Silicon carbide ingot manufacturing method, and silicon carbide substrate manufacturing method

Abstract

To provide a silicon carbide ingot manufacturing method capable of restraining cracks on a silicon carbide ingot.SOLUTION: A silicon carbide ingot manufacturing method includes the following steps. A silicon carbide single crystal having a poly-type of 4H is prepared. The silicon carbide single crystal has a first end face, a second end face, and an outer peripheral face. The second end face is opposite to the first end face. The outer peripheral face is communicated with the first and second end faces. The silicon carbide single crystal is ground on at least one of the first and second end faces. The silicon carbide single crystal is ground on the outer peripheral face. After the step of grinding the silicon carbide single crystal on at least one of the first and second end faces and the step of grinding the silicon carbide single crystal on the outer peripheral face, a notch part is formed on the silicon carbide single crystal using electric discharge wire processing.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a silicon carbide ingot and a method for manufacturing a silicon carbide substrate.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2009-233819 (Patent Document 1) describes a method for processing a single crystal ingot in which notch processing is performed on the single crystal ingot using a grindstone.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the method for processing a single crystal ingot described in Patent Document 1, when forming a notch in the single crystal ingot, the grindstone comes into contact with the single crystal ingot. Therefore, when forming a notch in an ingot made of silicon carbide, cracks may occur in the single crystal ingot due to the fact that silicon carbide is a hard material.

[0005] An object of the present disclosure is to provide a method for manufacturing a silicon carbide ingot capable of suppressing the occurrence of cracks in the silicon carbide ingot.

Means for Solving the Problems

[0006] The method for manufacturing a silicon carbide ingot according to the present disclosure includes the following steps. A silicon carbide single crystal with a polytype of 4H is prepared. The silicon carbide single crystal has a first end face, a second end face, and an outer peripheral face. The second end face is opposite to the first end face. The outer peripheral face is continuous with each of the first end face and the second end face. The silicon carbide single crystal is ground on at least one of the first end face and the second end face. The silicon carbide single crystal is ground on the outer peripheral face. After the step of grinding the silicon carbide single crystal on at least one of the first end face and the second end face and the step of grinding the silicon carbide single crystal on the outer peripheral face, a notch portion is formed in the silicon carbide single crystal using wire electrical discharge machining.

Advantages of the Invention

[0007] According to the present disclosure, it is possible to provide a method for manufacturing a silicon carbide ingot capable of suppressing the generation of cracks in the silicon carbide ingot.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Mode for Carrying Out the Invention

[0009] [Description of Embodiment of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) The method for manufacturing a silicon carbide ingot according to the present disclosure includes the following steps. A silicon carbide single crystal having a polytype of 4H is prepared. The silicon carbide single crystal has a first end face, a second end face, and an outer peripheral face. The second end face is opposite to the first end face. The outer peripheral face is continuous with each of the first end face and the second end face. The silicon carbide single crystal is ground at at least one of the first end face and the second end face. The silicon carbide single crystal is ground on the outer peripheral face. After the step of grinding the silicon carbide single crystal at at least one of the first end face and the second end face and the step of grinding the silicon carbide single crystal on the outer peripheral face, a notch portion is formed in the silicon carbide single crystal using wire electrical discharge machining. Thereby, generation of cracks in the silicon carbide ingot can be suppressed as compared with the case of forming the notch portion using a grinding wheel.

[0011] (2) According to the method for manufacturing a silicon carbide ingot according to (1) above, the applied voltage in wire electrical discharge machining may be 100 V or more and 500 V or less. By the applied voltage being 500 V or less, it is possible to suppress the thickness of the processed and altered portion of the silicon carbide ingot from becoming excessively thick.

[0012] (3) According to the method for manufacturing a silicon carbide ingot according to (1) or (2) above, the wire feed rate in wire electrical discharge machining may be 400 m / min or more and 600 m / min or less. By the wire feed rate being 400 m / min or more, it is possible to suppress the wire from being melted and broken. By the wire feed rate being 600 m / min or less, it is possible to reduce the wire consumption.

[0013] (4) According to the method for manufacturing a silicon carbide ingot according to any one of (1) to (3) above, in wire electrical discharge machining, the silicon carbide ingot may be disposed on a stage configured to be movable. The feed rate of the stage in wire electrical discharge machining may be 0.5 mm / min or more and 1.5 mm / min or less. By the feed rate of the stage being 0.5 mm / min or more, it is possible to shorten the time required to form a notch portion in the silicon carbide single crystal.

[0014] (5) According to the method for manufacturing a silicon carbide ingot according to any one of (1) to (4) above, the diameter of the silicon carbide ingot may be 150 mm or more.

[0015] (6) According to the method for manufacturing a silicon carbide ingot according to (5) above, the diameter of the silicon carbide ingot may be 200 mm or more.

[0016] (7) The method for manufacturing a silicon carbide substrate according to the present disclosure has the following steps. A silicon carbide ingot is prepared using the method for manufacturing a silicon carbide ingot according to any one of (1) to (6) above. The silicon carbide ingot is cut. According to the method for manufacturing a silicon carbide substrate according to the present embodiment, a silicon carbide ingot having a notch formed using a discharge wire is prepared. Therefore, in the manufactured silicon carbide substrate, it is possible to suppress the remaining of processing strain.

[0017] (8) The method for manufacturing a silicon carbide substrate according to (7) above may further have a step of chamfering the notch portion after the step of cutting the silicon carbide ingot. Thereby, it is possible to remove the processed altered portion of the silicon carbide substrate formed when forming the notch portion.

[0018] (9) According to the method for manufacturing a silicon carbide substrate according to (8) above, in the chamfering process, the amount of cutting in the notch portion may be 0.1 mm or more. Therefore, it is possible to more reliably remove the processed altered portion of the silicon carbide substrate formed when forming the notch portion.

[0019] [Details of Embodiments of the Present Disclosure] Next, details of an embodiment of the present disclosure (hereinafter also referred to as the present embodiment) will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated. In the crystallographic description in this specification, individual orientations are indicated by [], collective orientations by <>, individual planes by (), and collective planes by {}. Also, for negative indices, in crystallography, a "-" (bar) is placed above the number, but in this specification, a negative sign is placed in front of the number.

