SiC crystal ingot and method for manufacturing SiC substrate

Abstract

This SiC crystal ingot has a facet, and when D is the diameter and Lx is the length of the first side of an imaginary rectangle that surrounds the facet with the minimum area in plan view from the crystal growth direction and has the first side parallel to the < 11-20 > direction and the second side parallel to the < 1-100 > direction, Lx is the length of the second side parallel to the < 1-100 > direction, D is the diameter of the imaginary rectangle, and Lx is the length of the second side parallel to the < 11-20 > direction. Lx / D < 0.3 is satisfied at a first end, which is a terminal end in the crystal growth direction.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a SiC ingot and a SiC substrate.

[0002] This application claims priority based on Japanese Patent Application No. 2023-223189 filed on December 28, 2023, Japanese Patent Application No. 2023-223451 filed on December 28, 2023, Japanese Patent Application No. 2023-223461 filed on December 28, 2023, Japanese Patent Application No. 2024-188125 filed on October 25, 2024, Japanese Patent Application No. 2024-188186 filed on October 25, 2024, and Japanese Patent Application No. 2024-188277 filed on October 25, 2024, the contents of which are incorporated herein by reference. Background Art

[0003] Silicon carbide (SiC) has an insulation breakdown electric field that is one order of magnitude larger and a bandgap that is three times larger than that of silicon (Si). In addition, silicon carbide (SiC) has characteristics such as a thermal conductivity that is about three times higher than that of silicon (Si). Therefore, silicon carbide (SiC) is expected to be applied to power devices, high-frequency devices, high-temperature operating devices, etc. Therefore, in recent years, SiC epitaxial wafers have been used in the semiconductor devices as described above.

[0004] A SiC epitaxial wafer is obtained by laminating a SiC epitaxial layer on the surface of a SiC substrate. Hereinafter, the substrate before laminating the SiC epitaxial layer is referred to as a SiC substrate, and the substrate after laminating the SiC epitaxial layer is referred to as a SiC epitaxial wafer. The SiC substrate is cut from a SiC ingot.

[0005] For example, as described in Patent Document 1, when manufacturing a SiC ingot, a facet is formed on the SiC ingot. When crystal growth is performed on the SiC ingot, a part of the crystal growth surface is parallel to the c-plane, and a plane parallel to the c-plane is exposed on the crystal growth surface. The crystal growth mode of this plane parallel to the c-plane is different from that of the other crystal growth surfaces with step flow growth. The part where crystal growth is performed in a manner different from the part with step flow growth is the facet.

[0006] Prior Art Documents

[0007] Patent Document 1: Japanese Patent No. 6050053 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] In recent years, SiC ingots have been processed using lasers. For example, cracks are formed on the SiC ingot using a laser, and a SiC substrate is cut out from the SiC ingot. The optimal value of the laser output varies depending on the resistance value of the SiC single crystal. If the laser output is small, sufficient cracks will not be generated. If the laser output is large, the roughness of the processed surface may increase. The resistance value of the facet is lower than that of the part where step flow growth occurs.

[0010] If there is a facet in the SiC ingot, it is necessary to change the laser output. There is a problem that the processing productivity decreases as the number of times of changing the laser output increases.

[0011] The present invention has been completed in view of the above problems, and an object thereof is to provide an SiC ingot that is easily processed during laser processing, and a method for manufacturing an SiC substrate using the SiC ingot.

[0012] Means for Solving the Problem

[0013] The present inventors found that in order to reduce the opportunity of changing the laser output, the shape of the facet is controlled. In order to solve the above problems, the present invention provides the following technical means.

[0014] (1) The SiC ingot of the first aspect has a facet. In this SiC ingot, when the diameter of the SiC ingot is set to D, and the length of the first side of a hypothetical rectangle that encloses the facet with the smallest area when viewed from the crystal growth direction and has a first side parallel to the <11-20> direction and a second side parallel to the <1-100> direction is set to Lx, at the first end that is the terminal of the crystal growth direction, Lx / D < 0.3 is satisfied.

[0015] (2) The SiC ingot according to the technical solution of (1) above may satisfy 0.05 < Lx / D < 0.3 at the first end.

[0016] (3) The SiC ingot according to the technical solution of (1) or (2) above may satisfy Lx / D ≤ 0.2 at the first end.

[0017] (4) The SiC ingot according to any one of the technical solutions of (1) to (3) above may satisfy Lx / D ≤ 0.1 at the first end.

[0018] (5) The SiC ingot according to any one of the technical solutions of (1) to (4) above may satisfy Lx / D < 0.3 at the second end opposite to the first end.

[0019] (6) The SiC ingot according to any one of the technical solutions of (1) to (5) above may satisfy 0.05 < Lx / D < 0.3 at the second end.

[0020] (7) The SiC ingot according to any one of the above (1) to (6) can satisfy Lx / D < 0.3 in one cut surface that intersects within a range of 90° ± 1° with the crystal growth direction.

