CN113463198A - Preparation method of silicon nitride ceramic - Google Patents
Preparation method of silicon nitride ceramic Download PDFInfo
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- CN113463198A CN113463198A CN202110671471.5A CN202110671471A CN113463198A CN 113463198 A CN113463198 A CN 113463198A CN 202110671471 A CN202110671471 A CN 202110671471A CN 113463198 A CN113463198 A CN 113463198A
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- 239000000919 ceramic Substances 0.000 title claims abstract description 45
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 41
- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 37
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 235000012431 wafers Nutrition 0.000 claims abstract description 71
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 58
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims abstract description 56
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 48
- 239000010703 silicon Substances 0.000 claims abstract description 48
- 239000000843 powder Substances 0.000 claims abstract description 31
- 238000005245 sintering Methods 0.000 claims abstract description 31
- 238000005121 nitriding Methods 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 22
- 230000006911 nucleation Effects 0.000 claims abstract description 20
- 238000010899 nucleation Methods 0.000 claims abstract description 20
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000005266 casting Methods 0.000 claims abstract description 16
- 238000001816 cooling Methods 0.000 claims abstract description 16
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000011777 magnesium Substances 0.000 claims abstract description 14
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- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 11
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- 239000011863 silicon-based powder Substances 0.000 claims abstract description 9
- 238000010438 heat treatment Methods 0.000 claims abstract description 8
- 238000011068 loading method Methods 0.000 claims abstract description 8
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 8
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 7
- 238000004321 preservation Methods 0.000 claims abstract description 7
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- 238000005520 cutting process Methods 0.000 claims abstract description 6
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- 238000004519 manufacturing process Methods 0.000 claims description 19
- 239000007789 gas Substances 0.000 claims description 7
- 229910052727 yttrium Inorganic materials 0.000 claims description 4
- 229910052684 Cerium Inorganic materials 0.000 claims description 3
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 3
- 229910052691 Erbium Inorganic materials 0.000 claims description 3
- 229910052693 Europium Inorganic materials 0.000 claims description 3
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 3
- 229910052689 Holmium Inorganic materials 0.000 claims description 3
- 229910052765 Lutetium Inorganic materials 0.000 claims description 3
- 229910052779 Neodymium Inorganic materials 0.000 claims description 3
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 3
- 229910052773 Promethium Inorganic materials 0.000 claims description 3
- 229910052772 Samarium Inorganic materials 0.000 claims description 3
- 229910052771 Terbium Inorganic materials 0.000 claims description 3
- 229910052775 Thulium Inorganic materials 0.000 claims description 3
- 229910052769 Ytterbium Inorganic materials 0.000 claims description 3
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 3
- 229910003460 diamond Inorganic materials 0.000 claims description 3
- 239000010432 diamond Substances 0.000 claims description 3
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims description 3
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 claims description 3
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 claims description 3
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 claims description 3
- KJZYNXUDTRRSPN-UHFFFAOYSA-N holmium atom Chemical compound [Ho] KJZYNXUDTRRSPN-UHFFFAOYSA-N 0.000 claims description 3
- 229910052746 lanthanum Inorganic materials 0.000 claims description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 3
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 claims description 3
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 claims description 3
- VQMWBBYLQSCNPO-UHFFFAOYSA-N promethium atom Chemical compound [Pm] VQMWBBYLQSCNPO-UHFFFAOYSA-N 0.000 claims description 3
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 claims description 3
- 229910052706 scandium Inorganic materials 0.000 claims description 3
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 claims description 3
- 239000002210 silicon-based material Substances 0.000 claims description 3
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 claims description 3
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 claims description 3
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 3
- 229920005591 polysilicon Polymers 0.000 abstract 2
- 239000013078 crystal Substances 0.000 description 16
- 239000000463 material Substances 0.000 description 6
- 239000002994 raw material Substances 0.000 description 5
- 238000011160 research Methods 0.000 description 4
- 238000005229 chemical vapour deposition Methods 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 238000005240 physical vapour deposition Methods 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- FRNOGLGSGLTDKL-UHFFFAOYSA-N thulium atom Chemical compound [Tm] FRNOGLGSGLTDKL-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000013081 microcrystal Substances 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000005543 nano-size silicon particle Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000007517 polishing process Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 239000010409 thin film Substances 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
- 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
- C30B29/38—Nitrides
-
- 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
