Depth-resolved in-situ TEM observation of electromigration in a submicron-wide layered Al-0.5%Cu line

We studied electromigration (probably at similar to 350 degrees C) in a submicron-wide Al-0.5 wt%Cu-on-TiN line with a drift-velocity measurement structure by using depth-resolved (side-view) in-situ transmission electron microscopy. Voiding at the cathode was characterized by uniform thinning of a grain and by mass transport from no-current Bow ledges with a (111) faceted plane. The adjacent grain began to void when the grain upstream in the electron flow was almost depleted. The voiding proceeded in a manner similar to that in the upstream grain. Voiding between the cathode and the anode began mostly at the intersection of the Al top surface with grain boundaries. It proceeded mainly downward along the anode side of the grain boundary until it reached the Al bottom surface causing a gap in the Al. Then it grew laterally toward the anode. The cathode side surface of the void remained stationary during the void evolution.