Stable Encapsulated Charge-Biased Resonators

Abstract

Bias voltages are typically required for the operation of many capacitive microelectromechanical systems (MEMS) devices. A stored charge can be used in place of a bias voltage supply, granting benefits in terms of power consumption and circuit area. However, charges stored on a device typically tend to leak out over time to the environment, and in this paper, the charge storage capability of resonators fabricated in the epi-seal encapsulation platform is evaluated. Charges were introduced on the resonators using a mechanical switch located within the epi-seal cavity, and no leakage was observed over a year at room temperature. At higher temperatures, the leakage follows an Arrhenius relationship with an activation energy of 1.87 eV, with the leakage pathway believed to be through the buried silicon dioxide support. A 3-dB drop in the resonant peak requires a leakage time of approximately two days at 350 °C, indicating extreme charge trapping capabilities at lower temperatures are possible within the epi-seal platform.