Temperature compensated MEMS oscillator using structural resistance based temperature sensing

This work presents a micro-ovenized 77.7 MHz silicon MEMS oscillator using resonator's structural resistance as an embedded temperature sensor. The structural resistance of a silicon microresonator exhibits a large temperature coefficient of resistance (TCR) and is used as a sensitive self-temperature sensor to accurately and locally monitor resonator's temperature. A novel cross-sectional Lamé-mode resonator fabricated using the HARPSS™ process with wafer-level hermetic packaging is used as the high-Q frequency reference. A resistance temperature detector (RTD) circuit along with a high gain loop filter are implemented to extract the temperature information and generate a resistance error signal to control the heater amplifier. A micro-oven adjacent to the resonator and on the same die is automatically controlled by the temperature monitoring loop to provide an active temperature compensation for stabilization of the frequency reference. The resonator is interfaced with a sustaining amplifier implemented in TSMC 0.35μm CMOS process, consuming 17mA from a 3V supply.