Silicon carbide substrate manufacturing method

Abstract

To provide a silicon carbide substrate manufacturing method capable of restraining cracks on a silicon carbide substrate.SOLUTION: A silicon carbide substrate manufacturing method has 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 silicon carbide wafer is formed by cutting the silicon carbide single crystal. A notch part is formed on the silicon carbide wafer using laser.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Japanese Patent Application Laid-Open No. 2000-331897 (Patent Document 1) describes a method for manufacturing a semiconductor wafer in which a notch is formed in the outer peripheral portion of a semiconductor wafer using a grinding wheel.

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 manufacturing a semiconductor wafer described in Patent Document 1, when a notch is formed in the semiconductor wafer, the grinding wheel comes into contact with the semiconductor wafer. Therefore, when a notch is formed in a semiconductor wafer made of silicon carbide, cracks may occur in the semiconductor wafer 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 substrate capable of suppressing the occurrence of cracks in the silicon carbide substrate.

Means for Solving the Problems

[0006] The method for manufacturing a silicon carbide substrate 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 silicon carbide wafer is formed by cutting the silicon carbide single crystal. A notch portion is formed in the silicon carbide wafer using a laser.

Effect of the Invention

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

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

Mode for Carrying Out the Invention

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

[0010] (1) The method for manufacturing a silicon carbide substrate according to the present disclosure has 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 steps of grinding the silicon carbide single crystal on at least one of the first end face and the second end face and grinding the silicon carbide single crystal on the outer peripheral face, a silicon carbide wafer is formed by cutting the silicon carbide single crystal. A notch portion is formed in the silicon carbide wafer using a laser. Thereby, generation of cracks in the silicon carbide substrate can be suppressed as compared with the case of forming the notch portion using a grindstone.

[0011] (2) The method for manufacturing a silicon carbide substrate according to (1) above may further have a step of chamfering the notch portion. Thereby, a processed and altered portion of the silicon carbide substrate formed when forming the notch portion can be removed.

[0012] (3) According to the method for manufacturing a silicon carbide substrate according to (2) above, in the chamfering process, the amount of material removed at the notch portion may be 0.1 mm or more. Therefore, the processed and altered portion of the silicon carbide substrate formed when forming the notch portion can be more reliably removed.

[0013] (4) The method for manufacturing a silicon carbide substrate according to the present disclosure has the following steps. A silicon carbide wafer with a polytype of 4H is prepared. A notch portion is formed on the silicon carbide wafer using a laser. As a result, the generation of cracks in the silicon carbide substrate can be suppressed as compared with the case of forming the notch portion using a grinding wheel.

[0014] (5) The method for manufacturing a silicon carbide substrate according to (4) above may further include a step of performing chamfering on the notch portion. Thereby, the processed and altered portion of the silicon carbide substrate formed when forming the notch portion can be removed.

[0015] (6) According to the method for manufacturing a silicon carbide substrate according to any one of (1) to (5) above, the wavelength of the laser may be 1000 nm or more and 11000 nm or less.

[0016] (7) According to the method for manufacturing a silicon carbide substrate according to any one of (1) to (6) above, the laser may be a fiber laser, a YAG laser, or a CO2 laser.

[0017] (8) According to the method for manufacturing a silicon carbide substrate according to any one of (1) to (7) above, in the step of forming a notch portion on the silicon carbide wafer using a laser, the notch portion may be formed by scanning the laser a plurality of times.

[0018] (9) According to the method for manufacturing a silicon carbide substrate according to any one of (1) to (3) above, after the step of grinding the outer peripheral surface, the diameter of the silicon carbide single crystal may be 150 mm or more.

[0019] (10) According to the method for manufacturing a silicon carbide substrate according to the above (9), after the step of grinding the outer peripheral surface, the diameter of the single crystal silicon carbide may be 200 mm or more.

[0020] (11) According to the method for manufacturing a silicon carbide substrate according to any one of the above (1) to (10), the thickness of the silicon carbide wafer may be 1 mm or less.

[0021] [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 before the number.

