Method of manufacturing silicon carbide substrate, method of manufacturing silicon carbide epitaxial substrate, and method of manufacturing silicon carbide semiconductor device

Abstract

To provide a method of manufacturing a silicon carbide substrate, the method enabling reduction of time necessary for cutting a silicon carbide crystal, a method of manufacturing a silicon carbide epitaxial substrate, and a method of manufacturing a silicon carbide semiconductor device.SOLUTION: A method of manufacturing a silicon carbide substrate has the following steps. A plurality of silicon carbide crystals are installed in a cutting device. The plurality of silicon carbide crystals are cut using a cutting device. In a step of cutting a plurality of silicon carbide crystals, the plurality of silicon carbide crystals are cut simultaneously while a flat plate is arranged between two adjacent silicon carbide crystals belonging to the plurality of silicon carbide crystals.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a silicon carbide substrate, a method for manufacturing a silicon carbide epitaxial substrate, and a method for manufacturing a silicon carbide semiconductor device. [Background technology]

[0002] Japanese Patent Application Publication No. 2013-258243 (Patent Document 1) describes a method for manufacturing a compound semiconductor substrate, including a step of holding a plurality of ingots made of a compound semiconductor with a plurality of holding parts, a step of adjusting the attitude of each of the plurality of ingots by adjusting the inclination of each of the holding surfaces of the plurality of holding parts, and a step of cutting each of the plurality of ingots simultaneously to extract a compound semiconductor substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-258243 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a method for manufacturing a silicon carbide substrate, a method for manufacturing a silicon carbide epitaxial substrate, and a method for manufacturing a silicon carbide semiconductor device that are capable of shortening the time required to cut a silicon carbide crystal. [Means for solving the problem]

[0005] A method for manufacturing a silicon carbide substrate according to the present disclosure includes the following steps: A plurality of silicon carbide crystals are placed in a cutting device; The plurality of silicon carbide crystals are cut using the cutting device; In the step of cutting the plurality of silicon carbide crystals, the plurality of silicon carbide crystals are simultaneously cut in a state in which a flat plate is disposed between two adjacent silicon carbide crystals among the plurality of silicon carbide crystals. Effect of the Invention

[0006] Advantageous Effects of Invention The present disclosure can provide a method for manufacturing a silicon carbide substrate, a method for manufacturing a silicon carbide epitaxial substrate, and a method for manufacturing a silicon carbide semiconductor device that are capable of shortening the time required to cut a silicon carbide crystal. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic plan view showing the configuration of a silicon carbide substrate in accordance with the present embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a schematic cross-sectional view for explaining the plane orientation. [Figure 4] FIG. 4 is a flow diagram illustrating roughly the method for manufacturing a silicon carbide substrate according to the present embodiment. [Diagram 5] FIG. 5 is a schematic plan view showing a step of preparing a plurality of silicon carbide crystals. [Figure 6] FIG. 6 is a schematic side view showing a step of preparing a plurality of silicon carbide crystals. [Figure 7] FIG. 7 is a schematic plan view showing measurement positions for thickness variation in the first silicon carbide crystal. [Figure 8] FIG. 8 is a schematic front view showing a step of placing a plurality of silicon carbide crystals on a cutting device. [Figure 9] FIG. 9 is a schematic cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 10 is a schematic plan view showing measurement positions for the thickness variation of the first flat plate. [Figure 11] FIG. 11 is a cross-sectional view illustrating a step of cutting a plurality of silicon carbide crystals. [Figure 12] FIG. 12 is a flow diagram illustrating a schematic method for manufacturing a silicon carbide semiconductor device according to this embodiment. [Figure 13] FIG. 13 is a cross-sectional view illustrating a configuration of a silicon carbide epitaxial substrate according to this embodiment. [Figure 14]FIG. 14 is a schematic cross-sectional view showing a step of forming a body region. [Figure 15] FIG. 15 is a schematic cross-sectional view showing a step of forming a source region. [Figure 16] FIG. 16 is a schematic cross-sectional view showing a step of forming a trench in the ninth main surface of the silicon carbide epitaxial layer. [Figure 17] FIG. 17 is a schematic cross-sectional view showing a step of forming a gate insulating film. [Figure 18] FIG. 18 is a schematic cross-sectional view showing a step of forming a gate electrode and an interlayer insulating film. [Figure 19] FIG. 19 is a schematic cross-sectional view showing the configuration of a silicon carbide semiconductor device in accordance with this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. In the crystallographic description in this specification, individual orientations are indicated with [], collective orientations with <>, individual planes with (), and collective planes with {}. In addition, for negative indices, in crystallography, a "-" (bar) is placed above the number, but in this specification, a negative sign is placed before the number.

[0009] (1) A method for manufacturing silicon carbide substrate 100 according to the present disclosure includes the following steps. A plurality of silicon carbide crystals 200 are placed on cutting apparatus 500. The plurality of silicon carbide crystals 200 are cut using cutting apparatus 500. In the step of cutting the plurality of silicon carbide crystals 200, the plurality of silicon carbide crystals 200 are simultaneously cut with flat plate 90 disposed between two adjacent silicon carbide crystals 200 among the plurality of silicon carbide crystals 200.

[0010] (2) According to the method for manufacturing silicon carbide substrate 100 in accordance with (1) above, variation in thickness of flat plate 90 may be 500 μm or less.

[0011] (3) According to the method for manufacturing silicon carbide substrate 100 relating to (1) or (2) above, the plurality of silicon carbide crystals 200 may have a first silicon carbide crystal 210 and a second silicon carbide crystal 220. First silicon carbide crystal 210 may have a first main surface 11. Second silicon carbide crystal 220 may have a second main surface 22. Flat plate 90 may have a first surface 71 and a second surface 72. Second surface 72 may be opposite first surface 71. In a process of placing multiple silicon carbide crystals 200 in a cutting apparatus 500, the first silicon carbide crystal 210, the second silicon carbide crystal 220, and the flat plate 90 are placed in the cutting apparatus 500 so that the first surface 71 is in contact with the first main surface 11 and the second surface 72 is in contact with the second main surface 22, and the inclination of the {0001} plane orientation of the second main surface 22 relative to the {0001} plane orientation of the first main surface 11 may be within 0.5°.

[0012] (4) According to the method for manufacturing silicon carbide substrate 100 relating to (3) above, the variation in thickness of first silicon carbide crystal 210 may be 500 μm or less.

[0013] (5) According to the method for manufacturing silicon carbide substrate 100 according to any one of (1) to (4) above, cutting apparatus 500 may have a holding member 50. The plurality of silicon carbide crystals 200 and flat plate 90 may be held by holding member 50.

[0014] (6) A method for manufacturing a silicon carbide epitaxial substrate 300 according to the present disclosure includes the following steps. A silicon carbide substrate 100 is prepared using the method for manufacturing a silicon carbide substrate 100 according to any one of (1) to (5) above. A silicon carbide epitaxial layer 40 is formed on the silicon carbide substrate 100.

