JP2021020853A - Silicon carbide epitaxial substrate and method of manufacturing silicon carbide semiconductor device - Google Patents

Abstract

To provide a silicon carbide epitaxial substrate manufactured by a manufacturing process allowing for improvement of in-plane uniformity of thickness of a layer even in epitaxial growth of silicon carbide by a gas-foil system.SOLUTION: A silicon carbide epitaxial substrate 100 has a silicon carbide single crystal substrate 10 and a silicon carbide layer 20. The silicon carbide layer includes a second principal plane 30 on the opposite side from a plane in contact with the silicon carbide single crystal substrate. The second principal plane has an outer circumferential region 32 which is within 5 mm from an outer edge 31, and a center region 33. The silicon carbide layer has a center surface layer 25. The center surface layer has a carrier concentration average value of 1×1014 cm-3 to 5×1016 cm-3. Circumferential uniformity in carrier concentration is 2% or less and in-plane uniformity in carrier concentration is 10% or less. An average value in thickness of a portion 27 of the silicon carbide layer sandwiched between the center region and the silicon carbide single crystal substrate is 5 μm or larger. Circumferential uniformity in thickness is 1% or less and in-plane uniformity in thickness is 4% or less.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a method for manufacturing a silicon carbide epitaxial substrate and a silicon carbide semiconductor device.

Japanese Unexamined Patent Publication No. 2014-170891 (Patent Document 1) discloses a method of forming a silicon carbide layer on a silicon carbide single crystal substrate by epitaxial growth.

Japanese Unexamined Patent Publication No. 2014-170891

The silicon carbide epitaxial substrate according to the present disclosure includes a silicon carbide single crystal substrate and a silicon carbide layer. The silicon carbide single crystal substrate includes a first main surface. The silicon carbide layer is on the first main surface. The silicon carbide layer includes a second main surface opposite to the surface in contact with the silicon carbide single crystal substrate. The maximum diameter of the second main surface is 100 mm or more. The second main surface has an outer peripheral region within 5 mm from the outer edge of the second main surface and a central region surrounded by the outer peripheral region. The silicon carbide layer has a central surface layer including a central region. The average value of the carrier concentration in the central surface layer is 1 × 10 ¹⁴ cm ^-3 or more and 5 × 10 ¹⁶ cm ^-3 or less. The circumferential uniformity of the carrier concentration is 2% or less, and the in-plane uniformity of the carrier concentration is 10% or less. The average thickness of the portion of the silicon carbide layer sandwiched between the central region and the silicon carbide single crystal substrate is 5 μm or more. The circumferential uniformity of the thickness is 1% or less, and the in-plane uniformity of the thickness is 4% or less. The circumferential uniformity of the carrier concentration is the ratio of the absolute value of the difference between the maximum value and the minimum value of the carrier concentration of the central surface layer in the circumferential direction to the average value of the carrier concentration of the central surface layer in the circumferential direction. In-plane uniformity of carrier concentration is the ratio of the absolute value of the difference between the maximum and minimum values of the carrier concentration of the central surface layer in the entire central region to the average value of the carrier concentration of the central surface layer in the entire central region. .. The circumferential uniformity of the thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the portion in the circumferential direction to the average value of the thickness of the portion in the circumferential direction. The in-plane uniformity of thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the portion in the entire central region to the average value of the thickness of the portion in the entire central region.

It is a plane schematic diagram which shows the structure of the silicon carbide epitaxial substrate which concerns on this embodiment. It is sectional drawing which shows the structure of the silicon carbide epitaxial substrate which concerns on this embodiment. It is a plane schematic diagram which shows the measurement position of a carrier concentration. It is a figure which shows the method of determining the carrier concentration by the CV method. It is a partial cross-sectional schematic diagram which shows the structure of the susceptor plate of the manufacturing apparatus of the silicon carbide epitaxial substrate which concerns on this embodiment. It is a functional block diagram which shows the structure of the manufacturing apparatus of the silicon carbide epitaxial substrate which concerns on this embodiment. It is a top view which shows the structure of the gas ejection hole of the manufacturing apparatus of the silicon carbide epitaxial substrate which concerns on this embodiment. It is a figure which shows the relationship between the rotation speed of a susceptor plate and time. It is a flowchart which shows the outline of the manufacturing method of the silicon carbide semiconductor device which concerns on this embodiment. It is sectional drawing which shows the 1st step of the manufacturing method of the silicon carbide semiconductor device which concerns on this embodiment. It is sectional drawing which shows the 2nd step of the manufacturing method of the silicon carbide semiconductor device which concerns on this embodiment. It is sectional drawing which shows the 3rd process of the manufacturing method of the silicon carbide semiconductor device which concerns on this embodiment.

[Explanation of Embodiments of the present disclosure]
First, an embodiment of the present disclosure will be described. In the following description, the same or corresponding elements are designated by the same reference numerals, and the same description is not repeated for them. In the crystallographic description of the present specification, the individual orientation is indicated by [], the aggregation orientation is indicated by <>, the individual plane is indicated by (), and the aggregation plane is indicated by {}. Negative crystallographic exponents are usually expressed by adding a "-" (bar) above the number, but here the number is preceded by a negative sign for crystallography. Represent the above negative index.

(1) The silicon carbide epitaxial substrate 100 according to the present disclosure includes a silicon carbide single crystal substrate 10 and a silicon carbide layer 20. The silicon carbide single crystal substrate 10 includes a first main surface 11. The silicon carbide layer 20 is on the first main surface 11. The silicon carbide layer 20 includes a second main surface 30 on the side opposite to the surface 14 in contact with the silicon carbide single crystal substrate 10. The maximum diameter 111 of the second main surface 30 is 100 mm or more. The second main surface 30 has an outer peripheral region 32 within 5 mm from the outer edge 31 of the second main surface 30 and a central region 33 surrounded by the outer peripheral region 32. The silicon carbide layer 20 has a central surface layer 25 including a central region 33. The average value of the carrier concentration in the central surface layer 25 is 1 × 10 ¹⁴ cm ^-3 or more and 5 × 10 ¹⁶ cm ^-3 or less. The circumferential uniformity of the carrier concentration is 2% or less, and the in-plane uniformity of the carrier concentration is 10% or less. The average value of the thickness of the silicon carbide layer portion 27 sandwiched between the central region 33 and the silicon carbide single crystal substrate 10 is 5 μm or more. The circumferential uniformity of the thickness is 1% or less, and the in-plane uniformity of the thickness is 4% or less. The circumferential uniformity of the carrier concentration is the ratio of the absolute value of the difference between the maximum value and the minimum value of the carrier concentration of the central surface layer 25 in the circumferential direction to the average value of the carrier concentration of the central surface layer 25 in the circumferential direction. .. The in-plane uniformity of the carrier concentration is the ratio of the absolute value of the difference between the maximum value and the minimum value of the carrier concentration of the central surface layer 25 in the entire central region to the average value of the carrier concentration of the central surface layer 25 in the entire central region. Is. The circumferential uniformity of the thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the portion 27 in the circumferential direction to the average value of the thickness of the portion 27 in the circumferential direction. The in-plane uniformity of the thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the portion 27 in the entire central region to the average value of the thickness of the portion 27 in the entire central region.

