Study of silicon oxynitride thin films deposited by RF sputtering for optical applications

This work is based on the study of silicon oxynitride thin films, deposited by RF magnetron sputtering, to realize low losses optical multilayers (absorption, sputtering). At first, we have analysed the variations of the optical and physicochemical properties of the oxynitrides monolayers due to the deposition parameters: the gas partial pressures, the RF power, the target composition, the gas mixture. So, by describing the whole oxynitrides domain from the oxide to the nitride, we have shown the linear variation of the refractive index as well as the strict substitution of oxygen atoms by nitrogen atoms: this is the proof of a simple mechanism of formation. Moreover, thanks to IR spectrophotometric analyses, a model of the oxynitrides amorphous structure has been proposed and confirmed by two approximation methods. At last, we have studied more precisely the absorption (photothermal deflection) and the scattering (scatterrometer CASI) levels of the monolayers and the multilayers synthesized from silicon oxynitrides (antireflective stacks, mirrors). A comparison with the optical performances of classical stacks made of oxide, deposited by ion beam sputtering, have been made and we have proposed some solutions to decrease the two sources of losses. (author)