Technologies for polysilicon purification
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What is the process involved in polysilicon purification?
Hello: I was hoping you could recommend a forum for exchanges in the silicon industry – http://www.sizxbbs.com/index.php. It’s the China Silicon Industry Online Forum, covering the upstream and downstream sectors of metallic silicon and silicone, as well as those related to polysilicon; it encompasses the entire silicon materials industry, and it also serves as a platform for collaboration among silicon materials laboratories!
This is a major issue; in fact, purification starting from the raw materials is the key
The main production process of polysilicon is as follows: 1. Silicon powder is reacted with hydrogen chloride to produce trichlorosilane; of course, this reaction has side reactions that result in the formation of silicon tetrachloride； 2. The mixture of trichlorosilane and silicon tetrachloride is purified using a distillation tower to obtain high-purity trichlorosilane, with the purity required to be at least 6 nines. For example, a distillation tower at a company in Leshan is 70 meters tall. 3. By reducing trichlorosilane with high-purity hydrogen, elemental silicon is produced. After that, there’s fragmentation and such; I won’t go into details here.
It is essentially a chemical purification process. Silicon is mixed with impurities in solid metallic silicon powder, making it difficult to separate them. By using chlorine and hydrogen to convert these elements into liquid/gaseous compounds, separation becomes easier. After separation, the gas containing silicon is then converted back into solid silicon. As for physical/metallurgical methods, they involve directly turning silicon into a liquid state for separation, without any chemical reactions taking place with the silicon itself
This is based on principles of chemical engineering: distillation for purification is a physical process that utilizes the relative volatility of various components within a mixture to separate them, resulting in pure light components at the top of the tower and pure heavy components at the bottom!
What the original poster is asking about is probably not just distillation...
There must be chemical processes involved; in physical methods, silicon is chlorinated or hydrogenated, and the resulting products are then decomposed. Of course, this includes the purification of the reaction products as well
I’m very interested in learning about this area; I’ve just started working in this field and want to study hard*~~
The question is too broad; if you just want to learn about it, you’d better read more on the principles of chemical engineering.