A CMOS-MEMS Capacitive Pressure Sensor with Differential Sensing Electrodes and On-Chip Frequency Output Circuits

This paper presents a CMOS-MEMS capacitive pressure sensor with differential sensing electrodes integrated with a low-power readout circuit in a single chip. The differential sensing electrodes are designed in the back-end-of-line (BEOL) metal and oxide stacks in a commercial
$0.18\mu \mathrm{m}$
1P6M CMOS process. Compared with other pressure sensors with single sensing elements in the literature, the proposed differential sensing design offers the advantages of sensitivity enhancement and noise reduction. The readout circuit is a low power RC oscillator integrated with the sensor on the same chip to reduce noise and power consumption. The sensor was tested in the range of 50-300 kPa. The measurement results show the proposed sensing capacitors have a pressure sensitivity of 0.72 fF/kPa, the frequency of the readout oscillator has a sensitivity of 0.032%/kPa.