface 11. The line segment 3 passes through the midpoint 5 of the first principal surface 11. The position 45 defines a line segment perpendicular to the line segment 3.Position 45 is located at a position that is a distance of ¼ of line segment 3 from the second position 2, which represents a contact point between line segment 3 and end section 35, if line segment 3 is divided into four equal sections. Viewed in the direction perpendicular to the first principal surface 11, the curved section 32, which has an arc shape, comprises the lower arc section 33, the middle arc section 34, and the upper arc section 35. The middle arc section 34 is located between the lower arc section 33 and the upper arc section 35. The upper arc section 35 is formed by the upper region 43. The degree of curvature 101 of the end region 103, which extends to the end section 35 of the upper region 43, is not greater than 3 µm.A curvature value 101 of the end region 103, extending to the end section 35 of the upper region 43, of no more than 3 µm means that the curvature 101 of the end region 103 is no greater than 3 µm at all measurement positions when measured at 10 mm intervals in one direction along the end section 35, viewed perpendicular to the first principal surface 11. The curvature 101 of the end region 103 is preferably no greater than 2 µm, and more preferably no greater than 1 µm. (Second modification of the silicon carbide epitaxy substrate) As shown in Fig. 7, the silicon carbide epitaxy substrate 100 according to a second modification comprises the silicon carbide single-crystal substrate 10 according to the second modification and the silicon carbide layer 20. The silicon carbide layer 20 is arranged on the first principal surface 11. The silicon carbide layer 20 comprises the second principal surface 12, which is opposite the surface 14 that is in contact with the first principal surface 11. The second principal surface 12 is free of a stacking fault extending in the <1-100> direction from the end section 35 of the upper region 43 and having a length of not less than 1 mm. The second principal surface 12 may include a stacking fault extending from a region different from the end section 35 of the upper region 43, a stacking fault extending in a direction different from the <1-100> direction, or a stacking fault with a length of less than 1 mm. (Third modification of the silicon carbide single crystal substrate) As shown in Fig. 10, an example is assumed in which the line segment 3, which perpendicularly divides the orientation flat 31 into two equal sections, is, when viewed in the direction perpendicular to the first principal surface 11, subdivided into four equal sections in the silicon carbide single-crystal substrate 10 according to a third embodiment. The first principal surface 11 comprises the lower region 41, which extends from the orientation flat 31 to position 44, corresponding to 1 / 4 of the line segment, and the upper region 43, which extends from the end section 35 opposite the orientation flat 31 to position 45, corresponding to 1 / 4 of the line segment. The line segment 3 is arranged on the first principal surface 11. The line segment 3 passes through the midpoint 5 of the first principal surface 11. Position 44 defines a line segment perpendicular to the line segment 3.Position 44 is located a distance of 1 / 4 of line segment 3 from the first position 1, which represents the contact point between line segment 3 and orientation flattening 31 when line segment 3 is divided into four equal sections. Position 45 is located a distance of 1 / 4 of line segment 3 from the second position 2, which represents the contact point between line segment 3 and end section 35 when line segment 3 is divided into four equal sections. When viewed in the direction perpendicular to the first principal surface 11, the arc-shaped curvature section 32 comprises the lower arc section 33, the middle arc section 34, and the upper arc section 35. The middle arc section 34 is located between the lower arc section 33 and the upper arc section 35. The upper arc section 35 is formed by the upper region 43. The lower arc section 33 is formed by the lower region 41. The curvature 101 of the end region 103, extending to the end section 33 of the lower region 41, is not greater than 3 µm. A curvature 101 value of not more than 3 µm for the end region 103 extending to the end section 33 of the lower region 41 means that the curvature 101 of the end region 103 is not greater than 3 µm at all measurement positions when measured at 10 mm intervals in one direction along the end section 33, viewed in the direction perpendicular to the first principal surface 11. The curvature 101 of the end region 103 is preferably not greater than 2 µm, and even more preferably not greater than 1 µm. The curvature 101 of the end region 103, extending to the end section 35 