CN115261977A - Silicon carbide pretreatment method and device - Google Patents
Silicon carbide pretreatment method and device Download PDFInfo
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- CN115261977A CN115261977A CN202210934397.6A CN202210934397A CN115261977A CN 115261977 A CN115261977 A CN 115261977A CN 202210934397 A CN202210934397 A CN 202210934397A CN 115261977 A CN115261977 A CN 115261977A
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 135
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 78
- 238000002203 pretreatment Methods 0.000 title claims abstract description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 106
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 81
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 76
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 74
- 239000010703 silicon Substances 0.000 claims abstract description 73
- 238000000034 method Methods 0.000 claims abstract description 36
- 238000005245 sintering Methods 0.000 claims abstract description 28
- 238000010438 heat treatment Methods 0.000 claims description 35
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 20
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 10
- 238000009413 insulation Methods 0.000 claims description 6
- 230000004308 accommodation Effects 0.000 claims description 4
- 238000009529 body temperature measurement Methods 0.000 claims description 4
- 239000004215 Carbon black (E152) Substances 0.000 claims description 3
- 229930195733 hydrocarbon Natural products 0.000 claims description 3
- 150000002430 hydrocarbons Chemical class 0.000 claims description 3
- -1 hydrosilicon compound Chemical class 0.000 claims 1
- 239000013078 crystal Substances 0.000 abstract description 46
- 239000002245 particle Substances 0.000 abstract description 34
- 229910002804 graphite Inorganic materials 0.000 abstract description 28
- 239000010439 graphite Substances 0.000 abstract description 28
- 239000000843 powder Substances 0.000 abstract description 17
- 238000005087 graphitization Methods 0.000 abstract description 6
- 238000002425 crystallisation Methods 0.000 abstract description 5
- 230000008025 crystallization Effects 0.000 abstract description 5
- 239000007789 gas Substances 0.000 description 88
- 239000010410 layer Substances 0.000 description 16
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 239000002994 raw material Substances 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 230000006698 induction Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000010453 quartz Substances 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 5
- 229910052786 argon Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000011049 filling Methods 0.000 description 2
- RWSOTUBLDIXVET-UHFFFAOYSA-M hydrosulfide Chemical compound [SH-] RWSOTUBLDIXVET-UHFFFAOYSA-M 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000007781 pre-processing Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 150000001722 carbon compounds Chemical class 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000009770 conventional sintering Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- UNASZPQZIFZUSI-UHFFFAOYSA-N methylidyneniobium Chemical compound [Nb]#C UNASZPQZIFZUSI-UHFFFAOYSA-N 0.000 description 1
- NFFIWVVINABMKP-UHFFFAOYSA-N methylidynetantalum Chemical compound [Ta]#C NFFIWVVINABMKP-UHFFFAOYSA-N 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- 239000004482 other powder Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000000859 sublimation Methods 0.000 description 1
- 230000008022 sublimation Effects 0.000 description 1
- 229910003468 tantalcarbide Inorganic materials 0.000 description 1
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 description 1
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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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/90—Carbides
- C01B32/914—Carbides of single elements
- C01B32/956—Silicon carbide
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The application discloses a silicon carbide pretreatment method and a silicon carbide pretreatment device, and relates to the technical field of silicon carbide treatment. The silicon carbide pretreatment method comprises the step of sintering silicon carbide powder in mixed gas containing carbon-containing gas and silicon-containing gas. During sintering, part of carbon and silicon in the mixed gas are crystallized on the surface of the silicon carbide powder, namely, the silicon carbide is condensed. The crystallization ensures that the silicon carbide powder is more compact and is not easy to collapse; and the particles of the silicon carbide powder can be connected together, and the whole powder has better structural stability. The pretreatment method can also inhibit graphitization of the silicon carbide powder and reduce generation of graphite particles. Therefore, the pretreatment method can reduce the carbon wrapping phenomenon caused by the floating of graphite particles in the subsequent growth process of the silicon carbide crystal, thereby improving the quality of the silicon carbide crystal. The silicon carbide pretreatment device is used for realizing the silicon carbide pretreatment method.
