CN112626619B - Silicon carbide single crystal ingot, substrate and preparation method thereof - Google Patents

Silicon carbide single crystal ingot, substrate and preparation method thereof Download PDF

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CN112626619B
CN112626619B CN202011344165.2A CN202011344165A CN112626619B CN 112626619 B CN112626619 B CN 112626619B CN 202011344165 A CN202011344165 A CN 202011344165A CN 112626619 B CN112626619 B CN 112626619B
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silicon carbide
carbide substrate
hexagonal
nitrogen
single crystal
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CN112626619A (en
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方帅
高宇晗
高超
石志强
杨世兴
宗艳民
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Shandong Tianyue Advanced Technology Co Ltd
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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
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    • 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
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    • H01L29/16—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table
    • H01L29/1608—Silicon carbide
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
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Abstract

The application relates to a silicon carbide single crystal ingot, a silicon carbide single crystal substrate and a preparation method of the silicon carbide single crystal ingot and the silicon carbide single crystal substrate, and belongs to the field of semiconductor materials. The silicon carbide substrate contains nitrogen elements, the silicon carbide substrate has not more than 50 hexagonal color spots, and sides forming the hexagonal color spots are perpendicular to the <10-10> direction; the limit of hexagon color spot includes inboard side and outside limit, and the hexagonal region is enclosed into to inboard side, contains the cavity between inboard side and the outside limit, and the center of the cavity of not less than 80% quantity is in the one side of the axis between inboard side and outside limit. The silicon carbide substrate containing nitrogen has the advantages that the novel defects, namely hexagonal color spots and few cavity defects exist, the resistivity of the silicon carbide substrate is uniform, and the electrical performance of a semiconductor device manufactured by the silicon carbide substrate is excellent; the silicon carbide substrate has excellent performance such as breakdown field strength, and the prepared device has extremely low number of cavities generated by extension.

Description

Silicon carbide single crystal ingot, substrate and preparation method thereof
Technical Field
The application relates to a silicon carbide single crystal ingot, a silicon carbide single crystal substrate and a preparation method of the silicon carbide single crystal ingot and the silicon carbide single crystal substrate, and belongs to the field of semiconductor materials.
Background
Silicon carbide single crystal is one of the most important third-generation semiconductor materials, and is widely applied to the fields of power electronics, radio frequency devices, photoelectronic devices and the like because of the excellent properties of large forbidden bandwidth, high saturated electron mobility, strong breakdown field, high thermal conductivity and the like. At present, the main preparation method of the silicon carbide single crystal is a Physical Vapor Transport (PVT) method, and the method is the most successful method for growing the SiC crystal with large diameter so far. The method is mainly used for growing SiC crystals through transporting a gas phase source generated by sublimating a silicon carbide raw material to a seed crystal at high temperature for recrystallization.
The SiC devices that have matured so far include: the silicon carbide Schottky diode mainly adopts a junction type barrier Schottky diode or a mixed p-n Schottky diode structure; silicon carbide metal-oxide-semiconductor field effect transistors and SiC power modules are rapidly developed in the fields of photovoltaic power generation, wind power, electric vehicles, locomotive traction, ships and the like; the application of SiC in photoelectric devices mainly comprises green light emitting diodes, blue light emitting diodes and ultraviolet photodiodes.
Some companies have been able to provide Φ 1 inch, 2 inch, 3 inch, and 4 inch silicon carbide substrates, although large size substrates are currently available. The existing SiC substrate still has many structural defects, such as micropipes, dislocations, inclusions, damascene structures and the like, but there is a gap in large-scale application of the SiC substrate, because the performance of the device depends on the quality of the SiC substrate, and particularly, the defects of the SiC substrate affect the quality of the manufactured device. The presence of micropipes, dislocations, inclusions and damascene structures in silicon carbide substrates has been known and the solutions studied have been numerous. However, the requirement of the growing quality of the silicon carbide single crystal is high, the influence factors are complex, the defect recognition of the silicon carbide single crystal is still in an incomplete stage, and the quality of the silicon carbide single crystal is important for the manufactured device, so that the quality of the silicon carbide substrate needs to be improved continuously to ensure the quality of the manufactured device.
Disclosure of Invention
In order to solve the above problems, a silicon carbide single crystal ingot, a substrate, and a method for producing the same are provided. The application discovers a novel defect, namely a cavity defect existing on a hexagonal color spot and a hexagonal color spot, wherein the color of the hexagonal color spot is different from that of a silicon carbide main body area, but the hexagonal color spot is not a hexagonal cavity different from that of a planar hexagonal cavity defect, so that the resistivity of a silicon carbide substrate is not uniform due to the hexagonal color spot, and the electrical property of a semiconductor device made of the silicon carbide substrate is seriously influenced, for example, the device made on the silicon carbide substrate is invalid; the presence of voids not only affects the properties of the silicon carbide wafer, such as breakdown field strength, but voids may extend to devices made with the silicon carbide substrate as the substrate. The present application thus provides a silicon carbide wafer and a silicon carbide ingot containing hexagonal shaped stains and a small number of voids. The silicon carbide substrate containing nitrogen has the advantages that the novel defects, namely hexagonal color spots and few cavity defects exist, the resistivity of the silicon carbide substrate is uniform, and the electrical performance of a semiconductor device manufactured by the silicon carbide substrate is excellent; the silicon carbide substrate has excellent performance such as breakdown field strength, and the prepared device has extremely low number of cavities generated by extension.
According to one aspect of the present application, there is provided a silicon carbide substrate comprising an element of nitrogen, the silicon carbide substrate having no more than 50 hexagonal color spots, edges forming the hexagonal color spots being perpendicular to <10-10> directions; the side of the hexagonal color spot comprises an inner side and an outer side, the inner side is surrounded into a hexagonal area, a cavity is arranged between the inner side and the outer side, and the centers of the cavities with the number not less than 80% are arranged on one side of a central axis between the inner side and the outer side. The silicon carbide substrate has few hexagonal color spots and novel hollow defects, and the quality of the substrate is high. The voids are more concentrated in the edge regions of the hexagonal color spots and are easier to repair. Since the number of holes is an integer, the result of obtaining the number of 80% of the number of holes is rounded to an integer when the decimal point is included.
