SiC INGOT AND METHOD FOR MANUFACTURING SiC SUBSTRATE

Abstract

To provide a SiC ingot easily processed during laser processing.SOLUTION: A SiC ingot has a facet surrounded with the minimum area when setting a diameter to D and plan-viewed from a crystal growth direction. When setting the length of the first side of a virtual rectangle having a first side parallel to a <11-20>direction and a second side parallel to a <1-100>direction to Lx, Lx / D<0.3 is satisfied in a first end being an end in the crystal growth direction.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Silicon carbide (SiC) has a breakdown electric field one order of magnitude larger and a bandgap three times larger than silicon (Si). In addition, silicon carbide (SiC) has characteristics such as a thermal conductivity 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 operation devices, etc. For this reason, in recent years, SiC epitaxial wafers have been used for semiconductor devices as described above.

[0003] 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 out from a SiC ingot.

[0004] For example, as described in Patent Document 1, when manufacturing a SiC ingot, facets are formed on the SiC ingot. When growing the SiC ingot, a part of the crystal growth surface becomes parallel to the c-plane, and a plane parallel to the c-plane is exposed on the crystal growth surface. The plane parallel to the c-plane has a different crystal growth pattern from the other crystal growth surfaces that grow by step flow. The portion that has grown by step flow and the portion that has grown by a different pattern are facets.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, SiC ingots have been processed with lasers. For example, cracks are introduced into SiC ingots with lasers, and SiC substrates are cut out from the SiC ingots. 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 do not occur, and if the laser output is large, the roughness of the processed surface may increase. The facet has a lower resistance value than the portion grown by step flow. If there is a facet in the SiC ingot, it is necessary to change the laser output. There is a problem that the processing throughput decreases as the number of times of changing the laser output increases.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide an SiC ingot that is easy to process during laser processing and a method for manufacturing an SiC substrate using the SiC ingot.

Means for Solving the Problems

[0008] The present inventors have found that by controlling the shape of the facet, the opportunity to change the laser output can be reduced. In order to solve the above problems, the present invention provides the following means.

[0009] (1) The SiC ingot according to the first aspect has a facet. In this SiC ingot, when the diameter of the SiC ingot is D and viewed in a plan view from the crystal growth direction, the facet is surrounded by a minimum area, and when the length of the first side of the virtual rectangle having 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 end of the crystal growth direction, Lx / D < 0.3 is satisfied.

[0010] (2) The SiC ingot according to the aspect (1) above may satisfy 0.05 < Lx / D < 0.3 at the first end.

[0011] (3) The SiC ingot according to the aspect of (1) or (2) above may satisfy Lx / D ≤ 0.2 at the first end.

[0012] (4) The SiC ingot according to any one of the aspects of (1) to (3) above may satisfy Lx / D ≤ 0.1 at the first end.

[0013] (5) The SiC ingot according to any one of the aspects of (1) to (4) above may satisfy Lx / D < 0.3 at the second end on the side opposite to the first end.

[0014] (6) The SiC ingot according to any one of the aspects of (1) to (5) above may satisfy 0.05 < Lx / D < 0.3 at the second end.

[0015] (7) The SiC ingot according to any one of the aspects of (1) to (6) above may satisfy Lx / D < 0.3 on one cutting plane that intersects within a range of 90° ± 1° with respect to the crystal growth direction.

[0016] (8) The SiC ingot according to any one of the aspects of (1) to (7) above may satisfy Lx / D < 0.3 on two or more cutting planes that intersect within a range of 90° ± 1° with respect to the crystal growth direction.

[0017] (9) The SiC ingot according to any one of the aspects of (1) to (8) above may satisfy Lx / D < 0.3 on five or more cutting planes that intersect within a range of 90° ± 1° with respect to the crystal growth direction.

[0018] (10) The SiC ingot according to any one of the aspects of (1) to (9) above may satisfy Lx / D < 0.3 on any cutting plane that intersects within a range of 90° ± 1° with respect to the crystal growth direction.

[0019] (11) The SiC ingot according to any one of the aspects of (1) to (10) above may have a portion where the offset angle with respect to the {0001} plane is 3.5° or more and 4.5° or less.

[0020] (12) The SiC ingot according to any one of the above aspects (1) to (11) may have a height in the crystal growth direction of 20 mm or more.

[0021] (13) The SiC ingot according to any one of the above aspects (1) to (12) may have a diameter of 145 mm or more.

