WO2021215120A1 - 炭化珪素単結晶および炭化珪素単結晶の製造方法 - Google Patents

炭化珪素単結晶および炭化珪素単結晶の製造方法 Download PDF

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WO2021215120A1
WO2021215120A1 PCT/JP2021/008195 JP2021008195W WO2021215120A1 WO 2021215120 A1 WO2021215120 A1 WO 2021215120A1 JP 2021008195 W JP2021008195 W JP 2021008195W WO 2021215120 A1 WO2021215120 A1 WO 2021215120A1
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silicon carbide
single crystal
region
carbide region
main surface
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French (fr)
Japanese (ja)
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省吾 境谷
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Sumitomo Electric Industries Ltd
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Sumitomo Electric Industries Ltd
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Priority to US17/919,222 priority Critical patent/US20230160103A1/en
Priority to CN202180028870.8A priority patent/CN115427615A/zh
Priority to JP2022516876A priority patent/JPWO2021215120A1/ja
Publication of WO2021215120A1 publication Critical patent/WO2021215120A1/ja
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/36—Carbides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
    • C30B23/002—Controlling or regulating
    • C30B23/005—Controlling or regulating flux or flow of depositing species or vapour
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
    • C30B23/02—Epitaxial-layer growth
    • C30B23/06—Heating of the deposition chamber, the substrate or the materials to be evaporated
    • C30B23/063—Heating of the substrate

Definitions

  • the present disclosure relates to a silicon carbide single crystal and a method for producing a silicon carbide single crystal.
  • This application claims priority based on Japanese Patent Application No. 2020-075940, which is a Japanese patent application filed on April 22, 2020. All the contents of the Japanese patent application are incorporated herein by reference.
  • Patent Document 1 describes a method for growing single crystal silicon carbide by a sublimation recrystallization method.
  • the silicon carbide single crystal according to the present disclosure includes a first main surface, a second main surface, a first silicon carbide region, and a second silicon carbide region.
  • the second main surface is on the opposite side of the first main surface and is convex outward.
  • the first silicon carbide region constitutes the first main surface and is between the first main surface and a virtual plane 10 mm away from the first main surface.
  • the second silicon carbide region constitutes the second main surface and is continuous with the first silicon carbide region.
  • Each of the first silicon carbide region and the second silicon carbide region contains a silicon carbide single crystal having a polytype of 4H.
  • the value obtained by dividing the number of void defects in the first silicon carbide region by the total of the number of void defects in the first silicon carbide region and the number of void defects in the second silicon carbide region is 0.8 or more.
  • the major axis of the void defect is 1 ⁇ m or more and 1000 ⁇ m or less.
  • the method for producing a silicon carbide single crystal according to the present disclosure includes the following steps.
  • the silicon carbide seed substrate and the silicon carbide raw material are arranged in the crucible.
  • the silicon carbide seed substrate includes a growth surface facing the silicon carbide raw material and a mounting surface on the opposite side of the growth surface.
  • the first silicon carbide region is formed on the growth surface.
  • the silicon carbide raw material is sublimated while the temperature of the growth surface is 2200 ° C.
  • the pressure in the crucible is 0.5 kPa or less
  • the temperature gradient between the growth surface and the surface of the silicon carbide raw material is 0.4 ° C./mm or less.
  • the second silicon carbide region is formed on the first silicon carbide region.
  • Each of the first silicon carbide region and the second silicon carbide region contains a silicon carbide single crystal having a polytype of 4H.
  • FIG. 1 is a schematic side view showing the structure of a silicon carbide single crystal according to the present embodiment.
  • FIG. 2 is a schematic cross-sectional view taken along the line II-II of FIG.
  • FIG. 3 is a partial cross-sectional schematic view showing the configuration of the silicon carbide single crystal manufacturing apparatus according to the present embodiment.
  • FIG. 4 is a flowchart schematically showing a method for producing a silicon carbide single crystal according to the present embodiment.
  • FIG. 5 is a partial cross-sectional schematic view showing a process of arranging the silicon carbide seed substrate and the silicon carbide raw material in the crucible.
  • FIG. 6 is a partial cross-sectional schematic view showing a step of forming the first silicon carbide region.
  • FIG. 1 is a schematic side view showing the structure of a silicon carbide single crystal according to the present embodiment.
