SiC crystal ingot and method for manufacturing SiC substrate

Abstract

This SiC crystal ingot is composed of a SiC single crystal grown by crystal growth from a first end to a second end inclined at an offset angle from a (0001) plane, and has a stepped flow growth region and a facet, and in a cross-section along a < 11-20 > direction through the center, the angle [theta] 1 formed by the crystal growth direction and the inner boundary between the facet and the stepped flow growth region is 56 DEG or less.

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, and incorporates their contents herein. 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. The SiC substrate is cut from a SiC ingot. The SiC ingot is formed by crystal growth of a SiC single crystal on a seed crystal. When crystal growth of a SiC single crystal is performed on the seed crystal, a facet and a step flow growth region are formed.

[0005] Patent Document 1 describes a method for manufacturing a SiC single crystal. In addition, Patent Document 1 describes that if the temperature of the facet region is made lower than that of the non-facet region or the raw material gas concentration of the facet region is made higher than that of the non-facet region from the initial stage to the middle stage of growth, the growth of the facet region and its vicinity is promoted and the area of the facet region becomes smaller.

[0006] Prior Art Documents

[0007] Patent Document 1: Japanese Patent No. 6050053 Gazette 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 when cutting out the SiC substrate using a laser varies depending on the resistance value of the SiC single crystal. If the laser output is small, sufficient cracks will not be generated. Additionally, if the laser output is large, the SiC single crystal will be damaged.

[0010] The facet of the SiC ingot has a lower resistance value compared to the step-flow growth region of step-flow growth. Therefore, when cutting out a SiC substrate from the SiC ingot, it is necessary to change the laser output at the boundary between the facet and the step-flow growth region. The more times the laser output is changed during the process of cutting out the SiC substrate, the lower the productivity.

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

[0012] Means for Solving the Problems

[0013] In order to reduce the number of changes in the laser output when cutting out a SiC substrate from a SiC ingot by laser processing and improve productivity, the inventor of the present invention focused on the shape of the facet of the SiC ingot and conducted in-depth research. As a result, it was found that as long as the SiC ingot has a facet controlled to a specific shape, the present invention was conceived. The present invention provides the following technical means.

[0014] [1] A SiC ingot composed of a SiC single crystal that crystallizes and grows from a first end inclined by an offset angle from the (0001) plane to a second end, having a step-flow growth region and a facet,

[0015] In a cross-sectional plane passing through the center and along the <11-20> direction, the angle formed by the inner boundary between the facet and the step-flow growth region and the crystal growth direction is 56° or less.

[0016] [2] The SiC ingot according to [1], the inner boundary extending from the first end to the second end is inclined at an angle greater than 0° and 56° or less in the [-1-120] direction with respect to the thickness direction from the first end to the second end.

[0017] [3] The SiC ingot according to [1] or [2], having a diameter of 149 mm or more.

[0018] [4] The SiC ingot according to [1] or [2], having a diameter of 199 mm or more.

[0019] [5] The SiC ingot according to any one of [1] to [4], the maximum thickness in the direction perpendicular to the first end between the first end and the second end is 10 mm or more.

[0020] [6] The SiC ingot according to any one of [1] to [4], the maximum thickness in the direction perpendicular to the first end between the first end and the second end is 20 mm or more.

[0021] [7] The SiC ingot according to any one of [1] to [4], the maximum thickness in the direction perpendicular to the first end between the first end and the second end is 30 mm or more.

[0022] [8] The SiC ingot according to any one of [1] to [4], the maximum thickness in the direction perpendicular to the first end between the first end and the second end is 40 mm or more.

[0023] [9] The SiC ingot according to any one of [1] to [4], the maximum thickness in the direction perpendicular to the first end between the first end and the second end is 50 mm or more.

[0024]

[10] A method for manufacturing a SiC substrate, comprising:

[0025] A step of manufacturing the SiC ingot according to any one of [1] to [9];

[0026] A step of processing the SiC ingot into a cylindrical shape; and

[0027] A step of slicing the SiC ingot processed into a cylindrical shape.

[0028]

[11] A method for manufacturing a SiC substrate, comprising:

[0029] A step of preparing the SiC ingot according to any one of [1] to [9]; and

[0030] A step of slicing the SiC ingot.

[0031]

[12] An evaluation method for a SiC ingot, comprising:

[0032] A step of manufacturing a SiC ingot;

[0033] A step of processing the SiC ingot into a cylindrical shape;

[0034] A step of slicing the SiC ingot processed into a cylindrical shape to obtain a plurality of evaluation SiC substrates;

[0035] A process for measuring the positions of the facets and the inner boundaries of the step flow growth regions in each SiC substrate for evaluation;

[0036] A process for calculating the angles formed by the inner boundaries of the facets and the step flow growth regions in a cross-sectional plane passing through the center of the SiC ingot and along the <11-20> direction with respect to the crystal growth direction based on the relationship between the position of each SiC substrate for evaluation in the SiC ingot from which it is cut out and the position of the inner boundary of each SiC substrate for evaluation; and

[0037] An evaluation process for evaluating whether the SiC ingot is fabricated under conditions suitable for fabricating a SiC ingot to be sliced by laser processing based on the angle formed by the inner boundary and the crystal growth direction.

