SiC substrate and SiC epitaxial wafer

Abstract

The purpose of the present invention is to provide a large-diameter SiC substrate and a SiC epitaxial wafer having few microtube defects. The SiC substrate according to the present embodiment has a diameter of 195 mm or more and a microtube density of 0.01 / cm2 or less.

Description

Technical Field

[0001] The present invention relates to a SiC substrate and a SiC epitaxial wafer. This application claims priority based on Japanese Patent Application No. 2023-136613 filed on August 24, 2023, the contents of which are incorporated herein by reference. Background Art

[0002] Compared with silicon (Si), the insulation breakdown electric field of silicon carbide (SiC) is one order of magnitude larger and the band gap is three times larger. In addition, silicon carbide (SiC) has characteristics such as thermal conductivity being about three times higher than that of silicon (Si). Therefore, it is expected that silicon carbide (SiC) will be applied to power devices, high-frequency devices, high-temperature working devices, etc. Therefore, in recent years, SiC epitaxial wafers are used for semiconductor devices such as the above.

[0003] SiC epitaxial wafers are obtained by stacking SiC epitaxial layers on the surface of SiC substrates. Hereinafter, the substrate before stacking the SiC epitaxial layer is referred to as SiC substrate, and the substrate after stacking the SiC epitaxial layer is referred to as SiC epitaxial wafer. SiC substrates are made by cutting out SiC ingots. SiC devices such as power devices, high-frequency devices, and high-temperature working devices are obtained by chipping SiC epitaxial wafers after the SiC epitaxial layer of the SiC epitaxial wafer forms the device.

[0004] In order to increase the number of SiC devices that can be obtained from a SiC epitaxial wafer, it is required to enlarge the diameter of the SiC substrate and the SiC epitaxial wafer. However, it is not easy to enlarge the diameter of the SiC substrate and the SiC epitaxial wafer. For example, Non-Patent Document 1 records that when the diameter of the SiC substrate and the SiC epitaxial wafer increases, the number of defects will increase significantly.

[0005] In addition, as one of the defects contained in the SiC substrate, there is a micropipe (for example, Patent Document 1). Micropipes are one of the fatal defects that have a bad influence on the subsequent processes and SiC devices. Micropipes, for example, can cause poor withstand voltage of SiC devices. Micropipes are crystal defects that are hollow inside, have a diameter of about sub-μm to several μm, and propagate in the c-axis direction of hexagonal silicon carbide. Micropipes are believed to be formed by the relaxation of strain energy by screw dislocations with large Burgers vectors.

[0006] Prior art literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-127201

[0008] Non-patent document 1: N. Piluso, E. Carria, R. Anzalone, A Severino. Microelectronic Engineering 273 (2023) 111962. Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] As also described in Patent Document 1, micropipes are defects that are difficult to completely eliminate. In addition, this tendency becomes more pronounced when the diameter of the SiC substrate becomes larger.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a SiC substrate and a SiC epitaxial wafer having a large diameter and few micropipes.

[0012] Technical solutions to solve problems

[0013] The present inventors have produced a SiC substrate and a SiC epitaxial wafer having few micropipes even when the substrate has a large diameter.

[0014] (1) The diameter of the SiC substrate according to the first invention is 195 mm or more, and the micropipe density is 0.01 micropipes / cm 2 the following.

[0015] (2) In the SiC substrate according to the above-mentioned aspect, the number of micropipes in the effective area excluding the edge exclusion area within 3 mm from the outer circumference may be 3 or less.

[0016] (3) In the SiC substrate according to the above-mentioned aspect, the number of micropipes in the effective area excluding the edge exclusion area within 3 mm from the outer circumference may be one or less.

[0017] (4) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​4 mm 2 Among the plurality of first regions obtained by dividing the surface into squares, more than 7209 first regions have no microtubules.

[0018] (5) The SiC substrate involved in the above technical solution can also be a substrate with an area of ​​9 mm 2 Among the plurality of second regions obtained by dividing the surface into squares, more than 3168 second regions have no microtubules.

