Improvement of Gate Oxide Reliability for Direct Tungsten-Gate Using Denudation of WNx

We investigated a gate oxide reliability of metal-oxide-semiconductor capacitors with W and denuded WNx gate. A 5.5 nm-thick SiO2 was used as gate dielectric. The W gate was deposited by D.C. magnetron sputtering and the denuded WNx gate was formed by N2 annealing following the deposition of WNx. The leakage current and charge-to-breakdown results indicate that the denuded WNx gate shows improved gate oxide reliability comparing with pure W gate. It is believed to be due to the segregation of nitrogen atoms at the interface of W and SiO2 film. It is also observed that the sputtering power must be reduced to improve the roughness of metal/SiO2 interface.