of the upper region 43, is not greater than 3 µm. A curvature 101 value of not more than 3 µm for the end region 103 extending to the end section 35 of the upper region 43 means that the curvature 101 of the end region 103 is not greater than 3 µm at all measurement positions when measured at 10 mm intervals in a direction along the end section 35, viewed in the direction perpendicular to the first principal surface 11. The curvature 101 of the end region 103 is preferably not greater than 2 µm, and even more preferably not greater than 1 µm. (Third modification of the silicon carbide epitaxy substrate) As shown in Fig. 7, the silicon carbide epitaxy substrate 100 according to a third modification comprises the silicon carbide single-crystal substrate 10 according to the third modification and the silicon carbide layer 20. The silicon carbide layer 20 is arranged on the first main surface 11. The silicon carbide layer 20 comprises the second main surface 12 opposite the surface 14, which is in contact with the first main surface 11. The second main surface 12 is free of a stacking defect extending in the <1-100> direction from the end section 33 of the lower region 41 and having a length of not less than 1 mm, and free of a stacking defect extending in the <1-100> direction from the end section 35 of the upper region 43 and having a length of not less than 1 mm.The second principal area 12 may include a stacking fault extending from a region different to the end section 35 of the upper region 43 and the end region 33 of the lower region 41, a stacking fault extending in a direction different to the <1-100> direction, or a stacking fault with a length of less than 1 mm. (Process for the production of the silicon carbide single crystal substrate) The following describes a method for producing a silicon carbide single-crystal substrate according to the present embodiment. A silicon carbide single-crystal ingot 80 of the 4H polytype is produced, for example, by a sublimation process. As shown in Fig. 11, the silicon carbide single-crystal ingot 80 comprises a top surface 81, a bottom surface 82, and a side surface 83. The side surface 83 is located between the top surface 81 and the bottom surface 82. The side surface 83 extends continuously to the top surface 81 and continuously to the bottom surface 82. The top surface 81 is, for example, convexly curved. The bottom surface 82 is, for example, substantially flat and substantially annular. In a cross-sectional view, the side surface 83 has a width that increases from the bottom surface 82 towards the top surface 81. When produced by the sublimation process using a crucible, the top surface 81 faces a silicon carbide starting material, and the bottom surface 82 faces a nucleation substrate. The silicon carbide single-crystal ingot 80 is then formed. In particular, a first grinding stone 61 and a second grinding stone 62 are prepared. The first grinding stone 61 is positioned so that it faces the side surface 83. The second grinding stone 62 is positioned so that it faces the upper surface 81. The lower surface 82 of the silicon carbide single-crystal ingot 80 is attached to a holder 65. The holder 65 is, for example, made of stainless steel. By rotating the holder 65 about a pivot axis 67, the silicon carbide single-crystal ingot 80, which is attached to the holder 65, is rotated. When the first grinding stone 61 is pressed against the side surface 83 of the silicon carbide single-crystal ingot 80 while the silicon carbide single-crystal ingot 80 is rotated, the side surface 83 is ground.Similarly, when the second grinding stone 62 is pressed against the upper surface 81 of the silicon carbide single-crystal ingot 80 while the silicon carbide single-crystal ingot 80 is rotated, the upper surface 81 is ground. The silicon carbide single-crystal ingot 80 is thus formed into a substantially columnar shape (see Fig. 13). The silicon carbide single-crystal ingot 80 has a substantially annular upper surface 81, a substantially annular lower surface 82, and a substantially cylindrical side surface 83. The holder 65 is removed from the lower surface 82 of the silicon carbide single-crystal ingot 80. A holder 71 is then attached to the lower surface 82 of the silicon carbide single-crystal ingot 80. While the silicon carbide single-crystal ingot 80 is attached to the holder 71 in a resting state, a third grinding stone 68 is pressed against the side surface 83 of the silicon carbide single-crystal ingot. As the third grinding stone 68 is pressed against it in a direction 70, indicated by an arrow, while performing a back-and-forth motion along a direction 69 parallel to the side surface 83, the side surface 83 is ground. An orientation flat 84 is thus formed in the silicon carbide single-crystal ingot 80 (see Fig. 15). The side surface 83 is defined by the planar orientation flat 84 and by