Method and device for removing foreign matter phosphor in polysilicon

Abstract

The invention relates to a method for removing impurity phosphor from polysilicon and a device thereof, in particular to a method for removing impurity phosphor from polysilicon by electronic torch melting technology and the device thereof, which belongs to the technical field of purifying polysilicon by physicometallurgy technology. The method is characterized in that polysilicon can be fully melted by the dual electron beams while water cooled copper crucible is rotated, polysilicon can be added in the melting process to realize continuous operation, thus removing the impurity phosphor frompolysilicon. Polysilicon is put into the water cooled copper crucible, the cover of a vacuum apparatus is closed; and then the water cooled copper is vacuumized, a left electron gun and a right electron gun are preheated. The shell of the device consists of a vacuum apparatus cover and a vacuum drum, the internal cavity of the vacuum drum is a vacuum chamber. The harmful impurity phosphor in polysilicon is thoroughly removed by the electron beam melting, which effectively improves the purity of polysilicon and realizes the continuous operation. The method has high efficiency; the device is simple and saves energy.

Description

Technical field [0001] The invention belongs to the technical field of purifying polysilicon by physical metallurgy technology, and particularly relates to a method and device for removing impurity phosphorus in polysilicon by using electron beam melting technology. Background technique [0002] High-purity polysilicon is the main raw material for preparing solar cells. The preparation of high-purity polycrystalline silicon abroad mainly uses the Siemens method, specifically the silane decomposition method and the chlorosilane gas-phase hydrogen reduction method, among which SiHCl 3 The Siemens method is currently the mainstream technology for polysilicon preparation. SiHCl 3 The useful deposition ratio of the method is 1×10 3 , Is SiH 4 100 times. The deposition speed of Siemens method can reach 8-10μm / min. The conversion efficiency of one pass is 5%-20%, and the deposition temperature is 1100℃, second only to SiCl 4 (1200℃), the power consumption is about 120kWh / kg, and the p...

AI Technical Summary

Problems solved by technology

The disadvantage of the Siemens method is that it adopts backward thermal chemical vapor deposition in the core link of the process. There are too many links in the process and the conversion rate is low at one time, which leads to a long process time and increases the cost of materials and energy consumption.

The simple directional solidification method cannot remove the impurity phosphorus with a large segregation coefficient. Among the many impurities in polysilicon, phosphorus is a harmful impurity, which directly affects the resistivity and minority carrier lifetime of silicon materials, and then affects the performance of solar cells. Photoelectric conversion efficiency

The phosphorus content of polycrystalline silicon that can be used to prepare solar cells is required to be reduced to below 0.0001%. It is known that the invention patent of Japanese Patent No. 11-20195 uses electron beams to achieve the purpose of removing phosphorus in polycrystalline silicon, but the disadvantage of this invention is that electron beams can only Remove impurities on the surface of liquid silicon, because the solution cannot be stirred and turned over, the effect of removing impurities inside the solution is not obvious

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