Degradation kinetics of ultrathin HfO2 layers on Si(100) during vacuum annealing monitored with in situ XPS/LEIS and ex situ AFM

The evolution of HfO2(3-5 nm)/SiO2(0.5 nm)/Si(1 00) stacks during vacuum annealing was monitored in situ with the combination of X-ray photoelectron spectroscopy and low energy ion scattering techniques and supplemented with atomic force microscopy analysis to investigate the mechanism that triggers HfO2 degradation with Hf silicide formation. The reduction of SiO2 interfacial layer and the formation of local paths for SiO escape into vacuum are believed to be critical at vacuum annealing above T> 850 degrees C for the reaction between HfO2, and Si to start and eventually lead to the degradation of the former. (C) 2007 Elsevier Ltd. All rights reserved.