Abstract
In this paper, we present the design, fabrication, and characterization of CMOS micromachined cantilevers for mass sensing in the femto-gram range. The cantilevers consisting of multiple metal and dielectric layers are fabricated after completion of the conventional CMOS process by dry etching steps. The cantilevers are electrostatically actuated to resonance by in-plane electrodes. The frequency shift due to mass loading is detected capacitively with on-chip circuitry, in which the modulation technique is used to eliminate the capacitive feedthrough from the driving port, and to lessen the effect of the flicker noise. The highest resonant frequency of the cantilevers is measured at 396.6 kHz with a quality factor of 2500. Mass loading on cantilevers is completed by deposition of a 0.1-□m SiO2 layer. The maximum frequency shift after deposition is 140 Hz, averaging 350 fg/Hz.