Identification and Analysis of Dominant Electromigration Failure Modes in Copper/Low-K Dual Damascene Interconnects

We investigate the electromigration-induced void morphologies that dominate the reliability of Cu/low-k dual damascene vias. We observe that while voids form in both the upper and lower metal levels during electromigration stress, slit-type voids underneath vias fundamentally dominate the reliability of vias. Early failure distributions are common-place for Cu dual-damascene vias, and we show that multi-link structures are a necessary and efficient means to ensure that all potential voiding modes are characterized during accelerated testing. Additionally we find via reliability is a function of width of the stripe attached to vias, and electromigration must be investigated across a wide width range to ensure that the limiting geometry is correctly identified