Method and equipment for purifying polycrystalline silicon by melting in electron beam shallow pool

Abstract

The invention belongs to the field of purification of polycrystalline silicon by adopting a physical metallurgy technology, and discloses a method for purifying polycrystalline silicon by melting in an electron beam shallow pool. The method comprises the following steps of: putting a large high-phosphorus and high-metal polycrystalline silicon ingot needing to be purified on a water-cooled elevating tray; melting the top of the silicon ingot by adopting electron beams; making a molten silicon solution form the shallow pool in a space formed by the top of the silicon ingot, a water-cooled copper sheathing and a graphite ferrule; melting for a certain period of time to remove phosphorus impurity; lifting the water-cooled elevating tray; raising the liquid level of a low-phosphorus silicon melt and making the low-phosphorus silicon melt flow into a quartz crucible through a diversion port; pulling the ingot downwards under the action of heat preservation; performing directional solidification growth; enriching metal impurities towards the top of the silicon ingot; cutting the top of the silicon ingot after solidifying; and removing the metal impurities. By adopting the method, phosphorus and metal impurities in silicon are removed by melting in the electron beam shallow pool and directional solidification, the purity of polycrystalline silicon meets the using requirement of solargrade silicon and energy sources are saved. The method has the advantages of simple process and high production efficiency, and is suitable for batch 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 and metal in polysilicon; in addition, the invention also relates to its equipment. 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 world-wide preparation of polysilicon materials for solar cells has formed large-scale production and the main technical routes under development are: [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 foreign countri...

AI Technical Summary

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. However, most of the current methods for purifying polysilicon by electron beam smelting have the disadvantage of high energy consumption. There is no method of purifying polysilicon by electron beam shallow melting pool smelting

The known invention patent with application number 2008100713986.X uses electron beam melting to achieve the purpose of removing phosphorus in polysilicon, but the raw material used in this patent is silicon round rods, which are not easy to process in actual production, and the water-cooled copper used at the same time The crucible is used as a crystallizer, which consumes a lot of energy

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