Piezoelectric aluminum nitride resonator for oscillator

This work investigates properties of the thin film elongation acoustic resonator (TFEAR) operating at MHz frequencies in air. This resonator is composed of a piezoelectric layer of aluminum nitride (AlN) sandwiched between two aluminum electrodes (Al). TFEAR works in the extensional mode excited via AlN d₃₁ piezoelectric coefficient. A 3D-finite element method analysis (FEM) using ANSYS^reg software has been performed to model static modal and harmonic behavior of the TFEAR. In order to consider insertion losses into the substrate, equivalent electrical models based on modified Butterworth-Van Dyke (MBVD) circuit have been improved by adding extra dissipative elements. Thus, a whole model for the on-wafer characterization set-up is given, allowing for automatic de-embedding of the present TFEAR equivalent circuit. Quality factor Q as high as 2500 in air have been recorded with motional resistance lower than 400 Omega. A first oscillator based on a TFEAR resonator was also designed and tested.