  • FIG. 2 is a schematic cross-sectional view taken along the line II-II of FIG.
  • FIG. 3 is a partial cross-sectional schematic view
  • FIG. 7 is a partial cross-sectional schematic view showing a step of forming the second silicon carbide region.
  • FIG. 8 is a diagram showing the relationship between the growth surface temperature of the silicon carbide seed substrate and the mixing ratio of different polytypes mixed in the silicon carbide single crystal formed on the silicon carbide seed substrate.
  • FIG. 9 is a diagram showing the relationship between the temperature gradient between the growth surface of the silicon carbide type substrate and the surface of the silicon carbide raw material and the aggregation rate of void defects.
  • An object of the present disclosure is to provide a method for producing a silicon carbide single crystal and a silicon carbide single crystal capable of reducing the number of void defects while suppressing the generation of different polytypes.
  • defects of this disclosure According to the present disclosure, it is possible to provide a method for producing a silicon carbide single crystal and a silicon carbide single crystal capable of reducing the number of void defects while suppressing the generation of different polytypes.
  • the silicon carbide single crystal 10 includes a first main surface 1, a second main surface 2, a first silicon carbide region 11, and a second silicon carbide region 12.
  • the second main surface 2 is on the opposite side of the first main surface 1 and is convex outward.
  • the first silicon carbide region 11 constitutes the first main surface 1 and is located between the first main surface 1 and a virtual plane 10 mm away from the first main surface 1.
  • the second silicon carbide region 12 constitutes the second main surface 2 and is connected to the first silicon carbide region 11.
  • Each of the first silicon carbide region 11 and the second silicon carbide region 12 contains a silicon carbide single crystal having a polytype of 4H.
  • the value obtained by dividing the number of void defects 6 in the first silicon carbide region 11 by the total of the number of void defects 6 in the first silicon carbide region 11 and the number of void defects 6 in the second silicon carbide region 12 is 0. 8 or more.
  • the major axis of the void defect 6 is 1 ⁇ m or more and 1000 ⁇ m or less.
  • the thickness of the silicon carbide single crystal 10 may be 30 mm or more in the direction perpendicular to the first main surface 1.
  • the surface density of the void defect 6 in the first silicon carbide region 11 is 0. It may be 1 piece / cm 2 or more.
  • the method for producing a silicon carbide single crystal 10 includes the following steps.
  • the silicon carbide seed substrate 20 and the silicon carbide raw material 23 are arranged in the crucible 30.
  • the silicon carbide seed substrate 20 includes a growth surface 21 facing the silicon carbide raw material 23 and a mounting surface 22 on the opposite side of the growth surface 21.
  • the first silicon carbide region 11 is formed on the growth surface 21. Silicon carbide while the temperature of the growth surface 21 is 2200 ° C.
  • the pressure inside the crucible 30 is 0.5 kPa or lower
  • the temperature gradient between the growth surface 21 and the surface of the silicon carbide raw material 23 is 0.4 ° C./mm or lower.
  • the second silicon carbide region 12 is formed on the first silicon carbide region 11.
  • Each of the first silicon carbide region 11 and the second silicon carbide region 12 contains a silicon carbide single crystal having a polytype of 4H.
  • the thickness of the first silicon carbide region 11 may be 10 mm or less.
  • the thickness of the silicon carbide single crystal 10 may be 30 mm or more.
  • FIG. 1 is a schematic side view showing the structure of a silicon carbide single crystal according to the present embodiment.
  • the silicon carbide single crystal 10 according to the present embodiment has a first main surface 1, a second main surface 2, an outer peripheral surface 5, a first silicon carbide region 11, and a second carbonized product. It mainly has a silicon region 12.
  • the second main surface 2 is on the opposite side of the first main surface 1.
  • the second main surface 2 is convex outward.
  • the first main surface 1 is, for example, a flat surface.
  • the outer peripheral surface 5 is connected to each of the first main surface 1 and the second main surface 2.
  • the silicon carbide single crystal 10 according to this embodiment has a substantially cylindrical shape.
  • the first silicon carbide region 11 constitutes the first main surface 1.
  • the first silicon carbide region 11 is a region within 10 mm from the first main surface 1.
  • the first silicon carbide region 11 is between the first main surface 1 and a virtual plane 10 mm away from the first main surface 1.
