MOCVD fluorine free WSi x metal gate electrode on high- k dielectric for NMOS technology

Abstract

We report material and electrical properties of tungsten silicide metal gate deposited on 12 in. wafers by chemical vapor deposition (CVD) using a fluorine free organo-metallic (MO) precursor. We show that this MOCVD WSi x thin film deposited on a high- k dielectric (HfSiO:N) shows a N+ like behavior (i.e. metal workfunction progressing toward silicon conduction band). We obtained a high- k/WSi x /polysilicon “gate first” stack (i.e. high thermal budget) providing stable equivalent oxide thickness (EOT) of ∼1.2 nm, and a reduction of two decades in leakage current as compared to SiO 2/polysilicon standard stack. Additionally, we obtained a metal gate with an equivalent workfunction (EWF) value of ∼4.4 eV which matches with the +0.2 eV above Si midgap criterion for NMOS in ultra-thin body devices.