Sub-3 DB Insertion Loss Broadband Acoustic Delay Lines and High Fom Resonators in LiNbO3/SiO2/Si Functional Substrate

This work demonstrates high-performance shear-horizontal surface acoustic wave (SH-SAW) delay lines at 910 MHz with low insertion loss (IL) of 2.6 dB and wide fractional bandwidth (FBW) of 8.8% in thin film LiNbO
3
/SiO
2
/Si functional substrate. The SH-SAW acoustic delay lines (ADLs) based on X-cut LiNbO
3
thin film and gold (Au) electrodes show a group velocity (V
g
) of 4,300 m/s and a propagation loss of 10.1 dB/mm, which yields an effective quality factor (Q
PL
) of 675. To validate the Q
PL
from the delay line measurement, a 969 MHz one-port SH-SAW resonator at a similar operation frequency was designed on the same chip and presents high effective electromechanical coupling factor $\left( {k_{{\text{eff}}}^2} \right)$ up to 38.5% and maximum Bode-Q (Q
max
) of 848, resulting in a high figure-of-merit (FoM) of 326. The low-loss behavior of SH-SAW devices illustrates the potential of LiNbO
3
/SiO
2
/Si functional substrates for RF signal processing and cross-domain applications.