Statistical model for electromigration failure at aluminum contacts and terminals

The statistical model for electromigration failure in stripes developed by Attardo, Rutledge, and Jack has been extended to cover the cases of terminals and contacts to silicon. By the use of computer simulation techniques, a model was developed that relates the time-to-failure and the distribution of failures to the magnitude of the structural divergence occurring at the diffusion barrier. The model is then used to predict the dependence of contact or terminal reliability on grain size distribution, device geometry, and current crowding. In particular, the model predicts the previously unknown fact that for a constant grain size, a large standard deviation of the grain size at the contacts will retard electromigration and that the current density distribution at the contact does not affect mean time-to-failure.