Optionally, no less than 90% of the number of said voids are centered on one side of the central axis between said medial and lateral edges; the number of cavities contained in the edges of the hexagonal color spot is not more than 10.
Optionally, the sides of the hexagonal color patch contain no more than 8 voids. Preferably, the sides of the hexagonal color patch contain no more than 5 voids. More preferably, the hexagonal color patch contains no more than 3, and still more preferably 0, holes at the sides.
Optionally, the silicon carbide substrate has an upper limit for the number of hexagonal shaped spots selected from the group consisting of 25, 20, 15, 10, 5, and 3 and a lower limit selected from the group consisting of 25, 20, 15, 10, 5, 3, and 0. Preferably, the silicon carbide substrate has a number of hexagonal color spots of not more than 10. More preferably, the silicon carbide substrate has no more than 3 hexagonal color spots in number. More preferably, the silicon carbide substrate has a number of hexagonal color spots of 0.
Optionally, not less than 80% of the number of the voids have their centers at the connecting region of each side of the hexagonal shaped stain. Further, not less than 90% of the number of the centers of the voids is in the connecting area of each side of the hexagonal color patch. Optionally, the hexagonal shaped stain has a greater number of short sides than there are voids.
Optionally, the ratio of the edges of the hexagonal color spots to the hexagonal area occupying the area of the silicon carbide substrate is 0-2 mm26 inch. Preferably, the ratio of the edges of the hexagonal color spots to the hexagonal area in the area of the silicon carbide substrate is 0 to 1.5mm2A/6 inch, more preferably 0 to 1mm20-0.5 mm in a length of 6 inches26 inch.
Optionally, the width between the inner side and the outer side of the edge of the hexagonal color spot is not more than 1 mm; and/or the distance between the two sides of the six sides of the hexagonal color spot that are furthest apart is no greater than 5 mm. Preferably, the upper limit of the border width range of the hexagonal color spots is selected from 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm or 10 μm. The upper limit of the range of distances between the two most distant sides of the six sides of the hexagonal color spot is selected from 4mm, 3mm, 2mm, 1mm, 800 μm, 500 μm, 400 μm, 300 μm, 200 μm, 100 μm, 50 μm or 10 μm. Optionally, the hexagonal color patch is a scalene hexagon.
Optionally, the diameter of the silicon carbide substrate is not less than 75 mm. Preferably, the diameter of the silicon carbide substrate is not less than 100 mm. More preferably, the diameter of the silicon carbide substrate is not less than 150 mm.
Optionally, the silicon carbide substrate has a nitrogen content of 5 × 1017～5×1019cm-3. Preferably, the nitrogen in the silicon carbide substrate containsIn an amount of 5X 1018～1×1019cm-3. More preferably, the silicon carbide substrate is N-type silicon carbide, and the nitrogen content in the silicon carbide substrate is 6 x 1018～9×1018cm-3。
Optionally, the silicon carbide substrate is a hexagonal single crystal. Preferably, the crystal form of the silicon carbide substrate is 4H-SiC or 6H-SiC.
Alternatively, a large amount of hexagonal color spots may be generated in the nitrogen-doped N-type silicon carbide single crystal, and the silicon carbide substrate has a resistivity of 0.002 Ω · cm to 0.06 Ω · cm when the silicon carbide substrate is an N-type silicon carbide single crystal. Preferably, the silicon carbide substrate has a resistivity of 0.015 Ω · cm to 0.028 Ω · cm. More preferably, the silicon carbide substrate has a resistivity of 0.018 Ω · cm to 0.022 Ω · cm.
Optionally, the silicon carbide substrate has a silicon carbide main body region outside the edges of the hexagonal color spots, the edges of the hexagonal color spots enclose a hexagonal region, and the edges of the hexagonal color spots are different from the silicon carbide main body region and the hexagonal region in color observed by an optical microscope; and/or
The sides of the hexagonal color patches are different from the nitrogen content of the silicon carbide body region and the hexagonal region, respectively. The formation of hexagonal spots may be related to whether the distribution of nitrogen content is uniform, while the color of the edge of the hexagonal spots appears different when observed in different light intensity and aperture modes of an optical microscope, e.g., the color of the edge of the hexagonal spots is whitish when observed in one of the light intensity and aperture modes in a polarization mode, while the main region of silicon carbide is yellow. For example, the color of the edge of the hexagonal color spot is yellowish when viewed with another light intensity and aperture in the polarized mode, while the silicon carbide main region is dark green.
Further, the edge color of the hexagonal color spot includes the case of uniform and non-uniform color; its boundaries include clear and unclear cases. The shape of a hexagonal stain may appear blurred as a pentagon, quadrangle, trilateral or circle-like shape because one or more sides are short. When the area of the hexagonal color spot is large, the difference between the edge of the hexagonal color spot and the hexagonal area is obvious; however, when the hexagonal mottle region is small, the edges of the hexagonal mottle and the boundaries of the hexagonal region may be blurred and may be merged with each other.
Preferably, the nitrogen content of the hexagonal regions is no less than the nitrogen content of the silicon carbide body regions is greater than the nitrogen content of the sides of the hexagonal color spots. More preferably, the difference between the nitrogen contents of the hexagonal regions and the silicon carbide main body region is a, the difference between the nitrogen contents of the silicon carbide main body region and the silicon carbide main body region is B, and the difference a is not less than B.
Optionally, the difference A is greater than B and the nitrogen content is 4 × 1018～1×1019In the N-type silicon carbide of (2), the difference A is in the range of 1.5X 1018-4.5×1018cm-3The difference B is in the range of 0.1X 1018-2.5×1018cm-3。
According to one embodiment, the nitrogen content of the hexagonal regions, the silicon carbide bulk region, and the sides of the hexagonal color spots are 4.7 × 1018cm-3、4×1018cm-3、7.7×1018cm-3。
Optionally, the hexagonal color spots form hexagons on a long crystal plane of the silicon carbide substrate; the edges of the hexagonal color patches extend along the C-axis within the silicon carbide substrate. The crystal form of the silicon carbide substrate is 4H-SiC or 6H-SiC.
