Method for removing boron and phosphorus and purifying industrial silicon by using metallurgic method

Abstract

The invention discloses a method for removing boron and phosphorus and purifying industrial silicon by using a metallurgic method. The method comprises the steps: (1) placing industrial silicon blocks in the vacuum environment to be heated till the silicon blocks are melted, keeping the temperature for 40-80 minutes so as to refine the silicon blocks; (2) leading protective atmosphere containing oxygen and steam to in the vacuum environment in the step (1) to enable the oxygen and the steam in the protective atmosphere to be fully reacted with impurities in the silicon blocks; and (3) reducing the temperature of the environment in the step (2) till the silicon blocks are in a solid state to obtain silicon ingots, and cutting off slag layers of the silicon ingots. By means of the method, various models of industrial silicon can be purified, samples are not required to be subjected to crushing and ball milling, only simple crushing is required, and the requirement for sample size is low. The method does not comprise any acid-washing steps, usage of a great quantity of strong corrosive acid is avoided, the process if simplified, and the cost is reduced. The impurities including phosphorus, arsenic, antimony, calcium and the like can be removed so as to meet the requirements of solar grade silicon by means of the process. The boron is reduced to be 1.5-0.3 ppmw, and the standard of the solar grade silicon is met.

Description

technical field

[0001] The invention relates to a method for purifying industrial silicon by removing boron and phosphorus through a metallurgical method. Background technique

[0002] With the increasing shortage of energy in the world and the improvement of environmental protection awareness, the demand for solar photovoltaic conversion cells and their main materials is increasing. The purification technology of high-purity polysilicon (solar-grade silicon 6N), which is used as a solar photovoltaic material, has also attracted worldwide attention. The cost of polysilicon accounts for 60% of the cost of solar cells. The vast majority of domestic enterprises still produce polysilicon by the Siemens method with high energy consumption and high pollution. Although the Siemens method has high product purity (11N), the production equipment is complicated, the efficiency is low, and the investment is huge, the energy consumption is high, and the release of chlorine gas endangers...