Influence of sputtering gases on the properties of magnetron sputtered tungsten films

Tungsten films nearly 15 mu m thick were produced on Ti6A14V substrates by d.c. magnetron sputtering in pure argon pure krypton and argon-krypton mixtures, applying a substrate bias voltage of -25 V. The residual stresses in the films were determined by a beam curvature technique and the hardness was measured by Vickers microindentation. Gas contents in the films were analysed by electron probe microanalysis or particle induced X-ray emission. Compressive intrinsic stress was minimal with pure krypton (-1.2 GPa) and increased with the argon gas mixture content up to -3.2 GPa with purr argon. The film Vickers microhardness was also minimal with pure krypton (8.2 GPa) and increased with the argon mixture content up to 17 GPa in pure argon. These changes in film mechanical properties were perfectly correlated with the embedded argon concentration and related to the amount of energy arriving on the growing film. The effect of the energetic particles bombarding the growing film was also studied by biasing the substrate up to -1000 V.