a curved surface section 85. The orientation flat 84 is essentially rectangular. A protective section 92 is then attached to the orientation flat 84. The protective section 92 is designed to cover the entire flat orientation flat 84 (see Fig. 16). The protective section 92 is attached to the orientation flat 84, for example, with an adhesive. Although the shape of the protective section 92 is not limited to any specific form, it may, for example, be in the shape of a plate. Silicon carbide is used, for example, as a material for the protective section 92. The protective section 92 can be made of monocrystalline or polycrystalline silicon carbide. The protective section 92 in the form of a plate has a thickness of, for example, not less than 10 mm. As shown in Fig. 16, the silicon carbide single-crystal ingot 80 is held on a base 91, while the orientation flat 84 is covered by the protective section 92. A surface 96 of the base 91 is formed with a recess 95 having an arc shape. The curved surface section 85 of the side face 83 of the silicon carbide single-crystal ingot 80 is positioned in the recess 95. The silicon carbide single-crystal ingot 80 is, for example, attached to the base 91 with an adhesive. The orientation flat 84 of the silicon carbide single-crystal ingot 80 is inclined with respect to the surface 96 of the base 91. The protective section 92 can be positioned away from the surface 96. The silicon carbide single-crystal ingot 80 is then cut. As shown in Fig. 17, a wire saw 93 is positioned on one side opposite the base 91 from the perspective of the silicon carbide single-crystal ingot 80. When the base 91 moves in a direction 94, as indicated by an arrow, while the wire saw 93 oscillates, the silicon carbide single-crystal ingot 80 is cut by the wire saw 93. Several wire saws 93 can be aligned in a direction perpendicular to the upper surface 81. The wire saw 93 touches the guard section 92 before coming into contact with the silicon carbide single-crystal ingot 80. After part of the guard section 92 has been cut, the wire saw 93 begins to cut the silicon carbide single-crystal ingot 80. When cutting the silicon carbide single-crystal ingot 80 with the wire saw 93, the wire saw 93 is inserted essentially perpendicularly into the side face 83 of the silicon carbide single-crystal ingot 80. However, at the beginning of the cutting process, the insertion angle of the wire saw 93 into the side face 83 of the silicon carbide single-crystal ingot 80 is unstable, and the wire saw 93 may be inserted obliquely into the side face 83. If the cutting of the silicon carbide single-crystal ingot 80 with the wire saw 93 is started without using the guard section 92, the wire saw 93 tends to be inserted obliquely to the side face 83. According to the present embodiment, the protective section 92 covers the entire area of ​​the orientation flat 84. Although a cut surface of the protective section 92, which is cut first, may be curved with respect to the side face of the protective section 92, the cut surface will gradually become substantially perpendicular to the side face. Therefore, the silicon carbide single-crystal ingot 80, which is cut downstream of the protective section 92, will be cut substantially perpendicular to the side face 83 of the silicon carbide single-crystal ingot 80. Consequently, the extent of the curvature 101 of the end region 103, which extends to the orientation flat 31, can be reduced (see Fig. 4). The silicon carbide single-crystal substrate 10 (see Fig. 1) is prepared as above. (Method for the production of the silicon carbide epitaxy substrate) The following describes a process for producing a silicon carbide epitaxial substrate. The silicon carbide layer 20 is formed on the silicon carbide single-crystal substrate 10 by epitaxial growth, for example, by chemical hot-wall vapor deposition (CVD). More precisely, the silicon carbide single-crystal substrate 10 is placed in a CVD reaction chamber. After, for example, the pressure in the reaction chamber is reduced from atmospheric pressure to approximately 1 × 10⁻⁶ Pa, the temperature of the silicon carbide single-crystal substrate 10 is increased. During the temperature increase, hydrogen (H₂) gas is introduced into the reaction chamber as a carrier gas. Once the temperature in the reaction chamber reaches, for example, approximately 1600°C, a source gas and dopant gas are introduced. The source gas consists of silicon (Si) source gas and carbon (C) source gas. For example, silane (SiH₄) gas can be used as the silicon source gas. For example, propane (C₃H₈) gas can be used as the carbon source gas. The flow rates of the silane and propane gases are set, for example, to 46 sccm and 14 sccm, respectively. The volume ratio of the silane gas to hydrogen is set, for example, to 0.04%. The C / Si ratio of the source gas is set, for example, to 0.9. For