[0020] (First Embodiment) <Silicon Carbide Ingot> First, the configuration of the silicon carbide ingot according to the first embodiment will be described. FIG. 1 is a schematic plan view showing the configuration of the silicon carbide ingot according to the first embodiment. As shown in FIG. 1, the silicon carbide ingot 100 mainly has a first main surface 11 and a first outer peripheral surface 19. The first main surface 11 is, for example, planar. The first main surface 11 extends along each of a first direction 101 and a second direction 102. The first outer peripheral surface 19 is continuous with the first main surface 11. The shape of the first outer peripheral surface 19 is annular.

[0021] The first direction 101 is, for example, the <11-20> direction. The first direction 101 may be, for example, the [11-20] direction. The first direction 101 may be a direction obtained by projecting the <11-20> direction onto the first main surface 11. From another perspective, the first direction 101 may be, for example, a direction including a <11-20> direction component.

[0022] The second direction 102 is perpendicular to the first direction 101. The second direction 102 is, for example, the <1-100> direction. The second direction 102 may be, for example, the [1-100] direction. The second direction 102 may be a direction obtained by projecting the <1-100> direction onto the first main surface 11. From another perspective, the second direction 102 may be, for example, a direction including a <1-100> direction component.

[0023] The first main surface 11 is the {0001} plane or a plane inclined with respect to the {0001} plane. The inclination angle (off angle) of the first main surface 11 with respect to the {0001} plane is, for example, 0° or more and 8° or less. When the first main surface 11 is inclined with respect to the {0001} plane, the inclination direction (off direction) of the first main surface 11 may be, for example, the first direction 101 or the second direction 102.

[0024] The silicon carbide ingot 100 is composed of hexagonal silicon carbide. The polytype of the hexagonal silicon carbide constituting the silicon carbide ingot 100 is 4H. The silicon carbide ingot 100 may be conductive or semi-insulating.

[0025] As shown in FIG. 1, in the silicon carbide ingot 100, a notch (first notch 14) is provided. The first notch 14 is a notch provided in the silicon carbide ingot 100. The first outer peripheral surface 19 has an arc-shaped portion (first arc-shaped portion 18) and a notch portion (first notch portion 17). When viewed perpendicular to the first main surface 11 (hereinafter also referred to as the first plan view), the shape of the first arc-shaped portion 18 is arc-shaped. In the first plan view, the center (first center A1) of the silicon carbide ingot 100 is the center of a circle including an arc along the first arc-shaped portion 18.

[0026] The first notch portion 17 is continuous with the first arc-shaped portion 18. The first notch portion 17 constitutes the first notch 14. In the first plan view, the first notch portion 17 is concave, for example, along the second direction 102. From another perspective, in the first plan view, the first notch portion 17 is concave from the circle including the arc along the first arc-shaped portion 18 toward the first center A1. In the first plan view, the tangent line of the first notch portion 17 is the first virtual line 91.

[0027] As shown in FIG. 1, the diameter of the silicon carbide ingot 100 is the first diameter W1. The first diameter W1 is, for example, 150 mm (6 inches). The first diameter W1 may be, for example, 150 mm (6 inches) or more, or 200 mm (8 inches) or more, or 250 mm (10 inches) or more. The first diameter W1 may be, for example, 400 mm (16 inches) or less. In the first plan view, the first diameter W1 is the longest straight-line distance between two different points on the first outer peripheral surface 19.

[0028] In this specification, 6 inches means 150 mm or 152.4 mm (6 inches × 25.4 mm / inch). 8 inches means 200 mm or 203.2 mm (8 inches × 25.4 mm / inch). 10 inches means 250 mm or 254 mm (10 inches × 25.4 mm / inch). 16 inches means 400 mm or 406.4 mm (16 inches × 25.4 mm / inch).

[0029] FIG. 2 is a schematic cross-sectional view taken along line II-II of FIG. 1. The cross-section shown in FIG. 2 is a cross-section perpendicular to the first main surface 11 and perpendicular to the first virtual line 91. As shown in FIG. 2, the silicon carbide ingot 100 has a second main surface 12. The second main surface 12 is opposite to the first main surface 11. The second main surface 12 is continuous with the first outer peripheral surface 19. The direction from the second main surface 12 toward the first main surface 11 is defined as the third direction 103. The third direction 103 is, for example, the same direction as the growth direction of the silicon carbide crystal constituting the silicon carbide ingot 100. The thickness of the silicon carbide ingot 100 in the third direction 103 is, for example, 10 mm or more.

[0030] As shown in FIG. 2, the silicon carbide ingot 100 has a first machined affected zone 15, a second machined affected zone 16, and a first main body portion 10. The first machined affected zone 15 forms a first notch portion 17. The first machined affected zone 15 is a portion that has received machining damage by wire electrical discharge machining. Specifically, the first machined affected zone 15 is composed of silicon carbide crystals that have been amorphized due to the heat generated in wire electrical discharge machining.

[0031] In a cross-section perpendicular to the first main surface 11 and perpendicular to the first virtual line 91, the thickness of the first machined affected zone 15 in the direction perpendicular to the first notch portion 17 is defined as the first thickness H1. The first thickness H1 is, for example, 0.05 mm or less.

[0032] The second machined affected zone 16 forms a first arcuate portion 18. The second machined affected zone 16 is a portion that has received machining damage by grinding of the silicon carbide single crystal on the outer peripheral surface. Specifically, the second machined affected zone 16 is composed of silicon carbide crystals that have been distorted due to the grinding of the silicon carbide single crystal on the outer peripheral surface.

[0033] As shown in FIG. 2, the thickness of the second machined and modified portion 16 is set to a second thickness H2. The second thickness H2 is the thickness of the second machined and modified portion 16 in the direction from the first arc-shaped portion 18 toward the first center A1 (see FIG. 1) in the first plan view. The second thickness H2 is, for example, thicker than the first thickness H1. The second thickness H2 is, for example, 0.1 mm or less.

