The advanced back-end module of very-large-scale-integrated-circuits (VLSIs) requires an ultrathin diffusion barrier layer between the Cu interconnect and low-K oxides. In this letter, we investigated the electrical properties of the barrier layer formed by a Ta-Mn alloy. A diffusion barrier layer self-formed at the interface during annealing, and the .Ta/MnSi bilayer structures were investigated by standard microscopy. Black's equation and the measured mean-time-to-failure (MTTF) were used to obtain the reliability characteristics under different temperatures and current densities. The reliability is approximately two times better than that of the conventional TaN/Ta counterpart. The confidence intervals at 95% for each MTTF confirmed the single failure mode, and the electromigration phenomenon was observed to be the failure mechanism. Our results provide evidence that is a promising barrier material for Cu interconnects in VLSIs.
- Cu interconnect
- diffusion barrier