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01 Enaohwo Eu
- 1. Overview of the Production of Silicon Enaohwo Enakeme Cmen 413-001
- 3. FIGURE 1: BFD FOR THE PRODUCTION OF SEMICONDUCTOR GRADE SILICON [1]
- 4. Key to the BFD [1] a TCS synthesis by hydrogenation of TET in the fluidised bed reactor b Separation of TCS/TET by distillation c Redistribution 1 in catalytic column d Separation of DCS/TET/TCS by distillation e Redistribution 2 in catalytic column f Separation of DCS/TET/SiH 4
Hinweis der Redaktion
- Silicon which is the fourteenth element in the periodic table and it never occurs free in nature, but in a combination with oxygen forming oxides and silicates [1]. In regards to this occurrence, several steps have been taken to produce different grades (metallurgical and semiconductor (polysilicon) etc) in a number of ways that depend on the purity that is desired. A brief summary on the production of Metallurgical grade silicon is given above but the process of interest is Semiconductor grade silicon which is discussed in further detail in the Union carbide process.
- The feed to the system is metallurgical grade silicon (MG-Si), hydrogen and tetrachlorosilane (TET). TET is hydrogenated/reduced in (a) in the presence of MG-Si to trichlorosilane (TCS), it is shown by equation 1. TET and TCS are then separated by distillation (b): TET is recycled back to the feed stream, also low boiling impurities are removed and the purified TCS goes on. The TCS is redistributed in catalytic columns (c and e) with quaternary ammonium ion exchange resins as catalysts [1]. The redistribution process is shown by equations 2 and 3 and their products undergo distillation to produce Dichlorosilane (DCS) and silane (d and f). TET and TCS are recycled from (d) to (c) and some of the TET is also sent back to the feed stream where they undergo equations 1 and 2, respectively. DCS that is not converted to silane in equation 3 in (f) is recycled back to the DCS stream that is entering (e) where it goes through the redistribution process again. Silane goes through further purification by distillation and is then pyrolysed to polysilicon on heated silicon seed rod that are mounted in a metal bell jar reactor [1] , the hydrogen from the pyrolysis chamber is recycled back to the Hydrogen that enters the hydrogenation chamber, this process is shown by equation 4. The general separation technique that is utilized in this production of silicon is separation by phase addition or creation,[3] specifically distillation.
- The table above shows a key to the block flow diagram in the previous page; it shows the labels (the space was too small for text) and what they represent and the various separation process.