General model for mechanical stress evolution during electromigration

A model is presented for the development of stress during electromigration. Formally similar to a thermal stress model, it provides a method of calcul ating all of the components of the stress tensor and clearly couples vacanc y transport and stress evolution with the boundary conditions that apply to the metal. Analytic solutions are discussed for electromigration either no rmal or parallel to a plate. The solution parallel to a plate is used to re interpret x-ray microdiffraction experiments from the literature. We find t hat the effective charge for vacancies in pure polycrystalline aluminum at 533 K is about 0.84. Using parameters that were either measured or calculat ed with the embedded atom method, our model displays good agreement with bo th transient electromigration data and drift data. (C) 1999 American Instit ute of Physics. [S0021-8979(99)01218-9].