[0034] The first main body portion 10 is a portion that has not received machining damage by wire electrical discharge machining and machining damage by grinding of the single-crystalline silicon carbide on the outer peripheral surface. The first main body portion 10 is composed of a single-crystalline silicon carbide having a normal crystal lattice. In a cross section perpendicular to the first main surface 11 and perpendicular to the first imaginary line 91, the first main body portion 10 is between the first machined and modified portion 15 and the second machined and modified portion 16. The first main body portion 10 is in contact with each of the first machined and modified portion 15 and the second machined and modified portion 16. The first main body portion 10 is surrounded by the first machined and modified portion 15 and the second machined and modified portion 16. [[ID=⑤]] [[ID=⑥]]

[0035] [[ID=⑦]] [[ID=⑧]]<Silicon carbide substrate>[[ID=⑨]] [[ID=⑩]]Next, the configuration of the silicon carbide substrate according to the first embodiment will be described. [[ID=⑪]] [[ID=⑫]]

[0036] [[ID=⑬]] [[ID=⑭]]FIG. 3 is a schematic plan view showing the configuration of the silicon carbide substrate according to the first embodiment. As shown in FIG. 3, the silicon carbide substrate 200 mainly has a third main surface 21 and a second outer peripheral surface 29. The third main surface 21 is, for example, planar. The third main surface 21 extends along each of the first direction 101 and the second direction 102. The second outer peripheral surface 29 is continuous with the third main surface 21. The shape of the second outer peripheral surface 29 is annular. [[ID=⑮]] [[ID=⑯]]

[0037] [[ID=⑰]] [[ID=⑱]]The third main surface 21 is a {0001} plane or a plane inclined with respect to the {0001} plane. The inclination angle (off angle) of the third main surface 21 with respect to the {0001} plane is, for example, 0° or more and 8° or less. When the third main surface 21 is inclined with respect to the {0001} plane, the inclination direction (off direction) of the third main surface 21 may be, for example, the first direction 101 or the second direction 102. [[ID=⑲]] [[ID=⑳]]

[0038] [[ID=㉑]] In the silicon carbide substrate 200, a notch (second notch 24) is provided. The second notch 24 is a notch provided in the silicon carbide substrate 200. The second outer peripheral surface 29 has an arc-shaped portion (second arc-shaped portion 28) and a notch portion (second notch portion 27). When viewed perpendicular to the third main surface 21 (hereinafter also referred to as the second plan view), the shape of the second arc-shaped portion 28 is arc-shaped. In the second plan view, the center (second center A2) of the silicon carbide substrate 200 is the center of a circle including an arc along the second arc-shaped portion 28.

[0039] The second notch portion 27 is continuous with the second arc-shaped portion 28. The second notch portion 27 constitutes the second notch 24. In the second plan view, the second notch portion 27 is concave, for example, along the second direction 102. From another perspective, in the second plan view, the second notch portion 27 is concave from the circle including the arc along the second arc-shaped portion 28 toward the second center A2. In the second plan view, the tangent line of the second notch portion 27 is the second virtual line 92.

[0040] The silicon carbide substrate 200 is a substrate manufactured by slicing the above-described silicon carbide ingot 100 (see FIGS. 1 and 2) using a wire saw or the like. From another perspective, the silicon carbide substrate 200 has substantially the same configuration as a part of the above-described silicon carbide ingot 100. The second arc-shaped portion 28 corresponds to a part of the above-described first arc-shaped portion 18 (see FIGS. 1 and 2). The second notch portion 27 corresponds to a part of the above-described first notch portion 17 (see FIGS. 1 and 2).

[0041] The silicon carbide substrate 200 is made of, for example, hexagonal silicon carbide. The polytype of the hexagonal silicon carbide constituting the silicon carbide substrate 200 is 4H. The silicon carbide substrate 200 may be a conductive substrate or a semi-insulating substrate.

[0042] As shown in FIG. 3, the diameter of the silicon carbide substrate 200 is the second diameter W2. The second diameter W2 may be, for example, 150 mm (6 inches) or more, 200 mm (8 inches) or more, or 250 mm (10 inches) or more. The second diameter W2 may be, for example, 400 mm (16 inches) or less. In the second plan view, the second diameter W2 is the longest straight-line distance between two different points on the second outer peripheral surface 29.

[0043] FIG. 4 is a schematic cross-sectional view taken along line IV-IV of FIG. 3. The cross-section shown in FIG. 4 is a cross-section perpendicular to the third main surface 21 and perpendicular to the second virtual line 92. As shown in FIG. 4, the silicon carbide substrate 200 has a fourth main surface 22. The fourth main surface 22 is opposite to the third main surface 21. The fourth main surface 22 is continuous with the second outer peripheral surface 29. The third main surface 21 is in the third direction 103 with respect to the fourth main surface 22. The thickness of the silicon carbide substrate 200 in the third direction 103 is, for example, 1 mm or less.

[0044] As shown in FIG. 4, the silicon carbide substrate 200 has a third processed and modified portion 25, a fourth processed and modified portion 26, and a second main body portion 20. The third processed and modified portion 25 constitutes the second notch portion 27. The third processed and modified portion 25 corresponds to a part of the above-described first processed and modified portion 15 (see FIG. 2). The third processed and modified portion 25 is a portion that has received processing damage by wire electrical discharge machining. Specifically, the third processed and modified portion 25 is composed of silicon carbide crystals that have been amorphized due to heat generated in wire electrical discharge machining.

[0045] In a cross-section perpendicular to the third main surface 21 and perpendicular to the second virtual line 92, the thickness of the third processed and modified portion 25 in a direction perpendicular to the second notch portion 27 is the third thickness H3. The third thickness H3 is, for example, 0.05 mm or less. The third thickness H3 may be substantially the same as the above-described first thickness H1 (see FIG. 2).

[0046] The fourth machined and altered portion 26 constitutes the second arc-shaped portion 28. The fourth machined and altered portion 26 corresponds to a part of the above-described second machined and altered portion 16 (see FIG. 2). The fourth machined and altered portion 26 is a portion that has received machining damage due to grinding of the silicon carbide single crystal on the above-described outer peripheral surface. Specifically, the fourth machined and altered portion 26 is composed of silicon carbide crystals that have been distorted due to grinding of the silicon carbide single crystal on the outer peripheral surface.

