SiC SINGLE CRYSTAL BOULE, METHOD FOR MANUFACTURING SiC SINGLE CRYSTAL BOULE, AND METHOD FOR MANUFACTURING SiC SUBSTRATE

Abstract

To provide an SiC single crystal boule with which a lot of SiC substrates can be efficiently acquired.SOLUTION: A SiC single crystal boule includes a part at a cut surface orthogonal to a crystal growth direction, where a length of a line segment which passes through the center of the largest inscribed circle included in the cut surface and connects a first outer peripheral point and a second outer peripheral point of the cut surface is 211 mm or more and 221 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a SiC single crystal boule, a method for manufacturing a SiC single crystal boule, and a method for manufacturing a SiC substrate. [Background technology]

[0002] Silicon carbide (SiC) has an electric breakdown field one order of magnitude larger than silicon (Si) and a band gap three times larger. Silicon carbide (SiC) also has properties such as a thermal conductivity about three times higher than silicon (Si). For this reason, silicon carbide (SiC) is expected to be applied to power devices, high-frequency devices, high-temperature operating devices, and the like. For this reason, SiC epitaxial wafers have come to be used in the above-mentioned semiconductor devices in recent years.

[0003] SiC epitaxial wafers are obtained by stacking a SiC epitaxial layer on the surface of a SiC substrate. Hereinafter, the substrate before the SiC epitaxial layer is stacked is referred to as the SiC substrate, and the substrate after the SiC epitaxial layer is stacked is referred to as the SiC epitaxial wafer. SiC devices such as power devices, high frequency devices, and high temperature operating devices are obtained by forming devices in the SiC epitaxial layer of the SiC epitaxial wafer and then chipping the SiC epitaxial wafer.

[0004] SiC substrates are obtained by slicing SiC ingots. SiC ingots are single crystals processed into a cylindrical shape, and are obtained by processing SiC single crystal boules. To increase production efficiency, it is necessary to obtain many SiC substrates from one SiC single crystal boule.

[0005] For example, Patent Document 1 discloses a method for producing a large-diameter silicon single crystal ingot and dividing the silicon single crystal ingot to produce many Si wafers at once. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2002-75923 A Summary of the Invention [Problem to be solved by the invention]

[0007] Since the elements Si and C are bonded to a SiC single crystal, it is more difficult to manufacture it than a Si single crystal consisting of only the element Si. As described in Patent Document 1, a method of dividing a large-diameter single crystal in the radial direction is useful, but in the case of SiC, it is extremely difficult to manufacture a large-diameter SiC single crystal boule in the first place. When attempting to manufacture a large-diameter SiC single crystal boule, the stress generated in the SiC single crystal boule becomes large, and the SiC single crystal boule breaks.

[0008] The present invention has been made in consideration of the above problems, and has an object to provide a SiC single crystal boule from which a large number of SiC substrates can be efficiently obtained. [Means for solving the problem]

[0009] The present inventors discovered a method for producing a large-diameter SiC single crystal boule, and determined the size of the SiC single crystal boule suitable for obtaining multiple SiC substrates from the same plane.

[0010] (1) A SiC single crystal boule according to a first aspect includes a cut surface perpendicular to the crystal growth direction, the cut surface having a length of 211 mm or more and 221 mm or less, the length of a line segment passing through the center of the largest inscribed circle contained in the cut surface and connecting a first outer periphery point and a second outer periphery point of the cut surface.

[0011] (2) In the SiC single crystal boule according to the above aspect, the line segment may have a length of 214 mm or more and 218 mm or less.

[0012] (3) A SiC single crystal boule according to the second aspect includes a portion in a cut surface perpendicular to the crystal growth direction, where the length of a line segment passing through the center of the largest inscribed circle contained in the cut surface and connecting a first outer periphery point and a second outer periphery point of the cut surface is 236 mm or more and 248 mm or less.

[0013] (4) In the SiC single crystal boule according to the above aspect, the line segment may have a length of 240 mm or more and 244 mm or less.

[0014] (5) A SiC single crystal boule according to a third aspect includes a cut surface orthogonal to the crystal growth direction, the cut surface having a length of 319 mm or more and 329 mm or less, the length of a line segment passing through the center of the largest inscribed circle contained in the cut surface and connecting a first outer periphery point and a second outer periphery point of the cut surface.

