ION SPUTTER RATES AND YIELDS FOR IRON-OXIDE, CHROMIUM-OXIDE AND ALUMINUM-OXIDE LAYERS

Layers of the oxides FeO, Fe3O4, Fe2O3, Cr2O3 and Al2O3 were prepared by evaporation of the corresponding metal layers onto a preoxidized Si substrate and oxidation at elevated temperature. The oxidation was co nducted under thermodynamically well-defined conditions so that the pu re oxide phases noted were obtained. The oxide layer thickness was cal culated from the thickness of the initial metal film, which was determ ined by chemical analysis and from the frequency change of a quartz cr ystal upon evaporaton. Auger electron spectroscopy depth profiles of t he oxide layers were measured during Ar+ sputtering, and the sputter t ime necessary to reach the interface oxide/substrate was determined. T he determination of this sputter time was not very exact, because the transition from oxide to substrate in the profile was rather gradual, owing to the roughness and crystalline character of the oxide layers t hat causes inhomogeneous sputtering. However, from the sputter time, o xide thickness and ion beam current, the sputter rates were obtained f or the oxides noted (in nm muA-1 cm-2 min-1) and were compared to the sputter ate of amorphous Ta2O5, which is generally used as the sputter reference standard. Considerable differences were found. The results will lead to more reliable determinations of oxide scale thicknesses b y sputtering.