Phase separation and electronic structure of Hf-silicate film as a function of composition

Thermal stability and electronic structure of xHf O2 · (100-x) Si O2 (HfSiO) (x=25%, 50%, and 75%) grown by atomic layer deposition were investigated by various measurement tools. The quantity of incorporated Si O2 content changes the binding energy of Hf O2 as the charging effect in the silicate is enhanced with the quantity Si O2. When the annealing temperature is increased over 800 °C, phase separation between Si O2 and Hf O2 is observed in the films with 50% and 75% Hf O2, while it does not occur in a Hf-silicate film with a high mole fraction of Si O2. The phase separation begins in the surface region via the segregation of Si O2. After the annealing treatment, the quantity of Si O2 supplied to the film surface due to interfacial interactions influences the phase separation process, resulting in no phase separation being observed, even at a high annealing treatment of 900 °C.