This paper is the first report of the high-temperature characteristics of a laterally vibrating piezoelectric lithium niobate (LiNbO3) MEMS resonator array up to 500{\deg}C in air. After a high-temperature burn-in treatment, device quality factor (Q) is enhanced to 508 and the resonance shifts to a lower frequency and remains stable up to 500{\deg}C. During subsequent in situ high-temperature testing, the resonant frequencies of two coupled shear horizontal (SH0) modes in the array are 87.36 MHz and 87.21 MHz at 25{\deg}C and 84.56 MHz and 84.39 MHz at 500{\deg}C, correspondingly, representing a -3% shift in frequency over the temperature range. Upon cooling to room temperature, the resonant frequency returns to 87.36 MHz, demonstrating recoverability of device performance. The first- and second-order temperature coefficient of frequency (TCF) are found to be -95.27 ppm/{\deg}C and 57.5 ppb/{\deg}C2 for resonant mode A, and -95.43 ppm/{\deg}C and 55.8 ppb/{\deg}C2 for resonant mode B, respectively. The temperature-dependent quality factor (Q) and electromechanical coupling coefficient (kt2) are extracted and reported. Device Q decreases to 334 after high-temperature exposure, while kt2 increases to 12.40%. This work supports the use of piezoelectric LiNbO3 as a material platform for harsh environment radio-frequency (RF) resonant sensors (e.g. temperature and infrared).
@article{arxiv.1911.10276,
title = {A Laterally Vibrating Lithium Niobate MEMS Resonator Array Operating at 500{\deg}C in Air},
author = {Savannah R. Benbrook and Caitlin A. Chapin and Ruochen Lu and Yansong Yang and Songbin Gong and Debbie G. Senesky},
journal= {arXiv preprint arXiv:1911.10276},
year = {2021}
}