According to another aspect of the present application, there is provided a method for producing the silicon carbide single crystal substrate, the method including the steps of:
1) preparing a silicon carbide single crystal ingot:
providing a crucible having a nitrogen gas channel disposed within the crucible sidewall and extending around the crucible interior cavity, the nitrogen gas channel having an inner sidewall less dense than an outer sidewall of the nitrogen gas channel;
placing a silicon carbide seed crystal at the inner top of a crucible and a silicon carbide raw material at the inner bottom of the crucible, and placing the crucible in a crystal growth furnace after assembling a heat preservation structure outside the crucible;
growing a silicon carbide single crystal ingot by using a physical vapor transport method, and permeating nitrogen into the inner cavity of the crucible through the nitrogen channel in the growth process of the silicon carbide single crystal to adjust the distribution of nitrogen in the prepared silicon carbide single crystal ingot;
2) and (3) subjecting the prepared silicon carbide single crystal ingot to a step including slicing to obtain the silicon carbide substrate.
Optionally, the nitrogen gas channel is a spiral channel, the spiral channel spirally extends around the inner cavity of the crucible along the axial direction of the crucible, and is wound at least once between the bottom and the top of the crucible.
Preferably, the inner liner and the outer shell are respectively barrel-shaped, the inner liner is sleeved in the outer shell and is tightly detachably connected with the outer shell, a spiral nitrogen channel is formed at the interface of the inner liner and the outer shell, the air inlet and the air outlet of the nitrogen channel are both arranged at the bottom end of the crucible, namely the spiral nitrogen channel is wound twice between the bottom and the top of the crucible, and the principle of introducing nitrogen is similar to that of circulating water.
Optionally, the wall thickness C of the portion of the lining where the nitrogen channel is formed is 3-5mm, the wall thickness C is too small to be corroded through easily, nitrogen directly enters the inner cavity of the crucible to affect crystal growth stability, and the wall thickness C is too large to hinder the nitrogen from diffusing into the crucible, so that the arrangement mode increases the permeability of the nitrogen without affecting heating.
Optionally, the method for growing the silicon carbide single crystal ingot by using the physical vapor transport method comprises the following steps:
controlling the temperature and pressure of the crystal growth furnace and the flow of inert gas introduced into the crystal growth furnace so as to clean and remove impurities in the crystal growth furnace;
a temperature rising stage: adjusting the temperature of the crystal growth furnace to 1800-2400K, and controlling the pressure in the crucible to be 0.6 multiplied by 105～1.2×105Pa, the flow rate of inert gas introduced into the crystal growth furnace is 50-500mL/min, and the flow rate V of nitrogen introduced into the nitrogen channel1Is 20-200 mL/min;
crystal growth stage: increasing the flow rate V of nitrogen introduced into the nitrogen channel250-500mL/min, V2Greater than V1The crystal growth temperature is 2200K-2800K, the crystal growth pressure is 100-5000Pa,keeping the time for 80-120 h to obtain the silicon carbide single crystal ingot.
Optionally, the crystal growth stage comprises a first crystal growth stage and a second crystal growth stage, the time ratio of the first crystal growth stage to the second crystal growth stage is 1:0.8-1.2, and the nitrogen inlet and the nitrogen outlet of the first crystal growth stage and the second crystal growth stage are exchanged.
Preferably, the flow rate of the inert gas is 300-400 mL/min. More preferably, the inert gas flow rate is 300 mL/min. Preferably, the inert gas is argon and/or helium.
Preferably, the nitrogen flow rate V of the warming stage1Is 40 to 100 mL/min. More preferably, said nitrogen flow rate V of said warming phase1The concentration was 60 mL/min. Preferably, said nitrogen flow rate V of said seeding stage2110-400 mL/min. More preferably, the nitrogen flow rate V of the crystal growth stage2Is 300 mL/min. The number and the density of hexagonal color spots can be reduced by the control mode of nitrogen partial pressure and nitrogen flow in different stages. Preferably, the nitrogen is high-purity nitrogen with the purity of not less than 99.99 percent.
Optionally, the crucible includes a liner and a shell, the liner forming an inner sidewall of the nitrogen gas channel, the shell forming an outer sidewall of the nitrogen gas channel, the liner having a density less than a density of the shell. Preferably, the density of the liner is not higher than 1.75g/cm3. Preferably, the density of the shell is not less than 1.85g/cm3. More preferably, the density of the shell is not less than 1.90g/cm3. Preferably, the crucible is made of graphite. The shell is made of a denser graphite material, so that the loss of the atmosphere at high temperature can be reduced, and particularly, the escape of evaporated silicon atmosphere is prevented, so that the carbon-rich atmosphere which can cause hexagonal color spots is reduced. The nitrogen slowly permeates in the inner lining and diffuses according to concentration gradient, the density of the inner lining and the density of the outer shell are different, the resistance to outward diffusion is larger, so that more nitrogen diffuses inwards, the nitrogen concentration at the edge of the seed crystal surface in the crucible is larger than the center of the seed crystal surface, even if the radial temperature exists due to the PVT method, the structure is adoptedAnd the ventilation mode can balance the nonuniformity brought by the PVT method, so that the resistivity is very uniform, and the number and the density of hexagonal color spots are effectively reduced.
Optionally, the silicon carbide raw material is silicon carbide polycrystal or silicon carbide powder. Further, the silicon carbide raw material is silicon carbide powder, the silicon carbide raw material filled in the crucible comprises an upper layer raw material and a lower layer raw material, the upper layer raw material is smaller than the particle size of the lower layer raw material, and the proportion of the upper layer raw material in the silicon carbide raw material is 30-40V%. Preferably, the particle size of the upper layer raw material is 5-10mm, and the particle size of the lower layer raw material is 20-30 mm. The great homogeneity that can increase the interior temperature distribution of bottom raw materials of the thermal radiance of the big granule raw materials between the raw materials of bottom between the gap is great, will make the raw materials evaporation faster under a suitable temperature like this, but the big granule raw materials can cause the unevenness of atmosphere to the transmission of growth intracavity, consequently at the little granule raw materials of raw materials overhead 5-10mm, provide less atmosphere pore, make originally stronger atmosphere flow evenly open through more dense aperture, make the atmosphere more even. After the atmosphere is uniform, the supersaturation degree of the crystal growth surface becomes uniform, so that the crystal growth is more stable, and the number and density of hexagonal color spots are effectively reduced. On the other hand, the lower layer of raw material is large-particle SIC powder, so that the time for completely carbonizing raw material particles is reduced, and the carbon-rich atmosphere which can cause hexagonal color spots is reduced.