When the silicon carbide layer is formed by epitaxial growth, the silicon carbide layer is formed on the silicon carbide single crystal substrate while rotating the silicon carbide single crystal substrate. The silicon carbide layer is formed at a high temperature of, for example, about 1600 ° C. Therefore, it is not possible to adopt a mechanism for mechanically rotating the silicon carbide single crystal substrate 10 using a metal such as stainless steel. Therefore, in the epitaxial growth of the silicon carbide layer, a gas foil method is adopted in which the susceptor plate is rotated while the susceptor plate holding the silicon carbide single crystal substrate is floated by using a gas such as hydrogen. ..

However, in the case of the gas foil method, deposits such as silicon carbide may adhere to the vicinity of the gas ejection hole for ejecting gas to the susceptor plate, for example. As a result, the direction and speed of gas flow change, so the rotation speed of the susceptor plate changes. If the shape of the susceptor plate is distorted, the rotation speed will not be stable. Further, as time passes, the silicon carbide layer is deposited on the silicon carbide single crystal substrate and the susceptor plate, and the total weight changes, so that the rotation speed may change. For the above reasons, it is considered that the rotation speed is not stable in the case of the gas foil method. It is presumed that this is the cause of the large variation in the thickness of the silicon carbide layer and the carrier concentration in the silicon carbide layer in the circumferential direction of the silicon carbide single crystal substrate.

Therefore, the inventors have found that the fluctuation of the rotation speed can be suppressed by monitoring the rotation speed of the silicon carbide single crystal substrate and feedback-controlling the flow rate of the gas based on the rotation speed. As a result, the uniformity of the carrier concentration in the silicon carbide layer and the uniformity of the thickness of the silicon carbide layer can be improved in the circumferential direction of the silicon carbide single crystal substrate. As a result, the in-plane uniformity of the carrier concentration in the silicon carbide layer and the in-plane uniformity of the thickness of the silicon carbide layer can be improved.

(2) The maximum diameter of the silicon carbide epitaxial substrate 100 according to (1) above may be 150 mm or more.

(3) In the silicon carbide epitaxial substrate 100 according to (1) or (2) above, the average value of the carrier concentration may be 1 × 10 ¹⁵ cm ^-3 or more and 1 × 10 ¹⁶ cm ^-3 or less.

(4) In the silicon carbide epitaxial substrate 100 according to any one of (1) to (3) above, the circumferential uniformity of the carrier concentration may be 1% or less.

(5) In the silicon carbide epitaxial substrate 100 according to any one of (1) to (4) above, the in-plane uniformity of the carrier concentration may be 5% or less.

(6) The method for manufacturing a silicon carbide semiconductor device according to the present disclosure includes the following steps. The silicon carbide epitaxial substrate 100 according to any one of (1) to (5) above is prepared. The silicon carbide epitaxial substrate 100 is processed.

[Details of Embodiments of the present disclosure]
Hereinafter, one embodiment of the present disclosure (hereinafter, also referred to as “the present embodiment”) will be described. However, this embodiment is not limited to these.

(Silicon Carbide epitaxial substrate)
As shown in FIGS. 1 and 2, the silicon carbide epitaxial substrate 100 according to the present embodiment has a silicon carbide single crystal substrate 10 and a silicon carbide layer 20. The silicon carbide single crystal substrate 10 includes a first main surface 11 and a third main surface 13 opposite to the first main surface 11. The silicon carbide layer 20 includes a fourth main surface 14 in contact with the silicon carbide single crystal substrate 10 and a second main surface 30 on the opposite side of the fourth main surface 14. As shown in FIG. 1, the silicon carbide epitaxial substrate 100 may have a first flat 5 extending in the first direction 101. The silicon carbide epitaxial substrate 100 may have a second flat (not shown) extending in the second direction 102. The first direction 101 is, for example, the <11-20> direction. The second direction 102 is, for example, the <1-100> direction.

The silicon carbide single crystal substrate 10 (hereinafter, may be abbreviated as “single crystal substrate”) is composed of a silicon carbide single crystal. The polytype of the silicon carbide single crystal is, for example, 4H-SiC. 4H-SiC is superior to other polytypes in electron mobility, dielectric breakdown electric field strength, and the like. The silicon carbide single crystal substrate 10 contains n-type impurities such as nitrogen. The conductive type of the silicon carbide single crystal substrate 10 is, for example, n type. The first main surface 11 is, for example, a {0001} surface or a surface inclined by 8 ° or less from the {0001} surface. When the first main surface 11 is inclined from the {0001} surface, the inclination direction of the normal of the first main surface 11 is, for example, the <11-20> direction.

The silicon carbide layer 20 is an epitaxial layer formed on the silicon carbide single crystal substrate 10. The silicon carbide layer 20 is on the first main surface 11. The silicon carbide layer 20 is in contact with the first main surface 11. The silicon carbide layer 20 contains n-type impurities such as nitrogen (N). The conductive type of the silicon carbide layer 20 is, for example, n type. The concentration of n-type impurities contained in the silicon carbide layer 20 may be lower than the concentration of n-type impurities contained in the silicon carbide single crystal substrate 10. As shown in FIG. 1, the maximum diameter 111 (diameter) of the second main surface 30 is 100 mm or more. The diameter of the maximum diameter 111 may be 150 mm or more, 200 mm or more, or 250 mm or more. The upper limit of the maximum diameter 111 is not particularly limited. The upper limit of the maximum diameter 111 may be, for example, 300 mm.

The second main surface 30 may be, for example, a {0001} surface or a surface inclined by 8 ° or less from the {0001} surface. Specifically, the second main surface 30 may be a (0001) plane or a plane inclined by 8 ° or less from the (0001) plane. The inclination direction (off direction) of the normal of the second main surface 30 may be, for example, the <11-20> direction. The inclination angle (off angle) from the {0001} plane may be 1 ° or more, or 2 ° or more. The off angle may be 7 ° or less, or 6 ° or less.

