Dynamical x-ray microscopy investigation of electromigration in passivated inlaid Cu interconnect structures

Abstract

Quantitative time-resolved x-ray microscopy mass transport studies of the early stages of electromigration in an inlaid Cu line/via structure were performed with about 40 nm lateral resolution. The image sequences show that void formation is a highly dynamic process, with voids being observed to nucleate and grow within the Cu via and migrate towards the via sidewall. Correlation of the real time x-ray microscopy images with postmortem high voltage electron micrographs of the sample indicates that the void nucleation occurs at the site of grain boundaries in Cu, and that the voids migrate along these grain boundaries during electromigration.