Stoichiometric Control of SiOx Thin Films Grown by Reactive Magnetron Sputtering at Oblique Angles

The deposition of SiOx (x≤2) compound thin films by the reactive magnetron sputtering technique at oblique angles is studied from both theoretical and experimental points of view. A simple mathematical formula that links the film stoichiometry and the deposition conditions is deduced. Numerous experiments have been carried out to test this formula at different deposition pressures and oblique angle geometries obtaining a fairly good agreement in all studied conditions. It is found that, at low deposition pressures, the proportion of oxygen with respect to silicon in the film increases a factor of ∼5 when solely tilting the film substrate with respect to the target, whereas at high pressures the film stoichiometry depends very weakly on the tilt angle. This behavior is explained by considering the fundamental processes mediating the growth of the film by this technique. We analyze how the oblique angle geometry influences the film stoichiometry in reactive magnetron sputtering depositions. A simple mathematical formula that links the film stoichiometry and the deposition conditions is deduced. This equation reproduces all experimental data at low and at high deposition pressures for different values of the deposition angle.