Package-friendly piezoresistive pressure sensors with on-chip integrated packaging-stress-suppressed suspension (PS3) technology

An on-chip integrated packaging-stress-suppressed suspension (PS3) technology for a packaging-stress-free pressure sensor is proposed and developed. With a MIS (microholes interetch and sealing) micromachining process implemented only from the front-side of a single-side polished (1 1 1) silicon wafer, a compact cantilever-shaped PS3 is on-chip integrated surrounding a piezoresistive pressure-sensing structure to provide a packaging-process/substrate-friendly method for low-cost but high-performance sensor applications. With the MIS process, the chip size of the PS3-enclosed pressure sensor is as small as 0.8 mm x 0.8 mm. Compared with a normal pressure sensor without PS3 (but with an identical pressure-sensing structure), the proposed pressure sensor has the same sensitivity of 0.046 mV kPa(-1) (3.3 V)(-1). However, without using the thermal compensation technique, a temperature coefficient of offset of only 0.016%. C-1 FS is noted for the sensor with PS3, which is about 15 times better than that for the sensor without PS3. Featuring effective isolation and elimination of the influence from packaging stress, the PS3 technique is promising to be widely used for packaging-friendly mechanical sensors.