[0022] (14) The SiC ingot according to any one of the above aspects (1) to (12) may have a diameter of 195 mm or more.

[0023] (15) When the length of the second side of the virtual rectangle is defined as Ly, the SiC ingot according to any one of the above aspects (1) to (14) may satisfy 0.5 > Ly / D at the first end.

[0024] (16) When the length of the second side of the virtual rectangle is defined as Ly, the SiC ingot according to any one of the above aspects (1) to (15) may satisfy 0.5 > Ly / D on any cutting plane that intersects within a range of 90° ± 1° with the crystal growth direction.

[0025] (17) The method for manufacturing a SiC substrate according to the second aspect includes a step of producing a SiC ingot according to any one of the above aspects (1) to (16) and a step of slicing the SiC ingot. (18) The method for manufacturing a SiC substrate according to the third aspect includes a step of preparing a SiC ingot according to any one of the above aspects (1) to (16) and a step of slicing the SiC ingot.

Advantages of the Invention

[0026] The SiC ingot according to the above aspect is easy to process during laser processing. Also, the method for manufacturing a SiC substrate according to the above aspect is excellent in production efficiency.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0028] Hereinafter, the SiC ingot and the like according to this embodiment will be described in detail with appropriate reference to the drawings. The drawings used in the following description may show, for the sake of clarity, the characteristic parts enlarged for convenience, and the dimensional ratios of each component may be different from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and can be appropriately modified and implemented within the scope of not changing the gist (technical requirements).

[0029] In this specification, individual orientations are indicated by [], collective orientations by <>, individual planes by (), and collective planes by {}. Regarding negative indices, in crystallography, a "-" (bar) is attached above the number, but in this specification, a negative sign is attached before the number. Also, the notation "a ± b" indicates a range from "a - b" to "a + b".

[0030] First, the directions are defined. The crystal growth direction of the SiC ingot 10 is defined as the Z direction. The Z direction is the height direction of the cylindrical SiC ingot 10. One direction of the plane orthogonal to the Z direction is defined as the X direction. The X direction is, for example, the <11-20> direction. Also, in the plane orthogonal to the Z direction, the direction orthogonal to the X direction is defined as the Y direction. The Y direction is, for example, the <1-100> direction.

[0031] "SiC ingot" FIG. 1 is a perspective view of the SiC ingot 10 according to 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 that a SiC substrate can be cut out.

[0032] 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 still more 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 still more preferably 201 mm or less. The SiC ingot 10 may be, for example, one that can obtain a 6-inch substrate or one that can obtain an 8-inch substrate. The diameter D of the SiC ingot 10 substantially coincides with the diameter of the processed SiC substrate.

[0033] 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, still more preferably 50 mm or more, and particularly preferably 60 mm or more. The thickness T of the SiC ingot 10 may be 100 mm or more. The thicker the SiC ingot 10, the more SiC substrates can be obtained. Also, the thickness T of the SiC ingot 10 may be 300 mm or less.

[0034] 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 end in the crystal growth direction and is, for example, a (000-1) plane or a plane inclined by an offset angle from the (000-1) plane. The second end 2 is the end on the side opposite to the first end 1 and is, for example, a (0001) plane or a plane inclined by an offset angle from the (0001) plane. The first end 1 and the second end 2 are the bottom surface and the top surface 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.

[0035] FIG. 2 is a cross-sectional view of the SiC ingot 10 according to the present embodiment. The SiC ingot 10 has a facet 4 and a step-flow growth region 5.

[0036] The SiC ingot 10 grows crystals on a SiC seed crystal. In many cases, a seed crystal having an offset angle with respect to the {0001} plane is used to suppress the generation of polytypes. The offset angle is, for example, 3.5° or more and 4.5° or less, preferably 4°. By step-flow growth of SiC on the seed crystal, the generation of polytypes can be suppressed. Even when the SiC ingot grows by step-flow, a part of the crystal growth surface becomes 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 on this plane parallel to the (0001) plane, step-flow growth does not occur. The facet 4 is a region where crystals grow perpendicular to the (0001) plane. The step-flow growth region 5 is a region where crystals grow by step-flow. The step-flow growth region 5 has, for example, an offset angle with respect to the {0001} plane of 3.5° or more and 4.5° or less.

[0037] FIG. 3 is a plan view of a cut surface obtained by cutting the SiC ingot 10 according to the present embodiment in 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 flat 6 or a notch for grasping the direction of the crystal axis.