[0038] Advantages of the Invention

[0039] The SiC ingot of the present technical solution is composed of a SiC single crystal that crystallizes and grows from a first end inclined by an offset angle from the (0001) plane to a second end. In a cross-sectional plane passing through the center and along the <11-20> direction, the angle formed by the inner boundary of the facet and the step flow growth region with respect to the crystal growth direction is 56° or less. Therefore, the SiC ingot of the present technical solution can reduce the number of changes in the laser output when it is processed into a cylindrical shape and sliced into SiC substrates by laser processing, and can easily and efficiently cut out SiC substrates. Brief Description of the Drawings

[0040] Figure 1 It is a cross-sectional view of the SiC ingot according to this embodiment.

[0041] Figure 2 It is a top view of the SiC ingot according to this embodiment.

[0042] Figure 3 It is a cross-sectional view showing an example of the manufacturing apparatus used for manufacturing the SiC ingot according to this embodiment.

[0043] Figure 4 It is a cross-sectional view showing another example of the manufacturing apparatus used for manufacturing the SiC ingot according to this embodiment.

[0044] Description of the Reference Numerals

[0045] 1 First end

[0046] 2 Second end

[0047] 3 Side wall

[0048] 4 Facet

[0049] 5 Step flow growth region

[0050] 10 SiC ingot

[0051] 20 Crucible

[0052] 21 Storage part

[0053] 22 Lid

[0054] 23 Gas discharge path

[0055] 24 Support

[0056] 25 Suspension member

[0057] 30 Heat insulating material

[0058] 40 Inner lining quartz tube

[0059] 41 Support

[0060] 50 Quartz tube

[0061] 51 Upper lid

[0062] 52 Lower lid

[0063] 60 Reflectance measuring device

[0064] 70 Weight measuring device

[0065] 71 Evaluation substrate Detailed implementation mode

[0066] Hereinafter, the manufacturing method of the SiC ingot and the SiC substrate 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 constituent elements 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).

[0067] 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 exponents, in crystallography, a "-" (bar) is added to the number, but in this specification, a negative sign is added in front of the number.

[0068] First, the directions are defined. The crystal growth direction of the SiC ingot 10 is set as the Z direction. The Z direction is the height direction of the substantially cylindrical SiC ingot 10. One direction of the plane orthogonal to the Z direction is set as the X direction. The X direction is, for example, the <11-20> direction. For example, the +X direction is set as the [11-20] direction, and the -X direction is set as the [-1-120] direction. Further, on the plane orthogonal to the Z direction, the direction orthogonal to the X direction is set as the Y direction. The Y direction is, for example, the <1-100> direction.

[0069] <SiC ingot>

[0070] Figure 1 is a cross-sectional view of the SiC ingot 10 of the present embodiment. Figure 2 is viewed from the Z direction Figure 1 and is a top view of the SiC ingot 10 of the present embodiment shown in

[0071] The SiC ingot 10 has a substantially cylindrical shape and is a single crystal of SiC that crystallizes and grows from the Figure 1 shown first end 1 to the second end 2. The SiC ingot 10 may be an ingot processed into a cylindrical shape or an ingot before being processed into a cylindrical shape. The second end 2 is the terminal of the crystal growth direction. The first end 1 and the second end 2 are connected by a side wall 3. The SiC ingot 10 may have a diameter that increases from the first end 1 to the second end 2 or may be a cylinder with a constant diameter.

[0072] The first end 1 is a plane inclined by an offset angle from the (0001) plane (Si plane). The second end 2 is a plane inclined by an offset angle from the (000-1) plane (C plane). The second end 2 is opposite to the first end 1. The first end 1 and the second end 2 may have an offset angle of, for example, 0.1° or more and 8° or less in the <11-20> direction and may not have an offset angle in the <1-100> direction. Further, the offset angle of the SiC ingot is not limited to this example.

[0073] The diameter D of the SiC ingot 10 is, for example, 145 mm or more, preferably 149 mm or more, more preferably 150 mm or more, further preferably 151 mm or more, and may also be 199 mm or more. The diameter D of the SiC ingot 10 is, for example, 305 mm or less. The diameter D of the SiC ingot 10 may also be, for example, 230 mm or less, preferably 220 mm or less, more preferably 205 mm or less, and further preferably 201 mm or less.

[0074] Here, the diameter D of the SiC ingot 10 is the minimum diameter of the SiC ingot 10 and corresponds to the minimum value of the diameter of the SiC substrate that can be obtained from the SiC ingot 10. As Figure 1As shown, for example, when the SiC ingot 10 has a shape with a diameter that expands from the first end 1 to the second end 2, the diameter of the first end 1 corresponds to the diameter D of the SiC ingot 10. For example, when the SiC ingot 10 is in the shape of a cylinder with a constant diameter, the diameter of any cross-section obtained by cutting the SiC ingot 10 on a plane orthogonal to the Z direction corresponds to the diameter D of the SiC ingot 10. 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.

