An X-ray study of the behavior of titanium films on silicon substrates

The thin film reaction between silicon and titanium did differ from the ordinary diffusion process in bulk samples at elevated temperatures. The lower free energy monosilicide formed prior to the disilicide in bulk standards and was also the dominant reaction product at lower temperatures in films. Titanium thin films, 2.3 microns thick, sustained considerable mechanical deformation during cooling from elevated temperatures. Line broadening, greater than that obtained from cold worked filings of titanium at room temperature, necessitated the use of computer simulation techniques to analyze the diffracted intensity from the reacted structure.

The structure and space group of titanium disilicide was confirmed along with a determination of both structure factor forms and accurate lattice parameters. A range of compositions for the monosilicide of titanium was observed along with the identification of Ti₅Si₄₍₃₇₎ as a high temperature compound. The identification of the inaccuracies and omissions present in the ASTM powder diffraction card files should resolve the confusion in the literature on the reaction between titanium films and silicon.

The temperatures for formation of silicides in thin films was found to be substantially lower than previously reported₍₂₎, indicative of the oxide free interface of the silicon substrates. The identification of the reactant silicides, deposited at the grain boundaries and as planar film at interfaces, establishes this study as the first attempt to develop a quantitative model for silicide formation in this transition metal system.