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WO2020077847A1 - 大尺寸高纯碳化硅单晶、衬底及其制备方法和制备用装置 - Google Patents

大尺寸高纯碳化硅单晶、衬底及其制备方法和制备用装置 Download PDF

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Publication number
WO2020077847A1
WO2020077847A1 PCT/CN2018/123708 CN2018123708W WO2020077847A1 WO 2020077847 A1 WO2020077847 A1 WO 2020077847A1 CN 2018123708 W CN2018123708 W CN 2018123708W WO 2020077847 A1 WO2020077847 A1 WO 2020077847A1
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WIPO (PCT)
Prior art keywords
crucible
silicon carbide
single crystal
carbide single
heat preservation
Prior art date
Application number
PCT/CN2018/123708
Other languages
English (en)
French (fr)
Inventor
高超
刘家朋
刘鹏飞
李长进
李加林
孙元行
李宏刚
Original Assignee
山东天岳先进材料科技有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Priority claimed from CN201821676275.7U external-priority patent/CN209144309U/zh
Priority claimed from CN201811204726.1A external-priority patent/CN109280976B/zh
Priority claimed from CN201811204668.2A external-priority patent/CN109280964B/zh
Application filed by 山东天岳先进材料科技有限公司 filed Critical 山东天岳先进材料科技有限公司
Priority to EP18922089.0A priority Critical patent/EP3666933A4/en
Priority to KR1020197037936A priority patent/KR102331308B1/ko
Priority to JP2019571512A priority patent/JP6937525B2/ja
Publication of WO2020077847A1 publication Critical patent/WO2020077847A1/zh

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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
    • 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
    • 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
    • C30B23/066—Heating of the material to be evaporated
    • 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
    • C30B35/00—Apparatus not otherwise provided for, specially adapted for the growth, production or after-treatment of single crystals or of a homogeneous polycrystalline material with defined structure
    • C30B35/002—Crucibles or containers

Definitions

  • the most mature silicon carbide single crystal preparation technology is the physical vapor transport method (PVT method for short).
  • the basic principle is that the graphite crucible placed in the center of the coil is heated by intermediate frequency induction.
  • the graphite crucible wall transfers heat to the interior after induction heating.
  • a continuous circular hole is provided in the center of the graphite insulation felt on the upper side of the graphite crucible.
  • the heat is dissipated through the circular hole, resulting in an axial temperature gradient of high temperature in the lower part of the crucible and low temperature in the upper part, driving sublimation
  • the gas phase is transferred from the powder zone in the growth chamber to the seed zone at the top of the crucible for crystallization.
  • the silicon carbide single crystal prepared by this method has been developed from 2 inches to 8 inches and is continuously used in downstream devices.
  • the diameter of the crucible also increases. Since the crucible wall is used as the heat source in the medium frequency induction heating method, the radial temperature gradient along the crucible wall and the center of the crucible also increases continuously; in addition, the PVT method produces an axial temperature gradient by using the central thermal insulation hole on the upper side of the crucible as the heat dissipation center This will further cause the unevenness of the thermal field inside the crucible in the radial direction, resulting in large thermal stresses in the radial direction of the crystal and uneven distribution of impurities and defects.
  • the thermal stress existing in the former is likely to cause serious quality problems such as cracking during crystal processing, unqualified curvature and warpage during substrate processing, and uneven distribution of impurities and defects in the latter will also seriously restrict the substrate along the diameter. To the uniformity of resistivity.
  • one party of the present application provides a device for growing silicon carbide single crystals.
  • This device redesigns the crucible and the thermal insulation structure wrapped around the periphery of the graphite crucible to form a uniform thermal field in the radial direction, thereby improving silicon carbide
  • the radial uniformity of the single crystal makes it possible to prepare high-quality large-size, high-purity, semi-insulating silicon carbide single crystal substrates.
  • the device for growing silicon carbide single crystal includes a graphite crucible, a heating unit, a seed crystal unit and an insulation structure, characterized in that the insulation structure includes a top of the insulation structure, a side of the insulation structure and a bottom of the insulation structure, In a substantially cylindrical shape, the side wall of the graphite crucible is linearly thickened along the direction from the bottom of the graphite crucible to the opening.
  • the seed crystal unit is provided at a position above the opening of the graphite crucible, the thermal insulation structure does not have an opening structure, and the seed crystal unit includes a carbonized single crystal seed crystal.
  • the graphite crucible is located in a closed cavity of the thermal insulation structure.
  • the opening cross section of the graphite crucible has a first distance to the inner surface of the top of the thermal insulation structure above it, and the first distance increases along the direction from the center of the graphite crucible to the edge of the graphite crucible.
  • the heating unit heats the graphite crucible by induction heating.
  • the heating unit includes an intermediate frequency coil.
  • the graphite crucible and the thermal insulation structure share a first central axis
  • the first central axis is parallel to the inner surface of the side wall of the graphite crucible and / or the outer surface of the side of the thermal insulation structure;
  • the first central axis has a first angle with the outer surface of the side wall of the graphite crucible, and the first central axis has a second angle with the inner surface of the side of the thermal insulation structure, the first angle and the second angle
  • the value is 5-30 °.
  • the lower limit of the value of the first included angle and the second included angle is selected from 7 °, 10 °, 13 °, or 15 °
  • the upper limit is selected from 28 °, 25 °, 23 °, 20 °, or 18 °.
  • the values of the first included angle and the second included angle are 10-25 °.
  • the first included angle and the second included angle are substantially equal.
  • the opening cross section of the graphite crucible has a first distance to the inner surface of the top of the thermal insulation structure above it, and the first distance increases along the center of the graphite crucible to the edge of the graphite crucible.
  • the top of the heat preservation structure is dome-shaped.
  • the value of the change value of the first distance is 5-50 mm.
  • the lower limit of the range of the change value of the first distance is selected from 10 mm, 15 mm, 20 mm, 25 mm, or 30 mmm, and the upper limit is selected from 15 mm, 20 mm, 25 mm, 30 mmm, 35 mm, 40 mm, or 45 mm.
  • the range of the change value of the first distance is 10-45 mm.
  • the outer surface of the heat preservation structure is a cylinder, and the top of the heat preservation structure does not have an opening; the inner surface of the bottom of the heat preservation structure is roughly cylindrical; along the bottom of the graphite crucible to the direction of its opening, the heat preservation structure The surface extends in a direction away from the central axis of the graphite crucible; the top of the insulation structure thickens along the direction from the edge of the graphite crucible to the center.
  • the inner surface of the side wall of the graphite crucible is substantially cylindrical, and the outer wall of the graphite crucible has substantially the same extension direction as the inner surface of the side portion of the thermal insulation structure.
  • a crystal growth device characterized by comprising the device described in any one of the above.
  • the crystal growth device is used to prepare a semi-insulating silicon carbide single crystal with a diameter of 4-12 inches and its substrate. Further, the crystal growth device is used to prepare a semi-insulating silicon carbide single crystal with a diameter greater than 8 inches and less than or equal to 12 inches and its substrate.
  • the present application provides a thermal field structure for growing silicon carbide single crystals.
  • the thermal field structure forms a radially uniform thermal field by redesigning the crucible and the thermal insulation structure wrapped around the crucible The structure, thereby improving the radial uniformity of the silicon carbide single crystal, making it possible to prepare a high-quality large-size high-purity semi-insulating silicon carbide single crystal substrate.
  • the thermal field structure of the silicon carbide single crystal growth includes a crucible, a heating unit and an insulation structure, characterized in that the insulation structure includes an insulation structure top, an insulation structure side and an insulation structure bottom, and the crucible is located in a sealed cavity of the insulation structure in vivo;
  • the wall thickness of the side wall opening area of the crucible is greater than the wall thickness of the bottom area.
  • the crucible and the heat preservation structure make the crucible have an axial temperature gradient, and / or a radial temperature gradient close to zero.
  • the crucible is a graphite crucible.
  • the side wall of the crucible is linearly thickened along the direction from the bottom of the crucible to the opening.
  • the side wall of the thermal insulation structure is linearly thickened along the direction from the opening of the crucible to the bottom.
  • the opening cross section of the crucible has a first distance to the inner surface of the top of the thermal insulation structure above it, and the first distance increases from the center of the crucible to the edge of the crucible.
  • the value of the change value of the first distance is 5-50 mm.
  • the lower limit of the range of the change value of the first distance is selected from 10 mm, 15 mm, 20 mm, 25 mm, or 30 mmm
  • the upper limit is selected from 15 mm, 20 mm, 25 mm, 30 mmm, 35 mm, 40 mm, or 45 mm.
  • the crucible and the thermal insulation structure generally share a first central axis
  • the first central axis is substantially parallel to the inner surface of the side wall of the crucible and / or the outer surface of the side portion of the thermal insulation structure;
  • the first central axis has a first angle with the outer surface of the side wall of the crucible, and the first central axis has a second angle with the inner surface of the side of the thermal insulation structure, the first angle and the second angle ⁇ 90 ° .
