Method for manufacturing silicon carbide semiconductor device and silicon carbide substrate

Abstract

The present invention provides a silicon carbide substrate, a silicon carbide single crystal substrate, and a method for manufacturing a silicon carbide semiconductor device that can accurately determine the quality of the device's active region. [Solution] The method for manufacturing a silicon carbide semiconductor device includes a silicon carbide single crystal substrate and a silicon carbide epitaxial film provided on the silicon carbide single crystal substrate, in which a reference mark serving as a reference for two-dimensional position coordinates is formed on the silicon carbide substrate, after the reference mark is formed, at least one of polishing or cleaning is performed on the reference mark formation surface of the silicon carbide substrate, the position coordinates of a defect in the silicon carbide substrate are identified based on the reference mark, an active element region is formed on the silicon carbide substrate, the position coordinates of the active element region are identified based on the reference mark, and the quality of the active element region is determined by relating the position coordinates of the defect and the position coordinates of the active element region.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a silicon carbide substrate, a silicon carbide single crystal substrate, and a silicon carbide semiconductor device. This application claims priority based on Japanese Patent Application No. 2020-169062, filed on October 6, 2020. All the descriptions contained in the Japanese patent application are incorporated herein by reference.

Background Art

[0002] Japanese Patent Laid-Open No. 4-62858 (Patent Document 1) describes a method for observing and analyzing foreign matter. In this method, a coordinate reference is provided on the wafer and a coordinate system is set.

[0003] Japanese Patent Laid-Open No. 2000-269286 (Patent Document 2) describes a method for specifying the defect position of a semiconductor substrate. In this method, the position of the defect is specified based on the coordinate values in the coordinate system of the affine transformation and the defect evaluation device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] The method for manufacturing a silicon carbide semiconductor device according to this disclosure comprises the following steps: A reference mark is formed on a silicon carbide substrate, which includes a silicon carbide single crystal substrate and a silicon carbide epitaxial film provided on the silicon carbide single crystal substrate, to serve as a reference for two-dimensional position coordinates. After forming the reference mark, at least one of polishing or cleaning is performed on the reference mark formation surface of the silicon carbide substrate. Based on the reference mark, the position coordinates of a defect in the silicon carbide substrate are identified. An active region is formed on the silicon carbide substrate. Based on the reference mark, the position coordinates of the active region are identified. The position coordinates of the defect and the position coordinates of the active region are correlated to determine whether the active region is good or bad.

[0006] The silicon carbide substrate according to this disclosure is a silicon carbide substrate comprising a silicon carbide single crystal substrate and a silicon carbide epitaxial film provided on the silicon carbide single crystal substrate, and comprises an outer peripheral edge and a main surface. The main surface is surrounded by the outer peripheral edge. The main surface includes an outer peripheral region which is within 5 mm from the outer peripheral edge and a central region enclosed by the outer peripheral region. The outer peripheral region of the silicon carbide epitaxial film is provided with a plurality of reference marks which serve as a reference for two-dimensional position coordinates.

[0007] The silicon carbide single crystal substrate according to this disclosure comprises an outer edge and a main surface surrounded by the outer edge. The main surface includes an outer region, which is a region within 5 mm from the outer edge, and a central region enclosed by the outer region. The outer region is provided with multiple reference marks that serve as a reference for two-dimensional position coordinates. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic plan view showing the configuration of a silicon carbide single crystal substrate according to the first embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view along the line II-II in Figure 1. [Figure 3] Figure 3 is an enlarged plan view showing the configuration of the reference marks. [Figure 4] Figure 4 is a schematic cross-sectional view along the line IV-IV in Figure 3. [Figure 5]Figure 5 is an enlarged schematic plan view showing the configuration of reference marks in a silicon carbide single crystal substrate according to the second embodiment. [Figure 6] Figure 6 is a schematic cross-sectional view along the line VI-VI in Figure 5. [Figure 7] Figure 7 is an enlarged schematic plan view showing the configuration of reference marks in a silicon carbide single crystal substrate according to the third embodiment. [Figure 8] Figure 8 is a schematic cross-sectional view along the line VIII-VIII in Figure 7. [Figure 9] Figure 9 is a schematic plan view showing the configuration of a silicon carbide single crystal substrate according to the fourth embodiment. [Figure 10] Figure 10 is a schematic cross-sectional view along line XX in Figure 9. [Figure 11] Figure 11 is a schematic plan view showing the configuration of a silicon carbide substrate according to the fifth embodiment. [Figure 12] Figure 12 is a schematic cross-sectional view along the line XII-XII in Figure 11. [Figure 13] Figure 13 is a schematic flowchart showing the manufacturing method of a silicon carbide semiconductor device according to the sixth embodiment. [Figure 14] Figure 14 is a schematic cross-sectional view showing the process of forming reference marks on a silicon carbide single crystal substrate. [Figure 15] Figure 15 is a schematic plan view illustrating the process of identifying the position coordinates of defects in a silicon carbide single crystal substrate based on reference marks. [Figure 16] Figure 16 is a schematic cross-sectional view showing the process of forming a silicon carbide epitaxial film on a silicon carbide single crystal substrate. [Figure 17] Figure 17 is a schematic plan view illustrating the process of identifying the position coordinates of defects in a silicon carbide epitaxial film based on reference marks. [Figure 18] Figure 18 is a schematic cross-sectional view showing the process of forming an active region on a silicon carbide epitaxial film. [Figure 19] Figure 19 is a schematic plan view illustrating the process for determining the quality of the active region of the element. [Figure 20]FIG. 20 is a schematic cross-sectional view showing a process of forming a gate insulating film. [Figure 21] FIG. 21 is a schematic cross-sectional view showing the configuration of a silicon carbide semiconductor device. [Figure 22] FIG. 22 is a flowchart schematically showing a method of manufacturing a silicon carbide semiconductor device according to the seventh embodiment. [Figure 23] FIG. 23 is a schematic plan view showing a process of adjusting the formation position of an element active region based on the position coordinates of a defect. [Figure 24] FIG. 24 is a flowchart schematically showing a method of manufacturing a silicon carbide semiconductor device according to the eighth embodiment. [Figure 25] FIG. 25 is a schematic cross-sectional view showing a process of preparing a silicon carbide single crystal substrate. [Figure 26] FIG. 26 is a schematic cross-sectional view showing a process of forming a silicon carbide epitaxial film on a silicon carbide single crystal substrate. [Figure 27] FIG. 27 is a schematic cross-sectional view showing a process of forming a reference mark on a silicon carbide epitaxial film. [Figure 28] FIG. 28 is a schematic cross-sectional view showing a process of forming an element active region on a silicon carbide epitaxial film. [Figure 29] FIG. 29 is a flowchart schematically showing a method of manufacturing a silicon carbide semiconductor device according to the ninth embodiment. [Figure 30] FIG. 30 is a schematic cross-sectional view showing a process of forming a first silicon carbide epitaxial film on a silicon carbide single crystal substrate. [Figure 31] FIG. 31 is a schematic cross-sectional view showing a process of forming a reference mark on a first silicon carbide epitaxial film. [Figure 32] FIG. 32 is a schematic cross-sectional view showing a process of forming a second silicon carbide epitaxial film on a first silicon carbide epitaxial film. [Figure 33] FIG. 33 is a schematic cross-sectional view showing a process of forming an element active region on a second silicon carbide epitaxial film.

Embodiments for Carrying Out the Invention

[0009] [Issues this disclosure aims to address] The purpose of this disclosure is to provide a silicon carbide substrate, a silicon carbide single crystal substrate, and a method for manufacturing a silicon carbide semiconductor device that can accurately determine the quality of the device's active region. [Effects of this disclosure] According to this disclosure, it is possible to provide a silicon carbide substrate, a silicon carbide single crystal substrate, and a method for manufacturing a silicon carbide semiconductor device that can accurately determine the quality of the device's active region.

[0010] [Summary of the embodiments of this disclosure] First, an overview of the embodiments of this disclosure will be described.

[0011] (1) The manufacturing method of the silicon carbide semiconductor device 300 according to the present disclosure comprises the following steps: A reference mark 3, which serves as a reference for two-dimensional position coordinates, is formed on a silicon carbide substrate 1 including a silicon carbide single crystal substrate 61 and a silicon carbide epitaxial film 62 provided on the silicon carbide single crystal substrate 61. After forming the reference mark 3, at least one of polishing or cleaning is performed on the reference mark formation surface of the silicon carbide substrate 1. Based on the reference mark 3, the position coordinates of a defect 80 on the silicon carbide substrate 1 are identified. An element active region 90 is formed on the silicon carbide substrate 1. Based on the reference mark 3, the position coordinates of the element active region 90 are identified. The position coordinates of the defect 80 and the position coordinates of the element active region 90 are correlated to determine whether the element active region 90 is good or bad. Polishing of the reference mark formation surface may be performed only on the reference mark formation surface (single-sided polishing), or on both the reference mark formation surface and the surface opposite to the reference mark formation surface (double-sided polishing).

[0012] According to the manufacturing method of the silicon carbide semiconductor device 300 described in (1) above, the position coordinates of the defect 80 on the silicon carbide substrate 1 are identified based on the reference mark 3. An element active region 90 is formed on the silicon carbide substrate 1. The position coordinates of the element active region 90 are identified based on the reference mark 3. The position coordinates of the defect 80 and the position coordinates of the element active region 90 are associated, and the quality of the element active region 90 is determined. By linking the position coordinates of the defect 80 and the position coordinates of the element active region 90 using common coordinates based on the reference mark 3, defective elements caused by the defect 80 can be identified with high accuracy. Therefore, the quality of the element active region 90 can be determined with high accuracy.

[0013] Furthermore, before the silicon carbide semiconductor device 300 is completed, the failure rate of elements due to defects 80 can be accurately estimated. Based on the failure rate of these elements, it becomes possible to design the optimal element structure or element arrangement.

[0014] (2) In the manufacturing method of the silicon carbide semiconductor device 300 described in (1) above, in the step of forming the element active region 90 on the silicon carbide substrate 1, the formation position of the element active region 90 may be adjusted based on the position coordinates of the defect 80. This makes it possible to form the element active region 90 while avoiding the defect 80. As a result, the yield of the device can be improved.

[0015] (3) In the manufacturing method of the silicon carbide semiconductor device 300 according to (1) or (2) above, the reference mark 3 may be provided on the silicon carbide single crystal substrate 61. The element active region 90 may be provided on the silicon carbide epitaxial film 62. When the reference mark 3 is provided on the silicon carbide single crystal substrate 61, after the reference mark is formed, it is desirable to polish the surface on which the reference mark is formed in order to remove any unevenness, distortion, foreign matter such as dust, and dirt near the reference mark caused by processing, and then clean the surface on which the reference mark is formed. Polishing may be performed only on the surface on which the reference mark is formed, or on both the surface on which the reference mark is formed and the surface on the opposite side of the surface on which the reference mark is formed.

[0016] Furthermore, only a portion of the silicon carbide epitaxial film 62 provided above the reference mark 3 may be removed by etching or the like until the silicon carbide single crystal substrate 61 is exposed. By etching or the like, the reference mark 3 provided on the silicon carbide single crystal substrate 61 is exposed, making it possible to distinguish the reference mark 3 with greater accuracy. The etching of the silicon carbide epitaxial film 62 may be continued until the silicon carbide single crystal substrate 61 is exposed, or it may be stopped just before the silicon carbide single crystal substrate 61 is exposed. If the etching is stopped just before the silicon carbide single crystal substrate 61 is exposed, the silicon carbide epitaxial film 62 may remain above the reference mark 3.

