Improved bulk acoustic wave resonator using edge method for high performance

We investigate the performance of aluminum nitride (AlN) resonator based bulk acoustic wave (BAW) structure made with air edge reflector and gold (Au) edge electrode. BAW Resonators have been fabricated, some devices using a thick film of e-beam evaporated gold as edge electrodes at the border of the resonator on bottom, top electrode. The air reflectors provided at the border of the resonator suppress the acoustic wave leakage through lateral direction. We have developed the simulation and measurement for the improving of resonator quality. The influence of the frame width on resonator surface after applied the air edge reflector and the gold edge electrode in the performance of the BAW resonators is analyzed. The Q_a (Q-factor at anti-resonance frequency) and the effective electro-mechanical coupling coefficient (kt²) which is essential to achieve low loss and wide band-width of RF filters is increased by 19 % and 3.4 %, respectively. Also, Insertion loss at S₂₁ parameter is improved significantly from -0.095 dB to -0.041 dB.