[0022] (First Embodiment) <Silicon Carbide Substrate> First, the configuration of the silicon carbide substrate according to the first embodiment will be described.

[0023] FIG. 1 is a schematic plan view showing the configuration of a silicon carbide substrate according to the first embodiment. As shown in FIG. 1, the silicon carbide substrate 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.

[0024] 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 in which the <11-20> direction is projected 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.

[0025] 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, for example, the 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.

[0026] 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.

[0027] In the silicon carbide substrate 100, a notch 14 is provided. The notch 14 is a notch provided in the silicon carbide substrate 100. The first outer peripheral surface 19 has an arc-shaped portion 18 and a notch portion 17. When viewed perpendicularly to the first main surface 11 (hereinafter also referred to as a plan view), the shape of the arc-shaped portion 18 is arc-shaped. In a plan view, the center A of the silicon carbide substrate 100 is the center of a circle including an arc along the arc-shaped portion 18.

[0028] The notch portion 17 is continuous with the arc-shaped portion 18. The notch portion 17 constitutes the notch 14. In a plan view, the notch portion 17 is, for example, concave along the second direction 102. From another perspective, in a plan view, the notch portion 17 is concave from the circle including the arc along the arc-shaped portion 18 toward the center A. In a plan view, the tangent line of the notch portion 17 is taken as the first virtual line 91.

[0029] The silicon carbide substrate 100 is composed of, for example, hexagonal silicon carbide. The polytype of the hexagonal silicon carbide constituting the silicon carbide substrate 100 is 4H. The silicon carbide substrate 100 may be a conductive substrate or a semi-insulating substrate.

[0030] As shown in FIG. 1, the diameter of the silicon carbide substrate 100 is the first diameter W1. The first diameter W1 may be, for example, 150 mm (6 inches) or more, 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 a plan view, the first diameter W1 is the longest straight-line distance between two different points on the first outer peripheral surface 19.

[0031] 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).

[0032] 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 substrate 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 thickness of the silicon carbide substrate 100 in the third direction 103 is, for example, 1 mm or less. The thickness of the silicon carbide substrate 100 in the third direction 103 may be, for example, 0.5 mm or less, or 0.35 mm or less. The thickness of the silicon carbide substrate 100 in the third direction 103 is, for example, 0.1 mm or more.

[0033] As shown in FIG. 2, the silicon carbide substrate 100 has a first processed and modified portion 15, a second processed and modified portion 16, and a main body portion 10. The first processed and modified portion 15 constitutes a notch portion 17. The first processed and modified portion 15 is a portion that has received processing damage by laser processing. Specifically, the first processed and modified portion 15 is composed of silicon carbide crystals that have been amorphized due to heat generated during laser processing.

[0034] 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 and altered portion 15 in the direction perpendicular to the notch portion 17 is defined as the first thickness H1. The first thickness H1 is, for example, 0.05 mm or less.

[0035] The second machined and altered portion 16 constitutes an arcuate portion 18. The second machined and altered portion 16 is a portion that has received machining damage due to grinding of the single-crystalline silicon carbide on the outer peripheral surface described later. Specifically, the second machined and altered portion 16 is composed of silicon carbide crystals that have been distorted due to grinding of the single-crystalline silicon carbide on the outer peripheral surface.

[0036] As shown in FIG. 2, the thickness of the second machined and altered portion 16 is defined as the second thickness H2. The second thickness H2 is the thickness of the second machined and altered portion 16 in the direction from the arcuate portion 18 toward the center A (see FIG. 1) in a 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.

[0037] The main body portion 10 is a portion that has not received machining damage due to laser processing and machining damage due to grinding of the single-crystalline silicon carbide on the outer peripheral surface. The main body portion 10 is composed of single-crystalline silicon carbide having a normal crystal lattice.

[0038] In a cross-section perpendicular to the first main surface 11 and perpendicular to the first virtual line 91, the main body portion 10 is located between the first machined and altered portion 15 and the second machined and altered portion 16. The main body portion 10 is in contact with each of the first machined and altered portion 15 and the second machined and altered portion 16. The main body portion 10 is surrounded by the first machined and altered portion 15 and the second machined and altered portion 16.

