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

High-resolution photoelectron spectroscopy with synchrotron radiation (energy resolution of 50meV) is used to investigate interfacial properties of Ge∕GeOx (1nm)∕HfO2 (1nm) 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 AlKα 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.