[0047] As shown in FIG. 4, the thickness of the fourth machined and altered portion 26 is defined as the fourth thickness H4. The fourth thickness H4 is the thickness of the fourth machined and altered portion 26 in the direction from the second arc-shaped portion 28 toward the second center A2 (see FIG. 3) in the second plan view. The fourth thickness H4 is, for example, thicker than the third thickness H3. The fourth thickness H4 is, for example, 0.1 mm or less. The fourth thickness H4 may be substantially the same as the above-described second thickness H2 (see FIG. 2).

[0048] The second main body portion 20 corresponds to a part of the above-described first main body portion 10 (see FIG. 2). The second main body portion 20 is a portion that has not received machining damage due to wire electrical discharge machining and machining damage due to grinding of the silicon carbide single crystal on the outer peripheral surface. The second main body portion 20 is composed of silicon carbide single crystals having a normal crystal lattice.

[0049] In a cross section perpendicular to the third main surface 21 and perpendicular to the second virtual line 92, the second main body portion 20 is located between the third machined and altered portion 25 and the fourth machined and altered portion 26. The second main body portion 20 is in contact with each of the third machined and altered portion 25 and the fourth machined and altered portion 26. The second main body portion 20 is surrounded by the third machined and altered portion 25 and the fourth machined and altered portion 26.

[0050] (Second Embodiment) Next, the configuration of the silicon carbide substrate 200 according to the second embodiment will be described. The silicon carbide substrate 200 according to the second embodiment is different from the silicon carbide substrate 200 according to the first embodiment mainly in that the silicon carbide substrate 200 is chamfered at each of the second notch portion 27 and the second arc-shaped portion 28, and in other respects, it is substantially the same as the silicon carbide substrate 200 according to the first embodiment. Hereinafter, the description will focus on the differences from the silicon carbide substrate 200 according to the first embodiment.

[0051] FIG. 5 is a schematic cross-sectional view showing the configuration of the silicon carbide substrate 200 according to the second embodiment. The cross-section shown in FIG. 5 corresponds to the cross-section shown in FIG. 4. As shown in FIG. 5, in a cross-section perpendicular to the third main surface 21 and perpendicular to the second virtual line 92 (see FIG. 3), the second notch portion 27 is convex in the direction from the second arc-shaped portion 28 toward the second notch portion 27. As shown in FIG. 5, in a cross-section perpendicular to the third main surface 21 and perpendicular to the second virtual line 92, the second arc-shaped portion 28 is convex in the direction from the second notch portion 27 toward the second arc-shaped portion 28.

[0052] In FIG. 5, the broken line indicates the portion removed from the silicon carbide substrate 200 (see FIG. 4) according to the first embodiment. As shown in FIG. 5, in the silicon carbide substrate 200 according to the second embodiment, each of the third processed altered layer 25 and the fourth processed altered layer 26 has been removed. From another perspective, the silicon carbide substrate 200 is constituted by, for example, the second main body portion 20.

[0053] By performing chamfering on the second notch portion 27, the third processed altered layer 25 has been removed. The amount of cutting in the second notch portion 27 is the first cutting amount T1. The first cutting amount T1 is the amount of cutting of the silicon carbide substrate 200 in the direction perpendicular to the second notch portion 27 in a cross-section perpendicular to the third main surface 21 and perpendicular to the second virtual line 92. The first cutting amount T1 is, for example, larger than the third thickness H3. The first cutting amount T1 is, for example, 0.1 mm or more.

[0054] By chamfering the second arc-shaped portion 28, the fourth processed and altered portion 26 is removed. The amount of cutting in the second arc-shaped portion 28 is defined as the second cutting amount T2. The second cutting amount T2 is the amount of cutting of the silicon carbide substrate 200 in the direction from the second arc-shaped portion 28 toward the second center A2 (see FIG. 3) in the second plan view. The second cutting amount T2 may be substantially the same as the first cutting amount T1, or may be larger than the first cutting amount T1. The second cutting amount T2 is, for example, larger than the fourth thickness H4. The second cutting amount T2 is, for example, 0.1 mm or more.

[0055] Note that the silicon carbide substrate 200 may have a portion that has received processing damage due to chamfering. This portion may constitute the second outer peripheral surface 29. This portion may surround the second main body portion 20.

[0056] <Method for manufacturing silicon carbide ingot> Next, a method for manufacturing the silicon carbide ingot 100 according to the present embodiment will be described. FIG. 6 is a flowchart schematically showing the method for manufacturing the silicon carbide ingot 100 according to the present embodiment. As shown in FIG. 6, the method for manufacturing the silicon carbide ingot 100 according to the present embodiment mainly includes a step of preparing a silicon carbide single crystal (S10), a step of grinding the silicon carbide single crystal at an end face (S20), a step of grinding the silicon carbide single crystal at an outer peripheral surface (S30), and a step of forming a notch portion in the silicon carbide single crystal using wire electrical discharge machining (S40).

[0057] First, the step of preparing a silicon carbide single crystal (S10) is performed. FIG. 7 is a cross-sectional schematic view showing the step of preparing a silicon carbide single crystal (S10). As shown in FIG. 7, a silicon carbide single crystal 300 is prepared. Specifically, for example, a polytype 4H silicon carbide single crystal 300 is manufactured by the sublimation method. The growth direction of the silicon carbide single crystal 300 is, for example, the same as the third direction 103. The silicon carbide single crystal 300 has a first end face 31, a second end face 32, and a third outer peripheral surface 39.

[0058] The first end face 31 is convex, for example, in the third direction 103. The second end face 32 is opposite to the first end face 31. The second end face 32 is, for example, planar. The first end face 31 is in the third direction 103 with respect to the second end face 32. The third outer peripheral surface 39 is continuous with each of the first end face 31 and the second end face 32. The third outer peripheral surface 39 is annular. As it separates from the second end face 32 along the third direction 103, for example, the diameter of the third outer peripheral surface 39 increases.

[0059] Next, a step (S20) of grinding the silicon carbide single crystal on the end face is performed. For example, using a grindstone (not shown), the silicon carbide single crystal 300 is ground on at least one of the first end face 31 and the second end face 32. Specifically, for example, the silicon carbide single crystal 300 is ground on the first end face 31 so that the first end face 31 becomes planar. On the second end face 32, the silicon carbide single crystal 300 may not be ground.

