Method for manufacturing silicon carbide wafers

Abstract

This suppresses the occurrence of cracks and chips in SiC ingots and SiC wafers. [Solution] Prepare a SiC ingot 10 made of SiC, having one surface 10a, another surface 10b opposite to surface 10a, and a side surface 10c connecting surface 10a and surface 10b; form a temporary notch 11 on the side surface 10c of the SiC ingot 10, with the bottom 11a being a curved portion; cut the SiC ingot 10 to obtain a SiC wafer with the temporary notch 11 formed thereon; and widen the temporary notch 11 of the SiC wafer to form a notch 101.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a SiC wafer composed of silicon carbide (hereinafter also referred to as SiC).

Background Art

[0002] Conventionally, for example, in Patent Document 1, after preparing a SiC ingot composed of SiC, a groove-shaped notch serving as a crystal orientation mark is formed on the side surface of the SiC ingot, and then the SiC ingot is cut into a thin disk shape to obtain a SiC wafer. In this case, the notch is a substantially V-shaped groove whose width becomes narrower toward the bottom. In other words, the notch has a shape with a corner at the bottom.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when forming a substantially V-shaped groove as the notch, stress concentration occurs at the bottom of the notch when cutting the SiC wafer, which may cause cracks, chips, etc. in the SiC ingot or SiC wafer.

[0005] An object of the present disclosure is to provide a method for manufacturing a SiC wafer that can suppress the occurrence of cracks and chips in the SiC ingot and SiC wafer.

Means for Solving the Problems

[0006] According to one aspect of this disclosure, a method for manufacturing a SiC wafer involves preparing a SiC ingot (10) made of SiC and having one face (10a), another face opposite to the first face (10b), and a side surface (10c) connecting the first and second faces; forming a temporary notch (11) on the side surface of the SiC ingot, with the bottom (11a) being a curved portion; cutting the SiC ingot to obtain a SiC wafer (100) with the temporary notch formed thereon; and widening the temporary notch of the SiC wafer to form a notch (101).

[0007] According to this method, a temporary notch with a curved bottom is formed in the SiC ingot, and after cutting the SiC ingot, the temporary notch is widened to form a notch in the SiC wafer. Therefore, when cutting the SiC ingot, stress concentration can be suppressed compared to when a notch with a corner is formed at the bottom, and cracks and chips in the SiC ingot and SiC wafer can be suppressed.

[0008] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0009] [Figure 1A] This diagram shows the manufacturing process of SiC wafers. [Figure 1B] This figure shows the manufacturing process of SiC wafers, following Figure 1A. [Figure 1C] This figure shows the manufacturing process of SiC wafers, following Figure 1B. [Figure 1D] This figure shows the manufacturing process of SiC wafers, following Figure 1C. [Figure 1E] This figure shows the manufacturing process of SiC wafers, following Figure 1D. [Figure 2] Figure 1B is a plan view of the process, showing the SiC ingot viewed from one side. [Figure 3] Figure 1D is a plan view of the process, showing the SiC ingot viewed from one side. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described below with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numerals.

[0011] (First Embodiment) A method for manufacturing a SiC wafer according to the first embodiment will be described with reference to Figures 1A to 1E. First, as shown in Figure 1A, a SiC ingot 10 made of SiC is prepared. In this embodiment, the SiC ingot 10 is cylindrical in shape, having one face 10a, another face 10b opposite to face 10a, and a side surface 10c connecting face 10a and face 10b. In addition, in this embodiment, face 10a of the SiC ingot 10 is a (0001) face having the <1-100> direction and the <11-20> direction. However, the SiC ingot 10 may be configured such that, for example, face 10a has an off-angle of a predetermined inclination angle with respect to the (0001) face. The off-angle is, for example, an off-angle of 1 degree or more and 8 degrees or less.

[0012] Next, as shown in Figure 1B, a temporary notch 11 is formed on the side surface 10c of the SiC ingot 10. In this embodiment, the temporary notch 11 is formed on the side surface 10c of the SiC ingot 10 that is perpendicular to the <1-100> direction. The temporary notch 11 is formed continuously from one surface 10a to the other surface 10b of the SiC ingot 10. That is, the temporary notch 11 is formed so that there is no unformed portion between one surface 10a and the other surface 10b of the side surface 10c of the SiC ingot 10 that is perpendicular to the <1-100> direction.

