High-density wide-range digital accelerometer arrays with high detection resolution

This paper presents the implementation and preliminary characterization of a new type of digital accelerometer array with high detection resolution and low noise, enabled by high aspect-ratio (HAR) silicon proof-mass, dense sensor array, precisely-defined air-gaps and small air damping. We fabricated and tested 16-element (4-bit) and 32-element (5-bit) threshold accelerometer arrays (chip area <;1 cm
²
) with evenly-spaced threshold air-gaps from 1-4 μm and incremental air-gaps as small as 100 nm. Vertically anchored springs of different cross-sectional dimensions (10
²
-30μm
²
) are further designed to target specific g-ranges from <; 100 mg to 40 g. The digital accelerometer chips are fabricated using a modified silicon-on-glass (SOG) process which provides tall (1mm) and HAR proof-mass within small footprint (>2.33 milligram/mm
²
), thus increasing the array density and reducing chip area while achieving Brownian noise equivalent acceleration (BNEA) at <;1μg.