Medium energy ion scattering has been used in combination with O16 and O18 isotope tracing to determine elemental depth distributions and elucidate oxygen transport in 2-5 nm thick HfO2 and HfSiOx films grown by atomic layer deposition on Si(001). Both the oxygen isotope exchange rate in the dielectric as well as the interfacial silicon oxide growth rates were examined as a function of time, temperature, film stoichiometry (HfO2, HfSiOx, and HfSiOxNy), and crystallinity. The amount of exchanged oxygen in the oxide was found to decrease with increasing SiO2 content. When the SiO2 to HfO2 ratio reaches 1:1 in HfSiOx an almost full suppression of the oxygen exchange is observed. The activation barrier for the SiO2 growth at the HfO2/Si and HfSiOx/Si interfaces was found to be much lower than that in the SiO2/Si and SiOxNy/Si cases, which is attributed to distinctly different oxygen incorporation mechanisms. The primary route for oxygen delivery to the interface responsible for the SiO2 growth is via exchange, however, direct oxidation by molecular oxygen cannot be discounted completely. In the presence of an interfacial nitride layer the O18-O16 exchange is replaced by the O18-N exchange, which slows diffusion and reduces the oxidation rate.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Mar 25 2011|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics