CN113026105A - Growth method for preparing silicon carbide crystal by using pretreated powder - Google Patents
Growth method for preparing silicon carbide crystal by using pretreated powder Download PDFInfo
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 180
- 239000013078 crystal Substances 0.000 title claims abstract description 121
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 102
- 239000000843 powder Substances 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims abstract description 56
- 238000010438 heat treatment Methods 0.000 claims abstract description 59
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 38
- 239000008367 deionised water Substances 0.000 claims abstract description 36
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 36
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 34
- 238000002791 soaking Methods 0.000 claims abstract description 14
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 238000002156 mixing Methods 0.000 claims abstract description 11
- 238000002390 rotary evaporation Methods 0.000 claims abstract description 11
- 230000001681 protective effect Effects 0.000 claims abstract description 10
- 239000002904 solvent Substances 0.000 claims abstract description 10
- 238000001704 evaporation Methods 0.000 claims abstract description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 56
- 229910052786 argon Inorganic materials 0.000 claims description 28
- 238000011049 filling Methods 0.000 claims description 25
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 22
- 238000004140 cleaning Methods 0.000 claims description 22
- 238000001816 cooling Methods 0.000 claims description 13
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 11
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 11
- 239000011259 mixed solution Substances 0.000 claims description 11
- 239000003921 oil Substances 0.000 claims description 10
- 239000005662 Paraffin oil Substances 0.000 claims description 6
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 229920002545 silicone oil Polymers 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 10
- 239000001257 hydrogen Substances 0.000 abstract description 10
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 10
- 239000012535 impurity Substances 0.000 abstract description 10
- 238000002360 preparation method Methods 0.000 abstract description 9
- 239000001301 oxygen Substances 0.000 abstract description 8
- 229910052760 oxygen Inorganic materials 0.000 abstract description 8
- 238000002161 passivation Methods 0.000 abstract description 8
- 239000003960 organic solvent Substances 0.000 abstract description 5
- 230000007547 defect Effects 0.000 abstract description 4
- 239000003153 chemical reaction reagent Substances 0.000 abstract description 2
- 239000002994 raw material Substances 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 8
- 238000000354 decomposition reaction Methods 0.000 description 5
- 235000012431 wafers Nutrition 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000000155 melt Substances 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000006184 cosolvent Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/36—Carbides
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
-
- 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
- C30B28/00—Production of homogeneous polycrystalline material with defined structure
- C30B28/12—Production of homogeneous polycrystalline material with defined structure directly from the gas state
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention relates to a growth method for preparing silicon carbide crystals by using pretreated powder, belonging to the technical field of preparation of silicon carbide crystals. In order to solve the problem that the existing silicon carbide powder is easy to cause defects of silicon carbide crystals, the invention provides a growth method for preparing the silicon carbide crystals by using pretreated powder, which comprises the steps of soaking the silicon carbide powder in hydrofluoric acid, and then adding the powder into deionized water at 100 ℃ for heating to obtain hydrogen-passivated silicon carbide powder; fully mixing the hydrogen-passivated silicon carbide powder with a protective solvent, and then evaporating the protective solvent in a rotary evaporation mode until the mixture is powdery to obtain pretreated powder; and finally, preparing the silicon carbide crystal by taking the obtained pretreated powder as a raw material by adopting a PVT method. The pretreatment mode combining hydrogen passivation and organic solvent wrapping protection can maintain the low-oxygen impurity content state on the surface of the powder for a long time, and the yield of the silicon carbide crystals is improved. The preparation method is simple, and the reagent is low in price and safe, and has good practical value.
Description
Technical Field
The invention belongs to the technical field of silicon carbide crystal preparation, and particularly relates to a growth method for preparing silicon carbide crystals by using pretreated powder.
Background
The silicon carbide as the third-generation semiconductor material has the characteristics of wide forbidden band, high breakdown field strength, high thermal conductivity and the like. The method can be applied to the fields of new energy automobiles, photovoltaic inverters, charging piles and the like to achieve the aims of reducing power consumption, improving switching frequency, reducing overall cost and the like.
