Effect of thin V insertion layer into Ta film on the performance of Ta diffusion barrier in Cu metallization

Abstract

In order to increase the failure temperature of Ta diffusion barrier for Cu, we investigated the effect of a thin V insertion layer ͑100 Å͒ into Ta film with/without ion bombardment on Ta diffusion barrier performance in Cu metallization. When the Ta/V/Ta diffusion barrier was deposited without concurrent ion bombardment, the insertion of the thin V layer into Ta film was not effective to improve the barrier performance of Ta film, because of the thermal instability of the Ta/V/Ta multilayer caused by the reaction between the Ta/V/Ta films and Si substrate. Meanwhile, when the Ta/V/Ta diffusion barrier was deposited with ion bombardment, the insertion of the thin V layer into Ta film improved barrier properties significantly. This was attributed not only to the densification of grain boundaries in Ta/V/Ta films, but also to the formation of two thermally stable sharp interfaces between Ta and V by ion bombardment, resulting in the reduction of the fast diffusion of Cu through Ta/V/Ta films.

Diffusion Barriers

“…Thus, it is concluded that Cu diffusion into silicon promotes TaSi 2 grain growth [81]. Further possibilities include the incorporation of CeO 2 into Ta grain boundaries [87] as well as the insertion of an additional Zr [88] or V film [89] into the Ta barrier. Yin et al [83] demonstrated that heat treatment in vacuum at pressure p 0 ≈ 1 Pa leads to O diffusion along Cu grain boundaries into the Cu/Ta interface and, consequently, to the formation of a thin amorphous Ta oxide layer.…”