REACTIVE UNBALANCED MAGNETRON SPUTTERING OF HYDROGENATED AMORPHOUS-SILICON AND SILICON-OXIDE

Hydrogenated amorphous silicon (a-Si:H) films have been deposited using an unbalanced magnetron, giving film deposition rates of around 3 nm s-1, a substrate bias of 30 V and an ion current of 2.50 mA cm-2. A polycrystalline silicon target was reactively sputtered in argon at 3 mtorr and hydrogen partial pressures ranging between 0 and 1 mtorr. Dopants of antimony and indium were also sputtered at the same time as the silicon In order to tailor the absorption coefficient and band gap of the resulting films. The analysis of dopant concentrations was undertaken using SIMS. A novel technique for calculating the absorption coefficients of the a-Si:H films by eliminating interference effects, using three measured optical parameters, is reported here. By replacing hydrogen with oxygen as the reactive gas, it was found to be possible to produce silicon oxides as films with a range of compositions, having optical properties ascribed to the monoxide through to the dioxide, refractive indices from 2 down to 1.45, with optical absorption occurring in the blue region of the spectrum for those with the highest indices.