  • the thickness of the first silicon carbide region 11 (first thickness T1) is 10 mm in the direction perpendicular to the first main surface 1.
  • the second silicon carbide region 12 constitutes the second main surface 2.
  • the second silicon carbide region 12 is connected to the first silicon carbide region 11.
  • the second silicon carbide region 12 is provided on the first silicon carbide region 11.
  • the outer peripheral surface 5 has a first outer peripheral surface portion 3 and a second outer peripheral surface portion 4.
  • the second outer peripheral surface portion 4 is connected to the first outer peripheral surface portion 3.
  • Each of the first silicon carbide region 11 and the second silicon carbide region 12 contains a silicon carbide single crystal having a polytype of 4H.
  • the first silicon carbide region 11 constitutes the first outer peripheral surface portion 3.
  • the second silicon carbide region 12 constitutes the second outer peripheral surface portion 4.
  • the thickness of the second silicon carbide region 12 (second thickness T2) is, for example, 20 mm or more in the direction perpendicular to the first main surface 1.
  • the thickness of the silicon carbide single crystal 10 (third thickness T3) is, for example, 30 mm or more in the direction perpendicular to the first main surface 1.
  • the lower limit of the third thickness T3 is not particularly limited, but may be, for example, 35 mm or more, or 40 mm or more.
  • a void defect 6 is present in each of the first silicon carbide region 11 and the second silicon carbide region 12.
  • the void defect 6 is a hollow defect formed by being confined in the silicon carbide region. In other words, the void defect 6 is not exposed on the outer surface of the silicon carbide region.
  • the void defect 6 is substantially spherical.
  • the shape of the void defect 6 is, for example, an ellipse.
  • the major axis of the shape of the void defect 6 is, for example, 1 ⁇ m or more and 1000 ⁇ m or less.
  • the value obtained by dividing the number of void defects 6 in the first silicon carbide region 11 by the total of the number of void defects 6 in the first silicon carbide region 11 and the number of void defects 6 in the second silicon carbide region 12 is 0. 8 or more. From another point of view, 80% or more of the total number of void defects 6 present in the silicon carbide single crystal 10 is present in the first silicon carbide region 11. The number of void defects 6 present in the second silicon carbide region 12 is less than 20% of the total number of void defects 6 present in the silicon carbide single crystal 10.
  • the lower limit of the value obtained by dividing the number of void defects 6 in the first silicon carbide region 11 by the total of the number of void defects 6 in the first silicon carbide region 11 and the number of void defects 6 in the second silicon carbide region 12 is Although not particularly limited, for example, it may be 0.85 or more, 0.90 or more, or 0.95 or more.
  • FIG. 2 is a schematic cross-sectional view taken along the line II-II of FIG.
  • the first silicon carbide region 11 is substantially circular when viewed in a direction perpendicular to the first main surface 1.
  • the second silicon carbide region 12 is substantially circular when viewed in a direction perpendicular to the first main surface 1.
  • the diameter W of the first silicon carbide region 11 is, for example, 150 mm.
  • the lower limit of the diameter W is not particularly limited, but may be, for example, 100 mm or more.
  • the upper limit of the diameter W is not particularly limited, but may be, for example, 200 mm or less, or 300 mm or less.
  • the surface density of the void defects 6 in the first silicon carbide region 11 may be 0.1 pieces / cm 2 or more.
  • the lower limit of the surface density of the void defect 6 in the first silicon carbide region 11 is not particularly limited , but may be, for example, 0.5 pieces / cm 2 or more, or 1 piece / cm 2 or more.
  • the upper limit of the surface density of the void defect 6 in the first silicon carbide region 11 is not particularly limited , but may be, for example, 10 pieces / cm 2 or less, or 5 pieces / cm 2 or less.
  • the surface density of the void defect 6 in the first silicon carbide region 11 may be large, and the surface density of the void defect 6 in the second silicon carbide region 12 may be large.
  • Void defects 6 can be observed using, for example, a transmission optical microscope.
  • a silicon carbide single crystal substrate cut out from the silicon carbide single crystal 10 using a multi-wire saw is observed with a transmission optical microscope, void defects 6 existing in the silicon carbide single crystal substrate are identified, and the number thereof is measured.
