ACTIVE BOOST IN THE QUALITY FACTOR OF AN ALN MEMS RESONATOR UP TO 165,000

This work reports a method to boost the quality factor (Q, defined as the ratio of the resonant frequency to the 3-dB bandwidth) of a 55 MHz AlN MEMS contour-mode resonator (CMR) from similar to 1.000 to >165,000. The resulting resonator exhibits an f-Q product of 8.8x10(12) comparable to quartz crystals (similar to 3x10(13) Hz). This significant. progress is accomplished by pumping energy into the resonator through an externally applied force that has a specific phase relationship with respect to the driving voltage source. This method overcomes the fundamental limit of AlN f-Q product using a finite amount of external power. We further validated this concept and showed more than 12 dB improvement in phase noise of an oscillator built using the Q-boosted resonator. Comparing with other active Q-boosting methods, this technique has the advantage that it intrinsically avoids self-oscillations. We demonstrated an interesting approach to improve the performance of AlN CMRs for timing applications.