Use of water vapor for suppressing the growth of unstable low-κ interlayer in HfTiO gate-dielectric Ge metal-oxide-semiconductor capacitors with sub-nanometer capacitance equivalent thickness

Annealing of high-permittivity HfTiO gate dielectric on Ge substrate in different gases (N2, NH3, NO and N2O) with or without water vapor is investigated. Analysis by transmission electron microscopy indicates that the four wet anneals can greatly suppress the growth of a GeOx interlayer at the dielectric/Ge interface, and thus decrease interface states, oxide charges and gate leakage current. Moreover, compared with the wet N2 anneal, the wet NH3, NO and N2O anneals decrease the equivalent permittivity of the gate dielectric due to the growth of a GeOxNy interlayer. Among the eight anneals, the wet N2 anneal produces the best dielectric performance with an equivalent relative permittivity of 35, capacitance equivalent thickness of 0.81 nm, interface-state density of 6.4 × 1011 eV− 1 cm− 2 and gate leakage current of 2.7 × 10− 4 A/cm2 at Vg = 1 V.