SiC single crystal block, method for producing SiC single crystal block, and method for producing SiC substrate

Abstract

The purpose of the present invention is to provide: a SiC single-crystal ingot from which a large number of SiC substrates can be efficiently obtained; a method for producing a SiC single-crystal ingot; and a method for producing a SiC substrate. The SiC single crystal block according to the present embodiment includes, in a cut plane orthogonal to the crystal growth direction, a portion in which the length of a line segment that passes through the center of the largest inscribed circle enclosed by the cut plane and connects a first outer peripheral point and a second outer peripheral point of the cut plane is 211-221 mm.

Description

Technical Field

[0001] The present invention relates to a SiC single crystal ingot, a method for manufacturing a SiC single crystal ingot, and a method for manufacturing a SiC substrate. This application claims priority based on Japanese Patent Application No. 2023-141660 filed on August 31, 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, silicon carbide (SiC) is expected to be used in power devices, high-frequency devices, high-temperature working devices, etc. Therefore, in recent years, SiC epitaxial wafers have been used in semiconductor devices such as those mentioned 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 devices such as power devices, high-frequency devices, and high-temperature working devices are obtained by forming devices on 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 cylindrical single crystals, which are obtained by processing SiC single crystal blocks. In order to improve production efficiency, it is required to obtain many SiC substrates from one SiC single crystal block.

[0005] For example, Patent Document 1 discloses a method of manufacturing a large-diameter silicon single crystal ingot and dividing the silicon single crystal ingot to manufacture a large number of Si wafers at a time.

[0006] Prior art literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2002-75923 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] In SiC single crystal, Si and C elements are combined, which is more difficult to manufacture than Si single crystal formed by Si element alone. As described in Patent Document 1, the 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 block. When a large-diameter SiC single crystal block is to be manufactured, the stress generated in the SiC single crystal block will increase, and the SiC single crystal block will crack.

[0010] 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 single crystal ingot capable of efficiently obtaining a large number of SiC substrates.

[0011] Technical solutions to solve problems

[0012] The present inventors have discovered a method for producing a large-diameter SiC single crystal ingot and have determined the size of a SiC single crystal ingot suitable for obtaining a plurality of SiC substrates from the same surface.

[0013] (1) The SiC single crystal ingot involved in the first technical solution includes, in a cutting surface orthogonal to the crystal growth direction, a portion in which the length of a line segment passing through the center of the largest inscribed circle enclosed by the cutting surface and connecting the first peripheral point and the second peripheral point of the cutting surface is greater than 211 mm and less than 221 mm.

[0014] (2) In the SiC single crystal ingot involved in the above technical solution, the length of the line segment may be greater than or equal to 214 mm and less than or equal to 218 mm.

[0015] (3) The SiC single crystal block involved in the second technical solution includes, in a cutting surface orthogonal to the crystal growth direction, a portion having a length of greater than 236 mm and less than 248 mm, of a line segment passing through the center of the largest inscribed circle enclosed by the cutting surface and connecting the first peripheral point with the second peripheral point of the cutting surface.

[0016] (4) In the SiC single crystal ingot involved in the above technical solution, the length of the line segment can also be greater than 240 mm and less than 244 mm.

[0017] (5) The SiC single crystal block involved in the third technical solution includes, in a cutting surface orthogonal to the crystal growth direction, a portion having a length of greater than 319 mm and less than 329 mm, of a line segment passing through the center of the largest inscribed circle enclosed by the cutting surface and connecting the first peripheral point and the second peripheral point of the cutting surface.

[0018] (6) In the SiC single crystal ingot involved in the above technical solution, the length of the line segment can also be greater than 322 mm and less than 326 mm.

[0019] (7) The SiC single crystal block involved in the fourth technical solution includes, in a cutting surface orthogonal to the crystal growth direction, a portion having a length of 357 mm or more and 368 mm or less, of a line segment passing through the center of the largest inscribed circle enclosed by the cutting surface and connecting the first peripheral point with the second peripheral point of the cutting surface.

[0020] (8) In the SiC single crystal ingot involved in the above technical solution, the length of the line segment can also be greater than 361 mm and less than 365 mm.