[0060] In the step (S20) of grinding the silicon carbide single crystal on the end face, the abrasive grains of the grindstone are composed of, for example, diamond. The binder of the grindstone is, for example, a vitrified bond. Compared with the case where the binder of the grindstone is a metal bond, when the binder of the grindstone is a vitrified bond, the self-generation effect of the grindstone is promoted. In the step (S20) of grinding the silicon carbide single crystal on the end face, the grit size of the grindstone is, for example, #140 or #170.

[0061] Next, a step (S30) of grinding the silicon carbide single crystal on the outer peripheral surface is performed. For example, using a grindstone (not shown), the silicon carbide single crystal 300 is ground on the third outer peripheral surface 39. Specifically, when viewed in the third direction 103, the silicon carbide single crystal 300 is ground on the third outer peripheral surface 39 so that the silicon carbide single crystal 300 becomes columnar.

[0062] In the step (S30) of grinding the silicon carbide single crystal on the outer peripheral surface, the abrasive grains of the grinding wheel are made of, for example, diamond. The bonding material of the grinding wheel is, for example, a vitrified bond. In the step (S30) of grinding the silicon carbide single crystal on the outer peripheral surface, the grit size of the grinding wheel is, for example, #140 or #170. Note that the step (S30) of grinding the silicon carbide single crystal on the outer peripheral surface may be performed before the step (S20) of grinding the silicon carbide single crystal on the end face.

[0063] Next, a step (S40) of forming a notch portion in the silicon carbide single crystal using wire electrical discharge machining is performed. FIG. 8 is a schematic diagram showing the step (S40) of forming a notch portion in the silicon carbide single crystal using wire electrical discharge machining. As shown in FIG. 8, a wire electrical discharge machining apparatus 500 is prepared. The wire electrical discharge machining apparatus 500 mainly includes a wire 51, a wire supply unit 52, a stage 53, a power supply 54, and a machining fluid supply unit (not shown).

[0064] The wire 51 is, for example, a brass-plated wire. Specifically, the wire 51 is, for example, an iron wire plated with brass. The wire supply unit 52 feeds out the wire 51. The wire supply unit 52 controls the feed rate of the wire 51.

[0065] The stage 53 is a portion that supports the silicon carbide single crystal 300. The stage 53 is made of a conductive material. The stage 53 moves, for example, along a horizontal plane. The power supply 54 applies a pulsed voltage between the wire 51 and the stage 53. The power supply 54 controls the magnitude of the voltage (applied voltage) applied between the wire 51 and the stage 53. The power supply 54 controls the interval (discharge interval) of the pulsed voltage applied between the wire 51 and the stage 53.

[0066] The machining fluid supply unit supplies machining fluid (not shown) to the position where the wire 51 and the silicon carbide single crystal 300 come into contact. The machining fluid is, for example, deionized water. The machining fluid cools each of the wire 51 and the silicon carbide single crystal. The machining fluid removes machining chips generated by wire electrical discharge machining.

[0067] As shown in FIG. 8, in the step (S40) of forming a notch portion in the single-crystalline silicon carbide using electrical discharge wire machining, the single-crystalline silicon carbide 300 is disposed on the stage 53. The single-crystalline silicon carbide 300 is a workpiece. The single-crystalline silicon carbide 300 is electrically connected to the power supply 54 via the stage 53.

[0068] The wire 51 is supplied from the wire supply unit 52. The wire 51 is supplied along the first arrow B1. The feed rate of the wire 51 is, for example, 400 m / min or more and 600 m / min or less. The feed rate of the wire 51 may be, for example, 430 m / min or more, or may be 460 m / min or more. The feed rate of the wire 51 may be, for example, 570 m / min or less, or may be 540 m / min or less.

[0069] A pulse voltage is applied between the wire 51 and the stage 53 using the power supply 54. Thereby, a pulse voltage is applied between the wire 51 and the single-crystalline silicon carbide 300. The applied voltage is, for example, 100 V or more and 500 V or less. The applied voltage may be, for example, 180 V or more, or may be 250 V or more. The applied voltage may be, for example, 420 V or less, or may be 350 V or less. The discharge interval is, for example, 5 μs.

[0070] When the stage 53 moves, the single-crystalline silicon carbide 300 is moved. The feed rate of the stage 53 is, for example, 0.5 mm / min or more and 1.5 mm / min or less. The feed rate of the stage 53 may be, for example, 0.7 mm / min or more, or may be 0.9 mm / min or more. The feed rate of the stage 53 may be, for example, 1.3 mm / min or less, or may be 1.1 mm / min or less.

[0071] FIG. 9 is a schematic plan view showing a step (S40) of forming a notch portion in a silicon carbide single crystal using wire electrical discharge machining. In FIG. 9, a cross section of a wire 51 is shown. In FIG. 9, a third virtual line 93 indicates the path of the wire 51. The length of the third virtual line 93 when viewed perpendicular to the third main surface 21 is the machining length in wire electrical discharge machining. The machining length is, for example, about 5 mm. As shown in FIG. 9, the portion of the silicon carbide single crystal 300 surrounded by the third outer peripheral surface 39 and the third virtual line 93 is defined as a removed portion 68.

[0072] The silicon carbide single crystal 300 is moved using a stage 53 so that the wire 51 passes through the third virtual line 93. The silicon carbide single crystal 300 moves along the second arrow B2. A pulse voltage is applied between the silicon carbide single crystal 300 and the wire 51 in a state where the silicon carbide single crystal 300 approaches the wire 51, thereby generating a discharge between the silicon carbide single crystal 300 and the wire 51. Due to the heat generated by the discharge, the portion of the silicon carbide single crystal 300 around the wire 51 melts. Therefore, the silicon carbide single crystal 300 is cut without substantially contacting the wire 51.

[0073] By applying a pulse voltage between the silicon carbide single crystal 300 and the wire 51 while moving the silicon carbide single crystal 300, the silicon carbide single crystal 300 is cut along the third virtual line 93. Due to the heat generated by the discharge, the portion of the silicon carbide single crystal 300 around the third virtual line 93 becomes amorphous. From another perspective, due to the heat generated by the discharge, a first machined affected layer 15 (see FIG. 2) is formed.

