Micro-Raman spectroscopy analysis of residual stress in polysilicon MEMS resonators

This paper presents the recent results of utilization of micro-Raman spectroscopy to measure and characterize residual stress in polysilicon doubly-clamped MEMS resonators with small lateral size. Due to imprecise prediction of the magnitude of intrinsic residual stress, detrimental effect of the residual stress severely shifts the resonant frequency of MEMS resonator from the analytical pre-designed value. The stress is not only determined by the fabrication process but also related to the structural dimensions of resonators. In this work, microRaman spectroscopy was used to measure the residual stress of resonators with widths down to 2μm. The results show that the optimized resonator with length shorter than 50μm and width between 3.2μm and 4.1μm exhibits minimum residual stress.