A MONOLITHIC CMOS-MEMS 3-AXIS ACCELEROMETER WITH A LOW-POWER, LOW-NOISE DUAL-CHOPPER AMPLIFIER

Abstract

This paper reports the process development, interface circuit design and device characterization of a monolithically integrated 3-axis capacitive accelerometer with a single proof mass.An improved DRIE post-CMOS MEMS process has been developed, which provides robust single-crystal silicon structures in all three axes and greatly reduces undercut of comb fingers in dry release.A low-noise, low-power, dual-chopper amplifier is designed for each axis, which consumes only 1 mW power.With a 40dB onchip amplification, the measured sensitivities of the lateral-and zaxis accelerometers are 560 mV/g and 320 mV/g, respectively, which can be decreased by simply decreasing the amplitude of the modulation signal.The over-all noise floors of the lateral-and zaxis are 12 g/ Hz and 110 g/ Hz, respectively when tested around 200 Hz.