JP2019188510A - Method for manufacturing silicon carbide substrate - Google Patents

Abstract

To provide a method for manufacturing a silicon carbide substrate which is capable of efficiently slicing an ingot of silicon carbide single crystal, and suppressing an occurrence of detection impossible state of a deflection amount in the middle of slicing.SOLUTION: A method for manufacturing a silicon carbide substrate comprises: a process of preparing an ingot 2 made of silicon carbide single crystal; a process of slicing the ingot 2 along a surface orthogonal to a first direction along the central axis of the ingot 2 by a wire 14 on the surface of which abrasive grains are fixed; a process of measuring a deflection amount of the wire 14 in a non-contact manner by a displacement sensor 15; and a process of feedback controlling the slicing process corresponding to the deflection amount. The slicing process is performed by relatively moving the ingot 2 along a second direction D2 orthogonal to the first direction against the wire 14 that makes reciprocating motion along an extending direction of the wire while rocking within a plane orthogonal to the first direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for manufacturing a silicon carbide substrate.

  Conventionally, a method for slicing a silicon carbide single crystal substrate described in Patent Document 1 (Japanese Patent Laid-Open No. 2015-47673) is known. In the slicing method described in Patent Literature 1, a fixed abrasive that reciprocates along an X direction, in which an ingot of a silicon carbide single crystal whose central axis extends along the Y direction extends in the X direction perpendicular to the Y direction. It slices by moving along the Z direction orthogonal to the X direction and the Y direction toward the grain wire. In the slicing method described in Patent Document 1, the slicing is controlled in accordance with the amount of deflection in the Z direction of the fixed abrasive wire measured by a digital camera.

  As another slicing method, a slicing method described in Patent Document 2 (Japanese Patent Laid-Open No. 2007-326167) is known. Note that the slicing method described in Patent Document 2 is a slicing method for a silicon (Si) single crystal substrate.

JP 2015-47673 A JP 2007-326167 A

  In the method for slicing a silicon carbide single crystal substrate described in Patent Document 1, since the fixed abrasive wire does not swing in a plane including the X direction and the Z direction, an ingot of a silicon carbide single crystal having high hardness is efficiently formed. It is difficult to slice. Further, in the method for slicing a silicon carbide single crystal substrate described in Patent Document 1, the lens of the digital camera is contaminated by the coolant supplied at the time of slicing, which may make it difficult to measure the amount of deflection during slicing. There is.

  The present invention has been made in view of the above-mentioned problems of the prior art. More specifically, the present invention provides a method for manufacturing a silicon carbide substrate capable of efficiently slicing a silicon carbide single crystal ingot and suppressing the occurrence of undetectable deflection during slicing. To do.

  A method for manufacturing a silicon carbide substrate according to one aspect of the present invention includes a step of preparing an ingot made of a silicon carbide single crystal, and a first direction along the central axis of the ingot by a wire having abrasive grains fixed on the surface. A step of slicing the ingot along the surface, a step of measuring the deflection amount of the wire in a non-contact manner by a displacement sensor, and a step of performing feedback control of the step of slicing according to the deflection amount. In the slicing step, the ingot is moved along the second direction orthogonal to the first direction toward the wire reciprocating along the extending direction of the wire while swinging in a plane orthogonal to the first direction. This is done by relatively moving.

  According to the method for manufacturing a silicon carbide substrate according to one aspect of the present invention, it is possible to efficiently slice an ingot of a silicon carbide single crystal, and it is possible to suppress the occurrence of undetectable deflection amount during slicing. .

2 is a top view of the slicing device 1. FIG. 1 is a front view of a slicing device 1. FIG. FIG. 4 is a schematic diagram showing a swinging motion of a wire 14. 2 is a cross-sectional view of a wire 14. 6 is a schematic diagram for explaining a deflection amount δy of a wire 14; FIG. It is process drawing which shows the manufacturing method of the silicon carbide substrate which concerns on embodiment. It is a graph which shows the relationship between the threshold value set in threshold value setting process S2, and the curvature of the silicon carbide substrate after a slice.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed.