  • the crucible and the thermal insulation structure share a first central axis
  • the first central axis is parallel to the inner surface of the side wall of the crucible and / or the outer surface of the side of the heat preservation structure;
  • the first central axis has a first angle with the outer surface of the side wall of the crucible, and the first central axis has a second angle with the inner surface of the side of the thermal insulation structure, the first angle and the second angle ⁇ 90 ° .
  • the value of the first included angle is 5-30 °
  • the value of the second included angle is 5-30 °
  • the lower limit of the value of the first included angle and the second included angle is selected from 7 °, 10 °, 13 °, or 15 °
  • the upper limit is selected from 28 °, 25 °, 23 °, 20 °, or 18 °.
  • the first included angle and the second included angle are substantially equal.
  • the outer surface of the heat preservation structure is a cylinder, and the top of the heat preservation structure does not have an opening; the inner surface of the bottom of the heat preservation structure is substantially cylindrical; from the bottom of the crucible to the direction of its opening, the inner surface of the side of the heat preservation structure is along It extends away from the center of the crucible; the top of the insulation structure thickens along the direction from the edge of the crucible to the center;
  • the inner surface of the side wall of the crucible is substantially cylindrical, and the outer wall of the crucible has substantially the same extension direction as the inner surface of the side portion of the heat-retaining structure.
  • the thermal field structure further includes a seed crystal unit, the seed crystal unit is disposed above the opening of the crucible, and the heat preservation structure does not have an opening structure.
  • the seed crystal unit includes a carbonized single crystal seed crystal.
  • a crystal growth apparatus characterized by comprising the thermal field structure described in any one of the above.
  • the crystal growth device is used to prepare a semi-insulating silicon carbide single crystal with a diameter of 4-12 inches and its substrate. Further, the crystal growth device is used to prepare a semi-insulating silicon carbide single crystal with a diameter greater than 8 inches and less than or equal to 12 inches and its substrate.
  • a method for preparing a silicon carbide single crystal is provided.
  • the method redesigns the crucible and the heat-insulating structure surrounding the crucible to form a uniform heat field structure in the radial direction, thereby improving silicon carbide
  • the radial uniformity of the single crystal makes it possible to prepare high-quality large-size, high-purity, semi-insulating silicon carbide single crystal substrates.
  • the preparation method of the large-size high-purity silicon carbide single crystal includes the following steps:
  • Impurity removal stage the crystal growth device is sealed and evacuated, filled with protective gas after impurity removal;
  • Crystal growth stage the heating unit of the crystal growth device is used to control the temperature of the crucible to perform crystal growth, that is, the high-purity silicon carbide single crystal is prepared.
  • the purity of the silicon carbide powder is not less than 99.9999%, wherein the concentration of the donor impurities in the shallow energy level in the silicon carbide powder is not greater than 1 ⁇ 10 16 cm -3 , and the acceptor impurities in the shallow energy level The concentration is greater than 1 ⁇ 10 16 cm ⁇ 3 .
  • the concentration of the shallow-level donor impurity is not more than 1 ⁇ 10 15 cm ⁇ 3
  • the concentration of the shallow-level acceptor impurity is not more than 1 ⁇ 10 15 cm ⁇ 3 .
  • the shallow-level donor impurities include nitrogen
  • the shallow-level acceptor impurities include boron and aluminum.
  • the crystal growth stage includes: raising the pressure in the crucible to 10-100 mbar at a rate of 30-50 mbar / h, while increasing the temperature in the crucible to 2100-2200 ° C at a rate of 10-20 ° C / h , Keep 50-100h.
  • the crystal growth stage includes: increasing the pressure in the crucible to 20-80 mbar at a rate of 35-45 mbar / h, while increasing the temperature in the crucible to 2100-2200 °C at a rate of 10-20 ° C / h, Keep 60-80h.
  • the impurity removal stage includes: evacuating the pressure inside the crucible to 10-5 Pa and maintaining it for 5-10 h, and then introducing the protective gas. Further, the pressure inside the crucible was evacuated to 10-5 Pa and maintained for 6-9h. Further, the included gases are argon and helium.
  • the crucible and the heat preservation structure make the crucible have an axial temperature gradient and / or a uniform radial temperature.
  • the crucible and the thermal insulation structure are such that the radial temperature gradient in the crucible is close to zero.
  • the crucible is a graphite crucible.
  • the side wall of the crucible is linearly thickened along the direction from the bottom of the crucible to the opening.
  • the heat preservation structure includes a heat preservation structure top, a heat preservation structure side portion and a heat preservation structure bottom portion, and the wall portion of the heat preservation structure side portion is linearly thickened along the direction of the crucible opening to the bottom.
  • the crucible and the thermal insulation structure generally share a first central axis
  • the first central axis has a first angle with the outer surface of the side wall of the crucible and / or, the first central axis has a second angle with the inner side surface of the thermal insulation structure, the first angle ⁇ 90 °, The second included angle is ⁇ 90 °.
  • the crucible and the thermal insulation structure share a first central axis
  • the first central axis is parallel to the inner surface of the side wall of the crucible and / or the outer surface of the side of the heat preservation structure;
  • the first central axis has a first angle with the outer surface of the side wall of the crucible, and the first central axis has a second angle with the inner surface of the side of the thermal insulation structure, the first angle ⁇ 90 °, the second angle Angle ⁇ 90 °.
  • the value of the first included angle is 5-30 °.
  • the lower limit of the range of the first included angle is selected from 7 °, 10 °, 13 ° or 15 °, and the upper limit is selected from 28 °, 25 °, 23 °, 20 ° or 18 °.
  • the value of the second included angle is 5-30 °.
  • the lower limit of the range of the second included angle is selected from 7 °, 10 °, 13 °, or 15 °
  • the upper limit is selected from 28 °, 25 °, 23 °, 20 °, or 18 °.
  • the first included angle and the second included angle are substantially equal.
  • the opening surface of the crucible has a first distance to the inner surface of the top of the thermal insulation structure above it, and the first distance increases along the direction from the center of the crucible to the edge of the crucible.
  • the range of the change value of the first distance is 5-50 mm.
  • the lower limit of the range of the change value of the first distance is selected from 10 mm, 15 mm, 20 mm, 25 mm, or 30 mm, and the upper limit is selected from 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, or 45 mm.
  • the outer surface of the heat preservation structure is a cylinder, and the top of the heat preservation structure does not have an opening;
  • the inner surface of the bottom of the heat preservation structure is generally cylindrical; along the bottom of the crucible to the direction of its opening, the inner surface of the side of the heat preservation structure Extending along the direction away from the central axis of the crucible; the top of the insulation structure is thickened from the edge of the crucible to the center;
  • the inner surface of the side wall of the crucible is substantially cylindrical, and the outer wall of the crucible has substantially the same extension direction as the inner surface of the side portion of the heat-retaining structure.
  • the seed crystal unit is disposed at the opening of the crucible, and the seed crystal unit includes a silicon carbide unit
  • the thermal insulation structure does not have an opening structure.
  • a large-size high-purity silicon carbide single crystal which is characterized by being prepared by the above method.
  • a method for a large-sized high-purity silicon carbide single crystal substrate which includes any one of the above-mentioned methods for preparing a large-sized high-purity silicon carbide single crystal, and step 4)
  • Substrate preparation stage cutting, grinding and polishing the prepared high-purity silicon carbide single crystal to prepare a high-purity semi-insulating silicon carbide silicon carbide single crystal substrate.
  • a large-size high-purity silicon carbide single crystal substrate is provided, which is characterized in that it is prepared by the above method.
  • the method is used to prepare a semi-insulating silicon carbide single crystal with a diameter of 4-12 inches and its substrate. Further, this method is used to prepare a semi-insulating silicon carbide single crystal with a diameter greater than 8 inches and less than or equal to 12 inches and its substrate.
  • the large size in the large-size high-purity silicon carbide single crystal and large-size silicon carbide single crystal substrate refers to a diameter of 4-12 inches.
  • the PVT method refers to the physical vapor transport method.
  • crystal growth is performed by the PVT method, and the thermal field of crystal growth is transmitted from the crucible wall to the interior of the crucible after being heated.
  • the resistivity of the high-purity semi-insulating silicon carbide single crystal substrate is determined by the concentration of electroactive impurities in the crystal, where the shallow donor element nitrogen plays a decisive role in the value and distribution of resistivity.
  • the nitrogen concentration gradually decreases from the center to the edge of the crystal, thereby forming a tendency that the resistivity increases from the center to the edge in the radial direction, resulting in resistance on the same substrate The rate is unevenly distributed.
  • the thermal field structure of the grown silicon carbide single crystal of the present application forms a uniform thermal field structure in the radial direction by redesigning the crucible and surrounding the heat preservation structure of the crucible, thereby improving the radial uniformity of the quality of the silicon carbide single crystal It can prepare high-quality large-size high-purity semi-insulating silicon carbide single crystal substrates.
