Elaboration, characterization and dielectric properties study of amorphous alumina thin films deposited by r.f. magnetron sputtering

Abstract

The r.f. magnetron sputtering of alumina in pure Ar and Ar–O 2 mixtures was investigated to determine the best conditions for the elaboration of Al–O films. These thin films were analyzed for chemical composition, thickness, density, refractive index, O/Al ratio and dielectric properties in order to know the effect of the inclusion of oxygen or argon in the sputter gas on these alumina layers. The O/Al ratios for these films, as determined by Rutherford backscattering spectrometry and X-ray fluorescence, were higher than or equal to the ratio expected from stoichiometric alumina (1.5). In general, higher partial pressures of oxygen in the sputter plasma produced oxygen-rich films. For a given partial pressure, the inclusion of argon in the films increases when the sputtering pressure decreases. The inclusion of oxygen in the sputtered Al–O is found to correlate with the breakdown field measurements, with the oxygen-rich films proving to be better insulators. The experimental results indicate the dependence of dielectric properties on films sputtering conditions.