Sic ingot, sic substrate manufacturing method, and sic ingot evaluation method

Abstract

To provide an SiC ingot easy to be laser-processed.SOLUTION: This SiC ingot is made of an SiC single crystal inclined by an offset angle from a (0001) face and crystal-grown from a first end toward a second end, and has a step-flow growth region, and a facet. On a cross section passing through a center in a <11-20> direction, an angle θ1 formed by an inside boundary between the facet and the step flow growth region and a crystal growth direction is 56° or less.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Silicon carbide (SiC) has a 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 operation devices, etc. For this reason, in recent years, SiC epitaxial wafers have been increasingly 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. The SiC substrate is cut out from a SiC ingot. The SiC ingot is obtained by crystal growth of a SiC single crystal on a seed crystal. When a SiC single crystal is grown on a seed crystal, a facet and a step-flow growth region are formed.

[0004] Patent Document 1 describes a method for manufacturing a SiC single crystal. Patent Document 1 also describes that when 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 region is promoted and the area of the facet region becomes smaller.

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 a laser. For example, cracks are introduced into SiC ingots with a laser, and SiC substrates are cut out from the SiC ingots. The optimum value of the laser output when cutting out an SiC substrate using a laser varies depending on the resistance value of the SiC single crystal. If the laser output is small, sufficient cracks do not occur. Also, if the laser output is large, the SiC single crystal is damaged.

[0007] The facets of an SiC ingot have a lower resistance value compared to the step-flow growth region grown by step-flow growth. Therefore, when cutting out an SiC substrate from an SiC ingot, it is necessary to change the laser output at the boundary between the facet and the step-flow growth region. The more the number of times the laser output is changed in the process of cutting out the SiC substrate, the lower the productivity.

[0008] 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 laser-process and a method for manufacturing an SiC substrate using the SiC ingot.

Means for Solving the Problems

[0009] The inventors of the present invention focused on the shape of the facets of the SiC ingot and earnestly studied to reduce the number of times of changing the laser output when cutting out an SiC substrate from the SiC ingot by laser processing and improve the productivity. As a result, they found that an SiC ingot having facets controlled to a specific shape should be used, and the present invention was conceived. The present invention provides the following means.

[0010] [1] It is made of an SiC single crystal grown from a first end inclined by an offset angle from the (0001) plane toward a second end, and has a step-flow growth region and a facet. 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, a SiC ingot.

[0011] [2] The inner boundary extending from the first end to the second end is inclined at an angle of more 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, the SiC ingot according to [1].

[0012] [3] The diameter is 149 mm or more, the SiC ingot according to [1] or [2]. [4] The diameter is 199 mm or more, the SiC ingot according to [1] or [2]. [5] The maximum thickness in the direction perpendicular to the first end between the first end and the second end is 10 mm or more, the SiC ingot according to any one of [1] to [4].

[0013] [6] The maximum thickness in the direction perpendicular to the first end between the first end and the second end is 20 mm or more, the SiC ingot according to any one of [1] to [4]. [7] The maximum thickness in the direction perpendicular to the first end between the first end and the second end is 30 mm or more, the SiC ingot according to any one of [1] to [4]. [8] The maximum thickness in the direction perpendicular to the first end between the first end and the second end is 40 mm or more, the SiC ingot according to any one of [1] to [4]. [9] The maximum thickness in the direction perpendicular to the first end between the first end and the second end is 50 mm or more, the SiC ingot according to any one of [1] to [4].

[0014]

[10] A step of producing the SiC ingot according to any one of [1] to [9], A step of processing the SiC ingot into a columnar shape, A step of slicing the SiC ingot processed into a columnar shape, a method for manufacturing a SiC substrate. A step of preparing a SiC ingot according to any one of

[11] [1] to [9], and a step of slicing the SiC ingot, and a method for manufacturing a SiC substrate comprising the same.