As shown in FIG. 1, the second main surface 30 has an outer peripheral region 32 and a central region 33 surrounded by the outer peripheral region 32. The outer peripheral region 32 is an region within 5 mm from the outer edge 31 of the second main surface 30. In other words, the distance 112 between the outer edge 31 and the boundary between the outer peripheral region 32 and the central region 33 in the radial direction of the second main surface 30 is 5 mm.

As shown in FIG. 2, the silicon carbide layer 20 has a buffer layer 21 and a drift layer 24. The concentration of n-type impurities contained in the drift layer 24 may be lower than the concentration of n-type impurities contained in the buffer layer 21. The drift layer 24 includes a surface layer region 23 and a deep layer region 22. The surface layer region 23 constitutes the second main surface 30. The surface layer region 23 has a central surface layer 25 and an outer peripheral surface layer region 19. The central surface layer 25 constitutes the central region 33. The outer peripheral surface layer region 19 constitutes the outer peripheral region 32. The central surface layer 25 is surrounded by the outer peripheral surface layer region 19 when viewed from a direction perpendicular to the second main surface 30. The central surface layer 25 is a region within about 5 μm from the central region 33 toward the first main surface.

The deep region 22 has a central deep region 18 and an outer peripheral deep region 17. The central deep layer region 18 is surrounded by the outer peripheral deep layer region 17 when viewed from a direction perpendicular to the second main surface 30. Similarly, the buffer layer 21 has a central buffer area 16 and an outer buffer area 15. The central buffer area 16 is surrounded by the outer peripheral buffer area 15 when viewed from a direction perpendicular to the second main surface 30. The central deep layer region 18 is sandwiched between the central buffer region 16 and the central surface layer 25. Similarly, the outer peripheral deep layer region 17 is sandwiched between the outer peripheral buffer region 15 and the outer peripheral surface layer region 19.

The silicon carbide layer 20 is composed of a central silicon carbide region 27 and an outer silicon carbide region 26. The central silicon carbide region 27 is composed of a central surface layer 25, a central deep layer region 18, and a central buffer region 16. Similarly, the outer peripheral silicon carbide region 26 is composed of an outer peripheral surface layer region 19, an outer peripheral deep layer region 17, and an outer peripheral buffer region 15.

(Circular uniformity and in-plane uniformity of carrier concentration)
The silicon carbide layer 20 contains, for example, nitrogen as a dopant. According to the silicon carbide epitaxial substrate 100 according to the present disclosure, the average value of the carrier concentration in the central surface layer 25 is 1 × 10 ¹⁴ cm ^-3 or more and 5 × 10 ¹⁶ cm ^-3 or less. In the central surface layer 25, the circumferential uniformity of the carrier concentration is 2% or less, and the in-plane uniformity of the carrier concentration is 10% or less. Circumferential uniformity and in-plane uniformity indicate that the smaller the value, the more uniformly the carrier concentration is distributed. The carrier concentration in the present application means an effective carrier concentration. For example, when the silicon carbide layer contains a donor and an acceptor, the effective carrier concentration is calculated as the absolute value (| N _{d −} N _a |) of the difference between the donor concentration (N _d ) and the acceptor concentration (N _a ). Will be done. The method for measuring the carrier concentration will be described later.

In the central surface layer 25, the average value of the carrier concentration may be 2 × 10 ¹⁶ cm ^-3 or less, or 9 × 10 ¹⁵ cm ^-3 or less. The average value of the carrier concentration may be, for example, 1 × 10 ¹⁵ cm ^-3 or more, or 5 × 10 ¹⁵ cm ^-3 or more.

In the central surface layer 25, the circumferential uniformity of the carrier concentration may be 1.5% or less, 1% or less, or 0.5% or less. In the central surface layer 25, the in-plane uniformity of the carrier concentration may be 8% or less, 5% or less, or 3% or less.

Next, a method for measuring the carrier concentration will be described. The carrier concentration is measured by, for example, a mercury probe type CV measuring device. Specifically, one probe is arranged at the measurement position of the central region 33, which will be described later, and the other probe is arranged on the third main surface 13. The area of one probe is, for example, 0.01 cm ² . A voltage is applied between one probe and the other probe, and the capacitance between one probe and the other probe is measured.

As shown in FIG. 3, a plurality of concentric circles 34 centered on the center 35 of the second main surface 30 are assumed. Each of the plurality of concentric circles 34 has a common center 35. As shown in FIG. 3, the measurement position of the carrier concentration can be the position indicated by hatching. Specifically, the measurement positions of the carrier concentration pass through the center 35 and on the straight line 4 parallel to the first direction 101, on the straight line 3 passing through the center 35 and parallel to the second direction 102, and passing through the center 35. It is on a straight line 6 that divides the angle formed by the straight line 4 and the straight line 3 into two equal parts. The intersection of the boundary line between the outer peripheral region 32 and the central region 33 and the straight line 3 and the line segment connecting the central 35 are substantially divided into five equal parts. The measurement position may be the position of the intersection of the five concentric circles 34 centered on the center 35 and the straight line 3, the straight line 4, and the straight line 6 through the respective positions where the line segment is divided into five equal parts. As shown in FIG. 3, the carrier concentration is measured at a total of 31 measurement positions in the central region.

As shown in FIG. 3, the outer edge 31 includes an arc portion 7 and a linear first flat 5. The center of the circumscribed circle of the triangle formed by any three points on the arc portion 7 may be the center 35 of the second main surface 30.

The circumferential uniformity of the carrier concentration is the ratio of the absolute value of the difference between the maximum value and the minimum value of the carrier concentration of the central surface layer 25 in the circumferential direction to the average value of the carrier concentration of the central surface layer 25 in the circumferential direction. .. Specifically, the average value, the maximum value, and the minimum value of the carrier concentration at eight measurement positions on one concentric circle 34 are obtained, and the circumferential uniformity of the carrier concentration is calculated. According to the silicon carbide epitaxial substrate according to the present disclosure, the circumferential uniformity of the carrier concentration is 2% or less in each of the above five concentric circles 34. For example, the average value of the carrier concentration at the above eight measurement positions is 1.00 × 10 ¹⁶ cm ^-3 , the maximum value is 1.01 × 10 ¹⁶ cm ^-3 , and the minimum value is 0.99 × 10. ^When it is ¹⁶ cm ^-3 , the circumferential uniformity of the carrier concentration is (1.01 × 10 ¹⁶ cm ^-3 −0.99 × 10 ¹⁶ cm ^-3 ) /1.00 × 10 ¹⁶ cm ^-3 = 2. %.

