Design and Fabrication of Temperature-Insensitive MEMS Pressure Sensor Utilizing Aluminum-Silicon Hybrid Structures

Abstract

In order to meet the requirements for high sensitivity and low temperature drift of pressure sensors in the field of meteorological detection or tire pressure monitoring system (TPMS), this paper proposes a MEMS chip-level pressure sensor based on two pairs of aluminum-silicon hybrid structures, which are etched on the SOI wafer. The pressure sensor achieves the amplified piezoresistive effect by the micron thick ohmic contact between the boron-doped silicon and external aluminum shunt, as verified by finite element numerical simulation and experiment. Four symmetrical L-shaped raised structures are distributed around the square strained membrane, which enhance the stress of the pair of stress-sensitive aluminum-silicon hybrid structures. The other pair of hybrid structures placed outside the strained membrane of the sensor chip enables differential sensor output which is highly insensitive to temperature. The offset drift of differential output is reduced to −4.39%FS compared with that of single aluminum-silicon hybrid structure. Cooperated with temperature compensation structures, an additional thermodynamic control system by using PID algorithm to keep the working temperature stable can eliminate the temperature drift of sensor output. The feasibility of the thermodynamic control system is verified by steady-state thermal simulation. Experiment test results show that the sensitivity of a single aluminum-silicon hybrid structure can reach 0.283 mV/V/kPa at constant heating temperature of 50 °C, and whose thermal coefficient of offset (TCO) can be reduced from −6.92E-1 to −1.51E-3 %FS/°C in ambient temperature ranges of −20 to 50 °C.