Methods of purifying silicon

Abstract

The invention discloses a method for purifying silicon. The method comprises the steps: firstly, melting crude silicon and high-purity metal capable of forming hypereutectic or hyperperitectic with silicon in a crucible in which a temperature directional control tube is arranged; high lateral and longitudinal temperature gradients are generated by utilizing a temperature directional control tube,and the crystallization process of the primary monatomic silicon in a hypereutectic alloy system is controlled by combining a traveling wave magnetic field, so that the stability of a growth interfaceof the primary monatomic silicon is improved, and the formation of fluxing metal inclusions is inhibited. Firstly, the prepared bar is of a structure that the primary monatomic silicon is located inthe center and the fluxing metal is located on the outer side. Then, supersaturated dissolution of silicon is realized in a top high-temperature region, and coarsening growth of the central primary monatomic silicon rod is realized by virtue of reciprocating motion of a traveling wave magnetic field generator; and after the growth is finished and cooling is performed, the head metal gettering areais cut off. The process is repeated again on the obtained primary silicon to prepare the high-purity silicon. Therefore, according to the method, introduction of a large number of metal inclusions can be avoided, the process is simple, and the prepared silicon is high in purity.

Description

technical field [0001] The invention relates to the technical field of semiconductor silicon, in particular to a method for purifying silicon. Background technique [0002] With the depletion of petroleum energy, solar energy as an inexhaustible clean energy has attracted the attention of countries all over the world, and solar-grade silicon materials are the basis for preparing solar cells. The metallurgical method is a method of preparing solar-grade polysilicon, which is economical, simple in process and less polluting to the environment. Therefore, it has become the best method for preparing solar-grade silicon materials. It can quickly remove metal impurities from silicon, and then pass through regional smelting , Electron beam high-temperature vacuum smelting can effectively remove elements with high saturated vapor pressure, such as phosphorus. [0003] Traditionally, directional solidification is mainly used to purify polysilicon by metallurgy. However, due to the a...

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Problems solved by technology

[0003] Traditionally, directional solidification is mainly used to purify polysilicon by metallurgy. However, due to the addition of metallurgical elements, the solidification temperature interval of primary silicon is greatly increased. Ordinary directional solidification devices can easily destabilize the growth interface and introduce a large number of metal inclusions. Therefore, the corresponding inclusions must be removed by polysilicon crusher pickling and other processes in the follow-up

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