Grades dichlorosilane

The thermal decomposition of silanes in the presence of hydrogen into siUcon for production of ultrapure, semiconductor-grade siUcon has become an important art, known as the Siemens process (13). A variety of process parameters, which usually include the introduction of hydrogen, have been studied. Silane can be used to deposit siUcon at temperatures below 1000°C (14). Dichlorosilane deposits siUcon at 1000—1150°C (15,16). Ttichlorosilane has been reported as a source for siUcon deposition at >1150° C (17). Tribromosilane is ordinarily a source for siUcon deposition at 600—800°C (18). Thin-film deposition of siUcon metal from silane and disilane takes place at temperatures as low as 640°C, but results in amorphous hydrogenated siUcon (19). 

Trichlorosilane (TCS) is the basic material for the production of hyperpure silicon for the semiconductor industry according to the Siemens process. It is produced by hydrochlorination of technical-grade silicon Si + 3HC1 SiHCls + H2 [1 - 5]. The process aims at maximizing the selectivity toward the main product TCS and at minimizing the by-products like silicon tetrachloride (STC), dichlorosilane (DCS) and the so-called high boilers. Despite decades of industrial practice, the hydrochlorination of silicon is poorly understood. 

Dichlorosilane is primarily sold in ultra-high-purity grades for use in the electronics industry. A typical specification usually quantifies the acceptable levels of hydrocarbons and metals. 

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