A piezoresistive CMOS-MEMS resonator with high Q and low TCf

A high-frequency CMOS-MEMS bulk-mode resonator via a differentially piezoresistive transduction was proposed in this work, demonstrating quality factor (Q) greater than 15,000, temperature coefficient of frequency (TC
_f
) around -12.5ppm/°C, and operating power lower than 400μW, all in a single device. To attain the highest Q among reported CMOS-MEMS resonators to date, a dog-bone design was adopted with its two oxide-rich longitudinally vibrating beams which consist of only low-loss materials (i.e., poly-Si and SiO
₂
) from a standard 0.35μm 2-poly-4-metal (2P4M) CMOS technology. To achieve such decent temperature stability, a constant-resistance control approach was implemented to enable an ovenized element where the poly-Si heater and thermometer are both embedded inside the resonator structure, hence providing excellent thermal isolation, localized heating capability, and on-site/real-time temperature measurement.