[0021] (9) The method for manufacturing a SiC single crystal ingot involved in the fifth technical solution includes a crystal growth step of growing a SiC single crystal on the first surface of a seed crystal using a sublimation method. In the crystal growth step, the seed crystal is rotated while the second surface of the seed crystal opposite to the first surface is irradiated with a laser, so that the temperature of the irradiation position of the laser is controlled in such a way that the temperature relative to the radial center of the seed crystal is within ±5°C.

[0022] (10) The manufacturing method of the SiC substrate involved in the sixth technical solution includes: a process of forming an opening at the center of the SiC single crystal block involved in the above technical solution; a process of cutting the SiC single crystal block from the opening toward the radial outside to divide the SiC single crystal block into a plurality of parts; and a process of processing the plurality of parts into SiC ingots respectively and slicing the SiC ingots.

[0023] Effects of the Invention

[0024] The SiC single crystal ingot involved in the above technical solution can efficiently obtain many SiC substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a cross-sectional view of a SiC single crystal ingot according to the first embodiment.

[0026] Figure 2 This is a cross-sectional view obtained by cutting the SiC single crystal ingot according to the first embodiment along an XY plane orthogonal to the Z direction.

[0027] Figure 3 This is an XY cut plane of a first example when a plurality of SiC ingots are obtained from the SiC single crystal block according to the first embodiment.

[0028] Figure 4 This is an XY cut plane of a second example when a plurality of SiC ingots are obtained from the SiC single crystal block according to the first embodiment.

[0029] Figure 5 It is a diagram for explaining the method for producing a SiC single crystal ingot according to the first embodiment.

[0030] Figure 6 It is a diagram for explaining the method for manufacturing the SiC substrate according to the first embodiment.

[0031] Figure 7 It is a diagram for explaining the method for manufacturing the SiC substrate according to the first embodiment.

[0032] Figure 8It is a diagram for explaining the method for manufacturing the SiC substrate according to the first embodiment.

[0033] Fig. 9 It is a diagram for explaining the method for manufacturing the SiC substrate according to the first embodiment.

[0034] Description of symbols

[0035] 1 seed crystal; 1a first surface; 1b second surface; 2 crystal growth part; 10 SiC single crystal block; 20 SiC ingot; 30 SiC substrate; 50 crucible; 51 coil; 52 heating laser; 53 raw material powder; 54 drilling tool; 55 metal wire; H1, H2, H3, H4 openings DETAILED DESCRIPTION

[0036] Hereinafter, the SiC single crystal block and the SiC substrate involved in the present embodiment will be described in detail with appropriate reference to the accompanying drawings. In the accompanying drawings used in the following description, in order to facilitate understanding of the features of the present embodiment, the characteristic parts are sometimes enlarged, and the size ratios of the various components are sometimes different from the actual ones. The materials, dimensions, etc. illustrated in the following description are only examples, and the present invention is not limited thereto, and can be implemented by appropriately changing within the scope of not changing its purpose.

[0037] First, the directions are defined. The main direction of crystal growth of the SiC single crystal block is called the Z direction. The thickness direction of the seed crystal is an example of the Z direction. In addition, a radial direction of the SiC single crystal block is called the X direction. In addition, a radial direction of the SiC single crystal block and a direction orthogonal to the X direction is called the Y direction. The X direction and the Y direction are orthogonal to the Z direction.

[0038] Figure 1 1 is a cross-sectional view of a SiC single crystal ingot 10 according to the present embodiment. The SiC single crystal ingot 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 ingot 10. The crystal growth portion 2 is a SiC single crystal that is crystal-grown on the seed crystal 1.

[0039] The SiC single crystal block 10 can be a p-type semiconductor, an n-type semiconductor, or an intrinsic semiconductor. The SiC single crystal block 10 can also be semi-insulating. There is no particular limitation on the polymorph of the SiC single crystal block 10, and it can be any type of 4H, 6H, 3C, and 15R, or it can have multiple polymorphs. The offset angle of the SiC single crystal block 10 is, for example, greater than 0 degrees and less than 8 degrees. The conductivity type, polymorphism, and offset angle of the seed crystal 1 and the crystal growth portion 2 constituting the SiC single crystal block 10 are the same.

