Interface structure and non-stoichiometry in HfO2 dielectrics

High-resolution electron microscopy, electron energy-loss spectroscopy, and first-principles theory are used to investigate the composition and electronic structure of HfO2 dielectric layers deposited directly onto Si. A thin, nonstoichiometric, but Hf-free SiO2 layer forms between the HfO2 dielectric and the substrate, consistent with one-dimensional spinodal decomposition. Rapid thermal annealing crystallizes the HfO2, and the resulting grain boundaries within the HfO2 are found to be O-depleted, with localized states within the bandgap. These localized states are thought to act as significant leakage pathways, and may be responsible for Fermi-level pinning at the dielectric/contact interface. (C) 2004 American Institute of Physics.