Structure Design And Processing Simulation Of Piezoresistive Silicon MEMS Resonator

Compared with quartz resonators, MEMS resonator has advantages of high quality factor, low temperature drift, excellent phase noise performance, low power consumption, and especially the compatibility with the CMOS fabrication process which makes MEMS resonator promisingly to replace quartz resonator in the future integrated circuit systems.Piezoresistive silicon MEMS resonator is electrostatic actuated and the motion is detected by the piezoresistive effect of silicon. Different from other resonators such as electromagnetic and piezoelectric, it only needs silicon, the basic IC material, without needing other special materials. Compared with the capacitive MEMS resonator, it has low output resistance and can be highly integrated in the circuit.In this thesis, we analysed the piezoresistive silicon MEMS resonator with resonant frequency over hundreds of MHz by COMSOL Multiphysics simulation software. Frequency responses of the resonators with four geometrical structures were studied. The relationships between the critical dimension and the resonant characteristics such as resonator frequency, quality factor and output voltage were calibrated when scaled down with feature size of5μm,1μm,500nm,350nm,180nm,100nm and50nm, respectively. By optimizing the structure, a906.4MHz resonator with the quality factor of4352under the critical dimension of500nm and a1.3GHz resonator with the quality factor of2817under the critical dimension of350nm were obtained with great application potential. The fabrication process of the resonator was simulated by SILVACO TCAD focusing on the photolithographic and RIE etch process.