[0074] The removed portion 68 is separated from the silicon carbide single crystal 300. By removing the removed portion 68, a first notch 14 and a first notch portion 17 (see FIG. 1) are formed. Thus, the silicon carbide ingot 100 according to the above-described embodiment is manufactured.

[0075] <Method for manufacturing a silicon carbide substrate> Next, a method for manufacturing the silicon carbide substrate 200 according to the present embodiment will be described. FIG. 10 is a flowchart schematically showing the method for manufacturing the silicon carbide substrate 200 according to the present embodiment. As shown in FIG. 10, the method for manufacturing the silicon carbide substrate 200 according to the present embodiment mainly includes a step of preparing a silicon carbide ingot (S1), a step of cutting the silicon carbide ingot (S50), a step of chamfering the arc-shaped portion of the silicon carbide substrate (S60), and a step of chamfering the notch portion of the silicon carbide substrate (S70).

[0076] First, the step of preparing a silicon carbide ingot (S1) is carried out. Specifically, using the method for manufacturing the silicon carbide ingot 100 described above, the silicon carbide ingot 100 according to the present embodiment (see FIGS. 1 and 2) is prepared.

[0077] Next, the step of cutting the silicon carbide ingot (S50) is carried out. For example, by slicing the silicon carbide ingot 100 using a wire saw, the silicon carbide substrate 200 is formed. Thus, the silicon carbide substrate 200 according to the first embodiment described above (see FIGS. 3 and 4) is manufactured. From another perspective, the step of preparing a silicon carbide ingot (S1) and the step of cutting the silicon carbide ingot (S50) constitute the method for manufacturing the silicon carbide substrate 200 according to the first embodiment.

[0078] Next, the step of chamfering the arc-shaped portion of the silicon carbide substrate (S60) is carried out. FIG. 11 is a schematic diagram showing the step of chamfering the arc-shaped portion of the silicon carbide substrate (S60). As shown in FIG. 11, the silicon carbide substrate 200 is disposed on a support base 86. The support base 86 rotates the silicon carbide substrate 200. The support base 86 is movable along a plane perpendicular to the central axis (first central axis C1) of the silicon carbide substrate 200.

[0079] The first grinding wheel 81 is prepared. The first grinding wheel 81 is attached to the first shaft portion 83. The abrasive grains of the first grinding wheel 81 are composed of, for example, diamond. The bonding material of the first grinding wheel 81 is, for example, a metal bond. When the bonding material of the first grinding wheel 81 is a vitrified bond as compared with the case where the bonding material of the first grinding wheel 81 is a metal bond, the shape accuracy of the silicon carbide substrate 200 can be improved. The grit size of the first grinding wheel 81 is, for example, #400 or #600. The first shaft portion 83 rotates the first grinding wheel 81.

[0080] FIG. 12 is a partial cross-sectional schematic view showing the step (S60) of chamfering the arc-shaped portion of the silicon carbide substrate. As shown in FIGS. 11 and 12, the first grinding wheel 81 has a first concave surface 71. The first concave surface 71 is a surface that contacts the silicon carbide substrate 200. The first concave surface 71 is concave in a direction from the silicon carbide substrate 200 toward the central axis (second central axis C2) of the first grinding wheel 81. When viewed along the direction in which the second central axis C2 extends, the shape of the first concave surface 71 is annular. The minimum diameter of the first grinding wheel 81 is defined as the first minimum diameter D1. The first minimum diameter D1 is the diameter of the portion of the first concave surface 71 that is closest to the second central axis C2.

[0081] As shown in FIGS. 11 and 12, when the support base 86 rotates, the silicon carbide substrate 200 rotates about the first central axis C1. When the first shaft portion 83 rotates, the first grinding wheel 81 rotates about the second central axis C2. When viewed along the direction in which the first central axis C1 extends, the rotation direction of the silicon carbide substrate 200 and the rotation direction of the first grinding wheel 81 are, for example, the same.

[0082] As shown in FIGS. 11 and 12, when the support base 86 moves, the silicon carbide substrate 200 moves. As a result, while the first grinding wheel 81 and the silicon carbide substrate 200 each rotate, the first concave surface 71 and the second arc-shaped portion 28 come into contact. In the second arc-shaped portion 28, the silicon carbide substrate 200 is ground. The amount of material removed (second amount of material removed T2, see FIG. 5) from the silicon carbide substrate 200 in the second arc-shaped portion 28 is, for example, 0.1 mm or more. By the above, the fourth machined and altered portion 26 is removed.

[0083] Next, a chamfering process (S70) is performed on the notch portion of the silicon carbide substrate. FIG. 13 is an enlarged plan schematic view showing the chamfering process (S70) performed on the notch portion of the silicon carbide substrate. FIG. 14 is a partial cross-sectional schematic view showing the chamfering process (S70) performed on the notch portion of the silicon carbide substrate.

[0084] As shown in FIGS. 13 and 14, a second grinding wheel 82 is prepared. The second grinding wheel 82 is attached to a second shaft portion 84. The abrasive grains of the second grinding wheel 82 are made of, for example, diamond. The binder of the second grinding wheel 82 is, for example, a metal bond. Therefore, as described above, the shape accuracy of the silicon carbide substrate 200 can be improved. The grit size of the second grinding wheel 82 is, for example, #400 or #600.

[0085] The second shaft portion 84 rotates the second grinding wheel 82. The second grinding wheel 82 has a second concave surface 72. The second concave surface 72 is the surface that contacts the silicon carbide substrate 200. The second concave surface 72 is concave in the direction from the silicon carbide substrate 200 toward the central axis (third central axis C3) of the second grinding wheel 82.

[0086] The minimum diameter of the second grinding wheel 82 is defined as a second minimum diameter D2. The second minimum diameter D2 is the diameter at the portion of the second concave surface 72 that is closest to the third central axis C3. The second minimum diameter D2 is smaller than the first minimum diameter D1 (see FIG. 12).

[0087] As shown in FIG. 13, the maximum width E of the second notch portion 27 before the chamfering process is performed on the notch portion is larger than the second minimum diameter D2 (see FIG. 14) and smaller than the first minimum diameter D1 (see FIG. 12). The maximum width E is the distance between two connection points of the second notch portion 27 and the second arc-shaped portion 28 in a plan view.