  (1) A method for manufacturing a silicon carbide substrate according to an aspect of the present invention includes a step of preparing an ingot made of a silicon carbide single crystal, and a first along the central axis of the ingot by a wire having abrasive grains fixed to the surface. A step of slicing the ingot along a plane orthogonal to the direction, a step of measuring the amount of deflection of the wire in a non-contact manner by a displacement sensor, and a step of performing feedback control of the step of slicing according to the amount of deflection. In the slicing step, the ingot is moved along the second direction orthogonal to the first direction toward the wire reciprocating along the extending direction of the wire while swinging in a plane orthogonal to the first direction. This is done by relatively moving.

  According to the silicon carbide substrate manufacturing method of (1) above, a silicon carbide single crystal ingot can be efficiently sliced, and the occurrence of undetectable deflection during the slicing can be suppressed.

  (2) In the method for manufacturing a silicon carbide substrate according to (1), the measurement of the deflection amount may be performed when the swing angle is 0 °.

  According to the silicon carbide substrate manufacturing method of (2) above, the amount of deflection can be measured more reliably.

  (3) In the method for manufacturing a silicon carbide substrate according to (2), the relative moving speed of the ingot with respect to the wire in the second direction may be changed in accordance with the amount of deflection.

  According to the silicon carbide substrate manufacturing method of (3) above, the warp of the silicon carbide substrate can be improved without complicating the configuration of the slicing apparatus.

  (4) The method for manufacturing a silicon carbide substrate according to (3) may further include a step of setting a threshold value. The relative moving speed of the ingot is controlled so as to increase when the deflection amount is smaller than the threshold value in the feedback control step, and the relative moving speed becomes smaller when the deflection amount is larger than the threshold value. It may be controlled as follows.

  According to the silicon carbide substrate manufacturing method of (4) above, the warp of the silicon carbide substrate can be improved while performing efficient slicing.

  (5) In the method for manufacturing a silicon carbide substrate according to (4), the step of feedback control is performed when the slice position is greater than or equal to the first value and less than or equal to the second value, and the slice position is less than the first value and It may not be performed when the second value is exceeded.

  According to the silicon carbide substrate manufacturing method of (5) above, the warp of the silicon carbide substrate can be improved while performing efficient slicing.

  (6) In the method for manufacturing a silicon carbide substrate according to the above (1) to (5), the abrasive grains may be diamond abrasive grains.

  According to the silicon carbide substrate manufacturing method of (6) above, an ingot of a silicon carbide single crystal can be efficiently sliced, and occurrence of undetectable deflection during the slicing can be suppressed.

  (7) In the method for manufacturing a silicon carbide substrate according to (1) to (6), the displacement sensor may be an eddy current displacement sensor.

  According to the silicon carbide substrate manufacturing method of (7) above, it is possible to efficiently slice a silicon carbide single crystal ingot and to suppress the occurrence of undetectable deflection during slicing.

[Details of the embodiment of the present invention]
Next, details of the embodiment of the present invention 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 repeated description will not be repeated. In the crystallographic description in this specification, individual planes are indicated by (), and aggregate planes are indicated by {}. A negative crystallographic index is usually expressed by adding a “−” (bar) above the number. However, in the present specification, a negative exponent in crystallography is expressed by attaching a negative sign in front of a number.

(Slicing device used for manufacturing method of silicon carbide substrate according to embodiment)
Below, the structure of the slicing apparatus 1 used for the manufacturing method of the silicon carbide substrate which concerns on embodiment is demonstrated.

  FIG. 1 is a top view of the slicing apparatus 1. FIG. 2 is a front view of the slicing apparatus 1. As shown in FIGS. 1 and 2, the slicing device 1 includes an ingot fixing base 11, a first guide roller 12, a second guide roller 13, a wire 14, and a displacement sensor 15.

  The ingot fixing base 11 is a part that holds the ingot 2. The ingot 2 is attached to the ingot fixing base 11 by being bonded with an adhesive, for example. The ingot 2 has a cylindrical shape. Hereinafter, the direction along the central axis 2a of the ingot 2 is referred to as a first direction D1. The ingot fixing base 11 is configured to be relatively movable along a second direction D2 orthogonal to the first direction D1.

