Stability measurements of silicon MEMS resonant thermometers

The stability of single-anchored Double-Ended Tuning Fork (DETF) resonators fabricated in single-crystal silicon with an epi-seal process was investigated. Using two devices side-by-side, the common-mode noise from ambient temperature fluctuations was eliminated to distinguish the inherent noise of the resonator. With 1 s integration time, the two silicon resonators demonstrate a relative frequency stability of 4.8 ppb (standard deviation) over three weeks, corresponding to a temperature resolution of 0.16 mK.