Postvoiding FEM Analysis for Electromigration Failure Characterization

In this paper, we propose a novel finite-element method-based stress analysis for void growth process after the void is nucleated in the confined copper interconnects. We focus on the postvoiding analysis of void evolution, which remains challenging and less addressed in the past because void growth leads to transient structural changes in the copper interconnects. The new method explicitly considers the stress distribution’s impacts on the void volumes due to atomic conservation in confined wires. We introduce a phase-field equation that results in two coupled dynamic systems to describe the whole postvoiding stress evolution process. A novel regulated void growth velocity is introduced in order to consider the inherent physical interaction between the void volume and stress distribution in a confined interconnect wire. Numerical results show that the computed stress distributions and extracted current exponent values fit the measured results better than a recent postvoiding analysis work. Furthermore, the proposed electromigration analysis method models the Joule heating effect on wire resistance and temperature change, which were well observed in the published experiments.