example, ammonia (NH3) gas is used as the dopant gas. Ammonia gas decomposes more readily than triple-bonded nitrogen gas. Using ammonia gas is expected to improve the uniformity of the charge carrier concentration in the plane. The concentration of ammonia gas relative to hydrogen gas is adjusted to, for example, 1 ppm. By supplying the carrier gas, the source gas, and the dopant gas to the reaction chamber while the silicon carbide single-crystal substrate 10 is heated to approximately 1600°C, the silicon carbide layer 20 is formed on the silicon carbide single-crystal substrate 10 by epitaxial growth (see Fig. 7 and Fig. 18). The silicon carbide epitaxial substrate 100, comprising the silicon carbide single-crystal substrate 10 and the silicon carbide layer 20, is thus produced. (Method for manufacturing a silicon carbide semiconductor device) The following describes a method for manufacturing a silicon carbide semiconductor device 300 according to the present embodiment. The method for manufacturing a silicon carbide semiconductor device according to the present embodiment essentially comprises an epitaxial substrate manufacturing step (S10: Fig. 19) and a substrate processing step (S20: Fig. 19). First, the epitaxial substrate preparation step (S10: Fig. 19) is carried out. In particular, the silicon carbide epitaxial substrate 100 is produced using the method for producing a silicon carbide epitaxial substrate previously described (see Fig. 7 and Fig. 18). Then the substrate processing step (S20: Fig. 19) is carried out. In particular, a silicon carbide semiconductor device is produced by processing the silicon carbide epitaxy substrate. The term "processing" encompasses various types of processing, such as ion implantation, heat treatment, etching, oxide film formation, electrode formation, and singulation. A substrate processing step may include ion implantation, heat treatment, etching, oxide film formation, electrode formation, and / or singulation. The following describes a process for fabricating a metal oxide semiconductor field-effect transistor (MOSFET) as an example of a silicon carbide semiconductor device. The substrate preparation step (S20: Fig. 19) comprises an ion implantation step (S21: Fig. 19), an oxide film formation step (S22: Fig. 19), an electrode formation step (S23: Fig. 19), and a singulation step (S24: Fig. 19). First, the ion implantation step (S21: Fig. 19) is performed. A p-type impurity, such as aluminum (Al), is implanted into the second main surface 12, on which a mask (not shown) with an opening is formed. This creates a body region 132 with the p-type conductivity. Subsequently, an n-type impurity, such as phosphorus (P), is implanted at a prescribed position within the body region 132. This creates a source region 133 with the n-type conductivity. Finally, a p-type impurity, such as aluminum, is implanted at a prescribed position within the source region 133. This creates a contact region 134 with the p-type conductivity (see Fig. 20). A different section in the silicon carbide layer 20 than the body region 132, the source region 133, and the contact region 134 is a drift region 131. The source region 133 is separated from the drift region 131 by the body region 132. Ions can be implanted by heating the silicon carbide epitaxy substrate 100 to a temperature of approximately not less than 300°C and not more than 600°C. After ion implantation, the silicon carbide epitaxy substrate 100 is subjected to an activation annealing step. The impurities implanted into the silicon carbide layer 20 are activated by the activation annealing, so that carriers are formed in each region. An atmosphere for activation annealing can, for example, be an argon (Ar) atmosphere. An activation annealing temperature can, for example, be set to approximately 1800°C. The duration of the activation glow step can be set to approximately 30 minutes, for example. The oxide film formation step (S22: Fig. 19) is then carried out. For example, if the silicon carbide epitaxy substrate 100 is heated in an oxygen-containing atmosphere, an oxide film 136 forms on the second main surface 12 (see Fig. 21). The oxide film 136 is, for example, composed of silicon dioxide (SiO2). The oxide film 136 serves as a gate insulating film. A temperature for the thermal oxidation treatment can be set, for example, to approximately 1300°C. A duration for the thermal oxidation treatment can be set, for example, to approximately 30 minutes. After the formation of oxide film 136, further heat treatment can be carried out in a nitrogen atmosphere. For example, the heat treatment can be performed for about one hour at approximately 1100°C in a nitrogen oxide (NO) or nitrous oxide (N₂O) atmosphere. Afterwards, the heat treatment can be carried out in an argon atmosphere. For example, the heat treatment in an argon atmosphere can be performed for