  • the preparation method of the silicon carbide single crystal of the present application can produce high-quality large-size high-purity semi-insulating single crystal and single crystal substrate.
  • the preparation method of the present application uses a crucible with different wall thicknesses and a thermal insulation structure with different thicknesses to manufacture the shaft To the temperature gradient, at the same time change the graphite insulation structure on the upper side of the graphite crucible, so as to create a thermal field structure with a uniform radial temperature distribution, which can make the radial distribution of the thermal field inside the large-size crucible uniform.
  • the traditional method of manufacturing an axial temperature gradient through heat dissipation through the upper insulation hole is changed, and instead, a crucible with different wall thicknesses and an insulation structure with different thicknesses are used to create an axial temperature gradient.
  • the graphite insulation on the upper side of the crucible changes the insulation structure to create a thermal field structure with uniform radial temperature distribution. Since the nitrogen element grows into the crystal with the temperature gradient, this thermal field structure with uniform radial temperature distribution will guide the nitrogen element to be evenly distributed in the radial direction.
  • high purity semi-insulating silicon carbide single crystals and single crystal substrates with uniform radial resistivity and low stress are prepared.
  • FIG. 1 is a schematic diagram of a thermal field structure including a crucible according to an embodiment of the present application.
  • FIG. 2 is a resistivity distribution diagram of a high-purity silicon carbide single crystal substrate according to an embodiment of the present application.
  • first and second are for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features.
  • the features defined as “first” and “second” may explicitly or implicitly include one or more of the features.
  • the meaning of “plurality” is two or more, unless otherwise specifically limited.
  • the terms “installation”, “connected”, “connected”, “fixed” and other terms should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , Or integrated; it can be mechanical connection, electrical connection, or communication; it can be directly connected or indirectly connected through an intermediary, it can be the connection between two components or the interaction between two components .
  • installation can be a fixed connection or a detachable connection , Or integrated; it can be mechanical connection, electrical connection, or communication; it can be directly connected or indirectly connected through an intermediary, it can be the connection between two components or the interaction between two components .
  • the first feature "above” or “below” the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly intermediary contact.
  • the description referring to the terms “one embodiment”, “some embodiments”, “examples”, “specific examples”, or “some examples” means specific features described in conjunction with the embodiment or examples , Structure, material or characteristics are included in at least one embodiment or example of the present application.
  • the schematic expressions of the above terms are not necessarily directed to the same embodiment or example.
  • the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
  • an embodiment of the present application discloses a thermal field structure including a crucible for growing silicon carbide single crystals.
  • the thermal field structure includes a crucible 2, a heating unit, and a thermal insulation structure 6.
  • the crucible 2 is located inside the sealed thermal insulation structure 6, the heating unit heats the outer wall of the crucible 2 by induction, and the heating unit is disposed on the periphery of the thermal insulation structure 6.
  • a raw material 1 for growing crystals is placed in the crucible 2.
  • the embodiment of the present application discloses an apparatus for growing silicon carbide single crystals, which includes a crucible thermal field structure and a seed crystal unit 8.
  • the thermal field structure includes a crucible 2, a heating unit, and a thermal insulation structure 6.
  • the device includes a graphite crucible 2, a heating unit, a thermal insulation structure 6 and a seed crystal unit 8.
  • the graphite crucible 2 is located inside the closed thermal insulation structure 6, and the heating unit heats the outer wall of the graphite crucible 2 by induction, and the heating unit is provided on the periphery of the thermal insulation structure 6.
  • a raw material 1 for growing crystals is placed in the graphite crucible 2.
  • the inner wall of the graphite crucible 2 is substantially cylindrical, and the side wall of the graphite crucible 2 is linearly thickened along the bottom of the graphite crucible 2 to the opening direction.
  • the heating unit can simply heat the outer wall of the crucible 2.
  • the heating unit is composed of a power controller and the corresponding intermediate frequency induction coil 4; the induction coil 4 is located on the periphery of the side of the insulation structure 6 and surrounds the insulation structure 6 and is shared with the crucible 2 A central axis.
  • the intermediate frequency induction coil heats the crucible 2 by induction.
  • the crucible 2 may be a graphite crucible, but is not limited to a graphite crucible, and may be any material used for preparing silicon carbide single crystals.
  • the inner wall of the graphite crucible 2 is substantially cylindrical, and the side wall of the graphite crucible 2 is linearly thickened along the bottom of the graphite crucible 2 to the opening direction.
  • the thermal insulation structure 6 is made of a material with thermal insulation, such as graphite thermal insulation felt.
  • the thermal insulation structure 6 includes a thermal insulation side portion 66, a thermal insulation bottom 62, and a thermal insulation structure top 64.
  • the thermal field structure has a seed crystal unit 8 which is arranged inside the cover of the graphite crucible 2, and the heat preservation structure 6 does not have an opening structure.
  • the seed crystal unit 8 includes a carbonized single crystal seed crystal.
  • the crucible 2 and the thermal insulation structure 6 share a first central axis A, which is parallel to the inner surface of the side wall of the crucible 2 and the outer surface of the wall portion of the thermal insulation structure 6; the first central axis A is the outer surface of the side wall of the crucible 2 That is, the schematic line B in the figure has a first included angle, and the first central axis A and the inner surface of the wall portion of the thermal insulation structure 6, ie, the schematic line C in FIG. 1 has a second included angle, the first included angle and the second included angle ⁇ 90 °.
  • the outer wall of the graphite crucible 2 is a heat source.
  • the outer wall of the graphite crucible 2 has a trapezoidal shape
  • the inner side of the graphite crucible 2 has a straight cylindrical shape
  • the wall thickness of the graphite crucible 2 decreases from the seed crystal to the bottom of the graphite crucible 2.
  • the graphite insulation blanket 6 around the graphite crucible 2 is composed of the insulation blanket bottom 62, the insulation blanket top 64 and the insulation blanket side 66, wherein the insulation blanket bottom 62 is a regular cylinder; the thickness of the insulation blanket side 66 is along the outer diameter of the graphite crucible 2 Trapezoidal structure, that is, the thickness of the insulation felt side 66 near the upper part of the graphite crucible 2 is the smallest and the thickness gradually increases as it approaches the bottom of the graphite crucible 2;
  • the opening surface to the inner surface of the wall portion of the top of the insulation felt 64 above it has a first distance X, and the range of the variation value of the first distance X is 5-50 mm, and the top 64 of the insulation felt no longer retains the circular hole for temperature measurement.
  • the change value of the first distance X is 25 mm.
  • the thickness of the graphite crucible cylinder in the embodiment of the present application decreases linearly from top to bottom, wherein the inner wall of the graphite crucible is a vertical straight line, and the outer wall is a diagonal line. Due to the induction heating of the outer surface of the graphite crucible, the thick graphite wall above the graphite crucible generates heat and the heat is transferred to the interior chamber of the graphite crucible when the heat is transferred to the graphite crucible inner chamber. And the lower temperature zone of the upper part, thus forming an axial temperature gradient.
  • the angle formed by the straight line of the inner and outer sides of the graphite crucible wall should be limited to 5-30 °, that is, the first angle between the outer surface of the graphite crucible and the first centerline axis is 5-30 °, and this first angle can balance the temperature formed Gradient and heating efficiency of graphite crucible. Further, the first angle between the outer surface of the graphite crucible and the first centerline axis is 20 °.
  • the outer insulation structure of the graphite crucible in the embodiment of the present application is made of graphite felt.
  • the outer structure of the graphite felt is a cylindrical structure, the outer surface of the graphite felt side is a vertical straight line, and the inner surface of the graphite felt side is The outer wall of the graphite crucible is parallel.
  • the angle between the inner and outer surface sections of the graphite felt side is 5-30 °, that is, the second angle between the inner surface of the graphite felt side and the first centerline axis is 5-30 °.
  • the thinner area of the lower part of the graphite crucible is coated with a thicker graphite felt to reduce heat loss, thereby further forming a high-temperature area; the thinner area of the upper part of the graphite crucible is coated with a thinner graphite felt, and more heat is lost, thereby forming a low-temperature area .
  • an axial temperature gradient can be further formed in the graphite chamber of the graphite crucible.
  • the graphite felt on the upper side of the graphite crucible near the graphite crucible adopts an arc design and the center of the graphite crucible is no longer provided with openings.
  • an axial temperature gradient can be formed in the graphite crucible chamber, instead of dissipating heat through the central hole provided on the upper insulation blanket to form an axial temperature ladder design.
  • the arc design is used to make the center of the upper side of the graphite crucible closer to the upper graphite felt and the edge of the graphite crucible farther away from the upper thermal insulation graphite felt. Compensate, reduce or even eliminate radial temperature gradients.
  • the height difference of the arc-shaped surface of the upper insulation blanket should be maintained between 5-50mm, which can reasonably control the radial temperature gradient.
  • the thermal field structure is obtained after the graphite thermal insulation structure and the graphite crucible are prepared according to the above method.
  • a thermal field structure with a radial temperature gradient close to zero is formed.
