Effects of residual stresses in thin films on performances of MEMS-based microgratings

Effects of residual stresses on the optical and mechanical performances of MEMS-based microgratings were investigated using finite element simulation method. The results show that larger the tensile residual stress, more advantageous to improve the working optical efficiency of microgratings. However, as the tensile residual stress increases, driving voltage required for operating the grating structures is greatly enhanced, which makes the design and making of driving circuitry more complicated. Meanwhile, maximum working displacement of the grating structures will be decreased notably with the tensile residual stress increasing, restricting the application fields. In addition, structural resonant frequency will also be increased, affecting the working bandwidth of the gratings. As a result, to meet the demand of design, sufficient considerations for the effects of residual stresses on the performances of micrograting structures should be taken and strict control of the residual stresses during process should be performed.