  The first guide roller 12 and the second guide roller 13 have a columnar shape extending along the first direction D1. The first guide roller 12 and the second guide roller 13 are spaced apart from each other in the third direction D3. The third direction D3 is orthogonal to the first direction D1 and the second direction D2.

  The first guide roller 12 is configured to be rotatable around the central axis 12a. The first guide roller 12 has an outer peripheral surface 12b. The second guide roller 13 is configured to be rotatable around the central axis 13a. The second guide roller 13 has an outer peripheral surface 13b. Grooves (not shown) are formed in the outer peripheral surface 12b and the outer peripheral surface 13b along the direction intersecting the central axis 12a and the central axis 13a.

  The wire 14 is stretched between the first guide roller 12 and the second guide roller 13 by being wound along grooves formed on the outer peripheral surface 12b and the outer peripheral surface 13b. The wire 14 rotates between the first guide roller 12 and the second guide roller 13 by rotating the first guide roller 12 and the second guide roller 13 forward and backward around the central shaft 12a and the central shaft 13a. Reciprocate along the extending direction of.

  The first guide roller 12 and the second guide roller 13 have a positive rotation amount per cycle around the central axis 12a and the central axis 13a, and the first guide roller 12 and the second guide roller 13 have the central axis 12a and the central axis. By setting more than the counter-rotation amount per cycle around 13a, the portions of the wire 14 that are not subjected to friction with the ingot 2 are sequentially supplied to the contact area with the ingot 2. Hereinafter, the supply amount of the wire 14 that has not undergone friction with the ingot 2 per cycle may be referred to as a “new wire supply amount”.

  The first guide roller 12 and the second guide roller 13 draw an arc in the plane in which the central axis 12a and the central axis 13a are orthogonal to the first direction D1 (in the plane including the second direction D2 and the third direction D3). Is configured to be swingable.

  FIG. 3 is a schematic diagram showing the swinging motion of the wire 14. As shown in FIG. 3, the wire 14 swings by swinging the central axis 12a and the central axis 13a so as to draw an arc in a plane perpendicular to the first direction D1. An angle formed by a straight line connecting the centers of the first guide roller 12 and the second guide roller 13 and the third direction D3 is defined as a swing angle θ. For example, the wire 14 is swung so that the swing angle θ is in the range of −10 ° to + 10 °.

  FIG. 4 is a cross-sectional view of the wire 14. As shown in FIG. 4, the wire 14 is a fixed abrasive wire. More specifically, the wire 14 has a core wire 14a, a surface layer 14b, and abrasive grains 14c.

  The core wire 14a is a linear member. The core wire 14a is formed of, for example, a piano wire. The abrasive grains 14c are fixed by being partially embedded in the surface layer 14b covering the outer peripheral surface of the core wire 14a. The surface layer 14b is, for example, a Ni (nickel) plating layer. The abrasive grains 14c are, for example, diamond abrasive grains.

  The displacement sensor 15 measures the deflection amount δy of the wire 14. The deflection amount δy is measured by the displacement sensor 15 in a non-contact manner. FIG. 5 is a schematic diagram for explaining the deflection amount δy of the wire 14. The amount of deflection δy is the distance between the position of the wire 14 when the ingot 2 is not in contact (indicated by a dotted line in FIG. 5) and the position of the wire 14 when the ingot 2 is in contact. It is the maximum value. For the displacement sensor 15, for example, an eddy current displacement sensor is used. A plurality of displacement sensors 15 may be provided. The displacement sensor 15 is arrange | positioned at the side of the ingot 2, for example. When the number of the displacement sensors 15 is plural, the displacement sensors 15 may be arranged on both sides of the ingot 2.

(Method for Manufacturing Silicon Carbide Substrate According to Embodiment)
Below, the manufacturing method of the silicon carbide substrate which concerns on embodiment is demonstrated.

