Abstract
We analyzed experimentally the noise characteristics of fully integrated CMOS-MEMS resonators to determine the overall thermomechanical noise and its impact on the limit of detection at the system level. Measurements from four MEMS resonator geometries designed for ultrasensitive detection operating between 2-MHz and 8-MHz monolithically integrated with a low-noise CMOS capacitive readout circuit were analyzed and used to determine the resolution achieved in terms of displacement and capacitance variation. The CMOS-MEMS system provides unprecedented detection resolution of 11 yF·Hz−1/2 equivalent to a minimum detectable displacement (MDD) of 13 fm·Hz−1/2, enabling noise characterization that is experimentally demonstrated by thermomechanical noise detection and compared to theoretical model values.
Highlights
Micro and nanoelectromechanical resonators have been extensively proposed and experimentally tested for sensing purposes in the biological and chemical domains [1,2], among many others, given their extremely large mass sensitivity [3,4]
The MEMS resonators considered in this work were fabricated using the top metal layer (Aluminum) of a0.35-μm commercial technology followedwet-etching with a mask-less wet-etching of a commercial
The model predictions were experimentally confirmed for all the geometries corroborating The model predictions were experimentally confirmed for all the geometries the noise capabilities of these
Summary
Micro and nanoelectromechanical resonators have been extensively proposed and experimentally tested for sensing purposes in the biological and chemical domains [1,2], among many others, given their extremely large mass sensitivity [3,4] These systems are limited by their intrinsic noise [5], mainly thermomechanical (Vn,res ), that determines the ultimate limit of detection. Plate-B2 in Figure 1a), a CC-Beam structure (Figure 1b) and a Cantilever (Figure 1c) All these resonators were monolithically integrated with a full-custom capacitive readout amplifier (Figure 2), achieving a Vn,amp < 25 nV·Hz−1/2 input referred noise (@6 MHz), using a CMOS-MEMS solution that allows a direct on-chip resonator response measurement. Such a low-noise amplifier scheme allows detecting the resonators thermomechanical motion, allowing the calibration of both the displacement sensitivity (Ds ) and the minimum detectable displacement
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