A new, general model for mechanical stress evolution during electromigration

A new model is presented for the development of stress during electromigrat ion. Formally similar to a thermal stress model, it provides a method of ca lculating all of the components of the stress tensor and clearly couples va cancy transport and stress evolution with the boundary conditions that appl y to the metal. Analytic solutions are discussed for electromigration eithe r normal or parallel to a plate. The latter is similar to the metallization in experiments by Wang et al., permitting us to reinterpret these experime nts. We find that the effective charge for vacancies in pure polycrystallin e Al at 533 K is about 1.3. Using parameters that were either measured or c alculated with the Embedded Atom Method, our model displays good agreement with both transient electromigration data and drift data. (C) 2000 Publishe d by Elsevier Science S.A. All rights reserved.