Effects of hot-isostatic pressing and annealing post-treatment on HfO2 and Ta2O5 films prepared by ion beam sputtering

Hafnium oxide (HfO2) films and Tantalum oxide (Ta2O5) films prepared by ion beam sputtering are important high refractive index materials from ultraviolet to near infrared. In this paper, Hot-isostatic pressing (HIP) technique is applied to the post-treatment of HfO2 and Ta2O5 films, and the effects of HIP and annealing treatment on optical and stress properties of the thin films were compared. Optical properties are mainly including thickness, refractive index, extinction coefficient, band gap (Eg), and tail energy (Eu), which were calculated by the inversion of spectral properties. And stress characteristics were calculated by the curvature change of the samples surface. The results show that the two post-treatment methods both can reduce refractive index and extinction coefficient of the thin films, and can effectively improve band gap of thin films. The annealing treatment is better than HIP for reducing the extinction coefficient of thin films. The tail energies of the thin films show a decreasing trend after post-treatment, which indicates the decrease of the defect density of local state and the disorder degree of microstructures. The change of stress after HIP treatment is less than that of annealing because of the homogeneous pressure in HIP post-treatment, but both the post-treatment methods can transform the stress properties of the films.