[0015] (6) In the SiC single crystal boule according to the above aspect, the line segment may have a length of 322 mm or more and 326 mm or less.

[0016] (7) A SiC single crystal boule according to a fourth aspect includes a cut surface orthogonal to the crystal growth direction, the cut surface having a length of 357 mm or more and 368 mm or less, the length of a line segment passing through the center of the largest inscribed circle contained in the cut surface and connecting a first outer periphery point and a second outer periphery point of the cut surface.

[0017] (8) In the SiC single crystal boule according to the above aspect, the line segment may have a length of 361 mm or more and 365 mm or less.

[0018] (9) A fifth aspect of a method for producing a SiC single crystal boule includes a crystal growth step of growing a SiC single crystal on a first surface of a seed crystal by sublimation, and in the crystal growth step, a laser is irradiated onto a second surface of the seed crystal opposite to the first surface while rotating the seed crystal, and a temperature at the laser irradiation position is controlled to be within ±5°C of a temperature at a radial center of the seed crystal.

[0019] (10) A sixth aspect of the present invention relates to a method for manufacturing a SiC substrate, the method comprising the steps of: forming an opening at the center of a SiC single crystal boule according to the above aspect; cutting the SiC single crystal boule radially outward from the opening to divide the SiC single crystal boule into a plurality of parts; and processing each of the plurality of parts into a SiC ingot and slicing the SiC ingot. Effect of the Invention

[0020] The SiC single crystal boule according to the above embodiment makes it possible to efficiently obtain many SiC substrates. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a cross-sectional view of the SiC single crystal boule according to the first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the SiC single crystal boule according to the first embodiment, cut along an XY plane perpendicular to the Z direction. [Diagram 3] 1 is an XY cut surface of a first example of a case in which multiple SiC ingots are obtained from a SiC single crystal boule according to the first embodiment. [Figure 4] 13 is an XY cut surface of a second example of obtaining multiple SiC ingots from the SiC single crystal boule according to the first embodiment. [Diagram 5] FIG. 2 is a diagram for explaining the method for manufacturing a SiC single crystal boule according to the first embodiment. [Figure 6] 2A to 2C are views for explaining a method for manufacturing a SiC substrate according to the first embodiment. [Figure 7] 2A to 2C are views for explaining a method for manufacturing a SiC substrate according to the first embodiment. [Figure 8] 2A to 2C are views for explaining a method for manufacturing a SiC substrate according to the first embodiment. [Figure 9] 2A to 2C are views for explaining a method for manufacturing a SiC substrate according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The SiC single crystal boule and SiC substrate according to the present embodiment will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the characteristics of the present embodiment easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and may be modified as appropriate within the scope of the present invention.

[0023] First, the directions are defined. The main direction of crystal growth of the SiC single crystal boule is called the Z direction. The thickness direction of the seed crystal is an example of the Z direction. One radial direction of the SiC single crystal boule is called the X direction. One radial direction of the SiC single crystal boule that is perpendicular to the X direction is called the Y direction. The X and Y directions are perpendicular to the Z direction.

[0024] 1 is a cross-sectional view of a SiC single crystal boule 10 according to this embodiment. The SiC single crystal boule 10 includes a seed crystal 1 and a crystal growth portion 2. The seed crystal 1 is a SiC single crystal that serves as a starting point for crystal growth of the SiC single crystal boule 10. The crystal growth portion 2 is a SiC single crystal that has grown on the seed crystal 1.

[0025] The SiC single crystal boule 10 may be a p-type semiconductor, an n-type semiconductor, or an intrinsic semiconductor. The SiC single crystal boule 10 may be semi-insulating. The polytype of the SiC single crystal boule 10 is not particularly limited and may be any of 4H, 6H, 3C, and 15R, and may have a plurality of polytypes. The offset angle of the SiC single crystal boule 10 is, for example, 0 degrees or more and 8 degrees or less. The conductivity type, polytype, and offset angle of the seed crystal 1 and the crystal growth portion 2 constituting the SiC single crystal boule 10 are the same.