[0039] (Second Embodiment) Next, the configuration of the silicon carbide substrate 100 according to the second embodiment will be described. The silicon carbide substrate 100 according to the second embodiment is different from the silicon carbide substrate 100 according to the first embodiment mainly in that the silicon carbide substrate 100 is chamfered at each of the notch portion 17 and the arc-shaped portion 18, and is substantially the same as the silicon carbide substrate 100 according to the first embodiment in other respects. Hereinafter, the description will focus on the differences from the silicon carbide substrate 100 according to the first embodiment.

[0040] FIG. 3 is a schematic cross-sectional view showing the configuration of the silicon carbide substrate 100 according to the second embodiment. The cross-section shown in FIG. 3 corresponds to the cross-section shown in FIG. 2. As shown in FIG. 3, in a cross-section perpendicular to the first main surface 11 and perpendicular to the first virtual line 91 (see FIG. 1), the notch portion 17 is convex in the direction from the arc-shaped portion 18 toward the notch portion 17. In a cross-section perpendicular to the first main surface 11 and perpendicular to the first virtual line 91, the arc-shaped portion 18 is convex in the direction from the notch portion 17 toward the arc-shaped portion 18.

[0041] In FIG. 3, the broken line indicates the portion removed from the silicon carbide substrate 100 (see FIG. 2) according to the first embodiment. As shown in FIG. 3, in the silicon carbide substrate 100 according to the second embodiment, each of the first processed altered layer 15 and the second processed altered layer 16 is removed. From another perspective, the silicon carbide substrate 100 is constituted by, for example, the main body portion 10.

[0042] By performing chamfering on the notch portion 17, the first processed altered layer 15 is removed. The amount of cutting in the notch portion 17 is defined as the first cutting amount T1. The first cutting amount T1 is the amount of cutting of the silicon carbide substrate 100 in the direction perpendicular to the notch portion 17 in a cross-section perpendicular to the first main surface 11 and perpendicular to the first virtual line 91. The first cutting amount T1 is, for example, 0.1 mm or more.

[0043] By chamfering the arc-shaped portion 18, the second processed and altered portion 16 is removed. The amount of cutting in the arc-shaped portion 18 is defined as the second cutting amount T2. The second cutting amount T2 is the amount of cutting of the silicon carbide substrate 100 in the direction from the arc-shaped portion 18 toward the center A (see FIG. 1) in a 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, 0.1 mm or more.

[0044] Note that the silicon carbide substrate 100 may have a portion damaged by the chamfering process. The portion may constitute the first outer peripheral surface 19. The portion may surround the main body portion 10.

[0045] <Method for manufacturing a silicon carbide substrate> Next, a method for manufacturing the silicon carbide substrate 100 according to the present embodiment will be described. FIG. 4 is a flowchart schematically showing the method for manufacturing the silicon carbide substrate 100 according to the present embodiment. As shown in FIG. 4, the method for manufacturing the silicon carbide substrate 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), a step of forming a silicon carbide wafer by cutting the silicon carbide single crystal (S40), a step of forming a notch portion in the silicon carbide wafer using a laser (S50), a step of performing chamfering on the arc-shaped portion (S60), and a step of performing chamfering on the notch portion (S70).

[0046] First, a step (S10) of preparing a silicon carbide single crystal is performed. FIG. 5 is a cross-sectional schematic view showing the step (S10) of preparing a silicon carbide single crystal. As shown in FIG. 5, a silicon carbide single crystal 200 is prepared. Specifically, for example, by the sublimation method, a polytype 4H silicon carbide single crystal 200 is manufactured. The growth direction of the silicon carbide single crystal 200 is, for example, the same as the third direction 103. The thickness of the silicon carbide single crystal 200 in the third direction 103 is, for example, 10 mm or more. The silicon carbide single crystal 200 has a first end face 21, a second end face 22, and a second outer peripheral face 29.

