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

Abstract

Annealing of high-permittivity HfTiO gate dielectric on Ge substrate in different gases (N 2, NH 3, NO and N 2O) 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 GeO x interlayer at the dielectric/Ge interface, and thus decrease interface states, oxide charges and gate leakage current. Moreover, compared with the wet N 2 anneal, the wet NH 3, NO and N 2O anneals decrease the equivalent permittivity of the gate dielectric due to the growth of a GeO xN y interlayer. Among the eight anneals, the wet N 2 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 × 10 11 eV - 1 cm - 2 and gate leakage current of 2.7 × 10 - 4 A/cm 2 at V g = 1 V. © 2008 Elsevier B.V. All rights reserved.