[0015] (7) A method for manufacturing a silicon carbide semiconductor device 400 according to the present disclosure has the following steps. A silicon carbide substrate 100 is prepared using a method for manufacturing a silicon carbide substrate 100 according to any one of (1) to (5) above. A silicon carbide epitaxial layer 40 is formed on the silicon carbide substrate 100. An electrode 127 is formed on the silicon carbide epitaxial layer 40.

[0016] [Details of the embodiment of the present disclosure] Hereinafter, the details of the embodiments of the present disclosure will be described with reference to the drawings. Note that in the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

[0017] (Silicon carbide substrate) First, a configuration of a silicon carbide substrate 100 in accordance with this embodiment will be described. Fig. 1 is a plan view schematic diagram showing the configuration of a silicon carbide substrate 100 in accordance with this embodiment.

[0018] As shown in FIG. 1, the silicon carbide substrate 100 according to this embodiment has a seventh main surface 1 and a first outer peripheral side surface 9. The seventh main surface 1 extends along each of a first direction 101 and a second direction 102. The first direction 101 is not particularly limited, but is, for example, the <11-20> direction. The second direction 102 is not particularly limited, but is, for example, the <1-100> direction. The silicon carbide substrate 100 is made of, for example, hexagonal silicon carbide. The polytype of the hexagonal silicon carbide constituting the silicon carbide substrate 100 is, for example, 4H. The silicon carbide substrate 100 contains an n-type impurity such as nitrogen.

[0019] As shown in FIG. 1, the first outer peripheral side surface 9 has a first orientation flat portion 7 and a first arc-shaped portion 8. The first arc-shaped portion 8 is continuous with the first orientation flat portion 7. As shown in FIG. 1, when viewed along a straight line perpendicular to the seventh main surface 1, the first orientation flat portion 7 extends along a first direction 101. The seventh main surface 1 includes a first center O1. The first center O1 is the center of a circle that includes an arc along the first arc-shaped portion 8.

[0020] The diameter W1 of the seventh main surface 1 is, for example, 150 mm. The diameter W1 is not particularly limited, but may be, for example, 150 mm or more, or 200 mm or more. The diameter W1 is not particularly limited, but may be, for example, 300 mm or less. When viewed along a straight line perpendicular to the seventh main surface 1, the diameter W1 is the longest straight line distance between two different points on the first outer peripheral side surface 9.

[0021] FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1. The cross section shown in FIG. 2 is perpendicular to the seventh main surface 1 and parallel to the first direction 101. As shown in FIG. 2, the silicon carbide substrate 100 according to this embodiment has an eighth main surface 2. The eighth main surface 2 is opposite to the seventh main surface 1. The direction from the seventh main surface 1 to the eighth main surface 2 is defined as a third direction 103. The third direction 103 is perpendicular to each of the first direction 101 and the second direction 102. The thickness direction of the silicon carbide substrate 100 is the same as the third direction 103. The thickness (first thickness H1) of the silicon carbide substrate 100 in the third direction 103 is, for example, not less than 300 μm and not more than 700 μm.

[0022] The seventh main surface 1 is a surface tilted in an off direction with respect to the {0001} plane or the {0001} plane. Specifically, the seventh main surface 1 may be a surface tilted in an off direction with respect to the (0001) plane or the (0001) plane. The seventh main surface 1 may be a surface tilted in an off direction with respect to the (000-1) plane or the (000-1) plane. The off direction may be, for example, a first direction 101 or a second direction 102.

[0023] (face orientation) Next, a method for measuring the {0001} plane orientation will be described. The {0001} plane orientation at any position in the seventh main surface 1 can be measured by, for example, X-ray diffraction. For example, Cu-Kα1 is used as the X-ray source, and the (0004) peak is measured. The wavelength is 1.5405 angstroms (monochromatic). In other words, the wavelength is 0.15405 nm. The spot diameter of the X-ray is, for example, 3 mm. For example, at the first center O1, the {0001} plane orientation is measured by X-rays. The {0001} plane orientation is a direction perpendicular to the {0001} plane.

[0024] 3 is a schematic cross-sectional view for explaining the plane orientation. As shown in FIG. 3, the {0001} plane orientation (first plane orientation D1) at the first center O1 of the seventh main surface 1 is shifted from, for example, the normal direction (first normal direction N1) of the seventh main surface 1 at the first center O1. The angle between the first plane orientation D1 and the first normal direction N1 is set to be a first angle θ1. The first angle θ1 is the inclination angle of the seventh main surface 1 with respect to the {0001} plane. In other words, the first angle θ1 is the off angle of the silicon carbide substrate 100. When the first angle θ1 is 0°, the seventh main surface 1 is a {0001} plane.

[0025] The first angle θ1 is, for example, not less than 0° and not more than 8°. The first angle θ1 may be different from a desired off angle of silicon carbide substrate 100. The absolute value of the difference between the first angle θ1 and the desired off angle of silicon carbide substrate 100 is, for example, not more than 0.5°.

[0026] (Method for manufacturing silicon carbide substrate) Next, a method for manufacturing a silicon carbide substrate according to this embodiment will be described. Fig. 4 is a flow chart that outlines the method for manufacturing a silicon carbide substrate according to this embodiment.

[0027] As shown in FIG. 4, the manufacturing method of the silicon carbide substrate 100 according to this embodiment mainly includes a step (S10) of preparing a plurality of silicon carbide crystals, a step (S20) of placing the plurality of silicon carbide crystals in a cutting device, a step (S30) of adjusting the postures of the plurality of silicon carbide crystals, and a step (S40) of cutting the plurality of silicon carbide crystals.

[0028] First, a step (S10) of preparing a plurality of silicon carbide crystals is carried out. For example, a sublimation method is used to manufacture a plurality of silicon carbide crystals 200. Specifically, for example, a seed crystal made of single crystal silicon carbide and a silicon carbide raw material made of solid polycrystalline silicon carbide powder are placed in a container made of graphite.

[0029] The silicon carbide raw material is sublimated, and the sublimated silicon carbide gas is recrystallized on the seed crystal, whereby the silicon carbide crystal grows on the seed crystal. While the silicon carbide crystal is growing, nitrogen, for example, which serves as a donor, is introduced. As a result, the silicon carbide crystal contains, for example, nitrogen. The silicon carbide crystal is subjected to peripheral grinding and surface grinding. By repeating the above-mentioned manufacturing of the silicon carbide crystal, a plurality of silicon carbide crystals 200 are manufactured. Each of the plurality of silicon carbide crystals 200 is made of, for example, hexagonal silicon carbide. The polytype of the hexagonal silicon carbide constituting each of the plurality of silicon carbide crystals 200 is, for example, 4H.

[0030] Fig. 5 is a schematic plan view showing the step (S10) of preparing a plurality of silicon carbide crystals. Fig. 6 is a schematic side view showing the step (S10) of preparing a plurality of silicon carbide crystals. As shown in Figs. 5 and 6, the plurality of silicon carbide crystals 200 have, for example, a first silicon carbide crystal 210, a second silicon carbide crystal 220, and a third silicon carbide crystal 230.

