Piezoelectric MEMS Disk-Shaped and Ring-Shaped Resonators Utilizing Lamb Wave

摘要

Objective: This paper discusses analytically and by simulation, a novel disk and ring-shaped piezoelectric micromechanical acoustic resonators in which asymmetric Lamb wave (A_0) mode is induced in a thin-film aluminum nitride (AlN)-on-silicon structure. Method: The piezoelectric resonators are designed and simulated at two-port state by the aid of FEM tool. An analytical investigation is carried out in order to study the propagation of asymmetric lamb wave in a cylinder structure. Circular electrodes are utilized for excitation of intended order of asymmetric acoustic Lamb wave (A_0) in the structures. Due to the significance of feedthrough capacitances in the piezoelectric MEMS resonators in high-frequency applications, these capacitances are calculated and extracted. Several electrodes and tethers configurations are introduced and simulated by FEM simulation in order to study distortion of resonator structures. Result: Stress-free nodal zones close to the resonators outer edge are identified and support tethers, which are used to anchor the resonators, are connected to those points by applying the notch method. Connecting anchoring tethers to stress-free nodal zones considerable decreased tether deformation leading to lower loss for resonators. The prototype models of structures work at 307 MHz and 318 MHz for the disk-shaped and ring-shaped resonators, respectively. Numerous transient and harmonic analysis have been carried out in order to study resonators behavior at the fundamental mode and their spurious electrical response. Conclusion: The proposed structures in this paper can be a promising choice for different applications ranging from RF filter, RF oscillators, RF micromachined circuits and physical and biochemical sensors.