Influence of Sputter Gas Pressure and Substrate Bias on Intrinsic Stress and Crystallinity of Coatings Produced by Magnetron Sputtering

Abstract

DC magnetron sputtered Molybdenum thin coatings were produced at different sputter gas pressure with negative substrate potential in order to investigate the influence of this deposition parameters on intrinsic stress and crystallinity of thin films. Crystallinity and intrinsic stress of Mo-coatings were analyzed by scanning electron microscopy (SEM), interferometry and X-ray diffraction (XRD). The sputtered Molybdenum thin coatings produced at different sputter gas pressure with negative substrate bias show columnar structure. Mo-coatings produced at high pressures are strongly textured with a preferred orientation of the (110) crystallographic plane parallel to the substrate surface. Coatings produced at low sputter gas pressures were almost amorphous. The coating intrinsic stress is strongly dependent on sputter gas pressure and applied bias. The characteristic compressiveto-tensile stress transition curve was observed. The intrinsic stress varies rapidly with increasing sputter gas pressure from −2 × 109 N/m2 (compressive) to a maximum tensile stress of 1 × 109 N/m2. After reaching the maximum tensile stress, the stress decreases monotonically with increasing sputter gas pressure. In parallel with stress changes the coating microstucture (the coating density varies from 8.47 g/cm3 to 9.95 g/cm3), optical reflectance (from 38 % to 55%) and electrical conductivity (0.9 × 106 Ω−1m−1 to 4.0 × 106 Ω−1m−1).