Electromigration characteristics of copper dual damascene interconnects - line length and via number dependence

In this paper, we attempt to combine short length and via number effects to study the impact on the electromigration (EM) characteristics of dual damascene Cu lines. The results revealed interesting differences in electromigration behaviours of long and short length Cu lines. Increasing via number resulted in a higher electromigration failure time, but is related to the line length. For multiple-via structures with short Cu length, electromigration lifetime was significantly enhanced due to obvious back-stress effect and single failure mechanism of line depletion. These observed effects are specific to Cu dual-damascene structures and can have great technological implications for electromigration assessment.