Monolithic-integrated silicon bulk-micromachined accelerometer and pressure-sensor for tire-pressure-monitoring-system (TPMS) application

A single-sided micromachined TPMS sensor is proposed and fabricated for automobiles, which is with a piezoresistive pressure sensor and a cantilever-mass piezoresistive accelerometer monolithically integrated in a 1.6mm×1.5mm sized (111) silicon chip. Single-wafer-based front-side silicon micromachining and metal electroplating technologies are employed to fabricate the device. Specially designed releasing trenches along 〈111〉 orientation are constructed to form the hexagonal pressure-sensitive diaphragm and the post-sealed vacuum reference-cavity. The fabrication of the accelerometer is also based on a hexagonal diaphragm that is latterly cut into suspended cantilevers and seismic-mass. Fabricated with the low-cost front-side micromachining technique, the small-sized TPMS sensors are promising in practical applications and volume production.