[0019] (6) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​16 mm 2 Among the plurality of third regions obtained by dividing the surface into squares, more than 1,764 third regions have no microtubules.

[0020] (7) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​25 mm 2 Among the plurality of fourth regions obtained by dividing the surface into squares, more than 1116 fourth regions have no microtubules.

[0021] (8) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​36 mm 2 Among the plurality of fifth regions obtained by dividing the surface into squares, more than 764 fifth regions have no microtubules.

[0022] (9) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​49 mm 2 Among the plurality of sixth regions obtained by dividing the surface into squares, more than 556 sixth regions have no microtubules.

[0023] (10) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​64 mm 2 Among the plurality of seventh regions obtained by dividing the surface into squares, more than 421 seventh regions have no microtubules.

[0024] (11) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​81 mm 2 Among the plurality of eighth regions obtained by dividing the surface into squares, more than 329 eighth regions had no microtubules.

[0025] (12) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​100 mm 2 Among the plurality of 9th regions obtained by dividing the surface into squares, more than 262 9th regions have no microtubules.

[0026] (13) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​225 mm 2 Among the plurality of 10th regions obtained by dividing the surface into squares, more than 112 10th regions have no microtubules.

[0027] (14) The SiC substrate involved in the above technical solution may also be a substrate with an area of ​​400 mm 2 Among the plurality of 11th regions obtained by dividing the surface into squares, more than 58 11th regions have no microtubules.

[0028] (15) The SiC substrate according to the above technical solution may have a diameter of 205 mm or less.

[0029] (16) A SiC epitaxial wafer according to a second aspect includes the SiC substrate according to the above aspect and a SiC epitaxial layer stacked on the SiC substrate.

[0030] Effects of the Invention

[0031] The SiC substrate and SiC epitaxial wafer involved in the above technical solution have large diameters and few micropipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a top view of the SiC substrate according to the present embodiment.

[0033] Figure 2 This is an enlarged view of the vicinity of the center of the SiC substrate according to the present embodiment.

[0034] Figure 3 It is a diagram for explaining the method for manufacturing a SiC substrate according to the present embodiment.

[0035] Figure 4 It is a cross-sectional view of a SiC epitaxial wafer according to the present embodiment.

[0036] Description of symbols

[0037] 1 effective area, 2 edge exclusion area, 3 positioning groove (notch), 10 SiC substrate, A area, C center, 11 seed crystal, 12 crucible, 12A inner wall surface, 14 adhesive, 15 raw material, 20 SiC epitaxial layer, 100 SiC epitaxial wafer DETAILED DESCRIPTION

[0038] Hereinafter, the SiC substrate and SiC epitaxial wafer, etc. involved in the present embodiment will be described in detail with appropriate reference to the accompanying drawings. In order to make the features of the present embodiment easier to understand, the accompanying drawings used in the following description may enlarge the characteristic parts for convenience, and the size ratios of the various components may be different from the actual ones. The materials, dimensions, etc. illustrated in the following description are examples, and the present invention is not limited to those materials, dimensions, etc., and can be implemented by appropriately changing them within the scope of not changing the purpose.

[0039] In this specification, individual orientations are indicated by [], and collective orientations are indicated by <>. Regarding negative indices, "-" (bar) is written above the numbers in crystallography, but in this specification, a minus sign is written before the numbers.

[0040] Figure 1 It is a top view of the SiC substrate 10 according to the present embodiment. Figure 1This is a view of the SiC substrate observed from the <0001> direction. The SiC substrate 10 is formed of, for example, n-type SiC. The polytype of the SiC substrate 10 is not particularly limited, and may be any of 2H, 3C, 4H, and 6H. The SiC substrate 10 is, for example, 4H-SiC.

[0041] The SiC substrate 10 has a substantially circular shape when viewed from above. The SiC substrate 10 may have a positioning groove 3 for determining the direction of the crystal axis. Alternatively, the SiC substrate 10 may have an orientation flat surface instead of the positioning groove 3 .

