Influence of stress on the transmission characteristics of multilayer thin films.

The relationship between multilayer film strains and film thickness changes was analyzed based on the stress formula and the small flexibility principle of elasticity. A theoretical model of the relationship between changes in substrate curvature and film thickness was established, and the formula of every layer thickness with uneven changes of multilayer films was obtained for the spectra of the before-thinning and after-thinning filter. Both the simulated result for a narrow bandpass filter and experimental results showed that nonuniformities in the film thickness caused by substrate curvature changes are one of the main reasons for spectrum degradation in narrow bandpass filters.