Vacuum-packaged Resonant Pressure Sensor with Dual Resonators for High Sensitivity and Linearity

This paper presents a vacuum-packaged resonant pressure sensor featured with high sensitivity and linearity using dual resonators. The frequency difference between these two resonators is used to represent pressure, so that the nonlinear responds of each resonator is eliminated and the sensitivity of the sensor is also improved at the same time. The sensitivities of the dual resonators were matched through improved diaphragm uniformity and controlled anchor undercut, which leaded to a better linear performance. With this method, the nonlinear error is reduced from 1.3% F.S. to 0.2% F.S. over the pressure range from 0 to 250 kPa. Furthermore, to achieve better performance, the micro resonators were wafer-level vacuum packaged with anodic bonding to provide the needed low damping environment and the stable reference pressure. Test results show that the pressure in the vacuum-packaged micro chamber of the sensor is less than 5 Pa and kept for 6 months with no drop.