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A method for purifying polysilicon by using a liquid filter

A technology of polysilicon and filter screens, which is applied in the growth of polycrystalline materials, chemical instruments and methods, and single crystal growth. It can solve the problems of not being able to meet solar energy, achieve stable grain size, and improve the effect of uniform distribution.

Inactive Publication Date: 2011-11-30
NAN AN SANJING SOLAR POWER
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the polysilicon purity after general directional solidification is 4-5N (99.99%-99.999%wt), which cannot meet the needs of the solar energy industry. The present invention is an improvement aimed at this technical problem

Method used

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  • A method for purifying polysilicon by using a liquid filter
  • A method for purifying polysilicon by using a liquid filter
  • A method for purifying polysilicon by using a liquid filter

Examples

Experimental program
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Effect test

Embodiment 1

[0030] Put 140kg of 4-5N polycrystalline silicon into a quartz crucible, and put 60kg of Sn and Ga as the filter material at the same time, of which Sn is 55kg, Ga is 5kg, and vacuum pumped to 10 -3 After Pa, fill with argon, stop the diffusion pump to maintain a slight positive pressure in the furnace, turn on the control power supply, and the heater starts to heat until the mixture of silicon and filter material is completely melted at 1380 ° C, and the temperature is kept for 2 hours. Then turn on the temperature control to gradually cool the material in the crucible at a cooling rate of 0.2°C / h. During this process, silicon begins to crystallize, and the filter material slowly moves up. This process needs to maintain the temperature balance in the crucible. The temperature difference between the same horizontal plane in the crucible is kept at 0.2°C-0.5°C. The stability of the thermal field is the balance of the liquid filter. Guaranteed to move up slowly. After the tempe...

Embodiment 2

[0032] Put 160kg of 4-5N polysilicon into a quartz crucible, and put in a total of 40kg of Sn and Ga as the filter material at the same time, of which Sn is 39kg, Ga is 1kg, and vacuum pumped to 10 -3After Pa, fill with argon, stop the diffusion pump to maintain a slight positive pressure in the furnace, turn on the control power supply, and the heater starts to heat until the mixture of silicon and filter material is completely melted at 1400 ° C, and the temperature is kept for 3 hours. Then turn on the temperature control to gradually cool the material in the crucible at a cooling rate of 1°C / h. During this process, silicon begins to crystallize at this time, and the filter material slowly moves up. This process needs to maintain the temperature balance in the crucible. Guarantee that the net balance moves up slowly. After the temperature is cooled to 900°C, the temperature can be rapidly lowered, and the cooling rate is 15°C / h. After the crystallization process is over, ...

Embodiment 3

[0034] Put 170kg of 4-5N polysilicon into a quartz crucible, and put 30kg of filter material at the same time, including 28kg of Sn, 2kg of In, and vacuum to 10 -3 After Pa, fill it with helium, stop the diffusion pump to maintain a slight positive pressure in the furnace, turn on the control power supply, and the heater starts to heat until the mixture of silicon and filter material is completely melted at 1400 ° C, and the temperature is kept for 2.5 hours. Then turn on the temperature control to gradually cool the material in the crucible at a cooling rate of 5 °C / h. During this process, silicon begins to crystallize at this time, and the filter material slowly moves up. This process needs to maintain the temperature balance in the crucible. Guarantee that the net balance moves up slowly. After the temperature is cooled to 900°C, the temperature can be rapidly lowered, and the cooling rate is 20°C / h. After the crystallization process is over, cool down, take out the ingot...

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Abstract

The invention discloses a method for purifying polysilicon by using a liquid filter screen, which belongs to the field of metallurgical purification. The method of the present invention is to add a certain amount of metal elements or alloys or metal mixtures whose melting point is lower than the melting point of silicon and whose density is greater than that of silicon during the directional solidification and purification process of silicon. Various impurities are filtered from bottom to top with the filter screen to the surface of the ingot. The method of the invention can effectively reduce the impurity content in silicon, especially the B impurity content, and can reduce the B content from the original 2-4ppmwt to 0.5-1ppmwt. By adopting the method of the invention, the 4-5N polysilicon can be effectively purified to more than 6N.

Description

technical field [0001] The invention belongs to the field of semiconductor materials and solar cell materials, and relates to a purification method for preparing silicon materials with high purity above 6N and high resistivity from 4-5N high-purity polysilicon. Background technique [0002] Polysilicon is the basic material of solar cells, and it is a high-tech industry encouraged by the state. The demand for polysilicon at home and abroad is increasing year by year, and the supply is in short supply. [0003] At present, the main process for producing solar cell grade crystalline silicon in the world is the improved Siemens method, which includes trichlorosilane purification technology for boron removal, large-scale reduction furnace technology, reduction furnace tail gas recovery technology for hydrogen and hydrogen chloride gas recovery, silicon tetrachloride Hydrogenation technology, etc., the manufacturing process includes chlorination-reduction-deposition and other pro...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C30B29/06C30B28/08
Inventor 郑智雄张伟娜南毅马殿军程香赵志跃王致绪戴文伟
Owner NAN AN SANJING SOLAR POWER
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