[0047] The first end face 21 is, for example, convex in the third direction 103. The second end face 22 is opposite to the first end face 21. The second end face 22 is, for example, planar. The first end face 21 is in the third direction 103 with respect to the second end face 22. The second outer peripheral face 29 is continuous with each of the first end face 21 and the second end face 22. The second outer peripheral face 29 is annular. As it moves away from the second end face 22 along the third direction 103, for example, the diameter of the second outer peripheral face 29 increases.

[0048] Next, a step (S20) of grinding the silicon carbide single crystal at the end face is performed. For example, using a grinding wheel (not shown), the silicon carbide single crystal 200 is ground at at least one of the first end face 21 and the second end face 22. Specifically, for example, the silicon carbide single crystal 200 is ground at the first end face 21 so that the first end face 21 becomes planar. At the second end face 22, the silicon carbide single crystal 200 may not be ground.

[0049] In the step (S20) of grinding the silicon carbide single crystal at the end face, the abrasive grains of the grinding wheel are, for example, composed of diamond. The bonding material of the grinding wheel is, for example, a vitrified bond. Compared with the case where the bonding material of the grinding wheel is a metal bond, when the bonding material of the grinding wheel is a vitrified bond, the self-sharpening action of the grinding wheel is promoted. In the step (S20) of grinding the silicon carbide single crystal at the end face, the grit size of the grinding wheel is, for example, #140 or #170.

[0050] Next, a step (S30) of grinding the silicon carbide single crystal on the outer peripheral surface is performed. For example, using a grinding wheel (not shown), the silicon carbide single crystal 200 is ground on the second outer peripheral surface 29. Specifically, as viewed in the third direction 103, the silicon carbide single crystal 200 is ground on the second outer peripheral surface 29 so that the silicon carbide single crystal 200 has a cylindrical shape.

[0051] In the step (S30) of grinding the silicon carbide single crystal on the outer peripheral surface, the abrasive grains of the grinding wheel are composed of, for example, diamond. The binder 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.

[0052] In FIG. 5, the broken line 99 shows the outer shape of the silicon carbide single crystal 200 after the step (S20) of grinding the silicon carbide single crystal on the end face and the step (S30) of grinding the silicon carbide single crystal on the outer peripheral surface. The diameter of the silicon carbide single crystal 200 after the step (S20) of grinding the silicon carbide single crystal on the end face and the step (S30) of grinding the silicon carbide single crystal on the outer peripheral surface is the second diameter W2. The second diameter W2 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 second diameter W2 may be, for example, 400 mm (16 inches) or less.

[0053] Next, a step (S40) of cutting the silicon carbide single crystal is performed. For example, by slicing the silicon carbide single crystal 200 using a wire saw, a silicon carbide wafer 300 is formed. Thus, the silicon carbide wafer 300 is prepared. The configuration of the silicon carbide wafer 300 will be described later.

[0054] Next, a step (S50) of forming a notch portion in the silicon carbide wafer using a laser is performed. FIG. 6 is a schematic diagram showing the step (S50) of forming a notch portion in the silicon carbide wafer using a laser. As shown in FIG. 6, the silicon carbide wafer 300 is irradiated with a laser 80. Specifically, first, a laser processing apparatus (not shown) is prepared. As the laser processing apparatus, for example, a laser marker "MD-F3000" manufactured by Keyence Corporation can be used.

[0055] As shown in FIG. 6, the above-described silicon carbide wafer 300 is prepared. The silicon carbide wafer 300 is a workpiece. The silicon carbide wafer 300 has a third main surface 31 and a third outer peripheral surface 39. When viewed in a direction perpendicular to the third main surface 31, the shape of the third main surface 31 is circular. The third outer peripheral surface 39 is continuous with the third main surface 31. The shape of the third outer peripheral surface 39 is cylindrical.

[0056] The thickness of the silicon carbide wafer 300 in a direction perpendicular to the third main surface 31 is, for example, 1 mm or less. The thickness of the silicon carbide wafer 300 in a direction perpendicular to the third main surface 31 may be, for example, 0.5 mm or less, or 0.35 mm or less. The thickness of the silicon carbide wafer 300 in a direction perpendicular to the third main surface 31 is, for example, 0.1 mm or more.