[0031] As shown in Fig. 5 and Fig. 6, first silicon carbide crystal 210 has first main surface 11, third main surface 12, and second outer peripheral side surface 19. First main surface 11 extends along each of first direction 101 and second direction 102. Third main surface 12 is opposite first main surface 11. Second outer peripheral side surface 19 is continuous with each of first main surface 11 and third main surface 12. Second outer peripheral side surface 19 has second orientation flat portion 17 and second arc-shaped portion 18. Second arc-shaped portion 18 is continuous with second orientation flat portion 17.

[0032] 5, the second orientation flat portion 17 extends along a first direction 101 when viewed along a straight line perpendicular to the first main surface 11. The first main surface 11 includes a second center O2. The second center O2 is the center of a circle that includes an arc along the second arc-shaped portion 18.

[0033] 6, the thickness (second thickness H2) of the first silicon carbide crystal 210 in the third direction 103 is, for example, not less than 0.5 cm and not more than 10 cm. The angle formed by the {0001} plane orientation (second plane orientation D2) at the second center O2 of the first main surface 11 and the normal direction (second normal direction N2) of the first main surface 11 at the second center O2 is defined as a second angle θ2. The second angle θ2 is the inclination angle of the first main surface 11 with respect to the {0001} plane. In other words, the second angle θ2 is the off-angle of the first silicon carbide crystal 210.

[0034] Second angle θ2 may be different from a desired off angle of silicon carbide substrate 100 (see FIGS. 1 and 2). The absolute value of the difference between second angle θ2 and the desired off angle of silicon carbide substrate 100 is, for example, 0.1° or less.

[0035] As shown in Fig. 5 and Fig. 6, the second silicon carbide crystal 220 has a fourth main surface 21, a second main surface 22, and a third outer peripheral side surface 29. The fourth main surface 21 extends along each of the first direction 101 and the second direction 102. The second main surface 22 is opposite the fourth main surface 21. The third outer peripheral side surface 29 is continuous with each of the fourth main surface 21 and the second main surface 22. The third outer peripheral side surface 29 has a third orientation flat portion 27 and a third arc-shaped portion 28. The third arc-shaped portion 28 is continuous with the third orientation flat portion 27.

[0036] 5, when viewed along a straight line perpendicular to the fourth main surface 21, the third orientation flat portion 27 extends along the first direction 101. The fourth main surface 21 includes a third center O3. The third center O3 is the center of a circle that includes an arc along the third arc-shaped portion 28.

[0037] 6, the thickness (third thickness H3) of the second silicon carbide crystal 220 in the third direction 103 is, for example, not less than 0.5 cm and not more than 10 cm. The third thickness H3 may be different from the second thickness H2. The angle formed by the {0001} plane orientation (third plane orientation D3) at the third center O3 of the fourth main surface 21 and the normal direction (third normal direction N3) of the fourth main surface 21 at the third center O3 is defined as a third angle θ3. The third angle θ3 is the inclination angle of the fourth main surface 21 with respect to the {0001} plane. In other words, the third angle θ3 is the off-angle of the second silicon carbide crystal 220.

[0038] The third angle θ3 may be different from the second angle θ2. The third angle θ3 may be different from a desired off angle of silicon carbide substrate 100 (see FIGS. 1 and 2). The absolute value of the difference between the third angle θ3 and the desired off angle of silicon carbide substrate 100 is, for example, 0.1° or less.

[0039] As shown in Fig. 5 and Fig. 6, the third silicon carbide crystal 230 has a fifth main surface 31, a sixth main surface 32, and a fourth outer peripheral side surface 39. The fifth main surface 31 extends along each of the first direction 101 and the second direction 102. The sixth main surface 32 is opposite the fifth main surface 31. The fourth outer peripheral side surface 39 is continuous with each of the fifth main surface 31 and the sixth main surface 32. The fourth outer peripheral side surface 39 has a fourth orientation flat portion 37 and a fourth arc-shaped portion 38. The fourth arc-shaped portion 38 is continuous with the fourth orientation flat portion 37.

[0040] 5, the fourth orientation flat portion 37 extends along the first direction 101 when viewed along a straight line perpendicular to the fifth main surface 31. The fifth main surface 31 includes a fourth center O4. The fourth center O4 is the center of a circle that includes an arc along the fourth arc-shaped portion 38.

[0041] 6, the thickness (fourth thickness H4) of the third silicon carbide crystal 230 in the third direction 103 is, for example, not less than 0.5 cm and not more than 10 cm. The fourth thickness H4 may be different from the second thickness H2. The angle between the {0001} plane orientation (fourth plane orientation D4) at the fourth center O4 of the fifth main surface 31 and the normal direction (fourth normal direction N4) of the fifth main surface 31 at the fourth center O4 is defined as a fourth angle θ4. The fourth angle θ4 is the inclination angle of the fifth main surface 31 with respect to the {0001} plane. In other words, the fourth angle θ4 is the off-angle of the third silicon carbide crystal 230.

[0042] Fourth angle θ4 may be different from each of second angle θ2 and third angle θ3. Fourth angle θ4 may be different from a desired off angle of silicon carbide substrate 100 (see FIGS. 1 and 2). The absolute value of the difference between fourth angle θ4 and the desired off angle of silicon carbide substrate 100 is, for example, 0.1° or less. The {0001} plane orientation of each of the plurality of silicon carbide crystals 200 can be measured using the plane orientation measuring method described above.

[0043] Next, a description will be given of the thickness variation of each of the plurality of silicon carbide crystals 200. Fig. 7 is a schematic plan view showing measurement positions for the thickness variation of first silicon carbide crystals 210. In the following, a method for measuring the thickness variation of first silicon carbide crystals 210 will be described as an example.

[0044] As shown in FIG. 7, a first outer peripheral region 16 and a first central region 15 are assumed in the first main surface 11. The first outer peripheral region 16 is a region within 5 mm from the outer edge of the first main surface 11. From another perspective, when viewed along a straight line perpendicular to the first main surface 11, the distance (third distance E3) between the outer edge of the first main surface 11 and the boundary between the first outer peripheral region 16 and the first central region 15 is 5 mm. The first central region 15 is surrounded by the first outer peripheral region 16. The first central region 15 is continuous with the first outer peripheral region 16. The first central region 15 includes a second center O2.

[0045] A plurality of first measurement points 81 are located on the first main surface 11. The number of the first measurement points 81 is nine. Specifically, the plurality of first measurement points 81 are located on a first virtual line 95 passing through the second center O2 and parallel to the first direction 101, and on a second virtual line 96 passing through the second center O2 and parallel to the second direction 102. More specifically, four first measurement points 81 are located on the intersections of the first virtual line 95 and the second virtual line 96 with the boundary between the first outer peripheral region 16 and the first central region 15. Four first measurement points 81 are located on the first virtual line 95 and the second virtual line 96, and on the midpoints between the second center O2 and the boundary between the first outer peripheral region 16 and the first central region 15. One first measurement point 81 is located on the second center O2.

