High-resolution photoelectron spectroscopy of Ge-based HfO2 gate stacks

High-resolution photoelectron spectroscopy with synchrotron radiation (energy resolution of 50 meV) is used to investigate interfacial properties of Ge/GeOx (1 nm)/HfO2 (1 nm) gate stacks. With soft x rays, a reliable Ge3d core-level study is possible thanks to the much lower cross section of the Hf5p core level than that using Al Kalpha radiation. It is clearly shown that Hf-germanate bonding states are formed at the GeOx/HfO2 interface, with an additional Ge3d spectral component shifted to lower binding energy relative to GeO2.