Recovery of lower-boiling silanes in a cvd process

Abstract From the Canadian patent

A process for the deposition of pure semiconductor silicon by reductive chemical vapor decomposition of a precursor silane, the process comprising: (1) forming and depositing semiconductor silicon on a heated substrate;, (2) separating a mixture enriched in lower-boiling silanes from the effluent gases from the decomposition/ deposition reactor;, (3) combining the mixture enriched in lower-boiling silanes with additional tetrachlorosilane so that there is, present in the combination less than about 1.0 mole hydrogen bonded to silicon per mole of total silicon; (4) passing the combination through a bed of a solid disproportionation catalyst to facilitate disproportionation of …