A Fully Integrated Capacitive Pressure Sensor with High Sensitivity

A fully integrated absolute capacitive pressure sensor is presented. The sensing structure consisting of poly Si/gate oxide/n well Si sandwich is a solid-state capacitor, which changes under applied pressure due to the variations of the permittivity of the dielectric, the area and distance between the electrodes. The on-chip interface circuit based on capacitance-frequency conversion is also introduced. The device was fabricated by CMOS process with some post-processing. The typical pressure response of the structure shows the sensitivity is about 43.6 fF/hPa and the nonlinearity is less than 3.3% over the range from 800 hPa to 800 hPa. The resolution of the interface circuit is about 3.2 Hz/hPa.