Optionally, the coating is a TaC coating. The arrangement of the coating prevents the back evaporation of the seed crystal in the crystal growth process from causing void defects on hexagonal color spots. Preferably, the coating is formed by a CVD method (chemical vapor deposition), a PVD method (physical vapor deposition) or an MBE method (molecular beam epitaxy).
Optionally, the silicon surface of the silicon carbide seed crystal has a roughness Ra < 0.5. To reduce the number of internal dislocations of a silicon carbide single crystal, particularly TSD (threading dislocations). Before crystal growth, the carbon surface of the seed crystal is subjected to fine polishing treatment to make the surface of the seed crystal fully smooth, and the Si surface of the seed crystal is also subjected to fine polishing treatment to make the surface of the seed crystal free from scratches and as smooth as possible.
Optionally, silicon powder is filled in the middle of the silicon carbide raw material. Preferably, the silicon powder is loaded in a loader provided with a through hole, the loader being loaded in the middle of the silicon carbide raw material. Silicon powder is filled in the silicon carbide raw material to compensate silicon in sublimation atmosphere during silicon carbide single crystal growth, and the silicon powder is further placed in the middle because the heating coil in the PVT growth method has the lowest temperature in the heating crucible, so that the silicon powder cannot be volatilized too early in the initial crystal growth stage, and the carbon-rich atmosphere which can cause hexagonal color spots is reduced.
According to another aspect of the present application, there is provided a silicon carbide single crystal ingot processed to form a silicon carbide substrate including a slicing step; the silicon carbide substrate is selected from the silicon carbide substrate described in any one of the above or the silicon carbide substrate prepared by any one of the above methods.
Optionally, the silicon carbide single crystal ingot is processed by steps including cutting and polishing to form a silicon carbide substrate. Further, the silicon carbide single crystal ingot is subjected to end face machining, multi-line cutting, grinding, mechanical polishing, chemical mechanical polishing, cleaning and packaging, and a silicon carbide substrate which is used after being opened is formed.
Optionally, the width of the sides of the hexagonal color spot increases, and the distance between two sides of the six sides of the hexagonal color spot that are farthest from each other increases, along the growth direction of the silicon carbide single crystal extending along the C-axis.
Alternatively, hexagonal mottling may occur in a partial region of the silicon carbide single crystal ingot in the growth direction of the silicon carbide single crystal extending along the C-axis, that is, the number of hexagonal mottling differs in the silicon carbide substrate produced after the same silicon carbide single crystal ingot is sliced.
Optionally, it includes the method for producing a silicon carbide single crystal ingot of the step 1) in the method for producing a silicon carbide substrate described in any one of the above.
In the present application, the hexagonal color spot is a novel defect in the silicon carbide substrate, each side of the hexagonal color spot is flush with the surface of the silicon carbide main body region, is not a hexagonal pit, but presents a hexagonal or nearly hexagonal shape with a different color from the silicon carbide main body region, the region composed of the sides of the hexagonal color spot is defined as the hexagonal color spot, and other properties are referred to in other parts of the present application.
In the present application, the number of holes included in the sides of the hexagonal color patches is the number of holes included in all the sides of each hexagonal color patch, unless otherwise specified.
Benefits of the present application include, but are not limited to:
1. according to the silicon carbide substrate, a novel defect, namely a hexagonal color spot and a cavity defect existing on the hexagonal color spot is found, the color of the hexagonal color spot is different from that of a silicon carbide main body area, but the hexagonal color spot is not a hexagonal cavity different from that of a planar hexagonal cavity defect, the hexagonal color spot can enable the resistivity of the silicon carbide substrate to be uneven, and the electrical performance of a semiconductor device made of the silicon carbide substrate can be seriously affected, for example, a device made on the silicon carbide substrate is enabled to be invalid; the presence of voids not only affects the properties of the silicon carbide wafer, such as breakdown field strength, but voids may extend to devices made with the silicon carbide substrate as the substrate. The present application thus provides a silicon carbide wafer and a silicon carbide ingot that contain hexagonal shaped stains and a low number of voids. The silicon carbide substrate containing nitrogen has the advantages that the novel defects, namely hexagonal color spots and few cavity defects exist, the resistivity of the silicon carbide substrate is uniform, and the electrical performance of a semiconductor device manufactured by the silicon carbide substrate is excellent; the silicon carbide substrate has excellent performance such as breakdown field strength, and the prepared device has extremely low number of cavities generated by extension.
2. According to the silicon carbide substrate of the present application, the silicon carbide substrate has a low defect density of dislocations, carbon inclusions, stacking faults, and the like, and has a uniform resistivity.
3. According to the preparation method of the silicon carbide substrate, the prepared silicon carbide substrate is low in density and quantity of hexagonal color spots, few in void defects, low in density of defects such as dislocation, carbon inclusion and stacking fault and uniform in resistivity, and the number of the hexagonal color spots is small; the control method is simple and convenient to operate.
4. According to the silicon carbide single crystal ingot, the hexagonal color spots are found to exist in the nitrogen-containing silicon carbide crystal ingot, the color of the hexagonal color spots is different from that of a silicon carbide main body area, but the hexagonal color spots are not hexagonal holes different from plane hexagonal void defects, the hexagonal color spots can cause the non-uniform resistivity of the silicon carbide crystal ingot, the silicon carbide substrate made of the silicon carbide crystal ingot can be seriously influenced, and further the electrical performance of a semiconductor device made of the silicon carbide crystal ingot is influenced, for example, the device made on the silicon carbide substrate is made to be invalid, and the silicon carbide crystal ingot has low density of the hexagonal color spots; it has also been found that the presence of voids not only affects the properties of the silicon carbide wafer, such as breakdown field strength, but that voids may extend into devices made with the silicon carbide substrate as the substrate.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
FIG. 1 is a schematic view of the assembled crucible placed in a crystal growth furnace.
Fig. 2a, 2b, and 2c are schematic views showing 3 kinds of hexagonal color spots existing in silicon carbide substrate 2# at the initial stage of crystal growth in the silicon carbide single crystal ingot according to example 1 of the present application.