[0013] In this embodiment, when forming the temporary notch 11, a disc-shaped grinding wheel 30 having one surface 30a, another surface 30b opposite to the first surface 30a, and a side surface 30c connecting the first surface 30a and the other surface 30b is used to form the temporary notch 11. Specifically, the grinding wheel 30 in this embodiment has a roughly drum-like shape with a bulge in the central part of the side surface 30c between the first surface 30a and the other surface 30b. The bulge in the central part of the side surface 30c of the grinding wheel 30 is curved. The grinding wheel 30 is not particularly limited, but for example, one of the following may be used as abrasive grains: diamond, boron carbide powder (i.e., B4C), green silicon carbide (i.e., GC), etc., and one of the following may be used as a bonding agent: vitrified, metal, resin, etc. Furthermore, the grinding wheel 30 has a lower grit than the grinding wheel 40 used when forming the notch 101, which will be described later. In other words, the grinding wheel 30 used is one in which the surface roughness Ra on the wall surface of the temporary notch 11 is greater than the surface roughness Ra on the wall surface of the notch 101, which will be described later.

[0014] When forming the temporary notch 11, as shown in Figures 1B and 2, the grinding wheel 30 is rotated in the circumferential direction, and the grinding wheel 30 is brought into contact with the SiC ingot 10 so that the circumferential direction (i.e., the direction of rotation) is aligned with the thickness direction of the SiC ingot 10, thereby forming the temporary notch 11. When forming the temporary notch 11, for example, pitch machining or step machining, which is performed at predetermined intervals, may be employed.

[0015] The temporary notch 11 is formed such that its depth d1 is shallower than the depth d2 of the notch 101 described later, and its opening angle θ1 is narrower than the opening angle θ2 of the notch 101 described later. In the temporary notch 11 and the notch 101, depths d1 and d2 refer to the lengths in the direction from the opening side toward the bottom, and opening angles θ1 and θ2 refer to the angles of the opening. Furthermore, the temporary notch 11 is formed such that its bottom 11a in the depth direction has curvature. In other words, the temporary notch 11 is formed such that its bottom 11a in the depth direction is a rounded curved portion. The temporary notch 11 is formed such that, for example, its surface roughness Ra is 1.0 μm or more.

[0016] In the process of FIG. 1B, although not particularly shown, beveling may be performed so that the boundary between the one surface 10a and the side surface 10c, and the boundary between the other surface 10b and the side surface 10c have a chamfered R shape. When performing the beveling process, either forming the temporary notch 11 or performing the beveling process may be carried out first.

[0017] Next, as shown in FIG. 1C, the SiC ingot 10 is cut to form a thin disk-shaped SiC wafer 100 having a one surface 100a and the other surface 100b opposite to the one surface 100a. For cutting the SiC ingot 10, wire saw cutting, electrical discharge machining that intermittently generates plasma discharge for cutting, laser machining that forms a modified layer by irradiating a laser for cutting, etc. are employed.

[0018] At this time, the bottom 11a in the depth direction of the temporary notch 11 formed in the SiC ingot 10 is a curved portion. Therefore, when cutting the SiC ingot 10, compared with the case where a notch having a corner at the bottom 11a is formed, the occurrence of stress concentration can be suppressed, and the occurrence of cracks, chips, etc. in the SiC ingot 10 and the SiC wafer 100 can be suppressed.

[0019] Subsequently, as shown in FIGS. 1D and 3, a notch 101 is formed in the SiC wafer 100 cut from the SiC ingot 10. In this embodiment, a columnar grindstone 40 is used to form the notch 101. Specifically, the grindstone 40 is composed of any one of diamond, boron carbide powder, green silicon carbide, etc. as abrasive grains, and any one of vitrified, metal, resin, etc. as a bonding material. Also, the grindstone 40 used is larger than the number of the grindstone 30 used when forming the temporary notch 11.

[0020] When forming the notch 101, the grinding wheel 40 is rotated in the circumferential direction, and while pressing the grinding wheel 40 against the temporary notch 11 in a state where the circumferential direction (i.e., the rotation direction) is along the plane direction of the SiC wafer 100, it is displaced as shown by the arrow A in FIG. 3 to widen the temporary notch 11 and form the notch 101. For example, the notch 101 is formed such that the depth d2 is about 0.8 to 1.2 mm and the opening angle is about 85 to 95°.