[0038] As shown in FIG. 3, in a plan view from the Z direction, the facet 4 and the step-flow growth region 5 have different colors and the boundary therebetween 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 observed visually as a region with a darker color tone than the step-flow growth region 5.

[0039] The boundary between the facet 4 and the step-flow growth region 5 can be determined visually, but it may also be determined by the following procedure. First, an image of the measurement cross-section is acquired. The image is acquired, for example, by double-side polishing the substrate and using a scanner. As the scanner, for example, a flatbed scanner manufactured by Canon can be used. The image may also be acquired using a digital camera. Next, the acquired image is converted into an HLS color space composed of hue, luminance, and saturation, and the luminance is obtained. Then, in the image converted into the luminance distribution, a circle with a radius of X pixels is drawn around an arbitrary pixel. If there is a pixel in this circle whose luminance difference from the central pixel is Y or more, the pixel at the center of the circle becomes a pixel candidate for the facet. If there is no pixel in this circle whose luminance difference from the central pixel is Y or more, the pixel at the center of the circle is not a pixel candidate for the 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 not being a pixel candidate for the facet. Then, the boundary between the pixel candidates for the facet and the pixels not being a pixel candidate for the facet is detected, and the inside of this region becomes the facet. Note that among the pixel candidates for the facet, a pixel that is an isolated area away from other pixel candidates for the facet can be determined not to be a pixel candidate for the facet. The radius X of the circle and the luminance difference Y are set according to the size of the image and the number of pixels. These settings are set to values such that the visual result and the determination result do not deviate significantly. For example, when using an image of 640 pixels × 480 pixels including a 150 mm wafer, the radius X is set to 9 pixels and the luminance difference Y is set to 4 W·sr -1 ·m -2 and.

[0040] Here, assume a virtual rectangle 7 that encloses the facet 4 with the minimum area. The virtual 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.

[0041] The length Lx of the first side 8 satisfies Lx / D < 0.3 in relation to the diameter D of the SiC ingot 10. It is preferable that Lx / D satisfies Lx / D ≦ 0.25, more preferably Lx / D ≦ 0.2, still more preferably Lx / D ≦ 0.15, and particularly preferably Lx / D ≦ 0.1. Also, Lx / D may 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. Also, it is more preferable that this relationship is satisfied at the second end 2 of the SiC ingot 10. Further, it is more preferable that the relationship of Lx / D is satisfied at a cut surface substantially orthogonal to the Z direction at one position of the SiC ingot 10 in the Z direction. It is more preferable that the relationship of Lx / D is satisfied at 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. It is more preferable that the relationship of Lx / D is satisfied at 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. It is more preferable that the relationship of Lx / D is satisfied at any 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.

[0042] When 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 irradiating while scanning the laser in the Y direction is repeated while moving in the X direction. If there is a facet 4 during the scanning of the laser in the Y direction, it is necessary to change the laser output in order to generate appropriate cracks. This is because the facet 4 and the step-flow growth region 5 have different resistance values. If the width of the facet 4 in the X direction is narrow, the width of the portion where it is necessary to change the laser output during the scanning of the laser in the Y direction becomes narrow. That is, when Lx / D < 0.3 is satisfied, the ratio of the portion where the laser scanning can be performed without changing the laser output is wide, and the SiC substrate can be cut out efficiently. Also, this tendency is more prominent as the value of Lx / D is smaller.

[0043] Also, FIG. 4 is a plan view of a cross-sectional surface obtained by cutting a SiC ingot according to a comparative example in a plane orthogonal to the Z direction. In the example shown in FIG. 4, 0.05 ≧ Lx / D. If the value of Lx / D is too small, as shown in FIG. 4, the facet 4 is curved and often becomes crescent-shaped. When the facet 4 becomes crescent-shaped, it may be necessary to change the laser output a plurality of times during one scan of the laser in the Y direction. In this case, since the number of times of changing the laser output for generating appropriate cracks increases, the throughput for obtaining the SiC substrate deteriorates.

[0044] For example, FIG. 5 is a plan view image of a SiC substrate cut out from a SiC ingot satisfying 0.05 ≧ Lx / D. As shown in FIG. 5, the curvature of the facet 4 with a small Lx / D value can be confirmed.

[0045] The length Lx of the first side 8 is preferably 30 mm or less, more preferably 25 mm or less, still more preferably 20 mm or less, still more preferably 15 mm or less, and still more preferably 10 mm or less.