Fig. 3a, 3b, and 3c are schematic views showing 3 kinds of hexagonal spots present in mid-growth sic substrate 8# obtained from the sic single crystal ingot according to example 1 of the present application.
Fig. 4a, 4b, and 4C show hexagonal spots at the same C-axis position in 3 consecutive silicon carbide substrates extending in the growth direction in the silicon carbide single crystal ingot according to example 1 of the present application.
Fig. 5 shows a hexagonal color spot of a silicon carbide substrate 8# according to example 1 of the present application.
Fig. 6 is the hexagonal stain of fig. 5 after etching.
The nitrogen content associated with one hexagonal stain in the silicon carbide substrate of figure 4c in the silicon carbide substrate of figure 7 silicon carbide substrate 8 #.
FIG. 8 is a schematic structural view of a silicon carbide substrate according to an embodiment;
fig. 9 is a schematic view of the structure of several consecutive silicon carbide substrates sliced from a silicon carbide ingot into silicon carbide substrates according to one embodiment.
Detailed Description
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
Unless otherwise specified, the raw materials and catalysts in the examples of the present application were purchased commercially.
The analysis method in the examples of the present application is as follows:
observing the appearance of the hexagonal color spots by using an Olympus multifunctional optical microscope;
detecting the nitrogen content of the silicon carbide single crystal by using Secondary Ion Mass Spectrometry (SIMS) which is Secondary Ion Mass Spectroscopy;
testing the elemental composition of the silicon carbide substrate by using a Raman spectrometer;
the quality of the crystal and the crystal structure such as the crystal orientation are detected by testing the half-peak width of the substrate by using high-resolution XRD.
Example 1
Referring to fig. 1, the crucible side wall is provided with a nitrogen gas channel 6, the nitrogen gas channel 6 being arranged within the crucible side wall and extending around the crucible inner cavity, the inner side wall of the nitrogen gas channel being less dense than the outer side wall of the nitrogen gas channel.
In one embodiment, the crucible 2 comprises an inner liner 21 and an outer shell 22, the side wall of the crucible forms a nitrogen channel 6, the nitrogen channel 6 is a spiral channel, the spiral channel spirally extends around the inner cavity of the crucible along the axial direction of the crucible, and the nitrogen channel is wound at least once between the bottom and the top of the crucible. For example, the nitrogen passage extends from the inlet 71 at the bottom of the crucible to the top of the crucible and then extends to the bottom of the crucible to form the outlet 72.
Specifically, the liner 21 and the shell 22 are respectively barrel-shaped, the liner 21 is sleeved in the shell 22, the liner 21 and the shell 22 are arranged in a sealing, fitting and splicing manner, a spiral nitrogen channel is formed at the interface of the liner 21 and the shell 22, namely, half of the inner wall of each of the liner 21 and the shell 22 is formed, the liner 21 and the shell 22 are spliced to form a spiral channel, the air inlet 71 and the air outlet 72 of the nitrogen channel are both arranged at the bottom end of the crucible, namely, the spiral nitrogen channel is wound twice between the bottom and the top of the crucible.
As an embodiment, the wall thickness C of the part of the inner lining forming the nitrogen channel 6 is 3-5mm, the wall thickness C is too small and is easy to be corroded through, the nitrogen directly flows into the inner cavity of the crucible to influence the crystal growth stability, the wall thickness C is too large and is easy to block the diffusion of the nitrogen to the inner side of the crucible, and the arrangement mode is used for increasing the permeability of the nitrogen under the condition of not influencing the heat generation.
Example 2
Referring to fig. 1, according to an embodiment of the present application, a method of preparing a silicon carbide single crystal ingot using the crucible of example 1 includes the steps of:
1) preparing a silicon carbide single crystal ingot:
providing the crucible of example 1 with a nitrogen channel disposed within the sidewall of the crucible and extending around the crucible interior cavity, the inner sidewall of the nitrogen channel being less dense than the outer sidewall of the nitrogen channel;
placing a silicon carbide seed crystal 1 at the top in a crucible 2 and a silicon carbide raw material 3 at the bottom in the crucible 2, assembling a heat preservation structure 3 outside the crucible 2, placing the crucible in a crystal growth furnace 4, and heating by using an induction coil 5;
the temperature controller 12 controls the temperature of the crystal growth furnace, controls the pressure through the vacuum system 8 and controls the flow of inert gas introduced into the crystal growth furnace 10 through the inert gas system 9 so as to clean and remove impurities in the crystal growth furnace 10;
a temperature rising stage: the temperature of the crystal growth furnace is adjusted to 1800-2400K, and the pressure in the crucible 2 is controlled to be 0.6 multiplied by 105～1.2×105Pa, the flow rate of inert gas introduced into the crystal growth furnace 10 is 50-500mL/min, and the flow rate V of nitrogen introduced into the nitrogen channel120-200 mL/min;
crystal growth stage: increasing the flow rate V of nitrogen introduced into the nitrogen channel250 to 500mL/min, V2Greater than V1The crystal growth temperature is 2200K-2800K, the crystal growth pressure is 100-;
stopping introducing the nitrogen, continuously introducing the inert gas, and keeping the flow of the introduced inert gas unchanged;
and (3) cooling: turning off the intermediate frequency heating power supply, increasing the circulating water flow in the quartz tube of the crystal growth furnace, rapidly cooling the crystal growth furnace chamber for about 10h, and turning off the flow of the protective inert gas after the cooling is finished;
opening the furnace to obtain 4-inch, 6-inch or 8-inch N-type silicon carbide single crystal ingots with uniform resistivity after the temperature reduction is finished;
2) and (3) subjecting the prepared silicon carbide single crystal ingot to a step including slicing to obtain a silicon carbide substrate.
The direction of the edge of the hexagonal color spot was detected by X-ray diffraction on the obtained silicon carbide substrate and was perpendicular to the <10-10> direction. A schematic view of the structure of a silicon carbide substrate produced is shown in fig. 8, and a schematic view of the structure of a silicon carbide ingot produced cut into silicon carbide substrates is shown in fig. 9.