The in-plane uniformity of the carrier concentration is the ratio of the absolute value of the difference between the maximum value and the minimum value of the carrier concentration of the central surface layer 25 in the entire central region to the average value of the carrier concentration of the central surface layer 25 in the entire central region. Is. Specifically, the average value, the maximum value, and the minimum value of the carrier concentration at the above 31 measurement positions are obtained, and the in-plane uniformity of the carrier concentration is calculated. According to the silicon carbide epitaxial substrate according to the present disclosure, the in-plane uniformity of the carrier concentration is 10% or less. For example, the average value of the carrier concentration at the above 31 measurement positions is 1.00 × 10 ¹⁶ cm ^-3 , the maximum value is 1.05 × 10 ¹⁶ cm ^-3 , and the minimum value is 0.95 × 10 ^{When 16} cm ^-3 , the in-plane uniformity of carrier concentration is (1.05 × 10 ¹⁶ cm ^-3 −0.95 × 10 ¹⁶ cm ^-3 ) /1.00 × 10 ¹⁶ cm ^-3 = 10 %.

As shown in FIG. 4, the vertical axis is 1 / C (the reciprocal of the capacitance), the horizontal axis is V (voltage), and the measurement data 41 is plotted. As shown in FIG. 4, as the voltage increases, the reciprocal of the capacitance decreases. The carrier concentration can be obtained from the slope of the straight line of the measurement data 41. The larger the absolute value of the slope of the measurement data 41, the higher the carrier concentration. In FIG. 4, the carrier concentration of the substrate showing the measurement data 41 represented by the straight line is higher than the carrier concentration of the substrate showing the measurement data 42 represented by the broken line. The measurement depth of the carrier concentration depends on the applied voltage. In this embodiment, the voltage is swept from 0V to 5V (voltage V1 in FIG. 4), for example. As a result, the carrier concentration in the central surface layer 25 within about 5 μm from the central region 33 toward the first main surface 11 is measured. When the voltage becomes higher than the voltage V1, the carrier concentration in the region up to the deeper position is measured.

(Circular uniformity and in-plane uniformity of the thickness of the silicon carbide layer)
The average value of the thickness 113 of the portion of the silicon carbide layer (that is, the central silicon carbide region 27) sandwiched between the central region 33 and the silicon carbide single crystal substrate 10 is 5 μm or more. The average value of the thickness 113 may be 10 μm or more, or 15 μm or more. The circumferential uniformity of the thickness is 1% or less, and the in-plane uniformity of the thickness is 4% or less. The circumferential uniformity of the thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the central silicon carbide region 27 in the circumferential direction to the average value of the thickness of the central silicon carbide region 27 in the circumferential direction. The in-plane uniformity of the thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the central silicon carbide region 27 in the entire central region to the average value of the thickness of the central silicon carbide region 27 in the entire central region. is there.

The thickness measurement position may be the same as the carrier concentration measurement position described above. Specifically, as shown in FIG. 3, the average value, the maximum value, and the minimum value of the thickness of the central silicon carbide region 27 at eight measurement positions on one concentric circle 34 are obtained. The circumferential uniformity of the thickness of the central silicon carbide region 27 is calculated. According to the silicon carbide epitaxial substrate according to the present disclosure, the circumferential uniformity of the thickness of each of the above five concentric circles 34 is 1% or less. For example, when the average value of the thickness of the central silicon carbide region 27 at the above eight measurement positions is 10.00 μm, the maximum value is 10.05 μm, and the minimum value is 9.95 μm, the thickness is uniform in the circumferential direction. The sex is (10.05 μm-9.95 μm) / 10 μm = 1%. Similarly, the average value, the maximum value, and the minimum value of the thickness of the central silicon carbide region 27 at the above 31 measurement positions are obtained, and the in-plane uniformity of the thickness of the central silicon carbide region 27 is calculated. .. When the average value of the thickness of the central silicon carbide region 27 at the above 31 measurement positions is 10.0 μm, the maximum value is 10.2 μm, and the minimum value is 9.8 μm, the circumferential uniformity of the thickness is , (10.2 μm-9.8 μm) / 10 μm = 4%.

(Film formation equipment)
Next, the configuration of the manufacturing apparatus 200 used in the manufacturing method of the silicon carbide epitaxial substrate 100 according to the present embodiment will be described.

As shown in FIG. 5, the manufacturing apparatus 200 is, for example, a hot wall type CVD (Chemical Vapor Deposition) apparatus. The manufacturing apparatus 200 mainly includes a heating element 203, a quartz tube 204, a heat insulating material 205, an induction heating coil 206, and a preheating mechanism 211. The cavity surrounded by the heating element 203 is the reaction chamber 201. The reaction chamber 201 is provided with a susceptor plate 210 for holding the silicon carbide single crystal substrate 10. The susceptor plate 210 is rotatable. The silicon carbide single crystal substrate 10 is placed on the susceptor plate 210 with the first main surface 11 facing up.

The heating element 203 is made of graphite, for example. The induction heating coil 206 is wound along the outer circumference of the quartz tube 204. By supplying a predetermined alternating current to the induction heating coil 206, the heating element 203 is induced and heated. This heats the reaction chamber 201.

The manufacturing apparatus 200 further includes a gas inlet 207 and a gas exhaust port 208. The gas exhaust port 208 is connected to an exhaust pump (not shown). Arrows in FIG. 5 indicate gas flow. The carrier gas, raw material gas and doping gas are introduced into the reaction chamber 201 from the gas introduction port 207 and exhausted from the gas exhaust port 208. The pressure in the reaction chamber 201 is adjusted by the balance between the amount of gas supplied and the amount of gas exhausted.

(Feedback control unit)
As shown in FIG. 6, the manufacturing apparatus 200 may further include a rotation speed meter 51, a control unit 52, an MFC (Mass Flow Controller) 53, and a gas supply source 54. The rotation speed meter 51 may be a laser rotation speed meter configured so that the rotation speed of the silicon carbide single crystal substrate 10 (in other words, the rotation speed of the susceptor plate 210) can be monitored by using, for example, laser light. .. The rotation speed meter 51 may monitor the rotation speed of the silicon carbide single crystal substrate 10 with reference to the first flat 5 of the silicon carbide single crystal substrate 10. The rotation speed meter 51 is arranged at a position facing the first main surface 11.

