JP2019034862A - Method for manufacturing silicon carbide epitaxial substrate - Google Patents

Abstract

To provide a silicon carbide epitaxial substrate capable of suppressing the occurrence of a linear defect on the surface of an epitaxial layer.SOLUTION: A method for manufacturing a silicon carbide epitaxial substrate comprises steps of: preparing a silicon carbide substrate 10; detecting a defect point being a depression or projection existing on the main surface 10A of the substrate 10; checking the total length used as the total of a line segment corresponding to a defect point group linearly arranged in defect points on the main surface; and forming epitaxial layers 60 and 70 on the main surface 10A on which it is checked that the total length is equal to or less than a predetermined threshold value.SELECTED DRAWING: Figure 1

Description

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

  A semiconductor device including a silicon carbide (SiC) layer is known. This semiconductor device prepares a silicon carbide epi substrate in which an epitaxial layer made of silicon carbide (hereinafter also referred to as an “epi layer”) is formed by epitaxial growth on a silicon carbide substrate, and forms a device region in the epi layer. It can be manufactured by forming an electrode or the like on the epi layer.

  High surface smoothness is required for the silicon carbide substrate used for the above applications. A method for obtaining a silicon carbide substrate having high surface smoothness is described in Patent Document 1, for example. Patent Document 1 discloses that a silicon carbide substrate having high surface smoothness can be obtained by polishing a silicon carbide substrate using a specific polishing liquid and a polishing pad.

Japanese Patent Laying-Open No. 2015-57864

  In a silicon carbide epi substrate, it is required to suppress the occurrence of linear defects (scratches) on the epi layer surface as much as possible. Some linear defects on the surface of the epi layer are caused by defects existing on the surface of the silicon carbide substrate. For example, when a linear defect exists on the surface of the silicon carbide substrate, a linear defect corresponding to the defect on the substrate surface is likely to occur on the epilayer surface. In order to suppress the occurrence of linear defects on the epilayer surface, the linear defects present on the surface of the silicon carbide substrate are detected before the formation of the epilayer, and the surface of the silicon carbide substrate is polished as necessary. Is done.

  On the other hand, a linear defect may occur at a corresponding location on the surface of the epi layer, although it is a location where no clear linear defect has been confirmed on the surface of the silicon carbide substrate. In order to reduce the linear defects that become apparent after the formation of the epi layer, the cause of the linear defects is specified, the surface state of the silicon carbide substrate surface is appropriately managed, and the linear defects on the epi layer surface are There is a demand to suppress the occurrence.

  Then, it aims at providing the manufacturing method of the silicon carbide epi substrate which can manufacture the silicon carbide epi substrate by which generation | occurrence | production of the linear defect in the epi layer surface was suppressed.

  A method for manufacturing a silicon carbide epi-substrate of the present application includes a step of preparing a silicon carbide substrate having a main surface, a step of detecting a defect point that is a concave portion or a convex portion existing on the main surface, Among them, a step of confirming the total length, which is the sum of the lengths of the line segments corresponding to the defect point groups arranged in a straight line, in the main surface, and the main surface whose total length is confirmed to be equal to or less than a predetermined threshold Forming an epitaxial layer thereon.

  According to the method for manufacturing a silicon carbide epi substrate, it is possible to provide a silicon carbide epi substrate in which the occurrence of linear defects on the epi layer surface is suppressed.

It is a flowchart which shows the procedure of the manufacturing method of a silicon carbide epi substrate. It is a perspective view which shows the structure of a silicon carbide substrate. It is a schematic sectional drawing which shows the structure of a silicon carbide substrate. It is a schematic diagram which shows the defect point which exists in a silicon carbide substrate and its main surface. It is a schematic diagram for demonstrating the method of determining total length. It is a schematic diagram for demonstrating the method of determining total length. It is a schematic diagram for demonstrating the method of determining total length. It is a schematic diagram for demonstrating the method of determining total length. It is a schematic diagram for demonstrating the method of determining total length. It is a schematic diagram for demonstrating the method of determining total length. It is a schematic diagram which shows an effective belt-shaped area | region. It is a schematic diagram which shows the effective strip | belt-shaped area | region on the main surface of a silicon carbide substrate. It is a schematic sectional drawing which shows the structure of a silicon carbide epi substrate.