about one hour at a temperature of approximately 1100 to 1500°C. The electrode formation step (S23: Fig. 19) is then carried out. A first electrode 141 is formed on the oxide film 136. The first electrode 141 serves as a gate electrode. The first electrode 141 is formed, for example, by CVD. The first electrode 141 consists, for example, of polysilicon, which is conductive due to the presence of an impurity. The first electrode 141 is formed at a position opposite the source region 133 and the body region 132. Subsequently, an intermediate insulating film 137, covering the first electrode 141, is formed. The intermediate insulating film 137 is formed, for example, by CVD. The intermediate insulating film 137 consists, for example, of silicon dioxide. The intermediate insulating film 137 is formed such that it is in contact with the first electrode 141 and the oxide film 136. The oxide film 136 and the intermediate insulating film 137 are then etched away at a predetermined position. The source region 133 and the contact region 134 are thus exposed through the oxide film 136. A second electrode 142 is formed, for example, by sputtering in this exposed section. The second electrode 142 serves as a source electrode. The second electrode 142 is made, for example, of titanium, aluminum, and silicon. After the formation of the second electrode 142, the second electrode 142 and the silicon carbide epitaxy substrate 100 are heated to a temperature of, for example, approximately 900 to 1100°C. This brings the second electrode 142 and the silicon carbide epitaxy substrate 100 into ohmic contact with each other. Subsequently, an intermediate compound layer 138 is formed so that it is in contact with the second electrode 142. The intermediate compound layer 138 is made of a material that contains, for example, aluminum. Subsequently, a third electrode 143 is formed on the third main surface 13. The third electrode 143 serves as a drain electrode. The third electrode 143 is, for example, made of an alloy containing nickel and silicon (e.g., NiSi). The singulation step (S24: Fig. 19) is then performed. For example, when singulating the silicon carbide epitaxy substrate 100 along a singulation line, the silicon carbide epitaxy substrate 100 is divided into several semiconductor chips. The silicon carbide semiconductor device 300 is manufactured as previously described (see Fig. 22). Although the method for fabricating a silicon carbide semiconductor device according to the present invention was previously described with reference to a MOSFET, the fabrication method according to the present invention is not limited thereto. The fabrication method according to the present invention is applicable to various silicon carbide semiconductor devices, such as an insulated-gate bipolar transistor (IGBT), a Schottky diode (SBD), a thyristor, a gate turn-off thyristor (GTO), and a PiN diode. Reference symbol list 1 First position; 2 Second position; 3 Line segment; 4 Line of least squares; 5 Midpoint; 6, 8 Point; 7, 9 Contact point, tangent; 10 Single crystal substrate; 11 First principal face; 12 Second principal face; 13 Third principal face (surface); 14 Fourth principal face (surface); 15 Cross-sectional profile; 20 Silicon carbide layer; 30 Side end face; 31, 84 Orientation flattening; 32 Curvature section; 33 Lower arc section (end section); 34 Middle arc section; 35 Upper arc section (end section); 36 Virtual surface; 41 Lower region; 43 Upper region; 50 Laser displacement meter; 51 Light-emitting element; 52 Light-receiving element; 53 Incident light; 54 Reflected light; 55 Step; 57 Surface profiling system; 61 First grinding stone; 62 Second grinding stone; 65, 71 Holder; 67 Rotation axis; 68 Third grinding stone; 80 Single crystal ingot; 81 Upper surface; 82 Lower surface; 83 Side surface; 85 Curved surface section; 91 Base; 92 Protective section;93 Wire saw; 95 Depression; 96 Surface; 100 Silicon carbide epitaxy substrate; 101 Curvature; 102 Region; 103 End region (first end region); 104 Middle region; 105 Outer circumference; 131 Drift region; 132 Body region; 133 Source region; 134 Contact region; 136 Oxide film; 137 Interlayer insulating film; 138 Interconnect layer; 141 First electrode; 142 Second electrode; 143 Third electrode; and 300 Silicon carbide semiconductor device;

Claims