Since silicon carbide is decomposed before being heated to a melting point under normal pressure, a method similar to the growth of silicon crystal cannot be directly used. At present, the growth methods of the large-size silicon carbide crystal mainly comprise two methods: one is to add a flux to form a melt containing silicon carbide and grow crystals using the melt. The other method is a PVT method, and the method is characterized in that silicon carbide powder is placed at the bottom of a crucible, silicon carbide seed crystals are adhered to the top of the crucible, the powder is decomposed under the conditions of high temperature and inert atmosphere, gas phase generated after decomposition is controlled by temperature gradient and is deposited on the seed crystals, and finally growth of the silicon carbide crystals is completed. The second PVT method is currently used for the large-scale production of silicon carbide crystals, since the first method causes a large number of crystal defects due to the introduction of cosolvents into the prepared crystals.
The residual bonds on the surface of the silicon carbide powder react with oxygen or water vapor in the air at room temperature to generate a layer of oxide film which can resist further oxidation caused by the penetration of external oxygen, so that the silicon carbide powder has good oxidation stability at normal pressure even at high temperature. In the furnace washing process of crystal preparation, the oxide layer on the surface of the silicon carbide powder is decomposed by heating and high vacuum, and is discharged out of a reaction system together with desorbed impurities and gases.
However, the current common preparation process ignores that partial decomposition products generated in the high-temperature decomposition process of the oxide layer on the surface of the silicon carbide powder are deposited on the surface of the seed crystal due to the action of the temperature gradient mode in the furnace body, and the decomposition products can corrode the surface of the seed crystal and permeate impurities, so that the defects on the surface of the seed crystal are increased, the content of the impurities is increased, and the quality of the silicon carbide crystal is influenced.
Disclosure of Invention
The invention provides a growth method for preparing silicon carbide crystals by using pretreated powder, which aims to solve the problem that the silicon carbide crystals are easy to have defects due to decomposition products generated in the preparation process of an oxide layer on the surface of the existing silicon carbide powder.
The technical scheme of the invention is as follows:
a growth method for preparing silicon carbide crystals by using pretreated powder comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 30-120 s by using 1-10 wt% of hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in the deionized water at 100 ℃ to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with a protective solvent, and then evaporating the protective solvent in a rotary evaporation mode until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal to the top of the crucible, vacuumizing the crucible, keeping the vacuum degree, heating the inside of the crucible to 900-1700 ℃, filling argon into the crucible, heating the inside of the crucible to 1800-2200 ℃, preserving the temperature, growing the silicon carbide crystal, cooling after the crystal growth is finished, and filling argon to normal pressure to obtain the silicon carbide crystal.
Furthermore, in the first step, the concentration of the hydrofluoric acid is 1 wt%, and the soaking time of the silicon carbide powder in the 1 wt% hydrofluoric acid is 60 s.
Further, the silicon carbide powder in the step one is heated in deionized water at 100 ℃ for 300-600 s.
Further, in the step one, the protective solvent is dimethyl silicone oil, white oil or paraffin oil.
Further, the mass volume ratio of the silicon carbide powder to the protective solvent in the step one is 1: 1-1: 2.
Further, the vacuum degree of the vacuum pumping in the crucible in the step two is 10-5-10-3torr。
Further, the heating rate in the crucible in the second step is 500-1000 ℃/h.
Further, the pressure of the argon gas filled in the step two is 0.01-10 atm.
And further, the heat preservation time for the growth of the silicon carbide crystal in the second step is 30-80 h.
And further, after the crystal growth in the second step is finished, cooling to 200-500 ℃, and then filling argon to normal pressure.
The invention has the beneficial effects that:
in the pretreatment process of the silicon carbide powder, a treatment mode combining hydrogen passivation and organic solvent coating protection is adopted, the silicon carbide powder is treated by hydrofluoric acid and boiling water in sequence, then the treated powder which is polluted by oxygen-free impurities and is primarily protected by hydrogen is coated and protected by the organic solvent which is easy to evaporate at high temperature, and the stability of the low-oxygen impurity surface of the silicon carbide powder in a long time is further protected, so that the powder cannot be polluted by air oxidation again due to slow failure of hydrogen passivation in the long-term storage and transportation process.
The pretreated powder prepared by the method can maintain the low-oxygen impurity content state on the surface of the powder for a long time, and can still obtain high-quality silicon carbide crystals when being used for preparing the silicon carbide crystals after being stored for a long time. The resistivity value of the wafer obtained by cutting the crystal prepared by the method for growing the silicon carbide crystal by using the pretreated powder provided by the invention can reach 1.65 x 105-3.49ⅹ105Omega cm, the method can better solve the problem that oxygen impurities block the preparation of semi-insulating silicon carbide wafers by combining hydrogen passivation and organic solvent coating, and improve the yield of silicon carbide crystals. The preparation method is simple, and the reagent is low in price and safe, and has good practical value.