[0057] Using the laser processing apparatus, the laser 80 is irradiated onto the third main surface 31, for example, along the first arrow B1. Specifically, the laser 80 is irradiated so that the focal point F of the laser 80 is located on the third main surface 31.

[0058] The laser 80 is, for example, a fiber laser, a YAG (Yttrium Aluminum Garnet) laser, or a CO2 laser. The wavelength of the laser 80 is, for example, 1000 nm or more and 11000 nm or less. The wavelength of the laser 80 may be, for example, 1050 nm or more and 1080 nm or more. The wavelength of the laser 80 may be, for example, 10800 nm or less, 10000 nm or less, 5000 nm or less, or 2000 nm or less.

[0059] When using the MD-F3000 as the laser processing apparatus, the laser 80 is a fiber laser doped with ytterbium (Yb). When using the MD-F3000 as the laser processing apparatus, for example, conditions such as a laser power of 80% and a pulse frequency of 60 kHz can be used. The output of the laser is, for example, 30 W.

[0060] FIG. 7 is a schematic plan view showing the process (S50) of forming a notch portion in a silicon carbide wafer using a laser. In FIG. 7, the focus F of the laser 80 irradiated on the silicon carbide wafer 300 is schematically shown using a dashed line. In FIG. 7, the second virtual line 92 indicates the path of the focus F. The length of the second virtual line 92 when viewed perpendicular to the third main surface 31 is the processing length in laser processing. The processing length is, for example, about 5 mm. As shown in FIG. 7, the portion of the silicon carbide wafer 300 surrounded by the third outer peripheral surface 39 and the second virtual line 92 is defined as the removed portion 68.

[0061] The laser 80 is scanned so that the focus F passes through the second virtual line 92. As a result, on the third main surface 31, the silicon carbide wafer 300 is shaved. By scanning the laser 80 a plurality of times, the silicon carbide wafer 300 is cut along the second virtual line 92. Due to the irradiation of the laser 80, heat is generated near the focus F. The portion of the silicon carbide wafer 300 around the second virtual line 92 is amorphized by the heat. From another perspective, the first processed altered layer 15 (see FIG. 2) is formed by the heat generated due to the irradiation of the laser 80.

[0062] The removed portion 68 is separated from the silicon carbide wafer 300. When the removed portion 68 is removed, the notch 14 and the notch portion 17 (see FIG. 1) are formed. Thus, the silicon carbide substrate 100 according to the first embodiment described above is manufactured. From another perspective, the steps of preparing a silicon carbide single crystal (S10), grinding the silicon carbide single crystal at the end face (S20), grinding the silicon carbide single crystal at the outer peripheral face (S30), forming a silicon carbide wafer by cutting the silicon carbide single crystal (S40), and forming a notch portion in the silicon carbide wafer using a laser (S50) constitute a method for manufacturing the silicon carbide substrate 100 according to the first embodiment.

[0063] Next, a chamfering step (S60) is performed on the arc-shaped portion. FIG. 8 is a schematic diagram showing the chamfering step (S60) performed on the arc-shaped portion. As shown in FIG. 8, the silicon carbide substrate 100 is disposed on a support base 86. The support base 86 rotates the silicon carbide substrate 100. The support base 86 is movable along a plane perpendicular to the central axis (first central axis C1) of the silicon carbide substrate 100.

[0064] A first grindstone 81 is prepared. The first grindstone 81 is attached to a first shaft portion 83. The abrasive grains of the first grindstone 81 are constituted by, for example, diamond. The binder of the first grindstone 81 is, for example, a metal bond. When the binder of the first grindstone 81 is a metal bond as compared with the case where the binder is a vitrified bond, the shape accuracy of the silicon carbide substrate 100 can be improved. The grit size of the first grindstone 81 is, for example, #400 or #600. The first shaft portion 83 rotates the first grindstone 81.