[Description of Embodiment of Present Invention]
First, embodiments of the present invention will be listed and described. The method of manufacturing a silicon carbide epi-substrate of the present application includes a step of preparing a silicon carbide substrate made of silicon carbide and having a main surface, a step of detecting a defect point that is a concave portion or a convex portion existing on the main surface, and a defect point Among them, a step of confirming the total length, which is the sum of the lengths of the line segments corresponding to the defect point group arranged in a straight line, in the main surface, and the main length confirmed to be equal to or less than a predetermined threshold. Forming an epitaxial layer on the surface.

  When an epitaxial layer made of silicon carbide is formed by epitaxial growth on the main surface of the silicon carbide substrate, the state of the epi layer is affected by the surface state of the main surface of the silicon carbide substrate. For example, when a linear defect (scratch) exists on the main surface of the silicon carbide substrate, the linear defect is easily formed on the surface of the formed epi layer. However, the occurrence of linear defects in the epi layer is not limited to the case where linear defects occur on the main surface of the silicon carbide substrate. In some cases, a linear defect becomes apparent when an epi layer is formed in spite of the fact that a linear defect is not confirmed on the surface of the silicon carbide substrate.

  The present inventors have found that the presence of a defect point group having a specific regularity on the main surface of a silicon carbide substrate is one of the causes of linear defects that are manifested in the epilayer. By detecting the presence of such a defect point group having regularity and reducing the number thereof, the number of occurrences of linear defects in the epi layer can be reduced. Furthermore, the surface state of the silicon carbide substrate is appropriately managed by confirming the total length, which is the sum of the lengths of the line segments corresponding to the defect point groups arranged in a straight line, within the main surface of the silicon carbide substrate. However, a silicon carbide epi substrate can be manufactured.

  In addition, by forming an epitaxial layer on the main surface whose total length is confirmed to be equal to or less than a predetermined threshold value, it is possible to manufacture a silicon carbide epi substrate in which the occurrence of linear defects is suppressed.

  In the step of checking the total length, a straight belt-like region including any first defect point among the defect points and a second defect point having a distance from the first defect point of 10 μm to 600 μm is set. From the first defect point side and the first defect point in the direction connecting the first defect point and the second defect point in the straight band region of the straight band region. A linear strip formed by sequentially extending to the other defect point on the condition that the other defect point exists within a distance range of 10 μm or more and 600 μm or less toward the opposite side to the second defect point. The effective strip region is extracted, the length of the effective strip region in the direction connecting the first defect point and the second defect point is obtained as the length of the line segment, and the effective strip region is determined as the total length. The effective belt-like region is extracted over the entire main surface so that the defect points used for this purpose do not overlap. Corresponding to the extracted effective band regions may be obtaining the sum of the length of the line segment. By doing in this way, the defect point group which has the above-mentioned specific regularity can be detected more appropriately.

  The width of the straight strip region set in the step of confirming the total length may be 20 μm. By setting the straight band-like region having a width of 20 μm, the defect point group having the specific regularity described above can be detected more accurately.

  In the step of confirming the total length, the effective band-shaped region may be set so as to include five or more defect points. By doing in this way, the defect group which has the above-mentioned specific regularity can be detected more appropriately.

  In the step of confirming the total length, the total length of line segments having a length of 1 mm or more may be set as the total length. By doing in this way, the said total length can be determined more appropriately.

  In the step of detecting a defect point, a defect point that is a recess having a depth of 10 nm or more from the surrounding region or a projection having a height of 10 nm or more from the surrounding region is detected as the defect point. Good. By doing in this way, the defect group which has the above-mentioned specific regularity can be detected more appropriately.

  In the step of confirming the total length, when it is confirmed that the total length exceeds the threshold, a step of polishing the main surface may be further included. Moreover, when the process of grind | polishing a main surface is implemented, the process of detecting a defect point and the process of confirming total length may be implemented again. By doing in this way, a silicon carbide substrate with fewer linear defects can be prepared.

  The threshold value may be a value obtained by subtracting the sum of the longitudinal lengths of linear defects existing in the main surface from the diameter of the circumscribed circle of the main surface of the silicon carbide substrate. By setting such a threshold value as a reference value, the surface state of the silicon carbide substrate can be managed more appropriately.

  The circumscribed circle diameter of the main surface may be 150 mm or greater and 200 mm or less. A silicon carbide substrate having such a main surface is suitable for producing a silicon carbide epi-substrate for a semiconductor device.

  In the method for manufacturing the silicon carbide epi substrate, at least one of a step of detecting a defect point by image processing and a step of confirming the total length may be performed. By utilizing image processing, it is possible to more efficiently carry out detection of defects and confirmation of the total length, which is the sum of effective band-like region lengths.