  • NS By measuring the number of void defects 6 for all silicon carbide single crystal substrates using this method, the number of void defects 6 existing in the first silicon carbide region 11 and the second silicon carbide region 12 can be obtained. ..
  • the areal density of the void defects 6 in the first silicon carbide region 11 is the cross-sectional area of the first silicon carbide region 11 in a cross section parallel to the first main surface 1 based on the number of void defects 6 existing in the first silicon carbide region 11. It is the value divided by.
  • the areal density of the void defects 6 in the second silicon carbide region 12 is the number of void defects 6 present in the second silicon carbide region 12 as the second silicon carbide region 12 in the cross section parallel to the first main surface 1. It is a value divided by the cross-sectional area of.
  • FIG. 3 is a partial cross-sectional schematic view showing the configuration of the silicon carbide single crystal manufacturing apparatus according to the present embodiment.
  • the silicon carbide single crystal manufacturing apparatus 100 mainly includes a chamber 50, a crucible 30, and a heater 40.
  • the crucible 30 and the heater 40 are arranged inside the chamber 50.
  • the crucible 30 has a raw material accommodating portion 32 and a lid portion 31.
  • the lid portion 31 is arranged on the raw material accommodating portion 32.
  • the heater 40 is, for example, a resistance heater. A voltage is applied to the heater 40 from an external power source (not shown). As a result, the heater 40 itself generates heat and heats the crucible 30.
  • the heater 40 has, for example, a first resistance heater 41, a second resistance heater 42, and a third resistance heater 43.
  • the first resistance heater 41 is arranged above the lid portion 31.
  • the second resistance heater 42 is arranged so as to surround the outer peripheral surface 5 of the raw material accommodating portion 32.
  • the third resistance heater 43 is arranged below the raw material accommodating portion 32.
  • a radiation thermometer (not shown) may be arranged outside the chamber 50.
  • FIG. 4 is a flowchart schematically showing a method for producing a silicon carbide single crystal according to the present embodiment.
  • a step (S1) of arranging a silicon carbide seed substrate and a silicon carbide raw material in a crucible and forming a first silicon carbide region are formed. It mainly has a step (S2) of forming a second silicon carbide region and a step (S3) of forming a second silicon carbide region.
  • FIG. 5 is a partial cross-sectional schematic view showing a process of arranging the silicon carbide seed substrate 20 and the silicon carbide raw material 23 in the crucible 30.
  • the silicon carbide raw material 23 is arranged in the raw material accommodating portion 32.
  • the silicon carbide raw material 23 is, for example, a powder of polycrystalline silicon carbide.
  • the silicon carbide seed substrate 20 is fixed to the lid 31 using, for example, an adhesive (not shown).
  • the silicon carbide seed substrate 20 has a growth surface 21 and a mounting surface 22.
  • the mounting surface 22 is on the opposite side of the growth surface 21.
  • the growth surface 21 faces the silicon carbide raw material 23.
  • the mounting surface 22 faces the lid portion 31.
  • the silicon carbide seed substrate 20 is arranged so that the growth surface 21 faces the surface of the silicon carbide raw material 23.
  • the silicon carbide seed substrate 20 is, for example, a polytype 4H hexagonal silicon carbide single crystal.
  • the diameter of the growth surface 21 is, for example, 150 mm.
  • the diameter of the growth surface 21 may be 150 mm or more.
  • the growth surface 21 is, for example, a surface inclined by an off angle of about 8 ° or less with respect to the ⁇ 0001 ⁇ surface or the ⁇ 0001 ⁇ surface.
  • the silicon carbide seed substrate 20 and the silicon carbide raw material 23 are arranged in the crucible 30.
  • FIG. 6 is a partial cross-sectional schematic view showing a step of forming the first silicon carbide region.
  • the growth surface 21 is heated until it reaches a temperature of, for example, 2100 ° C or higher and lower than 2200 ° C.
  • the lower limit of the temperature of the growth surface 21 is not particularly limited, but may be, for example, 2110 ° C. or higher, or 2120 ° C. or higher.
  • the upper limit of the temperature of the growth surface 21 is not particularly limited, but may be, for example, 2190 ° C. or lower, or 2180 ° C. or lower.
  • the pressure of the atmospheric gas in the crucible 30 is maintained at, for example, about 80 kPa.