[0042] The diameter of the SiC substrate 10 is, for example, 195 mm or more, preferably 199 mm or more. In addition, the diameter of the SiC substrate 10 is preferably 205 mm or less, more preferably 201 mm or less. The diameter of the SiC substrate 10 is, for example, 195 mm or more and 205 mm or less, preferably 199 mm or more and 201 mm or less.

[0043] The SiC substrate 10 has an effective area 1 and an edge exclusion area 2. The effective area 1 is an area used to obtain a device, and is an area of ​​the SiC substrate 10 excluding the edge exclusion area 2. The edge exclusion area 2 is an area within 3 mm from the outer periphery. The edge exclusion area 2 is an area that is generally not used for device production.

[0044] The micropipe density of the SiC substrate 10 according to the present embodiment is 0.01 micropipes / cm 2 The number of micropipes in the SiC substrate 10 according to the present embodiment is 3 or less, preferably 1 or less, and more preferably 0. The number of micropipes in the effective region 1 is, for example, 3 or less, preferably 1 or less, and more preferably 0.

[0045] Micropipes are hollow defects that are exposed on the surface of the SiC substrate 10 and have a diameter greater than 1 μm. Micropipes can be confirmed using a transmission X-ray topography image. Micropipes have strong strain and have a strong point-shaped contrast. Therefore, in a transmission X-ray topography image, micropipes can be distinguished by using the difference in contrast from other defects. For example, when micropipes are confirmed using a transmission X-ray topography image, the contrast of a point-shaped defect caused by deformation of a micropipe has a contrast that is more than three times that of a point-shaped defect caused by a threading dislocation.

[0046] In addition, in addition to the transmission X-ray topography image, microtubes can also be evaluated using an optical microscope and photoluminescence. Microtubes are confirmed as concave and convex in an optical microscope. In addition, microtubes are confirmed as dark spots accompanied by bright spots in photoluminescence. By observing microtubes using multiple evaluation methods, the accuracy of microtube identification can be further improved.

[0047] After distinguishing micropipes from other defects according to the above steps, the micropipe density and the number of micropipes in the SiC substrate 10 can be obtained by counting the number of micropipes. The position coordinates of the micropipes can be calculated from the position coordinates of the entire surface photograph of the transmission X-ray topography image. In addition, the density of the micropipes can be calculated by dividing the number of micropipes by the area of ​​the substrate.

[0048] The SiC substrate 10 is cut into a plurality of chips when obtaining a device. For example, the SiC substrate 10 is divided into a plurality of regions according to the size of the chip. Figure 2 This is a diagram obtained by enlarging the vicinity of the center C of the SiC substrate 10 involved in this embodiment. For example, the surface of the SiC substrate 10 is divided into a plurality of regions A. The regions A are each formed by a square with a side length of a. The regions A cover the entire surface of the SiC substrate 10 without any gaps. The center of one of the plurality of regions A coincides with the center C of the SiC substrate 10. Each region A corresponds to a singulated chip and becomes a SiC device.

[0049] The size of region A varies depending on the size required for the device. The area of ​​region A varies depending on the length a of one side.

[0050] Let the length a be 2 mm and the area be 4 mm 2 The square area is called the first area.

[0051] Let the length a be 3 mm and the area be 9 mm 2 The square area is called the second area.

[0052] Let the length a be 4 mm and the area be 16 mm 2 The square area is called the third area.

[0053] Let the length a be 5 mm and the area be 25 mm 2 The area of ​​the square is called the 4th area.

[0054] Let the length a be 6 mm and the area be 36 mm 2 The area of ​​the square is called the fifth area.

[0055] Let length a be 7 mm and area be 49 mm 2 The area of ​​the square is called the 6th area.

[0056] Let the length a be 8 mm and the area be 64 mm 2 The area of ​​the square is called the 7th area.

[0057] Let length a be 9 mm and area be 81 mm 2 The area of ​​the square is called the 8th area.

[0058] Let the length a be 10 mm and the area be 100 mm 2 The area of ​​the square is called the 9th area.

[0059] Let length a be 15 mm and area be 225 mm 2 The area of ​​the square is called the 10th area.

[0060] Let the length a be 20 mm and the area be 400 mm 2 The area of ​​the square is called the 11th area.