[Details of the embodiment of the present invention]
Next, an embodiment of a method for manufacturing a silicon carbide epi-substrate of the present application 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 description thereof will not be repeated.

[Method for producing silicon carbide epi-substrate]
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a flowchart showing a procedure of a method for manufacturing a silicon carbide epi-substrate. FIG. 2 is a perspective view showing the structure of the silicon carbide substrate. FIG. 3 is a schematic cross-sectional view showing a cross-sectional structure of the silicon carbide substrate. FIG. 4 is a schematic diagram showing a silicon carbide substrate and defect points existing on its main surface. 5 to 10 are schematic diagrams for explaining a method of determining the total length, respectively. FIG. 11 is a schematic diagram showing an effective band-like region. FIG. 12 is a schematic diagram showing an effective band-like region on the main surface of the silicon carbide substrate. FIG. 13 is a schematic cross-sectional view showing a cross-sectional structure of the silicon carbide epi-substrate.

  Referring to FIG. 1, the method for manufacturing a silicon carbide epi substrate according to the present embodiment includes steps S <b> 10 to S <b> 50 and step S <b> 60 as necessary. Details of each step will be described below.

[Board preparation process]
Referring to FIGS. 1 to 3, first, silicon carbide substrate 10 made of silicon carbide and having main surface 10A is prepared (step S10). Silicon carbide substrate 10 is obtained by slicing a single crystal of silicon carbide to a desired thickness and planarizing main surface 10A thereof. The flattening process of the main surface 10A is performed by polishing the main surface 10A, such as MP (Mechanical Polishing) or CMP (Chemical Mechanical Polishing). Thereafter, silicon carbide substrate 10 according to the present embodiment is obtained by cleaning planarized main surface 10A. Silicon carbide substrate 10 obtained in the present embodiment has a shape in which a circumscribed circle of main surface 10A has a diameter of 150 mm or greater and 200 mm or less.

[Defect point detection process]
Next, a defect point existing on the main surface 10A is detected (step S20). The defect detection can be suitably performed by, for example, a wafer defect inspection apparatus that detects defects using an optical system. As an example of a wafer defect inspection apparatus, as a defect inspection apparatus including a confocal differential interference microscope, a WASAVI series “SICA 6X” manufactured by Lasertec Corporation may be used.

  The defect point detected in the present embodiment is, for example, a point-like defect having a recess having a depth of 10 nm or more from the surrounding region or a protrusion having a height of 10 nm or more from the surrounding region. In the present embodiment, among the dot-like defects, the defect group included in the range of 10 μm in diameter is detected as a single defect point.

Referring to FIG. 4, it is assumed that, for example, defect point P ₁ to defect point P ₄ , defect point Q _1, and defect point Q ₂ exist on main surface 10A of silicon carbide substrate 10. In step S20, these defect points are detected. At this time, it is preferable to detect all defect points present on the main surface 10A. Illustration of other defect points on main surface 10A of silicon carbide substrate 10 detected in step S20 is omitted.

[Total length confirmation process]
Next, the total length which is the sum total in the main surface 10A of the length of the line segment corresponding to the defect point group arranged in a straight line among the defect points is confirmed (step S30). FIG. 4 shows a defect point group including defect points P ₁ to P ₄ arranged in a straight line. In this embodiment, the length of the line corresponding to the defective point group arranged in a straight line (i.e., between the defect points P ₃ ~ defect point P _z in FIG. 10, a first defect point P ₁ second The case where the length in the direction connecting the _two defect points P2) is determined will be described as an example.

  The total length may be confirmed by image processing using image processing software, or may be confirmed by acquiring a photograph of the main surface 10A in the wafer defect inspection apparatus and performing image processing on the photograph. Good. It is also possible to obtain a photograph of the main surface 10A and visually confirm the total length.

In the present embodiment, specifically, the total length is confirmed by the following procedure. Referring to FIG. 5, first, among the detected defect point in step S20, the defect point P ₁ of the arbitrary first, second defect point distance from the first defect point of 10μm or more 600μm or less to extract and P _2. Next, a straight belt-like region 20 having a width W of 20 μm is set so as to include the first defect point P ₁ and the second defect point P ₂ . The straight belt-like region 20 is a region sandwiched between the boundary line 21 and the boundary line 22.