Detailed Description
The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention. The process equipment or apparatus not specifically mentioned in the following examples are conventional in the art, and if not specifically mentioned, the raw materials and the like used in the examples of the present invention are commercially available; unless otherwise specified, the technical means used in the examples of the present invention are conventional means well known to those skilled in the art.
Example 1
The embodiment provides a growth method for preparing silicon carbide crystals by using pretreated powder, which comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 60s by using 1 wt% hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in 100 ℃ deionized water for 300s to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with white oil according to the mass-to-volume ratio of 1:2, and then carrying out rotary evaporation on the white oil until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-5And (3) torr, keeping the vacuum degree, heating the interior of the crucible to 1000 ℃ at a heating rate of 750 ℃/h, filling argon into the crucible to 0.1atm, continuously heating the interior of the crucible to 2100 ℃ at a heating rate of 800 ℃/h, preserving the temperature for 40h to grow the silicon carbide crystal, cooling to 500 ℃ after the crystal growth is finished, and filling argon into the crucible to normal pressure to obtain the silicon carbide crystal.
Example 2
The embodiment provides a growth method for preparing silicon carbide crystals by using pretreated powder, which comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 120s by using 2 wt% hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in 100 ℃ deionized water for 300s to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with dimethyl silicone oil according to the mass-to-volume ratio of 1:1, and then performing rotary evaporation to evaporate the dimethyl silicone oil until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-5And (3) torr, keeping the vacuum degree, heating the interior of the crucible to 900 ℃ at a heating rate of 500 ℃/h, filling argon into the crucible to 0.01atm, continuously heating the interior of the crucible to 1800 ℃ at a heating rate of 500 ℃/h, keeping the temperature for 80h for growing the silicon carbide crystal, cooling to 400 ℃ after the crystal growth is finished, and filling argon into the crucible to normal pressure to obtain the silicon carbide crystal.
Example 3
The embodiment provides a growth method for preparing silicon carbide crystals by using pretreated powder, which comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 100s by using 4 wt% hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in the deionized water at 100 ℃ for 400s to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with paraffin oil according to the mass-to-volume ratio of 1:1.5, and then evaporating the paraffin oil in a rotary evaporation mode until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-4And (3) torr, keeping the vacuum degree, heating the interior of the crucible to 1200 ℃ at a heating rate of 600 ℃/h, filling argon into the crucible to 0.5atm, continuously heating the interior of the crucible to 1900 ℃ at a heating rate of 600 ℃/h, preserving the temperature for 40h for growing the silicon carbide crystal, cooling to 500 ℃ after the crystal growth is finished, and filling argon into the crucible to normal pressure to obtain the silicon carbide crystal.
Example 4
The embodiment provides a growth method for preparing silicon carbide crystals by using pretreated powder, which comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 80s by using 5 wt% hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in 100 ℃ deionized water for 400s to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with white oil according to the mass-to-volume ratio of 1:2, and then carrying out rotary evaporation on the white oil until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-4And (3) torr, keeping the vacuum degree, heating the interior of the crucible to 1400 ℃ at a heating rate of 700 ℃/h, filling argon into the crucible to 1atm, continuously heating the interior of the crucible to 2000 ℃ at a heating rate of 700 ℃/h, keeping the temperature for 60h for growing the silicon carbide crystal, cooling to 300 ℃ after the crystal growth is finished, and filling argon into the crucible to normal pressure to obtain the silicon carbide crystal.
Example 5
The embodiment provides a growth method for preparing silicon carbide crystals by using pretreated powder, which comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 50s by using 6 wt% hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in 100 ℃ deionized water for 500s to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with dimethyl silicone oil according to the mass-to-volume ratio of 1:1, and then performing rotary evaporation to evaporate the dimethyl silicone oil until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-3torr, the inside of the crucible was heated to 150 at a heating rate of 800 ℃/h while maintaining the degree of vacuumAnd (3) filling argon into the crucible to 2atm at the temperature of 0 ℃, continuously heating the interior of the crucible to 2100 ℃ at the heating rate of 800 ℃/h, preserving the heat for 40h to grow the silicon carbide crystal, cooling to 300 ℃ after the crystal growth is finished, and filling argon to normal pressure to obtain the silicon carbide crystal.