  FIG. 6 is a process diagram illustrating the method for manufacturing the silicon carbide substrate according to the embodiment. As shown in FIG. 6, the method for manufacturing the silicon carbide substrate according to the embodiment includes a preparation step S1, a threshold setting step S2, a slicing step S3, a deflection amount measuring step S4, and a feedback control step S5. ing.

  In preparation process S1, preparation of ingot 2 is performed. Ingot 2 is composed of a silicon carbide single crystal. The preparation of the ingot 2 is performed by epitaxially growing a silicon carbide single crystal on a seed crystal composed of the silicon carbide single crystal by, for example, a sublimation method.

  The diameter of the ingot 2 is 100 mm or more and 150 mm or less, for example. The plane orthogonal to the central axis 2 a of the ingot 2 may be parallel to the (0001) plane of the silicon carbide single crystal constituting the ingot 2. The plane orthogonal to the central axis 2 a of the ingot 2 may be inclined with respect to the (0001) plane of the silicon carbide single crystal constituting the ingot 2. The inclination angle in this case is 4 °, for example.

  In the threshold setting step S2, a threshold is set. This threshold is related to the deflection amount δy, as will be described later.

  In the slicing step S3, the ingot 2 is sliced. In the slicing step S3, the ingot 2 is sliced by the wire 14. More specifically, this slice gives the second ingot 2 to the wire 14 that is reciprocating along the extending direction of the wire 14 while swinging in a plane orthogonal to the first direction D1. This is done by relatively moving along the direction D2.

  In the deflection amount measuring step S4, the deflection amount δy is measured. The measurement of the deflection amount δy is preferably performed when the swing angle θ is 0 °. The deflection amount δy may be an average value during one cycle of swinging of the wire 14. The measurement of the deflection amount δy is preferably performed every cycle of the swing of the wire 14. In the feedback control step S5, the slicing step S3 is controlled based on the measured deflection amount δy.

  In the feedback control step S5, feedback control of the slicing step S3 is performed according to the deflection amount δy. For example, in the feedback control step S5, the moving speed of the ingot 2 in the second direction D2 (hereinafter sometimes referred to as “feeding speed”) is controlled according to the deflection amount δy.

  More specifically, in the feedback control step S5, when the deflection amount δy is smaller than a predetermined threshold value, the feed rate of the ingot 2 is controlled to increase, and the deflection amount δy is larger than the threshold value. The feed speed of the ingot 2 is controlled to decrease. That is, in the feedback control step S5, when the deflection amount δy is smaller than the threshold value, control is performed so that the feed speed of the ingot 2 after control becomes larger than the feed speed of the ingot 2 when the deflection amount δy is measured. When the deflection amount δy is larger than the threshold value, the feed speed of the ingot 2 after control is controlled to be smaller than the feed speed of the ingot 2 when the deflection amount δy is measured.

  However, in the feedback control step S5, parameters other than the feed speed of the ingot 2 may be controlled according to the deflection amount δy. For example, in the feedback control step S5, the new line supply amount may be controlled according to the deflection amount δy. In the feedback control step S5, the movement of the ingot 2 along the first direction D1 may be controlled according to the deflection amount δy.

  The slicing step S3 may be divided into a first period, a second period, and a third period. The second period is performed after the first period. The third period is performed after the second period. The deflection amount measuring step S4 and the feedback control step S5 are performed when the slicing step S3 is in the second period, but may not be performed when the slicing step S3 is in the first period and the third period.

  The first period is a section from the start of the slice until the slice position reaches the first value. The second period is a section where the slice position is greater than or equal to the first value and less than the second value. The third period is a period after the slice position becomes the second value until the slice of the ingot 2 is completed. The first value is 5 mm, for example. The second value is, for example, a value obtained by dividing 5 mm from the diameter of the ingot 2. The slice position is a distance from a position where the ingot 2 is sliced by the wire 14 to a position where the ingot 2 is sliced by the wire 14.

(Effect of manufacturing method of silicon carbide substrate according to embodiment)
Below, the effect of the manufacturing method of the silicon carbide substrate concerning an embodiment is explained.