[0015]

[12] A step of producing a SiC ingot, a step of processing the SiC ingot into a cylindrical shape, a step of slicing the cylindrically processed SiC ingot to obtain a plurality of evaluation SiC substrates, a step of measuring the position of the inner boundary between the facet and the step flow growth region in each evaluation SiC substrate, From the relationship between the position in the cut SiC ingot of each evaluation SiC substrate and the position of the inner boundary of each evaluation SiC substrate, the facet on the cut surface passing through the center of the SiC ingot and along the <11-20> direction and the step flow growth region A step of calculating an angle formed by the inner boundary and the crystal growth direction, An evaluation step of evaluating whether or not the SiC ingot is produced under conditions suitable for producing a SiC ingot sliced by laser processing based on the angle formed by the inner boundary and the crystal growth direction. Evaluation method of SiC ingot.

Effect of the Invention

[0016] The SiC ingot of this embodiment is composed of a SiC single crystal grown from a first end offset by an offset angle from the (0001) plane toward a second end, and in a cut surface passing through the center and along the <11-20> direction, the facet and the step flow growth region The angle formed by the inner boundary and the crystal growth direction is 56° or less. For this reason, the SiC ingot of this embodiment can reduce the number of times of changing the laser output when cutting out a SiC substrate by processing into a cylindrical shape and cutting it out by laser processing, and the SiC substrate can be cut out easily and efficiently.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0018] Hereinafter, the manufacturing method of the SiC ingot and the SiC substrate according to this embodiment will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show enlarged parts that are characteristic for the sake of clarity of the features of this embodiment, 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 it can be appropriately changed and implemented without changing the gist (technical requirements).

[0019] In this specification, individual orientations are indicated by [], collective orientations by <>, individual planes by (), and collective planes by {}. Regarding negative indices, in crystallography, "-" (bar) is to be attached above the number, but in this specification, a negative sign is attached before the number.

[0020] First, define the directions. Let the crystal growth direction of the SiC ingot 10 be the Z direction. The Z direction is the height direction of the substantially cylindrical SiC ingot 10. Let one direction of the plane orthogonal to the Z direction be the X direction. The X direction is, for example, the <11-20> direction. For example, let the +X direction be the [11-20] direction and the -X direction be the [-1-120] direction. Also, on the plane orthogonal to the Z direction, let the direction orthogonal to the X direction be the Y direction. The Y direction is, for example, the <1-100> direction.

[0021] "SiC ingot" FIG. 1 is a cross-sectional view of the SiC ingot 10 according to the present embodiment. FIG. 2 is a plan view of the SiC ingot 10 according to the present embodiment shown in FIG. 1 as viewed from the Z direction. The SiC ingot 10 has a substantially cylindrical shape and is a single crystal of SiC that has grown from the first end 1 to the second end 2 shown in FIG. 1. The SiC ingot 10 may be in the state after being processed into a cylindrical shape or before being processed into a cylindrical shape. The second end 2 is the end 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 cylindrical shape with a constant diameter.

[0022] The first end 1 is a surface inclined by an offset angle from the (0001) plane (Si plane). The second end 2 is a surface inclined by an offset angle from the (000-1) plane (C plane). The second end 2 faces 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. Note that the offset angle of the SiC ingot is not limited to this example.

[0023] 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, still more preferably 151 mm or more, and may 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 be, for example, 230 mm or less, preferably 220 mm or less, more preferably 205 mm or less, and still more preferably 201 mm or less.

[0024] 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 obtainable from the SiC ingot 10. As shown in FIG. 1, for example, when the SiC ingot 10 has a shape that expands in diameter 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 a cylindrical shape with a constant diameter, the diameter of any cross-section obtained by cutting the SiC ingot 10 with a plane orthogonal to the Z direction corresponds to the diameter D of the SiC ingot 10. The SiC ingot 10 may be, for example, one capable of obtaining a 6-inch substrate or one capable of obtaining an 8-inch substrate.

[0025] 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, still more preferably 40 mm or more, even more preferably 50 mm or more, and particularly preferably 60 mm or more. The thickness of the SiC ingot 10 may be 100 mm or more. The thicker the thickness of the SiC ingot 10, the more SiC substrates can be obtained, which is preferable. Also, the thickness of the SiC ingot 10 is, for example, 300 mm or less.

