High Q Lateral-Field-Excited Bulk Resonator Based on Single-Crystal LiTaO3 for 5G Wireless Communication

作者：Xue, Yanmei; Yang, Xiaodong; Zhou, Changjian^*; Zhang, Xiu Yin^*; Chan, Mansun

来源：IEEE Journal of the Electron Devices Society, 2021, 9: 353-358.

DOI：10.1109/JEDS.2021.3066369

• Lateral field excitation
• single-crystal LiTaO3
• shear mode
• longitudinal mode
• 5G wireless communication

The paper presents the design and fabrication of lateral-field-excited (LFE) resonators based on 42 degrees Y-cut single-crystal LiTaO3 (LT) on silicon dioxide (SiO2). A simple coplanar top electrode is defined to excite the bulk acoustic wave modes in the suspended LT/SiO2 structure, and the fabrication process that only involves two lithography steps is more simplified compared to that of commercial film bulk acoustic wave resonators. For a model structure consisting of LT(670 nm)/SiO2 (1500 nm) thin film, two types of acoustic modes are both piezoelectrically active in the LT film: the first one is the thickness-shear mode with a resonance frequency of 2.46 GHz, an electromechanical coupling (k(eff)(2)) of 1.4%, a high quality factor (Q) of 1690, and the second one corresponds to longitudinal mode with a resonance frequency of 4.39 GHz, k(eff)(2) of 1.2%, a high Q of 1590, which is among the highest reported for piezoelectric MEMS resonators operating at this frequency range. The excellent performance would enable application scenarios including high-resolution sensors, low-phase-noise oscillators, and low-loss, high selectivity filters in the sub-6 GHz range for the fifth-generation (5G) wireless communication.