A polysilicon production process and a production system for the process

Abstract

The invention relates to a polysilicon production process and a production system used in the process. It includes mixing refined trichlorosilane with a concentration of more than 99.99% and hydrogen at a hydrogen:refined trichlorosilane molar ratio of 4 to 3:1 as a mixed gas feed into the CVD reduction furnace, and the mixed gas feed passes through the Bubble carburetor, heat exchanger for inlet and outlet, CVD reduction furnace main furnace and CVD reduction furnace auxiliary furnace connected in series; the final tail gas discharged from the CVD reduction furnace auxiliary furnace enters the CVD reduction furnace main furnace after heat exchange, and then enters the CVD reduction furnace main furnace. The surface of the silicon core in the furnace reacts to form polysilicon, and its by-product is intermediate tail gas; the intermediate tail gas is mixed with supplementary refined trichlorosilane gas and then enters the auxiliary furnace of the CVD reduction furnace, where the silicon core surface in the auxiliary furnace of the CVD reduction furnace generates The reaction produces polysilicon, and its by-product is the final tail gas; after the final tail gas comes out of the furnace, it exchanges heat with the mixed gas feed and then enters the reduction tail gas recovery system. The process and production system can produce high-quality electronic-grade polysilicon with high efficiency and low cost.

Description

technical field [0001] The invention relates to a polysilicon production process and a production system used in the process. Background technique [0002] Most factories use the trichlorosilane method to produce polysilicon, that is, trichlorosilane and hydrogen are mixed in a certain ratio, and after heat exchange with the reduction tail gas, they enter the reduction furnace and react on the surface of the silicon core at 1150 ° C in the furnace to form polysilicon. , the by-product reduction tail gas exits the reduction furnace, heats the feed mixture gas, and then enters the subsequent tail gas recovery system (see attached figure 2 ). Although the yield of this method is not low, and the trichlorosilane, hydrogen, and silicon tetrachloride in the reduction tail gas can be recycled, the primary use efficiency of the trichlorosilane is very low, and the unreacted trichlorohydrogen in the reduction tail gas Silicon accounts for about 52-60% of the total trichlorosilane f...

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Problems solved by technology

Which attached image 3 The disadvantage of the a process flow in the process is that the main furnace is charged. In the later stage of production, the ratio of other gases except trichlorosilane to trichlorosilane in the reduction tail gas is 9~6:1, and the ratio of trichlorosilane If the supersaturation is too low to meet the growth needs of the auxiliary furnace, cauliflower material will appear on the surface of the polysilicon rod of the auxiliary furnace, and the gap between the cauliflower material will greatly increase the precipitation of B, P and metal impurities due to the high temperature. Ultimately, the quality of polysilicon in the auxiliary furnace is seriously unqualified

attached Figure 4 The disadvantage of the b process in the process is that the feed to the auxiliary furnace is twice that of the main furnace. Too much feed will reduce the surface temperature of the auxiliary furnace, and the reaction temperature on the polysilicon surface must be maintained during operation. Therefore, in In the middle stage of the growth of the auxiliary furnace, there will be a large increase in current in order for the surface temperature of the silicon rod to reach the normal reaction temperature, which will cause the center temperature of the silicon rod to be too high, and eventually the melting core of the silicon rod will cause the rod to fall. If it is not handled properly, the reduction furnace will be damaged. A series of vicious accidents, so this method lacks operability

[0004] The invention patent application with the patent publication number CN101541678A discloses a process for producing polysilicon using a fluidized bed reactor and a Siemens reactor, and the exhaust gas from the Siemens reactor is fed to the fluidized bed reaction as a feed gas In the device, this process relatively improves the primary utilization rate of trichlorosilane, reduces the heat required to be supplied by the fluidized bed, and the feed gas flow supplemented to the fluidized bed can also meet the needs of the continuous operation of the fluidized bed, but due to The surface area of ​​granular silicon is large, and it is easy to cause pollution of polysilicon particles during the production process, such as the pollution of heavy metal elements on the furnace wall. Therefore, the polysilicon produced in the fluidized bed cannot meet the standard of electronic grade polysilicon; the abrasion of solid particles and the entrainment of dust in the airflow Emission in the exhaust gas will not only affect the exhaust gas recovery system, but also increase the exhaust gas filtration and recovery equipment, and cause the loss of raw materials

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