Silicon refining method and refining device

Abstract

The improvement of the production efficiency of high-purity silicon produced from silicon having metal-grade purity and the reduction of heat energy are achieved. After first treatment which is either a step for removing boron by oxidation and oxide thereof by evaporation by bringing silicon into a high-temperature molten metal state by performing steam addition plasma arc heating or low-pressure oxygen plasma arc heating on a silicon starting material housed in a hearth inside a chamber or a step for removing phosphorous by evaporation by bringing silicon into a high-temperature molten metal state by electron beam irradiation while a vacuum atmosphere suitable therefor is maintained in the chamber, refining treatment is performed on the silicon housed in the hearth in the same chamber while the atmosphere in the chamber is changed to a vacuum atmosphere suitable for second treatment which is the remaining step while the molten metal state is maintained. Thereafter, a high-purity refined silicon ingot from which phosphorous, boron, and other impurities are highly removed by cutting the end thereof at which impurities are concentrated by a unidirectional solidification method is obtained.

Description

technical field [0001] The present invention relates to a method and device for refining silicon, in particular to a method and device for producing high-purity silicon by removing impurities such as phosphorus and boron with high efficiency and high yield according to metallurgical methods. Background technique [0002] High-purity silicon is used in semiconductor devices and solar cells, but it is very difficult to refine the high-purity silicon required for these applications. To meet such high purity requirements, the refining process should not only have high production efficiency, but also have high yield. [0003] The purity requirement for silicon for solar cells (Solar Grade Silicon: SOG-Si) is Si: 99.9999% (6N) or higher, although the purity requirement for Si used in semiconductor equipment: 99.999999999% (11N) is relatively lower, but cost reduction is considered to be a major subject. [0004] The raw material of silicon used for these purposes is commercially...

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Problems solved by technology

[0035] However, to switch the above-mentioned atmosphere in such a short time, it is necessary to switch from the high vacuum of the dephosphorization process to the atmosphere suitable for plasma spraying, and from the atmosphere of plasma spraying to high vacuum, especially for suction to high vacuum. Generally known vacuum pumps that can achieve such a high vacuum degree require tens of minutes even if a vacuum system that uses a turbomolecular pump or Roots pump as an auxiliary pump and a front pump such as a rotary pump is used. , even if the capacity of these vacuum pumps is increased, it cannot be achieved in a short time to the extent that the above-mentioned continuous refining process can be carried out

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