INSITU REAL-TIME ELLIPSOMETRIC STUDY OF THE GROWTH OF RF PLASMA-DEPOSITED AMORPHOUS HYDROGENATED SILICON OXYNITRIDE THIN-FILMS

Amorphous hydrogenated silicon oxynitride thin films for electronic applications have been obtained from N2O + SiH4 gas mixtures by plasma-enhanced chemical vapour deposition. The films were deposited on crystalline silicon substrates at 300-degrees-C at various relative compositions of gas mixture, and they were optically characterized in situ during the deposition process by real-time phase-modulated ellipsometry at a fixed wavelength of 500 nm. The accurate experimental trajectories of the ellipsometric angles were analysed through theoretical growth models in order to determine the film thickness, the deposition rate, the optical parameters and the film-substrate interface. We have correlated the increase in the refractive index and extinction coefficient with silane concentration. Ellipsometric data indicate an abrupt film-substrate interface for these transparent films. They also suggest a slight inhomogeneity in grown films, interpreted in terms of the r.f. plasma evolution.