[0040] The thickness T of the SiC single crystal ingot 10 in the Z direction is b The thickness T of the SiC single crystal ingot 10 in the Z direction is 3 mm or more. b It is preferably 15 mm or more. b When the thickness is 15 mm or more, the dislocation near the facet can be swept out of the substrate acquisition region 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. The thickness T1 of the seed crystal 1 in the Z direction is, for example, 0.35 mm or less.

[0041] Figure 2 It is a cross-sectional view obtained by cutting the SiC single crystal block 10 involved in this embodiment with an XY plane orthogonal to the Z direction. The cut surface obtained by cutting the SiC single crystal block 10 with the XY plane is roughly circular. The cut surface obtained by cutting the SiC single crystal block 10 with the XY plane is almost not a perfect circle, and its diameter has a certain degree of deviation. For example, the line segments L1, L2, L3, and L4 passing through the center C of the cut surface are different. The line segment L1 connects the first peripheral point p1 and the second peripheral point p2 through the center C of the cut surface. The line segment L2 is located at a position where the line segment L1 is rotated 45 degrees with the center C as a reference, and connects the third peripheral point p3 and the fourth peripheral point p4 through the center C of the cut surface. The line segment L3 is located at a position where the line segment L1 is rotated 90 degrees with the center C as a reference, and connects the fifth peripheral point p5 and the sixth peripheral point p6 through the center C of the cut surface. Line segment L4 is located at a position where line segment L1 is rotated 135 degrees with respect to center C, and connects the seventh peripheral point p7 and the eighth peripheral point p8 through center C of the cut surface. The lengths of line segments L1, L2, L3, and L4 are within ±1.0% of the average of line segments L1, L2, L3, and L4.

[0042] Here, the "center of the cut surface" refers to the center of the cut surface when observed from a macroscopic perspective. When the cut surface is amorphous (irregular), the center of the largest inscribed circle contained in the cut surface is the "center of the cut surface". The shape of the cut surface can be obtained by measuring the outer diameter of the SiC single crystal block 10 at multiple locations using a vernier caliper. For example, the locations where the outer diameter is measured with a vernier caliper include the <1-100> direction and the <11-20> direction. In addition, the shape of the cut surface can also be obtained by using a three-dimensional measuring instrument to measure the overall shape of the single crystal ingot and using the result.

[0043] The length of the line segment L1 is, for example, greater than 211 mm and less than 221 mm, preferably greater than 214 mm and less than 218 mm. For the line segment L1, it can be set to any line segment passing through the center C, and the positions of the first peripheral point p1 and the second peripheral point p2 are arbitrary. That is, the line segment L1 being greater than 211 mm and less than 221 mm can be replaced by expressing that the cut surface of the SiC single crystal block 10 includes a portion of the line segment L1 having a length of greater than 211 mm and less than 221 mm. 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 greater than 221 mm. The lengths of the line segments L2, L3, and L4 are preferably greater than 211 mm. The lengths of the line segments L2, L3, and L4 are preferably less than 221 mm.

[0044] In addition, the length of line segment L1 may be greater than 236 mm and less than 248 mm, preferably greater than 240 mm and less than 244 mm. The cut surface of the SiC single crystal block 10 may include a portion of line segment L1 having a length of greater than 236 mm and less than 248 mm, preferably may include a portion of line segment L1 having a length of greater than 240 mm and less than 244 mm. In this case, the lengths of line segments L2, L3, and L4 may be different from those of line segment L1, and may be less than 236 mm or greater than 248 mm. The lengths of line segments L2, L3, and L4 are preferably greater than 236 mm. The lengths of line segments L2, L3, and L4 are preferably less than 248 mm.

[0045] In addition, the length of line segment L1 may be greater than 319 mm and less than 329 mm, preferably greater than 322 mm and less than 326 mm. The cut surface of the SiC single crystal block 10 may include a portion of line segment L1 having a length of greater than 319 mm and less than 329 mm, preferably may include a portion of line segment L1 having a length of greater than 322 mm and less than 326 mm. In this case, the lengths of line segments L2, L3, and L4 may be different from those of line segment L1, and may be less than 319 mm or greater than 329 mm. The lengths of line segments L2, L3, and L4 are preferably greater than 319 mm. The lengths of line segments L2, L3, and L4 are preferably less than 329 mm.