Example 6
The embodiment provides a growth method for preparing silicon carbide crystals by using pretreated powder, which comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 40s by using 8 wt% hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in 100 ℃ deionized water for 500s to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with paraffin oil according to the mass-to-volume ratio of 1:1.5, and then evaporating the paraffin oil in a rotary evaporation mode until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-3And (3) torr, keeping the vacuum degree, heating the interior of the crucible to 1600 ℃ at a heating rate of 900 ℃/h, filling argon into the crucible to 5atm, continuously heating the interior of the crucible to 2200 ℃ at a heating rate of 900 ℃/h, preserving the temperature for 40h to grow the silicon carbide crystal, cooling to 200 ℃ after the crystal growth is finished, and filling argon into the crucible to normal pressure to obtain the silicon carbide crystal.
Example 7
The embodiment provides a growth method for preparing silicon carbide crystals by using pretreated powder, which comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 30s by using 10 wt% hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in the deionized water at 100 ℃ for 600s to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with white oil according to the mass-to-volume ratio of 1:2, and then carrying out rotary evaporation on the white oil until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-5And (3) keeping the vacuum degree, heating the interior of the crucible to 1700 ℃ at a heating rate of 1000 ℃/h, filling argon to 10atm, continuously heating the interior of the crucible to 2200 ℃ at a heating rate of 1000 ℃/h, keeping the temperature for 30h for growing the silicon carbide crystal, cooling to 200 ℃ after the crystal growth is finished, and filling argon to normal pressure to obtain the silicon carbide crystal.
Example 8
The embodiment provides a growth method for preparing silicon carbide crystals by using pretreated powder, which comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 60s by using 1 wt% hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in 100 ℃ deionized water for 300s to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with white oil according to the mass-to-volume ratio of 1:2, and then carrying out rotary evaporation on the white oil until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-5And (3) torr, keeping the vacuum degree, heating the interior of the crucible to 1000 ℃ at a heating rate of 750 ℃/h, filling argon into the crucible to 0.1atm, continuously heating the interior of the crucible to 2100 ℃ at a heating rate of 800 ℃/h, preserving the temperature for 40h to grow the silicon carbide crystal, cooling to 500 ℃ after the crystal growth is finished, and filling argon into the crucible to normal pressure to obtain the silicon carbide crystal.
Comparative example 1
In the comparative example, silicon carbide crystal is grown by using silicon carbide powder which is stored for 14 days and is only subjected to hydrogen passivation treatment, and the specific method comprises the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 60s by using 1 wt% hydrofluoric acid, cleaning by using deionized water, then putting the silicon carbide powder into deionized water with the temperature of 100 ℃, heating for 300s to obtain hydrogen-passivated silicon carbide powder, and storing for 14 days in a normal environment;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder which is only passivated by hydrogen and stored for 14 days in the step I at the bottom of a crucible, adhering a silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-5And (3) torr, keeping the vacuum degree, heating the interior of the crucible to 1000 ℃ at a heating rate of 750 ℃/h, filling argon into the crucible to 0.1atm, continuously heating the interior of the crucible to 2100 ℃ at a heating rate of 800 ℃/h, preserving the temperature for 40h to grow the silicon carbide crystal, cooling to 500 ℃ after the crystal growth is finished, and filling argon into the crucible to normal pressure to obtain the silicon carbide crystal.
Comparative example 2
In the comparative example, silicon carbide crystal is grown by using silicon carbide powder which is stored for 14 days and is not pretreated, and the specific method for preparing the silicon carbide crystal by the PVT method comprises the following steps:
placing the silicon carbide powder which is stored for 14 days and is not pretreated at the bottom of the crucible, sticking the silicon carbide seed crystal at the top of the crucible, and vacuumizing the interior of the crucible to 10 DEG-5And (3) torr, keeping the vacuum degree, heating the interior of the crucible to 1000 ℃ at a heating rate of 750 ℃/h, filling argon into the crucible to 0.1atm, continuously heating the interior of the crucible to 2100 ℃ at a heating rate of 800 ℃/h, preserving the temperature for 40h to grow the silicon carbide crystal, cooling to 500 ℃ after the crystal growth is finished, and filling argon into the crucible to normal pressure to obtain the silicon carbide crystal.
