文摘
Pyrolysis of tetrabromosilane (SiBr4) was carried out by passing vaporized SiBr4 with hydrogen over a substrate heated to less than 1000 掳C. The substrate was then placed in a reaction furnace equipped with a flow system and the exhaust gas containing the reactants and products was analyzed versus temperature. SiBr4 began to decompose at 800 掳C simultaneously with the evolution of tribromosilane (SiHBr3), which was followed by the deposition of silicon in a crystalline form. The conversion of SiBr4 increased with increasing reaction temperature. No reaction occurred in the absence of H2. An experiment with tetrachlorosilane (SiCl4) under the similar conditions led to a decrease in SiCl4 concentration at temperatures greater than 900 掳C. This demonstrates that decomposition of SiBr4 is energetically favorable compared to that of SiCl4, as predicted from the Ellingham diagrams for the reactions of Br- and Cl-containing species. Thus, Si production from bromosilanes is an alternative to the process using SiHCl3, the so-called Siemens method, which is the main technology for Si production currently.