Structure of Hafnium Silicate Films Formed by Atomic Layer Deposition

Hf distributions in as-grown and annealed (HfO2)(0.25)(SiO2)(0.75) films with thicknesses in the range 4-13 nm were investigated by high resolution transmission electron microscopy (HRTEM), angle resolved X-ray photoelectron spectroscopy (ARXPS) and medium energy ion scattering (MEIS). HRTEM images show a layered structure in films thinner than 8 nm. ARXPS data also show a non-uniform distribution of Hf throughout the film depth. A diffusion of SiO2 to the film surface after a longer time anneal was observed by MEIS. All these observations provide evidence for surface-directed spinodal decomposition in the pseudobinary (HfO2)(x)(SiO2)(1-x) alloy system.