An in-plane high-sensitivity, low-noise micro-g silicon accelerometer

A high-sensitivity, low-noise in-plane capacitive microaccelerometer utilizing a combined bulk and surface micromachining technology is demonstrated. The accelerometer utilizes a 0.5 mm-thick, 2.4 mm /spl times/ 1.0 mm proof-mass and high aspect-ratio vertical polysilicon sensing electrodes fabricated using a trench refill process. The electrodes are separated from the proof-mass through a 1.1 /spl mu/m sensing gap that is formed using a sacrificial oxide layer. The measured sensitivity of the device is 5.6pF/g and the output noise floor of the accelerometer hybrid assembled with CMOS interface circuit is 1.6pg/4Hz in atmosphere.