CN114182348B - Preparation method of silicon carbide single crystal with reduced carbon coating - Google Patents
Preparation method of silicon carbide single crystal with reduced carbon coating Download PDFInfo
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- CN114182348B CN114182348B CN202111264650.3A CN202111264650A CN114182348B CN 114182348 B CN114182348 B CN 114182348B CN 202111264650 A CN202111264650 A CN 202111264650A CN 114182348 B CN114182348 B CN 114182348B
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- 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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- 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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Abstract
The invention relates to the technical field of crystal preparation, and discloses a preparation method of silicon carbide single crystals with reduced carbon wrapping, which at least comprises the steps of loading and crystal growth, wherein the loading step comprises the following steps: adding silicon carbide powder and oxide into a crystal growth container, wherein the oxide is silicon dioxide and/or cerium dioxide; wherein the silicon carbide powder and the oxide form a pack reaction structure, a stack reaction structure, or a composite reaction structure in the growth vessel; the coating reaction structure comprises a silicon dioxide layer and a silicon carbide powder layer coated outside the silicon dioxide layer; the laminated reaction structure comprises a silicon carbide powder layer and a cerium oxide layer, wherein a separator is arranged between the cerium oxide layer and the silicon carbide powder layer and is not in direct contact with the silicon carbide powder layer; the composite reaction structure comprises a silicon dioxide layer, a silicon carbide powder layer and a cerium dioxide layer, wherein the silicon carbide powder layer is wrapped outside the silicon dioxide layer, and a separator is arranged between the cerium dioxide layer and the silicon carbide powder layer and is not in direct contact. The method can effectively reduce the graphitization degree of the silicon carbide crystal.
Description
Technical Field
The invention relates to the technical field of preparation of silicon carbide crystals, in particular to a preparation method of a silicon carbide single crystal with reduced carbon wrapping.
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, optoelectronic devices and the like because of the excellent performances of large forbidden band width, high saturated electron mobility, strong breakdown field, high thermal conductivity and the like. The Physical Vapor Transport (PVT) method is the main growth technology for producing silicon carbide single crystals, namely, the method is realized by transporting a vapor source generated by sublimating silicon carbide raw materials to a seed crystal at high temperature for recrystallization.
The growth process of growing a silicon carbide single crystal by the PVT method is carried out in a closed graphite crucible, so that the growth environment is in a carbon-rich atmosphere at a high temperature. In the early stage of crystal growth, the crystal growth interface is in a state in which the silicon component and the carbon component are relatively balanced because of the high vapor partial pressure of the silicon component. As crystal growth proceeds, the silicon component of the silicon carbide feedstock continually sublimates less, resulting in a gradual imbalance of gas phase components within the growth chamber into a carbon-rich state. In a carbon-rich growth environment, the front interface of crystal growth has carbon enrichment and carbon inclusion defects. Inclusion defects can induce defects such as micropipes, dislocations, faults and the like, seriously affect the quality of the silicon carbide substrate, and further affect the quality of an epitaxial layer and the performance of a device.
To eliminate the carbon inclusion defect existing in the silicon carbide crystal, wang Fengfu of the university of western union, etc. a small crucible containing a silicon-rich raw material is added to the original long-crystal crucible to desirably serve as a supplemental source of silicon components during the crystal growth process, thereby reducing the formation of the carbon-rich components and further suppressing the formation of carbon inclusions [ Wang Fengfu ]. The influence of the quality of SiC crystals of Si powder incorporated in the raw material [ D ]. University of western union, 2013 ]. The method can not flexibly control the sublimation time of the silicon in the small crucible, and can possibly cause the advanced sublimation or the delayed sublimation of the silicon, and the advanced sublimation of the silicon can cause the excessive silicon atmosphere in the growth cavity, thereby easily forming the defects of silicon inclusion, microtubes and the like; silicon lag sublimation does not act to inhibit carbon inclusion.
CN105671637a and CN205653539U disclose a slow-release device for growing silicon carbide single crystal by PVT method, a partition plate is arranged in the crucible, the partition plate divides the silicon carbide powder source into an upper layer and a lower layer, and a plurality of holes communicated with the upper layer and the lower layer of silicon carbide powder source are arranged on the partition plate. CN207062351U discloses a vacuum furnace for two-stage distillation, wherein a crucible I and a crucible II are communicated through an air duct, a temperature control heating member I is connected with the crucible I, a temperature control heating member II is connected with the crucible II, a thermocouple I is arranged in the crucible I, and a thermocouple II is arranged in the crucible II to respectively heat the two crucibles and realize twice vacuum distillation of metal materials. The above patent documents have unsatisfactory control effect on the loss of silicon element in the process of growing monocrystalline silicon carbide, and the control is not accurate enough.
Disclosure of Invention
The invention aims to solve the problem that the silicon carbide long crystal condition is difficult to control in the prior art, and provides a preparation method for reducing carbon-coated silicon carbide single crystals.
