Electrically Enhanced Readout System for a High-Frequency CMOS-MEMS Resonator

The design of a CMOS clamped-clamped beam resonator along with a full custom integrated differential amplifier, monolithically fabricated with a commercial 0.35 μm CMOS technology, is presented. The implemented amplifier, which minimizes the negative effect of the parasitic capacitance, enhances the electrical MEMS characterization, obtaining a 48×10 8 resonant frequency-quality factor product (Q×fres) in air conditions, which is quite competitive in comparison with existing CMOS-MEMS resonators. DC voltage (VDC) is applied to the suspended structure, while an AC excitation voltage (VAC) is applied to the excitation electrode. The resulting electrostatic force induces the movement of the suspended structure at the excitation frequency. This oscillation generates a change in the capacitance constituted by the readout electrode and the suspended structure that can be quantified by measuring the induced output current: