A fully-packaged silicon micromachined piezoresistive accelerometer

The design and development of a second-generation miniature piezoresistive micromachined accelerometer are presented. Bulk micromachining etching techniques were utilized in the fabrication of the single-crystalline silicon device. The sensor is essentially its own package, consisting of three carefully aligned ⟨100⟩ silicon wafers. A dozen photomasks were required for the design and fabrication of the complete packaged device. Improvements of this version of the microsensor over the first generation device include the following: wafer level silicon-silicon bonding and alignment, integral squeeze-film air damping, built-in overrange protection, corner compensation, stress relief, low-G performance, light weight (20 mg), small die size (140×140 mils), digital offset nulling bridge, and on-board circuitry for a companion VLSI signal conditioning IC