NIR laser diode and FTIR based process control for industrial CVD reactors

Aiming toward process control of industrial high yield/high volume CVD reac tors, the potential of optical sensors as a monitoring tool has been explor ed. The sensors selected are based on both Fourier transform infrared spect roscopy (FTIR) and tuneable diode laser spectroscopy (NIR-DLS). The former has the advantage of wide spectral capability and well-established database s. NIRLD spectroscopy has potentially high sensitivity, laser spatial resol ution and the benefits of comparatively easier integration capabilities - i ncluding optical fibre compatibility. The proposed technical approach for p rocess control is characterised by a 'chemistry based' feedback system with in-situ optical data as input information. The selected optical sensors co ntinuously analyse the gas phase near the surface of the growing layer. The spectroscopic data has been correlated with process performance and layer properties, which, in turn establish data basis for process control. The ne w process control approach is currently being verified on different industr ialised CVD coaters. One of the selected applications deals with the deposi tion of SnO2 layers on glass based on the oxidation of (CH3)(2)SnCl2, which is used in high volume production for low-E glazings. (C) 2001 Elsevier Sc ience B.V. All rights reserved.