A piezoresistive pressure sensor with improved sensitivity in low pressure condition

In this paper, a high sensitive piezoresistive pressure sensor is designed, fabricated and characterized. The designed structure is composed of 4 diagrams separated by two crossed thick beams. There are two piezoresistors located at two ends of the beam, which are used to measure the largest stress in the structure during stressed. Four piezoresistors are connected into a Wheatstone Bridge. The crossed thick beams are covered with a 2μm thick Al layer resulting more residual stress on piezoresistors. This structure has shown improved sensor sensitivity in low pressure condition. The sensor is characterized under the pressure ranges from 5-400hPa. As a reference, a conventional flat membrane pressure sensor is also fabricated. The testing results show that the sensitivity of crossed beam structure is 32.9μV/hPa, which is 3.8 times higher than that of the conventional structure. Finally, the stress simulation results of the crossed beam membrane (CBM) and the conventional flat membrane (CFM) are given to verify the testing results.