[0026] The SiC ingot 10 has a facet 4 and a step-flow growth region 5. The SiC ingot 10 is composed of a SiC seed crystal and a crystal growth portion that has grown on the SiC seed crystal. As the SiC seed crystal, one having an offset angle with respect to the {0001} plane is used. This is because by growing a SiC single crystal on the SiC seed crystal by step-flow growth, the generation of crystals of different polymorphs can be suppressed. The offset 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°.

[0027] Even when a SiC single crystal is grown by step-flow on a SiC seed crystal, during the growth of the SiC single crystal, 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. On the plane parallel to the (0001) plane, since crystals grow perpendicular to the (0001) plane, step-flow growth does not occur. The facet 4 of the SiC ingot 10 is a region where crystals have grown perpendicular to the (0001) plane. The facet 4 is a region having a substantially circular shape when viewed from the Z direction as shown in FIG. 2. The step-flow growth region 5 is a region where a SiC single crystal has grown by step-flow on the SiC seed crystal. The step-flow growth region 5 is formed so as to surround the facet 4 as shown in FIG. 2. 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°.

[0028] The facet 4 and the step-flow growth region 5 have different colors when the SiC ingot 10 is viewed in plan from the Z direction (crystal growth direction). This is because the crystal growth modes are different between the facet 4 and the step-flow growth region 5. The facet 4 is observed visually as a region having a darker color than the step-flow growth region 5. Therefore, the boundary between the facet 4 and the step-flow growth region 5 can be confirmed visually.

[0029] The boundary between the facet 4 and the step-flow growth region 5 when the SiC ingot 10 is viewed in plan from the Z direction can be judged visually, but it may also be judged by the following procedure. First, an image when the SiC ingot 10 is viewed in plan from the Z direction is acquired. The image is acquired, for example, 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.

[0030] Next, the acquired image is converted into the HLS color space consisting of hue, luminance, and saturation, and the luminance is obtained. Then, in the image converted to the luminance distribution, a circle with a radius of X pixels is drawn centered on an arbitrary pixel. If there is a pixel within 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 a facet. If there is no pixel within 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 a facet. Next, the same process is performed on all the pixels of the image, and each pixel is classified as a pixel candidate for a facet or a pixel not being a facet candidate. Then, the boundary between the pixel candidates for a facet and the pixels not being a facet candidate is detected, and the interior of this region can be defined as a facet. Among the pixel candidates for a facet, a pixel that is an outlier away from other pixel candidates for a facet can be determined not to be a facet candidate. 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 diameter wafer obtained from a SiC ingot, the radius X is set to 9 pixels and the luminance difference Y is set to 4 W·sr -1 ·m -2 and.

[0031] Also, in the XZ cross-section of the SiC ingot 10, the boundary between the facet 4 and the step-flow growth region 5 can be visually determined. Hereinafter, among the boundaries between the facet 4 and the step-flow growth region 5, the boundary located on the central side of the SiC ingot 10 in the XZ cross-section of the SiC ingot 10 is referred to as the inner boundary 6, and the boundary outside the inner boundary 6 is referred to as the outer boundary 7. In the SiC ingot 10 of the present embodiment shown in FIG. 1, the inner boundary 6 and the outer boundary 7 are straight lines inclined in the -X direction with respect to the Z direction (the crystal growth direction indicated by reference numeral 8 in FIG. 1).

[0032] As shown in FIG. 1, 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 facet 4 penetrates deeper into the SiC ingot 10 as it approaches the second end 2 from the first end 1. 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.

[0033] 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 facet 4 inside can only be estimated. Since the facet 4 is a region where the amount of dopant elements such as nitrogen incorporated is larger than that in the step-flow growth region 5, the resistance value is low and the light transmittance is low. Therefore, when the SiC ingot 10 is processed into a cylindrical shape and laser processed, it is necessary to set different laser output conditions for the facet 4 and the step-flow growth region 5. For example, if there is a facet 4 at a position in the SiC ingot 10 where the facet 4 is estimated not to exist, estimated from 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 problems occurring is high.

