Crystal plasticity simulations of thermal stresses in thin-film aluminum interconnects

Abstract

Thermal stresses that develop in aluminum interconnects upon cooling from an annealing temperature are investigated using crystal plasticity theory. The crystal plasticity model is implemented assuming either isotropic hardening or a physically based hardening model developed for single crystals. The dependence of the predicted thermal stresses on crystal orientation and on interconnect aspect ratio is examined. The results are compared with recent observations of electromigration-induced transgranular voids to ascertain the contribution of the thermal stresses in the failure of aluminum interconnects. The analysis clearly demonstrates the necessity of accounting for all slip systems when modeling the effects of texture in single-crystal thin films. In addition, the calculations suggest that proper consideration of the hardening description is necessary for accurate predictions of thermal stresses.