[0017] (4) According to the method for manufacturing the silicon carbide semiconductor device 300 described in (1) or (2) above, the reference mark 3 and the element active region 90 may each be provided on the silicon carbide epitaxial film 62. When the reference mark 3 is provided on the silicon carbide epitaxial film 62, after the reference mark 3 is formed, the reference mark formation surface is polished or cleaned.

[0018] (5) According to the method for manufacturing the silicon carbide semiconductor device 300 according to any of (1) to (4) above, the reference mark 3 may be formed by laser processing. If the reference mark 3 is an indentation, dust may be generated when forming the reference mark 3. By forming the reference mark 3 by laser processing, the generation of dust can be suppressed. Therefore, the yield of the device can be further improved. Also, if the reference mark 3 is an indentation, it is difficult to form the reference mark 3 deeply. Therefore, if polishing is performed on the reference mark formation surface to remove the unevenness and distortion near the reference mark that occurs when processing the reference mark 3, the reference mark 3 may disappear. In this case, it becomes difficult to distinguish the reference mark 3. By forming the reference mark 3 by laser processing, the reference mark 3 can be formed deeply. Therefore, polishing can be performed on the reference mark formation surface to remove the unevenness and distortion near the reference mark that occurs when processing the reference mark 3. Furthermore, the reference mark 3 can be distinguished with high accuracy during alignment. Furthermore, if the reference mark 3 is an indentation, cracks may occur in the substrate on which the reference mark 3 is formed. By forming the reference mark 3 using laser processing, it is possible to suppress the occurrence of cracks in the substrate.

[0019] When the reference mark 3 is provided on the silicon carbide single crystal substrate 61, after the reference mark is formed, it is desirable to polish the surface on which the reference mark is formed in order to remove any irregularities, distortions, foreign matter such as dust, and dirt near the reference mark caused by processing, and then to clean the surface on which the reference mark is formed. Polishing may be performed only on the surface on which the reference mark is formed, or on both the surface on which the reference mark is formed and the surface opposite to the surface on which the reference mark is formed. When the reference mark 3 is provided on the silicon carbide epitaxial film 62, after the reference mark 3 is formed, polishing or cleaning is performed on the surface on which the reference mark is formed.

[0020] (6) According to the method for manufacturing the silicon carbide semiconductor device 300 according to any of (1) to (4) above, the reference mark 3 may be formed by etching. If the reference mark 3 is an indentation, dust may be generated when forming the reference mark 3. By forming the reference mark 3 by etching, the generation of dust can be suppressed. Therefore, the yield of the device can be further improved. Also, if the reference mark 3 is an indentation, it is difficult to form the reference mark 3 deeply. Therefore, if polishing is performed on the reference mark formation surface to remove unevenness and distortion near the reference mark that occurs when processing the reference mark 3, the reference mark 3 may disappear. In this case, it becomes difficult to distinguish the reference mark 3. By forming the reference mark 3 by etching, the reference mark 3 can be formed deeply. Therefore, polishing can be performed on the reference mark formation surface to remove unevenness and distortion near the reference mark that occurs when processing the reference mark 3. Furthermore, the reference mark 3 can be distinguished with high accuracy during alignment. Furthermore, if the reference mark 3 is an indentation, cracks may occur in the substrate on which the reference mark 3 is formed. By forming the reference mark 3 through etching, it is possible to suppress the occurrence of cracks in the substrate.

[0021] When the reference mark 3 is provided on the silicon carbide single crystal substrate 61, after the reference mark is formed, it is desirable to polish the surface on which the reference mark is formed in order to remove any irregularities, distortions, foreign matter such as dust, and dirt near the reference mark caused by processing, and then to clean the surface on which the reference mark is formed. Polishing may be performed only on the surface on which the reference mark is formed, or on both the surface on which the reference mark is formed and the surface opposite to the surface on which the reference mark is formed. When the reference mark 3 is provided on the silicon carbide epitaxial film 62, after the reference mark 3 is formed, polishing or cleaning is performed on the surface on which the reference mark is formed.

[0022] (7) The silicon carbide substrate 1 according to the present disclosure is a silicon carbide substrate 1 comprising a silicon carbide single crystal substrate 61 and a silicon carbide epitaxial film 62 provided on the silicon carbide single crystal substrate 61, and comprises an outer peripheral edge 2 and a main surface 10. The main surface 10 is surrounded by the outer peripheral edge 2. The main surface 10 includes an outer peripheral region 12 which is a region within 5 mm from the outer peripheral edge 2 and a central region 11 surrounded by the outer peripheral region 12. The outer peripheral region 12 of the silicon carbide epitaxial film 62 is provided with a plurality of reference marks 3 which serve as a reference for two-dimensional position coordinates. This makes it possible to secure a wider area for the region where the element is formed compared to the case where the reference marks 3 are provided in the central region 11.

[0023] (8) In the silicon carbide substrate 1 according to (7) above, the distance between each of the multiple reference marks 3 when viewed in a direction perpendicular to the main surface 10 may be 30 mm or more. This makes it possible to accurately identify the position coordinates of the defect 80.

[0024] (9) In the silicon carbide substrate 1 according to (7) or (8) above, the diameter of the smallest virtual circle surrounding each of the multiple reference marks 3 when viewed in a direction perpendicular to the main surface 10 may be greater than 10 μm and less than 3 mm. This allows for accurate identification of the reference marks 3 during alignment.

[0025] (10) In the case of the silicon carbide substrate 1 according to any of (7) to (9) above, the depth of each of the multiple reference marks 3 in the direction perpendicular to the main surface 10 is preferably about 1 / 10 to 10 times the thickness of the silicon carbide epitaxial film 62. The depth of each of the multiple reference marks 3 may be, for example, greater than 0.5 μm and less than 100 μm. When the reference marks 3 are provided on the silicon carbide single crystal substrate 61, by forming reference marks 3 of the above depth, even if the shape of the reference marks 3 that are carried over and formed on the silicon carbide epitaxial film 62 is somewhat distorted due to the growth conditions of the silicon carbide epitaxial film 62 (for example, growth temperature and C / Si ratio), the reference marks 3 can be accurately identified during alignment.

[0026] (11) In the case of the silicon carbide substrate 1 according to any of (7) to (10) above, each of the multiple reference marks 3 may have a cross shape when viewed in a direction perpendicular to the main surface 10. This makes it possible to accurately distinguish the reference marks 3 during alignment.

[0027] (12) The silicon carbide single crystal substrate 61 according to the present disclosure comprises an outer peripheral edge 2 and a main surface 10 surrounded by the outer peripheral edge 2. The main surface 10 includes an outer peripheral region 12 which is a region within 5 mm from the outer peripheral edge 2 and a central region 11 surrounded by the outer peripheral region 12. The outer peripheral region 12 is provided with a plurality of reference marks 3 which serve as a reference for two-dimensional position coordinates.

[0028] (13) In the silicon carbide single crystal substrate 61 according to (12) above, the distance between each of the multiple reference marks 3 when viewed in a direction perpendicular to the main surface 10 may be 30 mm or more.

[0029] (14) In the silicon carbide single crystal substrate 61 according to (12) or (13) above, the diameter of the smallest virtual circle surrounding each of the multiple reference marks 3 when viewed in a direction perpendicular to the main surface 10 may be greater than 10 μm and less than 3 mm.

[0030] (15) In the case of the silicon carbide single crystal substrate 61 according to any of (12) to (14) above, the depth of each of the multiple reference marks 3 in the direction perpendicular to the main surface 10 may be greater than 0.5 μm and less than 100 μm.

[0031] (16) In the case of a silicon carbide single crystal substrate 61 according to any of (12) to (15) above, each of the multiple reference marks 3 may have a cross shape when viewed in a direction perpendicular to the main surface 10.

[0032] [Details of the embodiments of this disclosure] The details of the embodiments of this disclosure (hereinafter also referred to as these embodiments) will be described below with reference to the drawings. In the following drawings, identical or corresponding parts will be given the same reference numerals, and their descriptions will not be repeated.

[0033] (First Embodiment) First, the configuration of the silicon carbide single crystal substrate 61 according to the first embodiment will be described.

[0034] Figure 1 is a schematic plan view showing the structure of a silicon carbide single crystal substrate 61 according to the first embodiment. As shown in Figure 1, the silicon carbide single crystal substrate 61 according to the first embodiment mainly has a first main surface 10 and an outer peripheral edge 2. The first main surface 10 is surrounded by the outer peripheral edge 2. The first main surface 10 includes a central region 11 and an outer peripheral region 12. The outer peripheral region 12 is a region within 5 mm from the outer peripheral edge 2. The central region 11 is surrounded by the outer peripheral region 12. The first main surface 10 is composed of the central region 11 and the outer peripheral region 12. In the radial direction of the first main surface 10, the distance W2 between the boundary between the central region 11 and the outer peripheral region 12 and the outer peripheral edge 2 is 5 mm.

[0035] The outer edge 2 has, for example, an orientation flat 2a and an arc-shaped portion 2b. The orientation flat 2a extends along a first direction X. As shown in Figure 1, the orientation flat 2a is linear when viewed in a direction perpendicular to the first main surface 10. The arc-shaped portion 2b is connected to the orientation flat 2a. The arc-shaped portion 2b is arc-shaped when viewed in a direction perpendicular to the first main surface 10.

[0036] As shown in Figure 1, when viewed perpendicular to the first principal surface 10, the first principal surface 10 extends along the first direction X and the second direction Y, respectively. When viewed perpendicular to the first principal surface 10, the second direction Y is perpendicular to the first direction X.

[0037] The first direction X is, for example, the <11-20> direction. The first direction X may also be, for example, the [11-20] direction. The first direction X may also be the direction obtained by projecting the <11-20> direction onto the first principal plane 10. From another point of view, the first direction X may also be a direction that includes, for example, the <11-20> direction component.

[0038] The second direction Y is, for example, the <1-100> direction. The second direction Y may also be, for example, the [1-100] direction. The second direction Y may also be, for example, the direction obtained by projecting the <1-100> direction onto the first principal plane 10. From another point of view, the second direction Y may also be, for example, a direction that includes the <1-100> direction component.

[0039] The first main surface 10 may be the {0001} surface, or it may be a surface inclined with respect to the {0001} surface. If the first main surface 10 is inclined with respect to the {0001} surface, the inclination angle (off-angle) with respect to the {0001} surface is, for example, 1° or more and 8° or less. If the first main surface 10 is inclined with respect to the {0001} surface, the inclination direction (off-direction) of the first main surface 10 is, for example, the <11-20> direction.

[0040] The maximum diameter W1 of the first main surface 10 is, for example, 100 mm (4 inches) or more. The maximum diameter W1 of the first main surface 10 may also be 150 mm (6 inches) or more, or 200 mm (8 inches) or more. There is no particular upper limit to the maximum diameter W1 of the first main surface 10, but it may be, for example, 400 mm (16 inches) or less. Note that the maximum diameter W1 of the first main surface 10 is the longest straight-line distance between two different points on the outer edge 2.

