Changeable electromigration failure mode in wide Cu interconnects

The electromigration (EM) failure mode of wide via-line Cu interconnects, together with the current density exponent, is shown to be changeable with current density at common package-level acceleration conditions. As the stress current density increases, the resistance of upstream interconnect is more likely to exhibit open jump at EM failure. Failure analysis shows Ta-based liner at the Via is broken at high currents, and isolated Via voiding overwhelms the line voiding and becomes responsible solely for the EM failure. Finite element simulation suggests the inhomogeneous current density in the Via and line may dominate the EM kinetics at high currents.