Impacts of electrical properties and reliability on Ge MOS capacitors with surface pretreatment

Surface pretreatments with NO, N2O and NH3, are employed to prepare HfTiO/GeOxNy stack gate dielectric on n-Ge substrate. Impact of surface pretreatment on the electrical properties and reliability of the Ge MOS capacitors have been investigated. Excellent performances of Al/HfTiO/GeOxNy/n-Ge MOS capacitor with wet NO surface pretreatment have been achieved with an equivalent oxide thickness of 1.88 nm, physical thickness of 7.2 nm, equivalent permittivity of ∼ 34.5, interface -state density of 2.1×10¹¹ eV⁻¹cm⁻², equivalent oxide charge of −7.64×10¹¹ cm-2 and gate leakage current of 4.97×10⁻⁵ A/cm² at Vg = 1 V. Experimental results also indicate that the wet NO surface pretreatment can lead to excellent reliability.