[0041] In this specification, 4 inches refers to 100 mm or 101.6 mm (4 inches × 25.4 mm / inch). 6 inches refers to 150 mm or 152.4 mm (6 inches × 25.4 mm / inch). 8 inches refers to 200 mm or 203.2 mm (8 inches × 25.4 mm / inch). 16 inches refers to 400 mm or 406.4 mm (16 inches × 25.4 mm / inch).

[0042] As shown in Figure 1, multiple reference marks 3 are provided in the outer perimeter region 12. Each of the multiple reference marks 3 serves as a reference for the two-dimensional position coordinates. As shown in Figure 1, when viewed in a direction perpendicular to the first main surface 10, each of the multiple reference marks 3 may be located within 5 mm of the orientation flat (outer perimeter region 12). The number of reference marks 3 is not particularly limited, but for example, there are two.

[0043] As shown in Figure 1, the distance A between each of the multiple reference marks 3, viewed in a direction perpendicular to the first main surface 10, is, for example, 30 mm or more. The lower limit of the distance A between each of the multiple reference marks 3 is not particularly limited, but may be, for example, 40 mm or more, or 50 mm or more. The upper limit of the distance A between each of the multiple reference marks 3 is not particularly limited, but may be, for example, 200 mm or less, or 150 mm or less.

[0044] As shown in Figure 1, each of the multiple reference marks 3 may have a cross shape when viewed in a direction perpendicular to the first main surface 10. The multiple reference marks 3 may include, for example, a first reference mark 31 and a second reference mark 32. The distance A between each of the multiple reference marks 3 is the distance from the center of the first reference mark 31 to the center of the second reference mark 32. If the reference marks 3 have a cross shape, the distance A between each of the multiple reference marks 3 is the distance from the center of the cross shape of the first reference mark 31 to the center of the cross shape of the second reference mark 32.

[0045] Figure 2 is a schematic cross-sectional view along the line II-II in Figure 1. As shown in Figure 2, the silicon carbide single crystal substrate 61 has a second principal surface 20 opposite to the first principal surface 10. Each of the multiple reference marks 3 is, for example, a recess. In a direction perpendicular to the first principal surface 10, the bottom surface of the recess is located between the first principal surface 10 and the second principal surface 20.

[0046] In a direction perpendicular to the first main surface 10, the depth D of each of the multiple reference marks 3 is, for example, greater than 0.5 μm and less than 100 μm. The lower limit of the depth D of each of the multiple reference marks 3 is not particularly limited, but may be, for example, 3 μm or more, or 5 μm or more. The upper limit of the depth D of each of the multiple reference marks 3 is not particularly limited, but may be, for example, 50 μm or less, or 30 μm or less.

[0047] The polytype of silicon carbide constituting the silicon carbide single crystal substrate 61 is, for example, 4H. The polytype of silicon carbide constituting the silicon carbide single crystal substrate 61 may also be, for example, 6H. The thickness of the silicon carbide single crystal substrate 61 is, for example, 350 μm or more and 500 μm or less. The silicon carbide single crystal substrate 61 contains n-type impurities such as nitrogen (N). The conductivity type of the silicon carbide single crystal substrate 61 is, for example, n-type.

[0048] Figure 3 is an enlarged plan view showing the configuration of the reference mark 3. When viewed perpendicular to the first main surface 10, the shape of the reference mark 3 is, for example, axially symmetric. The shape of the reference mark 3 is, for example, a cross shape. For example, it may be provided so that two rectangles intersect perpendicularly at the center. Figure 4 is a schematic cross-sectional view along the line IV-IV in Figure 3. As shown in Figure 4, the length of the shorter side of the rectangle (third length W3) may be greater than the depth D of the reference mark 3. The third length W3 is, for example, 10 μm.

[0049] The shape of reference mark 3 is not limited to a cross shape. The shape of reference mark 3 may be a polygon, an axisymmetric rectangle (rectangle, square), or a circle. Reference mark 3 is a shape that can be surrounded by, for example, a virtual circle. The smallest virtual circle surrounding reference mark 3 is, for example, the circumcircle of reference mark 3. The center of reference mark 3 is the center of the circumcircle.

[0050] When viewed in a direction perpendicular to the first principal surface 10, the radius of the smallest virtual circle (first virtual circle R1) surrounding each of the multiple reference marks 3 is, for example, greater than 10 μm and less than 3 mm. The lower limit of the radius of the first virtual circle R1 is not particularly limited, but may be, for example, 50 μm or more, or 100 μm or more. The upper limit of the radius of the first virtual circle R1 is not particularly limited, but may be, for example, 1 mm or less, or 0.5 mm or less.

[0051] As shown in Figure 3, the largest virtual circle (second virtual circle R2) surrounded by the reference mark 3 is, for example, the inscribed circle of the reference mark 3. The center of the inscribed circle of the reference mark 3 may coincide with the center of the circumscribed circle of the reference mark 3. Viewed perpendicular to the first principal surface 10, the radius of the second virtual circle R2 is, for example, less than 5 μm.

[0052] As shown in Figure 1, the X-axis is defined as a straight line passing through the center of the first reference mark 31 and the center of the second reference mark 32. The Y-axis is defined as a straight line parallel to the first principal plane 10 and perpendicular to the X-axis. The midpoint between the center of the first reference mark 31 and the center of the second reference mark 32 is, for example, defined as the origin of the 2D position coordinate system. The direction from the origin toward the first reference mark 31 is, for example, defined as the negative direction of the X-axis. The direction from the origin toward the second reference mark 32 is, for example, defined as the positive direction of the X-axis. The direction from the origin toward the orientation flat 2a is, for example, defined as the negative direction of the Y-axis. The direction opposite to the direction from the origin toward the orientation flat 2a is, for example, defined as the positive direction of the Y-axis. For example, a virtual 2D position coordinate system is determined based on the first reference mark 31 and the second reference mark 32 as described above.

[0053] The position coordinates of defect 80 may be defined using the above-mentioned virtual two-dimensional position coordinate system, such as a representative point like the defect center, or a shape such as a rectangle, circle, or ellipse surrounding the defect.

[0054] (Second Embodiment) Next, the configuration of the silicon carbide single crystal substrate 61 according to the second embodiment will be described. The silicon carbide single crystal substrate 61 according to the second embodiment differs from the silicon carbide single crystal substrate 61 according to the first embodiment mainly in that the reference mark 3 is composed of a plurality of recesses 30, and is otherwise the same as the silicon carbide single crystal substrate 61 according to the first embodiment. The following description will focus on the configuration that differs from the silicon carbide single crystal substrate 61 according to the first embodiment.

[0055] Figure 5 is an enlarged schematic plan view showing the configuration of the reference mark 3 of the silicon carbide single crystal substrate 61 according to the second embodiment. As shown in Figure 5, the reference mark 3 of the silicon carbide single crystal substrate 61 according to the second embodiment is composed of a plurality of recesses 30. When viewed in a direction perpendicular to the first main surface 10, the shape of each of the plurality of recesses 30 is, for example, a circle. Each of the plurality of recesses 30 is arranged at equal intervals along, for example, the first direction X and the second direction Y.

[0056] As shown in Figure 5, for example, a 2x10 recess 30 and a 10x2 recess 30 may be provided with a cross-shaped tolerance. Figure 6 is a schematic cross-sectional view along the line VI-VI in Figure 5. As shown in Figure 6, the width of the region between two adjacent recesses (fifth width W5) may be greater than the diameter of each of the multiple recesses 30 (fourth width W4).

[0057] (Third embodiment) Next, the configuration of the silicon carbide single crystal substrate 61 according to the third embodiment will be described. The silicon carbide single crystal substrate 61 according to the third embodiment differs from the silicon carbide single crystal substrate 61 according to the first embodiment mainly in that the reference mark 3 is convex, and in other respects it is the same as the silicon carbide single crystal substrate 61 according to the first embodiment. The following description will focus on the configuration that differs from the silicon carbide single crystal substrate 61 according to the first embodiment.

[0058] Figure 7 is an enlarged plan schematic view showing the configuration of the reference mark 3 of the silicon carbide single crystal substrate 61 according to the third embodiment. Figure 8 is a schematic cross-sectional view along the line VIII-VIII in Figure 7. As shown in Figures 7 and 8, the reference mark 3 may be convex. The shape of the convex reference mark 3 is, for example, a cross shape.

[0059] As shown in Figure 8, a portion of the convex reference mark 3 is provided, for example, between two grooves 54. Each of the two grooves 54 has a bottom surface 53 and a side surface 52. A portion of the side surface 52 of the groove 54 constitutes the side surface of the convex reference mark 3. The depth D of the groove 54 corresponds to the height of the reference mark 3.

[0060] (Fourth Embodiment) Next, the configuration of the silicon carbide single crystal substrate 61 according to the fourth embodiment will be described. The silicon carbide single crystal substrate 61 according to the fourth embodiment differs from the silicon carbide single crystal substrate 61 according to the first embodiment mainly in the placement of the reference mark 3, and is otherwise the same as the silicon carbide single crystal substrate 61 according to the first embodiment. The following description will focus on the configuration that differs from the silicon carbide single crystal substrate 61 according to the first embodiment.

[0061] Figure 9 is a schematic plan view showing the configuration of the silicon carbide single crystal substrate 61 according to the fourth embodiment. Figure 10 is a schematic cross-sectional view along line XX in Figure 9. As shown in Figure 9, the multiple reference marks 3 include, for example, a first reference mark 31, a second reference mark 32, a third reference mark 33, and a fourth reference mark 34. Each of the first reference mark 31, the second reference mark 32, the third reference mark 33, and the fourth reference mark 34 is provided in the outer peripheral region 12.

[0062] A line (first line) passing through the center of the first reference mark 31 and the center of the second reference mark 32 is, for example, parallel to the first direction X. A line (second line) passing through the center of the third reference mark 33 and the center of the fourth reference mark 34 is, for example, parallel to the second direction Y. The first line is used, for example, as the X-axis of the two-dimensional coordinate system. The second line is used, for example, as the Y-axis of the two-dimensional coordinate system. The intersection of the first line and the second line is used, for example, as the origin of the two-dimensional coordinate system. For example, a virtual two-dimensional position coordinate system may be determined based on the first reference mark 31, the second reference mark 32, the third reference mark 33, and the fourth reference mark 34 as described above.

[0063] (Fifth embodiment) Next, the configuration of the silicon carbide substrate 1 according to the fifth embodiment will be described. The silicon carbide substrate 1 according to the fifth embodiment differs from the silicon carbide single crystal substrate 61 according to the first embodiment in that it has a silicon carbide single crystal substrate 61 and a silicon carbide epitaxial film 62, but is otherwise the same as the silicon carbide single crystal substrate 61 according to the first embodiment. The following description will focus on the configuration that differs from the silicon carbide single crystal substrate 61 according to the first embodiment.

[0064] Figure 11 is a schematic plan view showing the configuration of the silicon carbide substrate 1 according to the fifth embodiment. Figure 12 is a schematic cross-sectional view along the line XII-XII in Figure 11. As shown in Figure 12, the silicon carbide substrate 1 has a silicon carbide single crystal substrate 61 and a silicon carbide epitaxial film 62. The silicon carbide epitaxial film 62 is provided on the silicon carbide single crystal substrate 61. The silicon carbide epitaxial film 62 has a third main surface 43 and a fourth main surface 40. The third main surface 43 is in contact with the silicon carbide single crystal substrate 61. The fourth main surface 40 is on the opposite side of the third main surface 43.