EXAMPLE 3 preparation of silicon carbide single crystal ingot # 1
The preparation method of the silicon carbide single crystal ingot 1# comprises the following steps:
a crucible of example 1 was provided having a nitrogen gas channel disposed within the sidewall of the crucible and extending around the crucible interior, the nitrogen gas channel having an inner sidewall density of 1.70g/cm3The density of the shell is 1.90g/cm3；
Placing a silicon carbide seed crystal at the inner top of a crucible and a silicon carbide powder at the inner bottom of the crucible, assembling a heat preservation structure outside the crucible and sealing the crucible in a crystal growth furnace;
controlling the temperature and pressure of the crystal growth furnace and the flow of argon introduced into the crystal growth furnace to clean and remove impurities in the crystal growth furnace;
a temperature rising stage: adjusting the temperature of the crystal growth furnace to 2200K, and controlling the pressure in the crucible to be 0.9 multiplied by 105Pa, the flow of the argon introduced into the crystal growth furnace is 300mL/min, and the flow of the nitrogen introduced into the nitrogen channel is V140 mL/min;
a crystal growth stage: increasing the flow rate V of nitrogen introduced into the nitrogen channel2200mL/min, the crystal growth temperature of 2400K, the crystal growth pressure of 1000Pa and the retention time of 100 h;
stopping introducing the nitrogen, continuously introducing inert gas, and keeping the flow of introduced argon unchanged;
and (3) cooling: turning off the intermediate frequency heating power supply, increasing the circulating water flow in the quartz tube of the crystal growth furnace, rapidly cooling the crystal growth furnace chamber for 10h, and turning off the flow of the protective inert gas after the cooling is finished;
and opening the furnace to obtain the N-type silicon carbide single crystal ingot with uniform resistivity, wherein the N-type silicon carbide single crystal ingot is No. 1 after the temperature reduction is finished.
The silicon carbide substrate was prepared by subjecting silicon carbide single crystal ingot # 1 to end face machining, multi-wire slicing, grinding, mechanical polishing, chemical mechanical polishing, cleaning and packaging, and forming a 6-inch silicon carbide substrate ready for use in an open box, and the preparation method is not limited to 6-inch silicon carbide single crystal, and may be 4-inch, 8-inch, 12-inch, and the like. Taking a silicon carbide substrate with the following dimensions as an example, a silicon carbide single crystal ingot 1# produces a plurality of silicon carbide substrates with a thickness of 350 ± 25 μm and a dimension of 6 inches, and the silicon carbide substrates 1#, 2#, 3#, 4# and the like are respectively arranged along the crystal growth direction from the seed crystal, and so on. The silicon carbide substrate 2# belongs to the initial stage of crystal growth, the silicon carbide substrate 8# belongs to the middle stage of crystal growth, and the number of hexagonal color spots in the silicon carbide substrate is the same.
Fig. 2a, 2b, 2c show 3 different hexagonal color patches in the silicon carbide substrate 1#, respectively. Fig. 3a, 3b, 3c show the presence of 3 different hexagonal color spots, respectively, in the silicon carbide substrate 4 #. Fig. 4a, 4b, and 4c show the extension of the same hexagonal color patch present in the silicon carbide substrates 6#, 7#, and 8#, respectively.
The silicon carbide single crystal wafer has 10 hexagonal color spots, the content of cavities on all the hexagonal color spots is 25, wherein 20 cavities are close to the inner side edge, and the nitrogen content is 6-8 multiplied by 1018cm-3The resistivity is 0.020-0.024 Ω & cm, and the total area of the sides and cubic region of the hexagonal color spot is 2 square millimeters.
EXAMPLE 4 preparation of silicon carbide single crystal ingot No. 2
The method for producing the silicon carbide single crystal ingot 2# of the present example is different from the method for producing the silicon carbide single crystal ingot 1# of example 3 in that the crystal growth stage includes a first crystal growth stage and a second crystal growth stage, a time ratio of the first crystal growth stage to the second crystal growth stage is 1:1, a nitrogen gas inlet and a nitrogen gas outlet of the first crystal growth stage and the second crystal growth stage are exchanged, and the specific steps of crystal growth include:
a first crystal growth stage: firstly, increasing the nitrogen flow to 200ml/min, controlling the temperature of an infrared thermometer to be 2200K, controlling the absolute pressure in a growth chamber to be 1000Pa, and growing for 50 h;
a second crystal growth stage: and exchanging a nitrogen gas inlet and a nitrogen gas outlet, changing the gas inlet in the first stage into the gas outlet, changing the gas outlet into the gas inlet, controlling the temperature of the infrared thermometer to be 2400K, controlling the absolute pressure in the growth chamber to be 1000Pa, and growing for 50 h.
The number of hexagonal color spots in the silicon carbide single crystal wafer is 5, the content of voids existing in all the hexagonal color spots is 5, the positions of 5 voids close to the outer side edges are provided, and the nitrogen content is 8-9 multiplied by 1018cm-3The resistivity is 0.018-0.021 omega cm, and the total area of the edge part and the cubic area of the hexagonal color spots is less than 0.8 square millimeter.
EXAMPLE 5 preparation of silicon carbide single crystal ingot # 3
The silicon carbide single crystal ingot 3# of the present example differs from the method of producing the silicon carbide single crystal ingot 2# of example 4 in that,
a temperature rising stage: adjusting the temperature of the crystal growth furnace to 1800K, and controlling the pressure in the crucible to be 0.6 multiplied by 105Pa, the flow of argon gas introduced into the crystal growth furnace is 50mL/min, and the flow of nitrogen gas introduced into the nitrogen channel is V1Is 20 mL/min;
the specific steps of crystal growth comprise:
a first crystal growth stage: firstly, increasing the nitrogen flow to 150ml/min, controlling the temperature of an infrared thermometer to 2200K, controlling the absolute pressure in a growth chamber to be 200Pa, and growing for 50 h;
a second crystal growth stage: and exchanging a nitrogen gas inlet and a nitrogen gas outlet, changing the gas inlet in the first stage into the gas outlet, changing the gas outlet into the gas inlet, controlling the temperature of the infrared thermometer to 2200K, controlling the absolute pressure in the growth chamber to be 200Pa, and growing for 50 h.
The number of hexagonal color spots in the silicon carbide single crystal wafer is 8, and all the holes on the hexagonal color spots areHas a total of 15 nitrogen contents of 7-8X 1018cm-3The resistivity was 0.019 to 0.022 Ω · cm, and the total area of the sides and the cubic region of the hexagonal color patch was 1.2 square millimeters.
