Effects of microvoids on the linewidth dependence of electromigration failure of dual-damascene copper interconnects

The electromigration lifetime of dual-damascene Cu interconnects was found to significantly decrease with increasing linewidth, for linewidths ranging between 0.2 and 2.25 μm. Voids were also found to preexist in these lines. When void nucleation is required for failure, the electromigration reliability is generally found to be at most weakly dependent on the linewidth. In contrast, the current study suggests that growth, drift, and accumulation of existing voids lead to the observed strong linewidth dependence.