[0065] As shown in Figure 11, the fourth main surface 40 has a central region 41 and an outer peripheral region 42. The outer peripheral region 42 is the region within 5 mm from the outer peripheral edge 2. The outer peripheral region 42 surrounds the central region 41. Each of the multiple reference marks 3 is provided in the outer peripheral region 42 of the fourth main surface 40. Each of the multiple reference marks 3 has a first reference mark 31 and a second reference mark 32. As shown in Figure 12, each of the multiple reference marks 3 is provided in the silicon carbide epitaxial film 62.

[0066] The silicon carbide polytype constituting the silicon carbide single crystal substrate 61 and the silicon carbide epitaxial film 62 is, for example, 4H. The silicon carbide polytype constituting the silicon carbide single crystal substrate 61 and the silicon carbide epitaxial film 62 may also be, for example, 6H. The thickness of the silicon carbide single crystal substrate 61 is, for example, 350 μm or more and 500 μm or less. The thickness of the silicon carbide epitaxial film 62 is, for example, 1 μm or more and 100 μm or less.

[0067] Each of the silicon carbide single crystal substrate 61 and the silicon carbide epitaxial film 62 contains n-type impurities, such as nitrogen (N). The conductivity type of each of the silicon carbide single crystal substrate 61 and the silicon carbide epitaxial film 62 is, for example, n-type. The silicon carbide single crystal substrate 61 may be a conductive substrate or a semi-insulating substrate. The silicon carbide epitaxial film 62 may be a homostructure epitaxial film or a heterostructure epitaxial film. The silicon carbide epitaxial film 62 may be a single layer or two or more layers.

[0068] (Sixth Embodiment) Next, a method for manufacturing the silicon carbide semiconductor device 300 according to the sixth embodiment will be described.

[0069] Figure 13 is a schematic flowchart showing the manufacturing method of the silicon carbide semiconductor device 300 according to the sixth embodiment. As shown in Figure 13, the manufacturing method of the silicon carbide semiconductor device 300 according to the sixth embodiment mainly comprises the steps of forming reference marks on a silicon carbide single crystal substrate (S11), polishing the silicon carbide single crystal substrate (S12), cleaning the silicon carbide single crystal substrate (S13), identifying the position coordinates of defects on the silicon carbide single crystal substrate based on the reference marks (S14), forming a silicon carbide epitaxial film on the silicon carbide single crystal substrate (S15), identifying the position coordinates of defects in the silicon carbide epitaxial film based on the reference marks (S16), forming an active device region on the silicon carbide epitaxial film (S17), identifying the position coordinates of the active device region based on the reference marks (S18), and determining the quality of the active device region by relating the position coordinates of the defects and the position coordinates of the active device region (S19).

[0070] First, a silicon carbide single crystal of polytype 4H is manufactured, for example, by sublimation. Next, a silicon carbide single crystal substrate 61 is prepared by slicing the silicon carbide single crystal, for example, by a wire saw. The silicon carbide single crystal substrate 61 has a first main surface 10 and a second main surface 20. The second main surface 20 is on the opposite side of the first main surface 10. The first main surface 10 has a central region 11 and an outer peripheral region 12. The outer peripheral region 12 surrounds the central region 11.

[0071] Next, a step (S11) is performed to form a reference mark on the silicon carbide single crystal substrate. Figure 14 is a schematic cross-sectional view showing the step of forming a reference mark on the silicon carbide single crystal substrate. As shown in Figure 14, the reference mark 3 (first mark 3a) is provided in the outer peripheral region 12 of the silicon carbide single crystal substrate 61. As a result, a reference mark 3 (first mark 3a), which serves as the reference for two-dimensional position coordinates, is formed on the silicon carbide substrate 1. The silicon carbide single crystal substrate 61 on which the reference mark 3 is formed is, for example, the silicon carbide substrate according to the first to fourth embodiments.

[0072] Next, a polishing process (S12) is performed on the silicon carbide single crystal substrate. Specifically, the silicon carbide single crystal substrate 61 is subjected to mechanical polishing and chemical mechanical polishing. In the mechanical polishing process, diamond is used as the abrasive grain. In the chemical mechanical polishing process, colloidal silica is used as the abrasive grain. Polishing may be performed only on the first main surface 10 of the silicon carbide single crystal substrate 61 (single-sided polishing), or polishing may be performed on both the first main surface 10 and the second main surface 20 (double-sided polishing). By removing irregularities and distortions near the reference mark through the polishing and cleaning processes after the formation of the reference mark, the shape of the reference mark 3, which is carried over and formed on the silicon carbide epitaxial film, is prevented from being distorted. Therefore, it becomes possible to accurately distinguish the reference mark 3.

[0073] Next, a step (S13) is performed to clean the silicon carbide single crystal substrate. This removes any residue generated when forming the reference mark 3 on the silicon carbide single crystal substrate 61. As described above, after forming the reference mark 3, the reference mark formation surface of the silicon carbide substrate 1 is polished, and then the reference mark formation surface is cleaned. The reference mark formation surface corresponds to the first main surface 10. In the above description, the case in which both the step (S12) of polishing the silicon carbide single crystal substrate and the step (S13) of cleaning the silicon carbide single crystal substrate are performed has been described, but this embodiment is not limited to this. In this embodiment, it is sufficient to perform at least one of the steps (S12) of polishing the silicon carbide single crystal substrate or the step (S13) of cleaning the silicon carbide single crystal substrate.

[0074] Next, a step (S14) is performed to identify the position coordinates of a defect in the silicon carbide single crystal substrate based on reference marks. In step (S14), the defect in the silicon carbide single crystal substrate is measured based on the reference marks and its position coordinates are identified. Figure 15 is a schematic plan view showing the step of identifying the position coordinates of a defect 80 in the silicon carbide single crystal substrate 61 based on reference marks 3. As shown in Figure 15, a plurality of reference marks 3 (first marks 3a) are provided in the outer peripheral region 12 of the silicon carbide single crystal substrate 61. The plurality of reference marks 3 (first marks 3a) include a first reference mark 31a and a second reference mark 32a.

[0075] For example, the X-axis is defined as a straight line passing through the center of the first reference mark 31a and the center of the second reference mark 32a. The Y-axis is defined as a straight line parallel to the first principal plane 10 and perpendicular to the X-axis. The midpoint between the center of the first reference mark 31a and the center of the second reference mark 32a is defined as the origin of the 2D position coordinate system. The direction from the origin toward the first reference mark 31a is defined as the negative direction of the X-axis. The direction from the origin toward the second reference mark 32a is defined as the positive direction of the X-axis. The direction from the origin toward the orientation flat 2a is defined as the negative direction of the Y-axis. The direction opposite to the direction from the origin toward the orientation flat 2a is defined as the positive direction of the Y-axis. For example, a virtual 2D position coordinate system is determined based on the first reference mark 31a and the second reference mark 32a as described above.

[0076] As shown in Figure 15, the silicon carbide single crystal substrate 61 has defects 80. The defects 80 include, for example, a first defect 81 and a second defect 82. The first defect 81 is, for example, a micropipe. The second defect 82 is, for example, a stacking fault. The defects 80 may also be, for example, through-helix dislocations, through-edge dislocations, basal plane dislocations, carbon inclusions, or surface deposits. The defects 80 may be located in the central region 11 or in the peripheral region 12. The second defect 82 may be a scratch or the like.

[0077] The two-dimensional position coordinates of defect 80 are identified using a virtual two-dimensional position coordinate system determined based on reference mark 3. Specifically, if the first defect 81 exists on multiple coordinates including the first coordinate (X1, Y1), then the multiple coordinates including the first coordinate (X1, Y1) are identified as the two-dimensional position coordinates of the first defect 81. Similarly, if the second defect 82 exists on multiple coordinates including the second coordinate (X2, Y2), then the multiple coordinates including the second coordinate (X2, Y2) are identified as the two-dimensional position coordinates of the second defect 82. As described above, the position coordinates of defects 80 on the silicon carbide substrate 1 are identified based on reference mark 3 (first mark 3a). The inspection method for defects 80 is a non-destructive inspection method using, for example, photoluminescence, X-ray diffraction, surface light scattering, or polarized transmitted light.

[0078] Next, a step (S15) is performed to form a silicon carbide epitaxial film on a silicon carbide single crystal substrate. Specifically, the silicon carbide single crystal substrate 61 is placed, for example, in the deposition chamber of a CVD (Chemical Vapor Deposition) apparatus. Next, a raw material gas, a carrier gas, and a doping gas are introduced into the deposition chamber. The raw material gas includes, for example, silane (SiH4) gas and propane (C3H8) gas. The carrier gas is, for example, hydrogen. The doping gas is, for example, ammonia gas or nitrogen gas.

[0079] Figure 16 is a schematic cross-sectional view showing the process of forming a silicon carbide epitaxial film 62 on a silicon carbide single crystal substrate 61. In the deposition chamber, silane gas and propane gas are thermally decomposed to form the silicon carbide epitaxial film 62 on the first main surface 10 of the silicon carbide single crystal substrate 61. As shown in Figure 16, the silicon carbide epitaxial film 62 has a third main surface 43 and a fourth main surface 40. The third main surface 43 is in contact with the silicon carbide single crystal substrate 61.

[0080] As shown in Figure 16, the silicon carbide epitaxial film 62 in the outer peripheral region 12 is formed to fill the reference mark 3 (first mark 3a) formed on the first main surface 10. As a result, a reference mark 3 (second mark 3b) is formed in the outer peripheral region 12 of the fourth main surface 40 of the silicon carbide epitaxial film 62. The reference mark 3 (second mark 3b) formed in the outer peripheral region 12 of the fourth main surface 40 is directly above the reference mark 3 (first mark 3a) formed in the outer peripheral region 12 of the first main surface 10. The second mark 3b is formed by being carried over from the first mark 3a to the silicon carbide epitaxial film 62. The shape of the second mark 3b is substantially the same as the shape of the first mark 3a.

[0081] Reference marks 3 (first mark 3a and second mark 3b) are formed, for example, by laser processing. In laser processing, it is preferable to use, for example, a UV (ultraviolet) laser or a fiber laser. The wavelength of the laser is preferably in the range of 100 nm to 1200 nm. The depth of reference marks 3 is, for example, greater than 0.5 μm and less than 100 μm. If reference marks 3 are too shallow, they are difficult to see. If reference marks 3 are too deep, it is difficult to remove dust and dirt that get inside the reference marks 3. In this case, it is easy to create a contamination risk for subsequent processes.

[0082] It is preferable to form the reference mark 3 with multiple laser irradiations rather than in a single irradiation. However, if the desired depth can be reached with a single laser irradiation, the reference mark 3 may be formed in a single irradiation. Furthermore, focusing the laser on the processing surface allows for more precise processing of the reference mark 3.

