Analysis of electromigration in redundant vias

We analyze the electromigration material transport and stress build-up in dual-damascene interconnect structures with single and double vias. Two cases are studied: in the first, an effective diffusion coefficient is considered, representing the case where grain boundary diffusion is the dominant mechanism and the adhesion between the copper and the capping layer is strong. In the second, the effect of interfaces, based on the assumption that the copper/capping layer interface is the main path for diffusion, is considered. It is shown that the diffusion mechanism has a significant impact on the behavior of the redundant via structure. The influence of the via spacing is also discussed.