[0026] Thickness T of the SiC single crystal boule 10 in the Z direction b The thickness T of the SiC single crystal boule 10 in the Z direction is 3 mm or more. b The thickness T of the SiC single crystal boule 10 in the Z direction is preferably 15 mm or more. bWhen the offset angle is 15 mm or more, dislocations near the facet can be swept out of the substrate acquisition area when the offset angle is 4 degrees. The thickness T1 of the seed crystal 1 in the Z direction is, for example, 1 mm or less.

[0027] FIG. 2 is a cross-sectional view of the SiC single crystal boule 10 according to the present embodiment cut along the XY plane perpendicular to the Z direction. The cut surface of the SiC single crystal boule 10 cut along the XY plane is substantially circular. The cut surface of the SiC single crystal boule 10 cut along the XY plane is rarely a perfect circle, and its diameter has a certain degree of variation. For example, each of the line segments L1, L2, L3, and L4 passing through the center C of the cut surface is often different. The line segment L1 passes through the center C of the cut surface and connects the first outer periphery point p1 and the second outer periphery point p2. The line segment L2 is located at a position obtained by rotating the line segment L1 45 degrees with respect to the center C, passes through the center C of the cut surface, and connects the third outer periphery point p3 and the fourth outer periphery point p4. The line segment L3 is located at a position obtained by rotating the line segment L1 90 degrees with respect to the center C, passes through the center C of the cut surface, and connects the fifth outer periphery point p5 and the sixth outer periphery point p6. Line segment L4 is located at a position obtained by rotating line segment L1 135 degrees around center C, passes through center C of the cut surface, and connects the seventh outer perimeter point p7 and the eighth outer perimeter point p8. The lengths of line segments L1, L2, L3, and L4 are each within ±1.0% of the average of line segments L1, L2, L3, and L4.

[0028] Here, the "center of the cut surface" refers to the center of the cut surface when viewed from a macroscopic perspective. If the cut surface is irregular, the center of the largest inscribed circle contained within the cut surface is the "center of the cut surface." The shape of the cut surface can be determined by measuring the outer diameter of the SiC single crystal boule 10 at multiple points using a vernier caliper. For example, the points at which the outer diameter is measured with a vernier caliper include the <1-100> direction and the <11-20> direction. The shape of the cut surface can also be determined from the results of measuring the overall shape of the single crystal boule using a three-dimensional measuring device.

[0029] The length of the line segment L1 is, for example, 211 mm or more and 221 mm or less, and preferably 214 mm or more and 218 mm or less. The line segment L1 can be set to any line segment passing through the center C, and the positions of the first outer periphery point p1 and the second outer periphery point p2 are arbitrary. In other words, the line segment L1 being 211 mm or more and 221 mm or less can be said to mean that the cut surface of the SiC single crystal boule 10 includes a portion where the length of the line segment L1 is 211 mm or more and 221 mm or less. The lengths of the line segments L2, L3, and L4 may be different from the line segment L1, and may be less than 211 mm or more than 221 mm. The lengths of the line segments L2, L3, and L4 are preferably 211 mm or more.

[0030] The length of line segment L1 may be 236 mm or more and 248 mm or less, preferably 240 mm or more and 244 mm or less. The cut surface of SiC single crystal boule 10 may include a portion where line segment L1 has a length of 236 mm or more and 244 mm or less, preferably a portion where line segment L1 has a length of 240 mm or more and 244 mm or less. In this case, the lengths of line segments L2, L3, and L4 may be different from line segment L1, and may be less than 236 mm or more than 248 mm. The lengths of line segments L2, L3, and L4 are preferably 236 mm or more.

[0031] The length of line segment L1 may be 319 mm or more and 329 mm or less, preferably 322 mm or more and 326 mm or less. The cut surface of SiC single crystal boule 10 may include a portion where line segment L1 has a length of 319 mm or more and 329 mm or less, preferably a portion where line segment L1 has a length of 322 mm or more and 326 mm or less. In this case, the lengths of line segments L2, L3, and L4 may be different from line segment L1 and may be less than 319 mm or more than 329 mm. The lengths of line segments L2, L3, and L4 are preferably 319 mm or more.

