Combined effects of residual stress and microstructure on degradation of Cu thin films on Si

Abstract

In this paper, combined effects of residual stress and microstructure on degradation of Cu thin films on Si have been investigated. Magnetron sputtering with different processing parameters produced cracked and non-cracked Cu films with various grain sizes and residual stresses. Phase transformation and the change in electrical resistance of the Cu thin films have been analyzed for different annealing conditions. It has been revealed that non-cracked and large-grained (25.2±8.9nm) Cu films with high tensile residual stress (186 MPa) result in the most significant degradation (sheet resistance increase of 894%) upon annealing at 300°C. Specimens with smaller grains (17.3±6.4 nm) and low residual stress (41.6 MPa) or cracks showed no increase in sheet resistance after annealing at 300°C. The microstructural evaluation showed that residual stress of Cu affects the grain growth rate during annealing, which is closely related to the Cu/Si interdiffusion behavior.