Combined differential and relative pressure sensor based on a double-bridge structure

A combined differential and relative MEMS pressure sensor based on a double piezoresistive Wheatstone bridge structure is presented. The developed sensor has a conventional (inner) bridge on a micro machined membrane and a secondary (outer) bridge on the chip substrate. The double-bridge structure has previously been used e.g. in the compensation of temperature-induced errors in MEMS pressure sensors as stated in M. Akbar and M. A. Shanblatt (1992), J. J. Dziuban et al. (1994) and Young-Tae Lee and Hee-Don Seo (1995). An approach is demonstrated for a combined measurement of sensor output from inner and outer bridge, leading to the deduction of both differential and relative media pressure (with respect to atm. pressure), and a significant improvement in differential pressure sensor accuracy. Output from both bridges depends linearly on both differential and absolute media pressure. Furthermore, the sensor stress distributions involved are studied and supported by extensive 3D FEM stress analysis.