A Laterally Vibrating Lithium Niobate MEMS Resonator Array Operating at 500 °C in Air

• Published in: Sensors (Basel, Switzerland) Vol. 21; no. 1; p. 149
• Main Authors: Eisner, Savannah R., Chapin, Cailin A., Lu, Ruochen, Yang, Yansong, Gong, Songbin, Senesky, Debbie G.
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 29.12.2020; MDPI
• Subjects: Acoustics; high-temperature; Letter; lithium niobate; Microelectromechanical systems; piezoelectric resonators; RF MEMS; Sensors; SH0 mode; Signal processing; Thin films; United States > US; SH0 mode; lithium niobate; RF MEMS; piezoelectric resonators; high-temperature
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s21010149

This paper reports the high-temperature characteristics of a laterally vibrating piezoelectric lithium niobate (LiNbO3; LN) MEMS resonator array up to 500 °C in air. After a high-temperature burn-in treatment, device quality factor (Q) was enhanced to 508 and the resonance shifted to a lower frequency and remained stable up to 500 °C. During subsequent in situ high-temperature testing, the resonant frequencies of two coupled shear horizontal (SH0) modes in the array were 87.36 MHz and 87.21 MHz at 25 °C and 84.56 MHz and 84.39 MHz at 500 °C, correspondingly, representing a −3% shift in frequency over the temperature range. Upon cooling to room temperature, the resonant frequency returned to 87.36 MHz, demonstrating the recoverability of device performance. The first- and second-order temperature coefficient of frequency (TCF) were found to be −95.27 ppm/°C and 57.5 ppb/°C2 for resonant mode A, and −95.43 ppm/°C and 55.8 ppb/°C2 for resonant mode B, respectively. The temperature-dependent quality factor and electromechanical coupling coefficient (kt2) were extracted and are reported. Device Q decreased to 334 and total kt2 increased to 12.40% after high-temperature exposure. This work supports the use of piezoelectric LN as a material platform for harsh environment radio-frequency (RF) resonant sensors (e.g., temperature and infrared) incorporated with high coupling acoustic readout.