The effectiveness of a thin refractory metal layer inserted into a Ta film by ion-assisted deposition as a diffusion barrier between copper and silicon

In order to increase the failure temperature of a Ta diffusion barrier for Cu, we investigated the effect of adding of a thin refractory metal layer into a Ta film with/without ion bombardment on the Ta diffusion barrier performance in Cu metallization. The insertion of a thin Zr, W, Nb, or V layer into the Ta film improved the barrier properties significantly when the barrier layers were deposited with concurrent ion bombardment. The improvement of Ta diffusion barrier property was attributed to a densification of the grain boundaries in the films and to the formation of two thermally stable sharp interfaces between the Ta and the V by the ion bombardment, thereby retarding the Cu diffusion through Ta/V/Ta films.