Description
Technical Field
The application relates to the technical field of silicon carbide treatment, in particular to a silicon carbide pretreatment method and device.
Background
The silicon carbide as the third generation semiconductor material has obviously better performance than the first two generations semiconductor materials (silicon, germanium, gallium arsenide and the like) in the micro-electronic fields of high power, high temperature, high frequency, radiation resistance and the like and the short wavelength light electronic field. Physical Vapor Transport (PVT) is currently the most developed method for growing silicon carbide crystals and is also the mainstream method currently applied in industrial production. During crystal growth, high purity silicon carbide sublimes into a gas and diffuses to the surface of the seed crystal, and then crystallizes. However, in the existing process, fine graphite particles are easily brought to the crystal growth surface along with the gas flow in the growth process of the silicon carbide crystal, so that carbon is wrapped in the crystal to reduce the quality. In the related technology, a sintering method is adopted to pretreat a silicon carbide raw material so as to reduce floating graphite particles in the subsequent silicon carbide crystal growth process and improve the quality of the silicon carbide crystal, but the effect is still not good enough and the phenomenon of carbon wrapping is still easy to occur.
In view of this, the present application is specifically proposed.
Disclosure of Invention
The application aims to provide a silicon carbide pretreatment method and a silicon carbide pretreatment device, which can reduce the floating phenomenon of graphite particles in the growth process of a silicon carbide crystal, thereby reducing the carbon wrapping of the silicon carbide crystal and improving the quality of the silicon carbide crystal.
The application is realized as follows:
in a first aspect, the present application provides a silicon carbide pretreatment method comprising:
sintering the silicon carbide powder in a mixed gas containing carbon-containing gas and silicon-containing gas.
In an alternative embodiment, the ratio of the amount of silicon to carbon species in the mixed gas is between 1.01 and 1.20.
In an alternative embodiment, the carbon-containing gas is a hydrocarbon and the silicon-containing gas is a hydrosulfide.
In an alternative embodiment, the carbon-containing gas is methane and the silicon-containing gas is monosilane.
In an alternative embodiment, the step of sintering the silicon carbide powder is performed in a heating space having opposite high and low temperature ends, the silicon carbide powder being stacked at the low temperature end of the heating space.
In an alternative embodiment, the lower end of the heating space is a low temperature end and the upper end of the heating space is a high temperature end.
In an alternative embodiment, the temperature difference between the high temperature end and the low temperature end is 50 to 150 ℃.
In an alternative embodiment, the temperature in the heating space is between 2100 ℃ and 2300 ℃.
In an alternative embodiment, the carbon-containing gas and the silicon-containing gas are continuously supplied into the heating space during the step of sintering the silicon carbide powder.
In a second aspect, the application provides a carborundum preprocessing device, carborundum preprocessing device includes the crucible, carbonous air supply and silicon-containing air supply, form the chamber that holds that is used for holding the carborundum powder in the crucible, first air inlet and second air inlet have been seted up on the crucible, the silicon-containing air supply through first air inlet with hold the chamber intercommunication, the carbonous air supply through the second air inlet with hold the chamber intercommunication, the silicon-containing air supply is used for providing the carbonous gas to the intracavity that holds of crucible, the carbonous air supply is used for providing the carbonous gas to the intracavity that holds of crucible.
In an alternative embodiment, the crucible comprises a crucible main body and a cover body, the crucible main body forms an accommodating cavity and an opening opposite to the bottom of the accommodating cavity, the cover body is arranged at the opening of the crucible main body, and the first air inlet and the second air inlet are arranged at the cover body.
In an optional embodiment, the cover body is provided with a first temperature measuring hole, and the bottom of the crucible main body is provided with a second temperature measuring hole.
In an alternative embodiment, the crucible has opposite top and bottom ends, the outer surface of the crucible is covered with a layer of insulation, the thickness of the layer of insulation near the top end of the crucible being greater than the thickness of the layer of insulation near the bottom end of the crucible.
In an alternative embodiment, the silicon carbide pretreatment apparatus further comprises a heating device for heating the crucible.