Next, referring to FIG. 6 to FIG. 11, the effective belt-like region 50 is extracted from the straight belt-like region 20. The effective band region 50 is on the second defect point P ₂ side as viewed from the first defect point P _{1 in} the direction connecting the first defect point P ₁ and the second defect point P ₂ of the straight band region 20. towards (side indicated by the direction of arrow D ₂ in FIG. 6) opposite to the second defect point when viewed from and the first defect point P ₁ (the side indicated by the direction of arrow D ₁ in FIG. 6) In other words, it is a straight belt-like portion formed by sequentially extending to the other defect points on condition that another defect point exists within a distance range of 10 μm or more and 600 μm or less.

A method for extracting the effective band-like region 50 will be specifically described with reference to FIGS. Referring to FIG 6, first, a within the linear band-like region 20, the first defect point P ₁ from seeing arrow D ₁ direction, the distance from the first defect point P ₁ is less 600μm or 10μm It is confirmed whether or not there is another defect point within the range 30. As shown in FIG. 6, the second defect point P < _b > ₂ exists within the range 30. Therefore, as shown in FIG. 7, the effective belt-like region 50 is extended to the _second defect point P _{2 in} the direction of the arrow D ₁ . On the other hand, referring to FIG. 6, defect point Q ₁ existing outside straight belt-like region 20 does not satisfy the above condition, and is excluded from the object for forming effective belt-like region 50.

The A within the linear band-like region 20, the arrow D ₂ when viewed from the first defect point P ₁ the orientation of the (first opposite side of the second defect point P ₂ as viewed from the defect point P _1), It is confirmed whether or not there is another defect point in the range 32 where the distance from the _first defect point P1 is 10 μm or more and 600 μm or less. As shown in FIG. 6, the third defect point P ₃ exists in the range 32. Therefore, the effective band-like region 50 as shown in FIG. 7 is extended to third defect point P ₃ in the direction of arrow D _2.

With reference to FIGS. 8 to 10, the same processing is repeated until there is no other defect point that satisfies the above conditions. Referring to FIG. 8, one end portion (second defect point P _{2) of} effective band region 50 in straight band region 20 and in the direction of arrow D ₁ as viewed from _first defect point P _1. distance from the end) containing the within the range 34 600 .mu.m or 10 [mu] m, the fourth defect point _{P 4} exists. Therefore, the effective belt-like region 50 is extended to the _fourth defect point P ₄ on the arrow D ₁ side.

On the other hand, referring to FIG. 8, a within the linear band-like region 20, the orientation arrow D ₂ when viewed from the first defect point P _1, the other end of the effective belt region 50 (third defect other defects point does not exist in the distance 10μm or 600μm within the range 36 from the end portion) including point P _3. There is within the linear band-like region 20 but a defect point Q ₂ to which are outside the scope 36 is excluded from for forming the effective band-like region 50 for the above condition is not met.

Here, the upper limit of the distance range is 600 μm because the defect points existing at the position where the shortest distance from the end of the effective band region 50 exceeds 600 μm are the other defect point groups included in the effective band region 50. This is because the relationship is low, and it is considered that the risk of forming a linear defect in the epilayer in relation to other defect point groups included in the effective band-like region 50 is relatively low. Specifically, a defect point group including defect points P ₁ , P ₂ , P ₃ , and P ₄ can cause a linear defect in the epi layer, but the linear defect has a distance from the defect point P _3. possibility of reaching the position on the epitaxial layer corresponding to the defective point Q ₂ to which more than 600μm is because it is considered to be relatively low. On the other hand, the lower limit is set to 10 μm because a plurality of defect points whose distances are within 10 μm are sufficient to confirm the total length even if they are handled as a single defect point.

Thus, the third more effective band-like region 50 in the direction of arrow D ₂ than the defect point P ₃ is not extended. At this point, as shown in FIG. 9, the effective band-like region 50 is extended to third defect point P ₃ and the fourth defect point P _4.

Referring to FIG. 10, successively extending the effective band-like region 50 in the direction of arrow D ₁ in the range of the linear band-like region 20 in the above same conditions. Finally, a defect point within a distance range of 10 μm or more and 600 μm or less from the defect point P _{Z-1 in} the direction of arrow D ₁ , and a distance range of 10 μm or more and 600 μm or less from the defect point in the direction of arrow D ₁ The effective belt-like region 50 is extended to the defect point P _z in which no other defect point exists in 38. In this way, an effective band-like region 50 as shown in FIG. 11 is extracted. Z is an integer of 5 or more.