- C30B28/04—Production of homogeneous polycrystalline material with defined structure from liquids
- C30B28/06—Production of homogeneous polycrystalline material with defined structure from liquids by normal freezing or freezing under temperature gradient
-
- 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
- C30B29/02—Elements
- C30B29/06—Silicon
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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
- C30B31/00—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor
- C30B31/06—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor by contacting with diffusion material in the gaseous state
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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
- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
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- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention relates to a preparation method of silicon nitride ceramics, which comprises the following steps: s1) polycrystalline silicon ingot casting: the silicon powder nucleation method directionally solidifies the polysilicon ingot, uniformly mixing 80-95 wt% of high-purity silicon powder, 1-10 wt% of magnesium-containing powder and 1-10% of rare earth element powder, then loading the mixture into a quartz crucible with the bottom being sprayed with a quartz sand nucleation layer, loading the mixture into an ingot casting furnace, and controlling the cooling rate after ingot casting to form the superfine microcrystalline polysilicon ingot with the grain size of 0.5-100 mu m; s2) preparing a polycrystalline silicon wafer: cutting a silicon ingot into polycrystalline silicon chips with the thickness of 0.1mm-1 mm; s3) silicon wafer nitriding: stacking polycrystalline silicon wafers in a sintering furnace, separating the silicon wafers by using graphite plates with BN coatings, vacuumizing, nitriding in a nitrogen atmosphere at the nitriding temperature of 1350-1400 ℃, at the heating rate of 20-100 ℃/h and at the heat preservation time of 1-12 h, and cooling along with the furnace; s4) sintering the silicon wafer blank: the silicon wafer blank subjected to nitriding sintering and the jig are placed in a sintering furnace, and sintering is carried out at the sintering temperature of 1700-1900 ℃ and the nitrogen pressure of 0.5-20 MPa in a nitrogen atmosphere.
Description
Technical Field
The invention belongs to the technical field of silicon nitride ceramic preparation, and particularly relates to a method for preparing polycrystalline silicon nitride ceramic by using polycrystalline silicon as a raw material.
Background
Active solder bonding (AMB) copper clad ceramic substrates are one of the most important packaging materials for high power semiconductor modules. The silicon nitride ceramic plate with high thermal conductivity is the most important main material in the manufacturing process of the AMB copper-clad ceramic substrate, and accounts for more than 50% of the cost of the whole product. The conventional preparation process of the silicon nitride ceramic chip comprises slurry preparation, blank forming, sintering and ceramic chip surface treatment, wherein the raw material is high-purity micro-nano silicon nitride powder with high price. In the traditional process, high-purity raw materials and strict blank forming control are both guaranteed for producing the high-heat-conductivity silicon nitride ceramic chip, and are also reasons for causing high manufacturing cost. Therefore, to significantly reduce the production cost of silicon nitride ceramic wafers, the ceramic wafer production process must be improved.
With the rapid development of the solar cell industry, the silicon wafer serving as the main raw material of the solar cell has large production scale and low cost, wherein the price of the polycrystalline silicon wafer is maintained at 1-2 yuan/wafer in 2021 year. The polycrystalline silicon wafer is made of silicon powder with extremely high purity, the impurity content is extremely low, and the polycrystalline silicon wafer with low price provides more possibilities for downstream markets.
In the field of research and production of microelectronic and optoelectronic materials and devices, silicon nitride is an important thin film material, and is often used as a capacitor dielectric due to its large dielectric constant. The silicon nitride film is produced on the surface of the silicon wafer by a Chemical Vapor Deposition (CVD) method or a Physical Vapor Deposition (PVD) method, wherein the direct nitridation of the silicon wafer belongs to the chemical vapor deposition, and the treated silicon wafer is placed in NH3Or N2And nitriding the silicon wafer in the atmosphere to generate a silicon nitride film.
Therefore, compared with the traditional production process of the silicon nitride ceramic chip, the method for preparing the high-thermal-conductivity silicon nitride ceramic chip by directly nitriding the polycrystalline silicon chip is one of feasible methods. The method means that the silicon wafer prepared in the solar cell field is used as a ceramic blank and is directly sintered, so that the production cost of the ceramic wafer is obviously reduced, and the method is a pioneering innovation in the ceramic preparation field.
Regarding the direct nitridation of the surface of the silicon wafer, many researches are carried out in the prior art, for example, in journal article "direct nitridation of the surface of the silicon wafer subjected to high-temperature heat treatment in nitrogen atmosphere", a high-purity nitrogen atmosphere needs to be provided for producing a silicon nitride film on the surface of the silicon wafer by nitridation, and the temperature needs to be higher than 1100 ℃; in a study paper, "dynamics and mechanism research of direct nitrogen nitridation of silicon wafers", it is mentioned that a silicon nitride layer prepared on the surface of a silicon wafer can prevent the silicon wafer from being further nitrided, and the thickness of the silicon nitride layer is in a micro-nano level. How to improve the nitridation degree of the silicon wafer is the key for producing silicon nitride ceramics by using the silicon wafer nitridation.
