A monolithic integration multifunctional MEMS sensor based on cavity SOI wafer

This paper reports a monolithic integration multi-functional MEMS sensor for acceleration and pressure measurement based on cavity SOI wafer. The piezoresistive sensor uses a beam-block-membrane structure which is not only sensitive to acceleration, but also can be used as a gauge pressure transducer to detect low pressure. A miniature absolute pressure sensor is embedded to the accelerometer's mass block without increasing in chip area. This gapless sensor is designed for dust environment. The fabrication process allows thin membrane design to achieve high sensitivity in small chip size. The measure range of the accelerometer can be adjusted by controlling etching depth in manufacturing process after layout design and CMOS process. A 100g measurement range accelerometer which can be used as a 5kPa gauge pressure transducer and an 180μm×180μm 500kPa absolute pressure sensor are integrated in a 1.7mm×1.7mm die for tire pressure monitoring system and fabricated in 6 inch production line. The actual device shows the sensitivity of 0.164mV/g/V to acceleration and 0.0524mV/kPa/V to absolute pressure in 3.3V supply voltage.