[0046] Also, the length Ly of the second side 9 preferably satisfies Ly / D < 0.5, more preferably satisfies Ly / D ≤ 0.45, and even more 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. Also, this relationship is more preferably satisfied at the second end 2 of the SiC ingot 10, and even more preferably satisfied on 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. Also, this relationship is even more preferably satisfied on 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. Also, this relationship is even more preferably satisfied on 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. Also, this relationship is even more preferably satisfied on 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. Also, Ly / D may be greater than 0.01.

[0047] When the value of Ly / D is large, the facet 4 is likely to curve and become crescent-shaped. By making the planar shape of the facet 4 elliptical, the number of times of changing the laser output can be reduced.

[0048] "Manufacturing Method of SiC Ingot" Next, the manufacturing method of the SiC ingot 10 according to this embodiment will be described. FIG. 6 is a cross-sectional view of an example of the manufacturing apparatus of the SiC ingot 10 according to this embodiment. The manufacturing apparatus of the SiC ingot 10 includes a crucible 20, a heat insulating material 30, a liner quartz tube 40, a quartz tube 50, and a reflectance measuring device 60.

[0049] The crucible 20 is made of, for example, graphite. The crucible 20 has a housing portion 21 and a lid 22. A gas discharge passage 23 is formed between the housing portion 21 and the lid 22. The gas discharge passage 23 is located at at least one position on the outer surface of the crucible 20, and there may be a plurality of such positions. Further, the gas discharge passage 23 may be in a ring shape extending around the outer surface of the crucible 20 between the housing portion 21 and the lid 22. The housing portion 21 is supported and fixed by a support 24. The lid 22 is suspended by a suspension member 25 and can be moved up and down. The distance between the housing portion 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 passage 23 in the Z direction can be freely designed.

[0050] In the film formation space A inside the crucible 20, a seed crystal S and a SiC raw material M are arranged. The gas sublimated from the SiC raw material M recrystallizes on the surface of the seed crystal S, thereby causing crystal growth of the SiC ingot 10. The residual gas in the film formation space A is discharged from the crucible 20 to the outside through the gas discharge passage 23.

[0051] The atmospheric pressure during crystal growth in the film formation space A is set to be greater than 0.3 Torr and less than 10 Torr. If the pressure in the film formation space A is too low, dopant elements cannot be sufficiently incorporated into the crystal, and the resistivity of the SiC ingot 10 increases. The resistivity of the SiC ingot 10 is a parameter that affects laser processing. Also, if the pressure in the film formation space A is too high, sufficient sublimated gas cannot be generated from the SiC raw material M, and productivity decreases.

[0052] The bulk density of the graphite constituting the side surface of the crucible 20 is 3 more than 1.75 g / cm 3 and less than 2.00 g / cm. A part of the residual gas in the film formation space A permeates through the crucible 20 and exits to the outside. If the bulk density of the graphite constituting the crucible 20 is low, a large amount of residual gas is discharged from portions other than the gas discharge passage 23. The residual gas discharged from positions other than the gas discharge passage 23 deteriorates the heat insulating material 30. On the other hand, if the bulk density of the graphite constituting the crucible 20 is too high, the amount of heat conduction of the graphite becomes too large, and an appropriate temperature distribution cannot be achieved inside the crucible 20.

[0053] The volume G of the graphite that constitutes the crucible 20 is set to be 1.5 times or more and 4.0 times or less the volume F based on the diameter of the seed crystal S. The volume F corresponds to the inner product of the crucible 20. When the diameter of the seed crystal S is d, it is obtained by π×d 3 / 2. If the volume of the graphite is small, the residual gas passing through the crucible 20 increases, and the heat insulating material 30 deteriorates. If the volume of the graphite is too large, the thickness of the graphite becomes too thick, and an appropriate temperature distribution cannot be achieved inside the crucible 20.

[0054] The heat insulating material 30 covers the periphery of the crucible 20. The volume of the heat insulating material 30 is set to be more than 1 time 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 and 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 internal volume surrounded by the outer surface of the crucible. By setting the volume of the heat insulating material 30 within this range, an appropriate temperature distribution can be achieved inside the crucible 20. The temperature distribution inside the crucible 20 affects the formation of the facet 4.