The silicon carbide crystals prepared in example 1, example 8, comparative example 1 and comparative example 2 were cut into wafers, and the resistivity values of the three wafers were measured, and the results are shown in table 1.
TABLE 1
| Test object | Resistivity value (omega cm) |
| Example 1 | 1.65ⅹ105-3.49ⅹ105 |
| Example 8 | 1.65ⅹ105-3.49ⅹ105 |
| Comparative example 1 | 9.12ⅹ102-3.44ⅹ105 |
| Comparative example 2 | 6.73ⅹ102-3.54ⅹ105 |
As can be seen from a comparison of the data in Table 1, the silicon carbide crystal prepared in example 8 from the silicon carbide powder stored for 14 days had almost no difference in resistivity values from the silicon carbide crystal prepared from the silicon carbide powder not stored in example 1, and was significantly superior to the silicon carbide crystal prepared from the powder without any pretreatment and the powder subjected to only hydrogen passivation. Compared with untreated powder and powder subjected to only hydrogen passivation treatment, the powder obtained by the pretreatment method combining hydrogen passivation and organic solvent coating can maintain the low-oxygen impurity content state on the surface of the powder for a long time, better solve the problem of oxygen impurities in preparation of semi-insulating silicon carbide wafers and improve the yield of the silicon carbide crystals.
Claims (10)
1. A growth method for preparing silicon carbide crystals by using pretreated powder is characterized by comprising the following steps:
step one, preparing pretreated powder:
cleaning silicon carbide powder by using a mixed solution of concentrated ammonia water and hydrogen peroxide with the same volume and deionized water in sequence, soaking the silicon carbide powder for 30-120 s by using 1-10 wt% of hydrofluoric acid, cleaning by using deionized water, and then heating the silicon carbide powder in the deionized water at 100 ℃ to obtain hydrogen-passivated silicon carbide powder; fully mixing the obtained hydrogen-passivated silicon carbide powder with a protective solvent, and then evaporating the protective solvent in a rotary evaporation mode until the mixture is powdery to obtain pretreated powder;
step two, preparing silicon carbide crystals by a PVT method:
placing the pretreated powder obtained in the step one at the bottom of a crucible, adhering a silicon carbide seed crystal to the top of the crucible, vacuumizing the crucible, keeping the vacuum degree, heating the inside of the crucible to 900-1700 ℃, filling argon into the crucible, heating the inside of the crucible to 1800-2200 ℃, preserving the temperature, growing the silicon carbide crystal, cooling after the crystal growth is finished, and filling argon to normal pressure to obtain the silicon carbide crystal.
2. The method for growing silicon carbide crystals according to claim 1, wherein in step one, the concentration of hydrofluoric acid is 1 wt%, and the soaking time of the silicon carbide powder in 1 wt% hydrofluoric acid is 60 s.
3. The growing method for preparing silicon carbide crystals by using the pretreated powder material as claimed in claim 1 or 2, wherein the time for heating the silicon carbide powder material in the step one in deionized water at 100 ℃ is 300-600 s.
4. The growing method for preparing silicon carbide crystals by using the pretreated powder material is characterized in that the protective solvent in the step one is dimethyl silicone oil, white oil or paraffin oil.
5. The growing method for preparing silicon carbide crystals by using the pretreated powder is characterized in that the mass volume ratio of the silicon carbide powder to the protective solvent in the step one is 1: 1-1: 2.
6. The method for growing silicon carbide crystals by using pretreated powder as claimed in claim 5, wherein the degree of vacuum of the vacuum inside the crucible in step two is 10-5-10-3torr。
7. The growing method for preparing silicon carbide crystals by using the pretreated powder as claimed in claim 6, wherein the heating rate in the crucible in the second step is 500-1000 ℃/h.
8. The method for growing silicon carbide crystals using the pretreated powder in claim 7, wherein the pressure of the argon gas introduced in step two is 0.01-10 atm.
9. The growing method for preparing silicon carbide crystals by using the pretreated powder material is characterized in that the heat preservation time for growing the silicon carbide crystals in the second step is 30-80 h.
10. The growing method for preparing silicon carbide crystals by using the pretreated powder material as claimed in claim 9, wherein the temperature is reduced to 200-500 ℃ after the crystal growth in the second step, and then argon is added to the mixture to reach normal pressure.
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