[0034] In contrast, for the SiC ingot 10 of the present embodiment, in the XZ cut surface (a cut surface passing through the center and along the <11-20> direction), the angle θ1 formed by the inner boundary 6 between the facet 4 and the step flow growth region 5 and the crystal growth direction 8 is 56° or less. Therefore, the displacement of 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 sufficiently small. Thus, when the SiC ingot 10 is processed into a cylindrical shape and laser processed, the processing stability 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, even more preferably 40° or less, still more preferably 35° or less, and even more 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 the cylindrically processed SiC ingot is laser processed, which is preferable. Also, 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 is preferable.

[0035] The inner boundary 6 extending from the first end 1 toward the second end 2 preferably has an angle of more than 0° and 56° or less with respect to the [-1-120] direction in the thickness direction from the first end 1 toward the second end 2. In other words, it is preferable that the inner boundary 6 is inclined in the -X direction with respect to the Z direction (the crystal growth direction indicated by reference numeral 8 in FIG. 1). This is because it can be estimated that the facet 4 does not exist in the region within the SiC ingot 10 that is inside the planar coordinates of the facet 4 at the second end 2 from the planar coordinates of the facet 4 at the second end 2. Thus, when the SiC ingot 10 is processed into a cylindrical shape and laser processed, the processing stability becomes even higher. The angle of the inner boundary 6 with respect to the [-1-120] direction in the thickness direction from the first end 1 toward the second end 2 is preferably 50° or less, more preferably 45° or less, even more preferably 40° or less, still more preferably 35° or less, and even more preferably 30° or less.

[0036] In the SiC ingot 10 of this 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 cut surface 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 vary depending on 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 treated 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 five different positions in the Z direction.

[0037] In the SiC ingot 10 of this embodiment, as shown in FIG. 1, it is preferable that the distance between the inner boundary 6 and the outer boundary 7 in the XZ cut surface becomes wider as it approaches 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 polymorphs can be suppressed, and the SiC single crystal can be grown more stably. Further, this is because it can be estimated that there is no facet 4 in the region within the SiC ingot 10 that is wider than the planar coordinates of the facet 4 at the second end 2 from the planar coordinates of the facet 4 at the second end 2.

[0038] "Method for manufacturing SiC ingot" Next, the manufacturing method of the SiC ingot 10 according to this embodiment will be described with examples. FIG. 3 is a cross-sectional view showing an example of a manufacturing apparatus used when manufacturing the SiC ingot 10 according to this embodiment. The manufacturing apparatus for the SiC ingot 10 shown in FIG. 3 includes a crucible 20, a heat insulating material 30, a liner quartz tube 40, a quartz tube 50, and a reflectance measuring device 60.

[0039] 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 provided at at least one location on the outer surface of the crucible 20, and may be provided at a plurality of locations. The gas discharge passage 23 may be provided 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 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.

[0040] In the film formation space A in 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, and thus a SiC single crystal serving as a crystal growth portion of the SiC ingot 10 grows. The residual gas in the film formation space A is discharged from the gas discharge passage 23 to the outside of the crucible 20.

[0041] The atmospheric pressure during crystal growth in the film formation space A is set to be more than 0.3 Torr and less than 10 Torr. If the pressure in the film formation space A is too low, dopant elements such as nitrogen cannot be sufficiently supplied 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 is not generated from the SiC raw material M, and the productivity decreases.

[0042] The bulk density of the graphite constituting the side surface of the crucible 20 is 1.75 g / cm 3 more than 2.00 g / cm 3is less than. A part of the residual gas in the film formation space A passes 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 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 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 heat conduction amount of the graphite becomes too high, and an appropriate temperature distribution cannot be achieved inside the crucible 20.