[0075] The thickness of the SiC ingot 10 is the maximum thickness in the direction perpendicular to the first end 1 between the first end 1 and the second end 2. The thickness of the SiC ingot 10 is, for example, 10 mm or more, preferably 20 mm or more, 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 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, so it is preferred. In addition, the thickness of the SiC ingot 10 is, for example, 300 mm or less.

[0076] The SiC ingot 10 has a facet 4 and a step-flow growth region 5.

[0077] The SiC ingot 10 is composed of a SiC seed crystal and a crystal growth portion that crystallizes and grows on the SiC seed crystal. As the SiC seed crystal, a seed crystal having an offset angle with respect to the {0001} plane is used. This is because, by causing step-flow growth of SiC single crystals on the SiC seed crystal, the generation of crystals of different polytypes can be suppressed. The tilt angle of the SiC seed crystal with respect to the {0001} plane is, for example, 3.5° or more and 4.5° or less, preferably 4°.

[0078] Even when step-flow growth of SiC single crystals is carried out on the SiC seed crystal, during the growth of the SiC single crystal, 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. On the plane parallel to the (0001) plane, since the crystal grows perpendicular to the (0001) plane, step-flow growth does not occur. The facet 4 of the SiC ingot 10 is a region where the crystal grows perpendicular to the (0001) plane. As Figure 2 shown, the facet 4 is a region that is approximately circular when viewed from the Z direction. The step-flow growth region 5 is a region where SiC single crystals grow by step-flow on the SiC seed crystal. As Figure 2 shown, the step-flow growth region 5 is formed so as to surround the facet 4. The step-flow growth region 5 has an offset angle with respect to the {0001} plane. The offset angle of the step-flow growth region 5 with respect to the {0001} plane is, for example, 3.5° or more and 4.5° or less, preferably 4°.

[0079] When looking down at the SiC ingot 10 from the Z direction (crystal growth direction), the facets 4 and the step-flow growth region 5 have different colors. This is because the crystal growth modes in the facets 4 and the step-flow growth region 5 are different. The facet 4 is visually observed as a region with a darker hue compared to the step-flow growth region 5. Therefore, the boundary between the facet 4 and the step-flow growth region 5 can be confirmed visually.

[0080] The boundary between the facet 4 and the step-flow growth region 5 when looking down at the SiC ingot 10 from the Z direction can be judged visually or can be judged according to the following steps.

[0081] First, obtain an image when looking down at the SiC ingot 10 from the Z direction. The image is obtained using a scanner, for example. As the scanner, a flatbed scanner manufactured by Canon can be used, for example. An image can also be obtained using a digital camera.

[0082] Next, convert the obtained image into an HLS color space composed of hue, lightness, and saturation, and obtain the lightness. Then, in the image converted into a lightness distribution, draw a circle with a radius of X pixels centered on an arbitrary pixel. When there is a pixel in the circle with a lightness difference of Y or more from the central pixel, the pixel serving as the center of the circle becomes a pixel candidate for a facet. When there is no pixel in the circle with a lightness difference of Y or more from the central pixel, the pixel serving as the center of the circle becomes a non-facet candidate pixel. Next, perform the same processing for all pixels of the image, and classify each pixel as a pixel candidate for a facet or a non-facet candidate pixel. Then, detect the boundary between the pixel candidates for facets and the non-facet candidate pixels, and the interior of this region can be regarded as a facet. In addition, among the pixel candidates for facets, pixels that are relatively far apart from other pixel candidates for facets can be judged as non-facet candidates. Set the radius X of the circle and the lightness difference Y 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 deviate little. For example, when using a 640-pixel × 480-pixel image including a wafer with a diameter of 150 mm obtained from the SiC ingot, set the radius X to 9 pixels and the lightness difference Y to 4 W·sr -1 ·m -2 。

[0083] In the XZ cross-section of the SiC ingot 10, the boundary between the facet 4 and the step-flow growth region 5 can also be judged visually. Hereinafter, among the boundaries between the facet 4 and the step-flow growth region 5, the boundary on the central side of the SiC ingot 10 located in the XZ cross-section of the SiC ingot 10 is called the inner boundary 6, and the boundary located outside the inner boundary 6 is called the outer boundary 7. In Figure 1In the SiC ingot 10 of the present embodiment shown, the inner boundary 6 and the outer boundary 7 are straight lines inclined in the -X direction with respect to the Z direction ( Figure 1 the crystal growth direction indicated by the symbol 8 in

[0084] As Figure 1 shown, the inner boundary 6 and the outer boundary 7 move toward the center side (-X direction: [-1-120] direction) of the SiC ingot 10 as they approach the second end 2 from the first end 1. That is, the closer to the second end 2 from the first end 1, the more the facet 4 enters the inside of the SiC ingot 10. As a result, the planar coordinates of the facet 4 at the first end 1 are different from the planar coordinates of the facet 4 at the second end 2.