The application has the following beneficial effects:
the silicon carbide pretreatment method provided by the embodiment of the application comprises the step of sintering silicon carbide powder in mixed gas containing carbon-containing gas and silicon-containing gas. Sintering the silicon carbide powder in the mixed gas containing carbon and silicon, so that a part of carbon and silicon in the mixed gas are crystallized on the surface of the silicon carbide powder, namely, are condensed into silicon carbide. The crystallization occurs among the silicon carbide powder particles, so that the filling effect is achieved, the silicon carbide powder is more compact, and the phenomenon of material collapse (material collapse can cause powder to float and influence the growth quality of crystals) is not easy to occur. Moreover, the crystallization of carbon and silicon in the mixed gas enables the particles of the silicon carbide powder to be bonded together, the powder has better structural stability as a whole, and even if a certain amount of graphite particles appear in the silicon carbide powder, the graphite particles are bonded, so the graphite particles are not easy to float in the subsequent crystal growth process. In addition, in the existing sintering process, the silicon element and the carbon element in the silicon carbide powder are easy to volatilize in a non-stoichiometric ratio (the silicon volatilizes more), so that silicon is lost, and carbon is enriched in the powder to form graphite particles. However, in the embodiment of the present application, since the sintering process is performed in an atmosphere containing silicon, excessive volatilization of silicon in the silicon carbide powder can be suppressed to a certain extent, thereby suppressing graphitization of the silicon carbide powder and reducing generation of graphite particles. Therefore, the carbon coating phenomenon caused by the floating of graphite particles in the subsequent silicon carbide crystal growth process can be radically reduced, and the quality of the silicon carbide crystal is improved. The silicon carbide pretreatment device provided by the embodiment of the application can be used for the silicon carbide pretreatment method.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is a schematic illustration of a silicon carbide pretreatment apparatus for pretreating a silicon carbide powder according to one embodiment of the present disclosure;
FIG. 2 is a schematic view of a lid of a crucible in one embodiment of the present application.
Reference numerals: 100-a crucible; 110-a crucible body; 111-a containment chamber; 112-a second temperature measurement hole; 120-a lid; 121-a first temperature measurement hole; 122 — a first air inlet; 123-a second air inlet; 124-a first conduit; 125-a second conduit; 200-a heat-insulating layer; 300-a heating device; 400-quartz tube; 500-a first thermometer; 600-a second thermometer; 700-silicon carbide powder.
Detailed Description
During the crystal growth using the PVT method, if graphite particles are present or generated in the powder used, the graphite particles may be carried to the surface of the crystal growth with the gas flow, so that carbon coating is generated inside the crystal, and the quality of the crystal is reduced. The raw material for crystal growth is silicon carbide powder, and since C element and Si element are sublimated in a non-stoichiometric ratio in the growth process, namely C and Si are not sublimated in a one-to-one ratio, si is sublimated more. This non-stoichiometric sublimation results in carbon enrichment and hence graphitization of the silicon carbide feedstock, particularly for small particle powders. Before the crystal growth process, the raw material powder is pretreated by using a sintering process, so that a compact powder structure can be obtained, but Si loss and slight graphitization occur to the powder due to non-stoichiometric volatilization of Si and C elements in the sintering process. Therefore, the existing sintering process still generates more graphite particles, which are not beneficial to the growth of subsequent crystals and are easy to generate carbon wrapping, so that the quality of the obtained silicon carbide crystals is reduced.
In order to solve the problem that the quality of crystals obtained by crystal growth in the related art is not high due to carbon wrapping, the embodiment of the application provides a silicon carbide pretreatment method and a silicon carbide pretreatment device, which can be used for pretreating silicon carbide powder and reducing the occurrence of the carbon wrapping phenomenon in the subsequent crystal growth process, so that the quality of the finally obtained silicon carbide crystals is improved.
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The features and properties of the present application are described in further detail below with reference to examples.
The following first describes a silicon carbide pretreatment apparatus provided in the present application. Fig. 1 is a schematic diagram illustrating a silicon carbide pretreatment apparatus for pretreating silicon carbide powder according to an embodiment of the present disclosure. As shown in fig. 1, the silicon carbide pretreatment apparatus provided in the embodiments of the present application includes a heating apparatus 300, a crucible 100, a carbon-containing gas source (not shown), and a silicon-containing gas source (not shown).
