Design and fabrication of high frequency bulk acoustic wave transducers using interdigital transducers

Interdigital transducers (IDTs) deposited at an interface of piezoelectric crystal-liquid and powered by electrical signals of certain frequency can generate bulk acoustic waves (BAWs) only into the interior of liquid, and this effect can be applied in fabricating high-frequency BAW transducers. Theoretical simulation results shows that a thin protective film (SiO₂) between piezoelectric crystal and liquid has fewer roles for the BAW generation. The main advantage of this kind of transducer is that IDTs generate BAWs into liquid directly without the need of impedance matching. A BAW transducer using IDTs with a central frequency of 31.5MHz is designed and fabricated, and the experimental measurement results of frequency response are consistent with theoretical model.