[0021] (8) The SiC ingot according to any one of the above (1) to (7) can satisfy Lx / D < 0.3 in two or more cut surfaces that intersect within a range of 90° ± 1° with the crystal growth direction.

[0022] (9) The SiC ingot according to any one of the above (1) to (8) can satisfy Lx / D < 0.3 in five or more cut surfaces that intersect within a range of 90° ± 1° with the crystal growth direction.

[0023] (10) The SiC ingot according to any one of the above (1) to (9) can satisfy Lx / D < 0.3 in any one cut surface that intersects within a range of 90° ± 1° with the crystal growth direction.

[0024] (11) The SiC ingot according to any one of the above (1) to (10) can have a portion with an offset angle with respect to the {0001} plane of 3.5° or more and 4.5° or less.

[0025] (12) For the SiC ingot according to any one of the above (1) to (11), the height of the crystal growth direction can be 20 mm or more.

[0026] (13) For the SiC ingot according to any one of the above (1) to (12), the diameter can be 145 mm or more.

[0027] (14) For the SiC ingot according to any one of the above (1) to (12), the diameter can be 195 mm or more.

[0028] (15) For the SiC ingot according to any one of the above (1) to (14), when the length of the second side of the imaginary rectangle is set as Ly, at the first end, 0.5 > Ly / D can be satisfied.

[0029] (16) For the SiC ingot according to any one of the above (1) to (15), when the length of the second side of the imaginary rectangle is set as Ly, in any one cut surface that intersects within a range of 90° ± 1° with the crystal growth direction, 0.5 > Ly / D can be satisfied.

[0030] (17) The manufacturing method of the SiC substrate according to the second aspect includes: a step of manufacturing the SiC ingot according to any one of the above (1) to (16); and a step of slicing the SiC ingot.

[0031] (18) The manufacturing method of the SiC substrate according to the third aspect includes: a step of preparing the SiC ingot according to any one of the above (1) to (16); and a step of slicing the SiC ingot.

[0032] Effects of the Invention

[0033] The SiC ingot according to the above aspect is easy to process during laser processing. In addition, the production efficiency of the manufacturing method of the SiC substrate according to the above aspect is excellent. Description of the Drawings

[0034] Figure 1 It is a perspective view of the SiC ingot according to the present embodiment.

[0035] Figure 2 It is a cross-sectional view of the SiC ingot according to the present embodiment.

[0036] Figure 3 It is a top view of the cut surface obtained by cutting the SiC ingot according to the present embodiment.

[0037] Figure 4 It is a top view of the cut surface obtained by cutting the SiC ingot according to the comparative example.

[0038] Figure 5 It is a top view of the cut surface obtained by cutting the SiC ingot according to the comparative example.

[0039] Figure 6 It is a cross-sectional view of an example of the manufacturing apparatus for manufacturing the SiC ingot according to the present embodiment.

[0040] Figure 7 It is a cross-sectional view of another example of the manufacturing apparatus for manufacturing the SiC ingot according to the present embodiment.

[0041] Description of Reference Numerals

[0042] 1 First end

[0043] 2 Second end

[0044] 3 Side surface

[0045] 4 Facet

[0046] 5 Step flow growth region

[0047] 6 Oriented plane

[0048] 7 Imaginary rectangle

[0049] 8 First side

[0050] 9 Second side

[0051] 10 SiC ingot

[0052] 20 Crucible

[0053] 21 Storage part

[0054] 22 Lid

[0055] 23 Gas discharge path

[0056] 24 Support

[0057] 25 Hanging part

[0058] 30 Thermal insulation material

[0059] 40 Inner lined quartz tube

[0060] 41 Support

[0061] 50 Quartz tube

[0062] 51 Upper lid

[0063] 52 Lower lid

[0064] 60 Reflectance measuring device

[0065] 70 Weight measuring device

[0066] 71 Evaluation substrate Detailed implementation mode

[0067] Hereinafter, the SiC ingot and the like of the present embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in order to easily understand the features of the present embodiment, sometimes the part that becomes a feature is enlarged and shown, and the dimensional ratios of the respective components are sometimes different from the actual ones. The materials, dimensions, etc. exemplified in the following description are only examples, and the present invention is not limited thereto, and can be appropriately changed and implemented within the range without changing its gist (technical requirements).

[0068] In this specification, individual orientations are represented by [], collective orientations are represented by <>, individual planes are represented by (), and collective planes are represented by {}. Regarding negative indices, in crystallography, a "-" (bar) is added to the number, but in this specification, a negative sign is added in front of the number.

[0069] In addition, the expression "a ± b" represents a range from "a - b" to "a + b".

