Dependence on the C2H4 and SiH4 gas mixture of the Si-C film properties obtained by excimer lamp chemical vapour deposition

Abstract Amorphous silicon-carbon alloy films were obtained by photo-chemical vapour deposition irradiating a gas mixture of ethylene and silane diluted in argon with a xenon excimer lamp ( λ = 172 nm). Films were deposited at low temperatures ( T = 200 °C) on to silicon, Corning glass and aluminium substrates. The role of the gas-phase parameters on the composition, structure and optical properties of the films is reported. Characterization by energy dispersive X-ray spectroscopy and Rutherford backscattering spectroscopy revealed that an increase in the ethylene/silane concentration ratio led to important changes in film composition. The ellipsometric measurements indicated a logarithmic decrease in the refractive index from 1.9 to 1.3. Infrared spectroscopy showed the presence of Si-C bonds as well as hydrogen bonded in different configurations to silicon and carbon atoms, with the density of C-H bonds being considerably larger than that of Si-H. Ethylene-rich gas mixtures produced a decrease in the number of Si-H bonds and a shift in their stretching frequencies towards higher wave numbers, due to compositional variations. Postdeposition oxidation of the films was also observed, as a consequence of their porous character.