  • the atmospheric gas contains an inert gas such as argon gas, helium gas or nitrogen gas.
  • the temperature of the growth surface 21 can be calculated by finite element analysis of the temperature distribution in the furnace based on, for example, the temperature of the outer wall of the rutsubo measured by a radiation thermometer.
  • 41 parts of the first resistance heater and 42 parts of the second resistance heater so that the temperature gradient between the growth surface 21 of the silicon carbide seed substrate 20 and the surface of the silicon carbide raw material 23 is, for example, more than 0.4 ° C./mm.
  • the voltage applied to each of the 43 parts of the third resistance heater is controlled.
  • the pressure of the atmospheric gas in the crucible 30 is reduced to, for example, 1.0 kPa.
  • the silicon carbide raw material 23 in the accommodating portion starts sublimation, and the sublimated silicon carbide gas is recrystallized on the growth surface 21 of the silicon carbide seed substrate 20.
  • the first silicon carbide region 11 begins to grow on the growth surface 21 of the silicon carbide seed crystal. While the first silicon carbide region 11 is growing, the pressure in the crucible 30 is maintained, for example, about 0.1 kPa or more and 3 kPa or less.
  • the pressure in the crucible 30 is measured, for example, using a pressure gauge (not shown) attached to the chamber 50.
  • the first silicon carbide region 11 is formed on the growth surface 21 (see FIG. 6).
  • the first silicon carbide region 11 contains a silicon carbide single crystal having a polytype of 4H.
  • the thickness of the first silicon carbide region 11 (first thickness T1) is, for example, 10 mm or less.
  • the upper limit of the thickness of the first silicon carbide region 11 is not particularly limited, but may be, for example, 8 mm or less, or 6 mm or less.
  • FIG. 7 is a partial cross-sectional schematic view showing a step of forming the second silicon carbide region.
  • the temperature of the growth surface 21 in the step of forming the second silicon carbide region (S3) is set to be higher than the temperature of the growth surface 21 in the step of forming the first silicon carbide region (S2). Specifically, the temperature of the growth surface 21 in the step (S3) of forming the second silicon carbide region is 2200 ° C. or higher.
  • the lower limit of the temperature of the growth surface 21 in the step (S3) of forming the second silicon carbide region is not particularly limited, but may be, for example, 2210 ° C. or higher, or 2220 ° C. or higher.
  • the pressure in the crucible 30 in the step (S3) of forming the second silicon carbide region is, for example, 0.5 kPa or less.
  • the upper limit of the pressure in the crucible 30 in the step (S3) of forming the second silicon carbide region is not particularly limited, but may be, for example, 0.4 kPa or less, or 0.3 kPa or less.
  • the temperature gradient between the growth surface 21 and the surface 24 of the silicon carbide raw material 23 is 0.4 ° C./mm or less.
  • the upper limit of the temperature gradient between the growth surface 21 and the surface 24 of the silicon carbide raw material 23 is not particularly limited, but may be, for example, 0.35 ° C./mm or less, or 0.3 ° C./mm or less. good.
  • the silicon carbide raw material 23 in the accommodating portion is sublimated, and the sublimated silicon carbide gas is recrystallized on the first silicon carbide region 11.
  • the temperature of the growth surface 21 is set to 2200 ° C. or higher
  • the pressure inside the crucible 30 is set to 0.5 kPa or lower
  • the temperature gradient between the growth surface 21 and the surface of the silicon carbide raw material 23 is 0.4 ° C./mm.
  • the second silicon carbide region 12 contains a silicon carbide single crystal having a polytype of 4H.
  • the thickness of the silicon carbide single crystal 10 (third thickness T3) is, for example, 30 mm or more.
  • the lower limit of the thickness of the silicon carbide single crystal 10 is not particularly limited, but may be, for example, 35 mm or more, or 40 mm or more.
  • the heater 40 is a resistance heater
  • the heater 40 is not limited to the resistance heater.
  • the heater may be, for example, an induction heating coil.
  • a silicon carbide single crystal having a polytype of 6H is more stable than a silicon carbide single crystal having a polytype of 4H. Therefore, when producing a silicon carbide single crystal having a polytype of 4H, it is desirable to lower the temperature of the growth surface in order to prevent the silicon carbide single crystal having a polytype of 6H from being mixed.
