Thermoelastic damping in trench-refilled polysilicon resonators

This paper presents quality factor measurement results for trench-refilled (TR) polysilicon beam resonators which demonstrate an increase in Q as their resonant frequency increases, a trend opposite to what is expected from solid beams of the same dimensions. This phenomenon is believed to be due to a multi-path thermoelastic damping characteristic. The frequency-dependant behavior of Q/sub TED/ in trench-refilled resonators with voids is analyzed, for which the measurement data is agreeable. A multiphysics FEMLAB simulation was also performed to illustrate the thermal gradients in a resonating TR beam. We show that in a particular frequency range, trench-refilled polysilicon beams can have a higher Q than their silicon counterpart and the thickness of the resonator can be tuned to produce a desired quality factor behavior.