[0085] Here, in the actual SiC ingot 10, only the planar coordinates of the facet 4 at the first end 1 or the second end 2 can be confirmed, and the planar coordinates of the inner facet 4 can only be estimated. The facet 4 is a region where the inhalation amount of doping elements such as nitrogen is larger than that in the step-flow growth region 5, so the resistance value is low and the light transmittance is low. Therefore, when the SiC ingot 10 is processed into a cylindrical shape for laser processing, it is necessary to make the laser output conditions different between the facet 4 and the step-flow growth region 5. For example, if there is a facet 4 at a position of the SiC ingot 4 where the facet 4 is supposed to be absent according to the planar coordinates of the facet 4 at the second end 2, the laser output may be insufficient during laser processing. That is, when the SiC ingot 10 is processed into a cylindrical shape and laser processed, the possibility of occurrence of defective conditions becomes high.

[0086] In contrast, in the SiC ingot 10 of the present embodiment, in the XZ cross-section (a cross-section passing through the center and along the <11-20> direction), the angle θ1 formed by the inner boundary 6 of the facet 4 and the step-flow growth region 5 and the crystal growth direction 8 is 56° or less. Therefore, the positional deviation between the planar coordinates of the facet 4 at the first end 1 and the planar coordinates of the facet 4 at the second end 2 becomes small enough. Therefore, the processing stability when the SiC ingot 10 is processed into a cylindrical shape and laser processed is high. The angle θ1 formed by the inner boundary 6 and the crystal growth direction 8 is preferably 50° or less, more preferably 45° or less, more preferably 40° or less, more preferably 35° or less, and further preferably 30° or less. The smaller the angle θ1 formed by the inner boundary 6 and the crystal growth direction 8, the better the processing stability when laser processing the SiC ingot processed into a cylindrical shape, and thus it is preferred. In addition, the SiC ingot 10 in which the angle θ1 formed by the inner boundary 6 and the crystal growth direction 8 is 10° or more can be easily manufactured, and thus it is preferred.

[0087] The angle at which the inner boundary 6 extending from the first end 1 to the second end 2 is inclined in the [-1-120] direction with respect to the thickness direction from the first end 1 to the second end 2 is preferably greater than 0° and 56° or less. In other words, it is preferable that the inner boundary 6 is inclined in the -X direction with respect to the Z direction ( Figure 1 the crystal growth direction indicated by the symbol 8 in

[0088] ). This is because, based on the planar coordinates of the facet 4 at the second end 2, it can be inferred that there is no facet 4 in the region of the SiC ingot 10 inside the planar coordinates of the facet 4 at the second end 2. Therefore, the processing stability during machining the SiC ingot 10 into a cylindrical shape and performing laser processing becomes higher. The angle at which the inner boundary 6 is inclined in the [-1-120] direction with respect to the thickness direction from the first end 1 to the second end 2 is preferably 50° or less, more preferably 45° or less, more preferably 40° or less, more preferably 35° or less, and further preferably 30° or less.

[0089] In the SiC ingot 10 of the present embodiment, the angle θ1 formed by the inner boundary 6 and the crystal growth direction 8 is constant (in other words, the inner boundary 6 in the XZ cross-section is a straight line). The angle θ1 formed by the inner boundary 6 and the crystal growth direction 8 in the SiC ingot 10 may also vary according to the position in the Z direction. In this case, the average value of the angle θ1 formed by the inner boundary 6 and the crystal growth direction 8 is regarded as the angle θ1 formed by the inner boundary 6 and the crystal growth direction 8. The angle θ1 formed by the inner boundary 6 and the crystal growth direction 8 is the average value of the angles θ1 formed by the inner boundary 6 and the crystal growth direction 8 measured at 5 different positions in the Z direction with different positions.

[0089] In the SiC ingot 10 of the present embodiment, as Figure 1 shown, the distance between the inner boundary 6 and the outer boundary 7 in the XZ cross-section preferably widens as approaching the second end 2 from the first end 1. In other words, it is preferable that the area of the facet 4 at the second end 2 is larger than the area of the facet 4 at the first end 1. This is because the generation of crystals of different polytypes can be suppressed, and the growth of SiC single crystals can be made more stable. In addition, based on the planar coordinates of the facet 4 at the second end 2, it can be inferred that there is no facet 4 in the region of the SiC ingot 10 wider than the planar coordinates of the facet 4 at the second end 2.

[0090] <Manufacturing method of SiC ingot>

[0091] Next, an example of the manufacturing method of the SiC ingot 10 of the present embodiment will be described. Figure 3 It is a cross-sectional view showing an example of the manufacturing apparatus used when manufacturing the SiC ingot 10 of the present embodiment.

[0092] Figure 3The manufacturing apparatus for the SiC ingot 10 shown includes a crucible 20, a heat insulating material 30, a lining quartz tube 40, a quartz tube 50, and a reflectivity measuring device 60.

[0093] The crucible 20 is made of, for example, graphite. 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 provided at at least one place on the outer side surface of the crucible 20, and may also be provided at multiple places. The gas discharge path 23 may also be provided in a ring shape on the entire circumference of 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 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 the 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 single crystal, which is the crystal growth part of the SiC ingot 10, grows. The residual gas in the film formation space A is discharged to the outside of the crucible 20 through the gas discharge path 23.

