High-power handling and temperature-stable SH-SAW filters using a 42° YX-LT/SiO₂/α-Si/Si multilayer structure

This paper presents high-performance shear-horizontal surface acoustic wave (SH-SAW) filters on a piezoelectric-on-insulator (POI) platform incorporating lithium tantalate (LiTaO₃) and amorphous silicon (α-Si) thin films. The POI-SAW resonators and filters were designed and fabricated on a 42° YX LiTaO₃/SiO₂/α-Si/Si layered substrate. In this design, the α-Si layer serves to suppress parasitic surface conduction while providing temperature compensation. Thermal annealing was subsequently employed to enhance the Q. Measurement results show a large electromechanical coupling coefficient (k²_eff) of 10.2% and an improved Bode-Q_max of 1375 for the POI-SAW resonator. Furthermore, the ladder π-type filter utilizing the designed resonators exhibits a minimum insertion loss (IL) of 0.53 dB, a 3-dB fractional bandwidth of 5.3% centered at 3.6 GHz, and out-of-band rejection of 35 dB. Notably, the filter also exhibits a high-power handling capability of 36.5 dBm and good temperature stability, with temperature coefficients of frequency (TCF) within ±20 ppm/℃ at both the lower and higher edges of the 3-dB bandwidth and a small TCF variation of only 3.2 ppm/℃. These results confirm the high-performance characteristics of the proposed POI-SAW filter design, showing significant promise for 5G n78 band applications.