Silicon carbide single-crystal substrate (10) comprising: a first principal surface (11); and an orientation flattening (31) extending in a <11-20> direction, wherein the first principal surface (11) has an end region (103) extending by at most 5 mm from an outer circumference of the first principal surface (11), and wherein, in a direction perpendicular to the first principal surface (11), a degree of curvature (101) of the end region (103) extending to the orientation flattening (31) is not greater than 3 µm, wherein, when viewed in the direction perpendicular to the first principal surface (11), a cross-section in the direction of the orientation flattening (31) divides the orientation flattening (31) perpendicularly into two equal sections, the end region (103) curves upwards in a direction away from a surface (13) opposite the first principal surface (11).and the degree of curvature (101) represents a distance between a contact point (7) between the orientation flat (31) and the first principal surface (11) and a point (6) at which a smallest square line (4), calculated from a cross-sectional profile (15) of the first principal surface (11) in a region (102) extending from a position 3 mm from the orientation flat (31) to a midpoint (5) of the first principal surface (11) to a position 5 mm from the orientation flat, intersects the orientation flat (31). Silicon carbide single crystal substrate (10) according to claim 1, wherein the curvature (101) is not greater than 2 µm. Silicon carbide single crystal substrate (10) according to claim 2, wherein the curvature (101) is not greater than 1 µm. Silicon carbide single crystal substrate (10) according to one of claims 1 to 3, wherein a line segment (3) that perpendicularly divides the orientation flattening (31) into two equal sections, is divided into four equal sections when viewed in the direction perpendicular to the first principal surface (11), the first principal surface (11) comprises a lower region (41) extending from the orientation flattening (31) to a position (44) corresponding to 1 / 4 of the line segment (3), and wherein the curvature (101) of the end region (103) extending to an end section (33) of the lower region (41) is not greater than 3 µm. Silicon carbide single crystal substrate (10) according to one of claims 1 to 3, wherein a line segment (3) that perpendicularly divides the orientation flattening (31) into two equal sections is divided into four equal sections when viewed in the direction perpendicular to the first principal surface (11), the first principal surface (11) comprises an upper region (43) extending from an end section (35) opposite the orientation flattening (31) to a position (45) corresponding to 1 / 4 of the line segment (3), and wherein the curvature (101) of the end region (103) extending to the end section (35) of the upper region (43) is not greater than 3 µm. Silicon carbide single-crystal substrate (10) according to one of claims 1 to 3, wherein a line segment (3) that perpendicularly divides the orientation flattening (31) into two equal sections is divided into four equal sections when viewed in the direction perpendicular to the first principal surface (11), the first principal surface (11) comprises a lower region (41) extending from the orientation flattening (31) to a position (44) corresponding to 1 / 4 of the line segment (3), and an upper region (43) extending from an end section (35) opposite the orientation flattening (31) to a position (45) corresponding to 1 / 4 of the line segment (3), wherein the curvature (101) of the end region (103) extending to an end section (33) of the lower region (41) is not greater than 3 µm, and the curvature (101) of the The end region (103), which extends to the end section (35) of the upper region (43), is not larger than 3 µm. Silicon carbide single-crystal substrate (10) comprising: a first principal surface (11); and an orientation flattening (31) extending in a <11-20> direction, wherein the first principal surface (11) has an end region (103) extending by at most 5 mm from an outer circumference of the first principal surface (11), and wherein, in a direction perpendicular to the first principal surface (11), a degree of curvature (101) of the end region (103) extending to the orientation flattening (31) is not greater than 3 µm, wherein, when viewed in the direction perpendicular to the first principal surface (11), a cross-section in the direction of the orientation flattening (31) divides the orientation flattening (31) perpendicularly into two equal sections, the end region (103) curves downwards in a direction away from a surface (13) opposite the first principal surface (11).and the degree of curvature (101) represents a distance between a contact point (7) between the orientation flat (31) and the first principal surface (11) and a point (6) at which a smallest square line (4), calculated from a cross-sectional profile (15) of the first principal surface (11) in an area (102) extending from a position 3 mm from the orientation flat (31) to a midpoint (5) of the first principal surface (11) to a position 5 mm from the orientation flat (31), intersects a virtual plane (36) extending along the orientation flat (31). Silicon carbide single crystal substrate (10) according to claim 7, wherein the curvature (101) is not greater than 2 µm. Silicon carbide single crystal substrate (10) according to claim 8, wherein the curvature (101) is