EXAMPLE 6 preparation of silicon carbide single crystal ingot No. 4
The silicon carbide single crystal ingot 4# of this example is different from the method for producing the silicon carbide single crystal ingot 1# of example 3 in that the silicon carbide raw material charged in the crucible includes an upper layer raw material and a lower layer raw material, the particle size of the upper layer raw material is 8mm, the particle size of the lower layer raw material is 25mm, and the proportion of the upper layer raw material in the silicon carbide raw material is 75V%.
The number of hexagonal color spots in the silicon carbide single crystal wafer is 7, the content of the cavities on all the hexagonal color spots is 14 in total, wherein 8 cavities are positioned close to the inner side edge, 4 cavities are positioned close to the outer side edge, and the nitrogen content is 7-8 multiplied by 1018cm-3The resistivity was 0.019 to 0.022 Ω · cm, and the total area of the sides and the cubic region of the hexagonal color patch was 1.7 square millimeters.
Example 7 preparation of silicon carbide single crystal ingot No. 5
The difference between the method for producing the silicon carbide single crystal ingot 4# of the present example and the method for producing the silicon carbide single crystal ingot 1# of the present example is that the rear surface of the silicon carbide seed crystal is epitaxially coated with TaC, the silicon surface of the silicon carbide seed crystal has a roughness Ra of less than 0.5, and the middle portion of the silicon carbide raw material is filled with silicon powder.
The number of hexagonal color spots in the silicon carbide single crystal wafer is 6, the content of the cavities on all the hexagonal color spots is 13 in total, wherein 3 cavities are near the inner side edge, 9 cavities are near the outer side edge, and the nitrogen content is 7-8 multiplied by 1018cm-3The resistivity was 0.019 to 0.022 Ω · cm, and the total area of the sides and the cubic region of the hexagonal color patch was 1.5 square millimeters.
EXAMPLE 8 detection of hexagonal spot defects in silicon carbide single crystal ingot No. 1-5 #
Respectively detecting hexagonal color spots existing in the silicon carbide single crystal ingots 1# -5#, and measuring the sides of the hexagonal color spots to be vertical to the silicon carbide single crystal ingots by an X-ray orientation instrument<10-10>Direction; raman detection is carried out to find hexagonThe color spots are not polytype; the hexagonal stain corrosivity test shows that the hexagonal stain is not dislocation, particularly not screw dislocation (TSD dislocation for short), the reference picture is a picture of a hexagonal stain in a silicon carbide substrate 8# (figure 5) and a picture after etching (figure 6), hexagonal stains, edge dislocations and screw dislocations are hexagonal etch pits after etching is finished, the figure shows that the etched edge dislocations and screw dislocations are smaller than the etch pits of the hexagonal stain in general, the screw dislocations are about tens of micrometers higher than the etch pits of the edge dislocations, the etch pits of the edge dislocations are about tens of micrometers to tens of micrometers, the sizes of the etch pits of the edge dislocations are related to the etching process, but the etched edge dislocations and the screw dislocations are smaller than the etch pits of the hexagonal stain in general, and the distribution of the edge dislocations and the screw dislocations is not obviously related to the hexagonal stain. The detection structure of the nitrogen element shows that the difference of the nitrogen contents of the hexagonal area larger than the silicon carbide main body area is A, the difference of the nitrogen contents of the silicon carbide main body area larger than the edges of the hexagonal color spots is B, and the difference A is larger than the difference B. Referring to fig. 7, the nitrogen contents of the hexagonal region, the silicon carbide main region, and the edge portion of the hexagonal color spot of fig. 4c in the silicon carbide substrate 8# were 7.7 × 10, respectively18cm-3、4.7×1018cm-3、4×1018cm-3。
Comparative example 1 preparation of silicon carbide single crystal ingot D1#
The method for producing silicon carbide single crystal ingot D1# according to the present example was different from the method for producing silicon carbide single crystal ingot 1# according to example 3 in that a nitrogen gas channel was not present in the crucible side wall, and nitrogen gas and argon gas were directly introduced into the growth furnace.
The number of the hexagonal color spots in the silicon carbide single crystal wafer is 55, the content of the holes on all the hexagonal color spots is 90, and the number of the holes on at least 1 hexagonal color spot is 12; wherein, 26 holes are near the inner side and 28 holes are near the outer side, and 36 holes are in the middle; the nitrogen content is 3-5 × 1018cm-3Resistivity of 0.023 to 0.030 ohm cm, and total area of side portions and cubic areas of hexagonal color spots of 3.9 square millimeters。
Comparative example 2 preparation of silicon carbide single crystal ingot D2#
The silicon carbide single crystal ingot D2# of the present example was different from the method for producing silicon carbide single crystal ingot 1# of example 3 in that the nitrogen flow rate in the temperature raising stage was 100mL/min and the nitrogen flow rate in the crystal growth stage was 50 mL/min.
The number of the hexagonal color spots in the silicon carbide single crystal wafer is 60, the content of the holes existing in all the hexagonal color spots is 102, and the number of the holes in at least 1 hexagonal color spot is 15; wherein, the positions of 42 cavities close to the inner side edge and the positions of 42 cavities close to the outer side edge, and 18 cavities are positioned in the middle; nitrogen content of 1-2X 1018cm-3The resistivity was 0.035 to 0.045 Ω · cm, and the total area of the sides and cubic regions of the hexagonal color spot was 4.0 square millimeters.
The above description is only an example of the present application, and the protection scope of the present application is not limited by these specific examples, but is defined by the claims of the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the technical idea and principle of the present application should be included in the protection scope of the present application.

