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

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. (C) 2001 Elsevier Science Ltd. All rights reserved.