[0032] The length of line segment L1 may be 357 mm or more and 368 mm or less, preferably 361 mm or more and 365 mm or less. The cut surface of SiC single crystal boule 10 may include a portion where line segment L1 has a length of 357 mm or more and 368 mm or less, preferably a portion where line segment L1 has a length of 361 mm or more and 365 mm or less. In this case, the lengths of line segments L2, L3, and L4 may be different from line segment L1, and may be less than 357 mm or more than 368 mm. The lengths of line segments L2, L3, and L4 are preferably 357 mm or more.

[0033] The cut surface is, for example, any one of the uppermost end, the lowermost end, the surface having the maximum diameter, and the surface having the minimum diameter of the SiC single crystal boule 10. The direction of the line segment L1 is preferably, for example, the <11-20> direction or the <1-100> direction.

[0034] When the SiC single crystal boule 10 has a line segment L1 of a predetermined length, multiple SiC ingots can be efficiently obtained from one XY plane.

[0035] FIG. 3 is an XY cut surface of an example of obtaining a plurality of SiC ingots 20 from a SiC single crystal boule 10. FIG. 3 shows a diameter D required for the SiC single crystal boule 10. b The first example shown in FIG. 3 is a method for determining the diameter D of the SiC single crystal boule 10 when three SiC ingots 20 are obtained from the SiC single crystal boule 10. b In the first example, the diameter D required for the SiC single crystal boule 10 is determined based on the following formula (1): b This section stipulates:

[0036]

number

[0037] In formula (1), D b is the desired diameter of the SiC single crystal boule 10, and D wis the diameter of the SiC substrate, and l is the processing loss width. The processing loss width is a margin that takes into consideration losses that occur during processing when obtaining the SiC ingot 20 from the SiC single crystal boule 10. The processing loss width is at least 0.1 mm and at most 0.6 mm. In addition, since the SiC substrate is obtained by slicing the SiC ingot 20, the diameter of the SiC substrate is approximately the same as the diameter of the SiC ingot 20.

[0038] For example, consider the case where three 4-inch SiC substrates are obtained from the same surface of the SiC single crystal boule 10. The diameter D w may vary slightly. Diameter D of a 4-inch board w Acceptable diameter D w is greater than or equal to 98.0 mm and less than or equal to 102.0 mm.

[0039] [Table 1]

[0040] Table 1 shows the diameter D w The diameter D required for the SiC single crystal boule 10 is calculated by changing the size of the processing loss l. b This is the result of obtaining the diameter D of the SiC single crystal boule 10 required to obtain three 4-inch substrates from the same surface of the SiC single crystal boule 10. b is 211 mm or more and 221 mm or less. Therefore, if the SiC single crystal boule 10 includes a portion where the length of the line segment L1 is 211 mm or more and 221 mm or less, three SiC ingots 20 can be obtained from one SiC single crystal boule 10. In addition, the diameter D w If the allowable range is 99.5 mm or more and 100.6 mm or less, the diameter D required for the SiC single crystal boule 10 is b is 214 mm or more and 218 mm or less. In this case, if SiC single crystal boule 10 includes a portion where line segment L1 has a length of 214 mm or more and 218 mm or less, three SiC ingots 20 can be obtained from one SiC single crystal boule 10.

[0041] Similarly, consider the case where three 6-inch substrates are obtained from the same surface of the SiC single crystal boule 10. The diameter D w may vary slightly. Diameter D of a 6-inch board w Acceptable diameter D w is greater than or equal to 148.0 mm and less than or equal to 152.0 mm.

[0042] [Table 2]

[0043] Table 2 shows the diameter D w The diameter D required for the SiC single crystal boule 10 is calculated by changing the size of the processing loss l. b This is the result of obtaining the diameter D of the SiC single crystal boule 10 required to obtain three 6-inch substrates from the same surface of the SiC single crystal boule 10. b is 319 mm or more and 329 mm or less. Therefore, if the SiC single crystal boule 10 includes a portion where the length of the line segment L1 is 319 mm or more and 329 mm or less, three SiC ingots 20 can be obtained from one SiC single crystal boule 10. In addition, the diameter D w If the allowable range is 149.5 mm or more and 150.6 mm or less, the required diameter D of the SiC single crystal boule 10 is b is 322 mm or more and 326 mm or less. In this case, if SiC single crystal boule 10 includes a portion where line segment L1 has a length of 322 mm or more and 326 mm or less, three SiC ingots 20 can be obtained from one SiC single crystal boule 10.