[0088] When the second shaft portion 84 rotates, the second grinding wheel 82 rotates about the third central axis C3. In the step (S70) of chamfering the notch portion of the silicon carbide substrate, the silicon carbide substrate 200 is disposed on the support table 86. In the step (S70) of chamfering the notch portion of the silicon carbide substrate, the silicon carbide substrate 200 does not rotate.

[0089] As shown in FIG. 13, when the silicon carbide substrate 200 moves, the second grinding wheel 82 moves relative to the silicon carbide substrate 200 along the third arrow B3. Specifically, the second grinding wheel 82 moves along the second notch portion 27. As shown in FIG. 14, while the second grinding wheel 82 rotates, the second concave surface 72 and the second notch portion 27 come into contact with each other. Thereby, the silicon carbide substrate 200 is ground at the second notch portion 27. Note that the step (S70) of chamfering the notch portion of the silicon carbide substrate may be performed before the step (S60) of chamfering the arc-shaped portion of the silicon carbide substrate.

[0090] The amount of material removed from the silicon carbide substrate 200 at the second notch portion 27 (first amount of material removed T1, see FIG. 5) is, for example, 0.1 mm or more. Thereby, the third processed and altered portion 25 is removed. As described above, the silicon carbide substrate 200 (see FIG. 5) according to the second embodiment is manufactured.

[0091] Next, the effects of the method for manufacturing a silicon carbide ingot and the method for manufacturing a silicon carbide substrate according to the present embodiment will be described.

[0092] As a method of forming a notch portion in an ingot made of silicon or the like, there is a method of forming the notch portion using a grinding wheel. In this method, when forming the notch portion, the grinding wheel and the ingot come into contact with each other. Compared with an ingot made of silicon or the like, an ingot made of silicon carbide (silicon carbide ingot) is likely to crack because silicon carbide is a hard material. Therefore, when forming a notch portion in a silicon carbide ingot using a grinding wheel, cracks may occur in the silicon carbide ingot.

[0093] According to the method for manufacturing the silicon carbide ingot 100 according to this embodiment, a notch is formed in the silicon carbide single crystal 300 by using electrical discharge wire cutting. In electrical discharge wire cutting, the silicon carbide single crystal 300 and the wire 51 do not substantially contact each other. Therefore, the occurrence of cracks in the silicon carbide ingot 100 can be suppressed as compared with the case where a notch is formed using a grinding wheel.

[0094] As a binder for the grinding wheel used when forming the notch, metal bond may be used. When the binder is a metal bond, the accuracy of the shape of the notch can be improved as compared with the case where the binder is a vitrified bond. However, the frequency of replacing the grinding wheel increases due to the wear of the abrasive grains. In particular, when forming a notch in a silicon carbide single crystal, the wear of the abrasive grains becomes excessively fast because silicon carbide is a hard material. Therefore, the consumption of relatively expensive grinding wheels increases excessively. As a result, the cost required to manufacture the silicon carbide ingot 100 increases.

[0095] According to the method for manufacturing the silicon carbide ingot 100 according to this embodiment, the wire 51 is used when forming the notch. The price of the wire 51 is lower than that of the grinding wheel. Therefore, the cost required to manufacture the silicon carbide ingot 100 can be reduced as compared with the case where a notch is formed in the silicon carbide single crystal 300 using a grinding wheel.

[0096] The method for manufacturing the silicon carbide ingot 100 according to this embodiment includes a step (S30) of grinding the silicon carbide single crystal on the outer peripheral surface. Therefore, in the method for manufacturing the silicon carbide ingot 100 according to this embodiment, the outer peripheral surface of the silicon carbide single crystal 300 is ground, and a notch is formed in the silicon carbide single crystal 300 by using electrical discharge wire cutting. Therefore, when forming the shape of the outer peripheral surface into a columnar shape, the processing can be facilitated by using grinding, and when forming the notch, the occurrence of cracks in the silicon carbide ingot 100 can be suppressed by using electrical discharge wire cutting.

[0097] When machining the outer peripheral surface of the single-crystalline silicon carbide 300 using electrical discharge wire cutting, amorphous silicon carbide is formed in the portion of the silicon carbide ingot 100 close to the first arcuate portion 18. For example, when slicing the silicon carbide ingot 100 using a wire saw, it is considered that the load applied to the wire saw differs between when cutting a portion composed of amorphous silicon carbide and when cutting a portion composed of non-amorphized silicon carbide. In this case, the shape accuracy of the silicon carbide substrate 200 formed by slicing deteriorates. According to the method for manufacturing the silicon carbide ingot 100 according to the present embodiment, silicon carbide does not become amorphous in the portion of the silicon carbide ingot 100 close to the first arcuate portion 18. Thereby, it is possible to suppress deterioration in the shape accuracy of the silicon carbide substrate 200 manufactured using the silicon carbide ingot 100.

[0098] When the applied voltage in electrical discharge wire cutting is excessively large, the thickness of the first processed altered layer 15 in the silicon carbide ingot 100 becomes excessively thick. In this case, when manufacturing the silicon carbide substrate 200 using the silicon carbide ingot 100, the time required to remove the third processed altered layer 25 increases. According to the method for manufacturing the silicon carbide ingot 100 according to the present embodiment, the applied voltage in electrical discharge wire cutting is 500 V or less. Therefore, it is possible to suppress the thickness of the first processed altered layer 15 of the silicon carbide ingot 100 from becoming excessively thick. Thereby, when manufacturing the silicon carbide substrate 200 using the silicon carbide ingot 100 according to the present embodiment, the time required to remove the third processed altered layer 25 can be reduced.

[0099] According to the method for manufacturing the silicon carbide ingot 100 according to the present embodiment, the feed rate of the wire 51 in electrical discharge wire cutting is 400 m / min or more and 600 m / min or less. By the feed rate of the wire 51 being 400 m / min or more, it is possible to suppress the wire 51 from being melted and broken. By the feed rate of the wire 51 being 600 m / min or less, it is possible to suppress the consumption amount of the wire 51 from increasing excessively.

[0100] According to the method for manufacturing the silicon carbide ingot 100 according to this embodiment, the feed rate of the stage 53 in the wire electrical discharge machining is 0.5 mm / min or more and 1.5 mm / min or less. Since the feed rate of the stage 53 is 0.5 mm / min or more, the time required to form a notch portion in the silicon carbide single crystal 300 can be shortened.

