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Metallic silicon surface treatment purification method

A surface treatment and purification method technology, applied in the direction of non-metallic elements, chemical instruments and methods, silicon compounds, etc., can solve the problems that metal impurities cannot be removed or are difficult to remove

Inactive Publication Date: 2010-07-07
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It is generally believed that the segregation coefficients of most metal impurities in silicon are very small, and can be removed by directional solidification; however, the segregation coefficients of B and P (0.8 and 0.35, respectively) are relatively large, and it is difficult to remove them by directional solidification.
Moreover, when the concentration of metal impurities is very high (greater than 1ppmw), the metal impurities cannot be removed by directional solidification

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] 1) Degreasing and cleaning metallic silicon with a particle size of 0.05 mm in acetone by ultrasonic waves;

[0019] 2) The product of step 1) is ball-milled to 0.005 mm in ethanol as a medium, and the resulting product is dried under an argon atmosphere;

[0020] 3) Put the product of step 2) into an annealing furnace, heat to 1050°C, keep it warm for 30 minutes, cool down to 700°C at a rate of 1°C per minute, keep it warm for 30 minutes, and then cool with the furnace;

[0021] 4) The product of step 3) is taken out, soaked for 1 hour with 5% hydrochloric acid and 1% hydrofluoric acid at a volume ratio of 1:1, and then cleaned with deionized water. High-grade metal silicon materials with a purity of 4N can be obtained. (The impurity content has been tested by ICPMS, see the table below for details, ppmw refers to one millionth by mass, that is, there is 1 microgram of metal impurities per gram of silicon)

[0022] Impurity atoms

Embodiment 2

[0024] 1) Degreasing and cleaning metal silicon with a particle size of 1mm in acetone by ultrasonic;

[0025] 2) The product of step 1) is ball-milled to 0.01 mm with acetone as the medium, and the resulting product is dried with argon;

[0026] 3) Put the product of step 2) into an annealing furnace, rapidly heat to 1200°C, keep it warm for 60 minutes, cool down to 750°C at a rate of 5°C per minute, keep it warm for 60 minutes, and then cool with the furnace;

[0027] 4) The product of step 3) is taken out, soaked for 3.5 hours with 10% hydrochloric acid and 5% hydrofluoric acid with a mass percentage concentration of 1:1, and then cleaned with deionized water. High-grade metal silicon materials with a purity of 5N can be obtained. (The content of impurities has been tested by ICPMS, see the table below for details)

[0028] Impurity atoms

Embodiment 3

[0030] 1) Degreasing and cleaning metallic silicon with a particle size of 10 mm in acetone by ultrasonic waves;

[0031] 2) The product of step 1) is ball-milled to 0.03 mm in ethanol as a medium, and the resulting product is dried with argon;

[0032] 3) Put the product of step 2) into an annealing furnace, rapidly heat to 1350°C, keep it for 120 minutes, cool down to 900°C at a rate of 10°C per minute, keep it for 150 minutes, and then cool with the furnace;

[0033] 4) The product of step 3) is taken out, soaked with 20% hydrochloric acid and 10% hydrofluoric acid in a volume ratio of 1:1 for 5 hours, and then cleaned with deionized water. High-grade metal silicon materials with a purity of 4.5N can be obtained. (The content of impurities has been tested by ICPMS, see the table below for details)

[0034] Impurity atoms

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PUM

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Abstract

The invention discloses a metallic silicon surface treatment purification method, comprising the following steps: deoiling and cleaning metallic silicon; carrying out ball-milling on the metallic silicon with alcohol or ketone as medium and then drying the metallic silicon with argon; heating the dried metallic silicon quickly and carrying out heat preservation and reduction in succession and then cooling; taking out the cooled metallic silicon and dipping the metallic silicon into a mixed solution of muriatic acid and hydrofluoric acid; and cleaning the dipped metallic silicon with deionized water. In the invention, principles of impurity outdiffusion and surface impurity absorption of metallic silicon are adopted, a large area of defect is created on the surface of the metallic silicon artificially to form an affected layer, impurities in the metallic silicon are absorbed at high temperature, and preliminary purification treatment is carried out on the surface of the metallic silicon to improve the purity of the metallic silicon to 99.99%-99.999% (4-5N), so that the invention can be applied to silicon used for solar cell or further-purified material for subsequent purification technology.

Description

technical field [0001] The invention relates to a method for purifying metallic silicon, in particular to a method for purifying the surface of metallic silicon. Background technique [0002] Solar energy is widely distributed and is an inexhaustible clean energy. Solar cells can convert solar energy into electrical energy, but the current price of solar cells is relatively high, especially the cost of crystalline silicon cells, which is the main body of the photovoltaic market, is still very high, which seriously affects the promotion and use of solar energy. [0003] According to authoritative forecasts, the photovoltaic market in the next 10 years will still be dominated by crystalline silicon solar cells. In the past five years, the price of solar-grade silicon raw materials has risen to $500 / kg. Although it has fallen back to about $100 / kg, the cost of materials still accounts for more than 25% of the total cost, and it has become one of the most difficult links to red...

Claims

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Application Information

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IPC IPC(8): C01B33/037
Inventor 余学功顾鑫杨德仁
Owner ZHEJIANG UNIV
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