[0044] FIG. 4 is an XY cut surface of an example of obtaining a plurality of SiC ingots 20 from a SiC single crystal boule 10. FIG. 4 shows a diameter D b In the second example shown in FIG. 4, the diameter D of the SiC single crystal boule 10 is set to 1 / 10 so that four SiC ingots 20 can be obtained from the SiC single crystal boule 10. bIn the second example, the diameter D of the SiC single crystal boule 10 is determined based on the following formula (2): b This section stipulates:

[0045]

number

[0046] In formula (2), D b is the desired diameter of the SiC single crystal boule 10, and D w is the diameter of the SiC substrate, and l is the width of the processing loss. The width of the processing loss is about 0.1 mm at the smallest and about 0.6 mm at the largest. The diameter of the SiC substrate is approximately equal to the diameter of the SiC ingot 20.

[0047] For example, consider the case where four 4-inch SiC substrates are obtained from the same surface of the SiC single crystal boule 10.

[0048] [Table 3]

[0049] Table 3 shows the diameter D w The required diameter D of the SiC single crystal boule 10 is calculated by changing the size of the processing loss l. b This is the result of obtaining the diameter D of the SiC single crystal boule 10 required to obtain four 4-inch substrates from the same surface of the SiC single crystal boule 10. b is 236 mm or more and 248 mm or less. Therefore, if the SiC single crystal boule 10 includes a portion where the length of the line segment L1 is 236 mm or more and 248 mm or less, four SiC ingots 20 can be obtained from one SiC single crystal boule 10. In addition, the diameter D w If the allowable range is 99.5 mm or more and 100.6 mm or less, the required diameter D of the SiC single crystal boule 10 is bis 240 mm or more and 244 mm or less. In this case, if SiC single crystal boule 10 includes a portion where line segment L1 has a length of 240 mm or more and 244 mm or less, four SiC ingots 20 can be obtained from one SiC single crystal boule 10.

[0050] Similarly, a case will be considered in which four 6-inch substrates are obtained from the same surface of the SiC single crystal boule 10.

[0051] [Table 4]

[0052] Table 4 shows the diameter D w The required diameter D of the SiC single crystal boule 10 is calculated by changing the size of the processing loss l. b This is the result of obtaining the diameter D of the SiC single crystal boule 10 required to obtain four 6-inch substrates from the same surface of the SiC single crystal boule 10. b is 357 mm or more and 368 mm or less. Therefore, if the SiC single crystal boule 10 includes a portion where the length of the line segment L1 is 357 mm or more and 368 mm or less, four SiC ingots 20 can be obtained from one SiC single crystal boule 10. In addition, the diameter D w If the allowable range is 149.5 mm or more and 150.6 mm or less, the required diameter D of the SiC single crystal boule 10 is b is 361 mm or more and 365 mm or less. In this case, if SiC single crystal boule 10 includes a portion where line segment L1 has a length of 361 mm or more and 365 mm or less, four SiC ingots 20 can be obtained from one SiC single crystal boule 10.

[0053] The SiC single crystal boule 10 according to this embodiment has a large diameter and can obtain a plurality of SiC ingots 20. Furthermore, by specifying the length of the line segment L1 passing through the center C of the SiC single crystal boule 10, loss when obtaining a plurality of SiC ingots 20 can be reduced. Furthermore, since a plurality of SiC substrates can be obtained from each SiC ingot 20, the SiC single crystal boule 10 according to this embodiment can efficiently obtain a large number of SiC substrates.

[0054] Next, a description will be given of a method for manufacturing SiC single crystal boule 10 according to this embodiment. The method for manufacturing SiC single crystal boule 10 according to this embodiment includes a crystal growing step of growing a SiC single crystal on a first surface of a seed crystal by using a sublimation method.

[0055] 5 is a diagram for explaining a method for manufacturing a SiC single crystal boule 10 according to this embodiment. The apparatus for manufacturing a SiC single crystal boule 10 includes a crucible 50, a coil 51, and a heating laser 52. The crucible 50 is provided with openings H1 and H2 for temperature measurement and openings H3 and H4 for laser heating.