[0055] Also, the outer diameter of the heat insulating material 30 is set to be 1.2 times or more and 1.5 times or less the outer diameter of the crucible 20. Since 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 by induction heating, its heat insulation performance is likely to deteriorate. By having the heat insulating material 30 with a sufficient width, it is possible to prevent the deterioration of the heat insulating material 30 and achieve an appropriate temperature distribution inside the crucible 20.

[0056] The liner quartz tube 40 is located around the heat insulating material 30. At least a part of the liner 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 liner quartz tube 40. The liner quartz tube 40 is supported by the support 41. By moving the support 41 up and down, the liner quartz tube 40 also moves up and down. During crystal growth, the liner quartz tube 40 is moved downward at a constant speed. The residual gas discharged from the gas discharge path 23 is blown onto the liner quartz tube 40 and solidifies and adheres to the inner wall of the liner quartz tube 40. The reflectivity of the liner quartz tube 40 increases as the residual gas solidifies.

[0057] The quartz tube 50 surrounds the crucible 20, the heat insulating material 30, and the liner quartz tube 40. The quartz tube 50 is covered with an upper lid 51 and a lower lid 52. The quartz tube 50 controls the internal atmosphere.

[0058] The reflectance measuring device 60 measures the reflectance of the portion of the liner quartz tube 40 irradiated with the residual gas. The reflectance of this portion increases as the gas discharge amount from the gas discharge path 23 increases. The reflectance measuring device 60 measures the gas discharge amount from the gas discharge path 23 by measuring the reflectance of the portion of the liner quartz tube 40 irradiated with the gas. During crystal growth, the liner quartz tube 40 moves downward at a constant speed. Therefore, the position irradiated with the gas in the liner quartz tube 40 is constantly changing. If the gas discharge amount from the gas discharge path 23 is constant, the reflectance of the portion of the liner quartz tube 40 where the reflectance is measured by the reflectance measuring device 60 will be constant.

[0059] When producing the desired SiC ingot 10, it is necessary to keep the flow of the sublimation gas in the film formation space A 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.

[0060] When the reflectance of the portion measured by the reflectance measuring device 60 changes in the manufacturing apparatus of the SiC ingot 10 according to this embodiment, the hanging member 25 is moved up and down to change the width of the gas discharge path 23. For example, when the reflectance of the portion measured by the reflectance measuring device 60 decreases, since the gas discharge amount from the gas discharge path 23 is small, the width of the gas discharge path 23 is widened. For example, when the reflectance of the portion measured by the reflectance measuring device 60 changes to a high value, since the gas discharge amount from the gas discharge path 23 is large, the width of the gas discharge path 23 is narrowed.

[0061] The manufacturing apparatus of the SiC ingot 10 according to this 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 as described above. In this way, by controlling the temperature distribution and the flow of the sublimation gas in the film formation space A, the SiC ingot according to this embodiment can be produced.

[0062] Further, FIG. 7 is a cross-sectional view of another example of the manufacturing apparatus for the SiC ingot 10 according to the present embodiment. The manufacturing apparatus for the SiC ingot 10 shown in FIG. 7 includes a crucible 20, a heat insulating material 30, a quartz tube 50, a weight measuring device 70, and an evaluation substrate 71. In the manufacturing apparatus for the SiC ingot 10 shown in FIG. 7, an evaluation substrate 71 is provided instead of the liner quartz tube 40, and a weight measuring device 70 is provided instead of the reflectance measuring device 60. The configurations of the crucible 20, the heat insulating material 30, and the quartz tube 50 are the same as those in FIG. 6.

[0063] In the manufacturing apparatus for the SiC ingot 10 shown in FIG. 7, 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 increases as the residual gas solidifies.

[0064] 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 rate of increase in the weight of the evaluation substrate 71 is constant. On the other hand, when the gas discharge amount from the gas discharge path 23 increases, the rate of increase in the weight of the evaluation substrate 71 increases, and when the gas discharge amount from the gas discharge path 23 decreases, the rate of increase in the weight of the evaluation substrate 71 decreases. The manufacturing apparatus for the SiC ingot 10 shown in FIG. 7 evaluates the gas discharge amount from the gas discharge path 23 based on the change in the rate of increase in the weight of the evaluation substrate 71.

[0065] The manufacturing apparatus for the SiC ingot 10 shown in FIG. 7 can control the flow of the sublimation gas in the film formation space A by changing the width of the gas discharge path 23 so that the gas discharge amount from the gas discharge path 23 becomes 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 according to the present embodiment can be produced.