[0083] Only a portion of the silicon carbide epitaxial film 62 provided above the reference mark 3 (first mark 3a) may be removed by etching or the like until the silicon carbide single crystal substrate 61 is exposed. By etching or the like, the reference mark 3 (first mark 3a) provided on the silicon carbide single crystal substrate 61 is exposed, making it possible to distinguish the reference mark 3 (first mark 3a) with greater accuracy. The etching of the silicon carbide epitaxial film 62 may be continued until the silicon carbide single crystal substrate 61 is exposed, or it may be stopped just before the silicon carbide single crystal substrate 61 is exposed. If the etching is stopped just before the silicon carbide single crystal substrate 61 is exposed, the silicon carbide epitaxial film 62 may remain above the reference mark 3 (first mark 3a).

[0084] Reference marks 3 (first mark 3a and second mark 3b) may be formed, for example, by etching. The etching process may involve forming a mask pattern with SiO2 on a silicon carbide single crystal substrate 61, or on a silicon carbide epitaxial film 62 provided on the silicon carbide single crystal substrate 61, and then performing plasma etching with an etching gas. Using SF6 as the etching gas is effective. The etching gas may contain O2 gas or SiF4 in addition to SF6. This allows for the formation of deep reference marks 3 (first mark 3a and second mark 3b).

[0085] Only a portion of the silicon carbide epitaxial film 62 provided above the reference mark 3 (first mark 3a) may be removed by etching or the like until the silicon carbide single crystal substrate 61 is exposed. By etching or the like, the reference mark 3 (first mark 3a) provided on the silicon carbide single crystal substrate 61 is exposed, making it possible to distinguish the reference mark 3 (first mark 3a) with greater accuracy. The etching of the silicon carbide epitaxial film 62 may be continued until the silicon carbide single crystal substrate 61 is exposed, or it may be stopped just before the silicon carbide single crystal substrate 61 is exposed. If the etching is stopped just before the silicon carbide single crystal substrate 61 is exposed, the silicon carbide epitaxial film 62 may remain above the reference mark 3 (first mark 3a).

[0086] Next, a step (S16) is performed to identify the position coordinates of defects in the silicon carbide epitaxial film based on reference marks. Figure 17 is a schematic plan view showing the step of identifying the position coordinates of defects 80 in the silicon carbide epitaxial film 62 based on reference marks 3. As shown in Figure 17, a plurality of reference marks 3 (second marks 3b) are provided in the outer peripheral region 12 of the silicon carbide epitaxial film 62. The plurality of reference marks 3 (second marks 3b) include a first reference mark 31b and a second reference mark 32b.

[0087] For example, the X-axis is defined as a straight line passing through the center of the first reference mark 31b and the center of the second reference mark 32b. The Y-axis is defined as a straight line parallel to the fourth principal plane 40 and perpendicular to the X-axis. The midpoint between the center of the first reference mark 31b and the center of the second reference mark 32b is defined as the origin of the 2D position coordinate system. The direction from the origin toward the first reference mark 31b is defined as the negative direction of the X-axis. The direction from the origin toward the second reference mark 32b is defined as the positive direction of the X-axis. The direction from the origin toward the orientation flat 2a is defined as the negative direction of the Y-axis. The direction opposite to the direction from the origin toward the orientation flat 2a is defined as the positive direction of the Y-axis. For example, a virtual 2D position coordinate system is determined based on the first reference mark 31b and the second reference mark 32b as described above.

[0088] As shown in Figure 17, defects 80 are present on the fourth main surface 40 of the silicon carbide epitaxial film 62. Defects 80 include, for example, a third defect 83 and a fourth defect 84. The third defect 83 is, for example, a triangular defect. The fourth defect 84 is, for example, a downfall. Defects 80 may also be, for example, stacking faults, carrot defects, basal plane dislocations, or surface deposits.

[0089] Next, the two-dimensional position coordinates of defect 80 are identified using a virtual two-dimensional position coordinate system determined based on reference mark 3 (second mark 3b). Specifically, if the third defect 83 exists on multiple coordinates including the third coordinate (X3, Y3), then the multiple coordinates including the third coordinate (X3, Y3) are identified as the two-dimensional position coordinates of the third defect 83. Similarly, if the fourth defect 84 exists on multiple coordinates including the fourth coordinate (X4, Y4), then the multiple coordinates including the fourth coordinate (X4, Y4) are identified as the two-dimensional position coordinates of the fourth defect 84. As described above, the position coordinates of defects 80 on the silicon carbide substrate 1 are identified based on reference mark 3 (second mark 3b).

[0090] Next, a step (S17) is performed to form an active region on the silicon carbide epitaxial film. Figure 18 is a schematic cross-sectional view showing the step of forming an active region 90 on the silicon carbide epitaxial film 62. As shown in Figure 18, a p-type impurity such as aluminum (Al) is implanted into the silicon carbide epitaxial film 62. This forms a body region 132 having a p-type conductivity. Next, an n-type impurity such as phosphorus (P) is implanted into a part of the body region 132. This forms a source region 133 having an n-type conductivity. Next, a p-type impurity such as aluminum is implanted into a part of the source region 133. This forms a contact region 134 having a p-type conductivity (see Figure 18).

[0091] In the silicon carbide epitaxial film 62, the areas other than the body region 132, source region 133, and contact region 134 become the drift region 131. The source region 133 is separated from the drift region 131 by the body region 132. Ion implantation may be performed by heating the silicon carbide substrate 1 to, for example, 300°C to 600°C. After ion implantation, activation annealing is performed on the silicon carbide epitaxial substrate 100. Activation annealing activates the impurities implanted in the silicon carbide epitaxial film 62, generating carriers in each region. The atmosphere for activation annealing may be, for example, an argon (Ar) atmosphere. The temperature for activation annealing may be, for example, around 1800°C. The time for activation annealing may be, for example, around 30 minutes.

[0092] The element active region 90 includes, for example, a body region 132, a source region 133, and a contact region 134. As described above, the element active region 90 is formed on the silicon carbide substrate 1. The element active region 90 is provided on the silicon carbide epitaxial film 62.

[0093] Next, a step (S18) is performed to identify the position coordinates of the element active region based on the reference mark. The two-dimensional position coordinates of the element active region 90 are identified using a virtual two-dimensional position coordinate system determined based on the reference mark 3 (second mark 3b). Specifically, if the element active region 90 exists on multiple coordinates, for example, including the fifth coordinate (X5, Y5), then the multiple coordinates including the fifth coordinate (X5, Y5) are identified as the two-dimensional position coordinates of the element active region 90. As described above, the position coordinates of the element active region 90 are identified based on the reference mark 3.

[0094] In the step of determining the position coordinates of the element active region based on the reference mark (S18), the reference mark 3 may be the reference mark 3 (first mark 3a) formed in the step of forming the reference mark on the silicon carbide single crystal substrate (S11), or it may be the reference mark 3 (second mark 3b) formed in the step of forming a silicon carbide epitaxial film on the silicon carbide single crystal substrate (S15). The second mark 3b is formed when the first mark 3a is succeeded by the silicon carbide epitaxial film 62. Therefore, the two-dimensional position coordinate system determined based on the first mark 3a is substantially the same as the two-dimensional position coordinate system determined based on the second mark 3b.

[0095] Next, a process (S19) is performed to determine the quality of the element active region by relating the position coordinates of the defects with the position coordinates of the element active region. Figure 19 is a schematic plan view showing the process of determining the quality of the element active region 90. In Figure 19, the element active region 90 is a plurality of regions shown as roughly squares. The area between two adjacent element active regions 90 is the dicing region 91. As shown in Figure 19, the position coordinates of the first defect 81, the second defect 82, the third defect 83, the fourth defect 84, and the position coordinates of the element active region 90 may be mapped in a two-dimensional plane.

[0096] Next, the position coordinates of the first defect 81 are compared with the position coordinates of the element active region 90. If at least a portion of the position coordinates of the first defect 81 and the position coordinates of the element active region 90 overlap, then the first defect 81 is present in the element active region 90. As shown in Figure 19, some of the element active regions 90 overlap with the first defect 81. Semiconductor elements formed in the element active region 90 that overlap with the first defect 81 are judged to be defective.

[0097] Similarly, the position coordinates of the second defect 82 are compared with the position coordinates of the element active region 90. If at least a portion of the position coordinates of the second defect 82 and the position coordinates of the element active region 90 overlap, then the second defect 82 is present in the element active region 90. As shown in Figure 19, some of the element active regions 90 overlap with the second defect 82. Semiconductor elements formed in the element active region 90 that overlap with the second defect 82 are judged to be defective.

[0098] Similarly, the position coordinates of the third defect 83 are compared with the position coordinates of the element active region 90. If at least a portion of the position coordinates of the third defect 83 and the position coordinates of the element active region 90 overlap, then the third defect 83 is present in the element active region 90. As shown in Figure 19, some of the element active regions 90 overlap with the third defect 83. Semiconductor elements formed in the element active region 90 that overlap with the third defect 83 are judged to be defective.

[0099] Similarly, the position coordinates of the fourth defect 84 are compared with the position coordinates of the element active region 90. If at least a portion of the position coordinates of the fourth defect 84 and the position coordinates of the element active region 90 overlap, then the fourth defect 84 is present in the element active region 90. As shown in Figure 19, some of the element active regions 90 overlap with the fourth defect 84. Semiconductor devices formed in the element active region 90 that overlap with the fourth defect 84 are judged to be defective.

[0100] If the position coordinates of the element active region 90 do not overlap with the position coordinates of the first defect 81, the second defect 82, the third defect 83, and the fourth defect 84, then the element active region 90 is considered to be free of the first defect 81, the second defect 82, the third defect 83, and the fourth defect 84. As shown in Figure 19, some of the element active regions 90 do not overlap with any of the first defect 81, the second defect 82, the third defect 83, and the fourth defect 84. A semiconductor element formed in an element active region 90 that does not overlap with any of the first defect 81, the second defect 82, the third defect 83, and the fourth defect 84 is judged to be a good product. As described above, the quality of the element active region 90 is determined by relating the position coordinates of the defects 80 with the position coordinates of the element active region 90.

[0101] Figure 20 is a schematic cross-sectional view showing the process of forming the gate insulating film. As shown in Figure 20, the silicon carbide substrate 1 is heated in an oxygen-containing atmosphere, thereby forming the gate insulating film 136 on the silicon carbide epitaxial film 62. The gate insulating film 136 is made of, for example, silicon dioxide (SiO2). The temperature of the thermal oxidation treatment is, for example, about 1300°C. The time of the thermal oxidation treatment is, for example, about 30 minutes.

[0102] After the gate insulating film 136 is formed, further heat treatment may be performed in a nitrogen atmosphere. For example, heat treatment may be performed in an atmosphere of nitric oxide (NO), nitrous oxide (N2O), etc., at a temperature of about 1100°C for about 1 hour. Further heat treatment may then be performed in an argon atmosphere. For example, heat treatment may be performed in an argon atmosphere at a temperature of about 1100°C to 1500°C for about 1 hour.

[0103] Next, the first electrode 141 is formed on the gate insulating film 136. The first electrode 141 functions as a gate electrode. The first electrode 141 is formed, for example, by the CVD method. The first electrode 141 is made of, for example, polysilicon containing impurities and having conductivity. The first electrode 141 is formed in a position facing the source region 133 and the body region 132.

