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Method for removing boron impurities in silicon

A technology of boron impurities and silicon powder, which is applied in the field of high-purity silicon preparation, can solve the problems of high cost, long production cycle, and environmental pollution, and achieve the effects of low cost, short reaction time, and small environmental pollution

Inactive Publication Date: 2009-10-28
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Boron removal effect-6 wt%, that is 0.01ppmw, but the cost is high, the production cycle is long, the technology is relatively perfect, and there is environmental pollution

Method used

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  • Method for removing boron impurities in silicon

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0012] Example 1: Weighing 10g of industrial silicon powder with a particle size of 0.044mm and a boron content of 5×10 -4 Wt%, that is 5ppmw, add 0.5g of the variable valence compound CuS with a purity of 99.999wt%, the weight ratio of the proportion is silicon: CuS = 20:1, grind in a mortar for 3 minutes and mix, and then press and shape under a pressure of 10MPa Put it into the furnace, pass argon gas into the furnace, slowly raise the temperature to 1000°C and keep it for 2 hours, then cool with the furnace. The boron content in the sample was analyzed, and the result B content was 0.48×10 -4 wt%, ie 0.48ppmw.

Embodiment 2

[0013] Example 2: Weighing 20g of industrial silicon powder with a particle size of 0.044mm and a boron content of 5×10 -4 wt%, that is, 5ppmw, adding the valence compound FeCl with a purity of 99.999wt% 3 2g, the weight ratio of proportioning is silicon: FeCl 3 = 10:1, grind together in a mortar for 2.5 minutes and mix thoroughly, press and form under 15MPa pressure, put it into the furnace, feed argon gas into the tube furnace, slowly raise the temperature to 950°C and keep it warm for 1 hour Cooling with the furnace, the analysis result shows that the B content in silicon is 0.12×10 -4 wt%, ie 0.12ppmw.

Embodiment 3

[0014] Embodiment 3: weighing 40 g of head and tail material after directional solidification of polysilicon, boron content 5×10 -4 wt%, ie 5ppmw, add the variable valence compound VF with a purity of 99.999wt% 3 20g, the weight ratio of proportioning is silicon: VF 3 = 2:1, grind together in a mortar for 10 minutes and mix thoroughly, press and form under 10MPa pressure, put it into the furnace, feed argon into the tube furnace, slowly raise the temperature to 900°C and keep it warm for 5 hours, then Furnace cooling, B content in silicon is 0.21×10 -4 wt%, ie 0.21ppmw.

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Abstract

The invention relates to a method for removing boron impurities in silicon. The method comprises the following steps: industrial silicon and waste materials containing boron are taken as raw materials, any one of sulphide (CuS), chloride (CrCl3, FeCl3) and fluoride (VF3) value-variable compounds is added into silicon powder according to the weight ratio between silicon and additive of 80:1 to 2:1, and after grinding and forming, the mixture reacts for 0.5-8 hours under the protection of argon atmosphere and the condition that the temperature is 600-1600 DEG C; the added compound and boron impurities in silicon react to generate a gaseous compound, namely, boron sulfide, boron chloride or boron fluoride which is volatized and removed; and later, a furnace is cooled. The content of B in the industrial silicon and silicon waste materials containing boron is reduced to be lower than 5 multiplied by 10 weight percent, namely, 0.5ppmw, thereby reaching the requirements on boron impurities in solar-grade polysilicon.

Description

1. Technical field [0001] The invention relates to a method for removing impurity boron in industrial silicon by using a variable-valence compound to make it meet the boron content requirement of solar-grade silicon, and belongs to the technical field of high-purity silicon preparation. 2. Background technology [0002] Since the beginning of the 21st century, with the rapid growth of industrial silicon consumption, the annual consumption of industrial silicon in the world has reached more than 1.5 million tons, so the demand for high-purity silicon is also increasing. At present, solar-grade silicon cells (B impurity content <1×10 -4 wt%, that is, 1ppmw), the raw material does not have an independent supply system, but comes from semiconductor grade silicon (B impurity content <1×10 -6 wt%, ie 0.01ppmw), which can no longer meet the needs of the development of the solar cell industry, and the supply of raw materials has become one of the bottlenecks in the developmen...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/037
Inventor 马文会伍继君王烨杨斌谢克强刘大春周阳魏奎先秦博梅向阳汪镜福戴永年
Owner KUNMING UNIV OF SCI & TECH