The crucible 100 in this embodiment is a high density graphite crucible 100, but in other embodiments, the crucible 100 may be made of other types of materials that do not react with the raw material and are resistant to high temperature. A containing chamber 111 for containing the silicon carbide powder 700 is formed in the crucible 100, and the containing chamber 111 serves as a heating space for heating the silicon carbide powder 700. The crucible 100 is provided with a first gas inlet 122 and a second gas inlet 123, the silicon-containing gas source is communicated with the accommodating cavity 111 through the first gas inlet 122, and the carbon-containing gas source is communicated with the accommodating cavity 111 through the second gas inlet 123. The silicon-containing gas source is used for storing silicon-containing gas and can provide the silicon-containing gas into the containing cavity 111 of the crucible 100; the carbon-containing gas source is used for storing carbon-containing gas and can provide the carbon-containing gas into the accommodating cavity 111 of the crucible 100. Specifically, the silicon-containing gas source and the carbon-containing gas source may be respectively communicated with the first gas inlet 122 and the second gas inlet 123 through a pipeline, and a valve may be disposed on the pipeline to control the on/off of the gas circuit.
FIG. 2 is a schematic view of the lid 120 of the crucible 100 in one embodiment of the present application. As shown in fig. 1 and 2, in the present embodiment, the crucible 100 includes a crucible main body 110 and a cover 120, and the crucible main body 110 forms an accommodation chamber 111 and an opening opposite to the bottom of the accommodation chamber 111. In fig. 1, the crucible 100 is in an upright posture with the opening at the upper end of the accommodating chamber 111 and the bottom of the accommodating chamber 111 at the lower end of the accommodating chamber 111. The lid 120 is disposed at the opening of the crucible body 110, and the first inlet 122 and the second inlet 123 are disposed at the lid 120. Since the first and second gas inlets 122 and 123 are not required to be used in the crystal growth process after the pretreatment process, the first and second gas inlets 122 and 123 are disposed on the cover 120, so that the cover 120 including the first and second gas inlets 122 and 123 can be conveniently replaced with a common cover after the pretreatment process, and the next crystal growth process can be performed without replacing the entire crucible 100.
Specifically, a first conduit 124 is inserted into the first gas inlet 122, and the first conduit 124 is communicated with the silicon-containing gas source; a second conduit 125 is inserted into the second gas inlet 123, and the second conduit 125 is communicated with the carbon-containing gas source. The first and second conduits 124, 125 may optionally be graphite pieces containing metal carbides, such as tantalum carbide, niobium carbide, or tungsten carbide. Switches may be disposed on the first conduit 124 and the second conduit 125 to open and close the air passages.
In this embodiment, the cover 120 has a first temperature measuring hole 121, and the bottom of the crucible body 110 has a second temperature measuring hole 112. In this embodiment, the silicon carbide pretreatment device further includes a first temperature detector 500 and a second temperature detector 600, the first temperature detector 500 can detect the temperature (i.e., the end close to the opening) of the top end of the accommodating cavity 111 through the first temperature measuring hole 121, and the second temperature detector 600 can detect the temperature of the bottom of the accommodating cavity 111 through the second temperature measuring hole 112. Whether the temperature field of the heating space is appropriate can be judged through the temperature information fed back by the first thermometer 500 and the second thermometer 600.
In the present embodiment, the crucible 100 has opposite top and bottom ends, the outer surface of the crucible 100 is covered with the insulating layer 200, and the thickness of the insulating layer 200 near the top end of the crucible 100 is greater than the thickness of the insulating layer 200 near the bottom end of the crucible 100. In the present embodiment, the top end of the crucible 100 is the end provided with the cover 120, and the bottom end of the crucible 100 is the end of the crucible main body 110 away from the cover 120. Specifically, the insulating layer 200 may include one or more layers of insulating carbon felts, and a larger number of layers of insulating carbon felts are disposed at the top end of the crucible 100, and a smaller number of layers of insulating carbon felts are disposed at the bottom end of the crucible 100 (in the figure, the thickness difference of the insulating layer 200 at different positions is not shown), which is beneficial for making the temperature of the lower end of the accommodating cavity 111 lower than that of the upper end, and the lower end of the accommodating cavity 111 forms a low-temperature end of the heating space, so that when the silicon carbide powder 700 is stacked at the lower end of the accommodating cavity 111 for sintering, the carbon-containing gas and the silicon-containing gas tend to crystallize on the silicon carbide powder 700. The thickness of each layer of heat preservation carbon felt can be 5-20 mm.