The heating element 203 is provided with a recess 68. The recess 68 is composed of a bottom surface 62 and a side surface 67. A gas ejection hole 63 is provided on the bottom surface 62. The gas ejection hole 63 communicates with the flow path 64 provided in the heating element 203. The gas supply source 54 is configured to be able to supply a gas such as hydrogen to the flow path 64. An MFC 53 is provided between the gas supply source 54 and the flow path 64. The MFC 53 is configured to be able to control the flow rate of the gas supplied from the gas supply source 54 to the flow path 64. The gas supply source is a gas cylinder capable of supplying an inert gas such as hydrogen or argon.

As shown in FIG. 7, a plurality of gas ejection holes 63 are provided on the bottom surface 62. The gas ejection holes 63 may be provided at positions such as 0 °, 90 °, 180 ° and 270 ° when viewed from a direction perpendicular to the bottom surface 62. Each of the plurality of gas ejection holes 63 is configured to be able to eject gas along the circumferential direction of the bottom surface 61 of the susceptor plate 210. When viewed from a direction parallel to the bottom surface 62 (in the field of view of FIG. 6), the direction of the gas ejected from the gas ejection hole 63 may be inclined with respect to the bottom surface 61. In FIGS. 6 and 7, the direction of the arrow indicates the direction of gas flow. When the gas is injected onto the bottom surface 61, the susceptor plate 210 floats and rotates in the circumferential direction 103 of the silicon carbide single crystal substrate 10. The susceptor plate 210 rotates in the circumferential direction 103 with the bottom surface 61 of the susceptor plate 210 separated from the bottom surface 62 of the recess 68 and the side surface 65 of the susceptor plate 210 separated from the side surface 67 of the recess 68.

The control unit 52 is configured to be able to acquire information on the rotation speed of the silicon carbide single crystal substrate 10 measured by the rotation speed meter 51. The control unit 52 is configured to be able to transmit a signal to the MFC 53 based on the information on the rotation speed of the silicon carbide single crystal substrate 10. For example, when the rotation speed of the susceptor plate 210 is lower than the desired rotation speed, the control unit 52 sends a signal to the MFC 53 to increase the flow rate of the gas supplied to the flow path 64. As a result, the flow rate of the gas supplied from the gas supply source 54 to the flow path 64 increases. As a result, the rotation speed of the silicon carbide single crystal substrate 10 increases. On the contrary, when the rotation speed of the susceptor plate 210 is higher than the desired rotation speed, the control unit 52 sends a signal to the MFC 53 to reduce the flow rate of the gas supplied to the flow path 64. As a result, the flow rate of the gas supplied from the gas supply source 54 to the flow path 64 is reduced. As a result, the rotation speed of the silicon carbide single crystal substrate 10 is reduced.

That is, the flow rate of the gas introduced into the flow path 64 is adjusted based on the rotation speed of the silicon carbide single crystal substrate 10 detected by the rotation speed meter 51. In other words, the rotation speed meter 51, the control unit 52, and the MFC 53 form a feedback circuit. As a result, the change in the rotation speed of the silicon carbide single crystal substrate 10 can be suppressed. As a result, the uniformity of the carrier concentration can be improved in the circumferential direction of the second main surface 30.

Normally, the susceptor plate 210 and the single crystal substrate 10 are arranged substantially in the center in the axial direction of the reaction chamber 201. As shown in FIG. 5, in the present disclosure, the susceptor plate 210 and the single crystal substrate 10 may be arranged on the downstream side of the center of the reaction chamber 201, that is, on the gas exhaust port 208 side. This is because the decomposition reaction of the raw material gas is sufficiently advanced by the time the raw material gas reaches the single crystal substrate 10. As a result, it is expected that the distribution of the C / Si ratio will be uniform in the plane of the single crystal substrate 10.

(Preheating mechanism)
Ammonia gas, which is a dopant gas, is preferably sufficiently heated and thermally decomposed in advance before being supplied to the reaction chamber 201. This can be expected to improve the in-plane uniformity of the nitrogen concentration (carrier concentration) in the silicon carbide layer 20. As shown in FIG. 5, a preheating mechanism 211 is provided on the upstream side of the reaction chamber 201. Ammonia gas can be preheated in the preheating mechanism 211. The preheating mechanism 211 includes, for example, a room heated to 1300 ° C. or higher. When the ammonia gas passes through the inside of the preheating mechanism 211, it is sufficiently thermally decomposed and then supplied to the reaction chamber 201. With such a configuration, the ammonia gas can be thermally decomposed without causing a large turbulence in the gas flow.

The temperature of the inner wall surface of the preheating mechanism 211 is more preferably 1350 ° C. or higher. This is to promote the thermal decomposition of ammonia gas. Further, in consideration of thermal efficiency, the temperature of the inner wall surface of the preheating mechanism 211 is preferably 1600 ° C. or lower. The preheating mechanism 211 may be integrated with the reaction chamber 201 or may be a separate body. Further, the gas passing through the inside of the preheating mechanism 211 may be only ammonia gas or may contain other gases. For example, the entire raw material gas may be passed through the inside of the preheating mechanism 211.

(Manufacturing method of silicon carbide epitaxial substrate)
Next, a method for manufacturing the silicon carbide epitaxial substrate according to the present embodiment will be described.

First, for example, a polytype 6H silicon carbide single crystal is produced by a sublimation method. Next, the silicon carbide single crystal substrate 10 is prepared by slicing the silicon carbide single crystal with, for example, a wire saw. The silicon carbide single crystal substrate 10 has a first main surface 11 and a third main surface 13 opposite to the first main surface 11. The first main surface 11 is, for example, a surface inclined by 8 ° or less from the {0001} surface. As shown in FIGS. 5 and 6, the silicon carbide single crystal substrate 10 is arranged in the recess 66 of the susceptor plate 210 so that the first main surface 11 is exposed from the susceptor plate 210. Next, the silicon carbide layer 20 is formed by epitaxial growth on the silicon carbide single crystal substrate 10 by using the manufacturing apparatus 200 described above.

For example, after the pressure in the reaction chamber 201 is reduced from atmospheric pressure to about 1 × 10 ^-6 Pa, the temperature rise of the silicon carbide single crystal substrate 10 is started. During the temperature rise, hydrogen (H ₂ ) gas, which is a carrier gas, is introduced into the reaction chamber 201.

After the temperature in the reaction chamber 201 reaches, for example, about 1600 ° C., the raw material gas and the doping gas are introduced into the reaction chamber 201. The raw material gas includes a Si source gas and a C source gas. As the Si source gas, for example, silane (SiH ₄ ) gas can be used. As the C source gas, for example, propane (C ₃ H ₈ ) gas can be used. The flow rate of silane gas and the flow rate of propane gas are, for example, 46 sccm and 14 sccm. The volume ratio of silane gas to hydrogen is, for example, 0.04%. The C / Si ratio of the raw material gas is, for example, 0.9.

