A novel monolithic CMOS capacitive pressure sensor

This paper reports a novel monolithic capacitive pressure sensor based on the standard CMOS process and post-processing. The sensing part is a variable capacitor with a poly-gate/gate oxide/n-well Si structure. Poly-gate and n-well Si in the CMOS process are the top and bottom electrodes, respectively, while the center layer is the gate oxide. After CMOS process, selectively etching bulk silicon, PN junction self etch-stop and anodic bonding to the glass are used to get the microstructure. Compared with the traditional capacitive pressure sensor, this structure has intrinsic larger initial capacitance value which benefits the following interface circuits and high sensitivity. For the 800um times 800 mum sensor structure, the sensitivity can be 46fF/hPa.Then the sensor is read out using a relaxation oscillator and a D flip-flop with the resolution of 3.2 Hz/hPa