Design of a fast in situ infrared diagnostic tool

Conventional Fourier transform IR (FTIR) spectroscopes cannot be used to perform real time in situ IR reflection absorption spectroscopy at monolayer sensitivity for high deposition rates (a couple of tens to hundreds of nm/s) which can be obtained when using an expanding thermal deposition plasma. Therefore a new anal. tool has been developed. The tool is based on a fast optical scanner in combination with conventional grating technol. This results in a loss of spectral range with respect to FTIR spectroscopes, but a significant gain is obtained in time resoln. For the combination used this makes it possible to measure at time resoln. as low as 1.3 ms and resoln. of 24 cm-1 at 1000 cm-1. The absorption sensitivity for single reflection at the best time resoln. is approx. 10-2, but can be improved by using signal enhancement techniques. Here attenuated total reflection is used and the best sensitivity obtained is approx. 10-3, which is close to monolayer sensitivity for various absorption bands in the IR spectrum of silicon oxide films. Monolayer sensitivity can be obtained by averaging multiple spectra, however this will cause the time resoln. to decrease