The effective belt-like region 50 in the present embodiment is a straight belt-like portion, and five or more defect points exist in the portion. Further, the length L _{1 in the} direction connecting the first defect point P ₁ and the second defect point P _{2 of the} effective belt-like region 50 is 1 mm or more. If the number of defect points included in the straight strip portion is 4 or less, the effective strip region 50 is not handled in the present embodiment. Similarly, if the length L1 is less than ₁ mm, the effective band-like region 50 is not handled.

In determining the effective band-like region 50, the lower limit value of the number of defect points included in the effective band-like region 50 is not necessarily 5 and can be set as appropriate, for example, 3 or 10. Further, the lower limit value of the length L _{1 in} the direction connecting the first defect point P ₁ and the second defect point P _{2 of the} effective band-shaped region 50 is not necessarily 1 mm, for example 0.5 mm or 1 .5 mm can also be used.

Next, referring to FIG. 12, the same operation is performed on the entire main surface 10A to extract the effective band-like regions 50, 52, and 54 on the main surface 10A. At this time, extraction is performed so that the defect points already used for determining other effective band-like regions do not overlap. Lengths L ₁ , L ₂ , L ₃ ,... In the direction connecting the first defect point P ₁ and the second defect point P _{2 of} the effective strip regions 50, 52, 54 extracted as described above. • Check the total length (L ₁ + L ₂ + L ₃ +...) That is the sum of

[Comparison of total length and threshold]
Next, the total length (L ₁ + L ₂ + L ₃ +...) Confirmed in step S30 is compared with a predetermined threshold value to check whether the total length is equal to or less than the threshold value (step S40). The predetermined threshold value can be a value obtained by subtracting the sum of the longitudinal lengths of linear defects (scratches) present on the main surface 10A from the diameter based on the diameter of the circumscribed circle of the main surface 10A, for example. . In other words, the direction connecting the longitudinal length of the linear defects existing on the main surface 10A (scratching), the effective band-like region 50, 52, 54, the first defect point _{P 1} and the second defect point _{P 2} It is confirmed that the sum of the total lengths (L ₁ + L ₂ + L ₃ +...) Is equal to or smaller than the diameter of the circumscribed circle of the main surface 10A. By setting such a threshold value, the surface state of the main surface 10A can be appropriately managed, and the incidence rate of linear defects on the epilayer surface can be reduced.

[Epitaxial layer formation process]
Finally, in step S40, when it is confirmed that the total length on main surface 10A of silicon carbide substrate 10 is equal to or smaller than a predetermined threshold value (in the case of YES in step S40), an epitaxial layer (on the main surface 10A) An epi layer is formed (step S50).

  Referring to FIGS. 1, 2 and 12, in step S50, after the main surface 10A of silicon carbide substrate 10 is subjected to thermal cleaning, hydrogen etching, etc. to ensure the cleanliness of main surface 10A, A semiconductor layer made of silicon carbide is formed on main surface 10A by epitaxial growth. Specifically, buffer layer 60 made of silicon carbide having n-type conductivity is formed by epitaxial growth on main surface 10A of silicon carbide substrate 10 having n-type conductivity. Further, drift layer 70 made of silicon carbide having n-type conductivity is formed on main surface 60A of buffer layer 60. The buffer layer 60 and the drift layer 70 are sequentially formed by performing vapor phase epitaxial growth using, for example, a source gas containing an n-type impurity. Thus, silicon carbide epi-substrate 100 having epitaxial layers (buffer layer 60 and drift layer 70) formed on main surface 10A is manufactured.

[Polishing process]
The effective band-like region which is confirmed in step S40, if the first defect point P ₁ and the second sum direction length connecting the defect point P ₂ is confirmed to exceed a predetermined threshold value (in step S40 In the case of NO), a step of polishing the main surface 10A (step S60) may be performed. The main surface 10A can be polished by the above-described polishing methods such as MP and CMP.

  Moreover, when the process of grind | polishing 10 A of main surfaces is implemented, the process (step S20) which detects a defect point, and the process (step S30) which confirms total length may be implemented again. The step of confirming the total length (step S30) is performed again, and when it is confirmed that the total length is equal to or less than a predetermined threshold, an epitaxial layer (buffer layer 60 and drift layer 70) is formed on main surface 10A. Thus, silicon carbide epi substrate 100 is manufactured (step S50).

  The above is the description of the present embodiment. In the above embodiment, only the detection of the defect point has been described, but other scratches and defects such as a scratch may be detected at the same time.

The effective band-like region is confirmed in step S30 50, 52, 54, of ..., the first defect point _{P 1} and the second sum direction length connecting the defect point _{P 2} is a predetermined threshold value When it is confirmed that it exceeds (NO in step S40), instead of performing the polishing step (step S60), such silicon carbide substrate 10 may be discarded as a defective product.