[0104] Next, an interlayer insulating film 137 is formed. The interlayer insulating film 137 is formed to cover the first electrode 141. The interlayer insulating film 137 is formed, for example, by CVD. The interlayer insulating film 137 is composed of, for example, silicon dioxide. The interlayer insulating film 137 is formed to be in contact with the first electrode 141 and the gate insulating film 136. Next, a portion of the gate insulating film 136 and a portion of the interlayer insulating film 137 are removed by etching. As a result, the source region 133 and the contact region 134 are exposed from the gate insulating film 136.

[0105] Next, a second electrode 142 is formed. The second electrode 142 functions as a source electrode. The second electrode 142 is made of, for example, titanium, aluminum, and silicon. After the second electrode 142 is formed, the second electrode 142 and the silicon carbide substrate 1 are heated to a temperature of, for example, 900°C to 1100°C. This causes the second electrode 142 and the silicon carbide substrate 1 to make ohmic contact. Next, a wiring layer 138 is formed so as to be in contact with the second electrode 142. The wiring layer 138 is made of, for example, a material containing aluminum.

[0106] Next, a third electrode 143 is formed. The third electrode 143 functions as a drain electrode. The third electrode 143 is made of an alloy containing nickel and silicon (for example, NiSi).

[0107] Next, a dicing process is carried out. For example, the silicon carbide substrate 1 is diced along the dicing region 91, thereby dividing the silicon carbide substrate 1 into multiple semiconductor chips. In this way, the silicon carbide semiconductor device 300 is manufactured.

[0108] Figure 21 is a schematic cross-sectional view showing the configuration of the silicon carbide semiconductor device 300. As shown in Figure 21, the silicon carbide semiconductor device 300 is, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The silicon carbide semiconductor device 300 has a silicon carbide substrate 1, a first electrode 141, a second electrode 142, a third electrode 143, a gate insulating film 136, an interlayer insulating film 137, and a wiring layer 138. The silicon carbide substrate 1 has a silicon carbide single crystal substrate 61 and a silicon carbide epitaxial film 62. The silicon carbide epitaxial film 62 has a drift region 131, a source region 133, a body region 132, and a contact region 134.

[0109] In the above, a MOSFET was used as an example to describe the manufacturing method of the silicon carbide semiconductor device 300 according to this disclosure, but the manufacturing method according to this disclosure is not limited to this. The manufacturing method according to this disclosure is applicable to silicon carbide semiconductor devices 300 such as IGBTs (Insulated Gate Bipolar Transistors), SBDs (Schottky Barrier Diodes), thyristors, GTOs (Gate Turn Off thyristors), and PiN diodes.

[0110] (Seventh Embodiment) Next, a method for manufacturing the silicon carbide semiconductor device 300 according to the seventh embodiment will be described. The method for manufacturing the silicon carbide semiconductor device 300 according to the seventh embodiment differs from the method for manufacturing the silicon carbide semiconductor device 300 according to the sixth embodiment mainly in that it includes a step of adjusting the formation position of the element active region 90 based on the position coordinates of the defect 80, while the other steps are the same as those for manufacturing the silicon carbide semiconductor device 300 according to the sixth embodiment. The following description will focus on the steps that differ from those for manufacturing the silicon carbide semiconductor device 300 according to the sixth embodiment.

[0111] Figure 22 is a schematic flowchart showing the manufacturing method of the silicon carbide semiconductor device 300 according to the seventh embodiment. As shown in Figure 22, the manufacturing method of the silicon carbide semiconductor device 300 according to the seventh embodiment mainly comprises the steps of forming reference marks on a silicon carbide single crystal substrate (S21), polishing the silicon carbide single crystal substrate (S22), cleaning the silicon carbide single crystal substrate (S23), identifying the position coordinates of defects on the silicon carbide single crystal substrate based on the reference marks (S24), forming a silicon carbide epitaxial film on the silicon carbide single crystal substrate (S25), identifying the position coordinates of defects in the silicon carbide epitaxial film based on the reference marks (S26), adjusting the formation position of the element active region based on the position coordinates of the defects (S27), and determining the quality of the element active region by relating the position coordinates of the defects and the position coordinates of the element active region (S28).

[0112] First, a step (S21) is performed to form a reference mark on the silicon carbide single crystal substrate according to the seventh embodiment (S21) is the same as the step (S11) of forming a reference mark on the silicon carbide single crystal substrate according to the sixth embodiment.

[0113] Next, a step (S22) is performed to polish the silicon carbide single crystal substrate. The step (S22) for polishing the silicon carbide single crystal substrate according to the seventh embodiment is the same as the step (S12) for polishing the silicon carbide single crystal substrate according to the sixth embodiment.

[0114] Next, a step (S23) is performed to clean the silicon carbide single crystal substrate. The step (S23) for cleaning the silicon carbide single crystal substrate according to the seventh embodiment is the same as the step (S13) for cleaning the silicon carbide single crystal substrate according to the sixth embodiment.

[0115] Next, a step (S24) is performed to identify the position coordinates of a defect in the silicon carbide single crystal substrate based on a reference mark. The step (S24) of identifying the position coordinates of a defect in the silicon carbide single crystal substrate based on a reference mark according to the 7th embodiment is the same as the step (S14) of identifying the position coordinates of a defect in the silicon carbide single crystal substrate based on a reference mark according to the 6th embodiment.

[0116] Next, a step (S25) is performed to form a silicon carbide epitaxial film on a silicon carbide single crystal substrate. The step (S25) of forming a silicon carbide epitaxial film on a silicon carbide single crystal substrate according to the 7th embodiment is the same as the step (S15) of forming a silicon carbide epitaxial film on a silicon carbide single crystal substrate according to the 6th embodiment.

[0117] Next, a step (S26) is performed to identify the position coordinates of defects in the silicon carbide epitaxial film based on reference marks. The step (S26) of identifying the position coordinates of defects in the silicon carbide epitaxial film based on reference marks according to the 7th embodiment is the same as the step (S16) of identifying the position coordinates of defects in the silicon carbide epitaxial film based on reference marks according to the 6th embodiment.

[0118] Next, a step (S27) is performed to adjust the formation position of the element active region based on the position coordinates of the defects. Figure 23 is a schematic plan view showing the step of adjusting the formation position of the element active region 90 based on the position coordinates of the defect 80. In Figure 23, the roughly square region 92 shown by the dashed line is the region where the formation of the element active region 90 was planned. In the step (S24) of identifying the position coordinates of the defects in the silicon carbide single crystal substrate based on the reference marks, the two-dimensional position coordinates of the first defect 81 and the second defect 82 in the silicon carbide single crystal substrate 61 have already been identified. In the step (S26) of identifying the position coordinates of the defects in the silicon carbide epitaxial film based on the reference marks 3, the two-dimensional position coordinates of the third defect 83 and the fourth defect 84 in the silicon carbide epitaxial film 62 have already been identified.

[0119] In the step (S27) of adjusting the formation position of the element active region based on the position coordinates of the defects, the formation position of the element active region 90 is adjusted so that the element active region 90 does not overlap with each of the first defects 81, second defects 82, third defects 83, and fourth defects 84 as much as possible. From another perspective, the formation position of the element active region 90 is adjusted so that the number of element active regions 90 that overlap with each of the first defects 81, second defects 82, third defects 83, and fourth defects 84 is minimized. For example, the formation position of the element active region 90 is adjusted so that each of the first defects 81, second defects 82, third defects 83, and fourth defects 84 is formed in the dicing region 91 located between two adjacent element active regions 90. As described above, the formation position of the element active region 90 is adjusted based on the position coordinates of the defects 80. From another perspective, the formation position of the element active region 90 is optimally designed.

[0120] Next, a step (S28) is performed in which the position coordinates of the defect are associated with the position coordinates of the element active region to determine whether the element active region is good or bad. The step (S28) of associating the position coordinates of the defect with the position coordinates of the element active region to determine whether the element active region is good or bad according to the 7th embodiment is the same as the step (S19) of associating the position coordinates of the defect with the position coordinates of the element active region to determine whether the element active region is good or bad according to the 6th embodiment.

[0121] Next, the gate insulating film 136 is formed using the same method as the manufacturing method of the silicon carbide semiconductor device 300 according to the sixth embodiment (see Figure 20). Next, the first electrode 141, the second electrode 142, the interlayer insulating film 137, the wiring layer 138, and the third electrode 143 are formed using the same method as the manufacturing method of the silicon carbide semiconductor device 300 according to the sixth embodiment. Next, the silicon carbide substrate 1 is cut along the dicing region 91. This completes the manufacturing of the silicon carbide semiconductor device 300 (see Figure 21).

[0122] (Eighth embodiment) Next, a method for manufacturing the silicon carbide semiconductor device 300 according to the eighth embodiment will be described. The method for manufacturing the silicon carbide semiconductor device 300 according to the eighth embodiment differs from the method for manufacturing the silicon carbide semiconductor device 300 according to the sixth embodiment mainly in that it does not have a step of forming a reference mark 3 on the silicon carbide single crystal substrate 61, while the other steps are the same as those for manufacturing the silicon carbide semiconductor device 300 according to the sixth embodiment. The following description will focus on the steps that differ from those for manufacturing the silicon carbide semiconductor device 300 according to the sixth embodiment.

[0123] Figure 24 is a schematic flowchart showing the manufacturing method of the silicon carbide semiconductor device 300 according to the eighth embodiment. As shown in Figure 24, the manufacturing method of the silicon carbide semiconductor device 300 according to the eighth embodiment includes the steps of: forming a silicon carbide epitaxial film on a silicon carbide single crystal substrate (S31); forming reference marks on the silicon carbide epitaxial film (S32); identifying the position coordinates of defects in the silicon carbide epitaxial film based on the reference marks (S33); forming an active device region on the silicon carbide epitaxial film (S34); identifying the position coordinates of the active device region based on the reference marks (S35); and determining the quality of the active device region by relating the position coordinates of the defects and the position coordinates of the active device region (S36).

[0124] Figure 25 is a schematic cross-sectional view showing the process of preparing the silicon carbide single crystal substrate 61. As shown in Figure 25, the silicon carbide single crystal substrate 61 has a central region 11 and an outer peripheral region 12. No reference marks 3 are formed in either the central region 11 or the outer peripheral region 12.

[0125] Figure 26 is a schematic cross-sectional view showing the process of forming a silicon carbide epitaxial film 62 on a silicon carbide single crystal substrate 61. As shown in Figure 26, the silicon carbide epitaxial film 62 is formed on the silicon carbide single crystal substrate 61 by epitaxial growth. The silicon carbide epitaxial film 62 has a third main surface 43 and a fourth main surface 40. The third main surface 43 is in contact with the silicon carbide single crystal substrate 61. The fourth main surface 40 is on the opposite side of the third main surface 43.

[0126] Figure 27 is a schematic cross-sectional view showing the process of forming a reference mark 3 on a silicon carbide epitaxial film 62. As shown in Figure 27, the reference mark 3 is formed in the outer peripheral region 12 of the fourth main surface 40 of the silicon carbide epitaxial film 62.

[0127] After forming the reference mark 3, at least one of polishing or cleaning is performed on the reference mark formation surface of the silicon carbide epitaxial film 62 provided on the silicon carbide single crystal substrate 61. The reference mark formation surface corresponds to the fourth main surface 40.