  • the prepared thermal field structure is used for the growth of high-purity silicon carbide single crystal.
  • the preparation method of the high-purity silicon carbide single crystal includes the following steps:
  • the furnace pressure is increased to 10-100 mbar at a rate of 30-50 mbar / h, and the temperature in the furnace is increased to 2100-2200 °C at a rate of 10-20 °C / h, and maintained at this temperature for 50-100 h, Complete the growth process of silicon carbide single crystal;
  • the silicon carbide single crystal was prepared according to the above method.
  • the specific preparation parameters are different from the above method as shown in Table 1.
  • High purity silicon carbide single crystal 1 # -4 # was prepared.
  • the prepared silicon carbide single crystal 1 #, silicon carbide single crystal 2 #, silicon carbide single crystal 3 #, silicon carbide single crystal 4 #, silicon carbide single crystal 5 #, silicon carbide single crystal 6 #, silicon carbide single crystal D1 #, silicon carbide single crystal D2 # and silicon carbide single crystal D3 # were subjected to the same cutting, grinding and polishing methods respectively to obtain silicon carbide single crystal substrate 1 #, silicon carbide single crystal substrate 2 #, silicon carbide Single crystal substrate 3 #, silicon carbide single crystal substrate 4 #, silicon carbide single crystal substrate 5 #, silicon carbide single crystal substrate 6 #, silicon carbide single crystal substrate D1 #, silicon carbide single crystal substrate D2 # ⁇ SiC single crystal substrate D3 #; silicon carbide single crystal substrate 1 #, silicon carbide single crystal substrate 2 #, silicon carbide single crystal substrate 3 #, silicon carbide single crystal substrate 4 #, silicon carbide single Crystal substrate 5 #, silicon carbide single crystal substrate 6 #, silicon carbide single crystal substrate D1 #, silicon carbide single crystal substrate D2 #, and silicon carb
  • the difference in radial resistivity of semi-insulating silicon carbide single crystal substrate is more than one order of magnitude, and the resistivity of 4-8 inch semi-insulating silicon carbide single crystal substrate 1 # -6 # produced in the examples of this application can reach 1 ⁇ 10 10 ⁇ ⁇ cm or more, and the radial distribution of resistivity is controlled within an order of magnitude, and further, it can be controlled within 50%, thereby achieving uniform distribution of the resistivity of the silicon carbide single crystal substrate.
  • the resistance distribution of silicon carbide single crystal D1 #, silicon carbide single crystal D2 # and silicon carbide single crystal D3 # is poor, and the radial distribution of resistance is greater than two orders of magnitude.
  • the resistivity distribution of the silicon carbide single crystal substrate 1 # is shown in FIG. 2, and the resistivity of the silicon carbide single crystal substrate 1 # is evenly distributed.
  • 4-inch semi-insulating silicon carbide single crystal substrate the maximum value of resistivity is in the edge area, and the minimum value is in the center area.
  • the resistivity values are 4.24 ⁇ 10 11 ⁇ ⁇ cm and 4.84 ⁇ 10 11 ⁇ ⁇ cm, respectively. Less than 50%.
  • the radial temperature of the silicon carbide single crystal growth interface remains the same, the impurities and intrinsic point defects in the crystal growth process are evenly distributed in the radial direction, and thus the larger size semi-insulating high purity with uniformly distributed resistivity along the radial direction can be realized Silicon carbide single crystal substrate.
  • the curvature and warpage are within 10 ⁇ m.
  • the 4-inch silicon carbide single crystal substrate 1 # has a substrate bow value of 3.09 ⁇ m and a warp of 6.20 ⁇ m, and has excellent surface quality.