  In the above-described embodiment, the predetermined threshold value is calculated based on the diameter of the circumscribed circle of the main surface 10A, and the sum of the longitudinal lengths of linear defects (scratches) existing on the main surface 10A is calculated from the diameter. Although the subtracted value is used, the threshold can be set as appropriate. For example, the threshold value can be set to a smaller value, or conversely, the threshold value can be set to a larger value according to the strictness of management of the defect point group to be detected in the main surface 10A.

  Thus, according to the manufacturing method of the said silicon carbide epi substrate, the silicon carbide epi substrate by which generation | occurrence | production of the linear defect in the epi layer surface was suppressed can be provided.

  It should be understood that the embodiments disclosed herein are illustrative in all respects and are not restrictive in any aspect. The scope of the present invention is defined by the terms of the claims, rather than the meaning described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The method for manufacturing a silicon carbide epi-substrate of the present application can be applied particularly advantageously in a technical field where it is required to manufacture a silicon carbide epi-substrate in which the occurrence of linear defects on the epi layer surface is suppressed.

DESCRIPTION OF SYMBOLS 10 Silicon carbide substrate 10A Main surface 20 Straight strip region 21 Boundary line 22 Boundary line 30 Range 32 Range 34 Range 36 Range 38 Range 50 Effective strip region 52 Effective strip region 54 Effective strip region 60 Buffer layer 60A Main surface 70 Drift layer 100 Carbonization Silicon epi substrate

Claims (10)

A step of preparing a silicon carbide substrate made of silicon carbide and having a main surface;
Detecting a defect point which is a concave portion or a convex portion existing on the main surface;
Of the defect points, the step of confirming the total length that is the sum of the lengths of the line segments corresponding to the defect point group arranged in a straight line in the main surface;
Forming an epitaxial layer on the main surface where the total length is confirmed to be equal to or less than a predetermined threshold value. In the step of checking the total length,
Among the defect points, a straight band region including an arbitrary first defect point and a second defect point having a distance of 10 μm or more and 600 μm or less from the first defect point is set, and the straight band region Among the first defect point side and the first defect point in the direction connecting the first defect point and the second defect point in the straight belt-like region, as viewed from the first defect point. From the viewpoint of the second defect point, the second defect point is formed so as to extend to the other defect point on the condition that another defect point exists within a distance range of 10 μm to 600 μm. The effective strip region is extracted as a length of the line segment in the direction connecting the first defect point and the second defect point of the effective strip region,
As the total length, the effective band area is extracted in the entire main surface so that the defect points used for determining the effective band area do not overlap, and the line segment corresponding to the extracted effective band area is extracted. The method for manufacturing a silicon carbide epi-substrate according to claim 1, wherein a total sum of the lengths is calculated.   3. The method for manufacturing a silicon carbide epi substrate according to claim 2, wherein a width of the linear strip region set in the step of checking the total length is 20 μm.   4. The method of manufacturing a silicon carbide epi substrate according to claim 2, wherein in the step of confirming the total length, the effective band-like region is set so as to include five or more defect points. 5.   5. The silicon carbide epi-substrate according to claim 1, wherein in the step of checking the total length, a total length of the line segments having a length of 1 mm or more is set as the total length. Production method.   The step of detecting the defect point, wherein the defect point is a defect point that is a recess having a depth of 10 nm or more from a surrounding region or a projection having a height of 10 nm or more from the surrounding region. The method for manufacturing a silicon carbide epi-substrate according to any one of claims 1 to 5. In the step of confirming the total length, if it is confirmed that the total length exceeds the threshold, the method further includes a step of polishing the main surface,
The silicon carbide according to any one of claims 1 to 6, wherein when the step of polishing the main surface is performed, the step of detecting the defect point and the step of confirming the total length are performed again. Epi substrate manufacturing method.   8. The value according to claim 1, wherein the threshold value is a value obtained by subtracting a sum total of longitudinal lengths of linear defects existing in the main surface from a diameter of a circumscribed circle of the main surface. Of manufacturing a silicon carbide epi-substrate.   The method for manufacturing a silicon carbide epi-substrate according to any one of claims 1 to 8, wherein a diameter of a circumscribed circle of the main surface is not less than 150 mm and not more than 200 mm.   The method for manufacturing a silicon carbide epi substrate according to any one of claims 1 to 9, wherein at least one of a step of detecting the defect point by image processing and a step of confirming the total length is performed.

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