[0128] Next, a step (S33) is performed to identify the position coordinates of defects in the silicon carbide epitaxial film based on reference marks. The step (S33) of identifying the position coordinates of defects in the silicon carbide epitaxial film based on reference marks according to the 8th embodiment is the same as the step (S16) of identifying the position coordinates of defects in the silicon carbide epitaxial film based on reference marks according to the 6th embodiment.

[0129] Figure 28 is a schematic cross-sectional view showing the process of forming an active element region 90 on a silicon carbide epitaxial film 62. As shown in Figure 28, an active element region 90 is formed on the silicon carbide epitaxial film 62. The active element region 90 has, for example, a body region 132, a source region 133, and a contact region 134. As described above, the reference mark 3 and the active element region 90 are each provided on the silicon carbide epitaxial film 62.

[0130] Next, a step (S35) is performed to identify the position coordinates of the element active region based on the reference marks. The step (S35) of identifying the position coordinates of the element active region based on the reference marks according to the 8th embodiment is the same as the step (S18) of identifying the position coordinates of the element active region based on the reference marks according to the 6th embodiment. Next, a step (S36) is performed to determine whether the element active region 90 is good or bad by associating the position coordinates of the defect 80 with the position coordinates of the element active region 90. The step (S36) of determining whether the element active region is good or bad by associating the position coordinates of the defect 80 with the position coordinates of the element active region according to the 8th embodiment is the same as the step (S19) of determining whether the element active region is good or bad by associating the position coordinates of the defect 80 with the position coordinates of the element active region according to the 6th embodiment.

[0131] Next, the gate insulating film 136 is formed using the same method as the manufacturing method of the silicon carbide semiconductor device 300 according to the sixth embodiment (see Figure 20). Next, the first electrode 141, the second electrode 142, the interlayer insulating film 137, the wiring layer 138, and the third electrode 143 are formed using the same method as the manufacturing method of the silicon carbide semiconductor device 300 according to the sixth embodiment. Next, the silicon carbide substrate 1 is cut along the dicing region 91. This completes the manufacturing of the silicon carbide semiconductor device 300 (see Figure 21).

[0132] (Ninth Embodiment) Next, a method for manufacturing the silicon carbide semiconductor device 300 according to the ninth embodiment will be described. The method for manufacturing the silicon carbide semiconductor device 300 according to the ninth embodiment differs from the method for manufacturing the silicon carbide semiconductor device 300 according to the eighth embodiment mainly in that reference marks 3 are formed on both the first silicon carbide epitaxial film 71 and the second silicon carbide epitaxial film 72. The other steps are the same as those for manufacturing the silicon carbide semiconductor device 300 according to the eighth embodiment. The following description will focus on the steps that differ from those for manufacturing the silicon carbide semiconductor device 300 according to the eighth embodiment.

[0133] Figure 29 is a schematic flowchart showing the manufacturing method of the silicon carbide semiconductor device 300 according to the ninth embodiment. As shown in Figure 29, the manufacturing method for the silicon carbide semiconductor device 300 according to the ninth embodiment includes the steps of: forming a first silicon carbide epitaxial film on a silicon carbide single crystal substrate (S41); forming reference marks on the first silicon carbide epitaxial film (S42); identifying the position coordinates of defects in the first silicon carbide epitaxial film based on the reference marks (S43); forming a second silicon carbide epitaxial film on the first silicon carbide epitaxial film (S44); identifying the position coordinates of defects in the second silicon carbide epitaxial film based on the reference marks (S45); forming an active device region on the second silicon carbide epitaxial film (S46); identifying the position coordinates of the active device region based on the reference marks (S47); and determining the quality of the active device region 90 by relating the position coordinates of the defects and the position coordinates of the active device region (S48).

[0134] Figure 30 is a schematic cross-sectional view showing the process of forming a first silicon carbide epitaxial film 71 on a silicon carbide single crystal substrate 61. As shown in Figure 30, the first silicon carbide epitaxial film 71 is formed on the silicon carbide single crystal substrate 61 by epitaxial growth.

[0135] Figure 31 is a schematic cross-sectional view showing the process of forming a reference mark 3 on the first silicon carbide epitaxial film 71. As shown in Figure 31, the reference mark 3 (first mark 3a) is formed in the outer peripheral region 12 of the first silicon carbide epitaxial film 71.

[0136] After forming the reference mark 3 (first mark 3a), the reference mark formation surface of the first silicon carbide epitaxial film 71 provided on the silicon carbide single crystal substrate 61 is polished or cleaned. The reference mark formation surface corresponds to the upper surface of the first silicon carbide epitaxial film 71.

[0137] Next, a step (S43) is performed to identify the position coordinates of defects in the first silicon carbide epitaxial film based on reference marks. The step (S43) of identifying the position coordinates of defects in the first silicon carbide epitaxial film based on reference marks according to the 9th embodiment is the same as the step (S33) of identifying the position coordinates of defects in the silicon carbide epitaxial film based on reference marks according to the 8th embodiment.

[0138] Figure 32 is a schematic cross-sectional view showing the process of forming a second silicon carbide epitaxial film 72 on a first silicon carbide epitaxial film 71. As shown in Figure 32, the second silicon carbide epitaxial film 72 is formed on the first silicon carbide epitaxial film 71 by epitaxial growth. A reference mark 3 (second mark 3b) is formed in the outer peripheral region 12 of the second silicon carbide epitaxial film 72. The second mark 3b is located directly above the first mark 3a.

[0139] A portion of the second silicon carbide epitaxial film 72, which is located above the reference mark 3 (first mark 3a), may be removed by etching or the like until the first silicon carbide epitaxial film 71 is exposed. By etching or the like, the reference mark 3 (first mark 3a) located on the first silicon carbide epitaxial film 71 is exposed, making it possible to distinguish the reference mark 3 (first mark 3a) with greater accuracy. The etching of the second silicon carbide epitaxial film 72 may be continued until the first silicon carbide epitaxial film 71 is exposed, or it may be stopped just before the first silicon carbide epitaxial film 71 is exposed. If the etching is stopped just before the first silicon carbide epitaxial film 71 is exposed, the second silicon carbide epitaxial film 72 may remain above the reference mark 3 (first mark 3a).

[0140] Next, a step (S45) is performed to identify the position coordinates of defects in the second silicon carbide epitaxial film based on reference marks. The step (S45) of identifying the position coordinates of defects in the second silicon carbide epitaxial film based on reference marks according to the ninth embodiment is the same as the step (S33) of identifying the position coordinates of defects in the silicon carbide epitaxial film based on reference marks according to the eighth embodiment.

[0141] Next, a step (S46) is performed to form an active device region on the second silicon carbide epitaxial film. Figure 33 is a schematic cross-sectional view showing the step of forming an active device region on the second silicon carbide epitaxial film. The step (S46) of forming an active device region on the second silicon carbide epitaxial film according to the ninth embodiment is the same as the step (S34) of forming an active device region on the silicon carbide epitaxial film according to the eighth embodiment. As shown in Figure 33, the active device region 90 is formed on the second silicon carbide epitaxial film 72. The active device region 90 may be formed on both the first silicon carbide epitaxial film 71 and the second silicon carbide epitaxial film 72.

[0142] Next, a step (S47) is performed to determine the position coordinates of the element active region based on the reference mark. The step (S47) of determining the position coordinates of the element active region based on the reference mark according to the 9th embodiment is the same as the step (S35) of determining the position coordinates of the element active region based on the reference mark according to the 8th embodiment.

[0143] Next, a step (S48) is performed in which the position coordinates of the defect are associated with the position coordinates of the element active region to determine whether the element active region is good or bad. The step (S48) in which the position coordinates of the defect are associated with the position coordinates of the element active region to determine whether the element active region is good or bad in the 9th embodiment is the same as the step (S36) in which the position coordinates of the defect are associated with the position coordinates of the element active region to determine whether the element active region is good or bad in the 8th embodiment.

[0144] Next, the gate insulating film 136 is formed using the same method as the manufacturing method of the silicon carbide semiconductor device 300 according to the sixth embodiment (see Figure 20). Next, the first electrode 141, the second electrode 142, the interlayer insulating film 137, the wiring layer 138, and the third electrode 143 are formed using the same method as the manufacturing method of the silicon carbide semiconductor device 300 according to the sixth embodiment. Next, the silicon carbide substrate 1 is cut along the dicing region 91. This completes the manufacturing of the silicon carbide semiconductor device 300 (see Figure 21).

[0145] In the manufacturing method of the silicon carbide semiconductor device 300 according to the sixth to ninth embodiments described above, the case in which the reference mark 3 is formed in the outer peripheral region 12 has been explained, but the location of the reference mark 3 is not limited to the outer peripheral region 12. Specifically, the reference mark 3 may be provided only in the central region 11, or it may be provided in both the outer peripheral region 12 and the central region 11. When the reference mark 3 is provided in the central region 11, the reference mark 3 is provided, for example, in the dicing region 91. The reference mark 3 may also be formed on the surface (first main surface 10) or the back surface (second main surface 20) of the silicon carbide single crystal substrate 61.

[0146] Next, the effects and advantages of the manufacturing method for the silicon carbide single crystal substrate 61, silicon carbide substrate 1, and silicon carbide semiconductor device 300 according to the above embodiment will be described.

[0147] According to the manufacturing method of the silicon carbide semiconductor device 300 in one aspect of the above embodiment, the position coordinates of a defect 80 in the silicon carbide substrate 1 are identified based on a reference mark 3. An element active region 90 is formed on the silicon carbide substrate 1. The position coordinates of the element active region 90 are identified based on the reference mark 3. The position coordinates of the defect 80 and the position coordinates of the element active region 90 are associated, and a quality determination of the element active region 90 is performed. By linking the position coordinates of the defect 80 and the position coordinates of the element active region 90 using common coordinates based on the reference mark 3, defective elements caused by the defect 80 can be identified with high accuracy. Therefore, the quality of the element active region 90 can be determined with high accuracy.

[0148] Furthermore, before the silicon carbide semiconductor device 300 is completed, the failure rate of elements due to defects 80 can be accurately estimated. Based on the failure rate of these elements, it becomes possible to design the optimal element structure or element arrangement.

[0149] According to the manufacturing method of the silicon carbide semiconductor device 300 according to one embodiment of the above-described embodiment, in the step of forming an element active region 90 on the silicon carbide substrate 1, the formation position of the element active region 90 may be adjusted based on the position coordinates of the defect 80. This makes it possible to form the element active region 90 while avoiding the defect 80. As a result, the yield of the element can be improved.

[0150] According to the manufacturing method of the silicon carbide semiconductor device 300 according to one embodiment of the above-described embodiment, the reference mark 3 may be provided on the silicon carbide single crystal substrate 61. The element active region 90 may be provided on the silicon carbide epitaxial film 62.

[0151] When the reference mark 3 is provided on the silicon carbide single crystal substrate 61, it is desirable to polish the surface on which the reference mark was formed in order to remove any irregularities, distortions, foreign matter such as dust, and dirt near the reference mark caused by processing, and then to clean the surface on which the reference mark was formed. The polishing may be performed only on the surface on which the reference mark was formed, or on both the surface on which the reference mark was formed and the surface on the opposite side of the surface on which the reference mark was formed.

