Germanium out diffusion in SiGe-based HfO2 gate stacks

The authors report about a detailed study of the chemical composition of advanced HfO2/interfacial layer/SiGe stacks for future p-channel metal-oxide-semiconductor field-effect transistors. Several state-of-the-art characterization techniques are implemented to provide consistent and complementary information about interfacial chemical states and Ge diffusion along the stack. Angle-resolved x-ray photoelectron spectroscopy is performed in both standard and parallel modes. Results highlight the presence of elemental Ge in the HfO2, suggesting some Ge out diffusion from the SiGe substrate. This trend is confirmed by time-of-flight secondary ion mass spectrometry and plasma profiling time-of-flight mass spectrometry, a recently developed technique to monitor thin films compositions during device manufacturing. Published by the AVS.