  • the 8-inch silicon carbide single crystal substrate D1 #, silicon carbide single crystal substrate D2 # and silicon carbide single crystal substrate D3 # have a curvature and warpage of 23.39 ⁇ m / 31.74 ⁇ m, 19.27 ⁇ m / 29.73 ⁇ m, 27.84 ⁇ m / 40.66 ⁇ m, much larger than 10 ⁇ m.
  • the resistivity of the 8-12 inch semi-insulating silicon carbide single crystal substrate 1 # -6 # prepared in the examples of the present application can reach more than 1 ⁇ 10 10 ⁇ ⁇ cm, and the radial distribution of the resistivity is controlled within an order of magnitude Furthermore, it can be controlled within 80%, so as to achieve uniform distribution of the resistivity of the silicon carbide single crystal substrate.
  • its curvature and warpage can be controlled within 10 ⁇ m.

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Abstract

本申请公开了一种大尺寸高纯碳化硅单晶、衬底及其制备方法和制备用装置，属于碳化硅单晶、衬底领域。本申请通过改进PVT法的热场分布，改变传统的通过上保温孔散热制造轴向温度梯度的方法，改为使用不同壁厚的坩埚及不同厚度的保温结构制造出轴向温度梯度，同时改变坩埚上侧的保温结构，从而制造出径向温度分布一致的热场结构；尤其可使得大尺寸坩埚内部热场径向分布均匀；由于电活性杂质元素随着温度梯度而生长进入晶体中，因此这种径向温度分布均匀的热场结构将引导电活性杂质元素沿径向均匀分布，进而制备得到径向电阻率一致、低应力的大尺寸高纯半绝缘碳化硅单晶、单晶衬底。

Description

大尺寸高纯碳化硅单晶、衬底及其制备方法和制备用装置 技术领域
本申请涉及一种大尺寸高纯碳化硅单晶、单晶衬底及其制备方法和制备用装置，属于碳化硅单晶及其衬底领域。
背景技术
半导体碳化硅单晶材料自上世纪90年代开始商业化以来，经过近30年的发展，已逐步成为功率电子器件和微波射频器件的优选基底材料。随着下游器件技术的不断发展和产业化程度的不断提升，碳化硅单晶衬底质量需求也日趋严苛。
目前最为成熟的碳化硅单晶制备技术为物理气相输运法(简称PVT法)，其基本原理是通过中频感应加热放置于线圈中心的石墨坩埚，石墨坩埚壁感应发热后将热量传输至内部的碳化硅粉料并致其升华。在石墨坩埚上侧的石墨保温毡中心设置贯通的圆孔，在通过圆孔进行测温的同时使热量通过圆孔散失，从而造成坩埚下部温度高、上部温度低的轴向温度梯度，驱动升华的气相从生长腔室内的粉料区传输至坩埚顶部的籽晶区结晶。通过该方法制备的碳化硅单晶已由2英寸发展至8英寸并不断在下游器件中得到应用。
然而，随着晶体尺寸的不断增加，坩埚的直径也不断增大。由于中频感应加热方式中以坩埚壁作为发热源，沿坩埚壁与坩埚中心的径向温度梯度也不断增大；此外，PVT法通过在坩埚上侧保温中心圆孔作为散热中心制造轴向温度梯度，这会进一步造成坩埚内部的热场沿径向的不均匀性，导致晶体沿径向存在较大的热应力以及杂质和缺陷分布不均等问题。前者存在的热应力容易导致晶体加工过程中发生开裂、衬底加工过程中弯曲度、翘曲度不合格等严重的质量问题，后者的杂质与缺陷分布 不均也将严重制约衬底沿径向的电阻率均匀性等问题。
发明内容
为了解决上述问题，本申请一方提供了一种生长碳化硅单晶的装置，该装置通过重新设计坩埚和包覆于石墨坩埚外围的保温结构，形成沿径向均匀的热场，从而提高碳化硅单晶的径向均匀性，使得制备高质量的大尺寸高纯半绝缘碳化硅单晶衬底成为可能。
该生长碳化硅单晶的装置，包括石墨坩埚、加热单元、籽晶单元和保温结构，其特征在于，该保温结构包括保温结构顶部、保温结构侧部和保温结构底部，该石墨坩埚的内壁为大致圆柱状，该石墨坩埚的侧壁沿着石墨坩埚底部至开口方向线性加厚。
可选地，该籽晶单元设置在石墨坩埚开口上方位置，该保温结构不具有开孔结构，该籽晶单元包括碳化单晶籽晶。
可选地，该石墨坩埚位于该保温结构的密闭腔体内。
可选地，该保温结构的侧部的壁部沿着石墨坩埚开口至底部方向线性加厚。
可选地，该石墨坩埚的开口截面至其上方的保温结构顶部内表面具有第一距离，该第一距离沿着石墨坩埚中心至石墨坩埚边缘的方向增大。
可选地，所述加热单元对石墨坩埚的加热方式为感应加热。优选地，所述加热单元包括中频线圈。
可选地，该石墨坩埚与该保温结构共第一中心轴线；
该第一中心轴线与该石墨坩埚的侧壁内表面和/或该保温结构的侧部外表面平行；
该第一中心轴线与该石墨坩埚的侧壁外表面具有第一夹角，该第一中心轴线与该保温结构的侧部内表面具有第二夹角，该第一夹角和第二夹角的值为5～30°。进一步地，该第一夹角和第二夹角的值的下限选自 7°、10°、13°或15°，上限选自28°、25°、23°、20°或18°。
可选地，该第一夹角和第二夹角的值为10～25°。
可选地，该第一夹角和第二夹角大致相等。
可选地，该石墨坩埚的开口截面至其上方的保温结构顶部内表面具有第一距离，该第一距离沿着石墨坩埚中心至石墨坩埚边缘增大。作为一种实施方式，所述保温结构顶部为穹顶状。
可选地，该第一距离的变化值的值为5‐50mm。可选地，该第一距离的变化值的范围的下限选自10mm、15mm、20mm、25mm或30mmm，上限选自15mm、20mm、25mm、30mmm、35mm、40mm或45mm。
可选地，该第一距离的变化值的范围为10‐45mm。
可选地，该保温结构的外表面为圆柱体，该保温结构顶部不具有开口；该保温结构底部的内表面大致为圆柱状；沿着该石墨坩埚底部至其开口方向，该保温结构侧部内表面沿着远离该石墨坩埚中心轴线的方向延伸；该保温结构顶部沿着石墨坩埚边缘至中心的方向增厚。
可选地，该石墨坩埚的侧壁内表面为大致圆柱状，该石墨坩埚的外壁具有与该保温结构侧部内表面大致相同的延伸方向。
根据本申请的另一方面，提供了一种晶体生长装置，其特征在于，包括上述任一项所述的装置。
优选地，该晶体生长装置用于制备直径为4‐12英寸的半绝缘碳化硅单晶及其衬底。进一步地，该晶体生长装置用于制备直径为大于8英寸且小于等于12英寸的半绝缘碳化硅单晶及其衬底。
根据本申请的又一方面，本申请提供了一种生长碳化硅单晶的热场结构，该热场结构通过重新设计坩埚和包覆于坩埚外围的保温结构，形成沿径向均匀的热场结构，从而提高碳化硅单晶的径向均匀性，使得制备高质量的大尺寸高纯半绝缘碳化硅单晶衬底成为可能。
该生长碳化硅单晶的热场结构，包括坩埚、加热单元和保温结构，其特征在于，该保温结构包括保温结构顶部、保温结构侧部和保温结构底部，该坩埚位于该保温结构的密封腔体内；
该坩埚的侧壁开口区域的壁厚大于底部区域的壁厚。
可选地，该坩埚与保温结构使得坩埚内具有轴向温度梯度，和/或径向温度梯度接近零。
优选地，该坩埚为石墨坩埚。
可选地，该坩埚的侧壁沿着坩埚底部至开口方向线性加厚。
优选地，该保温结构的侧部的壁部沿着坩埚开口至底部方向线性加厚。
可选地，该坩埚的开口截面至其上方的保温结构顶部内表面具有第一距离，该第一距离从该坩埚中心至坩埚边缘的方向增大。
优选地，该第一距离的变化值的值为5‐50mm。可选地，该第一距离的变化值的范围的下限选自10mm、15mm、20mm、25mm或30mmm，上限选自15mm、20mm、25mm、30mmm、35mm、40mm或45mm。
可选地，该坩埚与该保温结构大致共第一中心轴线；
该第一中心轴线与该坩埚的侧壁内表面和/或该保温结构侧部外表面大致平行；
该第一中心轴线与该坩埚的侧壁外表面具有第一夹角，该第一中心轴线与该保温结构侧部内表面具有第二夹角，该第一夹角和第二夹角＜90°。
进一步地，该坩埚与该保温结构共第一中心轴线；
该第一中心轴线与该坩埚的侧壁内表面和/或该保温结构侧部外表面平行；
该第一中心轴线与该坩埚的侧壁外表面具有第一夹角，该第一中心 轴线与该保温结构侧部内表面具有第二夹角，该第一夹角和第二夹角＜90°。
可选地，该第一夹角的值为5～30°，该第二夹角的值为5～30°。进一步地，该第一夹角和第二夹角的值的下限选自7°、10°、13°或15°，上限选自28°、25°、23°、20°或18°。
可选地，该第一夹角和第二夹角大致相等。
可选地，该保温结构的外表面为圆柱体，该保温结构顶部不具有开口；该保温结构底部的内表面大致为圆柱状；从该坩埚底部至其开口方向，该保温结构侧部内表面沿着远离该坩埚中心的方向延伸；该保温结构顶部沿着坩埚边缘至中心的方向增厚；
该坩埚的侧壁内表面为大致圆柱状，该坩埚的外壁具有与该保温结构侧部内表面大致相同的延伸方向。
可选地，该热场结构中进一步包括籽晶单元，该籽晶单元设置在该坩埚开口上方，该保温结构不具有开孔结构。该籽晶单元包括碳化单晶籽晶。
根据本申请的又一方面，提供了一种碳化硅单晶的制备方法，其特征在于，使用上述任一项所述的热场结构进行制备。
根据本申请的另一方面，提供了一种晶体生长装置，其特征在于，包括上述任一项所述的热场结构。
优选地，该晶体生长装置用于制备直径为4‐12英寸的半绝缘碳化硅单晶及其衬底。进一步地，该晶体生长装置用于制备直径为大于8英寸且小于等于12英寸的半绝缘碳化硅单晶及其衬底。
根据本申请的再一方面，提供了一种碳化硅单晶的制备方法，该方法通过重新设计坩埚和包覆于坩埚外围的保温结构，形成沿径向均匀的热场结构，从而提高碳化硅单晶的径向均匀性，使得制备高质量的大尺 寸高纯半绝缘碳化硅单晶衬底成为可能。
该大尺寸高纯碳化硅单晶的制备方法，包括下述步骤：
1)组装阶段：将装填碳化硅粉料的坩埚安装籽晶单元，坩埚置于密闭保温结构的腔内，放入晶体生长装置内；
2)除杂阶段：将生长晶体装置密封并抽真空、除杂后充入保护气体；
3)长晶阶段：利用生长晶体装置的加热单元控制坩埚温度，进行长晶，即制得所述的高纯碳化硅单晶。
可选地，所述碳化硅粉料纯度不低于99.9999％，其中，所述碳化硅粉料中的浅能级施主杂质浓度不大于1×10 16cm ‐3，浅能级受主杂质的浓度大于不大于1×10 16cm ‐3。
进一步地，所述浅能级施主杂质浓度在不大于1×10 15cm ‐3，所述浅能级受主杂质的浓度不大于1×10 15cm ‐3。
可选地，所述浅能级施主杂质包括氮元素，所述浅能级受主杂质包括硼和铝。
可选地，所述长晶阶段包括：以30‐50mbar/h的速率将坩埚内压力提升至10‐100mbar，同时以10‐20℃/h的速率将坩埚内的温度提升至2100‐2200℃，保持50‐100h。
进一步地，所述长晶阶段包括：以35‐45mbar/h的速率将坩埚内压力提升至20‐80mbar，同时以10‐20℃/h的速率将坩埚内的温度提升至2100‐2200℃，保持60‐80h。
可选地，所述除杂阶段包括：将坩埚内部的压力抽真空至10 ‐5Pa并保持5‐10h，之后通入保护气体。进一步地，将坩埚内部的压力抽真空至10 ‐5Pa并保持6‐9h。进一步地，所述包括气体为氩气和氦气。
可选地，该坩埚与该保温结构使得坩埚内具有轴向温度梯度，和/或径向温度均匀。优选地，该坩埚与该保温结构使得坩埚内径向温度梯度 接近零。
优选地，所述坩埚为石墨坩埚。
可选地，该坩埚的侧壁沿着坩埚底部至开口方向线性加厚。
优选地，所述保温结构包括保温结构顶部、保温结构侧部和保温结构底部，该保温结构侧部的壁部沿着坩埚开口至底部方向线性加厚。
可选地，该坩埚与该保温结构大致共第一中心轴线；
该第一中心轴线与该坩埚的侧壁内表面和/或该保温结构的侧部外表面大致平行；
该第一中心轴线与该坩埚的侧壁外表面具有第一夹角和/或，该第一中心轴线与该保温结构的侧部内表面具有第二夹角，该第一夹角＜90°，该第二夹角＜90°。
进一步地，该坩埚与该保温结构共第一中心轴线；
该第一中心轴线与该坩埚的侧壁内表面和/或该保温结构的侧部外表面平行；
该第一中心轴线与该坩埚的侧壁外表面具有第一夹角，该第一中心轴线与该保温结构的侧部内表面具有第二夹角，该第一夹角＜90°，第二夹角＜90°。
可选地，该第一夹角的值为5～30°。进一步地，该第一夹角的范围的下限选自7°、10°、13°或15°，上限选自28°、25°、23°、20°或18°。
可选地，第二夹角的值为5～30°。进一步地，该第二夹角的范围的下限选自7°、10°、13°或15°，上限选自28°、25°、23°、20°或18°。
优选地，该第一夹角和第二夹角大致相等。
可选地，该坩埚的开口面至其上方的保温结构顶部内表面具有第一 距离，该第一距离沿着该坩埚中心至坩埚边缘的方向增大。
可选地，该第一距离的变化值的范围为5‐50mm。可选地，该第一距离的变化值的范围的下限选自10mm、15mm、20mm、25mm或30mm，上限选自15mm、20mm、25mm、30mm、35mm、40mm或45mm。
可选地，该保温结构的外表面为圆柱体，该保温结构顶部不具有开口；该保温结构底部的内表面大致为圆柱状；沿着该坩埚底部至其开口方向，该保温结构侧部内表面沿着远离该坩埚中心轴线的方向延伸；该保温结构顶部沿着坩埚边缘至中心的方向增厚；
该坩埚的侧壁内表面为大致圆柱状，该坩埚的外壁具有与该保温结构侧部内表面大致相同的延伸方向。
可选地，该籽晶单元设置在坩埚开口处，该籽晶单元包括碳化硅单
晶籽晶。可选地，该保温结构不具有开孔结构。
根据本申请的另一方面，提供了一种大尺寸高纯碳化硅单晶，其特征在于，由上述的方法制备得到。
根据本申请的又一方面，提供了一种大尺寸高纯碳化硅单晶衬底的方法，该方法包括上述任一所述的大尺寸高纯碳化硅单晶的制备方法，和步骤4)衬底制备阶段：将制得的高纯碳化硅单晶进行切割、研磨和抛光，制得高纯半绝缘碳化硅碳化硅单晶衬底。
根据本申请的再一方面，提供了一种大尺寸高纯碳化硅单晶衬底，其特征在于，由上述方法制备得到。
优选地，该方法用于制备直径为4‐12英寸的半绝缘碳化硅单晶及其衬底。进一步地，该方法用于制备直径为大于8英寸且小于等于12英寸的半绝缘碳化硅单晶及其衬底。
本申请中，所述大尺寸高纯碳化硅单晶、大尺寸碳化硅单晶衬底中所述的大尺寸是指直径为4‐12英寸。
本申请中，PVT法，是指物理气相输运法。
现有技术通过PVT法进行晶体生长，晶体生长热场由坩埚壁发热后传输至坩埚内部。在距离坩埚外壁越远的位置则温度越低，从而导致坩埚内部呈现较大的径向温度梯度。这种情况随着坩埚和晶体尺寸的增加而愈加严重。高纯半绝缘碳化硅单晶衬底的电阻率由晶体中的电活性杂质浓度决定，其中，浅施主元素氮在电阻率的数值及分布上起决定性的作用。由于PVT法制备碳化硅单晶时的热场分布特点，自晶体中心至边缘氮浓度逐渐降低，从而在容易径向上形成电阻率自中心向边缘升高的趋势，造成同一片衬底上的电阻率分布不均。
本申请的有益效果包括但不限于：
本申请的生长碳化硅单晶的热场结构通过重新设计坩埚和包覆于坩埚外围保温结构，形成沿径向均匀的热场结构，从而提高碳化硅单晶的质量的径向均匀性，从而可制备高质量的大尺寸高纯半绝缘碳化硅单晶衬底。
本申请的碳化硅单晶的制备方法可制得高质量的大尺寸高纯半绝缘单晶及单晶衬底，本申请的制备方法使用不同壁厚的坩埚及不同厚度的保温结构制造出轴向温度梯度，同时改变石墨坩埚上侧的石墨保温结构，从而制造出径向温度分布一致的热场结构，可使得大尺寸坩埚内部热场径向分布均匀。
本申请通过改进PVT法的热场分布，改变传统的通过上保温孔散热制造轴向温度梯度的方法，改为使用不同壁厚的坩埚及不同厚度的保温结构制造出轴向温度梯度，同时在坩埚上侧的石墨保温处改变保温结构，从而制造出径向温度分布一致的热场结构。由于氮元素随着温度梯度而 生长进入晶体中，因此这种径向温度分布均匀的热场结构将引导氮元素沿径向均匀分布。使用此方法制备得到径向电阻率一致、低应力的高纯半绝缘碳化硅单晶及单晶衬底。
附图说明
此处所说明的附图用来提供对本申请的进一步理解，构成本申请的一部分，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定。在附图中：
图1为本申请实施例涉及的包括坩埚的热场结构示意图。
图2为本申请实施例涉及的高纯碳化硅单晶衬底的电阻率分布图。
具体实施方式
为了更清楚的阐释本申请的整体构思，下面结合说明书附图以示例的方式进行详细说明。
了能够更清楚地理解本申请的上述目的、特征和优点，下面结合附图和具体实施方式对本申请进行进一步的详细描述。需要说明的是，在不冲突的情况下，本申请的实施例及实施例中的特征可以相互组合。
在下面的描述中阐述了很多具体细节以便于充分理解本申请，但是，本申请还可以采用其他不同于在此描述的其他方式来实施，因此，本申请的保护范围并不受下面公开的具体实施例的限制。
另外，在本申请的描述中，需要理解的是，术语“上”、“下”、“前”、“后”、“左”、“右”、“内”、“外”、“轴向”、“径向”、“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示 或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多该特征。在本申请的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。
在本申请中，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”、“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或成一体；可以是机械连接，也可以是电连接，还可以是通信；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