[0066] Here, as an example of the method for evaluating the gas discharge amount from the gas discharge path 23, an example using the change in reflectance and the change in weight is shown, but the physical quantities for evaluating the gas discharge amount from the gas discharge path 23 are not limited to these.

[0067] As described above, for the SiC ingot 10 according to the present embodiment, the shape of the facet 4 is controlled. The SiC ingot 10 according to the present embodiment is controlled such that the number of times the scanning direction of the laser intersects with the facet 4 is reduced, and the number of times the laser output is changed during laser processing can be reduced. Therefore, when cutting out a SiC substrate using a laser, the SiC ingot 10 according to the present embodiment can reduce the number of times the laser output is changed, and can efficiently produce a SiC substrate.

[0068] "Method for manufacturing SiC substrate" The method for manufacturing a SiC substrate according to the first embodiment includes a step of manufacturing the SiC ingot 10 of the above-described embodiment by any of the above-described methods, and a step of slicing the SiC ingot 10. As the step of slicing the SiC ingot 10, for example, a method of forming a crack by processing the SiC ingot 10 with a laser to cut out the SiC substrate can be used. The SiC ingot 10 may be processed into a columnar shape before slicing the SiC ingot 10.

[0069] The SiC substrate cut out from the SiC ingot 10 according to the present embodiment is likely to satisfy Lx / D < 0.3. For example, if Lx / D < 0.3 is satisfied on any cut surface of the SiC ingot 10 orthogonal to the crystal growth direction, the SiC substrate cut out from this SiC ingot 10 satisfies Lx / D < 0.3. In other words, if a plurality of SiC substrates cut out 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 according to the present embodiment. For example, if all SiC substrates with a thickness of 0.5 mm cut out from the same SiC ingot satisfy Lx / D < 0.3, the SiC ingot before cutting has a thickness of 20 mm or more and can be said to correspond to the SiC ingot according to the present embodiment.

[0070] The manufacturing method of the SiC substrate according to the second embodiment includes a step of preparing the SiC ingot 10 of the above-described embodiment and a step of slicing the SiC ingot 10. The step of 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 be a boule as long as it satisfies the requirements of the above-described embodiment. The step of slicing the SiC ingot 10 is the same as that of the first embodiment. Also, the SiC ingot 10 may be processed into a cylindrical shape before slicing the SiC ingot 10.

[0071] 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 are possible within the scope of the gist (technical requirements) of the present invention described in the claims.

Example

[0072] 「Example 1」 Using the SiC ingot manufacturing apparatus shown in FIG. 6, a SiC ingot with a diameter of 150 mm was produced while controlling the temperature distribution and the flow of the sublimation gas in the film formation space A. The SiC ingot of Example 1 had a facet at the first end which is the end in the crystal growth direction. The length Lx of the first side of the virtual rectangle surrounding the facet with the minimum area was 15 mm. That is, the SiC ingot of Example 1 satisfied Lx / D = 0.1.

[0073] Next, the SiC ingot of Example 1 was processed by laser to cut out a SiC substrate. The laser scan pitch was set to 200 μm, the feed rate of the laser scan was 200 mm / sec, the number of scan 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 the opposite direction after scanning the laser in one direction. The inter-line movement time indicates the time related to the movement in the X direction in the process of repeating the laser scanning in the Y direction and the movement in the X direction. Also, in order to change the laser output when the laser crosses the boundary between the facet and the step-flow growth region, the 0.5-second scan was stopped.

[0074] The process time required to cut out one SiC substrate from the SiC ingot of Example 1 was 11.1 minutes.

[0075] "Example 2" A SiC ingot with a diameter of 150 mm was produced in the same manner as in Example 1, except that the pressure of the atmosphere in the film formation space A was adjusted to a value different from that in Example 1. The SiC ingot of Example 2 had a facet at the first end which is the end of the crystal growth direction. The length Lx of the first side of the virtual rectangle surrounding the facet with the minimum area was 36 mm. That is, in the SiC ingot of Example 2, Lx / D = 0.24.

[0076] Next, the SiC ingot of Example 2 was processed by laser to cut out a SiC substrate. The laser conditions for cutting out the SiC substrate were the same as those in Example 1. The process time required to cut out one SiC substrate from the SiC ingot of Example 2 was 12.9 minutes.

