A Design For Capacitive MEMS Silicon Bulk Acoustic Wave Resonator

In this paper, a capacitive MEMS silicon bulk acoustic wave resonator is designed.Firstly, the working principle of the resonator is analysed, the dynamic model andequivalent circuit model are established. The resonator is simulated by ANSYS finiteelement analysis software, the simulation shows that the resonance frequency is108MHzwhich is consistent with the theoretical one, and depends on silicon material properties anddevice size. In order to improving the quality factor, the loss mechanisms are researched, itshows that except for air damping, the support loss or anchor loss is the domiantmechanism. And from the perspective of vibration mode and transmission line model,some feasible methods for reducing support loss are put forward, including placing thesupport beams at the nodal points, making the beam length equal to a quarter of the elasticwavelength, and setting acoustic reflectors at the substrate. In addition, the relationshipsbetween the motional resistance and DC bias, quality factor, capacitance gap are analyzed,it indicates that in the case of high quality and small capacitance gap, the motionalresistance is only several hundred ohms.Secondly, based on the above performance parameters of the design, the fabricationprocess based on SOI (Silicon-On-Insulator) is proposed, and the layout is designed. Andthe problems which are in the flow of fabrication are analyzed and solved.Finally, in order to predicte the influence factors of S21result and have a forecst, ADS(Advanced Design system) software is used to simulated the electrical model of the bulksilicon resonator, and the test platform is also setup.