As the doping gas, for example, ammonia (NH ₃ ) gas is used. Ammonia gas is more easily pyrolyzed than nitrogen gas having a triple bond. By using ammonia gas, improvement of in-plane uniformity of carrier concentration can be expected. The concentration of ammonia gas with respect to hydrogen gas is, for example, 1 ppm. It is desirable that the ammonia gas is pyrolyzed in advance by the preheating mechanism 211 before being introduced into the reaction chamber 201. Ammonia gas is heated to, for example, 1300 ° C. or higher by the preheating mechanism 211.

A carrier gas, a raw material gas, and a doping gas are introduced into the reaction chamber 201 while the silicon carbide single crystal substrate 10 is heated to about 1600 ° C., so that the silicon carbide layer 20 is epitaxially grown on the silicon carbide single crystal substrate 10. Is formed by. While the silicon carbide layer 20 is epitaxially grown, the susceptor plate 210 is rotating around a rotation shaft 212 (see FIG. 5). The average rotation speed of the susceptor plate 210 is, for example, 20 rpm.

As shown in FIG. 6, while the silicon carbide layer 20 is formed on the silicon carbide single crystal substrate 10 by epitaxial growth, the rotation speed of the silicon carbide single crystal substrate 10 is monitored by the rotation speed meter 51. The control unit 52 acquires information on the rotation speed of the silicon carbide single crystal substrate 10 measured by the rotation speed meter 51. The control unit 52 transmits a signal to the MFC 53 based on the information on the rotation speed of the silicon carbide single crystal substrate 10. That is, the flow rate of the gas introduced into the flow path 64 is adjusted based on the rotation speed of the silicon carbide single crystal substrate 10 detected by the rotation speed meter 51.

For example, assume that the target rotation speed of the susceptor plate 210 is 20 rpm. For example, when the rotation speed of the susceptor plate 210 is lower than 20 rpm by a predetermined value, the control unit 52 sends a signal to the MFC 53 to increase the flow rate of the gas supplied to the flow path 64. As a result, the flow rate of the gas supplied from the gas supply source 54 to the flow path 64 increases. As a result, the number of revolutions increases and approaches 20 rpm. On the contrary, when the rotation speed becomes higher than 20 rpm by a predetermined value, the control unit 52 sends a signal to the MFC 53 to reduce the flow rate of the gas supplied to the flow path 64. As a result, the flow rate of the gas supplied from the gas supply source 54 to the flow path 64 is reduced. As a result, the number of revolutions decreases and approaches 20 rpm.

As shown in FIG. 8, the rotation speed of the susceptor plate 210 changes slightly from the start of growth to the end of growth of the silicon carbide layer 20. During the step of forming the silicon carbide layer 20, the number of revolutions may be alternately increased and decreased. The amplitude of the number of revolutions may decrease over time. The number of revolutions may converge to a constant value over time. Preferably, the rotation speed of the susceptor plate 210 is controlled to an average rotation speed of ± 10%. For example, when the average rotation speed is 20 rpm, it is desirable that the rotation speed is controlled to 18 rpm or more and 22 rpm or less during the step of forming the silicon carbide layer 20. That is, it is desirable that the maximum rotation speed R2 is 22 rpm or less and the minimum rotation speed R1 is 18 rpm or more. More preferably, the rotation speed of the susceptor plate 210 is controlled to an average rotation speed of ± 8%, and more preferably to an average rotation speed of ± 5%. As described above, the silicon carbide layer 20 is formed on the silicon carbide single crystal substrate 10 by epitaxial growth. This makes it possible to improve the uniformity of the carrier concentration in the silicon carbide layer 20 and the uniformity of the thickness of the silicon carbide layer 20 in the circumferential direction of the silicon carbide single crystal substrate 10. As a result, the in-plane uniformity of the carrier concentration in the silicon carbide layer 20 and the in-plane uniformity of the thickness of the silicon carbide layer 20 can be improved.

(Manufacturing method of silicon carbide semiconductor device)
Next, a method for manufacturing the silicon carbide semiconductor device 300 according to the present embodiment will be described.

The method for manufacturing a silicon carbide semiconductor device according to the present embodiment mainly includes an epitaxial substrate preparation step (S10: FIG. 9) and a substrate processing step (S20: FIG. 9).

First, the epitaxial substrate preparation step (S10: FIG. 9) is carried out. Specifically, the silicon carbide epitaxial substrate 100 is prepared by the method for manufacturing a silicon carbide epitaxial substrate described above (see FIG. 1).

Next, the substrate processing step (S20: FIG. 9) is carried out. Specifically, a silicon carbide semiconductor device is manufactured by processing a silicon carbide epitaxial substrate. “Processing” includes, for example, various processes such as ion implantation, heat treatment, etching, oxide film formation, electrode formation, and dicing. That is, the substrate processing step may include processing at least one of ion implantation, heat treatment, etching, oxide film formation, electrode formation and dicing.

Hereinafter, a method for manufacturing a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) as an example of a silicon carbide semiconductor device will be described. The substrate processing step (S20: FIG. 9) includes an ion implantation step (S21: FIG. 9), an oxide film forming step (S22: FIG. 9), an electrode forming step (S23: FIG. 9), and a dicing step (S24: FIG. 9). including.

First, the ion implantation step (S21: FIG. 9) is carried out. A p-type impurity such as aluminum (Al) is injected into the second main surface 30 on which a mask (not shown) having an opening is formed. As a result, the body region 132 having the p-type conductive type is formed. Next, an n-type impurity such as phosphorus (P) is injected into a predetermined position in the body region 132. As a result, the source region 133 having an n-type conductive type is formed. Next, a p-type impurity such as aluminum is injected into a predetermined position in the source region 133. As a result, a contact region 134 having a p-type conductive type is formed (see FIG. 10).

In the silicon carbide layer 20, the portion other than the body region 132, the source region 133, and the contact region 134 becomes the drift region 131. The source region 133 is separated from the drift region 131 by the body region 132. Ion implantation may be performed by heating the silicon carbide epitaxial substrate 100 to about 300 ° C. or higher and 600 ° C. or lower. After ion implantation, activation annealing is performed on the silicon carbide epitaxial substrate 100. By activation annealing, impurities injected into the silicon carbide layer 20 are activated, and carriers are generated in each region. The atmosphere of activation annealing may be, for example, an argon (Ar) atmosphere. The temperature of activation annealing may be, for example, about 1800 ° C. The activation annealing time may be, for example, about 30 minutes.