[0065] FIG. 9 is a partial cross-sectional schematic view showing the step (S60) of chamfering the arcuate portion. As shown in FIGS. 8 and 9, the first grinding wheel 81 has a first concave surface 71. The first concave surface 71 is the surface that contacts the silicon carbide substrate 100. The first concave surface 71 is concave in a direction from the silicon carbide substrate 100 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.

[0066] As shown in FIGS. 8 and 9, when the support base 86 rotates, the silicon carbide substrate 100 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 100 and the rotation direction of the first grinding wheel 81 are, for example, the same.

[0067] As shown in FIGS. 8 and 9, when the support base 86 moves, the silicon carbide substrate 100 moves. As a result, while the first grinding wheel 81 and the silicon carbide substrate 100 each rotate, the first concave surface 71 and the arcuate portion 18 come into contact. In the arcuate portion 18, the silicon carbide substrate 100 is ground. The amount of material removed from the silicon carbide substrate 100 in the arcuate portion 18 (second amount of material removed T2, see FIG. 3) is, for example, 0.1 mm or more. As described above, the second processed and altered portion 16 is removed.

[0068] Next, the step (S70) of chamfering the notch portion is performed. FIG. 10 is an enlarged plan schematic view showing the step (S70) of chamfering the notch portion. FIG. 11 is a partial cross-sectional schematic view showing the step (S70) of chamfering the notch portion.

[0069] As shown in FIGS. 10 and 11, a second grindstone 82 is prepared. The second grindstone 82 is attached to a second shaft portion 84. The abrasive grains of the second grindstone 82 are made of, for example, diamond. The binder of the second grindstone 82 is, for example, a metal bond. Therefore, as described above, the shape accuracy of the silicon carbide substrate 100 can be improved. The grit size of the second grindstone 82 is, for example, #400 or #600.

[0070] The second shaft portion 84 rotates the second grindstone 82. The second grindstone 82 has a second concave surface 72. The second concave surface 72 is a surface that contacts the silicon carbide substrate 100. The second concave surface 72 is concave in a direction from the silicon carbide substrate 100 toward the central axis (third central axis C3) of the second grindstone 82.

[0071] The minimum diameter of the second grindstone 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. 9).

[0072] As shown in FIG. 10, the maximum width E of the notch portion 17 before chamfering is performed on the notch portion is larger than the second minimum diameter D2 (see FIG. 11) and smaller than the first minimum diameter D1 (see FIG. 9). The maximum width E is the distance between two connection points of the notch portion 17 and the arc-shaped portion 18 in a plan view.

[0073] When the second shaft portion 84 rotates, the second grindstone 82 rotates about the third central axis C3. In the step (S70) of performing chamfering on the notch portion, the silicon carbide substrate 100 is disposed on the support base 86. In the step (S70) of performing chamfering on the notch portion, the silicon carbide substrate 100 does not rotate.

[0074] As shown in FIG. 10, as the silicon carbide substrate 100 moves, the second grinding wheel 82 moves relative to the silicon carbide substrate 100 along the second arrow B2. Specifically, the second grinding wheel 82 moves along the notch portion 17. As shown in FIG. 11, while the second grinding wheel 82 rotates, the second concave surface 72 and the notch portion 17 come into contact with each other. As a result, the silicon carbide substrate 100 is ground at the notch portion 17. Note that the chamfering step (S70) for the notch portion may be performed before the chamfering step (S60) for the arcuate portion.

[0075] The amount of material removed from the silicon carbide substrate 100 at the notch portion 17 (first amount of material removed T1, see FIG. 3) is, for example, 0.1 mm or more. As a result, the first processed altered layer 15 is removed. Thus, the silicon carbide substrate 100 (see FIG. 3) according to the above-described second embodiment is manufactured.

[0076] Next, the operation and effect of the method for manufacturing a silicon carbide substrate according to the present embodiment will be described. As a method for forming a notch portion in a substrate made of silicon or the like, there is a method of forming the notch portion using a grinding wheel. In this method, the grinding wheel and the substrate come into contact with each other when forming the notch portion. Compared with a substrate made of silicon or the like, a substrate made of silicon carbide (silicon carbide substrate) is likely to crack, chip, and develop cracks because silicon carbide is a hard material. In particular, as the thickness of the silicon carbide substrate decreases, cracking, chipping, and cracking are more likely to occur. Therefore, when forming a notch portion using a grinding wheel, cracks, chipping, and cracking may occur in the silicon carbide substrate.

