Medium energy ion scattering has been used in combination with ${}^{16}\mathrm{O}$ and ${}^{18}\mathrm{O}$ isotope tracing to determine elemental depth distributions and elucidate oxygen transport in 2–5 nm thick HfO${}_2$ and HfSiO${}_x$ 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 (HfO${}_2$, HfSiO${}_x$, and HfSiO${}_x$N${}_y$), and crystallinity. The amount of exchanged oxygen in the oxide was found to decrease with increasing SiO${}_2$ content. When the SiO${}_2$ to HfO${}_2$ ratio reaches 1:1 in HfSiO${}_x$ an almost full suppression of the oxygen exchange is observed. The activation barrier for the SiO${}_2$ growth at the HfO${}_2$/Si and HfSiO${}_x$/Si interfaces was found to be much lower than that in the SiO${}_2$/Si and SiO${}_x$N${}_y$/Si cases, which is attributed to distinctly different oxygen incorporation mechanisms. The primary route for oxygen delivery to the interface responsible for the SiO${}_2$ growth is via exchange, however, direct oxidation by molecular oxygen cannot be discounted completely. In the presence of an interfacial nitride layer the ${}^{18}\mathrm{O}$-${}^{16}\mathrm{O}$ exchange is replaced by the ${}^{18}\mathrm{O}$-N exchange, which slows diffusion and reduces the oxidation rate.

• Received 30 November 2010

DOI:https://doi.org/10.1103/PhysRevB.83.115329