在本申请中，除非另有明确的规定和限定，第一特征在第二特征“上”或“下”可以是第一和第二特征直接接触，或第一和第二特征通过中间媒介间接接触。在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本申请的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不是必须针对的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任一个或多个实施例或示例中以合适的方式结合。
参考图1，本申请的实施例公开了一种生长碳化硅单晶的包括坩埚的热场结构，该热场结构包括坩埚2、加热单元和保温结构6。坩埚2位于密闭的保温结构6内部，加热单元通过感应的方式加热坩埚2的外壁，加热单元设置在保温结构6的外围。坩埚2内放置生长晶体的原料1。
本申请的实施例公开了一种生长碳化硅单晶的装置，该装置包括坩埚的热场结构和籽晶单元8，该热场结构包括坩埚2、加热单元和保温结构6。该装置包括石墨坩埚2、加热单元、保温结构6和籽晶单元8。石 墨坩埚2位于密闭的保温结构6内部，加热单元通过感应的方式加热石墨坩埚2的外壁，加热单元设置在保温结构6的外围。石墨坩埚2内放置生长晶体的原料1。石墨坩埚2的内壁为大致圆柱状，该石墨坩埚2的侧壁沿着石墨坩埚2底部至开口方向线性加厚。
加热单元可实现对坩埚2的外壁加热即可，加热单元由电源控制器和相应的中频感应线圈4构成；感应线圈4位于保温结构6侧部的外围，环绕保温结构6且与坩埚2共第一中心轴线。中频感应线圈，通过感应的方式对坩埚2加热。
坩埚2可为石墨坩埚，但不限于石墨坩埚，可以为用于制备碳化硅单晶的任意材料。石墨坩埚2的内壁为大致圆柱状，该石墨坩埚2的侧壁沿着石墨坩埚2底部至开口方向线性加厚。
保温结构6由具有保温隔热的材料制成，如使用石墨保温毡制成，保温结构6包括保温侧部66、保温底部62和保温结构顶部64。
进一步地，该热场结构中具有籽晶单元8，该籽晶单元8设置在石墨坩埚2盖体内侧，该保温结构6不具有开孔结构。该籽晶单元8包括碳化单晶籽晶。
坩埚2与保温结构6共第一中心轴线A，第一中心轴线A与坩埚2的侧壁内表面和保温结构6的壁部外表面平行；第一中心轴线A与坩埚2的侧壁外表面即图中的示意线B具有第一夹角和，第一中心轴线A与保温结构6的壁部内表面即图1中的示意线C具有第二夹角，第一夹角和第二夹角＜90°。
作为本申请的一种实施方式，根据中频加热石墨坩埚2的集肤效应，中频加热石墨坩埚2时，石墨坩埚2外壁为发热源。本实施例中的石墨坩埚2外壁为梯形状，石墨坩埚2内侧呈直筒状，石墨坩埚2壁厚自籽晶处至石墨坩埚2底部厚度减小。石墨坩埚2外围的石墨保温毡6由保 温毡底部62、保温毡顶部64和保温毡侧部66构成，其中保温毡底部62为规则圆柱状；保温毡侧部66厚度沿着石墨坩埚2外径呈梯形结构，即靠近石墨坩埚2上部的保温毡侧部66厚度最小且厚度随着靠近石墨坩埚2底部而逐渐增大；保温毡顶部64靠近石墨坩埚2一侧呈穹顶状，石墨坩埚2的开口面至其上方的保温毡顶部64壁部内表面具有第一距离X，该第一距离X的变化值的范围为5‐50mm，且保温毡顶部64不再保留测温圆孔，进一步地，该第一距离X的变化值为25mm。
本申请的实施方式中的石墨坩埚圆筒自上至下厚度线性减小，其中石墨坩埚内壁呈垂直直线，外壁呈斜线状。由于石墨坩埚外壁表层感应加热，石墨坩埚上部较厚的石墨壁发热后热量向石墨坩埚内部腔室传递时石墨坩埚效率小于石墨坩埚下部较薄的区域，继而可以在石墨坩埚腔室内形成下部较高的温区和上部较低的温区，从而形成轴向温度梯度。石墨坩埚壁内外侧剖面直线所形成的角度应限制在5‐30°，即石墨坩埚外表面与第一中线轴线的第一夹角为5‐30°，该第一夹角可平衡所形成温度梯度与石墨坩埚的发热效率。进一步地，石墨坩埚外表面与第一中线轴线的第一夹角为20°。
进一步地，本申请的实施方式中的石墨坩埚外侧保温结构由石墨毡制成，该保温结构即石墨毡的外部呈圆柱状结构，石墨毡侧部外表面呈垂直直线，石墨毡侧部内表面与石墨坩埚外壁平行。石墨毡侧部内外表剖面夹角呈5‐30°，即石墨毡侧部内表面与第一中线轴线的第二夹角为5‐30°。石墨坩埚下部较薄的区域外部包覆较厚部分的石墨毡减少热量散失，从而进一步形成高温区域；石墨坩埚上部较薄的区域包覆较薄的石墨毡，热量散失较多，从而形成低温区域。由此，可以在石墨坩埚石墨腔室内进一步形成轴向温度梯度。
更进一步地，本申请的实施方式中石墨坩埚上侧石墨毡靠近石墨坩 埚一侧采用弧形设计且石墨坩埚中心不再进行开孔设置。根据上述石墨坩埚和保温毡的设计，可以在石墨坩埚腔室内形成轴向温度梯度，替代上侧保温毡设置的中心孔散热形成轴向温梯的设计。然而，由于石墨坩埚壁发热的原因，径向上依然存在靠近石墨坩埚壁的区域温度较高、远离石墨坩埚壁的腔室中心温度较低的温梯，造成径向存在温度梯度。采用弧形设计，使石墨坩埚上侧中心距离上侧石墨毡较近、石墨坩埚边缘距离上侧保温石墨毡较远，因此石墨坩埚中心散热少、边缘散热多，从而与石墨坩埚壁发热情况相互补偿，减小甚至消除径向温度梯度。上侧保温毡弧形面高度差应保持在5‐50mm之间，可以合理的控制径向温度梯度。
按照上述方法制备完成石墨保温毡保温结构和石墨坩埚后即得到热场结构在制备碳化硅单晶是会形成径向温度梯度接近于零的热场结构。将制备的热场结构用于高纯碳化硅单晶的生长，该高纯碳化硅单晶的制备方法包括下述步骤：
①、将一定数量的碳化硅粉料置于石墨坩埚内，碳化硅粉料纯度应在99.9999％以上，其中所含的浅能级施主杂质如氮的浓度在1×10 16cm ‐3以下，浅能级受主杂质如硼、铝等浓度之和应在1×10 16cm ‐3以下；
②、将用于生长碳化硅单晶的籽晶置于石墨坩埚内部的碳化硅粉料上部后，将石墨坩埚密封；密封后的石墨坩埚放置于石墨保温毡保温结构内部后，整体移至单晶生长设备内后密封炉膛；
③、将炉膛内的压力抽真空至10 ‐5Pa并保持5‐10h，以去除炉腔内的残余杂质后，逐步向炉腔内通入保护气氛，例如氩气或氦气；
④、以30‐50mbar/h的速率将炉膛压力提升至10‐100mbar，同时以10‐20℃/h的速率将炉膛内的温度提升至2100‐2200℃，在此温度下保持50‐100h，完成碳化硅单晶的生长过程；
⑤、单晶生长过程结束后，停止加热炉膛，使炉膛温度自然降低至室温后，打开炉膛取出石墨坩埚，即可得所述的高处碳化硅单晶。
按照上述的方法制备碳化硅单晶，具体制备参数与上述方法不同之处如表1所示，制得高纯碳化硅单晶1#‐4#。
表1
Figure PCTCN2018123708-appb-000001
Figure PCTCN2018123708-appb-000002
将制得的碳化硅单晶1#、碳化硅单晶2#、碳化硅单晶3#、碳化硅单 晶4#、碳化硅单晶5#、碳化硅单晶6#、碳化硅单晶D1#、碳化硅单晶D2#和碳化硅单晶D3#分别进行同样的切割、研磨和抛光方法，分别制得碳化硅单晶衬底1#、碳化硅单晶衬底2#、碳化硅单晶衬底3#、碳化硅单晶衬底4#、碳化硅单晶衬底5#、碳化硅单晶衬底6#、碳化硅单晶衬底D1#、碳化硅单晶衬底D2#和碳化硅单晶衬底D3#；碳化硅单晶衬底1#、碳化硅单晶衬底2#、碳化硅单晶衬底3#、碳化硅单晶衬底4#、碳化硅单晶衬底5#、碳化硅单晶衬底6#、碳化硅单晶衬底D1#、碳化硅单晶衬底D2#和碳化硅单晶衬底D3#分别具有4‐12英寸的规格。
分别测试制得的碳化硅单晶衬底1#、碳化硅单晶衬底2#、碳化硅单晶衬底3#、碳化硅单晶衬底4#、碳化硅单晶衬底5#、碳化硅单晶衬底6#、碳化硅单晶衬底D1#、碳化硅单晶衬底D2#和碳化硅单晶衬底D3#的电阻率分布。通常半绝缘碳化硅单晶衬底的径向电阻率差异在一个数量级以上,本申请的实施例制得的4‐8英寸半绝缘碳化硅单晶衬底1#‐6#电阻率可以达到1×10 10Ω·cm以上，且电阻率径向分布控制在一个数量级以内，更进一步的，可以控制在50％以内，从而实现碳化硅单晶衬底的电阻率均匀分布。而碳化硅单晶D1#、碳化硅单晶D2#和碳化硅单晶D3#的电阻率分布均匀性差，电阻率径向分布大于两个数量级。以4英寸的碳化硅单晶衬底1#为例说明测试的结构，碳化硅单晶衬底1#的电阻率分布图2所示，碳化硅单晶衬底1#的电阻率均匀分布。4英寸半绝缘碳化硅单晶衬底，电阻率最大值位于边缘区域，最小值位于中心区域，电阻率值分别是4.24×10 11Ω·cm和4.84×10 11Ω·cm，电阻率值差异低于50％。
由于碳化硅单晶生长界面的径向温度保持一致，因此晶体生长过程中的杂质和本征点缺陷在径向分布均匀，进而可以实现电阻率沿径向均匀分布的更大尺寸半绝缘高纯碳化硅单晶衬底。
分别测试制得的碳化硅单晶衬底1#、碳化硅单晶衬底2#、碳化硅单 晶衬底3#、碳化硅单晶衬底4#、碳化硅单晶衬底5#、碳化硅单晶衬底6#、碳化硅单晶衬底D1#、碳化硅单晶衬底D2#和碳化硅单晶衬底D3#的弯曲度和翘曲度。对于4‐8英寸的制得的碳化硅单晶衬底1#‐6#的弯曲度和翘曲度在10μm以内。例如4英寸碳化硅单晶衬底1#的衬底弯曲度(bow)值为3.09μm，翘曲度(warp)为6.20μm，具有优异的面型质量。