[0070] First, define the directions. Set the crystal growth direction of the SiC ingot 10 as the Z direction. The Z direction is the height direction of the cylindrical SiC ingot 10. Set one direction of the plane orthogonal to the Z direction as the X direction. The X direction is, for example, the <11-20> direction. Additionally, on the plane orthogonal to the Z direction, set the direction orthogonal to the X direction as the Y direction. The Y direction is, for example, the <1-100> direction.

[0071] <SiC ingot>

[0072] Figure 1 is a perspective view of the SiC ingot 10 of the present embodiment. The SiC ingot 10 is a single crystal of cylindrical SiC. The SiC ingot 10 is processed into a cylindrical shape so as to cut out the SiC substrate.

[0073] The diameter D of the SiC ingot 10 is, for example, 145 mm or more, preferably 149 mm or more, more preferably 155 mm or less, and further preferably 151 mm or less. The diameter D of the SiC ingot 10 is, for example, 195 mm or more, preferably 199 mm or more, more preferably 205 mm or less, and further preferably 201 mm or less. The SiC ingot 10 can be, for example, an ingot capable of obtaining a 6-inch substrate or an ingot capable of obtaining an 8-inch substrate. The diameter D of the SiC ingot 10 is substantially the same as the diameter of the processed SiC substrate.

[0074] The thickness (height in the crystal growth direction) T of the SiC ingot 10 is, for example, 20 mm or more, preferably 30 mm or more, more preferably 40 mm or more, further preferably 50 mm or more, and particularly preferably 60 mm or more. The thickness T of the SiC ingot 10 can also be 100 mm or more. The thicker the thickness of the SiC ingot 10, the more SiC substrates can be obtained. Additionally, the thickness T of the SiC ingot 10 can be 300 mm or less.

[0075] The SiC ingot 10 has, for example, a first end 1, a second end 2, and a side surface 3. The first end 1 is the terminal in the crystal growth direction and is, for example, the (000-1) plane or a plane inclined and offset by an angle from the (000-1) plane. The second end 2 is the end on the opposite side of the first end 1 and is, for example, the (0001) plane or a plane inclined and offset by an angle from the (0001) plane. The first end 1 and the second end 2 are the bottom and top surfaces of the cylinder. The side surface 3 is the surface connecting the first end 1 and the second end 2 and is the side surface of the cylinder.

[0076] Figure 2 is a cross-sectional view of the SiC ingot 10 of the present embodiment. The SiC ingot 10 has a facet 4 and a step-flow growth region 5.

[0077] The SiC ingot 10 is crystallized and grown on a SiC seed crystal. In order to suppress the generation of different polytypes, a seed crystal having an offset angle with respect to the {0001} plane is often used. The offset angle is, for example, 3.5° or more and 4.5° or less, preferably 4°. By causing the SiC to grow in a step-flow manner on the seed crystal, the generation of different polytypes can be suppressed. Even when the SiC ingot grows in a step-flow manner, a part of the crystal growth surface is parallel to the (0001) plane, and a plane parallel to the (0001) plane is exposed on the crystal growth surface. Since the crystal grows perpendicular to the (0001) plane, the plane parallel to the (0001) plane does not grow in a step-flow manner.

[0078] The facet 4 is a region where the crystal grows perpendicular to the (0001) plane. The step-flow growth region 5 is a region where the crystal grows in a step-flow manner. The step-flow growth region 5 has an offset angle with respect to the {0001} plane of, for example, 3.5° or more and 4.5° or less.

[0079] Figure 3 It is a plan view of a cut surface obtained by cutting the SiC ingot 10 of the present embodiment on a plane substantially orthogonal to the Z direction. Substantially orthogonal means intersecting within a range of 90° ± 1° with respect to the Z direction. The XY plane of the SiC ingot 10 is substantially circular. The SiC ingot 10 may have an orientation plane 6 or a notch for grasping the crystal axis direction.

[0080] As Figure 3 shown, when viewed from the Z direction, the facet 4 and the step-flow growth region 5 have different colors, and the boundary can be visually observed. This is because the crystal growth modes of the facet 4 and the step-flow growth region 5 are different. The facet 4 is visually observed as a region with a darker hue than the step-flow growth region 5.

[0081] The boundary between the facet 4 and the step-flow growth region 5 can be judged visually, but it can also be judged according to the following steps. First, an image of the cross-section to be measured is obtained. The image is obtained, for example, by double-side polishing the substrate and using a scanner. The scanner can be, for example, a flatbed scanner manufactured by Canon. An image can also be obtained using a digital camera. Next, the obtained image is converted into the HLS color space composed of hue, brightness, and saturation, and the brightness is obtained. Then, in the image converted into the brightness distribution, a circle with a radius of X pixels is drawn with an arbitrary pixel as the center. When there are pixels in this circle with a brightness difference of Y or more from the central pixel, the pixel at the center of the circle becomes a pixel candidate for the facet. When there are no pixels in this circle with a brightness difference of Y or more from the central pixel, the pixel at the center of the circle becomes a pixel candidate for non-facet. Next, the same process is performed for all the pixels in the image, and each pixel is classified as a pixel candidate for the facet or a pixel candidate for non-facet. Then, the boundary between the pixel candidates for the facet and the pixel candidates for non-facet is detected, and the inside of this region becomes the facet. In addition, among the pixel candidates for the facet, pixels that are relatively far apart from other pixel candidates for the facet can be judged as pixel candidates for non-facet. The radius X of the circle and the brightness difference Y are set according to the size and number of pixels of the image. These settings are made with values such that the visual result and the judgment result do not deviate much. For example, in the case of using an image of 640 pixels × 480 pixels including a 150 mm wafer, the radius X is set to 9 pixels and the brightness difference Y is set to 4 W·sr -1 ·m -2 。

[0082] Here, a hypothetical rectangle (virtual rectangle) 7 that encloses the facet 4 with the minimum area is assumed. The hypothetical rectangle 7 is a rectangle having a first side 8 and a second side 9. The first side 8 is a side parallel to the <11 - 20> direction (X direction). The second side 9 is a side parallel to the <1 - 100> direction.

[0083] The length Lx of the first side 8 satisfies Lx / D < 0.3 in relation to the diameter D of the SiC ingot 10. Preferably, Lx / D satisfies Lx / D ≤ 0.25, more preferably Lx / D ≤ 0.2, further preferably Lx / D ≤ 0.15, and particularly preferably Lx / D ≤ 0.1. Additionally, Lx / D can satisfy 0.05 < Lx / D, preferably 0.06 < Lx / D, and more preferably 0.07 < Lx / D. This relationship is preferably satisfied at the first end 1 of the SiC ingot 10. Additionally, this relationship is more preferably satisfied at the second end 2 of the SiC ingot 10 as well. Additionally, the relationship of Lx / D is further preferably satisfied in the cut surface obtained by cutting the SiC ingot 10 at one position in the Z direction with a plane substantially orthogonal to the Z direction. The relationship of Lx / D is further preferably satisfied in each cut surface obtained by cutting the SiC ingot 10 at two or more positions in the Z direction with a plane substantially orthogonal to the Z direction. The relationship of Lx / D is further preferably satisfied in each cut surface obtained by cutting the SiC ingot 10 at five or more positions in the Z direction with a plane substantially orthogonal to the Z direction. The relationship of Lx / D is further preferably satisfied in the cut surface obtained by cutting the SiC ingot 10 at any position in the Z direction with a plane substantially orthogonal to the Z direction.

[0084] If the SiC ingot 10 satisfies the above relationship, the efficiency of obtaining the SiC substrate using a laser is improved. When obtaining the SiC substrate using a laser, the process of scanning the laser in the Y direction and irradiating it while moving in the X direction is repeated. When there is a facet 4 in the middle of scanning the laser in the Y direction, in order to generate appropriate cracks, it is necessary to change the laser output. This is because the resistance values of the facet 4 and the step flow growth region 5 are different. If the width of the facet 4 in the X direction is narrow, the width of the part where the laser output needs to be changed in the middle of scanning the laser in the Y direction becomes narrow. That is to say, if Lx / D < 0.3, the proportion of the part where the laser can be scanned without changing the laser output is large, and the SiC substrate can be cut out efficiently. Additionally, the smaller the value of Lx / D, the more significant this tendency becomes.

[0085] Additionally, Figure 4 is a top view of the cut surface obtained by cutting the SiC ingot of the comparative example with a plane orthogonal to the Z direction. Figure 4 In the example shown, 0.05 ≥ Lx / D. If the value of Lx / D is too small, as Figure 4 shown, the facet 4 bends and mostly becomes crescent-shaped. If the facet 4 is crescent-shaped, during one scan of the laser in the Y direction, it may be necessary to change the laser output multiple times. In this case, the number of times of changing the laser output for generating appropriate cracks increases, so the productivity for obtaining the SiC substrate deteriorates.

[0086] For example, Figure 5It is a top view of a SiC substrate cut from a SiC ingot satisfying 0.05 ≥ Lx / D. As Figure 5 shown, the curvature of the facet 4 with a small Lx / D value can be confirmed.

[0087] The length Lx of the first side 8 is preferably 30 mm or less, more preferably 25 mm or less, further preferably 20 mm or less, further preferably 15 mm or less, and further preferably 10 mm or less.

