Effects of thickness and annealing on the residual stress of TiO2 film

Abstract

Film stress will lead optical elements to distort in the surface shape; it must be studied for manufacturing high surface accuracy optical thin film. As the most commonly used film material in the visible/near-infrared spectrum, it is essential to research the state of stress in TiO2 film. The orthogonal experiment approach is used to investigate the impact of film thickness, annealing temperature, and annealing time on the residual stress of the TiO2 film deposited by EBE. It is shown that the film thickness effects the residual stress most. The order in which the residual stress varies with respect to the film stress, annealing temperature, and annealing time is then given, and the AFM test is utilized to explore the cause of the change in the residual stress. This study is of great benefit for designing low-stress optical film systems and preparing ultra-low surface shape accuracy thin film devices.