由于该坩埚能够提供减小径向的温度梯度，从而使得碳化硅晶体的内应力也同时减小，因此制备得到的碳化硅单晶衬底具有较小的应力，有利于降低其弯曲度和翘曲度，从而得到更高品质的碳化硅单晶衬底。8英寸的碳化硅单晶衬底D1#、碳化硅单晶衬底D2#和碳化硅单晶衬底D3#的弯曲度和翘曲度分别为23.39μm/31.74μm、19.27μm/29.73μm、27.84μm/40.66μm，远大于10μm。
本申请的实施例制得的8‐12英寸半绝缘碳化硅单晶衬底1#‐6#的电阻率可以达到1×10 10Ω·cm以上，且电阻率径向分布控制在一个数量级以内，更进一步的，可以控制在80％以内，从而实现碳化硅单晶衬底的电阻率均匀分布。对于8‐12英寸碳化硅单晶衬底，其弯曲度和翘曲度可以控制在10μm以内。
以上所述，仅为本申请的实施例而已，本申请的保护范围并不受这些具体实施例的限制，而是由本申请的权利要求书来确定。对于本领域技术人员来说，本申请可以有各种更改和变化。凡在本申请的技术思想和原理之内所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (35)

  1. 一种生长碳化硅单晶的装置，包括石墨坩埚、加热单元、籽晶单元和保温结构，其特征在于，该保温结构包括保温结构顶部、保温结构侧部和保温结构底部，该石墨坩埚的内壁为大致圆柱状，该石墨坩埚的侧壁沿着石墨坩埚底部至开口方向线性加厚。
  2. 根据权利要求1所述的生长碳化硅单晶的装置，其特征在于，该石墨坩埚位于该保温结构的密闭腔体内。
  3. 根据权利要求1所述的生长碳化硅单晶的装置，其特征在于，该保温结构侧部的壁部沿着石墨坩埚开口至底部方向线性加厚。
  4. 根据权利要求1所述的生长碳化硅单晶的装置，其特征在于，该石墨坩埚的开口截面至其上方的保温结构顶部内表面具有第一距离，该第一距离沿着石墨坩埚中心至石墨坩埚边缘的方向增大。
  5. 根据权利要求1所述的生长碳化硅单晶的装置，其特征在于，所述加热单元对石墨坩埚为感应加热方式。
  6. 根据权利要求1所述的生长碳化硅单晶的装置，其特征在于，该石墨坩埚与该保温结构共第一中心轴线；
    该第一中心轴线与该石墨坩埚的侧壁内表面和/或该保温结构侧部外表面平行；
    该第一中心轴线与该石墨坩埚的侧壁外表面具有第一夹角，该第一中心轴线与该保温结构的侧部内表面具有第二夹角，该第一夹角和第二夹角的值为5～30°。
  7. 根据权利要求4所述的生长碳化硅单晶的装置，其特征在于，该第一距离的变化值为5‐50mm。
  8. 根据权利要求1所述的生长碳化硅单晶的装置，其特征在于，该 保温结构的外表面为圆柱体，该保温结构顶部不具有开口；该保温结构底部的内表面大致为圆柱状；沿着该石墨坩埚底部至其开口方向，该保温结构侧部内表面沿着远离该石墨坩埚中心轴线的方向延伸；该保温结构顶部沿着石墨坩埚边缘至中心的方向增厚。
  9. 根据权利要求1所述的生长碳化硅单晶的装置，其特征在于，该石墨坩埚的侧壁内表面为大致圆柱状，该石墨坩埚的外壁具有与该保温结构侧部内表面大致相同的延伸方向。
  10. 一种晶体生长装置，其特征在于，包括权利要求1‐9中任一项所述的生长碳化硅单晶的装置。
  11. 一种生长碳化硅单晶的热场结构，包括坩埚、加热单元和保温结构，其特征在于，该保温结构包括保温结构顶部、保温结构侧部和保温结构底部，该坩埚位于该保温结构的密封腔体内；
    该坩埚的侧壁开口区域壁厚大于底部区域的壁厚。
  12. 根据权利要求11所述的热场结构，其特征在于，该坩埚为石墨坩埚。
  13. 根据权利要求11所述的热场结构，其特征在于，该坩埚的侧壁沿着坩埚底部至开口方向线性加厚。
  14. 根据权利要求13所述的热场结构，其特征在于，该保温结构侧部的壁部沿着坩埚开口至底部方向线性加厚。
  15. 根据权利要求11所述的热场结构，其特征在于，该坩埚的开口截面至其上方的保温结构顶部内表面具有第一距离，该第一距离沿着坩埚中心至坩埚边缘增大。
  16. 根据权利要求15所述的热场结构，其特征在于，该第一距离的变化值为5‐50mm。
  17. 根据权利要求11所述的热场结构，其特征在于，该坩埚与该保 温结构大致共第一中心轴线；
    该第一中心轴线与该坩埚的侧壁内表面和/或该保温结构侧部外表面大致平行；
    该第一中心轴线与该坩埚的侧壁外表面具有第一夹角和/或，该第一中心轴线与该保温结构侧部内表面具有第二夹角，该第一夹角和第二夹角＜90°。
  18. 根据权利要求11所述的热场结构，其特征在于，该坩埚与该保温结构共第一中心轴线；
    该第一中心轴线与该坩埚的侧壁内表面和/或该保温结构侧部外表面平行；
    该第一中心轴线与该坩埚的侧壁外表面具有第一夹角，该第一中心轴线与该保温结构侧部内表面具有第二夹角，该第一夹角和第二夹角＜90°。
  19. 根据权利要求17或18所述的热场结构，其特征在于，该第一夹角的值为5～30°，该第二夹角的值为5～30°。
  20. 根据权利要求19所述的热场结构，其特征在于，该第一夹角和第二夹角大致相等。
  21. 根据权利要求11所述的热场结构，其特征在于，该保温结构的外表面为圆柱体，该保温结构顶部不具有开口；该保温结构底部的内表面大致为圆柱状；沿着该坩埚底部至其开口方向，该保温结构侧部内表面沿着远离该坩埚中心轴线的方向延伸；该保温结构顶部沿着坩埚边缘至中心的方向增厚；
    该坩埚的侧壁内表面为大致圆柱状，该坩埚的外壁具有与该保温结构侧部内表面大致相同的延伸方向。
  22. 一种晶体生长装置，其特征在于，包括权利要求11‐21中任一项 所述的热场结构。
  23. 根据权利要求22所述的晶体生长装置，其特征在于，所述晶体生长装置用于制备直径为4‐12英寸的半绝缘碳化硅单晶。
  24. 一种大尺寸高纯碳化硅单晶的制备方法，其特征在于，使用权利要求21‐21中任一项所述热场结构或，权要求22或23所述的生长装置进行制备。
  25. 一种大尺寸高纯碳化硅单晶的制备方法，其特征在于，包括下述步骤：
    1)组装阶段：将装填碳化硅粉料的坩埚安装籽晶单元后，坩埚置于密闭保温结构的腔内，移至晶体生长装置内；
    2)除杂阶段：将生长晶体装置密封并抽真空、除杂后充入保护气体；
    3)长晶阶段：利用生长晶体装置的加热单元控制坩埚温度，进行长晶，即制得高纯碳化硅单晶。
  26. 根据权利要求25所述的大尺寸高纯碳化硅单晶的制备方法，其特征在于，所述碳化硅粉料纯度不低于99.9999％，
    其中，所述碳化硅粉料中的浅能级施主杂质浓度不大于1×10 16cm ‐3，浅能级受主杂质的浓度不大于1×10 16cm ‐3。
  27. 根据权利要求25所述的大尺寸高纯碳化硅单晶的制备方法，其特征在于，所述长晶阶段包括：以30‐50mbar/h的速率将生长晶体装置内压力提升至10‐100mbar，同时以10‐20℃/h的速率将生长晶体装置内的温度提升至2100‐2200℃，保持50‐100h。
  28. 根据权利要求25所述的大尺寸高纯碳化硅单晶的制备方法，其特征在于，该坩埚与该保温结构使得坩埚内具有轴向温度梯度，和/或径向温度均匀；优选地，所述坩埚为石墨坩埚。
  29. 根据权利要求25所述的大尺寸高纯碳化硅单晶的制备方法，其 特征在于，所述坩埚的侧壁沿着坩埚底部至开口方向线性加厚；
    优选地，所述保温结构包括保温结构顶部、保温结构侧部和保温结构底部，该保温结构侧部的壁部沿着坩埚开口至底部方向线性加厚。
  30. 根据权利要求29所述的大尺寸高纯碳化硅单晶的制备方法，其特征在于，该坩埚与该保温结构大致共第一中心轴线；
    该第一中心轴线与该坩埚的侧壁内表面和/或该保温结构侧部外表面大致平行；
    该第一中心轴线与该坩埚侧壁外表面具有第一夹角和/或，该第一中心轴线与该保温结构的侧部内表面具有第二夹角；
    该第一夹角＜90°，优选地，该第一夹角值为5～30°；
    该第二夹角＜90°，优选地，该第二夹角值为5～30°；
    更优选地，该第一夹角和第二夹角大致相等。
  31. 根据权利要求29所述的大尺寸高纯碳化硅单晶的制备方法，其特征在于，该坩埚的开口面至其上方的保温结构顶部内表面具有第一距离，该第一距离沿着该坩埚中心至坩埚边缘的方向增大；
    该第一距离的变化值的范围为5‐50mm。
  32. 根据权利要求29所述的大尺寸高纯碳化硅单晶的制备方法，其特征在于，该保温结构的外表面为圆柱体，该保温结构顶部不具有开口；该保温结构底部的内表面大致为圆柱状；沿着该坩埚底部至其开口方向，该保温结构侧部内表面沿着远离该坩埚中心轴线的方向延伸；该保温结构顶部沿着坩埚边缘至中心的方向增厚；
    该坩埚的侧壁内表面为大致圆柱状，该坩埚的外壁具有与该保温结构侧部内表面大致相同的延伸方向。
  33. 一种大尺寸高纯碳化硅单晶，其特征在于，由权利要求25‐32中任一项所述的方法制备。
  34. 一种制备大尺寸高纯碳化硅单晶衬底的方法，其特征在于，包括权利要求25‐32中任一项所述的大尺寸高纯碳化硅单晶的制备方法，和步骤4)衬底制备阶段：将制得的高纯碳化硅单晶进行切割、研磨和抛光，制得高纯半绝缘碳化硅单晶衬底。
  35. 一种大尺寸高纯碳化硅单晶衬底，其特征在于，由权利要求34所述的方法制备。
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