Method for removing metallic impurities in solar-grade polysilicon

A solar-grade, polysilicon technology, applied in non-metallic elements, chemical instruments and methods, silicon compounds, etc.

Inactive Publication Date: 2012-04-25
山西纳克太阳能科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This causes a waste of silicon material, and the yield rate of purified solar-grade polysilicon is greatly reduced

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0031] A graphite crucible capable of containing 200 kg of metallic silicon raw material was used, and 200 kg of raw metallic silicon with a metal impurity concentration of 700 ppm was weighed.

[0032] Turn on the front-stage mechanical pump and high-performance diffusion pump of the vacuum system in turn to pump the furnace chamber to a vacuum of 1.2×10 －3 Pa. Start to feed 20kg of metal silicon into the graphite crucible through the feeding device, turn on the high-frequency power supply to heat the silicon to melt, the melt temperature is controlled at 1500°C, and the power is 200KW.

[0033] Turn on the continuous feeding device and put the remaining metal silicon raw materials into the crucible until the volume of the silicon melt reaches 3 / 4 of the volume of the graphite crucible, then start the continuous rod pulling device, and the entire demetallization process takes 16 hours. After the silicon ingot was cooled, a sample was taken from it for detection, and the meta...

Embodiment 2

[0035] The process is the same as in Example 1, and 200 kg of raw metal silicon with a metal impurity concentration of 700 ppm is weighed. A graphite crucible capable of holding 200kg of silicon material is used. Turn on the front-stage mechanical pump and high-performance diffusion pump of the vacuum system in turn to pump the vacuum in the furnace chamber to 2.0×10 －3 Pa. Start to feed 20kg of metal silicon into the graphite crucible through the feeding device, turn on the high-frequency power supply to heat the silicon to melt, the melt temperature is controlled at 1600°C, and the power is 220KW. Turn on the continuous feeding device to put the raw metal silicon into the crucible until the volume of the silicon melt reaches 3 / 4 of the volume of the graphite crucible, and the entire demetallization process takes 20 hours. After the silicon ingot was cooled, a sample was taken from it for testing, and the metal content was 0.03ppm.

Embodiment 3

[0037] The technological process is the same as in Example 1, and the metal impurity concentration in the silicon material is 700ppm and 300kg of raw metal silicon. A graphite crucible capable of holding 300kg of silicon material is used. Vacuum the furnace chamber to 1.0×10 －3 Pa. The melt temperature is controlled at 1650°C, and the power is 240KW. It takes 24 hours to complete the demetallization process. After the silicon ingot was cooled, a sample was taken from it for testing, and the metal content was 0.01ppm.

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Abstract

The invention provides a method for removing metallic impurities in solar-grade polysilicon. The invention is characterized by comprising the following process steps: (1) selecting the raw material of metallic silicon with a particle size of 5 to 100 mm and a purity of more than 99%, wherein, the content of metallic impurities in metallic silicon is 700 ppm; (2) starting a vacuum system of a highvacuum induction furnace; (3) filling metallic silicon into a graphite crucible located in the high vacuum induction furnace, wherein metallic silicon occupies 1 / 10 of the volume of the graphite crucible, and turning on a high frequency induction power supply so as to melt metallic silicon; (4) after metallic silicon is melt, maintaining the temperature of molten silicon at 1560 to 1600 DEG C, and adding rest metallic silicon into the graphite crucible in the furnace for fusion so as to obtain silicon melt; (5) when the volume of the silicon melt is 3 / 4 of the volume of the crucible, startingan oriented pull rod device, removing metallic impurities in silicon through oriented drawing, and allowing a silicon rod to be formed; (6) cutting off a silicon rod tail in which impurities assembleso as to obtain polysilicon that has undergone removal of metallic impurities and purification. Low cost is achieved in the invention.

Description

technical field [0001] The invention relates to a method for removing metal impurities from solar-grade polysilicon, in particular to a purification method for removing metal impurities from polysilicon by using directional drawing rods. Background technique [0002] Energy shortage and environmental pollution are two major problems facing the current economic development, restricting economic and social development. The reserves of conventional fossil fuel resources in the earth are limited. With large-scale process mining and increasing energy consumption demand, global fossil fuel resources are being depleted at an accelerated rate, and the whole world is facing enormous pressure from the depletion of fossil energy resources. [0003] And the inexhaustible and inexhaustible solar energy will become the important energy source of our country in the middle of this century. As the most potential energy source in the 21st century, the solar energy industry has great develop...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/037
Inventor 孔繁敏安利明孙湘航王新元司继良徐民
Owner 山西纳克太阳能科技有限公司
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