How is the yield of the reactants TCS and hydrogen increased in the reduction reaction?
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I have been working in the polysilicon reduction workshop for some time now, but I still only have a superficial understanding of the methods and principles involved in increasing the yield of the reduction reaction. I know that during different stages of production the silicon rods keep growing larger, and the amount used increases accordingly based on the ratio of reactants – but I’m not sure how exactly this increase is achieved. I hope all experts will be kind enough to share their insights!
Generally speaking, over time the ratio is continuously reduced while the amount increases, and stable operation is achieved after several dozen hours
I would like to ask those upstairs: what was the initial ratio? Why keep reducing it until it stabilizes? What will it be approximately after stabilization? Is it the common 3:1 ratio?
Why does the ratio on the 2nd floor need to be reduced continuously? What’s the reason? Regarding the original poster’s question, the feed rate is determined based on the surface area of the silicon rods and the deposition rate, in order to determine the amount of gas mixture needed
Reply to 4# maxwell_112: As time goes by, the surface area of the silicon rod increases, which means more material is required. It is currently in a growth phase; if you reduce the ratio, more TCS will be produced. It’s important to adjust the current accordingly now, as the rod grows rapidly. Once it reaches a larger size, you can simply increase the ratio
Reply to 5# lisame10: So does each of your reduction furnaces come equipped with a vaporizer? In our case, several furnaces share one vaporizer, and the heating time for each furnace is different; therefore, it’s not possible to adjust the ratio.
Depending on the growth stage of the silicon rods, most processes now involve a different feeding rate at each stage, and this rate varies from one manufacturer to another. The feeding rate increases as the growth progresses, but care must be taken to monitor the temperature of the silicon rods during feeding