Improved Quality Factor of Hetero Acoustic Layer (HAL) SAW Resonator Combining LiTaO3 Thin Plate and Quartz Substrate

A Hetero Acoustic Layer (HAL) SAW device is a new type of SAW device with a solidly mounted monocrystalline piezoelectric thin plate, which can obtain very high impedance ratio (ZR) and small temperature coefficient of frequency (TCF) at the same time. In this study, HAL SAW resonators using a LiTaO3 (LT) thin plate and a quartz substrate were investigated numerically and experimentally. The resonator fabricated using 20 degrees YX LT and 40 degrees Y90 degrees X quartz exhibited a bandwidth (BW) of 5.0%, a ZR of 82 dB and a Bode Q of 3,000, which have been significantly improved from our previous report. The performance is better by a factor of 1.2 times in BW, 31 dB in ZR and 6.4 times in Bode Q compared with a standard SAW resonator on 42 degrees YX LT, which was fabricated in the same facility. Further improvement in performance is expected after optimizing wafer cut angles, electrode metal and fabrication process.