  In the method for manufacturing the silicon carbide substrate according to the embodiment, the slice of the ingot 2 reciprocates along the extending direction of the wire 14 while swinging in a plane orthogonal to the first direction D1. On the other hand, it is performed by relatively moving the ingot 2 along the second direction D2. Therefore, according to the method for manufacturing a silicon carbide substrate according to the embodiment, a load can be applied intensively to a portion where wire 14 and ingot 2 are in contact with each other. Therefore, according to the method for manufacturing a silicon carbide substrate according to the embodiment, a silicon carbide single crystal ingot having high hardness can be efficiently sliced.

  In the method for manufacturing the silicon carbide substrate according to the embodiment, the deflection amount δy is measured by the displacement sensor 15 in a non-contact manner. Therefore, according to the method for manufacturing a silicon carbide substrate according to the embodiment, measurement of the deflection amount δy during slicing due to the influence of coolant supplied during slicing is not likely to occur.

  In the method for manufacturing the silicon carbide substrate according to the embodiment, since the wire 14 is oscillating in a plane orthogonal to the first direction D1, the value of the deflection amount δy changes every moment. Therefore, in the method for manufacturing a silicon carbide substrate according to the embodiment, when the deflection amount δy is measured when the swing angle θ is 0 °, the deflection amount δy can be more reliably measured.

  The warpage amount of the silicon carbide substrate is proportional to the deflection amount δy. The deflection amount δy is proportional to the relative moving speed of the ingot 2 with respect to the wire 14. That is, the amount of warpage of the silicon carbide substrate is proportional to the feed speed of ingot 2. Therefore, in the method for manufacturing a silicon carbide substrate according to the embodiment, when feedback control is performed such that the feed rate of ingot 2 changes according to the deflection amount δy, the warp of the silicon carbide substrate can be reduced.

  The warp of the silicon carbide substrate can be reduced by moving the ingot 2 along the first direction D1 in accordance with the amount of deflection δy. However, there is a configuration for moving the ingot 2 along the first direction D1. Necessary. On the other hand, in the method for manufacturing a silicon carbide substrate according to the embodiment, when feedback control is performed so that the feed rate of the ingot 2 changes according to the deflection amount δy, the silicon carbide substrate is not added without adding an additional configuration. Warpage can be reduced.

  As the deflection amount δy increases, the processing speed increases because the wire 14 is strongly pressed against the ingot 2. On the other hand, as described above, the warp of the silicon carbide substrate increases as the deflection amount δy increases. Therefore, in the method for manufacturing a silicon carbide substrate according to the embodiment, when the deflection amount δy is larger than a predetermined threshold value, the feed rate of the ingot 2 is controlled to be small, and the deflection amount δy is larger than the threshold value. In the case where the feed rate of the ingot 2 is controlled so as to increase when it is small, both improvement in productivity of the silicon carbide substrate and reduction in warpage can be achieved.

  In the first period and the third period of the slicing step S3, slicing of the peripheral portion of the silicon carbide substrate proceeds. In the peripheral portion of the silicon carbide substrate, the demand for warpage is moderate as compared with the central portion of the silicon carbide substrate. Therefore, in the method for manufacturing a silicon carbide substrate according to the embodiment, when the slice position is greater than or equal to the first value and less than the second value, the required level regarding the warp of the silicon carbide substrate is satisfied without performing the feedback control step S5. Cheap.

Examples of the silicon carbide substrate according to the embodiment will be described below.
Table 1 shows the specifications of the ingot 2 used in the examples. As shown in Table 1, in the examples, the ingot 2 having a diameter of 100 mm and a thickness of 10 mm was used. Note that the plane perpendicular to the first direction D1 is inclined by 4 ° with respect to the (0001) plane of the silicon carbide single crystal constituting the ingot 2. Further, the polytype of the silicon carbide single crystal constituting the ingot 2 is 4H.