  • thermodynamically stable ⁇ 11-20 ⁇ planes or ⁇ 1-100 ⁇ planes are likely to be generated. Therefore, for example, when the growth surface 7 is a ⁇ 0001 ⁇ plane, it is considered that the void defect 6 is likely to occur due to an increase in the height of the plane perpendicular to the growth surface 7.
  • the temperature environment near the growth surface or the gas composition deviates from the appropriate conditions, so that silicon droplets are generated, and silicon diffuses into the crystal during growth, resulting in void defects 6. It is also possible that it will be formed. Further, when the temperature gradient in the vertical direction (growth direction) becomes large, sublimation and recrystallization proceed inside the void defect 6.
  • the void defects 6 move to the growth surface 7 side, and the void defects 6 are distributed over a wide region of the silicon carbide single crystal.
  • the region through which the void defect 6 has passed has a worse crystallinity than the region through which the void defect 6 has not passed.
  • the growth surface 21 is formed by sublimating the silicon carbide raw material 23 while keeping the temperature of the growth surface 21 of the silicon carbide seed substrate 20 at 2100 ° C. or higher and lower than 2200 ° C.
  • the first silicon carbide region 11 is formed on the top.
  • the first silicon carbide region 11 having a convex surface on the outside can be formed while suppressing the mixing of the silicon carbide single crystal having a polytype of 6H.
  • the first silicon carbide region 11 although the void defect 6 is generated, the growth of the silicon carbide single crystal having a polytype of 4H becomes stable. As a result, in the silicon carbide single crystal 10, mixing of different polytypes such as 6H can be suppressed.
  • the temperature of the growth surface 21 is set to 2200 ° C. or higher, the pressure in the crucible 30 is set to 0.5 kPa or lower, and the temperature gradient between the growth surface 21 and the surface 24 of the silicon carbide raw material 23 is 0.4 ° C./mm or lower.
  • the second silicon carbide region 12 is formed on the first silicon carbide region 11.
  • the temperature of the growth surface 21 is increased, the temperature gradient between the growth surface 21 and the surface 24 of the silicon carbide raw material 23 decreases, so that the growth rate decreases. Therefore, by lowering the pressure in the crucible 30, the silicon carbide raw material 23 is likely to sublimate, so that it is possible to prevent a decrease in the growth rate of the silicon carbide single crystal.
  • the temperature gradient inside the void defect 6 is also lowered. Therefore, it is possible to suppress the occurrence of sublimation and recrystallization inside the void defect 6. As a result, it is possible to prevent the void defect 6 from moving toward the growth surface 7 (see FIG. 7). Therefore, the occurrence of void defects 6 can be suppressed in the second silicon carbide region 12 that has grown in the late stage of growth.
  • the first silicon carbide region 11 constitutes the first main surface 1 and is within 10 mm from the first main surface 1.
  • the second silicon carbide region 12 constitutes the second main surface 2 and is connected to the first silicon carbide region 11.
  • the value obtained by dividing the number of void defects 6 in the first silicon carbide region 11 by the total of the number of void defects 6 in the first silicon carbide region 11 and the number of void defects 6 in the second silicon carbide region 12 is 0. 8 or more. This makes it possible to secure a large number of silicon carbide single crystal substrates from which devices can be manufactured.
  • a silicon carbide single crystal 10 was formed on the silicon carbide seed substrate 20.
  • the temperature of the growth surface 21 of the silicon carbide seed substrate 20 was set to 2125 ° C., 2150 ° C., 2175 ° C., 2200 ° C., 2225 ° C. and 2250 ° C., respectively.
  • the pressure of the crucible 30 was set to more than 0.5 kPa.
  • the temperature gradient between the growth surface 21 of the silicon carbide seed substrate 20 and the surface 24 of the silicon carbide raw material 23 was set to more than 0.4 ° C./mm.
  • the voltage applied to each of the first resistance heater 41 part, the second resistance heater 42 part, and the third resistance heater 43 part was controlled so as to satisfy the above growth condition.
  • the polytype of the target silicon carbide single crystal 10 is 4H.
  • the main heterogeneous polytype is 6H.
  • the mixing ratio of different polytypes was determined.