Next, an oxide film forming step (S22: FIG. 9) is carried out. For example, when the silicon carbide epitaxial substrate 100 is heated in an atmosphere containing oxygen, an oxide film 136 is formed on the second main surface 30 (see FIG. 11). The oxide film 136 is composed of, for example, silicon dioxide (SiO ₂ ) or the like. The oxide film 136 functions as a gate insulating film. The temperature of the thermal oxidation treatment may be, for example, about 1300 ° C. The time of the thermal oxidation treatment may be, for example, about 30 minutes.

After the oxide film 136 is formed, heat treatment may be further performed in a nitrogen atmosphere. For example, nitric oxide (NO), in an atmosphere of nitrous oxide (N ₂ O) or the like, for about 1 hour at about 1100 ° C., the heat treatment may be performed. After that, the heat treatment may be performed in an argon atmosphere. For example, the heat treatment may be performed in an argon atmosphere at about 1100 to 1500 ° C. for about 1 hour.

Next, the electrode forming step (S23: FIG. 9) is carried out. The first electrode 141 is formed on the oxide film 136. The first electrode 141 functions as a gate electrode. The first electrode 141 is formed by, for example, a CVD method. The first electrode 141 is made of, for example, polysilicon containing impurities and having conductivity. The first electrode 141 is formed at a position facing the source region 133 and the body region 132.

Next, an interlayer insulating film 137 covering the first electrode 141 is formed. The interlayer insulating film 137 is formed by, for example, a CVD method. The interlayer insulating film 137 is made of, for example, silicon dioxide or the like. The interlayer insulating film 137 is formed so as to be in contact with the first electrode 141 and the oxide film 136. Next, the oxide film 136 and the interlayer insulating film 137 at predetermined positions are removed by etching. As a result, the source region 133 and the contact region 134 are exposed from the oxide film 136.

For example, a second electrode 142 is formed on the exposed portion by a sputtering method. The second electrode 142 functions as a source electrode. The second electrode 142 is made of, for example, titanium, aluminum, silicon, or the like. After the second electrode 142 is formed, the second electrode 142 and the silicon carbide epitaxial substrate 100 are heated at a temperature of, for example, about 900 to 1100 ° C. As a result, the second electrode 142 and the silicon carbide epitaxial substrate 100 come into ohmic contact. Next, the wiring layer 138 is formed so as to be in contact with the second electrode 142. The wiring layer 138 is made of a material containing, for example, aluminum.

Next, the third electrode 143 is formed on the third main surface 13. The third electrode 143 functions as a drain electrode. The third electrode 143 is composed of, for example, an alloy containing nickel and silicon (for example, NiSi).

Next, a dicing step (S24: FIG. 9) is carried out. For example, the silicon carbide epitaxial substrate 100 is divided into a plurality of semiconductor chips by dicing the silicon carbide epitaxial substrate 100 along the dicing line. From the above, the silicon carbide semiconductor device 300 is manufactured (see FIG. 12).

In the above, the manufacturing method of the silicon carbide semiconductor device according to the present disclosure has been described by exemplifying the MOSFET, but the manufacturing method according to the present disclosure is not limited to this. The manufacturing method according to the present disclosure can be applied to various silicon carbide semiconductor devices such as IGBTs (Insulated Gate Bipolar Transformers), SBDs (Schottky Barrier Diodes), thyristors, GTOs (Gate Turn Off thyristors), and PiN diodes.

The embodiments disclosed this time should be considered as exemplary in all respects and not 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 the meaning equivalent to the scope of claims and all modifications within the scope.

3, 4, 6 Straight line 5 1st flat 7 Arc part 10 Silicon carbide single crystal substrate 11 1st main surface 13 3rd main surface 14 4th main surface (plane)
15 Outer buffer area 16 Central buffer area 17 Outer peripheral deep layer area 18 Central deep layer area 19 Outer surface layer area 20 Silicon carbide layer 21 Buffer layer 22 Deep area 23 Surface layer area 24 Drift layer 25 Central surface layer 26 Outer silicon carbide region 27 Central silicon carbide region (part)
30 Second main surface 31 Outer edge 32 Outer edge area 33 Central area 34 Concentric circle 35 Center 51 Rotating meter 52 Control unit 54 Gas supply source 61, 62 Bottom surface 63 Gas ejection hole 64 Flow path 65, 67 Side surface 68 Recession 100 Silicon carbide epitaxial substrate 101 1st direction 102 2nd direction 103 Circumferential direction 111 Maximum diameter 131 Drift area 132 Body area 133 Source area 134 Contact area 136 Oxidation film 137 Interlayer insulation film 138 Wiring layer 141 1st electrode 142 2nd electrode 143 3rd electrode 200 Manufacturing Equipment 201 Reaction chamber 202 Preheating mechanism 203 Heating element 204 Quartz tube 205 Insulation material 206 Induction heating coil 207 Gas inlet 208 Gas exhaust port 210 Suceptor plate 211 Preheating mechanism 212 Rotating shaft 300 Silicon carbide semiconductor device

Claims (14)