[0043] The volume G of the graphite constituting the crucible 20 shall be 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 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 G of the graphite constituting the crucible 20 is small, the residual gas passing through the crucible 20 increases, and the heat insulating material 30 deteriorates. 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 achieved inside the crucible 20.

[0044] The heat insulating material 30 is substantially cylindrical and is arranged to cover the periphery of the crucible 20. The volume of the heat insulating material 30 shall 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 20. By setting the volume of the heat insulating material 30 within the above 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.

[0045] The outer diameter of the heat insulating material 30 shall 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 setting the outer shape of the heat insulating material 30 within the above range, it is possible to prevent the deterioration of the heat insulating material 30 and achieve an appropriate temperature distribution inside the crucible 20.

[0046] The liner quartz tube 40 is disposed 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 blown onto the liner quartz tube 40, adheres to the inner wall of the liner quartz tube 40, and solidifies. The reflectivity of the liner quartz tube 40 increases due to the adhesion of the solidified residual gas. The liner quartz tube 40 is supported by a support 41. When the support 41 moves 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.

[0047] 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 by an upper lid 51 and a lower lid 52. The quartz tube 50 makes it easier to control the atmosphere in the film formation space A.

[0048] The reflectivity measuring device 60 measures the reflectivity of the portion of the liner quartz tube 40 irradiated with the residual gas discharged from the gas discharge path 23. The reflectivity of this portion increases as the gas discharge amount from the gas discharge path 23 increases. In the manufacturing apparatus for the SiC ingot 10 shown in FIG. 3, the gas discharge amount from the gas discharge path 23 is evaluated based on the change in the reflectivity of the liner quartz tube 40.

[0049] During crystal growth, the liner quartz tube 40 moves downward at a constant speed by the support 41. Therefore, the position of the liner quartz tube 40 irradiated with the residual gas always changes. If the gas discharge amount from the gas discharge path 23 is constant, the reflectivity of the portion of the liner quartz tube 40 whose reflectivity is measured by the reflectivity measuring device 60 is constant.

[0050] In order to manufacture the SiC ingot 10 in which the angle θ1 formed between 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, 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. In the manufacturing apparatus of the SiC ingot 10 shown in FIG. 3, during crystal growth, if the reflectance of the liner quartz tube 40 measured by the reflectance measuring device 60 changes, the hanging member 25 can be moved up and down to change the width of the gas discharge path 23. By doing this, the gas discharge amount from the gas discharge path 23 can be made substantially constant.

[0051] For example, during crystal growth, if the reflectance of the liner quartz tube 40 measured by the reflectance measuring device 60 decreases, since the gas discharge amount from the gas discharge path 23 decreases, the width of the gas discharge path 23 is widened. For example, during crystal growth, if the reflectance of the liner quartz tube 40 measured by the reflectance measuring device 60 changes to a high value, since the gas discharge amount from the gas discharge path 23 increases, the width of the gas discharge path 23 is narrowed.

[0052] In the manufacturing method of the SiC ingot 10 of the present embodiment, as described above, by changing the width of the gas discharge path 23 in the manufacturing apparatus shown in FIG. 3, the gas discharge amount from the gas discharge path 23 can be controlled. By this, the temperature distribution and the flow of the sublimation gas in the film formation space A can be controlled, and the SiC ingot 10 according to the present embodiment in which the angle θ1 formed by the inner boundary 6 between the facet 4 and the step flow growth region 5 and the crystal growth direction 8 is 56° or less can be manufactured.

[0053] (Another example) The SiC ingot 10 according to the present embodiment may be manufactured using the manufacturing method shown below. FIG. 4 is a cross-sectional view showing another example of the manufacturing apparatus used when manufacturing the SiC ingot according to the present embodiment. The manufacturing apparatus of the SiC ingot 10 shown in FIG. 4 includes a crucible 20, a heat insulating material 30, a quartz tube 50, a weight measuring device 70, and an evaluation substrate 71.

