Temperature Compensation of Thermally Actuated, In-Plane Resonant Gas Sensor Using Embedded Oxide-Filled Trenches

• Published in: Journal of microelectromechanical systems Vol. 29; no. 5; pp. 936 - 941
• Main Authors: Schwartz, Steven A., Brand, Oliver, Beardslee, Luke A.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: cantilever gas sensor; Cantilever members; compensated resonator; Finite element method; Frequency stability; Gas detectors; Gas sensors; Material properties; Q factors; Resonant frequency; Resonant gas sensor; Resonators; Silicon; Temperature; Temperature compensation; Temperature dependence; Temperature sensors; thermal compensation; thermally compensated gas sensor; Toluene; Trenches
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2020.3014502

We report the implementation of a passive temperature compensation technique in thermally actuated, silicon-based, resonant cantilever gas sensors vibrating in their fundamental in-plane resonant mode. The temperature compensation technique utilizes oxide-filled trenches along the edges of the cantilever structure and adds a single additional mask to the overall fabrication process. The trench width for effective temperature compensation was optimized using finite element simulation. The fabricated resonators exhibit a temperature coefficient of frequency (TCF) as low as 1.7 ppm/°C, which represents a 15x improvement compared to the same resonators without oxide trenches. Quality factors of devices with oxide compensation are similar to those measured in non-compensated counterparts. The temperature compensation technique addresses a key limitation of silicon-based, mass-sensitive chemical microsensors, namely their temperature instability due to inherent temperature-dependent material properties. Compared to our previous work, the improved frequency and baseline stability yields an almost order-of-magnitude improvement in the extrapolated limit of detection, approaching 100 ppb for toluene. [2020-0154]