HAL SAW resonators using LiTaO3 thin plate on quartz substrate

Surface acoustic wave (SAW) resonators with a moderate bandwidth and a large impedance ratio are obtained by Hetero Acoustic Layer (HAL) structure combing a LiTaO₃ (LT) thin plate and the substrate, which has a high velocity of leaky SAW and a small frequency temperature coefficient (TCF). In this study, a new type of HAL SAW resonators were fabricated using 0.5-1 μm thick 42°YX or 20°YX LT and 42°45'YX or 40°Y90°X quartz bonded together. An impedance ratio of 65-70 dB and a TCF of -26 ppm/°C were measured. Those impedance ratios are 13-21 dB better than that of a standard 42°YX LT SAW resonator fabricated in the same facility.