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A simple linear electromechanical model for an electrostatically driven resonating cantilever is derived. The model has been developed in order to determine dynamic quantities such as the capacitive current flowing through the cantilever-driver system at the resonance frequency, and it allows us to calculate static magnitudes such as position and voltage of collapse or the voltage versus deflection characteristic. The model is used to demonstrate the theoretical sensitivity on the attogram scale of a mass sensor based on a nanometre-scale cantilever, and to analyse the effect of an extra feedback loop in the control circuit to increase the Q factor.

This letter presents the design, fabrication, and demonstration of a CMOS-MEMS filter based on two high-Q submicrometer-scale clamped-clamped beam resonators with resonance frequency around 22 MHz. The MEMS resonators are fabricated with a 0.35-μm CMOS process and monolithically integrated with an on-chip differential amplifier. The CMOS-MEMS resonator shows high-quality factors of 227 in air conditions and 4400 in a vacuum for a bias voltage of 5 V. In air conditions, the CMOS-MEMS parallel filter presents a programmable bandwidth from 100 to 200 kHz with a < 1-dB ripple. In a vacuum, the filter presents a stop-band attenuation of 37 dB and a shape factor as low as 2.5 for a CMOS-compatible bias voltage of 5 V, demonstrating competitive performance compared with the state of the art of not fully integrated MEMS filters. Index Terms-Bandpass filter, CMOS-MEMS, micromechanical filter, system-on-chip.

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The nanometer-scale oxidation of Si(lQ0) surfaces in air is performed with an atomic force microscope working in tapping mode. Applying a positive voltage to the sample with respect to the tip, two kinds of modifications are induced on the sample: grown silicon oxide mounds less than 5 nm high and mounds higher than 10 run (which are assumed to be gold depositions). The threshold voltage necessary to produce the modification is studied as a function of the average tip-to-sample distance. Q 1995 American Institute of Ph.ysics.