[0088] In addition, the length Ly of the second side 9 preferably satisfies Ly / D < 0.5, more preferably satisfies Ly / D ≤ 0.45, and further preferably satisfies Ly / D ≤ 0.4 in relation to the diameter D of the SiC ingot 10. This relationship is preferably satisfied at the first end 1 of the SiC ingot 10. In addition, this relationship is more preferably satisfied at the second end 2 of the SiC ingot 10, and further preferably satisfied in the cross-sectional plane obtained by cutting the SiC ingot 10 at a position in the Z direction with a plane substantially orthogonal to the Z direction. In addition, this relationship is further preferably satisfied in each cross-sectional plane obtained by cutting the SiC ingot 10 at two or more positions in the Z direction with a plane substantially orthogonal to the Z direction. In addition, this relationship is further preferably satisfied in each cross-sectional plane obtained by cutting the SiC ingot 10 at five or more positions in the Z direction with a plane substantially orthogonal to the Z direction. In addition, this relationship is further preferably satisfied in the cross-sectional plane obtained by cutting the SiC ingot 10 at any position in the Z direction with a plane substantially orthogonal to the Z direction. In addition, Ly / D can be greater than 0.01.

[0089] If the value of Ly / D is large, the facet 4 bends and the possibility of becoming a crescent shape becomes high.

[0090] By making the top view shape of the facet 4 elliptical, the number of laser output changes can be reduced.

[0091] <Manufacturing method of SiC ingot>

[0092] Next, the manufacturing method of the SiC ingot 10 of the present embodiment will be described. Figure 6 It is a cross-sectional view of an example of the manufacturing apparatus of the SiC ingot 10 of the present embodiment. The manufacturing apparatus of the SiC ingot 10 includes a crucible 20, a heat insulating material 30, an inner lining quartz tube 40, a quartz tube 50, and a reflectivity measuring device 60.

[0093] The crucible 20 is made of graphite, for example. The crucible 20 has a storage part 21 and a lid 22. A gas discharge path 23 is formed between the storage part 21 and the lid 22. The gas discharge path 23 is located at at least one place, and may also be at multiple places, on the outer side surface of the crucible 20. Additionally, the gas discharge path 23 can be annular around the outer side surface of the crucible 20 between the storage part 21 and the lid 22. The storage part 21 is supported and fixed by a support 24. The lid 22 is suspended by a suspension member 25 and can move up and down. The distance between the storage part 21 and the lid 22 can be freely changed by moving the suspension member 25 up and down. That is, the width of the gas discharge path 23 in the Z direction can be freely designed.

[0094] A seed crystal S and a SiC raw material M are arranged in a film formation space A inside the crucible 20. The gas sublimated from the SiC raw material M recrystallizes on the surface of the seed crystal S, and thus the SiC ingot 10 grows by crystallization. The residual gas inside the film formation space A is discharged to the outside of the crucible 20 through the gas discharge path 23.

[0095] The atmospheric pressure during crystal growth inside the film formation space A is greater than 0.3 torr and less than 10 torr. If the pressure inside the film formation space A is too low, sufficient doping elements cannot be contained in the crystal, and the resistivity of the SiC ingot 10 becomes high. The resistivity of the SiC ingot 10 is a parameter affecting laser processing. Additionally, if the pressure of the film formation space A is too high, sufficient sublimated gas cannot be generated from the SiC raw material M, and the productivity decreases.

[0096] The volume density of the graphite forming the side surface of the crucible 20 is greater than 1.75 g / cm 3 and less than 2.00 g / cm 3 . A part of the residual gas inside the film formation space A permeates through the crucible 20 and is discharged to the outside. If the volume density of the graphite forming the crucible 20 is low, a large amount of residual gas will be discharged from parts other than the gas discharge path 23. The residual gas discharged from positions other than the gas discharge path 23 deteriorates the heat insulating material 30. On the other hand, if the volume density of the graphite forming the crucible 20 is too high, the heat conduction amount of the graphite is too large, and an appropriate temperature distribution cannot be formed inside the crucible 20.

[0097] The volume G of the graphite forming the crucible 20 is 1.5 times or more and 4.0 times or less of the volume F based on the diameter of the seed crystal S. The volume F corresponds to the inner volume of the crucible 20. When the diameter of the seed crystal S is set as d, it is obtained by π×d 3 / 2. If the volume of the graphite is small, the residual gas permeating through the crucible 20 increases, and the heat insulating material 30 deteriorates. If the volume of the graphite is too large, the wall thickness of the graphite is too thick, and an appropriate temperature distribution cannot be formed inside the crucible 20.

[0098] The heat insulating material 30 covers the periphery of the crucible 20. The volume of the heat insulating material 30 is more than 1 times and less than 3 times the volume of the crucible 20. The volume of the heat insulating material 30 is the volume of the heat insulating material 30 itself, which is the volume of the region surrounded by the outer surface and the inner surface of the heat insulating material 30. The volume of the crucible 20 is the volume of the interior surrounded by the outer surface of the crucible. By making the volume of the heat insulating material 30 within this range, an appropriate temperature distribution can be formed within the crucible 20. The temperature distribution within the crucible 20 affects the formation of the facet 4.