not greater than 1 µm. Silicon carbide single crystal substrate (10) according to one of claims 7 to 9, wherein a line segment (3) that perpendicularly divides the orientation flattening (31) into two equal sections, is divided into four equal sections when viewed in the direction perpendicular to the first principal surface (11), the first principal surface (11) comprises a lower region (41) extending from the orientation flattening (31) to a position (44) corresponding to 1 / 4 of the line segment (3), and wherein the curvature (101) of the end region (103) extending to an end section (33) of the lower region (41) is not greater than 3 µm. Silicon carbide single crystal substrate (10) according to one of claims 7 to 9, wherein a line segment (3) that perpendicularly divides the orientation flattening (31) into two equal sections is divided into four equal sections when viewed in the direction perpendicular to the first principal surface (11), the first principal surface (11) comprises an upper region (43) extending from an end section (35) opposite the orientation flattening (31) to a position (45) corresponding to 1 / 4 of the line segment (3), and wherein the curvature (101) of the end region (103) extending to the end section (35) of the upper region (43) is not greater than 3 µm. Silicon carbide single-crystal substrate (10) according to one of claims 7 to 9, wherein a line segment (3) that perpendicularly divides the orientation flattening (31) into two equal sections is divided into four equal sections when viewed in the direction perpendicular to the first principal surface (11), the first principal surface (11) comprises a lower region (41) extending from the orientation flattening (31) to a position (44) corresponding to 1 / 4 of the line segment (3), and an upper region (43) extending from an end section (35) opposite the orientation flattening (31) to a position (45) corresponding to 1 / 4 of the line segment (3), wherein the curvature (101) of the end region (103) extending to an end section (33) of the lower region (41) is not greater than 3 µm, and the curvature (101) of the The end region (103), which extends to the end section (35) of the upper region (43), is not larger than 3 µm. Silicon carbide epitaxy substrate (100) comprising: the silicon carbide single crystal substrate (10) according to any one of claims 1 to 3 and 7 to 9; and a silicon carbide layer (20) on the first principal surface (11), wherein the silicon carbide layer (20) has a second principal surface (12) opposite a surface (14) that is in contact with the first principal surface (11), and wherein the second principal surface (12) is free of a stacking defect extending in a <1-100> direction from the orientation flattening (31) and having a length of not less than 1 mm. Silicon carbide epitaxy substrate (100) comprising: the silicon carbide single crystal substrate (10) according to claim 4 or 10; and a silicon carbide layer (20) on the first main surface (11), wherein the silicon carbide layer (20) has a second main surface (12) opposite a surface (14) that is in contact with the first main surface (11), and wherein the second main surface (12) is free of a stacking defect extending in a <1-100> direction from the end section (33) of the lower region (41) and having a length of not less than 1 mm. Silicon carbide epitaxy substrate (100) comprising: the silicon carbide single crystal substrate (10) according to claim 5 or 11; and a silicon carbide layer (20) on the first principal surface (11), wherein the silicon carbide layer (20) has a second principal surface (12) opposite a surface (14) that is in contact with the first principal surface (11), and wherein the second principal surface (12) is free of a stacking defect extending in a <1-100> direction from the end section (35) of the upper region (43) and having a length of not less than 1 mm. Silicon carbide epitaxy substrate (100) comprising: the silicon carbide single crystal substrate (10) according to claim 6 or 12; and a silicon carbide layer (20) on the first principal surface (11), wherein the silicon carbide layer (20) has a second principal surface (12) opposite a surface (14) that is in contact with the first principal surface (11), and wherein the second principal surface (12) is free from a stacking fault extending in a <1-100> direction from an end section (33) of a lower region (41) and having a length of not less than 1 mm, and from a stacking fault extending in the <1-100> direction from an end section (35) of an upper region (43) and having a length of not less than 1 mm. Method for manufacturing a silicon carbide semiconductor device (300), comprising: manufacturing the silicon carbide epitaxy substrate (100) according to one of claims 13, 14, 15 and 16; and processing the silicon carbide epitaxy substrate (100).

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