Direct measurement of dissipation in phononic crystal and straight tethers for MEMS resonators

This paper presents optical measurements of the dynamic strain profiles along the tethers of microelectromechanical resonators and relates them to mechanical quality factor (Q). Such measurements allow for the quantification of tether dissipation and fair comparison between various tether designs. Our experiments present the first systematic comparison between the best-performing conventional tethers with one-dimensional phononic crystal (PnC) tethers for silicon bulk acoustic resonators, and demonstrate more than 3× improvement in Q when the PnC tethers are used. The spatial decay rate of the mechanical strain profile along the tethers correlates well with the measured Q. This work is the first to demonstrate one-dimensional PnC tethers for electrostatic bulk acoustic resonators.