Mechanism for early failure in Cu dual damascene structure

An infrared microscope and a convergent electron beam technique have been applied to detect and analyze the weak via in a Cu dual Damascene contact chain. It is shown that the early failure is due to cracking in the barrier metal layer, which opens up a fast diffusion path along the interface between the barrier metal and the dielectric. The subsequent opening and, in some cases, self-recovery of the via is also discussed. This early failure mode may impose severe limitation on the scalability of the dual Damascene structure.