An experimental investigation on the Q-boosted CMOS-MEMS flexural-mode resonator circuits

This work reports an extraordinary Q-boosting effect in a monolithically integrated CMOS-MEMS flexural-mode resonator circuit. The proposed resonator circuit centered at 960 kHz with a maximum Q of 12,673 is demonstrated for the first time among CMOS-MEMS flexural-mode based resonators (their typical Q ~ 1,500). Under proper biasing conditions while interfaced with on-chip amplifier circuits, the maximum Q of the resonator circuit can be magnified at least 5X as the dc bias voltage (V_P) beyond certain threshold level. Such a Q-booting effect cannot be explained by a traditional drive level-dependent Duffing nonlinearity model [1], and the mechanism behind this phenomenon is still under investigation. With this Q-boosting feature, oscillators implementing these CMOS-MEMS resonator circuits are expected to greatly improve both close-to-carrier (through high Q) and far-from-carrier (through transmission enhancement, i.e., low motional impedance) phase noise performance even using flexure-mode type MEMS resonators.