Interface Layers for High-k/Ge Gate Stacks: Are They Necessary?

Abstract

We discuss the effects of interface layers between high-k gate insulators and the Ge substrate on the electrical characteristics of Ge MOS devices. Our work has focused on both germanium oxynitride (GeOxNy) and tantalum oxynitride (TaOxNy) interface layers. We find that ultrathin interface layers of TaOxNy, a high permittivity diffusion barrier, produce greatly improved charge trapping characteristics and promising capacitance scaling for high-k/Ge gate stacks. Effects of interface layers on interface state density and the frequency dispersion of the capacitance-voltage (CV) behavior under inversion are also described.