[0099] In addition, the outer diameter of the heat insulating material 30 is 1.2 times or more and 1.5 times or less the outer diameter of the crucible 20. The heat insulating material 30 located on the side surface of the crucible 20 is in direct contact with the crucible 20 that generates heat due to induction heating, so the heat insulating performance is likely to deteriorate. By making the heat insulating material 30 have a sufficient width, deterioration of the heat insulating material 30 can be prevented, and an appropriate temperature distribution can be achieved within the crucible 20.

[0100] The inner lining quartz tube 40 is located around the heat insulating material 30. At least a part of the inner lining quartz tube 40 faces the end of the gas discharge path 23. The residual gas discharged from the gas discharge path 23 is irradiated onto the inner lining quartz tube 40. The inner lining quartz tube 40 is supported by the support 41. By moving the support 41 up and down, the inner lining quartz tube 40 also moves up and down. During crystal growth, the inner lining quartz tube 40 moves downward at a constant speed. The residual gas discharged from the gas discharge path 23 is blown onto the inner lining quartz tube 40 and solidifies on the inner wall of the inner lining quartz tube 40. The reflectivity of the inner lining quartz tube 40 increases due to the solidification of the residual gas.

[0101] The quartz tube 50 surrounds the crucible 20, the heat insulating material 30, and the inner lining quartz tube 40. The quartz tube 50 is covered by the upper cover 51 and the lower cover 52. The quartz tube 50 controls the atmosphere inside.

[0102] The reflectivity detector 60 measures the reflectivity of the part of the inner lining quartz tube 40 irradiated by the residual gas. The more the gas discharge amount from the gas discharge path 23, the higher the reflectivity of this part.

[0103] The reflectivity detector 60 measures the gas discharge amount from the gas discharge path 23 by measuring the reflectivity of the part of the inner lining quartz tube 40 irradiated by the gas. During crystal growth, the inner lining quartz tube 40 moves downward at a constant speed. Therefore, the position of the inner lining quartz tube 40 irradiated by the gas is always changing. If the gas discharge amount from the gas discharge path 23 is constant, the reflectivity of the part of the inner lining quartz tube 40 whose reflectivity is measured by the reflectivity detector 60 is constant.

[0104] When producing the desired SiC ingot 10, it is necessary to make the flow of the sublimation gas in the film formation space A constant. If the gas discharge amount from the gas discharge path 23 changes, the flow of the sublimation gas in the film formation space A changes.

[0105] In the manufacturing apparatus for the SiC ingot 10 of the present embodiment, when the reflectivity of the portion measured by the reflectivity measuring device 60 changes, the suspension member 25 is moved up and down to change the width of the gas discharge path 23. For example, when the reflectivity of the portion measured by the reflectivity measuring device 60 decreases, the gas discharge amount from the gas discharge path 23 is small, so the width of the gas discharge path 23 is widened. For example, when the reflectivity of the portion measured by the reflectivity measuring device 60 increases, the gas discharge amount from the gas discharge path 23 is large, so the width of the gas discharge path 23 is narrowed.

[0106] As described above, the manufacturing apparatus for the SiC ingot 10 of the present embodiment can also control the flow of the sublimation gas in the film formation space A by changing the width of the gas discharge path 23. In this way, by controlling the temperature distribution and the flow of the sublimation gas in the film formation space A, the SiC ingot of the present embodiment can be produced.

[0107] In addition, Figure 7 is a cross-sectional view of another example of the manufacturing apparatus for the SiC ingot 10 of the present embodiment. Figure 7 The manufacturing apparatus for the SiC ingot 10 shown includes a crucible 20, a heat insulating material 30, a quartz tube 50, a weight measuring device 70, and an evaluation substrate 71. Figure 7 In the manufacturing apparatus for the SiC ingot 10 shown, the evaluation substrate 71 is provided instead of the inner lining quartz tube 40, and the weight measuring device 70 is provided instead of the reflectivity measuring device 60. The structures of the crucible 20, the heat insulating material 30, and the quartz tube 50 are the same as those in Figure 6 the same.

[0108] In Figure 7 the manufacturing apparatus for the SiC ingot 10 shown, the residual gas discharged from the gas discharge path 23 is irradiated onto the evaluation substrate 71. The residual gas irradiated onto the evaluation substrate 71 solidifies on the surface of the evaluation substrate 71. The weight of the evaluation substrate 71 becomes heavier due to the solidification of the residual gas.

[0109] The weight measuring device 70 measures the weight of the evaluation substrate 71. If the gas discharge amount from the gas discharge path 23 is constant, the increase rate of the weight of the evaluation substrate 71 is constant. In contrast, if the gas discharge amount from the gas discharge path 23 increases, the increase rate of the weight of the evaluation substrate 71 increases, and if the gas discharge amount from the gas discharge path 23 decreases, the increase rate of the weight of the evaluation substrate 71 decreases. Figure 7The manufacturing apparatus of the SiC ingot 10 shown evaluates the gas discharge amount from the gas discharge path 23 based on the change in the weight increase rate of the evaluation substrate 71.