Disclosure of Invention
The invention is carried out by means of the research, provides a new possibility for the preparation method of the silicon nitride ceramic aiming at the problem of high cost of the silicon nitride ceramic prepared by the conventional method, and provides the preparation method of the silicon nitride ceramic by taking the polycrystalline silicon chip as the raw material and researching the surface nitriding condition of the polycrystalline silicon chip.
The improvement idea of the invention is as follows: the silicon chip manufacturing and the ceramic production are organically combined together, and the polycrystalline silicon chip with low material cost is used for replacing a ceramic green body for nitriding, so that the steps of green body forming, green body processing and the like are omitted, and the process is simplified; meanwhile, in the process of polycrystalline silicon ingot casting, rare earth elements such as Mg and Y are dissolved in gaps of silicon crystal grains to obtain a polycrystalline silicon wafer with fine grains, so that the silicon wafer is easier to nitride.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the preparation method of the silicon nitride ceramic provided by the invention comprises the following steps:
s1) polycrystalline silicon ingot casting: directionally solidifying a polycrystalline silicon ingot by adopting a silicon powder nucleation method, uniformly mixing 80-95 wt% of high-purity silicon powder, 1-10 wt% of magnesium-containing powder and 1-10% of rare earth element powder, then loading the mixture into a quartz crucible with a quartz sand nucleation layer sprayed at the bottom, loading the mixture into an ingot casting hearth, and controlling the cooling rate after ingot casting to form a superfine microcrystalline polycrystalline silicon ingot with the grain size of 0.5-100 mu m;
s2) preparing a polycrystalline silicon wafer: cutting the silicon ingot in the S1 into a polycrystalline silicon slice with the thickness of 0.1mm-1 mm;
s3) silicon wafer nitriding: stacking polycrystalline silicon wafers in a sintering furnace, separating the silicon wafers by using graphite plates with BN coatings, vacuumizing, nitriding in a nitrogen atmosphere at the nitriding temperature of 1350-1400 ℃, at the heating rate of 20-100 ℃/h and at the heat preservation time of 1-12 h, and cooling along with the furnace;
s4) sintering the silicon wafer blank: the silicon wafer blank subjected to nitriding sintering and the jig are placed in a sintering furnace, and sintering is carried out at the sintering temperature of 1700-1900 ℃ and the nitrogen pressure of 0.5-20 MPa in a nitrogen atmosphere.
Preferably, in step S1, the magnesium-containing powder is Mg powder, MgO powder, MgSiN powder2Powder, SiMg2Any one or more of the powders; the rare earth element powder is any one or mixture of powders of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), yttrium (Y), scandium (Sc) and oxides thereof.
Preferably, in step S1, the cooling rate is controlled to be 10-40 ℃/h after ingot casting.
Preferably, in step S1, the bottom of the ingot furnace body is provided with an ultrasonic generator, the ultrasonic generator is started at the initial stage of silicon material cooling and nucleation, the running power of the ultrasonic generator is 800w-1200w, the frequency is 15-25kHz, and the starting time is 5min-10 min.
Preferably, in step S1, the thickness of the quartz sand nucleation layer sprayed on the bottom of the quartz crucible is 0.2mm-0.8mm, and the particle size of the quartz sand is 20 μm-80 μm.
Preferably, in step S2, the silicon ingot is cut into a polycrystalline silicon wafer by a silicon ingot slicing process, a radial polishing process, and a diamond wire cutting process.
Preferably, in step S3, the furnace body is first evacuated to a vacuum degree of 0.1Pa to 0.01Pa, and then high purity N is introduced2And H2Mixed gas (H) of (2)25%) and subsequently heating, maintaining a gas pressure of 0.03-2 MPa.
Preferably, in the step S4, the heat preservation time for sintering the silicon wafer blank is 2-20 h, and the heating rate is 20-100 ℃/h.
The invention has the following beneficial effects:
according to the invention, a polycrystalline silicon wafer with low material cost is used for replacing a ceramic green body to carry out nitridation, the polycrystalline silicon ingot is cut into the polycrystalline silicon wafer, and then surface nitridation and sintering are directly carried out to obtain the polycrystalline silicon nitride ceramic, so that the steps of blank forming, blank processing and the like are omitted.