[0095] The atmosphere pressure during crystal growth in the film formation space A is greater than 0.3 torr and less than 10 torr. If the pressure in the film formation space A is too low, doping elements such as nitrogen cannot be sufficiently supplied into the crystal, resulting in a high resistivity of the SiC ingot 10. The resistivity of the SiC ingot 10 is a parameter that affects laser processing. In addition, if the pressure in the film formation space A is too high, sublimation gas cannot be sufficiently generated from the SiC raw material M, resulting in a reduction in productivity.

[0096] The volume density of the graphite constituting 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 in the film formation space A permeates through the crucible 20 and is discharged to the outside. If the volume density of the graphite constituting 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 parts other than the gas discharge path 23 will deteriorate the heat insulating material 30. On the other hand, if the volume density of the graphite constituting the crucible 20 is too high, the heat conduction amount of the graphite will be too high, resulting in an inappropriate temperature distribution not being able to be formed inside the crucible 20.

[0097] The volume G of the graphite constituting 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 π×d 3It is obtained by dividing by 2. If the volume G of the graphite forming the crucible 20 is small, the residual gas passing through the crucible 20 increases, deteriorating the heat insulating material 30. If the volume G of the graphite is too large, the wall thickness of the crucible 20 becomes too thick, and an appropriate temperature distribution cannot be formed inside the crucible 20.

[0098] The heat insulating material 30 is substantially cylindrical and is arranged so as to cover 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, and the volume of the crucible 20 is the volume of the interior surrounded by the outer surface of the crucible 20. By making the volume of the heat insulating material 30 within the above range, an appropriate temperature distribution can be formed inside the crucible 20. The temperature distribution inside the crucible 20 affects the formation of the facet 4.

[0099] 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 outer shape of the heat insulating material 30 within the above range, deterioration of the heat insulating material 30 can be prevented, and an appropriate temperature distribution can be formed inside the crucible 20.

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

[0101] The quartz tube 50 surrounds the crucible 20, the heat insulating material 30, and the inner liner quartz tube 40. The quartz tube 50 is covered by an upper cover 51 and a lower cover 52. The atmosphere inside the film formation space A can be easily controlled in the quartz tube 50.

[0102] The reflectometer 60 measures the reflectivity of the portion of the inner liner quartz tube 40 irradiated by the residual gas discharged from the gas discharge path 23. The more the gas discharge amount from the gas discharge path 23, the higher the reflectivity of this portion. In Figure 3 In the manufacturing apparatus of the SiC ingot 10 shown, the gas discharge amount from the gas discharge path 23 is evaluated based on the change in the reflectivity of the inner liner quartz tube 40.

[0103] In crystal growth, the inner quartz tube 40 moves downward at a certain speed through the support 41. Therefore, the position where the residual gas is irradiated in the inner quartz tube 40 is always changing. If the gas discharge amount from the gas discharge path 23 is constant, the reflectivity of the portion of the inner quartz tube 40 measured by the reflectometer 60 is constant.

[0104] In order to manufacture the SiC ingot 10 in which the angle θ1 formed by the facet 4 and the inner boundary 6 of the step flow growth region 5 and the crystal growth direction 8 is 56° or less, it is necessary to make the flow of the sublimation gas in the film formation space A substantially constant. When 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 Figure 3 In the manufacturing apparatus of the SiC ingot 10 shown, during crystal growth, when the reflectivity of the inner quartz tube 40 measured by the reflectometer 60 changes, the suspension member 25 can be moved up and down to change the width of the gas discharge path 23. Thereby, the gas discharge amount from the gas discharge path 23 is made substantially constant.

[0106] For example, during crystal growth, when the reflectivity of the inner quartz tube 40 measured by the reflectometer 60 decreases, the gas discharge amount from the gas discharge path 23 decreases, so the width of the gas discharge path 23 is widened. For example, during crystal growth, when the reflectivity of the inner quartz tube 40 measured by the reflectometer 60 becomes higher, the gas discharge amount from the gas discharge path 23 increases, so the width of the gas discharge path 23 is narrowed.

[0107] In the manufacturing method of the SiC ingot 10 of the present embodiment, as described above, by changing Figure 3 the width of the gas discharge path 23 in the manufacturing apparatus shown, the gas discharge amount from the gas discharge path 23 can be controlled. Thereby, the temperature distribution and the flow of the sublimation gas in the film formation space A can be controlled, and the SiC ingot 10 of the present embodiment in which the angle θ1 formed by the facet 4 and the inner boundary 6 of the step flow growth region 5 and the crystal growth direction 8 is 56° or less can be manufactured.

[0108] (Other examples)

[0109] The SiC ingot 10 of the present embodiment can also be manufactured by the manufacturing method shown below. Figure 4 It is a cross-sectional view showing another example of the manufacturing apparatus used when manufacturing the SiC ingot of the present embodiment. Figure 4 The manufacturing apparatus of 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.