[0061] An example of region A is shown here, but the size of the region is not limited to this. For example, the length of one side may be 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, or 19 mm, and the length of one side is not limited to an integer.

[0062] When region A is the first region, preferably, there are no micropipes in 7209 or more of the plurality of first regions included in the SiC substrate 10. If the number of first regions belonging to the effective region 1 is 7209 and none of these regions have micropipes, the maximum number of SiC devices can be obtained from one SiC substrate 10.

[0063] When the region A is the second region, preferably, there are no micropipes in 3168 or more of the plurality of second regions included in the SiC substrate 10. The number of second regions belonging to the effective region 1 is 3168.

[0064] When the region A is the third region, preferably, there are no micropipes in 1764 or more third regions among the plurality of third regions included in the SiC substrate 10. The number of third regions belonging to the effective region 1 is 1764.

[0065] When the region A is the fourth region, preferably, there are no micropipes in 1116 or more fourth regions among the plurality of fourth regions included in the SiC substrate 10. The number of fourth regions belonging to the effective region 1 is 1116.

[0066] When region A is the fifth region, preferably, there are no micropipes in 764 or more fifth regions among the plurality of fifth regions included in the SiC substrate 10. The number of fifth regions belonging to the effective region 1 is 764.

[0067] When the region A is the sixth region, preferably, there are no micropipes in 556 or more sixth regions among the plurality of sixth regions included in the SiC substrate 10. The number of sixth regions belonging to the effective region 1 is 556.

[0068] When the region A is the seventh region, preferably, there are no micropipes in 421 or more seventh regions among the plurality of seventh regions included in the SiC substrate 10. The number of seventh regions belonging to the effective region 1 is 421.

[0069] When region A is the eighth region, preferably, there are no micropipes in 329 or more eighth regions among the plurality of eighth regions included in the SiC substrate 10. The number of eighth regions belonging to the effective region 1 is 329.

[0070] When region A is the ninth region, preferably, there are no micropipes in 262 or more ninth regions among the plurality of ninth regions included in the SiC substrate 10. The number of ninth regions belonging to the effective region 1 is 262.

[0071] When the region A is the tenth region, preferably, there are no micropipes in 112 or more tenth regions among the plurality of tenth regions included in the SiC substrate 10. The number of tenth regions belonging to the effective region 1 is 112.

[0072] When the region A is the eleventh region, preferably, there are no micropipes in 58 or more of the plurality of eleventh regions included in the SiC substrate 10. The number of eleventh regions belonging to the effective region 1 is fifty-eight.

[0073] Next, a method for manufacturing the SiC substrate 10 according to the present embodiment will be described. Figure 3 This is a diagram for explaining the method for manufacturing the SiC substrate 10 according to the present embodiment. The method for manufacturing the SiC substrate 10 includes a seed crystal preparation step, a crucible preparation step, a seed crystal setting step, a raw material setting step, a crystal growth step, and a slicing step.

[0074] First, in the seed crystal preparation step, a seed crystal 11 is prepared. A crystal that does not include micropipes is prepared for the seed crystal 11. The seed crystal 11 that does not include micropipes can be produced by, for example, using the RAF (Repeated a-face) method.

[0075] Next, in the crucible preparation step, a crucible 12 for crystal growth is prepared. The crucible 12 is formed of graphite and a portion of its inner wall surface 12A is covered with a coating 13. The coating 13 is formed of TaC. The coating 13 covers an area of ​​10% or more and 50% or less of the inner wall surface 12A of the crucible 12. Here, the inner wall surface 12A means a surface of the inner surface of the crucible that is not filled with the raw material 15 and is exposed in the growth space.

[0076] When the coverage area of ​​the coating 13 is too small, carbon generated by dust from the inner wall surface 12A of the crucible 12 is easily introduced into the growing crystal. The carbon inclusion introduced into the crystal becomes the cause of the generation of microtubes. In addition, when the coverage area of ​​the coating 13 is too large, the supply of carbon gas from the inner wall surface 12A of the crucible 12 becomes less, and heterogeneous polymorphic SiC is easily generated in the growing crystal. Heterogeneous polymorphic SiC also becomes the cause of the generation of microtubes. The predetermined area of ​​the inner wall surface 12A of the crucible 12 is covered by the coating 13, which becomes a reason for preventing the generation of microtubes in the SiC substrate 10.

