Surface pretreatments for preparing HfTiO/GeOxNy stack gate dielectric on n-Ge substrate have been investigated.Excellent performances of Al/HfTiO/GeOxNy /n-Ge MOS capacitor have been achieved with an equivalent oxide thickness of 1.44 nm,physical thickness of 7.2 nm,equivalent permittivity of ~ 35,interface-state density of 2.1×1011 eV-1cm-2,equivalent oxide charge of-1.96×1012 cm-2 and gate leakage current of 2.71×10-4 A/cm2 at Vg = 1 V.Experimental results also indicate that the wet NO pretreatment can lead to excellent interface and gate leakage properties.The involved mechanisms lie in N-barrier role and N incorporation in GeOxNy interlayer,effectively preventing further growth of unstable GeOx during subsequent processing.
