Independent interface and bulk film contributions to reduction of tunneling currents in stacked oxide/nitride gate dielectrics with monolayer nitrided interfaces

Direct tunneling limits aggressive scaling of thermally-grown oxides to about ∼1.6 nm, a thickness at which the tunneling current at 1 V is ∼1 A/cm ². This paper presents experimental results, supported by interface characterizations and model calculations, which demonstrate that multi-layer or stacked gate dielectrics prepared by remote plasma processing comprised of (i) ultra-thin nitrided SiO ₂ interface layers, and (ii) either silicon nitride or oxynitride bulk dielectric films, can extend the oxide-equivalent thickness, t_ox-eq, limit down to ∼1.1-1.0 nm. A similar stacked gate dielectric, which substitutes higher- k oxides such as Zr(Hf)O ₂-SiO ₂ 'silicate' alloys or Ta ₂O ₅ for the nitrides or oxynitride alloys, is projected to further reduce t_ox-eq to ∼0.6-0.7 nm.