[0056] Raw material powder 53 is filled in crucible 50. The raw material powder is made of SiC. Seed crystal 1 is placed in a position facing raw material powder 53 in crucible 50. When a current is passed through coil 51 surrounding the periphery of crucible 50, raw material powder 53 in crucible 50 is heated. Gas sublimated from raw material powder 53 is recrystallized on first surface 1a of seed crystal 1, and crystal growth portion 2 made of SiC single crystal grows on first surface 1a.

[0057] In the crystal growth step, the second surface 1b of the seed crystal 1 is irradiated with a laser. The second surface 1b is a surface facing the first surface 1a of the seed crystal 1. The laser is irradiated from a heating laser 52 through openings H3 and H4. The heating laser 52 is, for example, a CO2 laser with a wavelength of 10600 nm. The heating laser 52 heats, for example, two locations that are symmetrical with respect to the center of the seed crystal 1. The output of the heating laser 52 is, for example, several tens of watts.

[0058] In the crystal growth step, the seed crystal 1 rotates together with the crucible 50. As the seed crystal 1 rotates, the heating laser 52 uniformly heats the seed crystal 1 in the circumferential direction. The rotation speed of the seed crystal 1 is, for example, 6 rpm.

[0059] The heating laser 52 can change the laser irradiation position in the radial direction of the seed crystal 1. The heating position of the seed crystal 1 by the laser can be changed in the radial direction. By changing the heating position of the seed crystal 1, the temperature distribution of the crystal growth surface of the crystal growth portion 2 can be controlled.

[0060] In the crystal growth process, the temperature at the laser irradiation position is controlled to be within ±5°C of the temperature at the center in the radial direction of the seed crystal 1. The temperature can be measured using, for example, a high-end research thermography FLIR A6000 series / X6000 series manufactured by Chino Corporation. This temperature control is performed, for example, by adjusting the output of the heating laser 52 and the heating position as needed.

[0061] For example, in the early stage of crystal growth, the temperature near the periphery of the seed crystal 1 is often lower than the temperature at the center. Therefore, in the early stage of crystal growth, a high-power laser is irradiated near the periphery of the seed crystal 1. Since the periphery of the seed crystal 1 and the crystal growth portion 2 are heated by the laser irradiation, the temperature difference between the periphery and the center of the seed crystal 1 becomes small in the middle and final stages of crystal growth. In this case, by weakening the laser output as the crystal growth progresses, the temperature distribution of the crystal growth surface of the crystal growth portion 2 becomes small. At the same time, the heating position by the laser is moved from the periphery to the center as the crystal growth progresses. For example, the laser heating position is moved at 0.25 mm / h. For example, the laser heating position is moved 35 mm toward the center of the seed crystal 1 from the early stage to the end of growth.

[0062] By producing the SiC single crystal boule 10 according to the above procedure, it is possible to produce a large-diameter SiC single crystal boule 10. It is believed that by controlling the temperature distribution on the crystal growth surface of the SiC single crystal boule 10, the stress generated in the SiC single crystal boule 10 can be reduced, and the SiC single crystal boule will not crack even if it has a large diameter.

[0063] Next, a method for producing a SiC substrate from the produced SiC single crystal boule 10 will be described. The method for producing a SiC substrate according to this embodiment includes an opening forming step, a dividing step, an ingot processing step, and a slicing step. Figures 6 to 9 are diagrams for explaining the method for producing a SiC substrate according to the first embodiment.

[0064] 6 is a schematic diagram of the aperture forming step. In the aperture forming step, an aperture is formed in the center of the large-diameter SiC single crystal boule 10 produced by the above-mentioned procedure. The aperture is formed, for example, by using a boron nitride (BN) or diamond-coated drill 54. The diameter of the aperture is 7 mm or less, for example, 2 mm. The drill 54 is, for example, a UDCMX manufactured by UNION TOOL.

[0065] 7 is a schematic diagram of the dividing step. In the dividing step, the SiC single crystal boule 10 is cut from the opening radially outward to divide the SiC single crystal boule 10 into a plurality of parts 11. In the dividing step, a wire 55 is passed through the opening to divide the SiC single crystal boule 10 from the inside to the outside. By cutting the SiC single crystal boule 10 from the inside to the outside, the occurrence of cracks can be suppressed more than when cutting the SiC single crystal boule 10 from the outside to the inside.