[0054] The manufacturing apparatus for the SiC ingot 10 shown in FIG. 4 is provided with an evaluation substrate 71 instead of the liner quartz tube 40 in the manufacturing apparatus for the SiC ingot 10 shown in FIG. 3, 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 in the manufacturing apparatus for the SiC ingot 10 shown in FIG. 4 are the same as those of the manufacturing apparatus for the SiC ingot 10 shown in FIG. 3.

[0055] In the manufacturing apparatus for the SiC ingot 10 shown in FIG. 4, the residual gas discharged from the gas discharge path 23 is sprayed onto the evaluation substrate 71. The residual gas sprayed onto the evaluation substrate 71 adheres to the surface of the evaluation substrate 71 and solidifies. The weight of the evaluation substrate 71 increases due to the solidified residual gas.

[0056] 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. On the contrary, when the gas discharge amount from the gas discharge path 23 increases, the acceleration of the weight increase of the evaluation substrate 71 increases. Also, when the gas discharge amount from the gas discharge path 23 decreases, the acceleration of the weight increase of the evaluation substrate 71 decreases. In the manufacturing apparatus for the SiC ingot 10 shown in FIG. 4, the gas discharge amount from the gas discharge path 23 is evaluated based on the change in the acceleration of the weight increase of the evaluation substrate 71.

[0057] Also, in the method for manufacturing the SiC ingot 10 using the manufacturing apparatus shown in FIG. 4, similar to the case of using the manufacturing apparatus shown in FIG. 3, by changing the width of the gas discharge path 23, the gas discharge amount from the gas discharge path 23 can be controlled. As a result, the temperature distribution and the flow of the sublimation gas in the film formation space A can be controlled, and the SiC ingot 10 according to the present embodiment in which the angle θ1 formed between 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 can be manufactured.

[0058] In the manufacturing method described above, as an example of a method for evaluating the gas discharge amount from the gas discharge path 23, the case of using the change in reflectance of the liner quartz tube 40 or the change in weight of the evaluation substrate 71 has been described as an example. However, the physical quantity for evaluating the gas discharge amount from the gas discharge path 23 is not limited to reflectance and weight.

[0059] The SiC ingot 10 of the present embodiment shown in FIG. 1 has a shape of the facet 4 controlled so that the displacement of 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 sufficiently small. The SiC ingot 10 of the present embodiment can be processed by a known method to obtain a SiC ingot that is a single crystal of columnar SiC.

[0060] The SiC ingot processed into a columnar shape, similar to the SiC ingot 10 of the present embodiment, has an angle θ1 formed between the inner boundary 6 of the facet 4 and the crystal growth direction 8 of 56° or less in the XZ cut surface (the cut surface passing through the center and along the <11-20> direction). For this reason, the SiC ingot obtained by processing the SiC ingot 10 of the present embodiment into a columnar shape has a sufficiently small displacement 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. The number of changes in the laser output when cutting out the SiC substrate can be reduced, and the SiC substrate can be cut out easily and efficiently. The SiC ingot may have an orientation flat or notch for grasping the direction of the crystal axis.

[0061] "Method for manufacturing SiC substrate" The method for manufacturing a SiC substrate according to the first embodiment includes a step of producing the SiC ingot 10 of the above-described embodiment by any of the above-described methods, a step of processing the SiC ingot 10 into a columnar shape, and a step of slicing the SiC ingot processed into a columnar shape. As a process of processing the SiC ingot 10 into a columnar shape, a known method can be used. Further, as a process of slicing the SiC ingot, for example, a method of making a crack by processing the SiC ingot with a laser and cutting out the SiC substrate can be used.

[0062] In this embodiment, each of the plurality of SiC substrates cut out from the SiC ingot, similar to the SiC ingot 10 of this embodiment, has an angle θ1 formed between the inner boundary 6 of the facet 4 and the step-flow growth region 5 and the crystal growth direction 8 of 56° or less on the XZ cut surface (the cut surface passing through the center and along the <11-20> direction). Also, when the angle θ1 formed between the inner boundary 6 and the Z direction (crystal growth direction) of each of the plurality of SiC substrates cut out from the same SiC ingot is 56° or less, it can be said that the SiC ingot before cutting corresponds to the SiC ingot according to this embodiment.

