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A One Chip, Polysiiicon, Surface Micromachined Pressure Sensor with Integrated CMOS Signal Conditioning Electronics
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Abstract
In this paper the integration of a polysiiicon, surface micromachined, absolute pressure sensor with analog CMOS (Complementary Metal Oxide Semiconductor) signal conditioning circuitry is a cavity filled with sacrificial oxide. The evacuated cavity under the polysiiicon plate is created by removing the sacrificial oxide and sealed using reactive sealing. The pressure is sensed by a Wheatstone bridge formed from dielectrically isolated polysiiicon piezoresistors deposited on top of the polysiiicon diaphragm [4].
The integrated sensor chip is formed by interweaving a standard CMOS process with the sensor fabrication processes. All of the sensor process steps are compatible with standard CMOS processing A total of 17 mask steps is required for both the sensor and the signal conditioning electronics, including a passivation layer over the CMOS electronics. The sensor and the signal conditioning electronics have been fabricated on a prototype die measuring 2.54 mm on a side. A production die 1.78 mm on a side is in wafer fabrication.
The signal conditioning electronics amplifies and temperature compensates the sensor bridge output. The output of the sensor is ratiometric and can drive a IK Ohm load to within 200 mV of either power supply rail. The chip requires a 5V regulated supply. The temperature compensation reduces the temperature error to less than 2.5% of Vref over a temperature range of −40 to 150 °C. Polysiiicon thin film resistors are laser trimmed to adjust offset and gain of the signal conditioning electronics.
Absolute pressure sensors have been fabricated in pressure ranges from 0-to-450 KPa up to 0-to-17 MPa. Performance data over temperature for various pressure ranges is presented and results of overpressure and pressure cycling tests are shown.
Citation
Mattes, M. and Seefeldt, J., "A One Chip, Polysiiicon, Surface Micromachined Pressure Sensor with Integrated CMOS Signal Conditioning Electronics," SAE Technical Paper 960757, 1996, https://doi.org/10.4271/960757.Also In
References
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