[0077] In addition, the coating 13 is provided at a position close to the seed crystal in the inner wall surface 12A. For example, when the crucible 12 has a guide member 16, a portion of the guide member 16 is covered by the coating 13. Specifically, the portion of the surface of the guide member 16 from a position 5 mm away from the first end 16a of the guide member 16 to a position 100 mm away from the first end 16a is covered by the coating 13. Here, the first end 16a is the end of the guide member 16 on the seed crystal 11 side. By partially covering the guide member 16 with the coating 13, it is possible to suppress dust generation while suppressing the generation of heterogeneous polymorphs. The generation state of micropipes in the SiC substrate 10 also changes depending on the setting position of the coating 13.

[0078] Next, in the seed crystal setting step, seed crystal 11 is set in crucible 12. Seed crystal 11 may be set on inner wall surface 12A of crucible 12 or on a susceptor provided on inner wall surface 12A. The susceptor is formed of the same member as crucible 12, for example.

[0079] The seed crystal 11 is set in the crucible 12, for example, by means of an adhesive 14. At this time, the seed crystal 11 is set in the crucible 12 in such a way that the shortest distance D between the back surface of the seed crystal 11 and the setting surface of the seed crystal 11 is less than 30 μm at any position in the in-plane direction of the seed crystal 11. For the setting surface, when the seed crystal 11 is directly set on the crucible 12, the setting surface is the inner wall surface 12A of the crucible 12, and when the seed crystal 11 is set on the susceptor, the setting surface is the exposed surface of the susceptor. The in-plane of the seed crystal 11 is the in-plane in which the seed crystal 11 extends, and is consistent with the direction in which the surface orthogonal to the straight line connecting the seed crystal 11 and the raw material 15 at the shortest distance extends. The shortest distance D between the back surface of the seed crystal 11 and the setting surface of the seed crystal 11 does not change significantly before and after heating during crystal growth, and therefore, it can be measured before heating or after heating. In addition, the adhesive 14 will carbonize when heated. Sometimes a gap is generated between the surface of the carbonized adhesive 14 and the seed crystal 11. The thickness of the gap (the shortest distance between the surface of the carbonized adhesive 14 and the seed crystal 11) is set to 10 μm or less.

[0080] When the distance between the seed crystal 11 and the setting surface increases, the seed crystal 11 is relatively located near the raw material 15. The closer to the raw material 15, the higher the temperature. In a high temperature environment, the seed crystal 11 is easily etched. When the seed crystal 11 is etched, the adhesive 14 or the setting surface is exposed. SiC polycrystals are easily grown in the exposed portion of the adhesive 14 or the setting surface. In the SiC polycrystalline state, micropipes are easily generated. By properly controlling the distance between the seed crystal 11 and the setting surface, the generation of micropipes in the SiC substrate 10 can be suppressed. In addition, the gap between the surface of the carbonized adhesive 14 and the seed crystal 11 will disturb the in-plane temperature uniformity during crystal growth, which becomes a cause of temperature rise. In the part where the temperature locally becomes high, etching will be accelerated, and the adhesive 14 or the setting surface will be exposed. Therefore, by preventing the gap between the surface of the adhesive 14 and the seed crystal 11, or by sufficiently narrowing the gap between the surface of the adhesive 14 and the seed crystal 11, the generation of micropipes in the SiC substrate 10 can be further suppressed.

[0081] Next, in the raw material setting step, raw material 15 is set at the bottom of crucible 12. Raw material 15 is, for example, SiC powder. In the raw material setting step, raw material 15 is set so that the shortest distance between the outermost surface of raw material 15 and seed crystal 11 is 150 mm or more. By making the distance between the raw material and the seed crystal far away, the risk of the seed crystal becoming high temperature and being etched can be reduced.