  Table 2 shows the slice conditions. As shown in Table 2, in the example, the traveling speed of the wire 14 was 1500 m / min, and the tension of the wire 14 was 45N. In the embodiment, the constant speed time in the normal rotation direction of the first guide roller 12 and the second guide roller 13 is 60 seconds, and the constant speed time in the reverse direction of the first guide roller 12 and the second guide roller 13 is 50 seconds. Second to 60 seconds. In the example, the slice thickness was 500 μm. In the example, the diameter of the wire 14 was 240 μm to 250 μm. In this wire 14, the core wire 14a had a diameter of 180 μm, the surface layer 14b was an electrodeposited nickel layer, and the abrasive grains 14c were diamond abrasive grains having a particle diameter of 30 μm to 40 μm.

  In the embodiment, the feed speed of the ingot 2 increases when the deflection amount δy is smaller than the threshold value set in the threshold setting step S2, and the ingot 2 feeds when the deflection amount δy is larger than the threshold value. Control was performed to reduce the speed.

  FIG. 7 is a graph showing the relationship between the threshold set in threshold setting step S2 and the warp of the silicon carbide substrate after slicing. In FIG. 7, the horizontal axis is a threshold (unit: mm) regarding the deflection amount δy set in the threshold setting step S2, and the vertical axis is the warp (unit: μm) of the silicon carbide substrate after slicing.

  As shown in FIG. 7, the value of warpage of the silicon carbide substrate after slicing was reduced by reducing the threshold value set in threshold value setting step S2. Further, the average processing speed is increased by increasing the threshold value set in the threshold value setting step S2. As described above, it was experimentally confirmed that the processing speed can be improved by appropriately adjusting the threshold value set in the threshold value setting step S2 so as not to exceed the required warpage of the silicon carbide substrate.

  The embodiments disclosed herein are illustrative in all respects and should not be considered as restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

DESCRIPTION OF SYMBOLS 1 Slice apparatus 11 Ingot fixing stand 12 1st guide roller 12a Central axis 12b Outer peripheral surface 13 Second guide roller 13a Central axis 13b Outer peripheral surface 14 Wire 14a Core wire 14b Surface layer 14c Abrasive grain 15 Displacement sensor 2 Ingot 2a Central axis D1 1st Direction D2 Second direction D3 Third direction S1 Preparation step S2 Threshold setting step S3 Slice step S4 Deflection measurement step S5 Feedback control step θ Swing angle δy Deflection amount

Claims (7)

Preparing an ingot made of a silicon carbide single crystal;
Slicing the ingot along a surface orthogonal to a first direction along the central axis of the ingot, with a wire having abrasive grains fixed to the surface;
Measuring the amount of deflection of the wire in a non-contact manner with a displacement sensor;
Feedback control of the slicing step according to the deflection amount,
The slicing step includes a second direction orthogonal to the first direction toward the wire reciprocating along the extending direction of the wire while swinging in a plane orthogonal to the first direction. A method for manufacturing a silicon carbide substrate, which is performed by relatively moving the ingot along the axis.   The method of manufacturing a silicon carbide substrate according to claim 1, wherein the measurement of the amount of deflection is performed when the swing angle becomes 0 °.   The silicon carbide substrate according to claim 2, wherein, in the feedback control step, a relative moving speed of the ingot with respect to the wire in the second direction is controlled to change according to the amount of deflection. Method. Further comprising setting a threshold;
In the feedback control step,
When the amount of deflection is smaller than the threshold value, the relative movement speed is controlled to increase,
The method for manufacturing a silicon carbide substrate according to claim 3, wherein when the amount of deflection is larger than the threshold value, the relative movement speed is controlled to be small.   The step of feedback control is performed when a slice position is not less than a first value and not more than a second value, and is not performed when the slice position is less than the first value and exceeds the second value. Item 5. A method for manufacturing a silicon carbide substrate according to Item 4.   The said abrasive grain is a manufacturing method of the silicon carbide substrate of any one of Claims 1-5 which is a diamond abrasive grain.   The said displacement sensor is a manufacturing method of the silicon carbide substrate of any one of Claims 1-6 which is an eddy current type displacement sensor.

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