JP2020011853A - Manufacturing method for recycled substrate - Google Patents

Abstract

To provide a manufacturing method for a recycled substrate capable of suppressing generation of cracks, chips or the like in a process for recycling a silicon carbide epitaxial substrate.SOLUTION: A manufacturing method for a recycled substrate includes a preparation step S1 of a silicon carbide epitaxial substrate having a silicon carbide substrate that includes a first principal plane, a second principal plane opposite to the first principal plane, a side plane, and an inclined plane that is connected to the first principal plane and the side plane and inclines toward the second principal plane as going toward the side plane from the first principal plane and having a first silicon carbide epitaxial layer formed on the first principal plane and the inclined plane. The manufacturing method further includes a removal step S4 of the first silicon carbide epitaxial layer on the first principal plane and a polishing step S5 of the first principal plane. The step S5 includes at least a first step S51 of mechanical polishing. When a distance between the first principal plane and an edge of the surface of the first silicon carbide epitaxial layer at a side plane side in a direction of toward the second principal plane from the first principal plane is less than a threshold value, the first step S51 is conducted after a beveling step S3 so that the distance becomes the threshold value or longer.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a method for manufacturing a recycled substrate.

  Conventionally, for example, a silicon carbide epitaxial substrate described in JP-A-2006-52991 (Patent Document 1) is known. The silicon carbide epitaxial substrate described in Patent Document 1 has a silicon carbide substrate and an epitaxial layer formed on one main surface of the silicon carbide substrate.

JP-A-2006-52991

  An object of the present disclosure is to provide a method of manufacturing a recycled substrate that can suppress generation of cracks, chips, and the like in a process of recycling a silicon carbide epitaxial substrate.

  A method for manufacturing a recycled substrate according to an aspect of the present disclosure includes a first main surface, a second main surface opposite to the first main surface, a side surface, a first main surface and a side surface, A silicon carbide substrate including an inclined surface inclined toward a second principal surface from the first principal surface toward the side surface, and a first silicon carbide epitaxial layer formed on the first principal surface and the inclined surface. A step of preparing a silicon carbide epitaxial substrate having the same, a step of removing the first silicon carbide epitaxial layer on the first main surface, and a step of polishing the first main surface.

  Polishing includes at least first mechanical polishing. When the distance between the first main surface and the end on the side surface side of the surface of the first silicon carbide epitaxial layer in the direction from the first main surface to the second main surface is smaller than the threshold, the distance is set to be equal to or larger than the threshold. The first mechanical polishing is performed after beveling the silicon carbide epitaxial substrate. When the distance is equal to or greater than the threshold, the first mechanical polishing is performed without performing beveling on the silicon carbide epitaxial substrate.

  According to the above, it is possible to suppress the occurrence of cracks, chips, and the like in the process of regenerating the silicon carbide epitaxial substrate.

It is a flowchart showing the manufacturing method of the reproduction board concerning an embodiment. FIG. 3 is a cross sectional view of silicon carbide epitaxial substrate 10 prepared in preparation step S1. 3 is an outline of the silicon carbide epitaxial substrate 10. FIG. 3 is a cross-sectional view of silicon carbide epitaxial substrate 10 after a beveling step S3. It is a mimetic diagram showing beveling processing in beveling process S3. FIG. 5 is a cross sectional view of silicon carbide epitaxial substrate 10 after an epitaxial layer removing step S4. FIG. 5 is a cross-sectional view of silicon carbide epitaxial substrate 10 after an epitaxial growth step S6. FIG. 11 is a cross-sectional view of silicon carbide epitaxial substrate 10 in a case where epitaxial layer removing step S4 is performed without performing beveling step S3. It is a graph which shows the relationship between distance L2 and a defective rate in a polishing test.

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

  (1) A method of manufacturing a recycled substrate according to an embodiment of the present disclosure includes a first main surface, a second main surface opposite to the first main surface, a side surface, and a first main surface and a side surface; A silicon carbide substrate including an inclined surface inclined from the first main surface toward the side surface toward the second main surface, and a first silicon carbide epitaxial formed on the first main surface and the inclined surface. A step of preparing a silicon carbide epitaxial substrate having a layer, a step of removing the first silicon carbide epitaxial layer on the first main surface, and a step of polishing the first main surface. Polishing includes at least first mechanical polishing. When the distance between the first main surface and the end on the side surface side of the surface of the first silicon carbide epitaxial layer in the direction from the first main surface to the second main surface is smaller than the threshold, the distance is set to be equal to or larger than the threshold. The first mechanical polishing is performed after beveling the silicon carbide epitaxial substrate. When the distance is equal to or greater than the threshold, the first mechanical polishing is performed without performing beveling on the silicon carbide epitaxial substrate.

