Quality factor in trench-refilled polysilicon beam resonators

In this paper, thermoelastic damping (TED) in trench-refilled (TR) polysilicon microelectromechanical beam resonators is studied as a mechanism for limiting quality factor (Q) at low frequencies. An approximate model based on Zener´s theory is developed and verified by numerical simulations in FEMLAB. According to the proposed model a double-dip characteristic is expected for the quality factor versus frequency curve of TR beam resonators. To verify the model experimentally, equal-width TR micro-resonators are fabricated in different length to cover a broad range of frequencies. Frequency response of these devices agrees well with our model. By using the theoretical and numerical models developed in this paper, an upper bound for the quality factor in TR beam resonators or any similar structure such as TR polysilicon gyros can be predicted.