High Resolution Single Crystal Silicon Accelerometer Using Silicon Fusion Bonding and Deep Reactive Ion Etching

Abstract

Abstract This paper presents a single crystal silicon accelerometer with high dynamic range fabricated in a CMOS compatible, low cost technology. This technology uses a combination of Silicon Fusion Bonding (SFB) and Deep Reactive Ion Etching (DRIE). which allows thick devices (up to several hundred μm) to be defined with high aspect ratios (up to 25). In addition to the advantages of single crystalline material, the high aspect ratio results in higher sensitivity thus providing significant performance improvement. Prototypes use a hybrid approach, with an 1.0 × 1.5 mm2 accelerometer and a capacitive sensor interface providing closed-loop force-balancing to minimize non-linearity. Characterization tests of a 2 G (1 G = 9.8 m/s2) full scale device have shown a sensitivity of 2.2 V/G. The non-linearity is below the noise level, limited by 1/f noise in the electronics inherent to the foundry CMOS process. At 100 Hz, the measured noise power spectral density is approximately 80 μGrms/√Hz, which is significantly higher than the estimated 6 μGrms/√Hz noise figure for the mechanical element due to Brownian motion.