[0101] When forming a notch portion using a grinding wheel, the grinding wheel comes into contact with the silicon carbide single crystal 300. In this case, the silicon carbide single crystal 300 is pulled by the grinding wheel along the moving direction and the rotating direction of the grinding wheel, so that processing strain occurs in the silicon carbide single crystal 300. The portion of the silicon carbide single crystal 300 where the processing strain has occurred may remain in each of the silicon carbide ingot 100 and the silicon carbide substrate 200 manufactured using the silicon carbide single crystal 300. Specifically, even after chamfering the second outer peripheral surface 29 of the silicon carbide substrate 200, a portion where the processing strain has occurred may remain. When an epitaxial layer is formed on the silicon carbide substrate 200, it is considered that defects in the epitaxial layer increase due to the processing strain remaining in the silicon carbide substrate 200.

[0102] According to the method for manufacturing the silicon carbide substrate 200 according to this embodiment, a silicon carbide ingot 100 in which a notch portion is formed using a wire electrical discharge is prepared. Therefore, it is possible to suppress the remaining of processing strain in the manufactured silicon carbide substrate 200. As a result, it is considered that an increase in defects in the epitaxial layer formed on the silicon carbide substrate 200 can be suppressed.

[0103] The method for manufacturing the silicon carbide substrate 200 according to this embodiment has a step (S70) of chamfering the notch portion. Therefore, the third processed and altered portion 25 of the silicon carbide substrate 200 formed by the formation of the notch portion can be removed. Thereby, when an epitaxial layer is formed on the silicon carbide substrate 200, it is possible to suppress an increase in defects in the epitaxial layer due to the third processed and altered portion 25.

[0104] According to the method for manufacturing the silicon carbide substrate 200 according to this embodiment, in the chamfering process, the amount of material removed at the notch portion (the second notch portion 27) is 0.1 mm or more. Therefore, the third processed altered layer 25 of the silicon carbide substrate 200 can be more reliably removed.

[0105] In addition, in the above, the configuration of the method for manufacturing the silicon carbide substrate 200 in which each of the third processed altered layer 25 and the fourth processed altered layer 26 is completely removed has been described. However, the configuration of the method for manufacturing the silicon carbide substrate 200 according to the present disclosure is not limited to the above configuration. Specifically, a part of each of the third processed altered layer 25 and the fourth processed altered layer 26 may remain without being removed. The first amount of material removed T1 may be smaller than, for example, the third thickness H3. The second amount of material removed T2 may be smaller than, for example, the fourth thickness H4.

[0106] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above-described embodiments but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0107] 10 First main body portion 11 First main surface 12 Second main surface 14 First notch 15 First processed altered layer 16 Second processed altered layer 17 First notch portion 18 First arc-shaped portion 19 First outer peripheral surface 20 Second main body portion 21 Third main surface 22 Fourth main surface 24 Second notch 25 Third processed altered layer 26 Fourth processed altered layer 27 Second notch portion 28 Second arc-shaped portion 29 Second outer peripheral surface 31 First end surface 32 Second end face 39 Third outer peripheral surface 51 Wire 52 Wire supply unit 53 Stage 54 Power supply 68 Portion to be removed 71 First concave surface 72 Second concave surface 81 First grindstone 82 Second grindstone 83 First shaft portion 84 Second shaft portion 86 Support base 91 First virtual line 92 Second virtual line 93 Third virtual line 100 Silicon carbide ingot 101 First direction 102 Second direction 103 Third direction 200 Silicon carbide substrate 300 Silicon carbide single crystal 500 Electric discharge wire machining apparatus A1 First center A2 Second center B1 First arrow B2 Second arrow B3 Third arrow C1 First central axis C2 Second central axis C3 Third central axis H1 First thickness H2 Second thickness H3 Third thickness H4 Fourth thickness T1 First cutting amount T2 Second cutting amount W1 First diameter W2 Second diameter

Claims

1. A step of preparing a single-crystalline silicon carbide in which the polytype is 4H, The single-crystalline silicon carbide has a first end face, a second end face opposite to the first end face, and an outer peripheral face continuous with each of the first end face and the second end face, A step of grinding the single-crystalline silicon carbide on at least one of the first end face and the second end face, A step of grinding the single-crystalline silicon carbide on the outer peripheral face, After the step of grinding the single-crystalline silicon carbide on at least one of the first end face and the second end face and the step of grinding the single-crystalline silicon carbide on the outer peripheral face, a step of forming a notch portion in the single-crystalline silicon carbide using wire electrical discharge machining is further provided. A method for manufacturing a silicon carbide ingot.

2. The method for manufacturing a silicon carbide ingot according to claim 1, wherein the applied voltage in the wire electrical discharge machining is 100 V or more and 500 V or less.

3. The method for manufacturing a silicon carbide ingot according to claim 1 or claim 2, wherein the feed rate of the wire in the wire electrical discharge machining is 400 m / min or more and 600 m / min or less.

4. In the wire electrical discharge machining, the single-crystalline silicon carbide is disposed on a stage configured to be movable, The method for manufacturing a silicon carbide ingot according to claim 1 or claim 2, wherein the feed rate of the stage in the wire electrical discharge machining is 0.5 mm / min or more and 1.5 mm / min or less.

5. The method for manufacturing a silicon carbide ingot according to claim 1 or claim 2, wherein the diameter of the silicon carbide ingot is 150 mm or more.

6. The method for manufacturing a silicon carbide ingot according to claim 5, wherein the diameter of the silicon carbide ingot is 200 mm or more.

7. A step of preparing a silicon carbide ingot using the method for manufacturing a silicon carbide ingot according to claim 1 or claim 2, A method for manufacturing a silicon carbide substrate, comprising a step of cutting the silicon carbide ingot.

8. The method for manufacturing a silicon carbide substrate according to claim 7, further comprising a step of chamfering the notch portion after the step of cutting the silicon carbide ingot.

9. The method for manufacturing a silicon carbide substrate according to claim 8, wherein the amount of cutting in the notch portion in the chamfering is 0.1 mm or more.

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