Claims (15)

1. A method for producing a silicon carbide substrate, comprising the steps of:
1) preparing a silicon carbide single crystal ingot:
providing a crucible having a nitrogen gas channel disposed within the crucible sidewall and extending around the crucible interior cavity, the nitrogen gas channel having an inner sidewall less dense than an outer sidewall of the nitrogen gas channel;
placing a silicon carbide seed crystal at the inner top of a crucible and a silicon carbide raw material at the inner bottom of the crucible, and placing the crucible in a crystal growth furnace after assembling a heat preservation structure outside the crucible;
growing a silicon carbide single crystal ingot by using a physical vapor transport method, and permeating nitrogen into the inner cavity of the crucible through the nitrogen channel in the growth process of the silicon carbide single crystal ingot to adjust the distribution of nitrogen in the prepared silicon carbide single crystal ingot;
the method for growing the silicon carbide single crystal ingot by using the physical vapor transport method comprises the following steps:
controlling the temperature and pressure of the crystal growth furnace and the flow of inert gas introduced into the crystal growth furnace so as to clean and remove impurities in the crystal growth furnace;
a temperature rise stage: adjusting the temperature of the crystal growth furnace to 1800-2400K, and controlling the pressure in the crucible to be 0.6 multiplied by 105～1.2×105Pa, the flow rate of inert gas introduced into the crystal growth furnace is 50-500mL/min, and the flow rate V of nitrogen introduced into the nitrogen channel120-200 mL/min;
crystal growth stage: increasing the flow rate V of nitrogen introduced into the nitrogen channel250 to 500mL/min, V2Greater than V1The crystal growth temperature is 2200K to 2800K, the crystal growth pressure is 100 Pa to 5000Pa, and the holding time is 80 h to 120h, so that the silicon carbide single crystal ingot is prepared; the crystal growth stage comprises a first crystal growth stage and a second crystal growth stage, the time ratio of the first crystal growth stage to the second crystal growth stage is 1:0.8-1.2, and a nitrogen inlet and a nitrogen outlet of the first crystal growth stage and the second crystal growth stage are exchanged;
2) subjecting the obtained silicon carbide single crystal ingot to a step including slicing to obtain a silicon carbide substrate;
the silicon carbide substrate contains nitrogen elements, the silicon carbide substrate has no more than 10 hexagonal color spots, and sides forming the hexagonal color spots are perpendicular to <10-10> directions;
the edges of the hexagonal color spots comprise inner edges and outer edges, the inner edges surround a hexagonal area, cavities are arranged between the inner edges and the outer edges, and the centers of the cavities with the number not less than 80% are arranged on one side of a central axis between the inner edges and the outer edges; a connecting region of not less than 80% of the number of centers of the voids at each side of the hexagonal stain;
the outer side area of the edge of the hexagonal color spots of the silicon carbide substrate is a silicon carbide main body area, the edge of the hexagonal color spots is surrounded into a hexagonal area,
the difference of the nitrogen contents of the hexagonal areas larger than the silicon carbide main body area is A, the difference of the nitrogen contents of the silicon carbide main body area larger than the edges of the hexagonal color spots is B, and the difference A is not smaller than the difference B;
the ratio of the edges of the hexagonal color spots to the area of the hexagonal area in the silicon carbide substrate is 0-2 mm26 inch.
2. The method for producing a silicon carbide substrate according to claim 1, wherein not less than 90% by number of the voids have centers on one side of a central axis between the inner side edge and the outer side edge;
the number of cavities contained in the edges of the hexagonal color spot is not more than 10.
3. The method for producing a silicon carbide substrate according to claim 1, wherein the ratio of the hexagonal color spots at the edges to the hexagonal area in the area of the silicon carbide substrate is 0 to 1.5mm2And 6 inches.
4. The method for producing a silicon carbide substrate according to claim 1, wherein the width between the inner side edge and the outer side edge of the edge portion of the hexagonal color spot is not more than 1 mm; and/or
The distance between the two sides farthest away in the six sides of the hexagonal color spot is not more than 5 mm.
5. The method for producing a silicon carbide substrate according to claim 1, wherein the silicon carbide substrate has a diameter of not less than 75 mm; and/or
The content of nitrogen in the silicon carbide substrate is 5 x 1017~5×1019cm-3(ii) a And/or
The silicon carbide substrate is a hexagonal single crystal; and/or
The resistivity of the silicon carbide substrate is 0.002-0.06 omega-cm.
6. The method for producing a silicon carbide substrate according to claim 5, wherein the silicon carbide substrate has a diameter of not less than 100 mm; and/or
The content of nitrogen in the silicon carbide substrate is 5 x 1018~1×1019cm-3(ii) a And/or
The crystal form of the silicon carbide substrate is 4H-SiC or 6H-SiC; and/or
The resistivity of the silicon carbide substrate is 0.015-0.028 omega cm.
7. The method for producing a silicon carbide substrate according to claim 6, wherein the silicon carbide substrate has a diameter of not less than 150 mm; and/or
The silicon carbide substrate is N-type silicon carbide, and the nitrogen content in the silicon carbide substrate is 6 multiplied by 1018~9×1018cm-3。
8. The method of producing a silicon carbide substrate according to any one of claims 1 to 7, wherein the sides of the hexagonal color spots are different in color from the silicon carbide main region and the hexagonal region, respectively, as observed with an optical microscope.
9. The method for producing a silicon carbide substrate according to claim 4, wherein the hexagonal color spots form hexagons on a long crystal plane of the silicon carbide substrate; edges of the hexagonal color spots extend along a C-axis inside the silicon carbide substrate;
the width of the edge of the hexagonal color spot is not more than 1 mm; and/or
The distance between the two sides farthest away in the six sides of the hexagonal color spot is not more than 5 mm.
10. The method for producing a silicon carbide substrate according to claim 9, wherein the hexagonal color unevenness is a scalene hexagon.
11. The method of producing a silicon carbide substrate according to claim 1, wherein the crucible comprises an inner liner forming an inner side wall of the nitrogen gas channel and an outer shell forming an outer side wall of the nitrogen gas channel, the inner liner having a density lower than that of the outer shell.
12. The method for producing a silicon carbide substrate according to claim 11, wherein the density of the lining is not higher than 1.75g/cm3。
13. The method for producing a silicon carbide substrate according to claim 12, wherein the density of the shell is not less than 1.85g/cm3。
14. The method for producing a silicon carbide substrate according to claim 13, wherein the density of the crucible is not less than 1.90g/cm3。
15. A silicon carbide single crystal ingot, characterized in that the silicon carbide single crystal ingot is processed including a slicing step to form a silicon carbide substrate; the number of hexagonal color spots in the silicon carbide single crystal ingot is gradually reduced along the growth direction;
the silicon carbide substrate is selected from the silicon carbide substrates prepared by the method of any one of claims 1-14.
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