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 electric signals of the certain frequency can generate the bulk acoustic waves (BAWs) only into the interior of liquid, and this effect can be applied in fabricating the high-frequency BAW transducers. Theoretical simulation shows that a thin protective film NOD between piezoelectric crystal and liquid has less role for the BAW generation. The main advantage of this kind of BAW transducers is that the IDTs generate the BAWs into liquid directly without the need of impedance matching. The BAW transducers using IDTs with a central frequency of 31.5MHz are designed and fabricated, and the experimental results of frequency responses are consistent with theoretical model.