[0066] The division is preferably performed using, for example, a loose abrasive cutter. A loose abrasive cutter can reduce loss during cutting compared to a fixed abrasive cutter. A commercially available slurry can be used. The diameter of the wire 55 is, for example, 0.15 mm. By reducing the diameter of the wire 55, loss during cutting can be reduced.

[0067] 8 is a schematic diagram of the ingot processing step. In the ingot processing step, each of the multiple parts 11 cut in the dividing step is processed into a SiC ingot 20. The processing into the SiC ingot 20 can be performed by a cylindrical grinding machine.

[0068] 9 is a schematic diagram of the slicing step. In the slicing step, each SiC ingot 20 is sliced. The slicing may be performed using a laser or a wire saw or the like. A plurality of SiC substrates 30 are obtained from each SiC ingot 20. Both sides of each SiC substrate 30 may be polished.

[0069] In the method for producing a SiC substrate according to the present embodiment, the SiC single crystal boule 10 is divided from the inside to the outside. Cutting the SiC single crystal boule 10 from the outside increases the risk of cracks, but dividing the SiC single crystal boule 10 from the inside to the outside reduces the risk of cracks.

[0070] Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0071] Reference Signs List 1... seed crystal, 1a... first surface, 1b... second surface, 2... crystal growth portion, 10... SiC single crystal boule, 20... SiC ingot, 30... SiC substrate, 50... crucible, 51... coil, 52... heating laser, 53... raw material powder, 54... drill, 55... wire, H1, H2, H3, H4... openings

Claims

1. 1. A SiC single crystal boule comprising: a cut surface perpendicular to a crystal growth direction, the cut surface including a line segment passing through a center of a maximum inscribed circle contained in the cut surface and connecting a first outer periphery point and a second outer periphery point of the cut surface, the line segment having a length of 211 mm or more and 221 mm or less.

2. 2. The SiC single crystal boule of claim 1, wherein the line segment has a length of 214 mm or more and 218 mm or less.

3. 1. A SiC single crystal boule comprising: a cut surface perpendicular to a crystal growth direction, the cut surface including a line segment passing through a center of a maximum inscribed circle contained in the cut surface and connecting a first outer periphery point and a second outer periphery point of the cut surface, the line segment having a length of 236 mm or more and 248 mm or less.

4. 4. The SiC single crystal boule of claim 3, wherein the line segment has a length of 240 mm or more and 244 mm or less.

5. 1. A SiC single crystal boule comprising: a cut surface perpendicular to a crystal growth direction, the cut surface including a portion having a length of 319 mm or more and 329 mm or less, the length of a line segment passing through a center of a maximum inscribed circle contained in the cut surface and connecting a first outer periphery point and a second outer periphery point of the cut surface.

6. 6. The SiC single crystal boule of claim 5, wherein the line segment has a length of 322 mm or more and 326 mm or less.

7. 1. A SiC single crystal boule comprising: a cut surface perpendicular to a crystal growth direction, the cut surface including a portion having a length of 357 mm or more and 368 mm or less, the length of a line segment passing through a center of a maximum inscribed circle contained in the cut surface and connecting a first outer periphery point and a second outer periphery point of the cut surface.

8. 8. The SiC single crystal boule of claim 7, wherein the line segment has a length of 361 mm or more and 365 mm or less.

9. a crystal growing step of growing a SiC single crystal on a first surface of a seed crystal by using a sublimation method; In the crystal growth step, a laser is irradiated onto a second surface of the seed crystal opposite to the first surface while rotating the seed crystal; A method for manufacturing a SiC single crystal boule, comprising controlling a temperature at the laser irradiation position to be within ±5°C of a temperature at the radial center of the seed crystal.

10. forming an opening in the center of the SiC single crystal boule of any one of claims 1 to 8; cutting the SiC single crystal boule radially outward from the opening to divide the SiC single crystal boule into a plurality of parts; processing each of the plurality of parts into a SiC ingot, and slicing the SiC ingot.

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