  According to the method for manufacturing a recycled substrate of the above (1), it is possible to suppress the occurrence of cracks, chips and the like in the process of recycling the silicon carbide epitaxial substrate.

  (2) In the method for manufacturing a recycled substrate according to the above (1), the threshold value may exceed 48 μm.

  According to the method for manufacturing a recycled substrate of the above (2), it is possible to suppress the occurrence of cracks, chips, and the like in the process of recycling the silicon carbide epitaxial substrate.

  (3) In the method for manufacturing a recycled substrate according to the above (1), the threshold value may be more than 48 μm and less than 57 μm.

  According to the method of manufacturing a recycled substrate of the above (3), it is possible to improve the productivity of the recycled substrate while suppressing the occurrence of cracks, chips, and the like in the process of recycling the silicon carbide epitaxial substrate.

  (4) In the method for manufacturing a recycled substrate according to the above (1), the threshold value may be 57 μm or more.

  According to the method for manufacturing a recycled substrate of the above (3), it is possible to further suppress the occurrence of cracks, chips, and the like in the process of recycling the silicon carbide epitaxial substrate.

  (5) The method for producing a recycled substrate according to the above (1) to (4) may further include a step of performing second mechanical polishing on the second main surface. The first mechanical polishing and the second mechanical polishing may be performed simultaneously.

  According to the method of manufacturing a reclaimed substrate of the above (5), even if mechanical polishing is performed in a mode of easily causing cracks, chips, and the like called double-sided polishing, cracks, chips, etc., in the process of regenerating the silicon carbide epitaxial substrate are not affected. Generation can be suppressed.

  (6) In the method of manufacturing a recycled substrate according to any one of (1) to (5), the polishing may further include chemical mechanical polishing performed after the first mechanical polishing.

  (7) The method for manufacturing a recycled substrate according to (6) may further include a step of growing a second silicon carbide epitaxial layer on the first main surface after chemical mechanical polishing.

[Details of Embodiment of the Present Disclosure]
Next, details of an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference characters, and overlapping description will not be repeated.

(Method of Manufacturing Recycled Substrate According to Embodiment)
Hereinafter, a method for manufacturing a recycled substrate according to the embodiment will be described.

  FIG. 1 is a process chart showing a method for manufacturing a recycled substrate according to the embodiment. As shown in FIG. 1, the method for manufacturing a recycled substrate according to the embodiment includes a preparing step S1, a dimension measuring step S2, a beveling step S3, an epitaxial layer removing step S4, a polishing step S5, and an epitaxial growing step. S6.

  In preparation step S1, silicon carbide epitaxial substrate 10 is prepared. FIG. 2 is a cross-sectional view of silicon carbide epitaxial substrate 10 prepared in preparation step S1. As shown in FIG. 2, silicon carbide epitaxial substrate 10 has silicon carbide substrate 20 and first silicon carbide epitaxial layer 30.

  Silicon carbide substrate 20 is formed of a single crystal of silicon carbide. For example, silicon carbide substrate 20 is formed of a single crystal of hexagonal silicon carbide having a polytype of 4H. Silicon carbide substrate 20 has first main surface 21, first inclined surface 22, side surface 23, second main surface 24, and second inclined surface 25.

  The first inclined surface 22 is continuous with both the first main surface 21 and the side surface 23. The first inclined surface 22 is inclined downward (toward the second main surface 24) from the first main surface 21 side toward the side surface 23 side. That is, the distance between the end of the first inclined surface 22 on the first main surface 21 side and the second main surface 24 is larger than the distance between the end of the first inclined surface 22 on the side surface 23 side and the second main surface 24. Has become. The second main surface 24 is a surface opposite to the first main surface 21. The second inclined surface 25 is continuous with both the second main surface 24 and the side surface 23. The second inclined surface 25 is inclined upward (toward the first main surface 21) from the second main surface 24 side toward the side surface 23 side. That is, the distance between the end of the second inclined surface 25 on the second principal surface 24 side and the first principal surface 21 is larger than the distance between the end of the second inclined surface 25 on the side surface 23 side and the first principal surface. ing.