  • the mixing rate of different polytypes is the probability that polytypes other than 4H are mixed in the grown silicon carbide single crystal. That is, it is the ratio obtained by dividing the number of grown silicon carbide single crystals mixed with polytypes other than 4H by the total number of grown silicon carbide single crystals.
  • the method for measuring the mixing rate of different types of polytypes is as follows.
  • the polytype measurement is, for example, a method of processing a silicon carbide single crystal into a wafer and then taking a transmission optical microscope image to discriminate by the difference in color, and a method of discriminating by the contrast of a photoluminescence (PL) imaging image.
  • PL photoluminescence
  • FIG. 8 shows the relationship between the growth surface temperature of the silicon carbide seed substrate 20 and the mixing ratio of different polytypes mixed in the first silicon carbide region 11 of the silicon carbide single crystal 10 formed on the silicon carbide seed substrate 20. It is a figure which shows.
  • Table 1 shows the data of FIG. As shown in FIG. 8 and Table 1, as the temperature of the growth surface 21 decreases, the mixing rate of different polytypes decreases. By setting the temperature of the growth surface 21 to less than 2200 ° C., the mixing rate of different types of polytypes can be significantly reduced.
  • the silicon carbide single crystal 10 was formed on the silicon carbide seed substrate 20 using the growth conditions of Samples 2-1 to 2-6.
  • the temperature gradients between the growth surface 21 of the silicon carbide seed substrate 20 and the surface 24 of the silicon carbide raw material 23 under the growth conditions of Samples 2-1 to 2-6 are 0.2 ° C./mm and 0.4, respectively.
  • the temperature was defined as ° C./mm, 0.6 ° C./mm, 0.8 ° C./mm, 1 ° C./mm and 1.2 ° C./mm.
  • the pressure of the crucible 30 was 0.5 kPa.
  • the growth surface 21 of the silicon carbide seed substrate 20 was set to 2150 ° C.
  • the voltage applied to each of the first resistance heater 41 part, the second resistance heater 42 part, and the third resistance heater 43 part was controlled so as to satisfy the above growth condition.
  • FIG. 9 is a diagram showing the relationship between the temperature gradient between the growth surface 21 of the silicon carbide seed substrate 20 and the surface 24 of the silicon carbide raw material 23 and the aggregation rate of void defects 6.
  • Table 2 shows the data of FIG.
  • the number of void defects 6 in the first silicon carbide region 11 within 10 mm from the growth surface 21 is the number of void defects 6 existing in the entire silicon carbide single crystal 10 (first silicon carbide region 11 and second silicon carbide region 12). It is the value divided by the total number.
  • the aggregation rate of the void defect 6 increases.
  • the aggregation rate of void defects 6 can be significantly increased.
  • the silicon carbide single crystal 10 was produced on the silicon carbide seed substrate 20 using the growth conditions of Samples 3-1 to 3-4.
  • the method for producing the silicon carbide single crystal 10 includes a step of forming the first silicon carbide region (S2) and a step of forming the second silicon carbide region (S3).
  • the growth conditions of Samples 3-1 to 3-4 are shown in Table 3.
  • the voltage applied to each of the first resistance heater 41 part, the second resistance heater 42 part, and the third resistance heater 43 part was controlled so as to satisfy the growth conditions shown in Table 3.
  • the growth conditions of sample 3-1 are examples.
  • the growth conditions of Samples 3-2 to 3-4 are comparative examples.
  • the aggregation rate of void defects 6 in the silicon carbide single crystal 10 formed using the growth conditions of sample 3-1 uses the growth conditions of samples 3-2 to 3-4. It was significantly higher than the aggregation rate of the void defects 6 in the silicon carbide single crystal 10 formed in the above. From the above results, in the step (S2) of forming the first silicon carbide region, the silicon carbide raw material 23 is sublimated while keeping the temperature of the growth surface 21 at 2100 ° C. or higher and lower than 2200 ° C., and the second silicon carbide region is formed. In the step (S3), the temperature of the growth surface 21 is set to 2200 ° C.
  • the pressure inside the pit 30 is set to 0.5 kPa or lower, and the temperature gradient between the growth surface 21 and the surface 24 of the silicon carbide raw material 23 is 0.4. It was confirmed that the aggregation rate of the void defect 6 can be significantly increased by sublimating the silicon carbide raw material 23 at a temperature of ° C./mm or less.

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