NIR diode laser based process control for industrial CVD reactors

The proposed new technical approach for CVD process control is characterise d by a "chemistry based" feedback system with in-situ optical data as input information. The selected optical sensors continuously analyse the gas pha se near the surface of the growing layer. The spectroscopic data has been c orrelated,vith process performance and layer properties, which in turn esta blish a data basis for process control. Diode laser spectroscopy in the nea r infrared (NIR-DLS) has been successfully applied for monitoring industria l CVD reactors. This technology has some notable potential advantages for p roduction process applications. For example, the technology is robust and s imple to operate, interference between species detection can be reduced, an d simultaneous multi-point monitoring is readily achieved. The new process control approach is currently being verified on different industrialised CV D coaters. The paper will present some results of recent process monitoring studies on deposition of SnO2 layers on glass, based on the oxidation of ( CH3)(2)SnCl2, which is used in high volume production for low-E glazings. K inetic investigations support the empirically determined stiff correlation between gas phase composition and deposition rate.