A. Shelemin, O. Zabeida, J. E. Klemberg-Sapieha, L. Martinu

Department of Engineering Physics, Polytechnique Montreal, Montreal, Quebec H3T 1J4, Canada

The ion beam-assisted chemical vapor deposition (IBA-CVD) has been demonstrated as a promising method for the fabrication of the hybrid (organic-inorganic) optical coatings. Despite a large number of data on the film properties, there is an evident lack of information about the processes in the gas phase and at the surface during the growth. Hence, better understanding of the underlying mechanisms is crucial for the transfer of this technology to industry. In this work, gas phase composition and plasma characteristics of the IBA-CVD processes were monitored by three independent diagnostic techniques - optical emission spectroscopy, residual gas analysis, and Langmuir probe. Using HMDSO as a model precursor, we investigated the effect of discharge power (W) and monomer (F) flow on the deposition process. We found that the W/F ratio is a crucial parameter that regulates monomer molecules dissociation and oxidation reactions, which, in turn, predetermine the films’ characteristics.

It was revealed that the IBA-CVD operated under near-optimum conditions yielding good-quality optical films develops W/F values varying from 12 to 270 W/sccm. Such energies per molecule induce an extensive depletion of the HMDSO units in the gas phase from 70% up to 96%. An intense dissociation of the organic molecules is accompanied by their reaction with oxygen, as was evidenced by similar depletion levels of O2 molecules. In addition, we show that the W/F ratio enables one to control the deposition rate and density of the resulting films.