In order to achieve the above object, the present invention provides a method for producing a silicon carbide single crystal reduced in carbon encapsulation, the method comprising at least the steps of charging and growing the crystal, the charging step comprising: adding silicon carbide powder and oxide into a crystal growth container, wherein the oxide is silicon dioxide and/or cerium dioxide;
wherein the silicon carbide powder and the oxide are caused to form a pack reaction structure, a stack reaction structure, or a composite reaction structure in the growth vessel; the coating reaction structure comprises a silicon dioxide layer and a silicon carbide powder layer coated outside the silicon dioxide layer; the laminated reaction structure comprises a silicon carbide powder layer and a cerium oxide layer laminated on the silicon carbide powder layer, wherein a separator is arranged between the cerium oxide layer and the silicon carbide powder layer and is not in direct contact; the composite reaction structure comprises a silicon dioxide layer, a silicon carbide powder layer wrapped outside the silicon dioxide layer and a cerium oxide layer which is arranged on the silicon carbide powder layer in a laminated mode, wherein a separator is arranged between the cerium oxide layer and the silicon carbide powder layer and is not in direct contact.
Preferably, the molar ratio of the silicon carbide powder to the oxide is 20 to 500:1.
preferably, the preparation method further comprises preheating the silicon carbide powder.
Further preferably, the conditions of the preheating treatment include: the temperature is 200-400 ℃ and the time is 0.5-1h.
Preferably, the particle size of the oxide is smaller than the particle size of the silicon carbide powder.
Preferably, the oxide is silica.
Preferably, in the encapsulation reaction structure or the composite reaction structure, the silicon carbide powder layer includes a first silicon carbide powder layer, a second silicon carbide powder layer, and a third silicon carbide powder layer that are stacked, the second silicon carbide powder layer has a hole formed thereon that is suitable for filling the silicon dioxide layer, and a thickness ratio of the first silicon carbide powder layer, the silicon dioxide layer, and the third silicon carbide powder layer is 1:2-4:1-2.
Further preferably, the projected area of the second silicon carbide powder layer in the direction in which the first silicon carbide powder layer, the second silicon carbide powder layer, and the third silicon carbide powder layer are arranged is 1.5 to 2 times the projected area of the silicon dioxide layer in that direction.
Preferably, when the oxide contains ceria, the ceria is placed in a tantalum crucible as the separator placed on the silicon carbide powder.
Further preferably, the volume ratio of the tantalum crucible and the growth vessel is 1:50-100.
Preferably, the conditions for growing the crystal include: under argon atmosphere, the temperature is 2100-2250 ℃ and the pressure is 300-500Pa.
According to the technical scheme, the silicon dioxide and/or the cerium dioxide are added into the crystal growth container, the silicon carbide powder is wrapped outside the silicon dioxide, and/or the cerium dioxide is arranged on the surface of the silicon carbide powder and is not in direct contact with the silicon carbide powder, so that the excessive carbon content can be effectively absorbed when the carbon content is excessive in the crystal growth process, the deposition of solid carbon particles on a growth interface is reduced, the graphitization degree of the obtained silicon carbide crystal is reduced, and the structural defects caused by carbon wrapping in the crystal growth process are reduced. And the mode of adding silicon dioxide and/or cerium oxide has less operation difficulty and is easy to control.
Drawings
FIG. 1 is a schematic structural view of a package reaction structure according to an embodiment of the present invention;
FIG. 2 is a schematic structural view of a packaging reaction structure according to another embodiment of the present invention;
FIG. 3 is a schematic structural view of a laminated reaction structure according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a composite reaction structure according to an embodiment of the present invention.
Description of the reference numerals
1 a silicon carbide powder layer; 2 a silicon dioxide layer; 3 a cerium oxide layer;
11 a first silicon carbide powder layer; a second silicon carbide powder layer; and 13 a third silicon carbide powder layer.
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
As described above, the present invention provides a method for producing a silicon carbide single crystal reduced in carbon encapsulation, the method comprising at least the steps of charging and growing the crystal, the charging step comprising: adding silicon carbide powder and oxide into a crystal growth container, wherein the oxide is silicon dioxide and/or cerium dioxide; wherein the silicon carbide powder and the oxide form a pack reaction structure, a stack reaction structure, or a composite reaction structure in the growth vessel; the coating reaction structure comprises a silicon dioxide layer 2 and a silicon carbide powder layer 1 coated outside the silicon dioxide layer 2; the laminated reaction structure comprises a silicon carbide powder layer 1 and a cerium oxide layer 3 laminated on the silicon carbide powder layer 1, wherein a separator is arranged between the cerium oxide layer 3 and the silicon carbide powder layer 1 and is not in direct contact; the composite reaction structure comprises a silicon dioxide layer 2, a silicon carbide powder layer 1 wrapped outside the silicon dioxide layer 2 and a cerium oxide layer 3 laminated on the silicon carbide powder layer 1, wherein a separator is arranged between the cerium oxide layer 3 and the silicon carbide powder layer 1 and is not in direct contact.
