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 reac tors. Using methyltrichlorosilane (MTS) as SiC precursor, several gase ous species could be detected including MTS, SiCl2, (SiCl3)(n=1,2), Si Cl4, HSiCl3, CH4, CH3Cl and HCl which, consequently, can be monitored simultaneously. First attempts have been established for deriving arbi trary and absolute concentrations of species from emission spectra. Th e determined composition of the reaction mixture supports recent theor etical results of kinetic modelling. Using the established technique, several runs have been monitored within the SiC-CVI/CVD reactor at dif ferent stages of deposition. Unexspectedly strong variations of concen trations of most of the gaseous species have been detected whose reaso n is not fully clear yet. These technique will be a key element in est ablishing a closed loop process control.