The heating device 300 is used for heating the crucible 100, and in the present embodiment, the heating device 300 includes an induction coil disposed around the outer circumference of the crucible 100, and the temperature field in the crucible 100 can be adjusted by adjusting the arrangement position and the operating power of the induction coil. In this embodiment, the silicon carbide pretreatment apparatus further includes a quartz tube 400, the crucible 100 is disposed in the quartz tube 400, and the induction coil surrounds the quartz tube 400. When the crucible 100 is heated, a protective atmosphere may be introduced into the quartz tube 400 to reduce oxidation of the crucible 100.
The silicon carbide pretreatment device provided by the embodiment of the application can be used for pretreating silicon carbide powder 700 so as to reduce the occurrence of carbon wrapping phenomenon in the subsequent crystal growth process, and thus high-purity silicon carbide crystals are obtained.
The embodiment of the application also provides a silicon carbide pretreatment method which can be realized by using the silicon carbide pretreatment device provided by the embodiment. The silicon carbide pretreatment method comprises the step of sintering silicon carbide powder in mixed gas containing carbon-containing gas and silicon-containing gas.
Taking the silicon carbide pretreatment device provided in the embodiment of the present application as an example, the silicon carbide powder 700 may be placed in the containing cavity 111 of the crucible 100, and then the carbon-containing gas and the silicon-containing gas are respectively introduced into the crucible 100 by using the carbon-containing gas source and the silicon-containing gas source, and sintering is performed in the atmosphere of the mixed gas containing silicon and carbon. Silicon and carbon in the gas will crystallize into silicon carbide on the silicon carbide powder 700 during sintering. Specifically, the crystals occur on the surface of the particles of the silicon carbide powder 700, and the crystals can fill the gaps of the silicon carbide powder 700, so that the powder is more compact and is not easy to collapse in the subsequent growth process. Meanwhile, silicon and carbon in the gas are crystallized in the silicon carbide powder 700, and particles in the silicon carbide powder 700 can be connected, so that the powder has high structural stability. Even if a certain amount of graphite particles are present in the silicon carbide powder 700, these graphite particles are not easily lifted up because they are bonded to other powder particles, and therefore the graphite particles are not easily lifted up to the crystal surface by the ascending air flow during the crystal growth process, resulting in carbon coating of the crystal. In addition, since silicon exists in the atmosphere at a certain concentration, excessive loss of silicon in the silicon carbide powder 700 is not easily generated during the sintering process, so that graphitization of the powder is also inhibited, and the number of graphite particles during the sintering process is fundamentally reduced.
Further, the ratio of the amount of silicon to the amount of carbon in the mixed gas is 1.01 to 1.20. It should be understood that since the silicon and carbon in the raw materials are easily volatilized in a non-stoichiometric ratio during the sintering process, the silicon is lost more, so that the raw materials are slightly graphitized, and therefore, the content of silicon in the mixed gas is set to be slightly higher than that of carbon in the embodiment, so that the loss of silicon can be better restrained. The ratio of the amounts of silicon to carbon may be adjusted as necessary, and is not limited to the above range.
Optionally, the carbon-containing gas is a hydrocarbon and the silicon-containing gas is a hydrosulfide. In this embodiment, the carbon-containing gas is methane and the silicon-containing gas is monosilane. Since both methane and monosilane contain only one carbon atom or silicon atom in the molecular formula, the volume ratio of methane to monosilane at isothermal and isobaric pressure is the ratio of the amounts of silicon to carbon in the mixed gas. When the amount of carbon and silicon in the molecular formula of the carbon-containing gas and the silicon-containing gas is changed, the volume ratio of the corresponding gases should be adaptively adjusted to ensure the proper ratio of silicon to carbon.