According to the present invention, the condition of growing the crystal may be a growing condition disclosed in the prior art, and the crystal growing container may be any container disclosed in the prior art that can be used in the preparation of silicon carbide crystals, such as a graphite crucible, a tantalum carbide crucible, or a tantalum crucible of different types. The silicon carbide powder layer 1, the silicon dioxide layer 2 and the cerium oxide layer 3 may have a regular or irregular layered structure, and may or may not have a cross-sectional shape corresponding to that of the long-crystal container, preferably, the long-crystal container, and may be more easily molded. The thicknesses of the silicon carbide powder layer 1, the silicon dioxide layer 2 and the cerium oxide layer 3 may be uniform or non-uniform, and preferably uniform, so that the reaction between carbon left during sublimation of the silicon carbide powder layer 1 and the silicon dioxide layer 2 and the reaction between carbon left during sublimation of the silicon carbide powder layer 1 and the cerium oxide layer 3 are more sufficient.
As one embodiment of the present invention, a packing reaction structure, a lamination reaction structure, or a composite reaction structure of silicon carbide powder and oxide formed in a growth vessel is shown in fig. 1 to 4. Wherein FIG. 1 is a specific embodiment of a wrap reaction structure; FIG. 2 is another embodiment of a packaging reaction structure; fig. 3 is a specific embodiment of a laminated reaction structure, and a structure between the silicon carbide powder layer 1 and the ceria layer 3 refers to a separator; FIG. 4 is a schematic representation of an embodiment of a composite reaction structure. Of course, the above-described fig. 1-4 are only one specific embodiment of the encapsulation reaction structure, the lamination reaction structure, or the composite reaction structure, and are not intended to limit the encapsulation reaction structure, the lamination reaction structure, or the composite reaction structure.
The above-mentioned encapsulation reaction structure, lamination reaction structure and composite reaction structure may be formed in any feasible manner. As a molding mode of the package reaction structure, the invention comprises the following steps: firstly paving a layer of silicon carbide powder in a crystal growth container, then paving a layer of silicon dioxide at the middle position of the silicon carbide powder, wherein the paving area of the silicon carbide powder is smaller than the paving area of the silicon carbide powder, and then paving the silicon carbide powder on the periphery of the silicon dioxide and the silicon dioxide so as to enable the silicon carbide powder to wrap the silicon dioxide. One molding method of the laminated reaction structure according to the present invention includes the steps of: silicon carbide powder is laid inside a growth container, and then a separator with cerium oxide placed thereon is placed on the silicon carbide powder to form a stacked reaction structure. As a forming mode of the composite reaction structure, the method comprises the following reaction steps: firstly, paving a layer of silicon carbide powder in a crystal growth container, then paving a layer of silicon dioxide at the middle position of the silicon carbide powder, wherein the paving area of the silicon carbide powder is smaller than the paving area of the silicon carbide powder, then paving the silicon carbide powder on the periphery of the silicon dioxide and the silicon dioxide so as to enable the silicon carbide powder to wrap the silicon dioxide, and finally, placing a separator with cerium oxide on the finally paved silicon carbide powder.
Preferably, after the completion of the charging, the distance of the top of the silicon carbide powder from the top of the long crystal container is ensured to be 10-20mm to improve the quality of the formed silicon carbide crystal. In the description of the embodiment of the present invention, the distance from the top of the silicon carbide powder to the top of the long crystal container was 10mm.
The inventor finds that adding silicon dioxide and/or cerium dioxide in the preparation process of the silicon carbide single crystal, wrapping silicon carbide powder outside the silicon dioxide, and isolating the cerium dioxide on the silicon carbide powder through a separator, so that the silicon dioxide and/or cerium dioxide can react with carbon left in the sublimation process of the silicon carbide (the silicon dioxide directly reacts with the carbon left in the silicon carbide powder, and the cerium dioxide reacts with the carbon which falls off due to non-reaction in the ascending air flow), thereby reducing the graphitization degree of the prepared silicon carbide single crystal and reducing the structural defects formed by carbon wrapping in the formation process of the silicon carbide; it is also possible to prevent cerium oxide from directly contacting silicon carbide to leave metallic cerium, which may be a product, on silicon carbide, thus causing problems of crucible metal contamination and difficult recovery of raw materials. And the operation difficulty in the preparation process of the silicon carbide crystal can be effectively reduced by adding silicon dioxide and/or cerium dioxide, the reaction is easier to control, and the air flow does not need to be regulated at any time.
In order to be able to further reduce the graphitization degree of the produced silicon carbide single crystal, it is preferable that the molar ratio of the silicon carbide powder to the oxide is 20 to 500:1. research shows that under the preferred proportion, the graphitization degree of the prepared silicon carbide single crystal can be effectively reduced, the problem of oxide carry-over after reaction can be prevented, and the utilization rate of silicon carbide powder and oxide is provided.
In order to further reduce the graphitization degree of the produced silicon carbide crystal and prevent the influence of impurities thereon, it is preferable that the purities of both silica and ceria are 4N or more and the purity of the silicon carbide powder is 5N or more. Specifically, the purity of the silicon dioxide is greater than or equal to 99.99%, the purity of the cerium dioxide is greater than or equal to 99.99%, and the purity of the silicon carbide powder is greater than or equal to 99.999%.
