Mechanisms of Stress Relief in Polycrystalline Films

The stress required to operate dislocation sources within a grain, at a grain boundary, and at surfaces is found to be larger than the intrinsic stresses observed in polycrystalline films. It is therefore unlikely that a dislocation flow mechanism can relieve stresses in films. Grain boundary sliding and diffusional creep can, however, relieve stresses in films and equations describing the kinetics of stress relaxation are derived. It is suggested that stress relief occurs primarily by a diffusion-creep mechanism. Growth of hillocks during annealing of a film is briefly discussed in terms of the diffusion-creep mechanism.