Aiming at the problem of low nitriding degree of the conventional polycrystalline silicon wafer, the process is improved on the basis of the original preparation of the polycrystalline silicon wafer, Mg and rare earth elements are introduced into the grain boundary of the polycrystalline silicon wafer and can play a role in expanding gaps among crystals, so that the nitrogen adsorption capacity and the nitriding capacity are improved, the cooling rate during crystal nucleation can be increased, and ultrasonic vibration is applied during crystal nucleation, so that the polycrystalline silicon wafer with small crystal grains can be obtained, and the improvement of the nitriding degree of silicon crystals is facilitated. After surface nitridation and sintering of the silicon wafer blank, the high-thermal-conductivity silicon nitride ceramic wafer is formed, and a new idea is provided for production of the silicon nitride ceramic wafer.
Drawings
FIG. 1 is a flow chart of a method for preparing a silicon nitride ceramic according to the present invention.
Detailed Description
The following embodiments are implemented on the premise of the technical scheme of the present invention, and give detailed implementation modes and specific operation procedures, but the protection scope of the present invention is not limited to the following embodiments.
Referring to fig. 1, the method for preparing silicon nitride ceramics in this embodiment includes the following steps:
s1) polycrystalline silicon ingot casting: directionally solidifying a polycrystalline silicon ingot by adopting a silicon powder nucleation method, uniformly mixing 80-95 wt% of high-purity silicon powder, 1-10 wt% of magnesium-containing powder and 1-10% of rare earth element powder, then loading the mixture into a quartz crucible with a quartz sand nucleation layer sprayed at the bottom, and loading the mixture into an ingot casting hearth, after casting the ingot at 1400 ℃, controlling the cooling rate to be 10-40 ℃/h, and forming an ultrafine microcrystalline polycrystalline silicon ingot with the grain size of 0.5-100 mu m;
wherein the magnesium-containing powder is Mg powder, MgO powder, MgSiN2Powder, SiMg2Any one or more of the powders; the rare earth element powder is any one or mixture of powders of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), yttrium (Y), scandium (Sc) and oxides thereof.
The thickness of the quartz sand nucleation layer sprayed at the bottom of the quartz crucible is 0.2mm-0.8mm, and the particle size of the quartz sand is 20 μm-80 μm.
In order to obtain a polycrystalline silicon wafer with fine grains, the bottom of an ingot casting furnace body is provided with an ultrasonic generator, the ultrasonic generator is started at the initial stage of silicon material cooling and nucleation, the running power of the ultrasonic generator is 800w-1200w, the frequency is 15-25kHz, and the starting time is 5min-10 min.
In the step, the quartz sand nucleation layer provides crystal nuclei, Mg and rare earth elements are introduced into the crystal boundary of the polycrystalline silicon wafer, the cooling rate during crystal nucleation can be increased, the size of crystal grains is controlled by controlling the cooling rate and ultrasonic vibration, superfine microcrystals are obtained, and the improvement of the nitriding degree of silicon crystals is facilitated.
S2) preparing a polycrystalline silicon wafer: the silicon ingot in the S1 is sequentially subjected to silicon ingot square cutting, radial polishing and diamond wire cutting to prepare a polycrystalline silicon slice with the thickness of 0.1mm-1 mm;
s3) silicon wafer nitriding: the polycrystalline silicon wafers are stacked in a sintering furnace, and the silicon wafers are separated by a graphite plate with a BN coating. Firstly, the furnace body is vacuumized to the vacuum degree of 0.1Pa-0.01Pa, and then high-purity N is introduced2And H2Mixed gas (H) of (2)2The volume fraction is 5 percent), then the temperature is raised, the nitriding is carried out under the conditions that the nitriding temperature is 1350-1400 ℃, the temperature raising rate is 20-100 ℃/h, the heat preservation time is 1-12 h, the temperature is cooled along with the furnace, and the gas pressure is kept to be 0.03-2 MPa in the whole process.
S4) sintering the silicon wafer blank: the silicon wafer blank after the nitridation sintering and the jig are placed in a sintering furnace, and the sintering is carried out under the conditions of a sintering temperature of 1700-1900 ℃, a heating rate of 20-100 ℃/h, a heat preservation time of 2-20 h and a nitrogen pressure of 0.5-20 MPa by adopting a nitrogen atmosphere to obtain the polycrystalline silicon nitride ceramic plate.
According to the invention, a polycrystalline silicon wafer with low material cost is used for replacing a ceramic green body to carry out nitridation, the polycrystalline silicon ingot is cut into the polycrystalline silicon wafer, and then surface nitridation and sintering are directly carried out to obtain the polycrystalline silicon nitride ceramic, so that the steps of blank forming, blank processing and the like are omitted.
