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Method and device for removing metal impurities in polycrystalline silicon by directional solidification

A technology of directional solidification and metal impurities, applied in the direction of non-metallic elements, chemical instruments and methods, silicon compounds, etc., can solve the problems of high production cost, long reaction time, long production cycle, etc., and achieve low cost, simple equipment, and production short cycle effect

Active Publication Date: 2014-05-28
福建兴朝阳硅材料股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The above patents all use the method of directional solidification to remove metal impurities, but the reaction time is long, the output is low, the production cycle is long, the energy consumption is large, the equipment is complicated, and the production cost is high.

Method used

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  • Method and device for removing metal impurities in polycrystalline silicon by directional solidification

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Experimental program
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Effect test

Embodiment 1

[0031] Put 100kg of raw silicon into the graphite crucible of the intermediate frequency induction furnace and heat it so that all the silicon material is melted into silicon liquid; the silicon liquid is poured into the improved directional solidification device, and the heat preservation cover is covered. The heat preservation crucible of the directional solidification furnace is characterized by a square bottom and a height equal to The bottom side length ratio is 0.8:1, start the silicon carbon rod switching power supply, realize the heating of the upper part of the silicon liquid, the heating temperature is 1450°C; place the graphite plate on the surface of the silicon liquid, the graphite rod and the graphite layer of the directional solidification furnace are respectively Connect to the negative pole and positive pole of the voltage controller, then apply a DC voltage of 10V, keep it for 2 hours, measure the temperature through a thermocouple, control the temperature of t...

Embodiment 2

[0033] Put 100kg of raw silicon into the graphite crucible of the intermediate frequency induction furnace and heat it to melt all the silicon material into silicon liquid; pour the silicon liquid into the improved directional solidification device, cover the heat preservation cover, start the silicon carbon rod switching power supply, and realize the upper part of the silicon liquid heating , the heating temperature is 1475°C; the graphite plate is placed on the surface of the silicon liquid, the graphite rod and the graphite layer of the directional solidification furnace are respectively connected to the negative pole and the positive pole of the voltage controller, and then a DC voltage of 60V is applied and kept for 3h. Even temperature measurement, control the temperature of the silicon liquid to cool down slowly, the cooling rate is 25°C / h, to achieve directional solidification; after the silicon ingot is cooled, remove the enriched impurities on the top, polish the surro...

Embodiment 3

[0035]Put 100kg of raw silicon into the graphite crucible of the intermediate frequency induction furnace and heat it to melt all the silicon material into silicon liquid; pour the silicon liquid into the improved directional solidification device, cover the heat preservation cover, start the silicon carbon rod switching power supply, and realize the upper part of the silicon liquid heating , the heating temperature is 1500°C; the graphite plate is placed on the surface of the silicon liquid, the graphite rod and the graphite layer of the directional solidification furnace are respectively connected to the negative pole and the positive pole of the voltage controller, and then a DC voltage of 100V is applied and kept for 4h. Even temperature measurement, control the temperature of silicon liquid to cool down slowly, the cooling rate is 28°C / h, to achieve directional solidification; after the silicon ingot is cooled, remove the enriched impurities on the top, polish the surroundi...

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Abstract

The invention relates to a method for removing metal impurities in polycrystalline silicon by directional solidification. The method comprises the steps of: (1) melting raw material silicon in a graphite crucible, pouring a silicon liquid into a directional solidification device, covering by an insulating plate, and maintaining upper temperature at 1450-1500 DEG C; (2) placing a graphite plate on the surface of the silicon liquid, wherein the graphite plate is connected with the cathode of an external direct current voltage, a graphite layer at the bottom of the directional solidification device is connected with the anode of the external direct current voltage, and the applied direct current voltage is 10-100V; (3) after electrifying for 2-4h, in an electrified state, cooling at 22-28 DEG C / h for directional solidification, cooling and taking out a silicon ingot, and cutting off upper and tail enriched impurity areas to obtain polycrystalline silicon with total metal impurity content which is smaller than 0.1ppm. With the adoption of the method for removing metal impurities by electrophoretic assistant directional solidification, the content of metal impurities can be effectively reduced, the production cost can be greatly lowered, and the problem of low output, long production period, large energy consumption, complex equipment and high production cost can be solved.

Description

technical field [0001] The invention relates to the field of purification of solar-grade polysilicon, in particular to a method for removing metal impurities by electrophoresis-assisted directional solidification, and also to its equipment. Background technique [0002] Photovoltaic energy is one of the most important new energy sources in the 21st century. In recent years, the global photovoltaic industry has developed rapidly. In order to meet the rapid development of the photovoltaic industry, all countries in the world are committed to developing new preparation technologies and processes for solar polysilicon with low cost and low energy consumption, such as improved Siemens method, new silane method, fluidized bed method, Metallurgy etc. Among them, the process of purifying polysilicon by metallurgy is relatively simple, the cost is low, and the pollution to the environment is relatively small, and it has become the main development direction of solar-grade polysilico...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B33/037
Inventor 李伟生龚炳生杨凤炳
Owner 福建兴朝阳硅材料股份有限公司
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