[0082] Next, a crystal growth step is performed by a sublimation method. In the sublimation method, a sublimation gas obtained by sublimating a raw material 15 in the crucible 12 by heating the crucible 12 is supplied to the seed crystal 11 to grow the seed crystal 11 into a larger SiC ingot. The SiC ingot grows on the seed crystal 11.

[0083] In the crystal growth process, the SiC ingot is grown to more than 10 mm. The diameter expansion of the SiC ingot relative to the seed crystal 11 is set to be greater than 5 mm and less than 10 mm. The diameter expansion is a value obtained by subtracting the diameter of the seed crystal 11 from the maximum diameter of the SiC ingot. For the diameter expansion of the SiC ingot, a predetermined diameter expansion can be obtained by adjusting the shape of the guide component 16 that expands the sublimation gas flow. By adjusting the growth amount of the SiC ingot according to the shape of the guide component 16, the diameter expansion is made greater than 5 mm and less than 10 mm. For a diameter expansion of less than 5 mm, in order to obtain a large-diameter crystal, it is necessary to repeatedly expand the diameter multiple times, and it is difficult to produce a large-diameter crystal.

[0084] On the other hand, when the diameter of the crystal is excessively enlarged during crystal growth, stress is generated in the crystal. When the diameter expansion amount during crystal growth is too large, stress concentration sometimes occurs, and cracks are generated in the crystal. The cracks become the cause of micropipe defects. In the crystal growth process, by controlling the diameter expansion of the crystal to be less than 10 mm, the generation of micropipes in the SiC substrate 10 can be suppressed.

[0085] Next, in the slicing step, the SiC substrate 10 is cut out from the SiC ingot. For example, the SiC ingot is hollowed out into a cylinder with a predetermined diameter, and the cylinder is sliced ​​to produce the SiC substrate 10. The slicing may be performed using a laser or a wire saw.

[0086] As described above, by performing the seed crystal preparation step, crucible preparation step, seed crystal setting step, raw material setting step, crystal growth step, and slicing step while performing control, it is possible to manufacture SiC substrate 10 having few micropipes even if it is large in diameter.

[0087] The SiC substrate 10 according to the present embodiment has few micropipes despite its large diameter. Therefore, many good SiC devices can be obtained from the SiC substrate 10 according to the present embodiment. The SiC device is obtained by chipping the SiC epitaxial wafer for each region A. Figure 4 1 is a cross-sectional view of a SiC epitaxial wafer 100 according to the present embodiment. The SiC epitaxial wafer 100 includes a SiC substrate 10 and a SiC epitaxial layer 20. Devices are formed in the SiC epitaxial layer 20.

[0088] As mentioned above, although the preferred embodiment of the present invention has been described in detail, the present invention is not limited to the specific embodiment, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

[0089] [Example]

[0090] "Example 1"

[0091] First, a seed crystal was prepared. A 4H-SiC single crystal having a diameter of 197 mm was prepared as a seed crystal.

[0092] Next, a crucible was prepared. A crucible whose inner wall surface was 39% covered with TaC was used. The coating formed by TaC was formed on a portion of the inner surface of the guide member near the seed crystal of the crucible. Specifically, the guide member was covered with TaC from a position 5 mm away from the first end of the seed crystal side to a position 100 mm away from the first end.

[0093] Next, a seed crystal was set on the inner wall surface of the crucible. The seed crystal was set on the inner wall surface using an adhesive. The adhesive used was a carbon adhesive with a thickness of 20 μm. Since the adhesive did not peel off, the distance between the back of the seed crystal and the setting surface of the seed crystal after the seed crystal was set was maintained at 20 μm, and no gap was formed between the carbonized adhesive and the seed crystal.

[0094] Next, the lower surface of the crucible was filled with a raw material. SiC powder was used as the raw material. The distance between the outermost surface of the raw material and the surface of the seed crystal was set to 200 mm.

[0095] Next, a SiC ingot was grown on the seed crystal using a sublimation method. The crystal growth amount (thickness of the SiC ingot) was 25 mm. In addition, the diameter expansion amount of the SiC ingot relative to the seed crystal was 8 mm.

