Stress relaxation in sputtered and annealed thin films was studied at various temperatures. The microstructure of films which were stabilized by a thermal cycle to 550C exhibited twinned grains having similar sizes to that of the film thickness. At temperatures below 200C, a small to high stress plasticity was observed, and was attributed to obstacle-controlled dislocation glide. Distinct plasticity was detected between 300 and 550C. This could be described by 2 relaxation processes, with exponentially decreasing stress towards a final value. The activation energies for the 2 processes (0.4eV/atom) agreed. The deformation rates differed by a factor of 10. It was supposed that the slower process was flow via grain-boundary diffusion, which was limited as a result of attachment of the film to the substrate. The faster process was suggested to be mechanical twinning, with diffusional accommodation at the grain boundaries.

Stress-Relaxation in CuNi Thin Films. W.Brückner, V.Weihnacht: Journal of Applied Physics, 1999, 85[7], 3602-8