[0110] Figure 4 In the manufacturing apparatus for the SiC ingot 10 shown, instead of Figure 3 the inner quartz tube 40 in the manufacturing apparatus for the SiC ingot 10 shown, an evaluation substrate 71 is provided, and instead of the reflectivity measuring device 60, a weight measuring device 70 is provided. Figure 4 The structures of the crucible 20, the heat insulating material 30, and the quartz tube 50 in the manufacturing apparatus for the SiC ingot 10 shown are the same as Figure 3 those in the manufacturing apparatus for the SiC ingot 10 shown.

[0111] In Figure 4 the manufacturing apparatus for the SiC ingot 10 shown, the residual gas discharged from the gas discharge path 23 is blown onto the evaluation substrate 71. The residual gas blown onto the evaluation substrate 71 adheres to the surface of the evaluation substrate 71 and solidifies. The weight of the evaluation substrate 71 becomes heavier due to the solidified residual gas.

[0112] 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 acceleration of the weight increase of the evaluation substrate 71 is constant. In contrast, if the gas discharge amount from the gas discharge path 23 increases, the weight increase speed of the evaluation substrate 71 increases. Also, if the gas discharge amount from the gas discharge path 23 decreases, the weight increase speed of the evaluation substrate 71 decreases.

[0113] In Figure 4 the manufacturing apparatus for the SiC ingot 10 shown, the gas discharge amount from the gas discharge path 23 is evaluated based on the change in the weight increase speed of the evaluation substrate 71.

[0114] In the method for manufacturing the SiC ingot 10 using the Figure 4 manufacturing apparatus shown, similar to the case of using the Figure 3 manufacturing apparatus shown, by changing the width of the gas discharge path 23, the gas discharge amount from the gas discharge path 23 can be controlled. Thereby, the temperature distribution in the film formation space A and the flow of the sublimation gas can be controlled, and the SiC ingot 10 of the present embodiment in which the angle θ1 formed by the facet 4 and the inner boundary 6 of the step flow growth region 5 and the crystal growth direction 8 is 56° or less can be manufactured.

[0115] In the above manufacturing method, as an example of the method for evaluating the gas discharge amount from the gas discharge path 23, the case of using the change in the reflectivity of the inner quartz tube 40 or the change in the weight of the evaluation substrate 71 has been described, but the physical quantity used to evaluate the gas discharge amount from the gas discharge path 23 is not limited to reflectivity and weight.

[0116] Figure 1In the SiC ingot 10 of the present embodiment shown, the shape of the facet 4 is controlled such that the positional deviation between the planar coordinates of the facet 4 at the first end 1 and the planar coordinates of the facet 4 at the second end 2 is small enough. The SiC ingot 10 of the present embodiment can be processed by a known method to form a cylindrical SiC single crystal, that is, a SiC ingot.

[0117] Similar to the SiC ingot 10 of the present embodiment, the processed cylindrical SiC ingot has an angle θ1 of 56° or less between the facet 4 and the inner boundary 6 of the step flow growth region 5 and the crystal growth direction 8 in the XZ cut plane (the cut plane passing through the center and along the <11-20> direction). Therefore, when the SiC ingot 10 of the present embodiment is processed into a cylindrical SiC ingot, the positional deviation between the planar coordinates of the facet 4 at the first end 1 and the planar coordinates of the facet 4 at the second end 2 is small enough, which can reduce the number of changes in the laser output when cutting out the SiC substrate, and can easily and efficiently cut out the SiC substrate. The SiC ingot may have an orientation plane or notch for grasping the crystal axis direction.

[0118] <Method for manufacturing SiC substrate>

[0119] The method for manufacturing a SiC substrate according to the first embodiment includes: a step of manufacturing the SiC ingot 10 of the above embodiment by any of the above methods; a step of processing the SiC ingot 10 into a cylindrical shape; and a step of slicing the processed cylindrical SiC ingot.

[0120] As the step of processing the SiC ingot 10 into a cylindrical shape, a known method can be adopted. In addition, as the step of slicing the SiC ingot, for example, a method of generating cracks by laser processing the SiC ingot and cutting out the SiC substrate can be adopted.

[0121] In the present embodiment, for multiple SiC substrates cut out from the SiC ingot, similar to the SiC ingot 10 of the present embodiment, in the XZ cut plane (the cut plane passing through the center and along the <11-20> direction), the angle θ1 between the facet 4 and the inner boundary 6 of the step flow growth region 5 and the crystal growth direction 8 is 56° or less. In addition, when the angle θ1 between the inner boundary 6 and the Z direction (crystal growth direction) is 56° or less in any of the multiple SiC substrates cut out from the same SiC ingot, it can be said that the SiC ingot before cutting is equivalent to the SiC ingot of the present embodiment.

[0122] The method for manufacturing a SiC substrate according to 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.

[0123] The process for preparing the SiC ingot 10 may include obtaining the SiC ingot 10 of the above-described embodiment from another company. The SiC ingot 10 may also be a boule as long as it satisfies the requirements of the above-described embodiment.

[0124] The process 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.

