Quantitative time-resolved X-ray microscopic mass transport studies of the early stages of electromigration in an inlaid Cu-line/via structure were performed at a lateral resolution of about 40nm. The image sequences showed that void formation was a highly dynamic process, with voids nucleating and growing within the Cu via and migrating towards the via side-wall. Correlations of the real-time X-ray microscopic images, with post mortem high-voltage electron micrographs of the sample indicated that void nucleation occurred at the sites of grain boundaries in Cu, and that the voids migrated along these grain boundaries during electromigration.
Dynamic X-Ray Microscopy Investigation of Electromigration in Passivated Inlaid Cu Interconnect Structures. G.Schneider, G.Denbeaux, E.H.Anderson, B.Bates, A.Pearson, M.A.Meyer, E.Zschech, D.Hambach, E.A.Stach: Applied Physics Letters, 2002, 81, 2535-7