Effect of thinning a WSiN/WSIx barrier layer on its barrier capability

We investigated the effects of tungsten silicon nitride/tungsten silicide ( WSiN/WSix) barrier layer thickness on its barrier capability. WSiN was obta ined by nitridizing the WSix surface with electron cyclotron resonance nitr ogen plasma. The total thickness of the WSiN/WSix barrier layer was reduced by thinning the initial WSix layer. When 5-nm-thick WSix was nitridized, t he N and Si contents in the WSiN/WSix layer became smaller than when WSix i nitial thickness was 20 nm. This barrier layer diffused into the copper (Cu ) layer when annealed, and did not act as a barrier layer. On the contrary, a WSiN/WSix barrier layer formed by nitridizing 10-nm-thick WSix showed go od barrier capability against Cu diffusion. We evaluated the leakage curren t between Cu damascene interconnections with this barrier layer and found t hat this barrier layer formed on-the trench side wall prevents Cu diffusion when the thickness on the side wall is over 10 nm. (C) 2001 American Vacuu m Society.