[0077] "Comparative Example 1" Without using the SiC ingot manufacturing apparatus shown in FIG. 6, a SiC ingot was grown in a sealed crucible to produce a SiC ingot with a diameter of 150 mm. The SiC ingot of Comparative Example 1 had a facet at the first end which was the end in the crystal growth direction. The length Lx of the first side of the virtual rectangle surrounding the facet with the minimum area was 60 mm. That is, the SiC ingot of Comparative Example 1 satisfied Lx / D = 0.4.

[0078] Next, the SiC ingot of Comparative Example 1 was laser processed to cut out a SiC substrate. The laser conditions when cutting out the SiC substrate were the same as those in Example 1.

[0079] The process time required to cut out one SiC substrate from the SiC ingot of Comparative Example 1 was 14.9 minutes.

[0080] The SiC ingots of Examples 1 and 2 required a shorter process time when cutting out the SiC substrate than the SiC ingot of Comparative Example 1.

[0081] In Examples 1 and 2 and Comparative Example 1, the results of the SiC ingots with a diameter of 150 mm after processing were shown. SiC ingots with a diameter of 200 mm after processing were also produced and the same evaluation was carried out. In the SiC ingots with a diameter of 200 mm after processing, the same evaluation results as those of the SiC ingots with a diameter of 150 mm after processing could be confirmed. That is, in the SiC ingots produced under the conditions of this embodiment, Lx / D < 0.3 was satisfied. In the SiC ingots produced under the conditions not satisfying this embodiment, Lx / D ≧ 0.3. Also, compared with the SiC ingots produced under the conditions not satisfying this embodiment, in the SiC ingots produced under the conditions of this embodiment, the time required to cut out one SiC substrate was shorter.

Explanation of Reference Numerals

[0082] 1 First end 2 Second end 3 Side surface 4 Facet 5 Step Flow Growth Region 6 Orientation Flat 7 Virtual Rectangle 8 First Side 9 Second Side 10 SiC Ingot 20 Crucible 21 Accommodation Section 22 Lid 23 Gas Discharge Path 24 Support 25 Suspension Member 30 Heat Insulation Material 40 Liner Quartz Tube 41 Support 50 Quartz Tube 51 Upper Lid 52 Lower Lid 60 Reflectance Meter 70 Weighing Instrument 71 Evaluation Substrate

Claims

1. having a facet, with a diameter of D, when viewed in plan view from the crystal growth direction, enclosing the facet with the minimum area, having a first side parallel to the <11-20> direction and a second side parallel to the <1-100> direction, when the length of the first side of the virtual rectangle is Lx, a SiC ingot satisfying Lx / D < 0.3 at a first end that is the end of the crystal growth direction.

2. The SiC ingot according to claim 1, satisfying 0.05 < Lx / D < 0.3 at the first end.

3. The SiC ingot according to claim 1, satisfying Lx / D ≤ 0.2 at the first end.

4. The SiC ingot according to claim 1, satisfying Lx / D ≤ 0.1 at the first end.

5. The SiC ingot according to claim 1, satisfying Lx / D < 0.3 at a second end opposite to the first end.

6. The SiC ingot according to claim 5, satisfying 0.05 < Lx / D < 0.3 at the second end.

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

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

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

10. The SiC ingot according to claim 1, satisfying Lx / D < 0.3 on any cut surface intersecting within a range of 90° ± 1° with the crystal growth direction.

11. The SiC ingot according to claim 1, having a portion where the offset angle with respect to the {0001} plane is 3.5° or more and 4.5° or less.

12. The SiC ingot according to claim 1, wherein the height in the crystal growth direction is 20 mm or more.

13. The SiC ingot according to claim 1, having a diameter of 145 mm or more.

14. The SiC ingot according to claim 1, having a diameter of 195 mm or more.

15. when the length of the second side of the virtual rectangle is Ly, The SiC ingot according to claim 1, satisfying 0.5 > Ly / D at the first end.

16. when the length of the second side of the virtual rectangle is Ly, The SiC ingot according to claim 1, wherein in any cleavage plane intersecting within the range of 90° ± 1° with respect to the crystal growth direction, 0.5 > Ly / D is satisfied.

17. A step of producing the SiC ingot according to any one of claims 1 to 16, and a step of slicing the SiC ingot, a method for manufacturing a SiC substrate.

18. A step of preparing the SiC ingot according to any one of claims 1 to 16, and a step of slicing the SiC ingot, a method for manufacturing a SiC substrate.

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