[0063] The method for manufacturing a 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, and the SiC ingot may be a boule as long as it satisfies the requirements of the above-described embodiment. The step of slicing the SiC ingot is the same as in the first embodiment. Also, the SiC ingot 10 may be processed into a columnar shape before slicing the SiC ingot.

[0064] "Evaluation Method for SiC Ingot" The evaluation method of the SiC ingot 10 of this embodiment includes the steps of manufacturing the SiC ingot 10 of this embodiment described above, processing the SiC ingot 10 into a cylindrical shape, slicing the cylindrically processed SiC ingot to obtain a plurality of SiC substrates for evaluation, measuring the position of the inner boundary 6 between the facet 4 and the step flow growth region 5 in each SiC substrate for evaluation, and calculating the angle θ1 formed by the inner boundary 6 between the facet 4 and the step flow growth region 5 and the crystal growth direction 8 on the cutting plane passing through the center of the SiC ingot 10 and along the <11-20> direction from the relationship between the position in the cut SiC ingot of each SiC substrate for evaluation and the position of the inner boundary 6 of each SiC substrate for evaluation, and an evaluation step.

[0065] In the evaluation step, it is evaluated whether the SiC ingot 10 is manufactured under conditions suitable for manufacturing a SiC ingot sliced by laser processing based on the angle θ1 formed by the above-described inner boundary 6 and the crystal growth direction 8 of the SiC ingot 10. Specifically, in the evaluation step, when the angle θ1 formed with the crystal growth direction 8 is 56° or less, it is evaluated that the SiC ingot 10 is manufactured under conditions suitable for manufacturing a SiC ingot sliced by laser processing, and when the angle θ1 formed with the crystal growth direction 8 exceeds 56°, it is preferably a step of evaluating that the SiC ingot 10 is manufactured under conditions not suitable for manufacturing a SiC ingot sliced by laser processing.

[0066] In addition, in the method for evaluating the SiC ingot 10 of the present embodiment, the positions of the inner boundaries 6 are measured for each of a plurality of prepared evaluation SiC substrates, and by using the results, the angle θ1 formed between the inner boundary 6 and the crystal growth direction 8 is calculated, and thereby, the shape of the faceted surface in other SiC ingots manufactured by the same manufacturing method as the SiC ingot 10 may be evaluated. Therefore, according to the method for evaluating the SiC ingot 10 of the present embodiment, it is possible to highly accurately evaluate whether the faceted surface in other SiC ingots has a controlled shape suitable for the SiC ingot sliced by laser processing.

[0067] 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

[0068] 「Example 1」 Using the SiC ingot manufacturing apparatus shown in FIG. 3, by adjusting the gas discharge amount from the gas discharge path 23, while controlling the temperature distribution and the flow of the sublimation gas in the film formation space A, two SiC ingots having a diameter of 160 mm and a thickness of 32.6 mm were manufactured.

[0069] The SiC ingot of Example 1 was visually observed in a plan view from the Z direction (crystal growth direction). As a result, the SiC ingot of Example 1 had a step flow growth region and a faceted surface. Further, 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 between the faceted surface 4 and the step flow growth region 5 in the XZ cut surface was visually confirmed, and the angle θ1 formed between the inner boundary 6 and the Z direction (crystal growth direction) was measured. As a result, θ1 was 27°.

[0070] Further, the SiC ingot 10 of Example 1 was processed into a columnar shape to obtain a SiC ingot with a diameter of 150 mm. Cracks were introduced into the obtained SiC ingot by laser processing, and 75 SiC substrates with a thickness of 0.35 mm were cut out.

[0071] The laser processing was performed with a scan pitch of 200 μm, a feed rate of laser scanning of 200 mm / sec, the number of scan times of 1 time, an acceleration / deceleration time of 0.1 second, and a line-to-line movement time of 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 line-to-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.

