A CMOS surface micromachined pressure sensor

A capacitive pressure sensor has been implemented by the industrial standar d 0.8 mu m CMOS (Complementary metal oxide semiconductor) process. The devi ce layout follows the entire set of CMOS IC (Integrated circuit) design rul es. The sensing capacitor of the capacitive pressure sensor is composed of the upper metal (metal 2) and the polysilicon layer. The lower metal layer (metal 1) serves as the sacrificial layer. After completing the standard CM OS process, three CMOS-compatible post-processing steps were applied. First , phosphoric acid was used to etch the sacrificial layer to release the mem brane of the capacitive pressure sensor. Second, PFCVD (Plasma enhanced che mical vapor deposition) nitride was utilized to seal all access holes. Fina lly, RIE (Reaction ion etching) was used to remove nitride on the membrane. The dimensions of the capacitive pressure sensor are 1.0 mm X 0.9 mm. This pressure sensor operates linearly in the range of 0 similar to 200kPa, and the sensitivity is 0.07 mV/kPa.