[0125] <Evaluation method for SiC ingot>

[0126] The evaluation method for the SiC ingot 10 of the present embodiment includes: a process of fabricating the SiC ingot 10 of the present embodiment; a process of processing the SiC ingot 10 into a cylindrical shape; a process of slicing the cylindrically processed SiC ingot to obtain a plurality of evaluation SiC substrates; a process of measuring the positions of the facets 4 and the inner boundaries 6 of the step-flow growth regions 5 in each evaluation SiC substrate; a process of calculating the angle θ1 formed by the inner boundaries 6 of the facets 4 and the step-flow growth regions 5 and the crystal growth direction 8 in a cross-sectional plane passing through the center of the SiC ingot 10 and along the <11-20> direction based on the relationship between the position of the SiC ingot from which each evaluation SiC substrate is cut out and the position of the inner boundary 6 of each evaluation SiC substrate; and an evaluation process.

[0127] In the evaluation process, based on the angle θ1 formed by the inner boundary 6 of the SiC ingot 10 and the crystal growth direction 8, it is evaluated whether the SiC ingot 10 is fabricated under conditions suitable for fabricating a SiC ingot sliced by laser processing.

[0128] Specifically, the evaluation process is preferably the following process: when the angle θ1 formed with the crystal growth direction 8 is 56° or less, it is evaluated that the SiC ingot 10 is fabricated under conditions suitable for fabricating a SiC ingot sliced by laser processing; when the angle θ1 formed with the crystal growth direction 8 is greater than 56°, it is evaluated that the SiC ingot 10 is fabricated under conditions not suitable for fabricating a SiC ingot sliced by laser processing.

[0129] In addition, in the evaluation method for the SiC ingot 10 of the present embodiment, the positions of the inner boundaries 6 may be measured for a plurality of pre-fabricated evaluation SiC substrates respectively, and the angle θ1 formed by the inner boundary 6 and the crystal growth direction 8 may be calculated using the results, thereby evaluating the shape of the facets in other SiC ingots fabricated by the same manufacturing method as the SiC ingot 10. Therefore, according to the evaluation method for the SiC ingot 10 of the present embodiment, it is possible to evaluate with high precision whether the facets in other SiC ingots are in a controlled shape suitable for a SiC ingot sliced by laser processing.

[0130] 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 elements) of the present invention described in the claims.

[0131] Example

[0132] <Example 1>

[0133] Use Figure 3 Using the SiC ingot manufacturing apparatus shown, by adjusting the gas discharge amount from the gas discharge path 23, the temperature distribution and the flow of the sublimation gas in the film formation space A were controlled, and two SiC ingots with a diameter of 160 mm and a thickness of 32.6 mm were produced.

[0134] The SiC ingot of Example 1 was observed from above in the Z direction (crystal growth direction) visually. As a result, the SiC ingot of Example 1 had a step flow growth region and facets. In addition, one of the two SiC ingots of Example 1 was cut along the <11-20> direction passing through the center, and the inner boundary 6 of the facet 4 and the step flow growth region 5 in the XZ cut surface was visually confirmed, and the angle θ1 formed by the inner boundary 6 and the Z direction (crystal growth direction) was measured. As a result, θ1 was 27°.

[0135] In addition, another SiC ingot of Example 1 was processed into a cylindrical shape to form a SiC ingot with a diameter of 150 mm. Cracks were formed on the obtained SiC ingot by laser processing, and 75 SiC substrates with a thickness of 0.35 mm were cut out.

[0136] The laser processing was performed under the conditions of a scanning pitch of 200 μm, a feed speed of laser scanning of 200 mm / sec, a scanning number of 1 time, an acceleration / deceleration time of 0.1 second, and an inter-line movement time of 0.1 second. The acceleration / deceleration time refers to the time required for acceleration and 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 the laser scanning in the Y direction and the movement in the X direction.

[0137] By the above method, the time required to cut out 75 SiC substrates from the SiC ingot of Example 1 was 778 minutes. Therefore, the time required to cut out one SiC substrate was 10.4 minutes.

[0138] <Example 2>

[0139] The gas discharge amount from the gas discharge path 23 was adjusted to a value different from that of Example 1, and two SiC ingots were produced in the same manner as in Example 1 except for this.

[0140] The SiC ingot of Example 2 was observed from above visually in the Z direction (crystal growth direction). As a result, the SiC ingot of Example 2 had a step-flow growth region and facets. In addition, one of the two SiC ingots of Example 2 was cut along the <11-20> direction passing through the center, and the inner boundary 6 of the facets 4 and the step-flow growth region 5 in the XZ cut surface was visually confirmed, and the angle θ1 formed by the inner boundary 6 and the Z direction (crystal growth direction) was measured. As a result, θ1 was 45°.

[0141] In addition, another SiC ingot of Example 2 was processed into a cylindrical shape in the same manner as the SiC ingot of Example 1 to obtain a SiC ingot with a diameter of 150 mm. Cracks were formed on the obtained SiC ingot by laser processing in the same manner as in Example 1, and 75 SiC substrates with a thickness of 0.35 mm were cut out.

