Monitoring of SiC Deposition in an Industrial CVI/CVD Reactor by In-Situ FTIR Spectroscopy

A FTIR based method was developed for in-situ monitoring the gas phase chemistry in the reaction chamber of technological scale CVI/CVD reactors. Using methyltrichlorosilane (MTS) as SiC precursor, several gaseous species could be detected including MTS, SiCl2, (SiCl3)n=1,2, SiCl4, HSiCl3, CH4, CH3Cl and HCl which, consequently, can be monitored simultaneously. First attempts have been established for derivinp arbitrary and absolute concentrations of species from emission spectra. The determined composition of the reaction mixture supports recent theoretical results of kinetic rnodelling. Using the established technique, several runs have been monitored within the SiC-CVI/CVD reactor at different stages of deposition. Unexspectedly strong variations of concentrations of most of the gaseous species have been detected whose reason is not fully clear yet. These technique will be a key element in establishing a closed loop process control