Abstract
In this paper, a piezoresistive pressure sensor based on silicon on insulator (SOI) was presented, which was composed of an SOI layer with sensing elements and a glass cap for a hermetic package. Different from its conventional counterparts, the position and thickness of the four piezoresistors was optimized based on numerical simulation, which suggests that two piezoresistors at the center while the other two at the edge of the pressure-sensitive diaphragm and a thickness of 2 μm can produce the maximum sensitivity and the minimum nonlinearity. Due to the use of silicon rather than metal for electrical connections, the piezoresistive pressure sensor was fabricated in a highly simplified process. From the experimental results, the fabricated piezoresistive pressure sensor demonstrated a high sensitivity of 37.79 mV·V−1·MPa−1, a high full-scale (FS) output of 472.33 mV, a low hysteresis of 0.09% FS, a good repeatability of 0.03% FS and a good accuracy of 0.06% FS at 20 °C. A temperature coefficient of sensitivity of 0.44 mV·MPa−1·°C−1 and a low zero drift were also shown at different temperatures. The piezoresistive pressure sensor developed in this study may function as an enabling tool in pressure measurements.
Highlights
Schematic of sensor the developed piezoresistive sensorwith withsensing optimized positions piezoresistors: (a) The piezoresistive pressure comprises two sections:pressure an silicon on insulators (SOI) wafer elements and aofglass cap for a hermetic piezoresistive pressure sensordeforms comprises two sections: andiaphragms, SOI wafer with sensing elements and a glassand capcorresponding for a hermetic package; (b) outside pressure pressure-sensitive leading to the different stresses package; outside deforms pressure-sensitive diaphragms, leading to the different stresses and corresponding resistance(b) changes ofpressure the piezoresistors
We name ∆σ1 and ∆σ2 as absolute stress difference (ASD), which is proportional to the resistance change of an individual piezoresistor. ∆σR is called the relative stress difference (RSD), which is proportional to the output of the Wheatstone bridge
This study demonstrates the piezoresistive pressure sensor with two piezoresistors positioned at the center while the other two are positioned at the edge of the pressuresensitive diaphragm
Summary
In order to improve the full-scale outputs of the piezoresistive pressure sensor, Chuang Li fabricated a four-grooved diaphragm combined with a roof beam in 2020, which was able to concentrate the stresses and gained a high full-scale output of 154.5 mV with 5 V voltage excitation [19]. This is still not enough in high-precision sensing. The piezoresistive pressure sensor developed in this study may function as an enabling tool in pressure measurements
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