FTIR based process control for industrial reactors

Aiming to process control of industrial high yield / high volume CVD reacto rs, the potential of Fourier transform infrared spectroscopy (FTIR) has bee n checked as a monitoring tool. Tin oxide deposition on glass by oxidation of dimethyl tin dichlorid in a cold-wall thermal CVD reactor was selected a s test case. Four different FTIR monitoring modes have been evaluated and f ound feasible: transmission, (gas) emission, reflection and surface emissio n. The most detailed information of the composition of the gas atmosphere i n the deposition zone is derived from the transmission and (gas) emission m easurements. The emission mode is best suited for high temperature CVD reac tors, needs only low effort for optical adaptation of the monitoring system but higher effort in data treatment for process control. Information on bo th gas composition and surface layer are derived from the reflection and th e surface emission modes. Depending on the polarization stale of the surfac e emission, spectra contain information either on the sample surface only o r on the reacting gas phase, too.