Effects of postdeposition annealing on the structure and optical properties of YOxNy films

Abstract

High-k gate dielectric YOxNy films were prepared by reactive sputtering. The effects of postdeposition annealing on the structure and optical properties of YOxNy films have been investigated. The x-ray diffraction result shows that the crystallization starts at the annealing temperature of 500°C. Spectroscopic ellipsometry was employed to determine the optical properties of a set of YOxNy films annealed at various temperatures. It was found that the refractive index (n) of YOxNy films decreased with the increase of annealing temperature below 600°C, whereas it increased with increasing annealing temperature above 600°C. The annealing-temperature dependence of the optical band gap of YOxNy films was also discussed in detail. It has indicated that the optical band gap of YOxNy films shifts to higher energy after higher temperature annealing, which is likely due to the reduction of N content and the change of crystalline structure in YOxNy films.