[0096] Next, after slicing the produced SiC ingot, the (0001) surface of the cut substrate was polished in the order of grinding, mechanical polishing (MP), and chemical mechanical polishing (CMP) to obtain a SiC substrate. The surface of the SiC substrate was measured using a transmission X-ray topography image to determine the number of micropipes contained in the SiC substrate.

[0097] The number of micropipes included in the SiC substrate of Example 1 is 1. Although one micropipe exists in the effective area, it is located near the edge exclusion area. Therefore, the micropipe can be excluded from the device acquisition area to partition the device acquisition area.

[0098] Therefore, according to the size of the region, it is possible to obtain a region without micropipes from the SiC substrate of Example 1. The number of the regions corresponds to the number of devices obtained.

[0099] Region 1: 7,209

[0100] Region 2: 3,168

[0101] Region 3: 1,764

[0102] Region 4: 1,116

[0103] Region 5: 764

[0104] Region 6: 556

[0105] Region 7: 421

[0106] Region 8: 329

[0107] Region 9: 262

[0108] Region 10: 112

[0109] Region 11: 58

[0110] As described above, in Example 1, a SiC substrate with few micropipes was obtained even for a large-diameter substrate of 8 inches. For Example 1, reproducibility was obtained even in multiple experiments. In addition, for the seed crystal of Example 1, a crystal with few micropipes obtained by multiple diameter expansions in the same manner as in Example 1 was used.

Claims

1. A SiC substrate, The diameter is 195mm or more. The microtubule density is 0.01 / cm 2 the following.

2. The SiC substrate according to claim 1, The number of microtubes in the effective area excluding the edge exclusion area within 3 mm from the outer periphery is 3 or less.

3. The SiC substrate according to claim 1, The number of microtubes in the effective area excluding the edge exclusion area within 3 mm from the outer periphery is 1 or less.

4. The SiC substrate according to claim 1, With an area of ​​4mm 2 Among the plurality of first regions obtained by dividing the surface into squares, more than 7209 first regions have no microtubules.

5. The SiC substrate according to claim 1, With an area of ​​9mm 2 Among the plurality of second regions obtained by dividing the surface into squares, more than 3168 second regions have no microtubules.

6. The SiC substrate according to claim 1, With an area of ​​16mm 2 Among the plurality of third regions obtained by dividing the surface into squares, more than 1764 third regions have no microtubules.

7. The SiC substrate according to claim 1, With an area of ​​25mm 2 Among the plurality of fourth regions obtained by dividing the surface into squares, more than 1116 fourth regions have no microtubules.

8. The SiC substrate according to claim 1, With an area of ​​36mm 2 Among the plurality of fifth regions obtained by dividing the surface into squares, more than 764 fifth regions have no microtubules.

9. The SiC substrate according to claim 1, With an area of ​​49mm 2 Among the plurality of sixth regions obtained by dividing the surface into squares, more than 556 sixth regions have no microtubules.

10. The SiC substrate according to claim 1, With an area of ​​64mm 2 Among the plurality of seventh regions obtained by dividing the surface into squares, more than 421 seventh regions have no microtubules.

11. The SiC substrate according to claim 1, With an area of ​​81mm 2 Among the plurality of eighth regions obtained by dividing the surface into squares, more than 329 eighth regions had no microtubules.

12. The SiC substrate according to claim 1, With an area of ​​100mm 2 Among the plurality of 9th regions obtained by dividing the surface into squares, more than 262 9th regions have no microtubules.

13. The SiC substrate according to claim 1, With an area of ​​225mm 2 Among the plurality of 10th regions obtained by dividing the surface into squares, more than 112 10th regions have no microtubules.

14. The SiC substrate according to claim 1, With an area of ​​400mm 2 Among the plurality of 11th regions obtained by dividing the surface into squares, more than 58 11th regions have no microtubules.

15. The SiC substrate according to claim 1, The diameter is less than 205mm. 16 . A SiC epitaxial wafer comprising the SiC substrate according to claim 1 and a SiC epitaxial layer stacked on the SiC substrate.

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