Nonlinearity Compensation for Mems Pressure Sensors with Piezoresistors at the Neutral Position

This paper reports on a novel nonlinearity compensation method for MEMS piezoresistive pressure sensors by placing additional piezoresistors along the <110> direction at the diaphragm ‘neutral position’. The membrane stress measured by the additional piezoresistors was utilized to compensate for the mechanical nonlinearity due to the balloon effect under a large diaphragm deflection. Prototype sensors were fabricated and characterized. Experiments showed that compared to the uncompensated pressure sensor, the compensated pressure sensor (based on a 1000 μm diameter circular diaphragm of 15 μm thickness) exhibited an increase in sensitivity by a factor of 2.76 and a decrease in nonlinearity by a factor of 7.71, indicating a 21 times improvement in the figure of merit (signal-to-nonlinearity ratio). The influence of membrane thickness on the nonlinearity compensation efficiency was also investigated. The compensation method can be applied to other types of MEMS pressure sensors and offers significant improvements in signal-to-nonlinearity ratio.