Mechanisms of electromigration in thin interconnects were studied in situ in a scanning electron microscope. The effect of grain boundaries, as important paths for diffusion, could be demonstrated because the initial grain structure was recorded by means of orientation mapping, using electron back-scattering diffraction techniques. The role played by grain boundaries having high misorientation angles, and large blocking grains, was investigated by comparing localized damage with the corresponding part of the orientation map. The formation of fatal voids was found to occur at the end of a large blocking grain followed by a high-angle grain boundary which was parallel to the current flow. Hillocks were formed at grain boundary triple-junctions where a high flux divergence occurred due to differing misorientation angles of the joined grain boundaries.

Study of Electromigration Damage in Al Interconnect Lines. A.Buerke, H.Wendrock, H.Wetzig: Crystal Research and Technology, 2000, 35[6-7], 721-30