Effect of Electron Flow Direction and Via Number on Electromigration Mechanism for Copper Dual Damascene Interconnects

In this study, the effects of the via number and the current direction on electromigration characteristics in the dual-damascene Cu lines have been investigated. The results reveal an interesting difference in electromigration behavior of electron up-and down-flow directions on the multi-via structures. Increasing the via number results in a higher electromigration failure time and then reaches saturation for electron up-flow case. As for electron down-flow direction, the failure time is independent of the via number. Moreover, the failure time of Cu lines with via structure is lower than that without via structure. A higher current density at the triple junction site in the inner via is the possible mechanism, resulting in a shorter failure time and via-number independent. These observed effects are specific to Cu dual-damascene structures and can provide great technological implications in electromigration improvement. (C) 2010 The Japan Society of Applied Physics