Verification of E-Shaped Double Busbar for Q -Improvement in 42° YX -LT/SiO₂/ α -Si/4H-SiC TF-SAW Resonators

This work systematically investigates the effectiveness of double-busbar electrode designs for enhancing the quality factor ($Q$) of thin-film surface acoustic wave (TF-SAW) resonators. In particular, two configurations—normal double busbar (NDB) and E-shaped double busbar (EDB)—are examined through combined theoretical analysis and experimental validation. The secondary busbar of NDB structure enhances energy confinement along with the aperture, thereby improving$Q$. Building on NDB structure, the EDB structure suppresses scattering losses by the dummy electrode, further improving$Q$. The proposed resonators were fabricated on a$42^{\circ } \textit {YX}$-LiTaO3/SiO2/$\alpha $-Si/4H-SiC heterogeneous substrate. Measured results show that the NDB resonator increases the Bode-${Q}_{\max }$from 1271 to 2439 (92% improvement), compared with the dummy single busbar (DSB) counterpart. The EDB resonator demonstrates a further 27% increase in Bode-${Q}_{\max }$(from 2439 to 3110). Temperature stability was also evaluated, with the EDB resonator exhibiting near-zero temperature coefficient of frequency (TCF) at parallel resonant frequency (+0.16 ppm/°C). These results confirm the strong potential of the proposed structures for low-loss RF front-end modules in next-generation wireless communication systems.