[0021] Since the notch 101 is formed by widening the temporary notch 11 as described above, the depth d2 is deeper than the depth d1 of the temporary notch 11, and the opening angle θ2 is wider than the opening angle θ1 of the temporary notch 11. Also, in this embodiment, since the grit size of the grinding wheel 40 is larger than that of the grinding wheel 30, the surface roughness Ra of the notch 101 is made smaller than the surface roughness Ra of the temporary notch 11, for example, less than 1.0 μm. And the notch 101 is formed by widening the temporary notch 11, but for example, it may have a shape with a corner at the bottom.

[0022] And in this step, chamfering is also performed so that the boundary between the one surface 100a and the side surface 100c, and the boundary between the other surface 100b and the side surface 100c become a chamfered R shape. Note that either forming the notch 101 or performing the chamfering may be done first.

[0023] Thereafter, as shown in FIG. 1E, the SiC wafer 100 is manufactured by performing grinding, polishing, CMP (abbreviation for Chemical Mechanical Polishing), cleaning, etc. on the SiC wafer 100 as necessary.

[0024] According to the embodiment described above, a temporary notch 11 with a curved bottom portion 11a is formed in the SiC ingot 10, and after cutting the SiC ingot 10, the temporary notch 11 is widened to form a notch 101 in the SiC wafer 100. Therefore, when cutting the SiC ingot 10, stress concentration can be suppressed compared to the case where a notch with a corner is formed at the bottom, and cracks, chips, etc., in the SiC ingot 10 and SiC wafer 100 can be suppressed.

[0025] (1) In this embodiment, when forming the temporary notch 11, the surface roughness is made greater than when forming the notch 101. Therefore, the manufacturing time when forming the temporary notch 11 can be easily shortened.

[0026] (2) In this embodiment, when forming the temporary notch 11, the temporary notch 11 is formed using a grinding wheel 30 in which the central portion between one side 30a and the other side 30b of the side surface 30c is bulging. Therefore, a temporary notch 11 in which the bottom portion 11a is curved can be easily formed.

[0027] (Other embodiments) This disclosure is described in accordance with embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and idea of ​​this disclosure.

[0028] For example, in the first embodiment described above, when forming the temporary notch 11, the temporary notch 11 may be formed by fixed abrasive wire machining or by wire electrical discharge machining.

[0029] Furthermore, in the first embodiment described above, the depth d2 and aperture angle θ2 of the notch 101 in the SiC wafer 100 can be changed as appropriate.

[0030] In addition, when indicating the orientation of a crystal, a bar (-) should ideally be placed above the desired number. However, due to the limitations on expression imposed by electronic filing, a bar is placed before the desired number in this specification. [Explanation of Symbols]

[0031] 10 SiC ingots 10a one side 10b Other side 11 Temporary Notch 100 SiC wafers 101 Notches

Claims

1. A method for manufacturing silicon carbide wafers, A silicon carbide ingot (10) is prepared, which is made of silicon carbide and has one face (10a), another face opposite to the first face (10b), and a side (10c) connecting the first face and the other face. A temporary notch (11) is formed on the side surface of the silicon carbide ingot, with the bottom portion (11a) being a curved portion. The silicon carbide ingot is cut to obtain a silicon carbide wafer (100) in which the temporary notch is formed. A method for manufacturing a silicon carbide wafer, comprising: widening the temporary notch of the silicon carbide wafer to form a notch (101); and

2. A method for manufacturing a silicon carbide wafer according to claim 1, wherein the formation of the temporary notch and the formation of the notch are such that the surface roughness of the temporary notch is greater than the surface roughness of the notch.

3. The method for manufacturing a silicon carbide wafer according to claim 1 or 2, wherein, in forming the temporary notch, a grinding wheel (30) is prepared which has one surface (30a), another surface (30b) opposite to the one surface, and a side surface (30c) connecting the one surface and the other surface, and the central part of the side surface between the one surface and the other surface is bulging, and the grinding wheel is brought into contact with the silicon carbide ingot while rotating the grinding wheel in the circumferential direction of the one surface, so that the circumferential direction is in line with the thickness direction of the silicon carbide ingot, thereby forming the temporary notch.

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