[0152] Furthermore, only a portion of the silicon carbide epitaxial film 62 provided above the reference mark 3 may be removed by etching or the like until the silicon carbide single crystal substrate 61 is exposed. By etching or the like, the reference mark 3 provided on the silicon carbide single crystal substrate 61 is exposed, making it possible to distinguish the reference mark 3 with greater accuracy. The etching of the silicon carbide epitaxial film 62 may be continued until the silicon carbide single crystal substrate 61 is exposed, or it may be stopped just before the silicon carbide single crystal substrate 61 is exposed. If the etching is stopped just before the silicon carbide single crystal substrate 61 is exposed, the silicon carbide epitaxial film 62 may remain above the reference mark 3.

[0153] According to the manufacturing method of the silicon carbide semiconductor device 300 according to one embodiment of the above-described embodiment, the reference mark 3 and the element active region 90 may each be provided on the silicon carbide epitaxial film 62. When the reference mark 3 is provided on the silicon carbide epitaxial film 62, after the reference mark 3 is formed, the reference mark formation surface is polished or cleaned.

[0154] According to the manufacturing method of the silicon carbide semiconductor device 300 in one aspect of the above embodiment, the reference mark 3 may be formed by laser processing. If the reference mark 3 is an indentation, dust may be generated when forming the reference mark 3. By forming the reference mark 3 by laser processing, dust generation can be suppressed. Therefore, the yield of the device can be further improved. Also, if the reference mark 3 is an indentation, it is difficult to form the reference mark 3 deeply. Therefore, if polishing is performed on the reference mark formation surface to remove unevenness and distortion near the reference mark 3 that occurs when processing the reference mark 3, the reference mark 3 may disappear. In this case, it becomes difficult to distinguish the reference mark 3. By forming the reference mark 3 by laser processing, the reference mark 3 can be formed deeply. Therefore, polishing can be performed on the reference mark formation surface to remove unevenness and distortion near the reference mark 3 that occurs when processing the reference mark 3. Furthermore, the reference mark 3 can be accurately distinguished during alignment. In addition, if the reference mark 3 is an indentation, cracks may occur in the substrate on which the reference mark 3 is formed. By forming the reference mark 3 using laser processing, it is possible to suppress the occurrence of cracks in the substrate.

[0155] When the reference mark 3 is provided on the silicon carbide single crystal substrate 61, after the reference mark is formed, it is desirable to polish the surface on which the reference mark is formed in order to remove any irregularities, distortions, foreign matter such as dust, and dirt near the reference mark caused by processing, and then to clean the surface on which the reference mark is formed. Polishing may be performed only on the surface on which the reference mark is formed, or on both the surface on which the reference mark is formed and the surface opposite to the surface on which the reference mark is formed. When the reference mark 3 is provided on the silicon carbide epitaxial film 62, after the reference mark 3 is formed, polishing or cleaning is performed on the surface on which the reference mark is formed.

[0156] According to the manufacturing method of the silicon carbide semiconductor device 300 in one aspect of the above embodiment, the reference mark 3 may be formed by etching. If the reference mark 3 is an indentation, dust may be generated when forming the reference mark 3. By forming the reference mark 3 by etching, the generation of dust can be suppressed. Therefore, the yield of the device can be further improved. Also, if the reference mark 3 is an indentation, it is difficult to form the reference mark 3 deeply. Therefore, if polishing is performed on the reference mark formation surface to remove unevenness and distortion near the reference mark 3 that occurs when processing the reference mark 3, the reference mark 3 may disappear. In this case, it becomes difficult to distinguish the reference mark 3. By forming the reference mark 3 by etching, the reference mark 3 can be formed deeply. Therefore, polishing can be performed on the reference mark formation surface to remove unevenness and distortion near the reference mark 3 that occurs when processing the reference mark 3. Furthermore, the reference mark 3 can be accurately distinguished during alignment. In addition, if the reference mark 3 is an indentation, cracks may occur in the substrate on which the reference mark 3 is formed. By forming the reference mark 3 through etching, it is possible to suppress the occurrence of cracks in the substrate.

[0157] When the reference mark 3 is provided on the silicon carbide single crystal substrate 61, after the reference mark is formed, it is desirable to polish the surface on which the reference mark is formed in order to remove any irregularities, distortions, foreign matter such as dust, and dirt near the reference mark caused by processing, and then to clean the surface on which the reference mark is formed. Polishing may be performed only on the surface on which the reference mark is formed, or on both the surface on which the reference mark is formed and the surface opposite to the surface on which the reference mark is formed. When the reference mark 3 is provided on the silicon carbide epitaxial film 62, after the reference mark 3 is formed, polishing or cleaning is performed on the surface on which the reference mark is formed.

[0158] The silicon carbide substrate 1 and silicon carbide single crystal substrate 61 according to one embodiment of the above-described model include an outer peripheral edge 2 and a main surface 10. The main surface 10 is surrounded by the outer peripheral edge 2. The main surface 10 includes an outer peripheral region 12, which is a region within 5 mm from the outer peripheral edge 2, and a central region 11 surrounded by the outer peripheral region 12. The outer peripheral region 12 is provided with a plurality of reference marks 3 that serve as a reference for two-dimensional position coordinates. This makes it possible to secure a wider area for the region where the element is formed compared to the case where the reference marks 3 are provided in the central region 11.

[0159] In one embodiment of the above-described silicon carbide substrate 1 and silicon carbide single crystal substrate 61, the distance between each of the multiple reference marks 3 when viewed in a direction perpendicular to the main surface 10 may be 30 mm or more. This allows for accurate identification of the position coordinates of the defect 80.

[0160] In one embodiment of the above-described silicon carbide substrate 1 and silicon carbide single crystal substrate 61, the diameter of the smallest virtual circle surrounding each of the multiple reference marks 3, when viewed in a direction perpendicular to the main surface 10, may be greater than 10 μm and less than 3 mm. This allows for accurate identification of the reference marks 3 during alignment.

[0161] In one embodiment of the above-described silicon carbide substrate 1 and silicon carbide single crystal substrate 61, the depth of each of the multiple reference marks 3 in the direction perpendicular to the main surface 10 is preferably about 1 / 10 to 10 times the thickness of the silicon carbide epitaxial film 62. The depth of each of the multiple reference marks 3 may be, for example, greater than 0.5 μm and less than 100 μm. When the reference marks 3 are provided on the silicon carbide single crystal substrate 61, by forming reference marks of the above-described depth, even if the shape of the reference marks 3 that are carried over and formed on the silicon carbide epitaxial film 62 is somewhat distorted due to the growth conditions of the silicon carbide epitaxial film 62 (for example, growth temperature and C / Si ratio), the reference marks 3 can be accurately identified during alignment.

[0162] In one embodiment of the above-described silicon carbide substrate 1 and silicon carbide single crystal substrate 61, each of the multiple reference marks 3 may have a cross shape when viewed in a direction perpendicular to the main surface 10. This allows for accurate identification of the reference marks 3 during alignment.

[0163] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims rather than the foregoing description and is intended to include the meaning of equivalents of the claims and all modifications within the scope. [Explanation of symbols]

[0164] 1 Silicon carbide substrate, 2 Outer edge, 2a Orientation flat, 2b Arc-shaped part, 3 Reference mark, 3a First mark, 3b Second mark, 10 First main surface (main surface), 11, 41 Central region, 12, 42 Outer region, 20 Second main surface, 30 Recess, 31, 31a, 31b First reference mark, 32, 32a, 32b Second reference mark, 33 Third reference mark, 34 Fourth reference mark, 40 Fourth main surface, 43 Third main surface, 52 Side surface, 53 Bottom surface, 54 Groove, 61 Single crystal substrate, 62 Silicon carbide epitaxial film, 71 First silicon carbide epitaxial film, 72 Second silicon carbide epitaxial film, 80 Defect, 81 First defect, 82 Second defect, 83 Third defect, 84 Fourth defect, 90 Element active region, 91 Dicing region, 92 Region, 100 Silicon carbide epitaxial substrate, 131 Drift region, 132 Body region, 133 Source region, 134 Contact region, 136 Gate insulating film, 137 Interlayer insulating film, 138 Wiring layer, 141 First electrode, 142 Second electrode, 143 Third electrode, 300 Silicon carbide semiconductor device, A Distance, D Depth, R1 First virtual circle, R2 Second virtual circle, W1 Maximum diameter, W2 Spacing, W3 Third length, W4 Fourth width, W5 Fifth width, X First direction, Y Second direction.

Claims

1. A step of forming a first reference mark that serves as the reference for two-dimensional position coordinates on a silicon carbide single crystal substrate, After the step of forming the first reference mark, the step of polishing and cleaning the first reference mark formation surface of the silicon carbide single crystal substrate, A step of identifying the position coordinates of a defect in the silicon carbide single crystal substrate based on the first reference mark, After the polishing and cleaning steps, a silicon carbide epitaxial film is formed on the silicon carbide single crystal substrate, and a second reference mark, whose shape inherits the shape of the first reference mark, is formed on the silicon carbide epitaxial film. The process of forming an active region on the silicon carbide epitaxial film, A step of determining the position coordinates of the element active region based on the second reference mark, A method for manufacturing a silicon carbide semiconductor device, comprising the step of associating the position coordinates of the defect with the position coordinates of the element active region to determine whether the element active region is good or bad.

2. A method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein in the step of forming an active region on the silicon carbide epitaxial film, the position of the active region is adjusted based on the position coordinates of the defect.

3. The method for manufacturing a silicon carbide semiconductor device according to claim 1 or claim 2, wherein the first reference mark is formed by laser processing.

4. The method for manufacturing a silicon carbide semiconductor device according to claim 1 or claim 2, wherein the first reference mark is formed by etching.

5. A silicon carbide substrate comprising a silicon carbide single crystal substrate and a silicon carbide epitaxial film provided on the silicon carbide single crystal substrate, With an outer edge, The silicon carbide single crystal substrate has a first main surface surrounded by the outer edge, The silicon carbide epitaxial film has a second main surface surrounded by the outer peripheral edge, The first main surface includes a first outer peripheral region which is the area within 5 mm from the outer peripheral edge, and a first central region enclosed by the first outer peripheral region. The second main surface includes a second outer peripheral region which is the area within 5 mm from the outer peripheral edge, and a second central region enclosed by the second outer peripheral region. The first outer region is provided with a plurality of first reference marks that serve as the basis for two-dimensional position coordinates. The second outer region is provided with a plurality of second reference marks that serve as the basis for two-dimensional position coordinates. A silicon carbide substrate in which the plurality of second reference marks are formed by being carried over from the plurality of first reference marks to the silicon carbide epitaxial film.

6. The silicon carbide substrate according to claim 5, wherein, when viewed in a direction perpendicular to the first main surface, the distance between each of the plurality of first reference marks is 30 mm or more.

7. The silicon carbide substrate according to claim 5 or 6, wherein, when viewed in a direction perpendicular to the first main surface, the diameter of the smallest virtual circle surrounding each of the plurality of first reference marks is greater than 10 μm and less than 3 mm.

8. The silicon carbide substrate according to claim 5 or claim 6, wherein, in a direction perpendicular to the first main surface, the depth of each of the plurality of first reference marks is greater than 0.5 μm and less than 100 μm.

9. The silicon carbide substrate according to claim 5 or 6, wherein, when viewed in a direction perpendicular to the first main surface, each of the plurality of first reference marks has a cross shape.

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