Method for preparing polycrystalline silicon by physically removing boron

Abstract

The invention relates to a method for removing a boron element from silicon, which comprises the following steps of: (1) selecting high-quality silicon generally based on 2202-qualtiy silicon; (2) weighing a certain amount of silicon, and adding the silicon into a refining furnace for refining; (3) heating the refining furnace by electricity to fully melt the silicon; (4) weighing an alkali slag forming agent in a total weight ratio of the alkali slag forming agent to the silicon of 1:!-1:5; (5) dividing the weighed alkali slag forming agent into 10 equal parts, adding the alkali slag forming agent into the refining furnace by 10 times, filtering the surface slag liquid when smelting once every one hour, and repeatedly adding the agent into the refining furnace to smelt the filter slag for 10 times; and (6) preparing a directional pouring container with a micropore filter device, pouring the silicon liquid into the directional container through the micropore filter device to perform directional cooling, detecting the boron content of less than 0.4PPm, and preparing the low-boron high-purity silicon. The method has the advantages of simple process, simple and convenient operation, low energy consumption and no pollution discharge.

Description

technical field [0001] The invention relates to a method for physically removing boron to prepare polysilicon. Background technique [0002] With the continuous increase of global energy consumption, conventional non-renewable energy can no longer meet the supply and demand of most countries. According to the analysis of the world's energy authorities, based on the current proven fossil energy reserves and mining speed, the remaining recoverable life of global oil is only 40 years, the remaining recoverable life of natural gas is 60 years, and the remaining recoverable life of coal is 120 years. On the other hand, the exploitation and application of primary energy is also an important cause of ecological damage and global environmental pollution. Therefore, the development and use of renewable new energy is a necessary condition for the long-term development of human beings, and it is also the fundamental method of our sustainable development. [0003] The new energy photo...

AI Technical Summary

Problems solved by technology

The requirement for solar grade polysilicon is that the total impurity content is less than 1ppm, that is, 6N, especially the requirements for the content of P and B elements are very strict (B<0.4ppm, P<0.7ppm). During the purification process, the two elements of P and B are due to The particularity of its chemical properties, meeting the requirements of solar-grade polysilicon brings great difficulties to the process