Some mechanisms for the incorporation of hydrogen in Hf-based gate dielectric films on Si

Hf-based materials are the leading candidates to replace SiO2 gate dielectrics in future Si-based metal-oxide-semiconductor field-effect transistors and H inside gate dielectrics has recognized roles on device performance and reliability. In this context, by employing nuclear reaction analyses of H-1 and H-2 nuclides as well as X-ray photoelectron spectroscopy, H incorporation in HfSiO, HfSiN, and HfO2 films on Si was accessed. Two technologically relevant H sources were investigated, namely annealing in H-2 at 400-600 degrees C and room temperature exposure to water vapour. We found that annealing in H-2 leads to high (when compared to SiO2) bulk H incorporation in HfSiO and HfSiN films, probably reflecting higher density of H trapping sites in these Hf-based materials. On the other hand, H incorporation in HfO2 films occurs mainly at HfO2 surface, without measurable H incorporation in HfO2 bulk. Moreover, by exposing HfO2 films on Si to water vapour we showed the formation of a hydroxylated HfO2 surface as well as migration of water-derived species through HfO2 films, incorporating water-derived species at the interfacial region between HfO2 and Si. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.