High coupling and highly stable leaky surface acoustic waves on LiTaO₃ thin plate bonded to quartz substrate

Abstract

The propagation properties and resonance characteristics of leaky surface acoustic waves (LSAWs) and longitudinal-type LSAWs (LLSAWs) on a LiTaO3 (LT) thin plate bonded to an AT-cut quartz substrate were investigated experimentally. For the LSAWs and LLSAWs, the bonded structures of 36°Y-cut X-propagating LT (36°YX-LT)/AT-cut 90°X-propagating quartz (AT90°X-quartz) and X-cut 31°Y-propagating LT (X31°Y-LT)/AT-cut 45°X-propagating quartz (AT45°X-quartz) were fabricated, respectively. For the LSAW on 36°YX-LT/AT90°X-quartz, the electromechanical coupling factor (K2) of 11.1% was obtained at an LT thin-plate thickness of 0.25 wavelength, whereas K2 for a single LT substrate was measured to be 5.7%. For the LLSAW on X31°Y-LT/AT45°X-quartz, K2 increased from 2.8% for the single LT substrate to 7.2% at an LT thin-plate thickness of 0.14 wavelength. Furthermore, K2 of approximately 12% and the temperature coefficient of frequency (TCF) of 0 ppm/°C were theoretically obtained simultaneously for the LSAW on 36°YX-LT/AT-cut 90°X-quartz at a certain thin-plate thickness.

Low-Residual-Stress Amorphous Film for LiTaO₃/Quartz or LiNbO₃/Quartz Bonding toward 5G Surface Acoustic Wave Devices

“…Transactions of The Japan Institute of Electronics Packaging Vol. 13,2020 stress σ th and the intrinsic stress σ i using the relation…”

“…Transactions of The Japan Institute of Electronics Packaging Vol 13,. 2020 pre-4G SAW substrates, but the conventional thick LT or LN substrates do not meet the requirements of 5G SAW.…”

Behaviors of higher-order modes in I.H.P. SAW devices and discussion of their suppression

“…Elsewhere, another type of device with a similar concept employing layered LT/quartz substrate has been reported by some researchers. [16][17][18][19][20][21][22][23][24][25][26][27][28] For this type of device, the suppression of higher-order modes while keeping other characteristics has been realized by optimizing the cut angle of quartz. 26) However, since the thermal conduction of quartz is not good, the power durability of this type of device is probably inferior compared with I.H.P.…”

Transverse energy confinement and resonance suppression in SAW resonators using low-cut lithium tantalate

“…SAW, have aroused appreciable interest owing to its small temperature coefficient of frequency and high quality factors (Q) owing to excellent acoustic energy confinement. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Despite the fact that energy can be well confined to the surface, there still remains lateral energy leakage through the busbar which causes excess loss. For its ultimate reduction, lateral edges including busbars and gaps between electrode finger tips must be designed properly.…”