Structure and optical properties of HfO2 thin films on silicon after rapid thermal annealing

HfO2 thin films have been deposited on Si substrate by radio frequency reactive magnetron sputtering. The optical and structural properties of HfO2 thin films in relation to rapid thermal annealing (RTA) temperatures are investigated by spectroscopic ellipsometry (SE), X-ray diffraction (XRD) and UV Raman spectrum. XRD and Raman measurements show that the as-deposited films are mainly amorphous and a transition to a crystalline phase occurs after RTA. Based on a parameterized Tauc–Lorentz dispersion model, the optical constants of the as-deposited and annealed films are systematically extracted. With increased annealing temperature, the refractive index n and the extinction coefficient k are observed to increase. The changes of the complex dielectric functions with annealing temperature are also discussed.