Depth Profiling of Chemical and Electronic Structures and Defects of Ultrathin HfSiON on Si(100)

Abstract

We present in-depth profiling of chemical bonding features and defect state density in ultrathin HfSiOxNy (Hf/(Hf+Si)=~43%) films with average nitrogen contents up to ~18at.% by using x- ray photoelectron spectroscopy (XPS) and total photoelectron yield spectroscopy (PYS) in combination oxide thinning in a dilute HF solution. It is found that the oxygen content becomes its minimum around ~1.2nm from the surface while the nitrogen content becomes its maximum within ~1.5nm from the surface. The result suggests that the surface re-oxidation is promoted coincidentally with the diffusion of N atoms generated by thermal decomposition of the Hf-Nx units during the N2-annealing. The depth profile of the defect states, which was derived from the change in the yield, shows that the defect state density becomes its maximum in the near-surface region where oxygen deficiency becomes significant. It is likely that the imbalance in chemical coordination between anions and cations is responsible for the defect generation.