[0046] At each of the plurality of first measurement points 81, the thickness of first silicon carbide crystal 210 is measured using, for example, a micrometer. The average value of the thickness of first silicon carbide crystal 210 is calculated by dividing the total value of the thickness at each of the plurality of first measurement points 81 by the number of first measurement points 81. The absolute value of the value obtained by subtracting the average value from the thickness at each of the plurality of first measurement points 81 is calculated. The maximum of these absolute values ​​is taken to be the thickness variation of first silicon carbide crystal 210.

[0047] The thickness variations of the second silicon carbide crystal 220 and the third silicon carbide crystal 230 can be measured using a method similar to the method for measuring the thickness variation of the first silicon carbide crystal 210 described above.

[0048] The thickness variation of first silicon carbide crystal 210 is, for example, 500 μm or less. The thickness variation of first silicon carbide crystal 210 may be, for example, 10 μm or more, or 50 μm or more. The thickness variation of first silicon carbide crystal 210 may be, for example, 300 μm or less, or 100 μm or less.

[0049] The thickness variation of second silicon carbide crystal 220 is, for example, 500 μm or less. The thickness variation of second silicon carbide crystal 220 may be, for example, 10 μm or more, or 50 μm or more. The thickness variation of second silicon carbide crystal 220 may be, for example, 300 μm or less, or 100 μm or less.

[0050] The thickness variation of third silicon carbide crystal 230 is, for example, 500 μm or less. The thickness variation of third silicon carbide crystal 230 may be, for example, 10 μm or more, or 50 μm or more. The thickness variation of third silicon carbide crystal 230 may be, for example, 300 μm or less, or 100 μm or less.

[0051] Next, a step (S20) of placing the plurality of silicon carbide crystals in a cutting device is performed. Fig. 8 is a schematic front view showing the step of placing the plurality of silicon carbide crystals in the cutting device. Fig. 9 is a schematic cross-sectional view taken along line IX-IX in Fig. 8.

[0052] As shown in Figures 8 and 9, cutting device 500 has holding member 50, fixing jig 60, and multiple wires 70. Holding member 50 has holding surface 51 and mounting surface 52. Holding member 50 is formed, for example, from an integrated part. Fixing jig 60 is configured to be able to adjust the attitude of holding member 50 and multiple silicon carbide crystals 200. Each of multiple wires 70 is, for example, a brass-plated piano wire made of carbon steel or the like.

[0053] 8, the direction in which each of the multiple wires 70 extends is a fourth direction 104. The fourth direction 104 is inclined, for example, with respect to each of the first direction 101 and the second direction 102. The inclination angle of the fourth direction 104 with respect to the first direction 101 is, for example, 45°. The direction from the multiple wires 70 toward the fixing jig 60 is a cutting direction 109.

[0054] 9, in the step (S20) of placing a plurality of silicon carbide crystals in a cutting device, a plurality of flat plates 90 are prepared. The plurality of flat plates 90 include a first flat plate 91 and a second flat plate 92, for example.

[0055] The first flat plate 91 has a first surface 71 and a second surface 72. The second surface 72 is opposite to the first surface 71. The shape of the first flat plate 91 is not particularly limited, but is, for example, a disk shape. The Mohs hardness of the material constituting the first flat plate 91 is lower than the Mohs hardness of the multiple silicon carbide crystals 200. The first flat plate 91 is, for example, made of ceramic. The value obtained by dividing the thickness (fifth thickness H5) of the first flat plate 91 in the third direction 103 by the thickness (second thickness H2) of the first silicon carbide crystals 210 is, for example, not less than 0.5 and not more than 3.

[0056] The thickness variation of the first flat plate 91 is, for example, 500 μm or less. The thickness variation of the first flat plate 91 may be, for example, 10 μm or more, or 50 μm or more. The thickness variation of the first flat plate 91 may be, for example, 300 μm or less, or 100 μm or less.

[0057] FIG. 10 is a schematic plan view showing the measurement position of the thickness variation of the first flat plate 91. The thickness variation of the first flat plate 91 can be measured using a method similar to the above-mentioned thickness variation measurement method. Specifically, as shown in FIG. 10, the second outer peripheral region 26 and the second central region 25 are assumed in the first surface 71. The second outer peripheral region 26 is a region within 5 mm from the outer edge of the first surface 71. From another perspective, the distance (fourth distance E4) between the outer edge of the first surface 71 and the boundary between the second outer peripheral region 26 and the second central region 25 is 5 mm when viewed along a straight line perpendicular to the first surface 71. The second central region 25 is surrounded by the second outer peripheral region 26. The second central region 25 is continuous with the second outer peripheral region 26. The second central region 25 includes the center (fifth center O5) of the first surface 71.

[0058] A plurality of second measurement points 82 are located on the first surface 71. The number of the second measurement points 82 is nine. Specifically, the plurality of second measurement points 82 are located on a third imaginary line 97 passing through the fifth center O5 and parallel to the first direction 101, and on a fourth imaginary line 98 passing through the fifth center O5 and parallel to the second direction 102. More specifically, four second measurement points 82 are located on the intersections of the third imaginary line 97 and the fourth imaginary line 98 with the boundary between the second outer peripheral region 26 and the second central region 25. Four second measurement points 82 are located on the third imaginary line 97 and the fourth imaginary line 98, and on the midpoint between the fifth center O5 and the boundary between the second outer peripheral region 26 and the second central region 25. One second measurement point 82 is located on the fifth center O5.

[0059] The thickness of the first flat plate 91 is measured at each of the second measurement points 82, for example using a micrometer. The average thickness of the first flat plate 91 is calculated by dividing the sum of the thicknesses at each of the second measurement points 82 by the number of the second measurement points 82. The absolute value of the value obtained by subtracting the average from the thickness at each of the second measurement points 82 is calculated. The maximum of the absolute values ​​is regarded as the thickness variation of the first flat plate 91.

[0060] As shown in FIG. 9 , the second flat plate 92 has a third surface 73 and a fourth surface 74. The fourth surface 74 is opposite to the third surface 73. The shape of the second flat plate 92 is not particularly limited, but is, for example, a disk shape. The hardness of the material constituting the second flat plate 92 is lower than the hardness of the plurality of silicon carbide crystals 200. The second flat plate 92 is, for example, made of ceramic. The thickness (sixth thickness H6) of the second flat plate 92 in the third direction 103 may be different from the fifth thickness H5. The value obtained by dividing the sixth thickness H6 by the thickness (third thickness H3) of the second silicon carbide crystals 220 is, for example, not less than 0.25 and not more than 3.

[0061] The thickness variation of the second flat plate 92 is 500 μm or less. The thickness variation of the second flat plate 92 may be, for example, 10 μm or more, or 50 μm or more. The thickness variation of the second flat plate 92 may be, for example, 300 μm or less, or 100 μm or less. The thickness variation of the second flat plate 92 can be measured using the method for measuring the thickness variation of the first flat plate 91 described above.

