Objective: This paper discusses analytically and by simulation, a novel disk and ring-shaped
piezoelectric micromechanical acoustic resonators in which asymmetric Lamb wave 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 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.