[0142] By the above method, the time required to cut out 75 SiC substrates from the SiC ingot of Example 2 was 833 minutes. Therefore, the time required to cut out one SiC substrate was 11.1 minutes.

[0143] <Comparative Example 1>

[0144] Except for not forming the gas discharge path 23, the same crucible as that used in Example 1 was used, and SiC ingots were crystallized and grown in a closed crucible to produce two SiC ingots with a diameter of 159 mm and a thickness of 28 mm.

[0145] The SiC ingot of Comparative Example 1 was observed from above visually in the Z direction (crystal growth direction). As a result, the SiC ingot of Comparative Example 1 had a step-flow growth region and facets. In addition, one of the two SiC ingots of Comparative Example 1 was cut along the <11-20> direction passing through the center, and the inner boundary 6 of the facets 4 and the step-flow growth region 5 in the XZ cut surface was visually confirmed, and the angle θ1 formed by the inner boundary 6 and the Z direction (crystal growth direction) was measured. As a result, θ1 was 62°.

[0146] In addition, another SiC ingot of Comparative Example 1 was processed into a cylindrical shape in the same manner as the SiC ingot 10 of Example 1 to obtain a SiC ingot with a diameter of 150 mm. Cracks were formed on the obtained SiC ingot by laser processing in the same manner as in Example 1, and 64 SiC substrates with a thickness of 0.35 mm were cut out.

[0147] By the above method, the time required to cut out 64 SiC substrates from the SiC ingot of Comparative Example 1 was 761 minutes. Therefore, the time required to cut out one SiC substrate was 11.9 minutes.

[0148] The time required to cut out one SiC substrate from the SiC ingots of Examples 1 and 2 is shorter than that of the SiC ingot of Comparative Example 1. The reason is that, in the SiC ingots of Examples 1 and 2, the number of times of laser output change when cutting out the SiC substrate from the SiC ingot is smaller than that of the SiC ingot of Comparative Example 1.

[0149] 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 the same evaluation was performed. 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.

[0150] That is, in the SiC ingots fabricated under the conditions of the present embodiment, the angle θ1 formed by the inner boundary 6 in the XZ cut surface and the Z direction (crystal growth direction) is 56° or less. In the SiC ingots fabricated under the conditions that do not satisfy the present embodiment, the angle θ1 is greater than 56°. In addition, the time required to cut out one SiC substrate is shorter in the SiC ingots fabricated under the conditions of the present embodiment than in the SiC ingots fabricated under the conditions that do not satisfy the present embodiment.

Claims

1. A SiC ingot, comprising a SiC single crystal grown from a first end inclined at an offset angle to a second end of a (0001) plane, and having a step flow growth region and a facet, In a cross section passing through the center and along the <11-20> direction, an angle formed by the facet and the inner boundary of the step flow growth region and the crystal growth direction is 56° or less.

2. The SiC ingot according to claim 1, The inner boundary extending from the first end to the second end is inclined in the [-1-120] direction at an angle greater than 0° and not more than 56° with respect to the thickness direction from the first end to the second end.

3. The SiC ingot according to claim 1, The diameter is 149mm or more.

4. The SiC ingot according to claim 1, The diameter is 199mm or more.

5. The SiC ingot according to claim 1, The maximum thickness between the first end and the second end in a direction perpendicular to the first end is greater than or equal to 10 mm.

6. The SiC ingot according to claim 1, The maximum thickness between the first end and the second end in a direction perpendicular to the first end is greater than or equal to 20 mm.

7. The SiC ingot according to claim 1, The maximum thickness between the first end and the second end in a direction perpendicular to the first end is 30 mm or more.

8. The SiC ingot according to claim 1, The maximum thickness between the first end and the second end in a direction perpendicular to the first end is 40 mm or more.

9. The SiC ingot according to claim 1, The maximum thickness between the first end and the second end in a direction perpendicular to the first end is 50 mm or more.

10. A method for manufacturing a SiC substrate, comprising: A process for producing a SiC ingot according to any one of claims 1 to 9; The step of processing the SiC ingot into a cylindrical shape; and a step of slicing the SiC ingot processed into a cylindrical shape.

11. A method for manufacturing a SiC substrate, comprising: A step of preparing the SiC ingot according to any one of claims 1 to 9; and The step of slicing the SiC ingot is as follows.

12. A method for evaluating a SiC ingot, comprising: Process for making SiC ingot; The step of processing the SiC ingot into a cylindrical shape; The step of slicing the SiC ingot processed into a cylindrical shape to obtain a plurality of SiC substrates for evaluation; a step of measuring the positions of the inner boundaries of the facets and the step flow growth region in each evaluation SiC substrate; A step of calculating an angle between the inner boundary of the facet and the step flow growth region and the crystal growth direction in a cut plane passing through the center of the SiC ingot and along the <11-20> direction based on a relationship between the position of each evaluation SiC substrate in the cut SiC ingot and the position of the inner boundary of each evaluation SiC substrate; and An evaluation step of evaluating whether the SiC ingot is produced under conditions suitable for producing a SiC ingot to be sliced ​​by laser processing, based on an angle formed by the inner boundary and the crystal growth direction.

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