[0062] In the step (S20) of placing the plurality of silicon carbide crystals in the cutting device, the plurality of silicon carbide crystals 200 and the plurality of flat plates 90 are held by holding member 50. Specifically, each of the plurality of silicon carbide crystals 200 and each of the plurality of flat plates 90 are fixed to holding surface 51 of holding member 50 using, for example, an adhesive (not shown).

[0063] Specifically, the first silicon carbide crystal 210 and the second silicon carbide crystal 220 are arranged adjacent to each other. The first flat plate 91 is arranged between the first silicon carbide crystal 210 and the second silicon carbide crystal 220. With the first flat plate 91 sandwiched between the first silicon carbide crystal 210 and the second silicon carbide crystal 220, the first silicon carbide crystal 210, the second silicon carbide crystal 220 and the first flat plate 91 are fixed to the holding member 50.

[0064] Similarly, second silicon carbide crystal 220 and third silicon carbide crystal 230 are arranged adjacent to each other. Second flat plate 92 is arranged between second silicon carbide crystal 220 and third silicon carbide crystal 230. With second flat plate 92 sandwiched between second silicon carbide crystal 220 and third silicon carbide crystal 230, second silicon carbide crystal 220, third silicon carbide crystal 230, and second flat plate 92 are fixed to holding member 50.

[0065] As a result of the above, first silicon carbide crystal 210, second silicon carbide crystal 220, and first flat plate 91 are placed in cutting apparatus 500 so that first surface 71 is in contact with first main surface 11 and second surface 72 is in contact with second main surface 22. Similarly, second silicon carbide crystal 220, third silicon carbide crystal 230, and second flat plate 92 are placed in cutting apparatus 500 so that third surface 73 is in contact with fourth main surface 21 and fourth surface 74 is in contact with sixth main surface 32. Second orientation flat portion 17, third orientation flat portion 27, and fourth orientation flat portion 37 (see FIG. 5) are arranged to be substantially parallel to each other.

[0066] With the first silicon carbide crystal 210, the second silicon carbide crystal 220, and the first flat plate 91 placed in the cutting apparatus 500, the inclination of the {0001} plane orientation (fifth plane orientation D5) of the second main surface 22 with respect to the {0001} plane orientation (second plane orientation D2) of the first main surface 11 is defined as a first inclination angle. The first inclination angle is the inclination of the fifth plane orientation D5 with respect to the second plane orientation D2 when viewed along the fourth direction 104.

[0067] The first tilt angle is, for example, 0.5° or less. The first tilt angle is not particularly limited, but may be, for example, 0.01° or more, or 0.05° or more. The first tilt angle is not particularly limited, but may be, for example, 0.4° or less, or 0.25° or less.

[0068] Similarly, with the second silicon carbide crystal 220, the third silicon carbide crystal 230, and the second flat plate 92 placed in the cutting apparatus 500, the inclination of the {0001} plane orientation (sixth plane orientation D6) of the sixth main surface 32 with respect to the {0001} plane orientation (third plane orientation D3) of the fourth main surface 21 is defined as a second inclination angle. The second inclination angle is the inclination of the sixth plane orientation D6 with respect to the third plane orientation D3 when viewed along the fourth direction 104.

[0069] The second tilt angle is, for example, 0.5° or less. The second tilt angle is not particularly limited, but may be, for example, 0.01° or more, or 0.05° or more. The second tilt angle is not particularly limited, but may be, for example, 0.4° or less, or 0.25° or less.

[0070] 9, in a state where the plurality of silicon carbide crystals 200 and the plurality of flat plates 90 are placed in cutting apparatus 500, the shortest distance between the plurality of silicon carbide crystals 200 and the plurality of wires 70 in cutting direction 109 is set to a first distance E1. In a state where the plurality of silicon carbide crystals 200 and the plurality of flat plates 90 are placed in cutting apparatus 500, the shortest distance between the plurality of flat plates 90 and the plurality of wires 70 in cutting direction 109 is set to a second distance E2.

[0071] The first distance E1 is, for example, equal to or less than the second distance E2. The value obtained by subtracting the first distance E1 from the second distance E2 is, for example, 1 mm or more and 10 mm or less. If the first distance E1 is longer than the second distance E2, when cutting the silicon carbide crystal 200, the wires 70 contact the flat plates 90 before contacting the silicon carbide crystals 200. In this case, due to the difference between the material of the silicon carbide crystals 200 and the material of the flat plates 90, the load applied to the wires 70 may increase when the wires 70 contact the silicon carbide crystals 200. If the first distance E1 is equal to or less than the second distance E2, the load applied to the wires 70 can be reduced.

[0072] Next, a step (S30) of adjusting the postures of the plurality of silicon carbide crystals is carried out. Specifically, the posture of fixing jig 60 is adjusted using, for example, a goniometer (not shown) or the like. This allows the postures of each of the plurality of silicon carbide crystals 200 to be adjusted simultaneously.

[0073] Next, a step (S40) of cutting the plurality of silicon carbide crystals is performed. Fig. 11 is a cross-sectional schematic diagram showing the step (S40) of cutting the plurality of silicon carbide crystals. As shown in Fig. 11, each of the plurality of silicon carbide crystals 200 is cut using the plurality of wires 70. Specifically, the plurality of wires 70 start to reciprocate, for example, along the fourth direction 104 (see Fig. 8). The linear speed of the plurality of wires 70 is set to 1000 m / min or more. The linear speed of the plurality of wires 70 may be 1200 m / min or more.

[0074] The wires 70 move along the cutting direction 109. The moving speed of the wires 70 in the cutting direction 109 is, for example, 0.05 mm / min on average. The wires 70 cut the silicon carbide crystals 200 and the flat plates 90. Specifically, in a state where the first flat plate 91 is disposed between the first silicon carbide crystal 210 and the second silicon carbide crystal 220 adjacent to each other among the silicon carbide crystals 200, the first silicon carbide crystal 210 and the second silicon carbide crystal 220 are simultaneously cut. Similarly, in a state where the second flat plate 92 is disposed between the second silicon carbide crystal 220 and the third silicon carbide crystal 230 adjacent to each other among the silicon carbide crystals 200, the second silicon carbide crystal 220 and the third silicon carbide crystal 230 are simultaneously cut. In this manner, silicon carbide substrate 100 (see FIGS. 1 and 2) in accordance with the present disclosure is manufactured.

[0075] (Method for manufacturing silicon carbide semiconductor device) Next, a method for manufacturing the silicon carbide semiconductor device 400 according to this embodiment will be described. Fig. 12 is a flow diagram that outlines the method for manufacturing the silicon carbide semiconductor device 400 according to this embodiment. As shown in Fig. 12, the method for manufacturing the silicon carbide semiconductor device 400 according to this embodiment mainly includes a step (S1) of manufacturing a silicon carbide epitaxial substrate and a step (S2) of forming an electrode on the silicon carbide epitaxial layer.