[0046] In addition, the length of line segment L1 may be greater than 357 mm and less than 368 mm, preferably greater than 361 mm and less than 365 mm. The cut surface of the SiC single crystal block 10 may include a portion of line segment L1 having a length of greater than 357 mm and less than 368 mm, preferably may include a portion of line segment L1 having a length of greater than 361 mm and less than 365 mm. In this case, the lengths of line segments L2, L3, and L4 may be different from those of line segment L1, and may be less than 357 mm or greater than 368 mm. The lengths of line segments L2, L3, and L4 are preferably greater than 357 mm. The lengths of line segments L2, L3, and L4 are preferably less than 368 mm.

[0047] The cut surface is, for example, any of the uppermost end, the lowermost end, the surface with the largest diameter, and the surface with the smallest diameter of SiC single crystal ingot 10. The direction of line segment L1 is preferably, for example, the <11-20> direction or the <1-100> direction.

[0048] When the SiC single crystal block 10 has a line segment L1 of a predetermined length, a plurality of SiC ingots can be efficiently obtained from one XY plane.

[0049] Figure 3 This is an XY cut plane of an example when a plurality of SiC ingots 20 are obtained from SiC single crystal block 10 . Figure 3 is the diameter D required for the SiC single crystal ingot 10 b The first example of a prescribed method for carrying out a prescribed operation. Figure 3 In the first example shown, when three SiC ingots 20 are obtained from a SiC single crystal block 10, the required diameter D of the SiC single crystal block 10 is specified. b In the first example, the required diameter D of the SiC single crystal ingot 10 is defined based on the following formula (1): b .

[0050]

[0051] In formula (1), D b is the required diameter of the SiC single crystal ingot 10, D w is the diameter of the SiC substrate, and l is the machining loss width. The machining loss width is a margin that takes into account the loss generated during the machining when the SiC ingot 20 is obtained from the SiC single crystal block 10. Regarding the machining loss width, it is 0.1 mm in the case of a small amount and about 0.6 mm in the case of a large amount. In addition, the SiC substrate is obtained by slicing the SiC ingot 20, so the diameter of the SiC substrate is roughly the same as the diameter of the SiC ingot 20.

[0052] For example, consider a case where three 4-inch SiC substrates are obtained from the same surface of the SiC single crystal ingot 10. The diameter D of the 4-inch substrate is w Sometimes there is some deviation. The diameter D of the 4-inch substrate w The allowable diameter D w It is not less than 98.0 mm and not more than 102.0 mm.

[0053] Table 1

[0054] <![CDATA[Substrate diameter D w (mm)]]> 98.0 100.2 102.0 Processing loss l(mm) 0.1 0.3 0.6 <![CDATA[Crystal block diameter D b (mm)]]> 211.28 216.25 220.47

[0055] Table 1 shows the change of diameter D wThe required diameter D of the SiC single crystal ingot 10 is obtained by calculating the size of the processing loss l. b When three 4-inch substrates are obtained from the same surface of the SiC single crystal ingot 10, the required diameter D of the SiC single crystal ingot 10 is b The diameter Db is preferably 211.28 mm to 220.47 mm. Therefore, when the SiC single crystal block 10 includes a portion where the length of the line segment L1 is 211 mm to 221 mm, three SiC ingots 20 can be obtained from one SiC single crystal block 10. In addition, when the diameter Db of the 4-inch substrate is w When the permissible range is 99.5 mm or more and 100.6 mm or less, the required diameter D of the SiC single crystal ingot 10 is b In this case, when SiC single crystal block 10 includes a portion where the length of line segment L1 is 214 mm to 218 mm, three SiC ingots 20 can be obtained from one SiC single crystal block 10 .

[0056] Similarly, consider the case where three 6-inch substrates are obtained from the same surface of the SiC single crystal ingot 10. The diameter Dw of the 6-inch substrate may vary slightly. w The allowable diameter Dw is not less than 148.0 mm and not more than 152.0 mm.