Silicon carbide single crystal substrate including the first main surface and
The silicon carbide epitaxial layer on the first main surface is provided.
The silicon carbide epitaxial layer includes a second main surface opposite to the surface in contact with the silicon carbide single crystal substrate.
The dopant of the silicon carbide epitaxial layer is nitrogen.
The maximum diameter of the second main surface is 100 mm or more.
The second main surface has an outer peripheral region within 5 mm from the outer edge of the second main surface and a central region surrounded by the outer peripheral region.
The silicon carbide epitaxial layer has a central surface layer including the central region.
The central surface layer is a region within 5 μm from the central region toward the first main surface.
The average value of the carrier concentration in the central surface layer is 1 × 10 ¹⁴ cm ^-3 or more and 5 × 10 ¹⁶ cm ^-3 or less.
The circumferential uniformity of the carrier concentration passes through a position where a line segment connecting the boundary line between the outer peripheral region and the central region and the center of the second main surface is equally divided into five, and is centered on the center. It is 2% or less in the outermost circle of the five concentric circles.
The average value of the thickness of the portion of the silicon carbide epitaxial layer sandwiched between the central region and the silicon carbide single crystal substrate is 5 μm or more.
The circumferential uniformity of the carrier concentration is the ratio of the absolute value of the difference between the maximum value and the minimum value of the carrier concentration of the central surface layer in the circumferential direction to the average value of the carrier concentration of the central surface layer in the circumferential direction. There is a silicon carbide epitaxial substrate. Silicon carbide single crystal substrate including the first main surface and
The silicon carbide epitaxial layer on the first main surface is provided.
The silicon carbide epitaxial layer includes a second main surface opposite to the surface in contact with the silicon carbide single crystal substrate.
The dopant of the silicon carbide epitaxial layer is nitrogen.
The maximum diameter of the second main surface is 100 mm or more.
The second main surface has an outer peripheral region within 5 mm from the outer edge of the second main surface and a central region surrounded by the outer peripheral region.
The silicon carbide epitaxial layer has a central surface layer including the central region.
The central surface layer is a region within 5 μm from the central region toward the first main surface.
The average value of the carrier concentration in the central surface layer is 1 × 10 ¹⁴ cm ^-3 or more and 5 × 10 ¹⁶ cm ^-3 or less.
The average value of the thickness of the portion of the silicon carbide epitaxial layer sandwiched between the central region and the silicon carbide single crystal substrate is 5 μm or more.
The circumferential uniformity of the thickness passes through a position where a line segment connecting the boundary line between the outer peripheral region and the central region and the center of the second main surface is equally divided into five equal parts, and the center is the center. It is 1% or less in the outermost circle of the five concentric circles.
The circumferential uniformity of the thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the portion in the circumferential direction to the average value of the thickness of the portion in the circumferential direction. Silicon carbide epitaxial substrate. Silicon carbide single crystal substrate including the first main surface and
The silicon carbide epitaxial layer on the first main surface is provided.
The silicon carbide epitaxial layer includes a second main surface opposite to the surface in contact with the silicon carbide single crystal substrate.
The dopant of the silicon carbide epitaxial layer is nitrogen.
The maximum diameter of the second main surface is 100 mm or more.
The second main surface has an outer peripheral region within 5 mm from the outer edge of the second main surface and a central region surrounded by the outer peripheral region.
The silicon carbide epitaxial layer has a central surface layer including the central region.
The central surface layer is a region within 5 μm from the central region toward the first main surface.
The average value of the carrier concentration in the central surface layer is 1 × 10 ¹⁴ cm ^-3 or more and 5 × 10 ¹⁶ cm ^-3 or less.
The circumferential uniformity of the carrier concentration passes through a position where a line segment connecting the boundary line between the outer peripheral region and the central region and the center of the second main surface is equally divided into five, and is centered on the center. 2% or less in each of the five concentric circles
The average value of the thickness of the portion of the silicon carbide epitaxial layer sandwiched between the central region and the silicon carbide single crystal substrate is 5 μm or more.
The circumferential uniformity of the carrier concentration is the ratio of the absolute value of the difference between the maximum value and the minimum value of the carrier concentration of the central surface layer in the circumferential direction to the average value of the carrier concentration of the central surface layer in the circumferential direction. There is a silicon carbide epitaxial substrate. The in-plane uniformity of the carrier concentration is 10% or less.
The in-plane uniformity of the carrier concentration is the difference between the maximum value and the minimum value of the carrier concentration of the central surface layer in the entire central region with respect to the average value of the carrier concentration of the central surface layer in the entire central region. The silicon carbide epitaxial substrate according to claim 3, which is a ratio of absolute values of. The in-plane uniformity of the thickness is 4% or less.
The in-plane uniformity of the thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the portion in the entire central region to the average value of the thickness of the portion in the entire central region. , The silicon carbide epitaxial substrate according to claim 4. Silicon carbide single crystal substrate including the first main surface and
The silicon carbide epitaxial layer on the first main surface is provided.
The silicon carbide epitaxial layer includes a second main surface opposite to the surface in contact with the silicon carbide single crystal substrate.
The dopant of the silicon carbide epitaxial layer is nitrogen.
The maximum diameter of the second main surface is 100 mm or more.
The second main surface has an outer peripheral region within 5 mm from the outer edge of the second main surface and a central region surrounded by the outer peripheral region.
The silicon carbide epitaxial layer has a central surface layer including the central region.
The central surface layer is a region within 5 μm from the central region toward the first main surface.
The average value of the carrier concentration in the central surface layer is 1 × 10 ¹⁴ cm ^-3 or more and 5 × 10 ¹⁶ cm ^-3 or less.
The average value of the thickness of the portion of the silicon carbide epitaxial layer sandwiched between the central region and the silicon carbide single crystal substrate is 5 μm or more.
The circumferential uniformity of the thickness passes through a position where a line segment connecting the boundary line between the outer peripheral region and the central region and the center of the second main surface is divided into five equal parts, and the center is the center. 1% or less in each of the five concentric circles
The circumferential uniformity of the thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the portion in the circumferential direction to the average value of the thickness of the portion in the circumferential direction. Silicon carbide epitaxial substrate. The in-plane uniformity of the thickness is 4% or less.
The in-plane uniformity of the thickness is the ratio of the absolute value of the difference between the maximum value and the minimum value of the thickness of the portion in the entire central region to the average value of the thickness of the portion in the entire central region. , The silicon carbide epitaxial substrate according to claim 6. The circumferential uniformity of the carrier concentration is 2% or less in each of the five concentric circles.
The circumferential uniformity of the carrier concentration is the ratio of the absolute value of the difference between the maximum value and the minimum value of the carrier concentration of the central surface layer in the circumferential direction to the average value of the carrier concentration of the central surface layer in the circumferential direction. The silicon carbide epitaxial substrate according to claim 7. The silicon carbide epitaxial substrate according to any one of claims 1 to 8, wherein the maximum diameter is 150 mm or more. The silicon carbide epitaxial substrate according to any one of claims 1 to 9, wherein the average value of the carrier concentration is 1 × 10 ¹⁵ cm ^-3 or more and 1 × 10 ¹⁶ cm ^-3 or less. The silicon carbide epitaxial substrate according to any one of claims 1, 3 to 5, and 8, wherein the circumferential uniformity of the carrier concentration is 1% or less. The silicon carbide epitaxial substrate according to claim 4 or 5, wherein the in-plane uniformity of the carrier concentration is 5% or less. The silicon carbide epitaxial substrate according to any one of claims 1 to 12, wherein the second main surface is a surface inclined by 8 ° or less from the {0001} surface. The step of preparing the silicon carbide epitaxial substrate according to any one of claims 1 to 13.
A method for manufacturing a silicon carbide semiconductor device, comprising a step of processing the silicon carbide epitaxial substrate.

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