[0110] Figure 7 The manufacturing apparatus of the SiC ingot 10 shown can control the flow of the sublimation gas in the film formation space A by changing the width of the gas discharge path 23 in such a way that the gas discharge amount from the gas discharge path 23 is constant. In this way, by controlling the temperature distribution and the flow of the sublimation gas in the film formation space A, the SiC ingot of the present embodiment can be fabricated.

[0111] Here, as an example of the evaluation method of the gas discharge amount from the gas discharge path 23, examples using the change in reflectivity and the change in weight are shown, but the physical quantity used to evaluate the gas discharge amount from the gas discharge path 23 is not limited to this.

[0112] As described above, the shape of the facet 4 of the SiC ingot 10 of the present embodiment is controlled. The SiC ingot 10 of the present embodiment is controlled to reduce the number of times the scanning direction of the laser intersects the facet 4, and the number of times the laser output is changed during laser processing can be reduced. Therefore, when cutting out the SiC substrate using the laser from the SiC ingot 10 of the present embodiment, the number of times the laser output is changed can be reduced, and the SiC substrate can be efficiently fabricated.

[0113] <Manufacturing method of SiC substrate>

[0114] The manufacturing method of the SiC substrate according to the first embodiment includes the step of fabricating the SiC ingot 10 of the above embodiment by any of the above methods, and the step of slicing the SiC ingot 10.

[0115] As the step of slicing the SiC ingot 10, for example, a method of cutting out the SiC substrate by generating cracks in the SiC ingot 10 through laser processing can be adopted. The SiC ingot 10 can be processed into a cylindrical shape before slicing the SiC ingot 10.

[0116] The SiC substrate cut from the SiC ingot 10 of the present embodiment has a high possibility of satisfying Lx / D < 0.3. For example, when the SiC ingot 10 satisfies Lx / D < 0.3 in any cross-sectional plane orthogonal to the crystal growth direction, the SiC substrate cut from the SiC ingot 10 satisfies Lx / D < 0.3. In other words, when multiple SiC substrates cut from the same SiC ingot all satisfy Lx / D < 0.3, it can be said that the SiC ingot before cutting corresponds to the SiC ingot of the present embodiment. For example, when SiC substrates with a thickness of 0.5 mm cut from the same SiC ingot all satisfy Lx / D < 0.3, the thickness of the SiC ingot before cutting is 20 mm or more, and it can be said to correspond to the SiC ingot of the present embodiment.

[0117] The manufacturing method of the SiC substrate of the second embodiment includes a step of preparing the SiC ingot 10 of the above embodiment and a step of slicing the SiC ingot 10.

[0118] The step of preparing the SiC ingot 10 may include obtaining the SiC ingot 10 of the above embodiment from other companies. The SiC ingot 10 may also be a boule as long as it satisfies the requirements of the above embodiment.

[0119] The step of slicing the SiC ingot 10 is the same as that of the first embodiment. Additionally, the SiC ingot 10 may be processed into a cylindrical shape before slicing the SiC ingot 10.

[0120] As described above, the preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to specific embodiments, and various modifications and changes can be made within the scope of the gist (technical requirements) of the present invention described in the claims.

[0121] Examples

[0122] <Example 1>

[0123] Using Figure 6 The SiC ingot manufacturing apparatus shown, while controlling the temperature distribution and the flow of the sublimation gas in the film formation space A, a SiC ingot with a diameter of 150 mm is produced. The SiC ingot of Example 1 has a facet at the first end which is the terminal of the crystal growth direction.

[0124] The length Lx of the first side of the imaginary rectangle that encloses the facet with the minimum area is 15 mm. That is, the SiC ingot of Example 1 satisfies Lx / D = 0.1.

[0125] Next, the SiC ingot of Example 1 was subjected to laser processing to cut out a SiC substrate. The scanning pitch of the laser was 200 μm, the feed rate of the laser scanning was 200 mm / sec, the number of scanning times was 1 time, the acceleration / deceleration time was 0.1 second, and the inter-line movement time was 0.1 second. The acceleration / deceleration time is the time required for acceleration / deceleration when scanning the laser in one direction and then scanning the laser in the opposite direction. The inter-line movement time represents the time taken for the movement in the X direction in the process of repeatedly performing laser scanning in the Y direction and movement in the X direction. When the laser crosses the boundary of the facet and the step flow growth region, in order to change the laser output, the scanning is stopped for 0.5 second.

[0126] The process time required to cut out one SiC substrate from the SiC ingot of Example 1 was 11.1 minutes.

[0127] <Example 2>

[0128] The pressure of the atmosphere in the film formation space A was adjusted to a value different from that of Example 1, and a SiC ingot with a diameter of 150 mm was produced in the same manner as in Example 1. The SiC ingot of Example 2 had a facet at the first end which was the terminal of the crystal growth direction.