[0057] Table 2

[0058] <![CDATA[Substrate diameter D w (mm)]]> 148.0 150.2 152.0 Processing loss l(mm) 0.1 0.3 0.6 <![CDATA[Crystal block diameter D b (mm)]]> 319.01 323.98 328.21

[0059] Table 2 shows the change of diameter D w The required diameter D of the SiC single crystal ingot 10 is obtained by calculating the size of the processing loss l. b When three 6-inch substrates are obtained from the same surface of the SiC single crystal ingot 10, the required diameter D of the SiC single crystal ingot 10 is b 319 mm or more and 329 mm or less. Diameter D b Preferably, it is 319.01 mm or more and 328.21 mm or less. Therefore, when the SiC single crystal block 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 block 10. In addition, when the diameter D of the 6-inch substrate is w When the permissible range is 149.5 mm or more and 150.6 mm or less, the required diameter D of the SiC single crystal ingot 10 is bIn this case, when SiC single crystal block 10 includes a portion where the length of line segment L1 is 322 mm to 326 mm, three SiC ingots 20 can be obtained from one SiC single crystal block 10 .

[0060] Figure 4 This is an XY cut plane of an example when a plurality of SiC ingots 20 are obtained from SiC single crystal block 10 . Figure 4 The diameter D required for the SiC single crystal ingot 10 is b The second example of a method for carrying out a regulation. Figure 4 In the second example shown, the diameter D of the SiC single crystal ingot 10 is b The diameter D of the SiC single crystal ingot 10 is specified so that four SiC ingots 20 can be obtained from the SiC single crystal ingot 10. In the second example, the diameter D of the SiC single crystal ingot 10 is specified based on the following formula (2): b .

[0061]

[0062] In formula (2), D b is the required diameter of the SiC single crystal ingot 10, D w is the diameter of the SiC substrate, and 1 is the machining loss width. The machining loss width is 0.1 mm in the case of a small amount and about 0.6 mm in the case of a large amount. The diameter of the SiC substrate is substantially the same as the diameter of the SiC ingot 20 .

[0063] For example, consider a case where four 4-inch SiC substrates are obtained from the same surface of SiC single crystal ingot 10 .

[0064] Table 3

[0065] <![CDATA[Substrate diameter D w (mm)]]> 98.0 100.2 102.0 Processing loss l(mm) 0.1 0.3 0.6 <![CDATA[Crystal block diameter D b (mm)]]> 236.73 242.33 247.10

[0066] Table 3 shows the change of diameter D w The required diameter D of the SiC single crystal ingot 10 is obtained by calculating the size of the processing loss l. b When four 4-inch substrates are obtained from the same surface of the SiC single crystal ingot 10, the required diameter D of the SiC single crystal ingot 10 is b Therefore, when the SiC single crystal block 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 block 10. In addition, when the diameter D of the 4-inch substrate is w When the permissible range is 99.5 mm or more and 100.6 mm or less, the required diameter D of the SiC single crystal ingot 10 isb In this case, when SiC single crystal block 10 includes a portion where the length of line segment L1 is 240 mm to 244 mm, four SiC ingots 20 can be obtained from one SiC single crystal block 10 .

[0067] Similarly, a case where four 6-inch substrates are obtained from the same surface of SiC single crystal ingot 10 is considered.

[0068] Table 4

[0069] <![CDATA[Substrate diameter D w (mm)]]> 148.0 150.2 152.0 Processing loss I(mm) 0.1 0.3 0.6 <![CDATA[Crystal block diameter D b (mm)]]> 357.45 363.04 367.81

[0070] Table 4 shows the change in diameter D w The required diameter D of the SiC single crystal ingot 10 is obtained by calculating the size of the processing loss l. b When four 6-inch substrates are obtained from the same surface of the SiC single crystal ingot 10, the required diameter D of the SiC single crystal ingot 10 is b The diameter Db is preferably 357.45 mm to 367.81 mm. Therefore, when the SiC single crystal block 10 includes a portion where the length of the line segment L1 is 357 mm to 368 mm, four SiC ingots 20 can be obtained from one SiC single crystal block 10. In addition, when the diameter Db of the 6-inch substrate is w When the permissible range is 149.5 mm or more and 150.6 mm or less, the required diameter D of the SiC single crystal ingot 10 is b In this case, when SiC single crystal block 10 includes a portion where the length of line segment L1 is 361 mm to 365 mm, four SiC ingots 20 can be obtained from one SiC single crystal block 10 .

