An Electrostatic Servo Capacitive Pressure Sensor

We have fabricated an electrostatic servo capacitive pressure sensor by using bulk silicon micromachining and SODIC(SOot-Deposited Integrated Circuit) wafer. The sensor consists of fixed electrodes and two diaphragms which are connected with pillars to move together for electrostatic servo force balancing. It detects pressure by the servo-voltage which is supplied between the lower diaphragm and the fixed electrodes to keep the diaphragm at the initial position. The diaphragm position is detected by the capacitance change between the upper diaphragm and the fixed electrodes. The capacitances versus pressure and the servo-voltage are measured. The results of these measurements show that this sensor can detect the pressure by the servo-voltage and have high sensitivity and wide dynamic range in comparison with the open-loop sensors. The sensor has an advantage that it is not affected by dusts or particles because the capacitor gap is isolated from the external environments.