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Method for purifying polysilicon by using silicon and tin alloy

A polysilicon and alloy technology, which is applied in the field of purifying polysilicon by using silicon-tin alloy, can solve the problem of no separation, etc., and achieve the effects of convenient operation, fast start-up, and small initial investment.

Inactive Publication Date: 2012-12-12
XIAMEN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Obinata et al. (6, Obinata I, Komatsu N.A study on purification of metal allur2 gicalgrade silicon by Si2Al alloy[J]. Sci Rep RITU, 1957, A29: 118-119) used aluminum as a solvent metal to refine industrial silicon, but he The process of using aluminum as a solvent is usually mixed with aluminum oxide, and this oxide is not well separated by pickling and other processes.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0017] 1) Mix industrial silicon and tin powder in a mass ratio of 9:1 and put them into a graphite crucible. When charging, first fill the bottom of the crucible with silicon material, then put tin powder in, and then fill the upper part with silicon material;

[0018] 2) Put the graphite crucible into the directional solidification furnace, then evacuate the solidification furnace, control the vacuum degree to 0.5Pa, raise the temperature in the furnace to 1480°C within 2.5 hours, melt the industrial silicon and tin powder in the graphite crucible, When the temperature rises to 100°C, a pre-prepared protective gas with a suitable ratio is introduced: Ar (99.999%) + water vapor (2ppm) + O 2 (1ppm)+N 2 (4ppm), to normal pressure;

[0019] 3) Insulate the fused industrial silicon and tin powder in step 2) for 3 hours to ensure that it fully melts and melts with silicon and tin melt to form an alloy;

[0020] 4) Cool the alloy in step 3) to 1200°C at a cooling rate of 10°C / h u...

Embodiment 2

[0023]Raw material and technological process are with embodiment 1. The amount of tin powder added is 20%, the vacuum degree in the directional solidification furnace is 0.6Pa, the melting temperature is 1490°C, and the heating time is 3h. When the temperature rises to 200°C, gas is introduced. The holding time at the melting temperature is 3.5h. When cooling and solidifying, the temperature drops to 1250°C, and the cooling rate is 20°C / h. The lower 10% of the obtained alloy silicon ingot is cut off and passed through a plasma inductively coupled mass spectrometer (ICP-MS). ) measured the P content in this polysilicon to be 0.08ppmw, the B content to be 0.3ppmw, and the purity of the polysilicon to be 99.99937%.

Embodiment 3

[0025] Raw material and technological process are with embodiment 1. The amount of tin powder added is 30%, the vacuum degree in the directional solidification furnace is 0.7Pa, the melting temperature is 1580°C, and the heating time is 4.5h. When the temperature rises to 300°C, gas is introduced. The holding time at the melting temperature is 5h. When cooling and solidifying, the temperature drops to 1300°C, and the cooling rate is 30°C / h. The lower 20% of the obtained alloy silicon ingot is cut off and passed through a plasma inductively coupled mass spectrometer (ICP-MS). It was determined that the P content in the polysilicon was 0.05 ppmw, the B content was 0.4 ppmw, and the purity of the polysilicon was 99.99942%.

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Abstract

The invention provides a method for purifying polysilicon by using a silicon and tin alloy and belongs to the field of metallurgy. The method comprises the following steps of: mixing tin powder and industrial silicon, and adding the mixture into a graphite crucible; placing the graphite crucible with the tin powder and the industrial silicon into a directional solidification furnace, vacuumizing the solidification furnace, raising the temperature in the solidification furnace to be between 1,480 and 1,600 DEG C, introducing a protective gas and adjusting the pressure of the solidification furnace, preserving heat of the melted tin powder and industrial silicon at the temperature of between 1,480 and 1,600 DEG C for 3 to 5 hours, reducing the temperature of the alloy melt which is subjected to heat preservation to solidify the alloy melt to obtain a silicon material; and cutting off the 5 to 30 percent of the lower part of the obtained silicon material to obtain the solar-grade polysilicon. The industrial silicon and the tin powder are mixed according to a proportion, melted, subjected to heat preservation and cooled at different cooling speeds to form an alloy; and after the alloyis separated from pure silicon, the separation ratio is measured. Equipment and process flows are simple, volume is small, and the method is convenient to operate, low in cost and wide in market prospect.

Description

technical field [0001] The invention relates to a method for purifying polysilicon, in particular to a method for purifying polysilicon by using a silicon-tin alloy. Background technique [0002] Global energy is gradually tense, and traditional energy such as coal, oil, and natural gas is in short supply, and the pollution is serious. Photovoltaic energy, with its clean, safe, and sustainable use, has become the most competitive energy in the future while alleviating the energy crisis. one. Polycrystalline silicon material is the main raw material for the production of semiconductors and solar cells. Commercial solar cells are basically made of silicon materials. Due to the mature technology, good quality, abundant raw materials and relatively low price of silicon materials, in the next 50 years , it is impossible to have other materials that can replace silicon materials as the main raw materials for the semiconductor and photovoltaic industries. In the production of sol...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B33/037
Inventor 罗学涛吴浩李锦堂黄平平傅翠梨张蓉
Owner XIAMEN UNIV
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