Differential capacitive pressure sensor design based on standard CMOS

Abstract

A microelectromechanical system capacitive pressure sensor with a differential configuration (patent pending), including a reference and sensitive capacitor, is presented. A single cavity includes both reference and sensitive electrodes. This implementation is achieved by a size reduction of the sensitive electrode. A reduction of the 40% on the sensible electrode area represents a decrease in the sensor sensitivity of only 12.5%, and allows the reference capacitor implementation in the area commonly used only for the sensitive capacitor. A tridimensional model of the sensor was simulated using a finite-element solver considering coupled mechanical and electrostatic models. The simulations show that this pressure sensor has a sensitivity of 4.2 fF/bar. The proposed pressure sensor designs use only materials available in complementary metal oxide silicon (CMOS) standard processes. A CMOS compatible post-process, based on the sacrificial material technique and its restrictions is presented.