Preparation method of polycrystalline silicon

Abstract

The invention provides a preparation method of polycrystalline silicon, and belongs to the technical field of solar silicon wafer preparation. The preparation method is achieved by the following technical scheme: smelting and purifying silica sand to 98% in an electric arc furnace, and generating industrial silicon; crushing the industrial silicon and reacting by using anhydrous hydrogen chloride (HCl) in a fluidized bed reactor, so as to generate trichlorosilane (SiHCl3), wherein the reaction temperature is 300 DEG C, and a gaseous mixture (H2, HCl, SiHCl3, SiCl4 and Si) are formed by reaction; filtering silicon powder from the gaseous mixture; condensing SiHCl3 and SiCl4, returning gaseous H2 and HCl to reaction or discharging into atmosphere, and then decomposing condensates SiHCl3 and SiCl4; and purifying trichlorosilane; and carry out reducing deposition on the purified trichlorosilane with high-purity SiHCl3 in H2 atmosphere by adopting a high-temperature reduction process, thereby generating polycrystalline silicon. The preparation method of the polycrystalline silicon has the advantages of significant energy conservation and consumption reduction, low cost and good quality; by adopting a comprehensive utilization technique, the environment is not polluted; and the method has obvious competitive advantages.

Description

technical field [0001] The invention belongs to the technical field of making solar silicon chips, and in particular relates to a method for making polysilicon. Background technique [0002] Polysilicon is refined from metallurgical grade silicon with low silicon purity. Since the main and auxiliary raw materials used in each polysilicon production plant are not the same, the production process technology is different; and the corresponding technical and economic indicators, product quality indicators, uses, and products of polysilicon products There are also differences in detection methods and process safety, each with its own technical characteristics and technical secrets. Generally speaking, the main traditional processes for polysilicon production in the world at present are: improved Siemens method, silane method and fluidized bed method. The improved Siemens method is currently the mainstream production method, and the polysilicon produced by this method accounts for...

AI Technical Summary

Problems solved by technology

[0003] In the next 15-20 years, the investment for polysilicon production using the improved Siemens process will exceed US$100 billion. The production of solar-grade polysilicon will still be dominated by the improved Siemens process. The improved Siemens process is still the most mature, reliable, and The process with the fastest production speed is in a long-term competitive state with other types of production processes, and it is difficult to replace each other