  First silicon carbide epitaxial layer 30 is formed on first main surface 21 and first inclined surface 22. First silicon carbide epitaxial layer 30 is formed of a single crystal of silicon carbide. First silicon carbide epitaxial layer formed on first main surface 21 has thickness T.

  In dimension measurement step S2, the dimension of silicon carbide epitaxial substrate 10 is measured. More specifically, in dimension measurement step S2, the surface of first silicon carbide epitaxial layer 30 formed on first main surface 21 in the direction from first main surface 21 to second main surface Distance L1 (see FIG. 2), which is the distance between the surface of first silicon carbide epitaxial layer 30 formed on one inclined surface 22 and the end on the side surface 23 side, is measured. The dimension measurement step S2 is performed by the following method using SEP-1401 (manufactured by Kobelco Research Institute).

  In the measurement of distance L1, a light corresponding to the shape of silicon carbide epitaxial substrate 10 is projected on a screen by irradiating silicon carbide epitaxial substrate 10 with light horizontally from the side. The outline of silicon carbide epitaxial substrate 10 is determined from the shape of the shadow of silicon carbide epitaxial substrate 10 projected on the screen.

  FIG. 3 is an outline of the silicon carbide epitaxial substrate 10. The end of the outline of silicon carbide epitaxial substrate 10 in the radial direction is point A in FIG. A perpendicular passing through the point A is defined as a straight line LA. The boundary between side surface 23 and the surface of first silicon carbide epitaxial layer 30 formed on first inclined surface 22 is point B in FIG. The tangent at the point B of the outline of the silicon carbide epitaxial substrate 10 is a straight line LB. The boundary between the surface of first silicon carbide epitaxial layer 30 formed on first main surface 21 and the surface of first silicon carbide epitaxial layer 30 formed on first inclined surface 22 is point C in FIG. is there. The tangent at the point C of the outline of the silicon carbide epitaxial substrate 10 is a straight line LC.

  The position where the angle θ1 between the straight line LB and the straight line LA is 20 ° is defined as a point B. The position where the angle θ2 between the straight line LC and the straight line LA is 77.5 ° is defined as a point C. The angles θ1 and θ2 have positive values when the straight line LB and the straight line LC rotate counterclockwise in FIG. 3 with respect to the straight line LA. Then, by measuring the distance between point B and point C in the thickness direction of silicon carbide epitaxial substrate 10, distance L1 is determined.

  By subtracting the thickness T from the measured distance L1, the first silicon carbide formed on the first main surface 21 and the first inclined surface 22 in the direction from the first main surface 21 to the second main surface 24 The distance L2, which is the distance from the end of the surface of the epitaxial layer 30 on the side surface 23 side, is calculated. The distance between the ridge line of the first main surface 21 and the first inclined surface 22 and the side surface 23 is defined as a distance L3.

  In beveling step S3, beveling on silicon carbide epitaxial substrate 10 is performed. The beveling step S3 is performed when the distance L2 is less than the threshold. If the distance L2 is equal to or greater than the threshold, the beveling step S3 is not performed. FIG. 4 is a cross-sectional view of silicon carbide epitaxial substrate 10 after the beveling step S3. The beveling step S3 is performed such that the distance L2 after the beveling step S3 is equal to or larger than the above threshold. The beveling step S3 is performed so that the distance L3 increases after the beveling step S3.

  FIG. 5 is a schematic diagram showing the beveling process in the beveling step S3. As shown in FIG. 4, the beveling step S3 is performed using a grindstone 40. That is, the beveling step S3 is performed by pressing the silicon carbide epitaxial substrate 10 against the grindstone 40 rotating around the central axis A1. At this time, by rotating silicon carbide epitaxial substrate 10 around central axis A2, beveling is performed over the entire circumference of silicon carbide epitaxial substrate 10.

  Note that distance L2 in silicon carbide epitaxial substrate 10 after beveling step S3 may be calculated by performing dimension measurement step S2 after beveling step S3 is performed. When the distance L2 calculated as a result is smaller than the threshold value, the beveling step S3 may be performed again.

  The above threshold exceeds 48 μm. The threshold may be greater than 48 μm and less than 57 μm. The above threshold may be 57 μm or more. Note that the above threshold value is not more than １ ／ of the thickness of silicon carbide epitaxial substrate 10 (the distance between first main surface 21 and second main surface 24).

