CN-121992372-A - High-purity silicon chemical vapor deposition system and method based on composite ceramic lining

CN121992372ACN 121992372 ACN121992372 ACN 121992372ACN-121992372-A

Abstract

The invention provides a high-purity silicon chemical vapor deposition system based on a composite ceramic lining, which comprises a reaction cavity, a heating unit, an air inlet unit, a tail gas treatment unit and a control unit, wherein the reaction cavity comprises a lining made of silicon carbide-hexagonal boron nitride composite ceramic. The method for preparing the high-purity silicon by using the chemical vapor deposition system comprises the steps of surface pretreatment of the lining, establishment of a deposition temperature field, vapor deposition of the silicon and the like. The reaction cavity liner is made of silicon carbide-boron nitride composite ceramic material, so that pollution impurities are not generated, the sealing performance of the working environment inside the reaction cavity can be better maintained, and impurities generated by other metal materials outside the liner are prevented from entering the reaction cavity. In the preparation method, the surface of the lining is pretreated, an atomic-level passivation layer is generated on the reaction surface of the lining in situ, and the cationic impurities in the lining body are prevented from diffusing into gas phase and deposited silicon, so that the effect of reducing the impurities is further achieved.

Inventors

WANG SHENGMING
ZHU DAOQUAN
Fang Dunping
WEI JIANGUO
WU HAN
WU JIANHUA
DU JIAKUN

Assignees

湖北红花高温材料股份有限公司

Dates

Publication Date: 20260508
Application Date: 20260211

Claims (9)

1. The high-purity silicon chemical vapor deposition system based on the composite ceramic lining is characterized by comprising a reaction cavity, a heating unit, an air inlet unit, a tail gas treatment unit and a control unit; The reaction cavity comprises a lining made of silicon carbide-hexagonal boron nitride composite ceramic, the lining forms the whole inner wall surface of the reaction cavity and a base for bearing silicon seed crystals, or only forms the whole inner wall surface of the reaction cavity, and hexagonal boron nitride phases are dispersed and distributed in a silicon carbide matrix in a micron-sized platelet form on the working surface of the lining; the heating unit is a multi-section independent temperature control heater surrounding the reaction cavity, and can form a precisely controlled temperature gradient in the axial direction and the radial direction of the lining; The air inlet unit is used for introducing mixed gas of silane gas and hydrogen into the reaction cavity; the tail gas treatment unit adopts a mode of dust removal and purification to remove silicon particles and harmful gas pollutants contained in tail gas; the control unit is respectively and electrically connected with the reaction cavity, the heating unit, the air inlet unit and the tail gas treatment unit, so that the automatic operation of the whole system is controlled.
2. The composite ceramic liner-based high purity silicon chemical vapor deposition system of claim 1, wherein the liner is prepared by: Mixing silicon carbide micro powder, flaky hexagonal boron nitride powder and a composite sintering aid containing aluminum nitride and yttrium oxide to prepare ceramic slurry, forming a green body according to the shape of a reaction cavity by adopting a direct-writing forming 3D printing technology, performing pre-oxidation treatment on the green body at 800-1000 ℃ in air atmosphere, and finally performing two-stage in-situ reaction sintering at 1400-1600 ℃ and 1850-2000 ℃ in protective atmosphere to form the composite ceramic lining.
3. The high-purity silicon chemical vapor deposition system based on the composite ceramic lining of claim 1, further comprising a surface pretreatment unit communicated with the reaction chamber, wherein the surface pretreatment unit can introduce a pretreatment gas containing a boron source or a nitrogen source into the reaction chamber.
4. The high-purity silicon chemical vapor deposition system based on a composite ceramic liner according to claim 3, wherein the pretreatment gas is diborane and hydrogen gas mixed gas or ammonia gas.
5. The high-purity silicon chemical vapor deposition system based on the composite ceramic lining of claim 1, wherein the tail gas treatment unit comprises a cyclone dust collector, a cryogenic condensing gas-liquid separator, an HCl absorption tower, a PSA hydrogen purification chamber and a combustion alkaline washing tank which are sequentially arranged, dust is removed firstly, cooling, condensation and recovery of chlorosilane are carried out, recycling of raw materials is realized by separating and purifying HCl and high-purity hydrogen, and finally, residual waste gas is combusted and alkaline washing is neutralized.
6. A method of producing high purity silicon using the chemical vapor deposition system according to any one of claims 1 to 5, comprising the steps of: S1, pretreatment of the surface of the lining, namely after a silicon seed crystal is filled into a reaction cavity, sealing the system, vacuumizing, introducing pretreatment gas containing a boron source or a nitrogen source into the reaction cavity, and reacting the pretreatment gas with the working surface of the lining for 0.5-4 hours at 600-900 ℃, so as to generate a passivation layer rich in boron or nitrogen on the surface of the passivation layer in situ; S2, establishing a deposition temperature field, namely switching to a deposition process after pretreatment is finished, heating the lining temperature of the reaction cavity to the deposition temperature through a heating unit, and establishing a required axial temperature gradient in the reaction cavity; And S3, silicon vapor deposition, namely introducing a mixed gas of high-purity silane gas and hydrogen into the reaction cavity, controlling the flow rate and the pressure of the gas to enable silicon crystals to continuously grow, stopping introducing silane after reaching the preset deposition time or the preset silicon ingot size, and performing program cooling in the hydrogen atmosphere to obtain the high-purity silicon ingot product.
7. The method for producing high purity silicon according to claim 6 wherein in step S2, when silane is used as a raw material, the deposition temperature is 1050 to 1150 ℃.
8. The method of producing high purity silicon according to claim 6, wherein in step S2, the top temperature is higher than the bottom temperature in the reaction chamber, and a gradient temperature difference in a range of 50℃is formed, in which the temperature gradually decreases from the top to the bottom, to facilitate vapor phase transport and deposition.
9. The method for producing high purity silicon according to claim 6, wherein in said step S3, the gas flow rate is 45 to 55L/min, and the system pressure is maintained at 0.04MPa to 0.06MPa.

