A well-posed moving boundary-value problem, describing the dynamics of curved interfaces and surfaces associated with voids and/or cracks that interacted with grain boundaries, was derived. Extensive computer simulations were performed for void configuration evolution during intergranular motion, under the actions of capillary and electromigration forces in thin-film metallic interconnects with bamboo structures. An analysis of experimental data, using the mean time-to-failure formulae derived here, gave consistent values for the interface diffusion coefficients and the enthalpies of voids. The expression, 5.85 x 10–5exp[–0.95(eV)/kT]m2/s, was obtained for voids that formed within the interior of the Cu interconnects; avoiding any surface contamination. The expression, 1.80 x 10–4exp[–1.20(eV)/kT]m2/s, was obtained for voids that nucleated at triple junctions or at grain-boundary surface intersections, where impurities such as Si, O, S - or even C - segregated during metallization and annealing, and could act as trapping centres for hopping vacancies.

T.O.Ogurtani, E.E.Oren: Journal of Applied Physics, 2004, 96[12], 7246-53