  FIG. 6 is a cross-sectional view of silicon carbide epitaxial substrate 10 after the epitaxial layer removing step S4. As shown in FIG. 6, in epitaxial layer removing step S4, first silicon carbide epitaxial layer 30 is removed. In epitaxial layer removing step S4, at least first silicon carbide epitaxial layer 30 formed on first main surface 21 is removed. Thereby, the first main surface 21 is exposed. The removal of first silicon carbide epitaxial layer 30 is performed, for example, by grinding.

  When the beveling step S3 is not performed, the first silicon carbide epitaxial layer 30 on the first main surface 21 is removed by performing the epitaxial layer removing step S4. The first silicon carbide epitaxial layer 30 may remain.

  The polishing step S5 includes a first step S51, as shown in FIG. The polishing step S5 may further include a second step S52. The second step S52 is performed after the first step S51.

  In the first step S51, the first main surface 21 is polished by mechanical polishing (Mechanical Polishing). In the first step S51, both the first main surface 21 and the second main surface 24 may be polished by mechanical polishing. In this case, the mechanical polishing of the first main surface 21 and the mechanical polishing of the second main surface 24 are performed simultaneously (double-side polishing). This mechanical polishing is performed using, for example, diamond abrasive grains.

  In the second step S52, the first main surface 21 is polished by chemical mechanical polishing (Chemical Mechanical Polishing). In the second step S52, the first main surface 21 and the second main surface 24 may be polished by chemical mechanical polishing. This chemical mechanical polishing is performed using, for example, colloidal silica or the like.

  FIG. 7 is a cross-sectional view of silicon carbide epitaxial substrate 10 after the epitaxial growth step S6. As shown in FIG. 7, in epitaxial growth step S6, second silicon carbide epitaxial layer 50 is formed. The second silicon carbide epitaxial layer 50 is epitaxially grown on the first main surface 21 by, for example, CVD (Chemical Vapor Deposition). As described above, the manufacturing process of the recycled substrate according to the embodiment is completed.

(Effect of Manufacturing Method of Recycled Substrate According to Embodiment)
Hereinafter, effects of the method for manufacturing a recycled substrate according to the embodiment will be described.

  Regeneration of the silicon carbide epitaxial substrate 10 is performed when a defect occurs in the first silicon carbide epitaxial layer 30 (for example, when the impurity concentration or defect density in the first silicon carbide epitaxial layer 30 does not satisfy a predetermined standard). Done in Therefore, when regenerating silicon carbide epitaxial substrate 10, it is necessary to temporarily remove at least first silicon carbide epitaxial layer 30 formed on first main surface 21.

  FIG. 8 is a cross-sectional view of silicon carbide epitaxial substrate 10 when epitaxial layer removing step S4 is performed without performing beveling step S3. As shown in FIG. 8, when beveling step S3 is not performed, first silicon carbide epitaxial layer 30 on first main surface 21 is removed in epitaxial layer removing step S4, so that silicon carbide epitaxial substrate is removed. In FIG. 10, the portion where beveling is performed becomes smaller. As a result, in first step S51 (mechanical polishing), cracks, chips, and the like are likely to occur in silicon carbide epitaxial substrate 10.

  In order to suppress the occurrence of cracks, chips and the like in silicon carbide epitaxial substrate 10 in first step S51, beveling should be performed on silicon carbide epitaxial substrate 10 prior to epitaxial layer removing step S4. Is valid. However, performing beveling on all the silicon carbide epitaxial substrates 10 is not preferable from the viewpoint of manufacturing cost.

  According to the findings found by the inventors of the present application, the distance L2 is a dominant factor regarding whether or not the silicon carbide epitaxial substrate 10 is cracked or chipped in the first step S51. Therefore, when the distance L2 is equal to or more than the threshold, the first step S51 is performed without performing the beveling step S3, and when the distance L2 is less than the threshold, the first step S51 is performed after performing the beveling step S3. By performing S51, the occurrence of cracks, chips, and the like in silicon carbide epitaxial substrate 10 can be suppressed. By doing so, it is not necessary to perform beveling on all of the silicon carbide epitaxial substrates 10, so that manufacturing costs can be reduced.

  In the first step S51, when the first main surface 21 and the second main surface 24 are simultaneously subjected to mechanical polishing (in the case of double-side polishing), the silicon carbide epitaxial substrate 10 is not restrained during the mechanical polishing. The substrate 10 is liable to crack, chip, or the like. According to the method for manufacturing a reclaimed substrate according to the embodiment, even if mechanical polishing is performed in such a manner that double-side polishing easily causes cracks, chips, and the like, cracks, chips, and the like are suppressed in silicon carbide epitaxial substrate 10. be able to.

