Structure Design and Fabrication of an Area-changed Bulk Micromachined Capacitive Accelerometer

In this paper, a lateral capacitive MEMS accelerometer for low-g applications was designed and fabricated. The accelerometer is chosen to be based on an area-changed detection scheme. Area-changed accelerometers can provide alternatives in designing high sensitivity and low mechanical noise floor sensors as it is capable of providing a large proof mass. Based on the calculation of sensitivity and basic resonance frequency, three kinds of accelerometers were designed and optimized. Bulk silicon is chosen as the proof mass material and a three-mask micromachining technology was adopted to fabricate the active structures of the accelerometer. Deep RIE and wafer bonding techniques are utilized as it offers solutions in fabricating the thick proof mass and high aspect ratio sensing element structures with small sensing gaps to achieve high sensitivity and low noise performance.