Aiming at the problem of low nitriding degree of the conventional polycrystalline silicon wafer, the process is improved on the basis of the original preparation of the polycrystalline silicon wafer, Mg and rare earth elements are introduced into the grain boundary of the polycrystalline silicon wafer and can play a role in expanding gaps among crystals, so that the nitrogen adsorption capacity and the nitriding capacity are improved, the cooling rate during crystal nucleation can be increased, and ultrasonic vibration is applied during crystal nucleation, so that the polycrystalline silicon wafer with small crystal grains can be obtained, and the improvement of the nitriding degree of silicon crystals is facilitated. After surface nitridation and sintering of the silicon wafer blank, the high-thermal-conductivity silicon nitride ceramic wafer is formed, and a new idea is provided for production of the silicon nitride ceramic wafer.
While the preferred embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that the invention is not limited thereto, and that various changes and modifications may be made without departing from the spirit of the invention, and the scope of the appended claims is to be accorded the full scope of the invention.
Claims (9)
1. A preparation method of silicon nitride ceramics is characterized by comprising the following steps,
s1) polycrystalline silicon ingot casting: directionally solidifying a polycrystalline silicon ingot by adopting a silicon powder nucleation method, uniformly mixing 80-95 wt% of high-purity silicon powder, 1-10 wt% of magnesium-containing powder and 1-10% of rare earth element powder, then loading the mixture into a quartz crucible with a quartz sand nucleation layer sprayed at the bottom, loading the mixture into an ingot casting hearth, and controlling the cooling rate after ingot casting to form a superfine microcrystalline polycrystalline silicon ingot with the grain size of 0.5-100 mu m;
s2) preparing a polycrystalline silicon wafer: cutting the silicon ingot in the S1 into a polycrystalline silicon slice with the thickness of 0.1mm-1 mm;
s3) silicon wafer nitriding: stacking polycrystalline silicon wafers in a sintering furnace, separating the silicon wafers by using graphite plates with BN coatings, vacuumizing, nitriding in a nitrogen atmosphere at the nitriding temperature of 1350-1400 ℃, at the heating rate of 20-100 ℃/h and at the heat preservation time of 1-12 h, and cooling along with the furnace;
s4) sintering the silicon wafer blank: the silicon wafer blank subjected to nitriding sintering and the jig are placed in a sintering furnace, and sintering is carried out at the sintering temperature of 1700-1900 ℃ and the nitrogen pressure of 0.5-20 MPa in a nitrogen atmosphere.
2. The method for producing a silicon nitride ceramic according to claim 1, wherein:
wherein, in step S1, the magnesium-containing powder is Mg powder, MgO powder, MgSiN2Powder, SiMg2Any one or more of the powders;
the rare earth element powder is any one or mixture of more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, scandium and oxide powder thereof.
3. The method for producing a silicon nitride ceramic according to claim 1, wherein:
in step S1, the cooling rate is controlled to be 10-40 ℃/h after ingot casting.
4. The method for producing a silicon nitride ceramic according to claim 1, wherein:
in the step S1, an ultrasonic generator is arranged at the bottom of the ingot furnace body and is started at the initial stage of silicon material cooling and nucleation, the running power of the ultrasonic generator is 800w-1200w, the frequency is 15-25kHz, and the starting time is 5-10 min.
5. The method for producing a silicon nitride ceramic according to claim 1, wherein:
in step S1, the thickness of the quartz sand nucleation layer sprayed on the bottom of the quartz crucible is 0.2mm-0.8mm, and the particle size of the quartz sand is 20 μm-80 μm.
6. The method for preparing silicon nitride ceramics according to claim 1, characterized in that:
in step S2, the silicon ingot is cut, ground radially, and cut by a diamond wire to obtain the polycrystalline silicon wafer.
7. The method for producing a silicon nitride ceramic according to claim 1, wherein:
in step S3, the furnace body is first vacuumized to the vacuum degree of 0.1-0.01 Pa, and high-purity N is then introduced2And H2Then the temperature of the mixed gas is raised, and the gas pressure is kept between 0.03MPa and 2 MPa.
8. The method for producing a silicon nitride ceramic according to claim 7, wherein:
wherein, in the mixed gas, H2Is 5% by volume.
9. The method for producing a silicon nitride ceramic according to claim 7, wherein:
in the step S4, the sintering heat preservation time of the silicon wafer blank is 2-20 h, and the heating rate is 20-100 ℃/h.
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