[0076] First, a step (S1) of manufacturing a silicon carbide epitaxial substrate is performed. The step (S1) of manufacturing a silicon carbide epitaxial substrate includes a step (S50) of preparing a silicon carbide substrate and a step (S60) of forming a silicon carbide epitaxial layer on the silicon carbide substrate. First, a step (S50) of preparing a silicon carbide substrate is performed. In the step (S50) of preparing a silicon carbide substrate, the silicon carbide substrate 100 is prepared using the method for manufacturing the silicon carbide substrate 100 described above (see FIG. 1).

[0077] Next, a step (S60) of forming a silicon carbide epitaxial layer on the silicon carbide substrate is performed. Specifically, silicon carbide epitaxial layer 40 is formed by epitaxial growth on seventh main surface 1 of silicon carbide substrate 100. In the epitaxial growth, for example, silane (SiH4) and propane (C3H8) are used as source gases, and hydrogen (H2) is used as a carrier gas. The temperature of the epitaxial growth is, for example, about 1400°C or higher and 1700°C or lower. In the epitaxial growth, an n-type impurity such as nitrogen is introduced into silicon carbide epitaxial layer 40. In this manner, silicon carbide epitaxial substrate 300 according to this embodiment is manufactured.

[0078] Fig. 13 is a cross-sectional schematic diagram showing a configuration of a silicon carbide epitaxial substrate 300 according to this embodiment. As shown in Fig. 13, the silicon carbide epitaxial substrate 300 has a silicon carbide substrate 100 and a silicon carbide epitaxial layer 40. The silicon carbide epitaxial layer 40 is provided on the silicon carbide substrate 100. The silicon carbide epitaxial layer 40 has a ninth main surface 3. The ninth main surface 3 constitutes the front surface of the silicon carbide epitaxial substrate 300. The eighth main surface 2 constitutes the back surface of the silicon carbide epitaxial substrate 300.

[0079] Silicon carbide epitaxial layer 40 may have a buffer layer 41 and a drift layer 42. Buffer layer 41 is in contact with silicon carbide substrate 100 at seventh main surface 1. Drift layer 42 is provided on buffer layer 41. Each of buffer layer 41 and drift layer 42 contains an n-type impurity such as nitrogen. The concentration of the n-type impurity contained in buffer layer 41 may be higher than the concentration of the n-type impurity contained in drift layer 42.

[0080] Next, a step (S2) of forming an electrode on the silicon carbide epitaxial layer is performed. Specifically, the following processing is performed on silicon carbide epitaxial substrate 300. First, ions are implanted into silicon carbide epitaxial substrate 300.

[0081] 14 is a schematic cross-sectional view showing a step of forming a body region. In the step of forming a body region, p-type impurities such as aluminum are ion-implanted into ninth main surface 3 of silicon carbide epitaxial layer 40. This forms body region 113 having p-type conductivity. Portions where body region 113 is not formed become drift layer 42 and buffer layer 41. Body region 113 has a thickness of, for example, 0.9 μm. Silicon carbide epitaxial layer 40 includes buffer layer 41, drift layer 42, and body region 113.

[0082] Next, a step of forming a source region is performed. Fig. 15 is a schematic cross-sectional view showing the step of forming a source region. Specifically, n-type impurities such as phosphorus are ion-implanted into the body region 113. This forms a source region 114 having an n-type conductivity. The thickness of the source region 114 is, for example, 0.4 µm. The concentration of the n-type impurity contained in the source region 114 is higher than the concentration of the p-type impurity contained in the body region 113.

[0083] Next, a p-type impurity such as aluminum is ion-implanted into the source region 114 to form a contact region 118. The contact region 118 is formed so as to penetrate the source region 114 and the body region 113 and to be in contact with the drift layer 42. The concentration of the p-type impurity contained in the contact region 118 is higher than the concentration of the n-type impurity contained in the source region 114.

[0084] Next, activation annealing is performed to activate the implanted impurities. The temperature of the activation annealing is, for example, 1500° C. to 1900° C. The activation annealing time is, for example, about 30 minutes. The atmosphere of the activation annealing is, for example, an argon atmosphere.

[0085] Next, a step of forming a trench in the ninth main surface 3 of the silicon carbide epitaxial layer 40 is performed. FIG. 16 is a cross-sectional schematic diagram showing a step of forming a trench in the ninth main surface 3 of the silicon carbide epitaxial layer 40. A mask 117 having an opening is formed on the ninth main surface 3 including the source region 114 and the contact region 118. The source region 114, the body region 113, and a part of the drift layer 42 are removed by etching using the mask 117. For example, inductively coupled plasma reactive ion etching can be used as the etching method. Specifically, for example, inductively coupled plasma reactive ion etching using SF6 or a mixed gas of SF6 and O2 as a reactive gas is used. A recess is formed in the ninth main surface 3 by etching.

[0086] Next, thermal etching is performed in the recess. The thermal etching can be performed, for example, by heating in an atmosphere containing a reactive gas having at least one or more types of halogen atoms, with the mask 117 formed on the ninth main surface 3. The at least one or more types of halogen atoms include at least one of chlorine (Cl) atoms and fluorine (F) atoms. The atmosphere includes, for example, Cl2, BCl3, SF6, or CF4. For example, a mixed gas of chlorine gas and oxygen gas is used as the reactive gas, and the thermal etching is performed at a heat treatment temperature of, for example, 700°C or more and 1000°C or less. Note that the reactive gas may contain a carrier gas in addition to the above-mentioned chlorine gas and oxygen gas. For example, nitrogen gas, argon gas, or helium gas can be used as the carrier gas.

[0087] 16 , a trench 56 is formed in the ninth main surface 3 by thermal etching. The trench 56 is defined by a sidewall surface 53 and a bottom wall surface 54. The sidewall surface 53 is formed by the source region 114, the body region 113, and the drift layer 42. The bottom wall surface 54 is formed by the drift layer 42. Next, the mask 117 is removed from the ninth main surface 3.

[0088] Next, a step of forming a gate insulating film is performed. Fig. 17 is a cross-sectional schematic diagram showing the step of forming a gate insulating film. Specifically, silicon carbide epitaxial substrate 300 having trench 56 formed in ninth main surface 3 is heated in an atmosphere containing oxygen at a temperature of, for example, 1300°C or more and 1400°C or less. As a result, gate insulating film 115 is formed, which is in contact with drift layer 42 at bottom wall surface 54, in contact with drift layer 42, body region 113, and source region 114 at side wall surface 53, and in contact with source region 114 and contact region 118 at ninth main surface 3.

[0089] Next, a step of forming a gate electrode is performed. Fig. 18 is a schematic cross-sectional view showing a step of forming a gate electrode and an interlayer insulating film. Gate electrode 127 is formed inside trench 56 so as to contact gate insulating film 115. Gate electrode 127 is disposed inside trench 56, and is formed on gate insulating film 115 so as to face each of sidewall surface 53 and bottom wall surface 54 of trench 56. Gate electrode 127 is formed, for example, by LPCVD (Low Pressure Chemical Vapor Deposition).