[0072] The time required to cut out 75 SiC substrates from the SiC ingot of Example 1 by the above method was 778 minutes. Therefore, the time required to cut out one SiC substrate was 10.4 minutes.

[0073] "Example 2" Two SiC ingots were produced in the same manner as in Example 1, except that the gas discharge amount from the gas discharge path 23 was adjusted to a value different from that in Example 1.

[0074] The SiC ingot of Example 2 was visually observed in a plan view from the Z direction (crystal growth direction). As a result, the SiC ingot of Example 2 had a step-flow growth region and a facet. Further, 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 between 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 45°.

[0075] Also, 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 introduced into 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.

[0076] 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.

[0077] "Comparative Example 1" The same crucible as that used in Example 1 was used except that the gas discharge path 23 was not formed, and SiC ingots were grown in a sealed crucible to produce two SiC ingots with a diameter of 159 mm and a thickness of 28 mm.

[0078] The SiC ingot of Comparative Example 1 was visually observed in a plan view from the Z direction (crystal growth direction). As a result, the SiC ingot of Comparative Example 1 had a step flow growth region and a facet. Also, 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 between the facet 4 and the step flow growth region 5 on the XZ cut surface was visually confirmed, and the angle θ1 formed between the inner boundary 6 and the Z direction (crystal growth direction) was measured. As a result, θ1 was 62°.

[0079] Also, 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 introduced into 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.

[0080] 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.

[0081] For the SiC ingots of Examples 1 and 2, the time required to cut out one SiC substrate was 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 changing the laser output when cutting out the SiC substrate from the SiC ingot was less than that of the SiC ingot of Comparative Example 1.

[0082] In Examples 1 and 2 and Comparative Example 1, the results of SiC ingots with a processed diameter of 150 mm were 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 confirmed. That is, in the SiC ingot fabricated under the conditions of the present embodiment, the angle θ1 formed between the inner boundary 6 on the XZ cut surface and the Z direction (crystal growth direction) was 56° or less. In the SiC ingot fabricated under the conditions not satisfying the present embodiment, the angle θ1 was more than 56°. Also, compared with the SiC ingot fabricated under the conditions not satisfying the present embodiment, in the SiC ingot fabricated under the conditions of the present embodiment, the time required to cut out one SiC substrate was shorter.

Explanation of Reference Numerals

[0083] 1 First end 2 Second end 3 Side wall 3 4 Facet 5 Step flow growth region 10 SiC ingot 20 Crucible 21 Accommodation part 22 Lid 23 Gas discharge path 24 Support 25 Suspension member 30 Thermal insulation material 40 Liner quartz tube 41 Support 50 Quartz tube 51 Upper cover 52 Lower cover 60 Reflectance measuring instrument 70 Weighing instrument 71 Evaluation substrate

Claims

1. (0001)It is made of a SiC single crystal grown from the first end inclined by an offset angle from the (0001) plane toward the second end, and has a step flow growth region and a facet. A SiC ingot, wherein, on a cut surface 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.

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

3. The SiC ingot according to claim 1, having a diameter of 149 mm or more.

4. The SiC ingot according to claim 1, having a diameter of 199 mm or more.

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

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

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

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

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

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

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

12. A step of manufacturing a SiC ingot; a step of processing the SiC ingot into a columnar shape; and a step of slicing the SiC ingot processed into a columnar shape to obtain a plurality of evaluation SiC substrates. Measuring the position of the inner boundary between the facet and the step-flow growth region in each SiC substrate for evaluation; Calculating the angle formed between the inner boundary of the facet and the step-flow growth region and the crystal growth direction in a cut surface passing through the center of the SiC ingot and along the <11-20> direction from the relationship between the position in the SiC ingot of the cut-out SiC substrate for each evaluation and the position of the inner boundary of the SiC substrate for each evaluation; An evaluation method for a SiC ingot, comprising an evaluation step of evaluating whether the SiC ingot is produced under conditions suitable for producing a SiC ingot sliced by laser processing based on the angle formed between the inner boundary and the crystal growth direction.

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