(Polishing test)
Hereinafter, a polishing test performed to confirm the effect of the method of manufacturing a recycled substrate according to the embodiment will be described.

  In this polishing test, when the first step S51 was performed by the double-side polishing method, the number of silicon carbide epitaxial substrates 10 in which chipping, cracking and chipping occurred was investigated. The epitaxial layer removing step S4 is performed on the silicon carbide epitaxial substrate 10 subjected to the polishing test, but the beveling step S3 is not performed. Further, in the polishing test, the value of the distance L2 changes in a range from 12 μm to 151 μm. The results of this polishing test are shown in Table 1 below.

  FIG. 9 is a graph showing the relationship between the distance L2 and the defect rate in the polishing test. In FIG. 9, the horizontal axis represents the distance L2 (unit: μm), and the vertical axis represents the defect rate (unit: percent). The defect rate is a value obtained by dividing the number of silicon carbide epitaxial substrates 10 in which at least one of chipping, cracking and chipping has occurred by the number of silicon carbide epitaxial substrates 10 subjected to the polishing test, and multiplying the result by 100.

  As shown in Table 1 and FIG. 9, when the distance L2 was 37 μm or less, the defect rate was 100%. When the distance L2 was 48 μm, the failure rate was 67%, but when the distance L2 was 57 μm, the failure rate was 0%. As described above, the defect rate was remarkably improved before the distance L2 exceeded 48 μm and reached 57 μm. When the distance L2 was 57 μm or more, the defect rate was 0%.

  From the above test results, a threshold value is set so as to exceed 48 μm (a threshold value is set so as to be more than 48 μm and less than 57 μm, or a threshold value is set so that it is equal to or more than 57 μm). When the distance is less than the threshold value, the first step S51 is performed after performing the beveling step S3, and when the distance L2 is equal to or more than the threshold, the first step S51 is performed without performing the beveling step S3. It has been experimentally shown that cracking, chipping and chipping are suppressed in the course of regeneration of the silicon carbide epitaxial substrate 10.

  The embodiment disclosed this time is an example in all respects, and should not be considered as restrictive. The scope of the present invention is defined by the terms of the claims, rather than the embodiments described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Reference Signs List 10 silicon carbide epitaxial substrate 20 silicon carbide substrate 21 first main surface 22 first inclined surface 23 side surface 24 second principal surface 25 second inclined surface 30 first silicon carbide epitaxial layer 40 grinding wheel 50 second silicon carbide epitaxial layers L1, L2 , L3 Distance S1 Preparation step S2 Dimension measurement step S3 Beveling step S4 Epitaxial layer removal step S5 Polishing step S6 Epitaxial growth step S51 First step S52 Second step T Thickness

Claims (7)

A first main surface, a second main surface opposite to the first main surface, a side surface, a continuation of the first main surface and the side surface, and heading from the first main surface side to the side surface side. A silicon carbide substrate including an inclined surface inclined toward the second principal surface according to the following formula; and a silicon carbide epitaxial substrate having a first silicon carbide epitaxial layer formed on the first principal surface and the inclined surface. The step of preparing,
Removing the first silicon carbide epitaxial layer on the first main surface;
Polishing the first main surface,
The polishing includes at least a first mechanical polishing,
When the distance between the first main surface and the end of the side surface side of the surface of the first silicon carbide epitaxial layer in the direction from the first main surface toward the second main surface is less than a threshold value, the distance Beveling is performed on the silicon carbide epitaxial substrate so that is equal to or more than the threshold value, and then the first mechanical polishing is performed,
When the distance is equal to or greater than the threshold, the first mechanical polishing is performed without performing beveling on the silicon carbide epitaxial substrate.   The method of claim 1, wherein the threshold value is greater than 48 μm.   The method of claim 1, wherein the threshold is more than 48 μm and less than 57 μm.   The method of claim 1, wherein the threshold value is equal to or greater than 57 μm. A step of performing a second mechanical polishing on the second main surface;
5. The method of claim 1, wherein the first mechanical polishing and the second mechanical polishing are performed simultaneously. 6.   The method for manufacturing a recycled substrate according to claim 1, wherein the polishing further includes chemical mechanical polishing performed after the first mechanical polishing.   The method of manufacturing a recycled substrate according to claim 6, further comprising a step of growing a second silicon carbide epitaxial layer on the first main surface after the chemical mechanical polishing.

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