In this embodiment, the step of sintering the silicon carbide powder 700 is performed in a heating space having opposite high-temperature and low-temperature ends, and the silicon carbide powder 700 is stacked at the low-temperature end of the heating space. In the case of using the silicon carbide pretreatment apparatus provided in the above embodiment, the accommodating chamber 111 of the crucible 100 is a heating space, and the heating space exhibits a temperature field with a high upper end temperature and a low lower end temperature by adjusting the position of the induction coil of the heating apparatus 300 and the thickness of the heat insulating layer 200. The temperature range in the heating space can be selected to be 2100-2300 ℃, and the temperature difference between the high temperature end and the low temperature end can be selected to be 50-150 ℃. Since silicon and carbon in the gas are likely to crystallize at the low temperature end, the silicon and carbon in the gas can be ensured to crystallize on the silicon carbide powder 700 by setting the silicon carbide powder 700 at the low temperature end.
Further, in the step of sintering the silicon carbide powder 700, carbon-containing gas and silicon-containing gas are continuously introduced into the heating space, and the ratio of silicon to carbon in the mixed gas is controlled by controlling the flow rate. In the pretreatment of silicon carbide, the receiving cavity 111 of the crucible 100 may be first evacuated to 5 × 10 -2 Below mbar, argon is then introduced to a pressure of from 100 to 800mbar, preferably 200mbar. The crucible 100 is heated to 2100 to 2300 ℃ by the heating device 300, and then the switches of the first conduit 124 and the second conduit 125 are opened to introduce the high-purity carbon-containing gas and silicon-containing gas. Taking the silicon-containing gas as the monosilane and the carbon-containing gas as the methane as the examples, the total flow rate of the mixed gas is 1-20 sccm, and the ratio of the monosilane to the methane is 1.01-1.20. After keeping the conditions for 5 to 10 hours, stopping introducing the silicon-containing gas and the carbon-containing gas, increasing the pressure to 500 to 1000mbar, and rapidly cooling.
In one embodiment, a 20mm thick graphite crucible is loaded with 2.0kg of 5N purity silicon carbide powder 700, compacted and leveled, and the lid 120 is placed. Then, a single layer of 5mm thick insulating carbon felt was wrapped around the crucible 100, 3 layers of 5mm thick insulating carbon felt were used on the top of the crucible 100 and only 2 layers were used on the bottom. The pretreatment of the silicon carbide powder 700 is then started. First, the vacuum pump is started to pump the pressure to 5x10 -2 And introducing high-purity argon to 200mbar below the mbar, heating the crucible 100 through the induction coil, and adjusting the position of the coil to ensure that the detection reading of the first temperature detector 500 is 2150 ℃ and the reading of the second temperature detector 600 is 2100 ℃. Monosilane and methane were then fed in at a total flow rate of 1.5sccm and a gas ratio of monosilane to methane of 1.05. After heating for 6 hours, the introduction of monosilane and methane was stopped, argon was introduced to 500mbar and the temperature was rapidly reduced.
After the pretreatment, the crystal growth was performed using a crucible 100 cover with a seed crystal instead of the cover 120 used in the above pretreatment. The pretreated silicon carbide powder 700 obtained by the silicon carbide pretreatment method has a compact and stable structure and less graphite particles, so that the pretreated powder is used for subsequent crystal growth, and the silicon carbide crystal with less carbon coating can be obtained.
