Mechanical properties of amorphous and microcrystalline silicon films

Abstract Hydrogen-free amorphous silicon (a-Si) films with thickness of 4.5–6.5 μm were prepared by magnetron sputtering of pure silicon. Mechanical properties (hardness, intrinsic stress, elastic modulus), and film structure (Raman spectra, electron diffraction) were investigated in dependence on the substrate bias and temperature. The increasing negative substrate bias or Ar pressure results in simultaneous reducing compressive stress, the film hardness and elastic modulus. Vacuum annealing or deposition of a-Si films at temperatures up to 600 °C saving amorphous character of the films, results in reducing compressive stress and increasing the hardness and elastic modulus. The latter value was always lower than that for monocrystalline Si(111). The crystalline structure (c-Si) starts to be formed at deposition temperature of ∼ 700 °C. The hardness and elastic modulus of c-Si films were very close to monocrystalline Si(111). Phase transformations observed in the samples at indentation depend not only on the load and loading rate but also on the initial phase of silicon. However, the film hardness is not too sensitive to the presence of phase transformations.