DEPOSITION OF TIO2 THIN-FILMS BY PLASMA-ENHANCED DECOMPOSITION OF TETRAISOPROPYLTITANATE

We investigated the suitability of tetraisopropyltitanate as a source gas for plasma-enhanced deposition of titanium dioxide thin films. Whereas TiO2 deposition using a standard planar reactor as well as a remote plasma process with O2 as reactant were found difficult to control, stoichiometric, carbon-free TiO2 can be deposited if the remote process with inert reactants such as argon or xenon is used. Deposition rates of 15 nm min-1 can be achieved. The refractive index, being a most important property in view of possible applications of TiO2 films as optical coatings, can be varied from 1.8 to 2.5 by suitable choice of deposition parameters. Film stoichiometry was found to be almost parameter independent whereas film density-rho and, strongly correlated with rho, properties such as the refractive index and the chemical resistance are mainly influenced by processing temperatures, in situ during deposition as well as ex situ by post-deposition annealing.