[0090] Next, the interlayer insulating film 126 is formed. The interlayer insulating film 126 is formed so as to cover the gate electrode 127 and to be in contact with the gate insulating film 115. The interlayer insulating film 126 is formed, for example, by chemical vapor deposition. The interlayer insulating film 126 is made of a material containing, for example, silicon dioxide. Next, the interlayer insulating film 126 and the gate insulating film 115 are partly etched so as to form openings on the source region 114 and the contact region 118. As a result, the contact region 118 and the source region 114 are exposed from the gate insulating film 115.

[0091] Next, a step of forming a source electrode is performed. The source electrode 116 is formed so as to contact each of the source region 114 and the contact region 118. The source electrode 116 is formed by, for example, a sputtering method. The source electrode 116 is made of, for example, a material including Ti (titanium), Al (aluminum) and Si (silicon).

[0092] Next, alloying annealing is performed. Specifically, the source electrode 116 in contact with each of the source region 114 and the contact region 118 is held at a temperature of, for example, 900° C. or more and 1100° C. or less for about 5 minutes. As a result, at least a portion of the source electrode 116 is silicided. As a result, the source electrode 116 in ohmic junction with the source region 114 is formed. The source electrode 116 may be in ohmic junction with the contact region 118.

[0093] Next, the source wiring 119 is formed. The source wiring 119 is electrically connected to the source electrode 116. The source wiring 119 is formed so as to cover the source electrode 116 and the interlayer insulating film 126.

[0094] Next, a step of forming a drain electrode is performed. First, the silicon carbide substrate 100 is polished at the eighth main surface 2. This reduces the thickness of the silicon carbide substrate 100. Next, the drain electrode 123 is formed. The drain electrode 123 is formed so as to be in contact with the eighth main surface 2. In this manner, the silicon carbide semiconductor device 400 according to this embodiment is manufactured.

[0095] 19 is a cross-sectional schematic diagram showing a configuration of a silicon carbide semiconductor device 400 according to this embodiment. The silicon carbide semiconductor device 400 is, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The silicon carbide semiconductor device 400 mainly includes a silicon carbide epitaxial substrate 300, a gate electrode 127, a gate insulating film 115, a source electrode 116, a drain electrode 123, a source wiring 119, and an interlayer insulating film 126. The silicon carbide epitaxial substrate 300 includes a buffer layer 41, a drift layer 42, a body region 113, a source region 114, and a contact region 118. The silicon carbide semiconductor device 400 may be, for example, an IGBT (Insulated Gate Bipolar Transistor) or the like.

[0096] Next, the effects of the method for manufacturing a silicon carbide substrate, the method for manufacturing a silicon carbide epitaxial substrate, and the method for manufacturing a silicon carbide semiconductor device according to the present embodiment will be described.

[0097] Typically, when manufacturing silicon carbide substrates 100 by simultaneously cutting a plurality of silicon carbide crystals 200, it is necessary to individually adjust the attitude of each of the plurality of silicon carbide crystals 200 in order to manufacture silicon carbide substrates 100 having the desired off-angle.

[0098] According to the method for manufacturing the silicon carbide substrate 100 of the present disclosure, in the step of cutting the plurality of silicon carbide crystals 200, the plurality of silicon carbide crystals 200 are simultaneously cut in a state in which the flat plate 90 is disposed between two adjacent silicon carbide crystals 200 among the plurality of silicon carbide crystals 200. Therefore, when adjusting the posture of each of the plurality of silicon carbide crystals 200, the posture of each of the two silicon carbide crystals 200 sandwiching the flat plate 90 can be adjusted integrally. This makes it possible to reduce the time required to adjust the posture of the plurality of silicon carbide crystals 200 while suppressing an increase in the relative inclination between the two adjacent silicon carbide crystals 200. As a result, the time required to cut the silicon carbide crystals can be reduced.

[0099] When the thickness variation of the flat plate 90 is excessively large, the relative inclination between the two silicon carbide crystals 200 sandwiching the flat plate 90 may become excessively large. According to the method for manufacturing the silicon carbide substrate 100 according to the present disclosure, the thickness variation of the flat plate 90 is 500 μm or less. Therefore, it is possible to suppress the relative inclination between the two silicon carbide crystals 200 sandwiching the flat plate 90 from becoming excessively large. From another viewpoint, it is possible to suppress the relative inclination between the {0001} planes of the two silicon carbide crystals 200 sandwiching the flat plate 90 from becoming excessively large. As a result, it is possible to reduce the difference between the {0001} plane orientation of the manufactured silicon carbide substrate 100 and the desired {0001} plane orientation of the silicon carbide substrate 100.

[0100] According to the method for manufacturing silicon carbide substrate 100 according to the present disclosure, first silicon carbide crystal 210, second silicon carbide crystal 220, and first flat plate 91 are placed in cutting apparatus 500 so that first surface 71 is in contact with first main surface 11 and second surface 72 is in contact with second main surface 22. The inclination of the {0001} plane orientation (fifth plane orientation D5) measured at second main surface 22 relative to the {0001} plane orientation (second plane orientation D2) measured at first main surface 11 is defined as a first inclination angle. The first inclination angle is, for example, 0.5° or less.

[0101] For this reason, when first silicon carbide crystal 210 and second silicon carbide crystal 220 are placed in cutting apparatus 500, the relative inclination between the {0001} planes of first silicon carbide crystal 210 and second silicon carbide crystal 220 is sufficiently reduced. As a result, the difference between the {0001} plane orientation of manufactured silicon carbide substrate 100 and the desired {0001} plane orientation of silicon carbide substrate 100 can be reduced.

[0102] When the thickness variation of the first silicon carbide crystal 210 is excessively large, the relative inclination between each of the plurality of silicon carbide crystals 200 may become excessively large. According to the method for manufacturing the silicon carbide substrate 100 according to the present disclosure, the thickness variation of the first silicon carbide crystal 210 is 500 μm or less. Therefore, it is possible to suppress the relative inclination between each of the plurality of silicon carbide crystals 200 from becoming excessively large. From another viewpoint, it is possible to suppress the relative inclination between each of the {0001} planes of the plurality of silicon carbide crystals 200 from becoming excessively large. As a result, it is possible to reduce the difference between the {0001} plane orientation of the manufactured silicon carbide substrate 100 and the desired {0001} plane orientation of the silicon carbide substrate 100.

[0103] According to the method for manufacturing silicon carbide substrate 100 according to the present disclosure, cutting apparatus 500 has holding member 50. Plural silicon carbide crystals 200 and flat plate 90 are held by holding member 50. Therefore, by adjusting the attitude of holding member 50, the attitude of each of plural silicon carbide crystals 200 can be adjusted simultaneously. This allows the attitude of each of plural silicon carbide crystals 200 to be easily adjusted.

[0104] In the above description, the number of silicon carbide crystals 200 in the plurality of silicon carbide crystals 200 is three, but the number of silicon carbide crystals 200 is not particularly limited. The number of silicon carbide crystals 200 may be two, or may be four or more. In the above description, the number of flat plates 90 in the plurality of flat plates 90 is two, but the number of flat plates 90 is not particularly limited. The number of flat plates 90 may be at least one or more. From another perspective, it is sufficient that the flat plate 90 is disposed between at least two silicon carbide crystals 200 among the plurality of silicon carbide crystals 200. The holding member 50 may be composed of a plurality of components. The plurality of components may be separate from each other.

