1024 3D-Stacked Monolithic NEMS Array with 375μm20.5mW 0.28ppm Frequency Deviation Pixel-level Readout for Zeptogram Gravimetric Sensing

NanoElectroMechanical System (NEMS)-based resonator sensors are a promising approach to detect a single molecule deposition with zeptogram mass resolution [1]. However, MEMS sensing areas (on the order of 1
$\mu\mathrm{m}^{2}$
) are several orders of magnitude lower than the mass deposition focus beam (
$\text{mm}^{2}$
-scale), dramatically reducing the probability of detecting molecules, thus increasing the detection time [2]. NEMS and CMOS co-integration has already been considered but the density NEMS arrays limits the detection probability and scalable readout circuits fully suitable to NEMS pixel constraints e.g. size, power consumption, resolution has not been proposed yet. We propose the first realization of a fully 3D-monolithic 1024 zepto-balances (zBal) array including NEMS-based gravimetric sensor [2] and readout circuits individually addressed by on-chip matrix decoder and voltage drivers and controlled by a shared phase-locked loop which scans sequentially two resonant frequencies of each NEMS. We report a zBal readout with 0.5mW power-consumption,
$375\mu\mathrm{m}^{2}$
, silicon footprint and 0.28ppm frequency-resolution variability for a 10ms individual NEMS acquisition time. The 0.7% frequency variability measured on 1024 NEMS arrays allows higher effective sensing area than the previously published active NEMS sensors [3]–[5].