Behavior of electromigration-induced gaps in a layered Al line observed by in situ sideview transmission electron microscopy

We observed the detailed behavior of electromigration-induced gaps (voids that cause an open circuit) in a submicron-wide Al line layered on a Ti/TiN conductor by in situ sideview transmission electron microscopy. Two types of gaps were observed. The first type is characterized by extensive growth, which may make the Ti/TiN shunt ineffective under use conditions. The gap causes a decrease in the Al drift velocity upstream in the electron flow. This decrease probably results from mass transport through the exposed TiN surface into the gap. The second type of gap did not grow and later healed; therefore, the shunt seems to be effective. The gap had little influence on the drift velocity. Mass was transported directly from the cathode-side Al segment through the gap to the anode-side segment. These mass transport processes may be the causes of resistance oscillation in layered lines. (C) 1996 American Institute of Physics.