Mechanical Properties of Alumina Films Sputtered Over Steps

Abstract

AbstractThe properties of sputtered films are strongly affected by the topography of the underlying substrate, due to the dependence of film growth and resputtering yield on the angle of incidence of the sputtered material and other species from the plasma. Thick r.f.-sputtered alumina films were deposited with different levels of substrate bias onto substrates into which parallel grooves had been cut. The alumina sputtered in the vicinity of the grooves forms well-defined regions with a lower incorporated argon content than the alumina sputtered onto the planar parts of the substrate. The ratio of compressive stress perpendicular to the grooves compared to the stress parallel to the grooves varies from 0.85 at zero substrate bias and 0.5 at biases of -50V and -100V. Comparing with finite element simulations, these ratios suggest that in the biased samples, the material near the steps has a lower level of compressive intrinsic stress than exists in the planar material. Nanoindentation was used to measure the modulus and hardness of the material near the steps and on the planar areas of the substrate. The alumina has an indentation modulus of 150 – 200 GPa and a hardness of 8 – 10 GPa, depending on its proximity to the grooves and on the substrate bias.