Stress modeling of periodic optical multilayer stack

The analysis of the residual in film is crucial to the fabrication of high accuracy multilayer device because it makes significant effects on the surface shape of the optical device. Based on film structure and deposition process, the periodic multilayer stack was reconstructed and then the residual stress model for periodic mutilayer stack was established. The model was related to the reference wavelength λ₀, the residual stress in a single cycle σ_C, the numble of the cycles m, and the interfacial stress between the cycle σ_C|C. By designing and depositing a periodic multilayer with a reference wavelength λ₀=900 nm, the residual stress of the sample was then calculated using the model and substrate deformation method. Comparison reveals that there is a about 30% error in the residual stress between estimating using the stress model and the measuring result. This demonstrates that the periodic multilayer stress model established in this study has high accuracy and qualifies for the stress estimation of periodic multilayer stack, further improving the accuracy of residual stress estimation of perodical multilayer stack.