Preferably, the preparation method further comprises preheating the silicon carbide powder. The method can remove water vapor absorbed in the silicon carbide powder and organic pollution possibly occurring in the silicon carbide powder through heat treatment, so that the purity of the silicon carbide powder is further improved, the influence of the water vapor and the organic pollution on the crystal form of the silicon carbide is further prevented, and the graphitization degree of the prepared silicon carbide crystal is further reduced. Preferably, the conditions of the preheating treatment include: the temperature is 200-400 ℃ and the time is 0.5-1h. The method can effectively remove water vapor and organic pollution of the silicon carbide powder under the preferred conditions, and further reduce the graphitization degree of the prepared silicon carbide crystal.
The solid oxide and the silicon carbide powder are both in powder form, preferably the particle size of the oxide is smaller than the particle size of the silicon carbide powder. The preferable conditions can further reduce the graphitization degree of the produced silicon carbide single crystal.
Preferably, the oxide is silica. That is, the oxide is silica, or the oxide is silica and ceria. The presence of silica can significantly reduce the graphitization degree of the produced silicon carbide single crystal. Further preferably, the oxides are silica and ceria, the silica and ceria having a molar ratio of 10 to 50:1.
preferably, in the encapsulation reaction structure or the composite reaction structure, the silicon carbide powder layer 1 includes a first silicon carbide powder layer 11, a second silicon carbide powder layer 12, and a third silicon carbide powder layer 13 that are stacked, the second silicon carbide powder layer 12 has a hole formed thereon that is adapted to fill the silicon dioxide layer 2, and the thickness ratio of the first silicon carbide powder layer 11, the silicon dioxide layer 2, and the third silicon carbide powder layer 13 is 1:2-4:1-2. Studies have shown that at this preferred thickness ratio, silica is able to react sufficiently with carbon left over from sublimation, thereby further reducing the degree of graphitization of the resulting silicon carbide crystals. Fig. 2 and 4 are two of the schematic structural views of this embodiment.
Specifically, the first silicon carbide powder layer 11, the second silicon carbide powder layer 12, and the third silicon carbide powder layer 13 are all uniform in thickness, and the second silicon carbide powder layer 12 and the silicon dioxide layer 2 are uniform in thickness. The thickness thereof can be made uniform by any of the means disclosed in the prior art. Preferably, the pavement is continuously scraped in the paving process, so that the thickness of the pavement is uniform.
It is further preferable that the projected area of the second silicon carbide powder layer 12 in the direction z in which the first silicon carbide powder layer 11, the second silicon carbide powder layer 12, and the third silicon carbide powder layer 13 are arranged is 1.5 to 2 times the projected area of the silicon dioxide layer 2 in that direction. Experiments prove that the graphitization degree of the prepared silicon carbide crystal can be further reduced under the condition of the preferable projection area. Fig. 2 and 4 are two of the schematic structural views of this embodiment.
The separator may be a conventional metal vessel or graphite vessel that does not react with ceria at high temperatures, preferably when the oxide contains ceria, the ceria is placed in a tantalum crucible as the separator placed on the silicon carbide powder. The tantalum crucible is adopted to prevent the elemental cerium generated by the reaction from polluting the crystal growth container, and the tantalum crucible can further absorb carbon remained in the recovery process, so that the graphitization degree of the prepared silicon carbide single crystal is further reduced. But also can be used for multiple times, and the preparation cost of the silicon carbide crystal is reduced.
In order to further reduce the graphitization degree of the produced silicon carbide single crystal and prevent the excessive volume of the tantalum crucible from affecting the growth of silicon carbide, the volume ratio of the tantalum crucible to the growth container is preferably 1:50-100.
Preferably, the conditions for growing the crystal include: under argon atmosphere, the temperature is 2100-2250 ℃ and the pressure is 300-500Pa. The research proves that the silicon carbide crystal obtained under the condition has lower graphitization degree and better crystal form.
The time for the crystal growth may be specifically defined by those skilled in the art depending on the amount of silicon carbide added.