[0129] The length Lx of the first side of the imaginary rectangle that encloses the facet with the minimum area was 36 mm. That is, in the SiC ingot of Example 2, Lx / D = 0.24.

[0130] Next, the SiC ingot of Example 2 was subjected to laser processing to cut out a SiC substrate. The laser conditions when cutting out the SiC substrate were the same as those in Example 1.

[0131] The process time required to cut out one SiC substrate from the SiC ingot of Example 2 was 12.9 minutes.

[0132] <Comparative Example 1>

[0133] Without using Figure 6 the SiC ingot manufacturing apparatus shown, a SiC ingot with a diameter of 150 mm was produced by growing the SiC ingot in a sealed crucible. The SiC ingot of Comparative Example 1 had a facet at the first end which was the terminal of the crystal growth direction. The length Lx of the first side of the imaginary rectangle that encloses the facet with the minimum area was 60 mm. That is, the SiC ingot of Comparative Example 1 satisfied Lx / D = 0.4.

[0134] Next, the SiC ingot of Comparative Example 1 was subjected to laser processing to cut out a SiC substrate. The laser conditions when cutting out the SiC substrate were the same as those in Example 1.

[0135] The process time required to cut out one SiC substrate from the SiC ingot of Comparative Example 1 was 14.9 minutes.

[0136] The SiC ingots of Examples 1 and 2 require a shorter processing time to cut out SiC substrates compared to the SiC ingot of Comparative Example 1.

[0137] In Examples 1 and 2 and Comparative Example 1, the results of SiC ingots with a processed diameter of 150 mm are shown. SiC ingots with a processed diameter of 200 mm were also fabricated and evaluated in the same manner. In the SiC ingots with a processed diameter of 200 mm, the same evaluation results as those of the SiC ingots with a processed diameter of 150 mm were also confirmed.

[0138] That is, in the SiC ingots fabricated under the conditions of the present embodiment, Lx / D < 0.3 is satisfied. In the SiC ingots fabricated under the conditions not satisfying the present embodiment, Lx / D ≥ 0.3. In addition, compared to the SiC ingots fabricated under the conditions not satisfying the present embodiment, the time required to cut out one SiC substrate is shorter in the SiC ingots fabricated under the conditions of the present embodiment.

Claims

1. A SiC ingot having facets, When the diameter is D and the length of the first side of an imaginary rectangle that surrounds the facet with the minimum area when viewed from the crystal growth direction and has a first side parallel to the <11-20> direction and a second side parallel to the <1-100> direction is Lx, At the first end, which is the terminal end of the crystal growth direction, Lx / D<0.3 is satisfied.

2. The SiC ingot according to claim 1, At the first end, 0.05<Lx / D<0.3 is satisfied.

3. The SiC ingot according to claim 1, At the first end, Lx / D≤0.2 is satisfied.

4. The SiC ingot according to claim 1, At the first end, Lx / D≤0.1 is satisfied.

5. The SiC ingot according to claim 1, At the second end on the opposite side to the first end, Lx / D<0.3 is satisfied.

6. The SiC ingot according to claim 5, At the second end, 0.05<Lx / D<0.3 is satisfied.

7. The SiC ingot according to claim 1, In one cut surface intersecting the crystal growth direction within the range of 90°±1°, Lx / D<0.3 is satisfied.

8. The SiC ingot according to claim 1, In two or more cut surfaces intersecting the crystal growth direction within the range of 90°±1°, Lx / D<0.3 is satisfied.

9. The SiC ingot according to claim 1, In five or more cut surfaces intersecting the crystal growth direction within the range of 90°±1°, Lx / D<0.3 is satisfied.

10. The SiC ingot according to claim 1, In any cross section intersecting the crystal growth direction within the range of 90°±1°, Lx / D<0.3 is satisfied.

11. The SiC ingot according to claim 1, The portion has an off angle of 3.5° or more and 4.5° or less with respect to the {0001} plane.

12. The SiC ingot according to claim 1, The height in the crystal growth direction is greater than 20 mm.

13. The SiC ingot according to claim 1, The diameter is 145mm or more.

14. The SiC ingot according to claim 1, The diameter is 195mm or more.

15. The SiC ingot according to claim 1, When the length of the second side of the imaginary rectangle is Ly, At the first end, 0.5>Ly / D is satisfied.

16. The SiC ingot according to claim 1, When the length of the second side of the imaginary rectangle is Ly, In any cross section intersecting the crystal growth direction within the range of 90°±1°, 0.5>Ly / D is satisfied.

17. A method for manufacturing a SiC substrate, comprising: A step of producing the SiC ingot according to any one of claims 1 to 16; and The step of slicing the SiC ingot is as follows.

18. A method for manufacturing a SiC substrate, comprising: A step of preparing the SiC ingot according to any one of claims 1 to 16; and The step of slicing the SiC ingot is as follows.

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