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

Abstract

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]