Description

High-purity silicon chemical vapor deposition system and method based on composite ceramic lining Technical Field The invention relates to the technical field of preparing high-purity silicon by vapor deposition, in particular to a high-purity silicon vapor deposition system and method based on a composite ceramic lining. Background The high-purity polysilicon is a semiconductor core material with the purity of more than or equal to 99.9999 percent (6N) and exists in a polycrystalline form, and is divided into an electronic grade (more than or equal to 9N-11N) and a solar grade (more than or equal to 6N), and the core is used for semiconductor chips and photovoltaic cells, and is also a basic raw material of power devices, MEMS sensors and infrared optical elements. The main current technology for preparing high-purity silicon is an improved Siemens method (trichlorosilane reduction) or a silane method, the core principle is that trichlorosilane (SiHCl 3) is rectified and purified, and then 9N+ electronic grade polysilicon can be stably produced through a closed loop process of Chemical Vapor Deposition (CVD) reduction. The currently mainly used apparatus is a chemical vapor deposition reactor, which uses a silicon core (generally elongated rod-like) disposed in a reaction chamber of the reactor to contact with a gas, thereby gradually depositing high purity silicon on the surface of the silicon core. However, during high temperature (typically >1000 ℃) deposition, the reactor liner or carrier can instead become an important source of impurities contaminating the silicon feedstock. The traditional lining material such as high-purity graphite can lead carbon, metal and other impurities into silicon at high temperature due to volatilization of trace impurities, particle exfoliation or reaction with reaction gas, so as to influence the electrical property of the silicon ingot. The quartz glass liner has low strength, poor thermal shock resistance, easy breakage and short service life. The improvements in the prior art are mostly focused on external process parameter optimization (such as airflow field design and heating uniformity) or purification treatment of the deposited silicon material, and belong to passive response. For example, the Chinese patent publication No. CN116282036B discloses a polysilicon cold hydrogenation catalyst recovery and separation device and a polysilicon production system, which can utilize magnetism to efficiently separate the catalyst, reduce the production cost and the impurity content of the product, thereby ensuring the purity and quality of the product. The Chinese invention with publication number of CN112374502B specially proposes a polysilicon cold hydrogenation method adopting a gas-solid parallel flow downer reactor, which eliminates the gas-solid ring core structure of the upgoing fluidized bed reactor, and has the advantages of sufficient and uniform reaction and high efficiency. The silicon powder and the catalyst are less carried out in the reaction, so that the silicon powder is recycled, the utilization rate of the silicon powder is high, and the production amount of slag slurry is greatly reduced. None of these actively intervene from the source of contamination, i.e. the interfacial chemistry of the reactor lining material. Therefore, there is a need for a new reactor liner and associated deposition technique that can radically inhibit impurity migration and can positively affect silicon crystal growth. Disclosure of Invention Aiming at the defects existing in the prior art, the invention provides a high-purity silicon chemical vapor deposition system and a high-purity silicon chemical vapor deposition method based on a composite ceramic lining, which solve the problems that the purity of a product is affected due to the fact that trace impurities volatilize, particles flake off or react with reaction gas in the reactor lining or a carrier in the prior art at high temperature. In a first aspect, the invention provides a high-purity silicon chemical vapor deposition system based on a composite ceramic liner, which comprises a reaction cavity, a heating unit, an air inlet unit, a tail gas treatment unit and a control unit; The reaction cavity comprises a lining made of silicon carbide-hexagonal boron nitride composite ceramic, the lining forms the whole inner wall surface of the reaction cavity and a base for bearing silicon seed crystals, or only forms the whole inner wall surface of the reaction cavity, and hexagonal boron nitride phases are dispersed and distributed in a silicon carbide matrix in a micron-sized platelet form on the working surface of the lining; the heating unit is a multi-section independent temperature control heater surrounding the reaction cavity, and can form a precisely controlled temperature gradient in the axial direction and the radial direction of the lining; The air inlet unit is used for introducing mixed gas of silane gas and hydroge