[0105] Although a configuration has been described above in which all of the plurality of silicon carbide crystals 200 are cut simultaneously by one cutting, the method for manufacturing silicon carbide substrate 100 according to the present disclosure is not limited to the above configuration. It is sufficient that at least two of the plurality of silicon carbide crystals 200 are cut simultaneously by one cutting. In the step (S40) of cutting the plurality of silicon carbide crystals, flat plate 90 does not have to be cut. EXAMPLES

[0106] (Sample preparation) Silicon carbide substrate 100 was manufactured using the above-mentioned method for manufacturing silicon carbide substrate 100. In the step (S10) of preparing a plurality of silicon carbide crystals, three silicon carbide crystals 200 (first silicon carbide crystal 210, second silicon carbide crystal 220, and third silicon carbide crystal 230) were prepared.

[0107] The off angle (second angle θ2) of the first silicon carbide crystal 210 was 4.03°. The off angle (third angle θ3) of the second silicon carbide crystal 220 was 3.98°. The off angle (fourth angle θ4) of the third silicon carbide crystal 230 was 4.12°. In the step (S20) of placing a plurality of silicon carbide crystals in the cutting apparatus, a first flat plate 91 was placed between the first silicon carbide crystal 210 and the second silicon carbide crystal 220. A second flat plate 92 was placed between the second silicon carbide crystal 220 and the third silicon carbide crystal 230.

[0108] (Measurement method) The off-angles (first angle θ1) of the silicon carbide substrate 100 (sample 1) obtained by cutting the first silicon carbide crystal 210, the silicon carbide substrate 100 (sample 2) obtained by cutting the second silicon carbide crystal 220, and the silicon carbide substrate 100 (sample 3) obtained by cutting the third silicon carbide crystal 230 were measured. In measuring the off-angles, the above-mentioned method for measuring the plane orientation was used. The absolute values ​​of the differences between the off-angles of the respective samples 1 to 3 and the desired off-angles were calculated.

[0109] (Measurement results) The absolute value of the difference between the off-angle of Sample 1 and the desired off-angle was 0.2°. The absolute value of the difference between the off-angle of Sample 2 and the desired off-angle was 0.08°. The absolute value of the difference between the off-angle of Sample 3 and the desired off-angle was 0.3°.

[0110] From the above results, it was confirmed that silicon carbide substrate 100 according to the present disclosure can sufficiently reduce the absolute value of the difference between the off-angle of manufactured silicon carbide substrate 100 and a desired off-angle.

[0111] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments, and it is intended to include the equivalent meaning of the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0112] 1 7th main surface 2 8th main surface 3 9th main surface 7. First Orientation Flat 8 First circular arc 9 First outer periphery side 11 First main surface 12 Third main surface 15 1st central area 16 1st outer peripheral area 17 2nd Orientation Flat 18 Second circular arc 19 Second outer periphery side 21 Fourth main surface 22 Second main surface 25 Second central area 26 Second outer area 27 3rd Orientation Flat 28 Third circular arc 29 Third outer perimeter side 31 5th main surface 32 6th main surface 37 4th Orientation Flat 38 Fourth circular arc 39 4th outer perimeter side 40 Silicon carbide epitaxial layer 41 Buffer layer 42 Drift Layer 50 Retaining member 51 Holding surface 52 Mounting surface 53 Side wall 54 Bottom wall 56 Trench 60 Fixture 70 Wire 71 Page 1 72 2nd page 73 Page 3 74 Page 4 81 1st measurement point 82 Second measurement point 90 flat plate 91 1st plate 92 2nd plate 95 First virtual line 96 Second imaginary line 97 Third imaginary line 98 Fourth imaginary line 100 Silicon carbide substrate 101 1st direction 102 Second direction 103 Third direction 104 4th direction 109 Cutting direction 113 Body Region 114 Source Region 115 Gate insulating film 116 Source Electrode 117 Mask 118 Contact Area 119 Source wiring 123 Drain electrode 126 Interlayer insulating film 127 Gate electrode (electrode) 200 Silicon carbide crystal 210 First Silicon Carbide Crystal 220 Secondary silicon carbide crystal 230 Third Silicon Carbide Crystal 300 Silicon carbide epitaxial substrate 400 Silicon carbide semiconductor device 500 cutting equipment D1 1st plane direction D2 2nd plane direction D3 3rd surface orientation D4 4th plane direction D5 5th plane direction D6 6th plane direction E1 1st distance E2 2nd distance E3 3rd distance E4 4th distance H1 First thickness H2 Second thickness H3 3rd thickness H4 4th thickness H5 5th thickness H6 6th thickness N1 1st normal direction N2 2nd normal direction N3 3rd normal direction N4 4th normal direction O1 1st center O2 2nd center O3 3rd center O4 4th center O5 5th center W1 diameter θ1 1st angle θ2 2nd angle θ3 3rd angle θ4 4th angle

Claims

1. placing a plurality of silicon carbide crystals in a cutting apparatus; cutting the plurality of silicon carbide crystals using the cutting device; a cutting step of cutting the plurality of silicon carbide crystals, the plurality of silicon carbide crystals being simultaneously cut in a state in which a flat plate is placed between two adjacent silicon carbide crystals among the plurality of silicon carbide crystals.

2. The method for manufacturing a silicon carbide substrate according to claim 1 , wherein said flat plate has a thickness variation of 500 μm or less.

3. the plurality of silicon carbide crystals include a first silicon carbide crystal having a first main surface and a second silicon carbide crystal having a second main surface; the plate includes a first surface and a second surface opposite the first surface; in the step of placing the plurality of silicon carbide crystals in the cutting apparatus, the first silicon carbide crystal, the second silicon carbide crystal, and the flat plate are placed in the cutting apparatus such that the first surface is in contact with the first main surface and the second surface is in contact with the second main surface; 3 . The method for manufacturing a silicon carbide substrate according to claim 1 , wherein an inclination of a {0001} plane orientation of said second main surface with respect to a {0001} plane orientation of said first main surface is within 0.5°.

4. 4. The method for manufacturing a silicon carbide substrate according to claim 3, wherein the first silicon carbide crystal has a variation in thickness of not more than 500 μm.

5. The cutting device includes a holding member, The method for manufacturing a silicon carbide substrate according to claim 1 , wherein said plurality of silicon carbide crystals and said flat plate are held by said holding member.

6. A step of preparing a silicon carbide substrate by using the method for manufacturing a silicon carbide substrate according to claim 1 or 2; and forming a silicon carbide epitaxial layer on the silicon carbide substrate.

7. A step of preparing a silicon carbide substrate by using the method for manufacturing a silicon carbide substrate according to claim 1 or 2; forming a silicon carbide epitaxial layer on the silicon carbide substrate; and forming an electrode on the silicon carbide epitaxial layer.

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