[0077] According to the method for manufacturing the silicon carbide substrate 100 according to the present embodiment, a notch portion is formed in the silicon carbide wafer 300 using a laser. In laser processing, a tool such as a grinding wheel does not contact the silicon carbide wafer 300. Therefore, the occurrence of cracks in the silicon carbide substrate 100 can be suppressed as compared with the case of forming a notch portion using a grinding wheel.

[0078] In laser processing, since a tool such as a grinding wheel does not contact the silicon carbide wafer 300, the occurrence of each of cracking and chipping in the silicon carbide substrate 100 can be suppressed as compared with the case where a notch is formed using a grinding wheel.

[0079] As a binder of the grinding wheel used when forming a notch, a 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, due to the wear of the abrasive grains, the frequency of replacing the grinding wheel increases. Particularly when forming a notch in a silicon carbide wafer, since silicon carbide is a hard material, the wear of the abrasive grains becomes excessively fast. Therefore, the consumption of relatively expensive grinding wheels increases excessively. As a result, the cost required to manufacture the silicon carbide substrate 100 increases.

[0080] According to the method for manufacturing the silicon carbide substrate 100 according to the present embodiment, the laser 80 is used when forming the notch. Therefore, a grinding wheel is not required for forming the notch. Accordingly, the cost required to manufacture the silicon carbide substrate 100 can be reduced as compared with the case where a notch is formed in the silicon carbide wafer 300 using a grinding wheel.

[0081] The method for manufacturing the silicon carbide substrate 100 according to the present embodiment includes a step (S30) of grinding a silicon carbide single crystal on an outer peripheral surface. Therefore, in the method for manufacturing the silicon carbide substrate 100 according to the present embodiment, the outer peripheral surface of the silicon carbide single crystal 200 is ground, and a notch is formed in the silicon carbide wafer 300 using a laser. For this reason, 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 substrate 100 can be suppressed by using a laser.

[0082] When processing the outer peripheral surface of the silicon carbide single crystal 200 using a laser, amorphous silicon carbide is formed in a portion of the silicon carbide single crystal 200 close to the second outer peripheral surface 29. For example, when slicing the silicon carbide single crystal 200 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-amorphous silicon carbide. In this case, the shape accuracy of the silicon carbide wafer 300 formed by slicing deteriorates. As a result, the shape accuracy of the silicon carbide substrate 100 deteriorates. According to the method for manufacturing the silicon carbide substrate 100 according to the present embodiment, silicon carbide does not become amorphous in a portion of the silicon carbide single crystal 200 close to the second outer peripheral surface 29. Thereby, it is possible to suppress deterioration of the shape accuracy of the silicon carbide substrate 100.

[0083] When forming a notch portion using a grinding stone, the grinding stone comes into contact with the silicon carbide wafer 300. In this case, the silicon carbide wafer 300 is pulled by the grinding stone along the moving direction and the rotational direction of the grinding stone, so that processing strain occurs in the silicon carbide wafer 300. A portion of the silicon carbide wafer 300 where processing strain has occurred may remain in the silicon carbide substrate 100 manufactured using the silicon carbide wafer 300. Specifically, even after chamfering the first outer peripheral surface 19 of the silicon carbide substrate 100, a portion where processing strain has occurred may remain. When an epitaxial layer is formed on the silicon carbide substrate 100, it is considered that defects in the epitaxial layer increase due to the processing strain remaining in the silicon carbide substrate 100.

[0084] According to the method for manufacturing the silicon carbide substrate 100 according to the present embodiment, a notch portion is formed in the silicon carbide wafer 300 using a laser. Therefore, it is possible to suppress the remaining of processing strain in the manufactured silicon carbide substrate 100. As a result, it is considered that an increase in defects in the epitaxial layer formed on the silicon carbide substrate 100 can be suppressed.

