Siemens process
The Siemens process enables the production of polycrystalline silicon of high purity. It is used to produce raw material for solar cells and microelectronics . The name is derived from the Siemens company that developed the process.
Procedure
The starting material is 98–99% pure silicon, which is ground and converted into trichlorosilane with gaseous hydrogen chloride at 300–350 ° C in a reactor .
In a further process, silicon is obtained from trichlorosilane and hydrogen.
This elementary silicon is caught on rods at 1100 ° C. The hydrogen chloride can be fed back into the cycle. The resulting silicon tetrachloride by-product can either be added to the cycle via trichlorosilane or burned.
A disadvantage of the process is the very high energy consumption. Therefore, other manufacturing methods such as the UMG process (Upgraded Metallurgical Grade) and the FBR process ( Fluidized Bed Reactor ) are now being researched, but must be further developed for production. It was also originally developed for microelectronics . There, different requirements are placed on the quality of silicon than in photovoltaics. For solar cells, for example, the purity of the wafer in its entire thickness is important in order to ensure the longest possible charge carrier life. In microelectronics, on the other hand, only the upper 20 to 30 µm should in principle be highly pure.
literature
- Erhard Sirtl, Konrad Reuschel: About the reduction of chlorosilanes with hydrogen . In: Journal of Inorganic and General Chemistry . tape 332 , no. 3-4 , October 1964, pp. 113-123 , doi : 10.1002 / zaac.19643320302 ( PDF ).
Web links
- MAXUM II Online monitoring of the production of polysilicon in the photovoltaic industry. (PDF) Siemens , 2009, accessed on November 3, 2015 .
Individual evidence
- ↑ William intent: Big win , magazine photovoltaik, issue: 07-2009