According to a particularly preferred embodiment of the present invention, there is provided a method for producing a silicon carbide single crystal reduced in carbon encapsulation, the method comprising at least the steps of preheating, charging and growing the crystal, the step of preheating comprising: the silicon carbide powder is subjected to preheating treatment, and the conditions of the preheating treatment comprise: the temperature is 200-400 ℃ and the time is 0.5-1h; the charging step comprises the following steps: adding silicon carbide powder and oxide into a crystal growth container, wherein the oxide is silicon dioxide and/or cerium dioxide, the purity of the silicon dioxide and the cerium dioxide is 4N or more, the purity of the silicon carbide powder is 5N or more, the particle size of the oxide is smaller than that of the silicon carbide powder, and the mole ratio of the silicon carbide powder to the oxide is 20-500:1, a step of; wherein the silicon carbide powder and the oxide form a pack reaction structure, a stack reaction structure, or a composite reaction structure in the growth vessel; the coating reaction structure comprises a silicon dioxide layer 2 and a silicon carbide powder layer 1 coated outside the silicon dioxide layer 2, wherein the silicon carbide powder layer 1 comprises a first silicon carbide powder layer 11, a second silicon carbide powder layer 12 and a third silicon carbide powder layer 13 which are stacked, holes suitable for filling the silicon dioxide layer 2 are formed in the second silicon carbide powder layer 12, and the thickness ratio of the first silicon carbide powder layer 11 to the silicon dioxide layer 2 to the third silicon carbide powder layer 13 is 1:2-4:1-2, the projected area of the second silicon carbide powder layer 12 in the direction z in which the first silicon carbide powder layer 11, the second silicon carbide powder layer 12 and the third silicon carbide powder layer 13 are arranged is 1.5-2 times the projected area of the silicon dioxide layer 2 in that direction, fig. 2 being a schematic structural view thereof; the laminated reaction structure comprises a silicon carbide powder layer 1 and a cerium oxide layer 3 laminated on the silicon carbide powder layer 1, wherein a tantalum crucible serving as a separator is arranged between the cerium oxide layer 3 and the silicon carbide powder layer 1 and is not in direct contact with the silicon carbide powder layer 1, the volume ratio of the tantalum crucible to a crystal growth container is 1:50-100, and fig. 3 is taken as a schematic structural diagram thereof; the composite reaction structure comprises a silicon dioxide layer 2, a silicon carbide powder layer 1 wrapped outside the silicon dioxide layer 2 and a cerium dioxide layer 3 stacked on the silicon carbide powder layer 1, wherein a tantalum crucible serving as a separator is arranged between the cerium dioxide layer 3 and the silicon carbide powder layer 1 and is not in direct contact with the silicon carbide powder layer 1, the volume ratio of the tantalum crucible to a long crystal container is 1:50-100, the silicon carbide powder layer 1 comprises a first silicon carbide powder layer 11, a second silicon carbide powder layer 12 and a third silicon carbide powder layer 13 stacked, holes suitable for filling the silicon dioxide layer 2 are formed on the second silicon carbide powder layer 12, the silicon dioxide layer 2 is filled in the holes, and the thickness ratio of the first silicon carbide powder layer 11, the silicon dioxide layer 2 and the third silicon carbide powder layer 13 is 1:2-4:1-2, the projected area of the second silicon carbide powder layer 12 in the direction z in which the first silicon carbide powder layer 11, the second silicon carbide powder layer 12 and the third silicon carbide powder layer 13 are arranged is 1.5-2 times the projected area of the silicon dioxide layer 2 in that direction, fig. 4 being a schematic structural view thereof; the conditions for growing the crystal include: under argon atmosphere, the temperature is 2100-2250 ℃ and the pressure is 300-500Pa.
The present invention will be described in detail by examples. In the following examples, the graphitization degree is obtained by measuring the carbon content of the residual silicon carbide powder after growth in unit mass, the carbon inclusion concentration is measured by a laser scattering detection method, and the graphitization degree is obtained by cs-920 equipment test; the silicon carbide powder is purchased from Shanxi scintillant company, the product model is conductive silicon carbide powder, the purity is 99.999%, and the grain size is 40-80 meshes; silica is purchased from sigma with a purity of 99.99% and a particle size of 150-300 microns; ceria was purchased from sigma with 99.99% purity and particle size of 100-200 microns.
Example 1
(1) The silicon carbide powder was preheated at 300℃for 0.75h.
(2) Adding silicon carbide powder, silicon dioxide and cerium dioxide in the step (1) into a graphite crucible, wherein the molar ratio of the silicon carbide powder to the silicon dioxide to the cerium dioxide is 2100:20:1 (3 kg of silicon carbide powder), the distance from the top of the silicon carbide powder to the top of the graphite crucible being 20mm; wherein silicon carbide powder, silicon dioxide and cerium oxide are caused to form a composite reaction structure in a graphite crucible, see fig. 4, the composite reaction structure comprising a silicon dioxide layer 2, a silicon carbide powder layer 1 wrapped outside the silicon dioxide layer 2, and a cerium dioxide layer 3 laminated on the silicon carbide powder layer 1, the cerium dioxide layer 3 being placed in a tantalum crucible as a separator and placed in a central position of the silicon carbide powder layer 11, the volume ratio of the tantalum crucible to the graphite crucible being 1:150, the silicon carbide powder layer 1 comprising a first silicon carbide powder layer 11, a second silicon carbide powder layer 12 and a third silicon carbide powder layer 13 laminated, a hole adapted to be filled with the silicon dioxide layer 2 being formed in the second silicon carbide powder layer 12, the silicon dioxide layer 2 being filled in the hole, the thickness of each of the first silicon carbide powder layer 11, the second silicon carbide powder layer 12, the third silicon carbide powder layer 13 and the silicon dioxide layer 2 being uniform, and the thickness of the silicon dioxide layer 2 being in accordance with the thickness of the second silicon carbide powder layer 12, the thickness ratio of the first silicon carbide powder layer 11, the silicon dioxide layer 2 and the third silicon carbide powder layer 13 being 1:2:1, the projected area of the second silicon carbide powder layer 12 in the z direction is 1.75 times of the projected area of the silicon dioxide layer 2 in the z direction, a graphite crucible upper cover is covered, and a silicon carbide seed crystal is fixed on the inner side of the graphite crucible upper cover.
(3) The graphite crucible is placed in an argon atmosphere, and the crystal is grown for 120 hours under the conditions that the temperature is 2200 ℃ and the pressure is 400 Pa.
Example 2
(1) The silicon carbide powder was preheated at 200℃for 1h.
