Method and device for smelting and purifying polysilicon by using electron beams and adopting slag filtering

Abstract

The invention belongs to the technical field of polysilicon purification adopting the physical metallurgy technology and provides a method for smelting and purifying polysilicon by using electron beams and adopting slag filtering. The method comprises the following steps: heating and melting a slag former in a melting crucible to form slag former melt, keeping the liquid state of the slag former melt while adding a high-phosphorus, high-boron and high-metal polysilicon material in a water cooled copper crucible by a charging device, melting the silicon material into silicon melt under the bombardment of the electron beams, removing impurity phosphorus through smelting; and leading the obtained low-phosphorus silicon melt to enter the slag former melt, removing the impurity boron by reacting the impurity boron of the silicon melt with the slag former in the fusing process, heating the melt in the melting crucible and keeping liquid smelting for 3-10 minutes after charging, performing directional solidification, and cutting the top waste residue of the silicon ingot and the high metal content silicon briquet to obtain the polysilicon product. The method comprehensively utilizes the technologies of electron beam smelting dephosphorization, slag filtering smelting boron removal and directional solidification metal removal to remove phosphorus, boron and metal impurities in polysilicon, thus the purification effect is good, the production efficiency is high and the method is suitable for mass production.

Description

technical field [0001] The invention belongs to the technical field of purifying polysilicon by physical metallurgy technology, and particularly relates to a method for removing impurity phosphorus, boron and metal in polysilicon; in addition, the invention also relates to the equipment thereof. Background technique [0002] Solar-grade polysilicon material is an important raw material for solar cells. Solar cells can convert solar energy into electrical energy. In today's shortage of conventional energy sources, solar energy has great application value. At present, the preparation of polysilicon materials for solar cells has formed a large-scale production worldwide, and the main technical routes are as follows: [0003] (1) Improved Siemens method: The Siemens method uses hydrochloric acid (or hydrogen, chlorine gas) and metallurgical grade industrial silicon as raw materials to perform hydrogen reduction from trichlorosilane. Now the relatively mature technology in forei...

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Problems solved by technology

However, the improved Siemens method and silane method require large equipment investment, high cost, serious pollution, and complicated processes, which are not conducive to the popular application of solar cells. In comparison, the metallurgical method has the characteristics of short production cycle, low pollution, and low cost. The focus of R&D in various countries

Electron beam smelting is one of the important methods for metallurgical purification of polysilicon. It can effectively reduce the impurity phosphorus in polysilicon, but most of the methods for purifying polysilicon by electron beam smelting cannot effectively remove boron and metal impurities in polysilicon at the same time, and Generally, electron beam smelting uses two electron guns, which has the disadvantage of high energy consumption.

The known invention patent with application number 2008100713986.X uses electron beam melting to achieve the purpose of removing phosphorus in polysilicon, but the method used in this patent cannot effectively remove impurity boron in polysilicon, and requires additional processes to remove impurity boron, increasing process links, and at the same time, the method used in this patent uses two electron guns, which consumes a lot of energy

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