Theoretical, numerical and experimental study of residual stress effect on two microresonators for acoustic sensing

Residual stress during the micro-fabrication process has been one of the main issues in many MEMS/NEMS sensors and actuators, especially acoustic sensing. We conduct theoretical, numerical and experimental study on the residual stress effect on the frequency responses of two types of polysilicon micro circular resonators: clamped and residual stress (RS) free design which can release the process-induced stress and is of easy fabrication. The measured natural frequency of the fabricated device is 39.8 kHz, in good agreement with both theoretical and FEM simulation results. We also determined the natural frequencies of these two designs as a function of residual stress. Under the same experimental RS condition of 50 MPa, the normalized changes of natural frequencies of these two designs are 159.7% versus 0.8%, respectively.