A monolithic three-axis silicon capacitive accelerometer with micro-g resolution
A monolithic three-axis silicon capacitive accelerometer utilizing a combined surface and bulk micromachining technology is demonstrated with micro-g resolution. The accelerometer consists of three individual single-axis accelerometers. All three devices have full-wafer thick silicon proof-mass, large area polysilicon sense/drive electrodes, and small sensing gap (<1.5 μm) formed by a sacrificial oxide layer. The fabricated accelerometer system is 7×9 mm2 in size, has >5pF/g measured sensitivity and sub-μg/√Hz mechanical noise floor for all three axes. The total measured noise floor of the accelerometer hybrid assembled with CMOS interface circuit is 1.60 μg/√Hz, 1.08 μg/√Hz for in-plane and out-of-plane devices, respectively.