Modeling and fabrication of piezoelectric Aluminum Nitride resonator and its application in oscillators

This work investigates the TFEAR (thin film elongation acoustic resonator) operating at MHz frequencies. This resonator is composed of a piezoelectric aluminum nitride (AlN) layer sandwiched between two aluminum (Al) electrodes. The resonators are manufactured on a silicon substrate. In opposition to common resonator, TFEAR works in extensional (elongation) mode excited via AlN d₃₁ piezoelectric coefficient. A finite element analysis is performed to simulate the static and modal behaviors. The simulation is used to determine the geometry of each material so as to reach the desired frequency range and to compare theoretical and experimental results at different resonance frequencies. A modified Van-Dyke Butterworth (MBVD) equivalent circuit model is developed, including substrate losses. Samples have been measured and quality factor as high as 2500 in air have been measured. A first oscillator based on TFEAR resonator was designed and fabricated.