(2) Adding silicon carbide powder, silicon dioxide and cerium dioxide in the step (1) into a graphite crucible, wherein the molar ratio of the silicon carbide powder to the silicon dioxide to the cerium dioxide is 3100:30:1 (3 kg of silicon carbide powder), the distance from the top of the silicon carbide powder to the top of the graphite crucible being 20mm; wherein silicon carbide powder, silicon dioxide and cerium oxide are caused to form a composite reaction structure in a graphite crucible, see fig. 4, the composite reaction structure comprising a silicon dioxide layer 2, a silicon carbide powder layer 1 wrapped outside the silicon dioxide layer 2, and a cerium dioxide layer 3 laminated on the silicon carbide powder layer 1, the cerium dioxide layer 3 being placed in a tantalum crucible as a separator and placed in a central position of the silicon carbide powder layer 11, the volume ratio of the tantalum crucible to the graphite crucible being 1:100, the silicon carbide powder layer 1 comprising a first silicon carbide powder layer 11, a second silicon carbide powder layer 12 and a third silicon carbide powder layer 13 laminated, a hole adapted to be filled with the silicon dioxide layer 2 being formed in the second silicon carbide powder layer 12, the silicon dioxide layer 2 being filled in the hole, the thickness of each of the first silicon carbide powder layer 11, the second silicon carbide powder layer 12, the third silicon carbide powder layer 13 and the silicon dioxide layer 2 being uniform, and the thickness of the silicon dioxide layer 2 being in accordance with the thickness of the second silicon carbide powder layer 12, the thickness ratio of the first silicon carbide powder layer 11, the silicon dioxide layer 2 and the third silicon carbide powder layer 13 being 1:2:1, the projected area of the second silicon carbide powder layer 12 in the z direction is 1.5 times of the projected area of the silicon dioxide layer 2 in the z direction, a graphite crucible upper cover is covered, and a silicon carbide seed crystal is fixed on the inner side of the graphite crucible upper cover.
(3) The graphite crucible is placed in an argon atmosphere, and the crystal is grown for 120 hours under the conditions that the temperature is 2100 ℃ and the pressure is 500Pa.
Example 3
(1) The silicon carbide powder was preheated at 400℃for 0.5h.
(2) Adding the silicon carbide powder, the silicon dioxide and the cerium oxide in the step (1) into a graphite crucible, wherein the molar ratio of the silicon carbide powder, the silicon dioxide and the cerium oxide is 1890:20:1 (3 kg of silicon carbide powder), the distance from the top of the silicon carbide powder to the top of the graphite crucible being 20mm; wherein silicon carbide powder, silicon dioxide and cerium oxide are caused to form a composite reaction structure in a graphite crucible, see fig. 4, the composite reaction structure comprising a silicon dioxide layer 2, a silicon carbide powder layer 1 wrapped outside the silicon dioxide layer 2, and a cerium dioxide layer 3 laminated on the silicon carbide powder layer 1, the cerium dioxide layer 3 being placed in a tantalum crucible as a separator and placed in a central position of the silicon carbide powder layer 11, the volume ratio of the tantalum crucible to the graphite crucible being 1:200, the silicon carbide powder layer 1 comprising a first silicon carbide powder layer 11, a second silicon carbide powder layer 12 and a third silicon carbide powder layer 13 laminated, a hole adapted to be filled with the silicon dioxide layer 2 being formed in the second silicon carbide powder layer 12, the silicon dioxide layer 2 being filled in the hole, the thickness of each of the first silicon carbide powder layer 11, the second silicon carbide powder layer 12, the third silicon carbide powder layer 13 and the silicon dioxide layer 2 being uniform, and the thickness of the silicon dioxide layer 2 being in accordance with the thickness of the second silicon carbide powder layer 12, the thickness ratio of the first silicon carbide powder layer 11, the silicon dioxide layer 2 and the third silicon carbide powder layer 13 being 1:2:1, the projected area of the second silicon carbide powder layer 12 in the z direction is 2 times that of the silicon dioxide layer 2 in the z direction, a graphite crucible upper cover is covered, and a silicon carbide seed crystal is fixed on the inner side of the graphite crucible upper cover.
(3) The graphite crucible is placed in an argon atmosphere, and crystal growth is carried out for 120 hours under the conditions that the temperature is 2250 ℃ and the pressure is 300 Pa.
Example 4
The procedure of example 2 was followed, except that the molar ratio of silicon carbide powder, silica and ceria was 21000:20:1 (silicon carbide powder 3 g), the thickness ratio of the first silicon carbide powder layer 11, the silicon dioxide layer 2, and the third silicon carbide powder layer 13 is 1:2:2, the projected area of the second silicon carbide powder layer 12 in the z-direction is 4 times the projected area of the silicon dioxide layer 2 in that direction.
Example 5
The method of example 3 was followed, except that the thickness ratio of the first silicon carbide powder layer 11, the silicon dioxide layer 2 and the third silicon carbide powder layer 13 was 1:1:3, the projected area of the second silicon carbide powder layer 12 in the z-direction is 3 times the projected area of the silicon dioxide layer 2 in that direction.
Example 6
(1) The silicon carbide powder was preheated at 400℃for 0.5h.
