A study on flicker frequency noise of piezoelectric aluminum nitride resonators as a function of electrode design

This paper presents experimental studies of flicker frequency (1/f) noise of 1 GHz aluminum nitride (AlN) contour mode resonators (CMR) as a function of electrode design. AlN CMRs with various electrode dimensions and different top electrode materials of Al, Au, and Pt are fabricated to give a wide range of thermoelastic damping (TED), which directly impacts the flicker noise of CMRs. We have measured the flicker noise of a total of 64 devices and the results show that flicker noise decreases with increasing Q, with a power law dependence which ranges from 1/Q^3.2 to 1/Q^3.8. Interestingly, the noise level also depends on the type of electrode materials, where the devices with Pt top electrode demonstrate the best noise performance. Our results indicate that a careful selection of the electrode material and dimensions could further reduce 1/f noise not only in AlN CMRs, but also in various classes of resonators, and thus enable ultra-low noise MEMS resonators for sensing and RF applications.