Feed system and method for polysilicon production

Abstract

The invention relates to a feeding system for a polycrystalline silicon production reduction furnace, and a method thereof. The system comprises: a hydrogen heater for heating hydrogen; a trichlorosilane vaporizer used for vaporizing a trichlorosilane liquid into a trichlorosilane gas; at least first second mixers, wherein each of the mixers is connected with the hydrogen heater and the trichlorosilane vaporizer and respectively receive heated hydrogen and the trichlorosilane gas, the first mixer mixes the received hydrogen and the trichlorosilane gas according to a first preset ratio to form a first feeding gas mixture, and the second mixer mixes the received hydrogen and the trichlorosilane gas according to a second preset ratio to form a second feeding gas mixture; and at least first and second reduction furnaces, wherein the at least first and second reduction furnaces are in fluid communication with the at least first and second mixers respectively to make the first mixer supply the first feeding gas mixture to the first reduction and the second mixer supply the second feeding gas mixture to the second reduction furnace.

Description

technical field [0001] The invention relates to a feeding system (device) and method for polysilicon production. Background technique [0002] The production of polysilicon rods is the most important stage in the process of preparing high-purity silicon, which plays an inestimable role in the output, quality, cost of polysilicon and the coordination, stability and safety of the entire production system. [0003] At present, domestic polysilicon production usually adopts hydrogen reduction method of trichlorosilane. Purified and purified hydrogen and trichlorosilane are supplied to the reduction furnace in a certain proportion, and the following chemical reactions are carried out at a certain high temperature. The produced silicon is deposited on the silicon core in the reduction furnace. The main chemical reaction equation is: [0004] SiHCl 3 +H 2 →Si+3HCl; [0005] Simultaneously, SiHCl 3 Thermal decomposition and SiCl 4 The reduction reaction: [0006] 4SiHCl 3 →S...

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Problems solved by technology

[0010] If the ratio of the selected reaction mixture is too large, the excess of hydrogen gas is more than the stoichiometric value, and the growth rate is low, which is conducive to improving the yield of silicon, but the "corn cob" phenomenon is prone to appear in the later stage of silicon rod growth.

The corn cob phenomenon is: the silicon cob grows into a corn cob shape, and the polycrystalline silicon cob in this state will have the following disadvantages: the quality of the silicon cob is poor, and there is a large amount of boron (B) and phosphorus (P) between the "corn kernels" due to high temperature. The accumulation of impurities and metal impurities leads to a decline in product quality; the silicon rod is loose and easy to fall, causing more serious losses

Because the mixed gas flowing out of one vaporizer will enter several reduction furnaces respectively, changing the ratio of mixed gas in one vaporizer will affect the feed ratio of all reduction furnaces

When the reduction furnaces are in different periods of the polysilicon growth process, this may have a rather adverse impact on the system: if the ratio is increased, one of the reduction furnaces is in the late stage of polysilicon growth, and corn cobs will appear; If the ratio is lowered, the yield of silicon in the reduction furnace in the early stage of growth will decrease

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