(2) Adding the silicon carbide powder and the silicon dioxide in the step (1) into a graphite crucible, wherein the molar ratio of the silicon carbide powder to the silicon dioxide is 90:1 (3 kg of silicon carbide powder), the distance from the top of the silicon carbide powder to the top of the graphite crucible being 20mm; wherein the silicon carbide powder and the silicon dioxide form a wrapping reaction structure in the graphite crucible, referring to fig. 2, the wrapping reaction structure comprises a silicon dioxide layer 2 and a silicon carbide powder layer 1 wrapped outside the silicon dioxide layer 2, the silicon carbide powder layer 1 comprises a first silicon carbide powder layer 11, a second silicon carbide powder layer 12 and a third silicon carbide powder layer 13 which are arranged in a stacked manner, a hole suitable for filling the silicon dioxide layer 2 is formed on the second silicon carbide powder layer 12, the silicon dioxide layer 2 is filled in the hole, the thickness of each of the first silicon carbide powder layer 11, the second silicon carbide powder layer 12, the third silicon carbide powder layer 13 and the silicon dioxide layer 2 is uniform, the thickness of the silicon dioxide layer 2 is consistent with the thickness of the second silicon carbide powder layer 12, and the thickness ratio of the first silicon carbide powder layer 11, the silicon dioxide layer 2 and the third silicon carbide powder layer 13 is 1:2:1, the projected area of the second silicon carbide powder layer 12 in the z direction is 2 times that of the silicon dioxide layer 2 in the z direction, a graphite crucible upper cover is covered, and a silicon carbide seed crystal is fixed on the inner side of the graphite crucible upper cover.
(3) The graphite crucible is placed in an argon atmosphere, and crystal growth is carried out for 120 hours under the conditions that the temperature is 2250 ℃ and the pressure is 300 Pa.
Example 7
(1) The silicon carbide powder was preheated at 400℃for 0.5h.
(2) Adding the silicon carbide powder and the cerium oxide in the step (1) into a graphite crucible, wherein the molar ratio of the silicon carbide powder to the cerium oxide is 90:1 (3 kg of silicon carbide powder), the distance from the top of the silicon carbide powder to the top of the graphite crucible being 20mm; wherein silicon carbide powder and ceria are caused to form a laminated reaction structure in a graphite crucible, see fig. 3, the laminated reaction structure comprising a silicon dioxide layer 2 and a ceria layer 3 laminated on a silicon carbide powder layer 1, the ceria layer 3 being placed in a tantalum crucible as a spacer and placed in the center position of a silicon carbide powder layer 11, the volume ratio of the tantalum crucible to the graphite crucible being 1:200, a graphite crucible upper cover being capped, and a silicon carbide seed crystal being fixed to the inner side of the graphite crucible upper cover.
(3) The graphite crucible is placed in an argon atmosphere, and crystal growth is carried out for 120 hours under the conditions that the temperature is 2250 ℃ and the pressure is 300 Pa.
Example 8
The procedure of example 7 was followed except that the volume ratio of tantalum crucible to graphite crucible was 1:50.
Comparative example 1
(1) The silicon carbide powder was preheated at 400℃for 0.5h.
(2) Sequentially filling silicon carbide powder, mixed powder of silicon carbide powder and ceria and silicon carbide powder into a graphite crucible to form a first silicon carbide powder layer, a mixed powder layer of silicon carbide powder and ceria and a second silicon carbide powder layer in the graphite crucible from bottom to top; in the mixed powder layer of silicon carbide powder and cerium oxide, the weight of the silicon carbide powder is 100g, the weight of the cerium oxide is 0.02g, the distance H between the upper surface of the mixed powder layer of the silicon carbide powder and the cerium oxide and the upper surface of the second silicon carbide powder layer is 50mm, a crucible upper cover is covered, and silicon carbide seed crystals are fixed on the inner side of the crucible upper cover.
(3) And (3) growing crystals for 120 hours in a mixed gas atmosphere of argon and nitrogen at a temperature of 2250 ℃ and a pressure of 300 Pa.
Comparative example 2
(1) The silicon carbide powder was preheated at 400℃for 0.5h.
(2) Adding the mixture of silicon carbide powder and silicon dioxide in the step (1) into a graphite crucible, wherein the molar ratio of the silicon carbide powder to the silicon dioxide is 90:1 (3 kg of silicon carbide powder), the distance from the top of the mixture to the top of the graphite crucible being 20mm; the upper cover of the graphite crucible is covered, and silicon carbide seed crystals are fixed on the inner side of the upper cover of the graphite crucible.
(3) The graphite crucible is placed in an argon atmosphere, and crystal growth is carried out for 120 hours under the conditions that the temperature is 2250 ℃ and the pressure is 300 Pa.
