Surface micromachining: from vision to reality to vision [accelerometer]

Airbag deployment systems demand reliable, inexpensive sensing of deceleration of the car during collision. The integrated accelerometer combines a 0.3 mm/sup 2/ micromechanical capacitive sensing element with precision bipolar/MOS control circuitry in a 9 mm/sup 2/ area. The microstructure is fabricated from a layer of deposited polysilicon by surface micromachining. This chip is an A/V (acceleration-to-voltage) functional block for accelerations of 1 to 50 g. This paper reviews the rationale for surface micromachining the sensing element, the BiMOS2C integrated process, the sense and control circuit architecture, and performance of the chip.