[0071] The SiC single crystal block 10 according to the present embodiment has a large diameter, and a plurality of SiC ingots 20 can be obtained. In addition, by defining the length of the line segment L1 passing through the center C of the SiC single crystal block 10, it is possible to reduce the loss when obtaining a plurality of SiC ingots 20. In addition, since a plurality of SiC substrates can be obtained from the SiC ingots 20, the SiC single crystal block 10 according to the present embodiment can efficiently obtain many SiC substrates.

[0072] Next, a method for producing SiC single crystal ingot 10 according to the present embodiment will be described. The method for producing SiC single crystal ingot 10 according to the present embodiment includes a crystal growth step of growing SiC single crystal on a first surface of a seed crystal using a sublimation method.

[0073] Figure 5 The device for manufacturing SiC single crystal ingot 10 includes crucible 50, coil 51, and heating laser 52. Crucible 50 is provided with openings H1 and H2 for temperature measurement and openings H3 and H4 for laser heating.

[0074] A raw material powder 53 is filled in the crucible 50. The raw material powder is made of SiC. The seed crystal 1 is set at a position opposite to the raw material powder 53 in the crucible 50. When an electric current flows through the coil 51 surrounding the crucible 50, the raw material powder 53 in the crucible 50 is heated. The gas sublimated from the raw material powder 53 is recrystallized on the first surface 1a of the seed crystal 1, and the crystal growth part 2 formed of the SiC single crystal grows on the first surface 1a.

[0075] In the crystal growth process, the second surface 1b of the seed crystal 1 is irradiated with laser. The second surface 1b is the surface opposite to the first surface 1a of the seed crystal 1 (i.e., the surface on the opposite side). The laser is irradiated from the heating laser 52 through the openings H3 and H4. The heating laser 52 is, for example, a CO2 laser with a wavelength of 10600nm. The heating laser 52 heats, for example, two positions symmetrically sandwiching the center of the seed crystal 1. The output of the heating laser 52 is, for example, several tens of W.

[0076] 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.

[0077] The heating laser 52 can change the irradiation position of the laser 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 part 2 can be controlled.

[0078] In the crystal growth process, the temperature of the laser irradiation position is controlled so that it is within ±5°C relative to the temperature of the radial center of the seed crystal 1. The temperature measurement can be performed using, for example, a high-end thermal imager FLIRA6000 series / X6000 series manufactured by Chino Co., Ltd. The temperature control is performed by, for example, adjusting the output and heating position of the heating laser 52 at any time.

[0079] 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 in the center. Therefore, in the early stage of crystal growth, a high-output laser is irradiated near the periphery of the seed crystal 1. By irradiating the laser, the periphery of the seed crystal 1 and the crystal growth part 2 is heated, so in the middle and final stages of crystal growth, the temperature difference between the periphery and the center of the seed crystal 1 becomes smaller. In this case, by reducing the output of the laser as the crystal growth progresses, the temperature distribution of the crystal growth surface of the crystal growth part 2 becomes smaller. In addition, at the same time, as the crystal growth progresses, the heating position of the laser is moved from the periphery toward the center. For example, the heating position of the laser is moved at 0.25 mm / h. For example, from the beginning of growth to the end of growth, the heating position of the laser is moved 35 mm toward the center of the seed crystal 1.

[0080] By manufacturing the SiC single crystal ingot 10 according to the above steps, it is possible to manufacture a large-diameter SiC single crystal ingot 10. It is believed that by controlling the temperature distribution of the crystal growth surface of the SiC single crystal ingot 10, the stress generated in the SiC single crystal ingot 10 can be reduced, and the SiC single crystal ingot will not crack even if it is large in diameter.

[0081] Next, a method for manufacturing a SiC substrate from the manufactured SiC single crystal ingot 10 will be described. The method for manufacturing a SiC substrate according to the present embodiment includes an opening forming step, a dividing step, an ingot processing step, and a slicing step. Figure 6 to Figure 9 It is a diagram for explaining the method for manufacturing the SiC substrate according to the first embodiment.

[0082] Figure 6 Schematic diagram of the opening forming process. In the opening forming process, an opening is formed in the center of the large-diameter SiC single crystal ingot 10 produced by the above steps. The opening is performed using, for example, a drill 54 made of boron nitride (BN) or diamond coating. The diameter of the opening is less than 7 mm, for example, 2 mm. The drill 54 is, for example, UDCMX manufactured by UNION TOOL.