Test case
The graphitization degree measurement was performed on the crystals obtained in the above examples and comparative examples, and the obtained data are shown in table 1:
TABLE 1
| Numbering device | Degree of graphitization (%) | Carbon inclusion concentration (units/cm) 2 ) |
| Example 1 | 85 | 0 |
| Example 2 | 81 | 0 |
| Example 3 | 82 | 0 |
| Example 4 | 90 | 0 |
| Example 5 | 87 | 0.01 |
| Example 6 | 89 | 0.015 |
| Example 7 | 90 | 0.03 |
| Example 8 | 88 | 0.01 |
| Comparative example 1 | 93 | 0.35 |
| Comparative example 2 | 92 | 0.4 |
From the data, examples 1-8 have lower graphitization levels than comparative examples 1 and 2, demonstrating that the process within the scope of the present invention is effective in reducing the graphitization levels of the resulting crystals.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (9)
1. A method for producing a reduced carbon-coated silicon carbide single crystal, the method comprising at least the steps of charging and growing the crystal, characterized in that the charging step comprises: adding silicon carbide powder and oxide into a crystal growth container, wherein the oxide is silicon dioxide and/or cerium dioxide, and the molar ratio of the silicon carbide powder to the oxide is 20-500:1, a step of;
wherein the silicon carbide powder and the oxide are caused to form a pack reaction structure, a stack reaction structure, or a composite reaction structure in the growth vessel; the coating reaction structure comprises a silicon dioxide layer (2) and a silicon carbide powder layer (1) coated outside the silicon dioxide layer (2); the laminated reaction structure comprises a silicon carbide powder layer (1) and a cerium oxide layer (3) laminated on the silicon carbide powder layer (1), wherein a separator is arranged between the cerium oxide layer (3) and the silicon carbide powder layer (1) and is not in direct contact; the composite reaction structure comprises a silicon dioxide layer (2), a silicon carbide powder layer (1) wrapped outside the silicon dioxide layer (2) and a cerium oxide layer (3) which is arranged on the silicon carbide powder layer (1) in a laminated mode, wherein a separator is arranged between the cerium oxide layer (3) and the silicon carbide powder layer (1) and is not in direct contact.
2. The method for producing a carbon-coated silicon carbide single crystal as claimed in claim 1, further comprising subjecting the silicon carbide powder to a preheating treatment;
the conditions of the preheating treatment include: the temperature is 200-400 ℃ and the time is 0.5-1h.
3. The method for producing a carbon-coated silicon carbide single crystal according to claim 1, wherein the particle diameter of the oxide is smaller than the particle diameter of the silicon carbide powder.
4. A method for producing a carbon-coated silicon carbide single crystal according to any of claims 1 to 3 wherein said oxide is silica.
5. A method of producing a reduced carbon-coated silicon carbide single crystal according to any one of claims 1 to 3, wherein in the coating reaction structure or the composite reaction structure, the silicon carbide powder layer (1) comprises a first silicon carbide powder layer (11), a second silicon carbide powder layer (12) and a third silicon carbide powder layer (13) which are stacked, the second silicon carbide powder layer (12) having formed thereon holes adapted to fill the silicon dioxide layer (2), and the thickness ratio of the first silicon carbide powder layer (11), the silicon dioxide layer (2) and the third silicon carbide powder layer (13) is 1:2-4:1-2.
6. The method for producing a carbon-coated reduced silicon carbide single crystal as claimed in claim 5, wherein the projected area of said second silicon carbide powder layer (12) in the direction (z) in which said first silicon carbide powder layer (11), said second silicon carbide powder layer (12) and said third silicon carbide powder layer (13) are arranged is 1.5 to 2 times the projected area of said silicon dioxide layer (2) in that direction.
7. A method for producing a carbon-coated silicon carbide single crystal according to any of claims 1 to 3 wherein when said oxide contains ceria, said ceria is placed in a tantalum crucible as said separator placed on said silicon carbide powder.
8. The method for producing a carbon-coated silicon carbide single crystal as claimed in claim 7, wherein the ratio of the volumes of the tantalum crucible and the growth vessel is 1:50 to 100.
9. A method for producing a carbon-coated silicon carbide single crystal according to any of claims 1 to 3, wherein said conditions for growing a crystal include: under argon atmosphere, the temperature is 2100-2250 ℃ and the pressure is 300-500Pa.
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| CN110983434A (en) * | 2019-12-27 | 2020-04-10 | 北京天科合达半导体股份有限公司 | Growth method for effectively reducing defects of silicon carbide single crystal and high-quality silicon carbide single crystal |
| CN111593407A (en) * | 2020-05-25 | 2020-08-28 | 北京北方华创微电子装备有限公司 | Silicon carbide growth method |
| CN112481699A (en) * | 2020-11-11 | 2021-03-12 | 山东天岳先进科技股份有限公司 | Preparation method of high-quality silicon carbide single crystal and silicon carbide single crystal |
| CN113089087A (en) * | 2021-04-13 | 2021-07-09 | 哈尔滨科友半导体产业装备与技术研究院有限公司 | Method for improving quality of silicon carbide crystals |
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| CN111593407A (en) * | 2020-05-25 | 2020-08-28 | 北京北方华创微电子装备有限公司 | Silicon carbide growth method |
| CN112481699A (en) * | 2020-11-11 | 2021-03-12 | 山东天岳先进科技股份有限公司 | Preparation method of high-quality silicon carbide single crystal and silicon carbide single crystal |
| CN113089087A (en) * | 2021-04-13 | 2021-07-09 | 哈尔滨科友半导体产业装备与技术研究院有限公司 | Method for improving quality of silicon carbide crystals |
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