In summary, the method for pretreating silicon carbide provided by the embodiment of the present application includes sintering the silicon carbide powder 700 in a mixed gas containing a carbon-containing gas and a silicon-containing gas. By sintering the silicon carbide powder 700 in a mixed gas containing carbon and silicon, a part of carbon and silicon in the mixed gas is crystallized on the surface of the silicon carbide powder 700, that is, condensed into silicon carbide. The crystallization occurs among the silicon carbide powder 700 particles, so that the filling effect is achieved, the silicon carbide powder 700 is more compact, and the phenomenon of collapse is not easy to occur (the collapse can cause the powder to float, and the crystal growth quality is influenced). Moreover, the crystallization of carbon and silicon in the mixed gas enables the particles of the silicon carbide powder 700 to be bonded together, the powder has a good structural stability as a whole, and even if a certain amount of graphite particles appear in the silicon carbide powder 700, the graphite particles are not easy to float up in the subsequent crystal growth process because of the bonding of the graphite particles. In addition, in the conventional sintering process, the silicon element and the carbon element in the silicon carbide powder 700 are easily volatilized in a non-stoichiometric ratio (the silicon is volatilized more), so that the silicon is lost, and the carbon is enriched in the powder to form graphite particles. However, in the embodiment of the present application, since the sintering process is performed in an atmosphere containing silicon, excessive volatilization of silicon in the silicon carbide powder 700 can be suppressed to a certain extent, thereby suppressing graphitization of the silicon carbide powder 700 and reducing generation of graphite particles. Therefore, the carbon coating phenomenon caused by the floating of graphite particles in the subsequent silicon carbide crystal growth process can be radically reduced, and the quality of the silicon carbide crystal is improved. The silicon carbide pretreatment device provided by the embodiment of the application can be used for the silicon carbide pretreatment method.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (14)
1. A method of pretreating silicon carbide, comprising:
sintering the silicon carbide powder in a mixed gas containing carbon-containing gas and silicon-containing gas.
2. The method of pretreating silicon carbide according to claim 1, wherein the amount of silicon to carbon in the mixed gas is 1.01 to 1.20.
3. The silicon carbide pretreatment method according to claim 1, wherein the carbon-containing gas is a hydrocarbon and the silicon-containing gas is a hydrosilicon compound.
4. The silicon carbide pretreatment method according to claim 3, wherein the carbon-containing gas is methane and the silicon-containing gas is monosilane.
5. The silicon carbide pretreatment method according to any one of claims 1 to 4, wherein the step of sintering the silicon carbide powder is performed in a heating space having opposite high-temperature and low-temperature ends, and the silicon carbide powder is stacked on the low-temperature end of the heating space.
6. The silicon carbide pretreatment method according to claim 5, wherein a lower end of the heating space is a low temperature end, and an upper end of the heating space is a high temperature end.
7. The silicon carbide pretreatment method according to claim 5, wherein a temperature difference between the high temperature side and the low temperature side is 50 to 150 ℃.
8. The silicon carbide pretreatment method according to claim 5, wherein the temperature in the heating space is 2100 to 2300 ℃.
9. The method of pretreating silicon carbide according to claim 5, wherein the carbon-containing gas and the silicon-containing gas are continuously supplied into the heating space during the step of sintering the silicon carbide powder.
10. The silicon carbide pretreatment device is characterized by comprising a crucible, a carbon-containing gas source and a silicon-containing gas source, wherein a containing cavity for containing silicon carbide powder is formed in the crucible, a first gas inlet and a second gas inlet are formed in the crucible, the silicon-containing gas source is communicated with the containing cavity through the first gas inlet, the carbon-containing gas source is communicated with the containing cavity through the second gas inlet, the silicon-containing gas source is used for providing a silicon-containing gas into the containing cavity of the crucible, and the carbon-containing gas source is used for providing a carbon-containing gas into the containing cavity of the crucible.
11. The silicon carbide pretreatment apparatus according to claim 10, wherein the crucible includes a crucible main body and a lid body, the crucible main body forms the accommodation chamber and an opening opposite to a bottom of the accommodation chamber, the lid body is provided to the opening of the crucible main body, and the first gas inlet and the second gas inlet are provided to the lid body.
12. The silicon carbide pretreatment device according to claim 11, wherein the lid body has a first temperature measurement hole, and the bottom of the crucible main body has a second temperature measurement hole.
13. The silicon carbide pretreatment apparatus of claim 10, wherein the crucible has opposing top and bottom ends, an outer surface of the crucible is covered with a layer of insulation, and the layer of insulation adjacent the top end of the crucible has a thickness greater than the layer of insulation adjacent the bottom end of the crucible.
14. The silicon carbide pretreatment apparatus of claim 10, further comprising a heating device for heating the crucible.
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