[0085] The manufacturing method of the silicon carbide substrate 100 according to this embodiment has a chamfering process (S70) for the notch portion. Therefore, the first processed and altered portion 15 formed by the formation of the notch portion can be removed. As a result, when an epitaxial layer is formed on the silicon carbide substrate 100, an increase in defects in the epitaxial layer due to the first processed and altered portion 15 can be suppressed.

[0086] According to the manufacturing method of the silicon carbide substrate 100 according to this embodiment, in the chamfering process, the amount of material removed from the notch portion 17 is 0.1 mm or more. Therefore, the first processed and altered portion 15 can be removed more reliably.

[0087] In addition, in the above description, the configuration of the manufacturing method of the silicon carbide substrate 100 in which each of the first processed and altered portion 15 and the second processed and altered portion 16 is completely removed has been described. However, the configuration of the manufacturing method of the silicon carbide substrate 100 according to the present disclosure is not limited to the above configuration. Specifically, a part of each of the first processed and altered portion 15 and the second processed and altered portion 16 may remain without being removed. The first amount of material removed T1 may be smaller than the first thickness H1, for example. The second amount of material removed T2 may be smaller than the second thickness H2, for example.

[0088] 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 meanings equivalent to the claims and all modifications within the scope are included.

Explanation of Reference Numerals

[0089] 10 Body portion 11 First main surface 12 Second main surface 14 Notch 15 First processed and altered portion 16 Second processed and altered portion 17 Notch portion 18 Arc-shaped portion 19 First outer peripheral surface 21 First end face 22 Second end face 29 Second outer peripheral surface 31 Third main surface 39 Third outer peripheral surface 68 Removed portion 71 First concave surface 72 Second concave surface 80 Laser 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 99 Dashed line 100 Silicon carbide substrate 101 First direction 102 Second direction 103 Third direction 200 Silicon carbide single crystal 300 Silicon carbide wafer A Center B1 First arrow B2 Second arrow C1 First central axis C2 Second central axis C3 Third central axis D1 First minimum diameter D2 Second minimum diameter E Maximum width F Focus H1 First thickness H2 Second 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 having a polytype of 4H is provided, 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 silicon carbide wafer by cutting the single-crystalline silicon carbide; A method for manufacturing a silicon carbide substrate, comprising a step of forming a notch portion on the silicon carbide wafer using a laser.

2. The method for manufacturing a silicon carbide substrate according to claim 1, further comprising a step of chamfering the notch portion.

3. The method for manufacturing a silicon carbide substrate according to claim 2, wherein in the chamfering process, the amount of material removed at the notch portion is 0.1 mm or more.

4. A step of preparing a silicon carbide wafer having a polytype of 4H; A method for manufacturing a silicon carbide substrate, comprising a step of forming a notch portion on the silicon carbide wafer using a laser.

5. The method for manufacturing a silicon carbide substrate according to claim 4, further comprising a step of chamfering the notch portion.

6. The method for manufacturing a silicon carbide substrate according to any one of claims 1 to 5, wherein the wavelength of the laser is 1000 nm or more and 11000 nm or less.

7. The laser is a fiber laser, a YAG laser, or a CO ２ laser, and is a method for manufacturing a silicon carbide substrate according to any one of claims 1 to 5.

8. In the step of forming the notch portion on the silicon carbide wafer using the laser, the notch portion is formed by scanning the laser a plurality of times. The method for manufacturing a silicon carbide substrate according to any one of claims 1 to 5.

9. After the step of grinding the outer peripheral face, the diameter of the single-crystalline silicon carbide is 150 mm or more. The method for manufacturing a silicon carbide substrate according to any one of claims 1 to 3.

10. After the step of grinding the outer peripheral face, the diameter of the single-crystalline silicon carbide is 200 mm or more. The method for manufacturing a silicon carbide substrate according to claim 9.

11. The thickness of the silicon carbide wafer is 1 mm or less. The method for manufacturing a silicon carbide substrate according to any one of claims 1 to 5.

Images