Systematic calculations were used to study the competition between dislocation nucleation and void formation as the stress relaxation mechanism in Cu interconnects under thermal stress, which was related to the aspect ratio (ratio of the film thickness to width) of the Cu lines. It was quantitatively found from both elastic-perfectly plastic model and kinematic strain hardening model that there exists a critical aspect ratio, below and above which the stress relaxation was dominated by the dislocation nucleation and void formation, respectively. The critical aspect ratio was revealed to modulate by both the length scale of the interconnects and the interfacial strength between the Cu lines and surroundings, suggesting potential application to achieve artificial controlling on stress relaxation mechanism in Cu lines. The calculations were in good agreement with available experimental data.Competition between Dislocation Nucleation and Void Formation as the Stress Relaxation Mechanism in Passivated Cu Interconnects. J.Zhang, J.Y.Zhang, G.Liu, Y.Zhao, J.Sun: Thin Solid Films, 2009, 517[9], 2936-40