Insights into effects of thermal annealing on optical properties of SiO2films

Abstract

Annealing is an important method to alter the properties of thin films. The effects of thermal treatment in air on optical properties of SiO₂ thin films were investigated. SiO₂ thin films were deposited on Si (110) substrates by an ion beam sputtering (IBS) technique, and then annealed in air under different thermal annealing time of 16 hours, 24 hours, 36 hours, 64 hours and the temperature from 100℃ to 600℃ with 24 hours. Optical properties refractive index and thickness are studied directly after deposition and after thermal treatment, and they are measured by spectroscopic ellipsometry. When the thermal annealing temperature was fixed at 300℃, the refractive index of SiO₂ films would reduce with the increase of the thermal annealing time, the optical thickness also reduced but the various quantities are almost the same. The refractive index of SiO₂ films changed with the different thermal annealing temperature. As the annealing temperature increased, the refractive index of SiO₂ films reduced gradually. When the selected annealing temperature is 500℃, the refractive index of SiO₂ films reached minimum. It can be found that the optical properties of SiO₂ thin films can be improved by an adapted annealing procedure.