[0083] Figure 7 Schematic diagram of the splitting process. In the splitting process, the SiC single crystal block 10 is cut from the opening toward the radially outer side, and the SiC single crystal block 10 is divided into a plurality of parts 11. In the splitting process, the metal wire 55 is passed through the opening to cut the SiC single crystal block 10 from the inside to the outside. By cutting the SiC single crystal block 10 from the inside to the outside, the generation of cracks can be suppressed compared to the case where the SiC single crystal block 10 is cut from the outside to the inside.

[0084] The splitting is preferably performed using a free abrasive cutter, for example. The free abrasive cutter can reduce the loss during cutting compared to the fixed abrasive cutter. The slurry can be a commercially available product. In addition, the diameter of the metal wire 55 is, for example, 0.15 mm. By reducing the diameter of the metal wire 55, the loss during cutting can be reduced.

[0085] Figure 8 2 is a schematic diagram of an ingot processing step. In the ingot processing step, each of the plurality of portions 11 cut in the dividing step is processed into a SiC ingot 20. The processing into the SiC ingot 20 can be performed using a cylindrical grinder.

[0086] Fig. 9 Schematic diagram of the slicing process. In the slicing process, each SiC ingot 20 is sliced. Slicing can be performed using a laser or a wire saw. A plurality of SiC substrates 30 are obtained from each SiC ingot 20. Both surfaces of the SiC substrate 30 may be polished.

[0087] In the method for manufacturing the SiC substrate according to the present embodiment, the SiC single crystal ingot 10 is divided from the inside to the outside. When the SiC single crystal ingot 10 is cut from the outside, the risk of cracks increases, but by dividing the SiC single crystal ingot 10 from the inside to the outside, the risk of cracks can be reduced.

[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.

Claims

1. A SiC single crystal block, A cut surface orthogonal to the crystal growth direction includes a portion where the length of a line segment passing through the center of the largest inscribed circle included in the cut surface and connecting the first peripheral point and the second peripheral point of the cut surface is greater than or equal to 211 mm and less than or equal to 221 mm.

2. The SiC single crystal ingot according to claim 1, The length of the line segment is greater than or equal to 214 mm and less than or equal to 218 mm.

3. A SiC single crystal block, A cut surface orthogonal to the crystal growth direction includes a portion having a length of 236 mm or more and 248 mm or less of a line segment passing through the center of the largest inscribed circle enclosed by the cut surface and connecting a first peripheral point and a second peripheral point of the cut surface.

4. The SiC single crystal ingot according to claim 3, The length of the line segment is greater than or equal to 240 mm and less than or equal to 244 mm.

5. A SiC single crystal block, A cut surface orthogonal to the crystal growth direction includes a portion having a length of 319 mm or more and 329 mm or less of a line segment passing through the center of the largest inscribed circle enclosed by the cut surface and connecting a first peripheral point and a second peripheral point of the cut surface.

6. The SiC single crystal ingot according to claim 5, The length of the line segment is greater than or equal to 322 mm and less than or equal to 326 mm.

7. A SiC single crystal block, A cut surface orthogonal to the crystal growth direction includes a portion having a length of 357 mm or more and 368 mm or less of a line segment passing through the center of the largest inscribed circle included in the cut surface and connecting a first peripheral point and a second peripheral point of the cut surface.

8. The SiC single crystal ingot according to claim 7, The length of the line segment is greater than or equal to 361 mm and less than or equal to 365 mm.

9. A method for manufacturing a SiC single crystal ingot, The method comprises a crystal growth 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, the second surface of the seed crystal opposite to the first surface is irradiated with laser light while the seed crystal is rotated. The temperature of the laser irradiation position is controlled so that the temperature of the radial center of the seed crystal is within ±5° C.

10. A method for manufacturing a SiC substrate, comprising: A step of forming an opening at the center of the SiC single crystal ingot according to any one of claims 1 to 8; The step of cutting the SiC single crystal ingot from the opening toward the outside in a radial direction to divide the SiC single crystal ingot into a plurality of parts; as well as The plurality of parts are processed into SiC ingots respectively, and the SiC ingots are sliced.

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