A model for electromigration failure distributions of contacts and vias in advanced IC technologies

Electromigration failure of contacts and vias in deep submicron IC technologies is the key concern for interconnect reliability. We present a physical model for electromigration failure of contact and vias in deep submicron technologies. We show that this model can be used to develop a complete description of the behavior of failure distributions of contacts and vias that is in very good agreement with experimental observations. The basic premise of the model is that failure is controlled by the electromigration-induced drift of the conductor away from the contact or via. The failure time of the contact or via is determined by the drift velocity of the conductor and the contact or via geometry. The model predicts that the median time-to-fail (MTF) exhibits a 1/(j-j_c) dependence on current density. Most significantly, however, the model shows that the lognormal failure time dispersion, a also exhibits a 1/(j-j_c) dependence, as well as a strong temperature dependence, and that these effects are inherent properties of contacts and vias. We compare model predictions for failure distributions to experimental data to establish the validity of the drift model