Method for purifying polycrystalline silicon by directional solidification and slag refining

A directional solidification, refining and purification technology, applied in the direction of self-solidification, polycrystalline material growth, chemical instruments and methods, etc., can solve the problems of silicon slag melt disturbance, difficult to meet the requirements of industrialization, and the results are not very ideal. Good effect, effective removal, simple effect

Inactive Publication Date: 2011-10-19
DALIAN UNIV OF TECH
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  • Application Information

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Problems solved by technology

Japan's Morita et al. did a systematic study on slagging smelting, and concluded that the main factors affecting the distribution coefficient are the basicity of the slag agent, the partial pressure of oxygen and the distribution of B in the melt, but the results are not very good. Ideal, difficult to meet the requirements of industrialization
[0005] A method for preparing solar-grade silicon with a patent number of 200810068908.0 and a metallurgical met...

Method used

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  • Method for purifying polycrystalline silicon by directional solidification and slag refining
  • Method for purifying polycrystalline silicon by directional solidification and slag refining

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Embodiment 1

[0020] First, take a polysilicon block with a boron content of 0.001% and a total metal content of 0.05%, wash it with deionized water for 5 times, put it in a drying oven and dry it at 60°C, take 500g of the dried polysilicon block and 500g of acid Slagging agent SiO 2 -CaO-Na 2 CO 3 Mix evenly according to the slag-silicon ratio of 1 to form a mixture, in which the acidic slagging agent SiO 2 -CaO-Na 2 CO 3 The mass percentage of each component is SiO 2 80%, CaO15% and Na 2 CO 3 5%;

[0021] Then slowly pour the mixture into the graphite crucible in the directional solidification furnace, close the furnace cover, turn on the mechanical pump to evacuate to 800Pa, then turn on the Roots pump to evacuate to 3Pa, and open the upper, side and lower three parts of the directional solidification furnace A graphite heating element, and keep the power of the three heating elements the same, start heating up, when the temperature rises to 1200 ° C, flow argon gas protection, h...

Embodiment 2

[0024] First, take a polysilicon block with a boron content of 0.0015% and a total metal content of 0.06%, wash it with deionized water for 5 times, put it in a drying oven and dry it at 60°C, take 500g of the dried polysilicon block and 600g of acid Slagging agent SiO 2 -CaO-Na 2 O is uniformly mixed according to the slag-silicon ratio of 1.2 to form a mixture, in which the acidic slagging agent SiO 2 -CaO-Na 2 The mass percentage of each component of O is SiO 2 60%, CaO25% and Na 2 O15%;

[0025] Then slowly pour the mixture into the graphite crucible in the directional solidification furnace, close the furnace cover, turn on the mechanical pump to evacuate to 800Pa, then turn on the Roots pump to evacuate to 3Pa, and open the upper, side and lower three parts of the directional solidification furnace A graphite heating element, and keep the power of the three heating elements the same, start heating up, when the temperature rises to 1200 ° C, flow argon protection, hea...

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Abstract

The invention belongs to the technical field of purifying polycrystalline silicon by physical metallurgy technology. A method for purifying polycrystalline silicon by directional solidification and slag refining comprises the following steps: firstly, mixing polycrystalline silicon material and acid slag former uniformly so as to form mixture, then arranging the mixture into a melting crucible ofa directional solidification furnace, slagging and melting the mixture in the melting crucible, simultaneously, conducting directional solidification so as to concentrate metal impurity and waste slag on the top of a silicon ingot, removing boron and metal impurity, and finally cutting the top of the silicon ingot, thus obtaining polycrystalline silicon ingot with low boron and metal content. Themethod has the following obvious effects: the acid slag former for slagging and melting and the directional solidification are adopted simultaneously, the impurity boron in the polycrystalline silicon is removed by the slagging of the acid slag former and the refining, simultaneously, the metal impurity with a smaller segregation coefficient in the polycrystalline silicon is removed by the directional solidification technology, the purity of the polycrystalline silicon material is improved, so that polycrystalline silicon material achieves the using requirement of solar-level polycrystalline silicon material.

Description

technical field [0001] The invention belongs to the technical field of purifying polysilicon by using physical metallurgy technology, and particularly relates to a method for removing boron and metal impurities in polysilicon by using directional solidification technology for slagging and smelting. Background technique [0002] In a society where energy is scarce and low-carbon environmental protection is advocated, solar energy, as an environmentally friendly new energy, has great application value. In recent years, the global solar photovoltaic industry has grown rapidly, and the output of solar cells has increased rapidly, directly driving the rapid expansion of solar polysilicon demand. [0003] At present, the methods of purifying solar polysilicon mainly include chemical purification and physical purification. The chemical purification is mainly the Siemens method. Its advantages lie in high product purity and good quality. Harmful gas will be produced. Metallurgy is...

Claims

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Application Information

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IPC IPC(8): C01B33/037C30B11/00C30B28/06C30B29/06
Inventor 谭毅许富民张磊胡跟兄
Owner DALIAN UNIV OF TECH
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