Impact of oxygen on Cu surface for highly reliable low-k/Cu interconnects with CuSiN and Ti-based barrier metal

A trade-off property of CuSiN between EM improvement and line resistance increase was resolved by a breakthrough that leaves oxygen at grain boundary of Cu line surface before CuSiN formation. Then, the combination of CuSiN and Ti-rich TiN (Ti(N)) barrier metal (-BM) was applied. Oxygen left by weakening process strength of CuO x reduction lowered line resistance, because Si diffusion causing line resistance increase was controlled by the oxygen at grain boundary. Low-damage process of CuO x reduction also improved voltage ramp dielectric breakdown (VRDB) property. Excellent EM performance brought about by CuSiN was kept by the combination with Ti(N)-BM, because the oxygen made Si and Ti distributions uniform at grain boundary of Cu surface by forming Ti-silicide. Cu atom transport that caused EM failure was suppressed throughout grain boundary of Cu surface.