Design, Fabrication and Characterization of Novel Piezoresistive Pressure Microsensor for TPMS

Novel piezoresistive microsensors for automotive tire pressure monitoring system (TPMS) are designed, fabricated and tested. 30 mum thick silicon diaphragms (from 370 mum times 370 mum to 970 mum times 970 mum) are adopted, thicker than that of the conventional piezoresistive pressure sensor, which extends the high stress distribution in the bulk silicon. Novel meander shape piezoresistors are designed, parts of which are fabricated on the high stress bulk silicon to obtain high linearity and sensitivity. Different diaphragm areas, piezoresistive shapes and placing methods on the microsensor performances are simulated, measured and analyzed. The whole fabrication is low-cost and compatible with standard IC process, which tolerates large process variations. Good microsensor precision (0.23%/FS) is obtained. The whole work indicates a novel solution of small size, high performance and low cost piezoresistive microsensor for TPMS and many other applications.