Dielectric charging effects in electrostatically actuated CMOS MEMS resonators

Effects of dielectric charging on resonant frequency in an electrostatically actuated MEMS cantilever are experimentally observed over time and with changing bias voltage. Frequency sensitivity to bias of -11 Hz/V arises from non-linearity in the comb electrostatic force when the device is driven at 200 kHz oscillation. Frequency drift of greater than +200 ppm is observed over a 12 hr period when bias switches by more than 12 V. Borrowing from RF MEMS switch charging models, a device model is applied to the cantilever resonator oscillator system. These initial results inform design and compensation methods leading to decreased frequency drift and improved limit of detection for gravimetric sensing applications.