Design and Simulation of a MEMS Capacitive Pressure Sensor With Corrugated Membrane and Linear Capacitance-Pressure Response

Abstract

This paper presents a new design for MEMS capacitive pressure sensor that helps to linearize the capacitance-pressures response of the sensor. Capacitive pressure sensors have two electrodes, one often fixed and one is deformed as the ambient pressure changes. In general, the two electrodes are made of flat thin films. The proposed sensor design is based on a corrugated membrane, where circular ridges and grooves are made in the membrane altering its deformation as the pressure is applied. The sensor design is analyzed using finite element simulations, and ANSYS coupled-field multiphysics solver is used to model and obtain the response of a conventional and corrugated pressure sensor as the ambient pressure changes. The simulation results show that, as expected, the sensor displays high sensitivity at lower pressure and as the pressure increases and the contact area between the membrane and fixed electrode expands, the sensitivity of the capacitance-pressure (C-P) response decreases for both sensors. However, the sensor with corrugated membrane displays high linearity at lower pressures. The response for proposed design at this pressure range is nearly a perfect line, while the conventional design exhibits nonlinearity that is visually noticeable. To quantitatively evaluate the level of linearity of the C-P responses, a linearity factor as the coefficient of linear correlation between the capacitance and pressure is used. The simulation results show that at low pressure of 0.2–1.0 MPa, the sensor with corrugated membrane has high linearity of 0.999 compared to 0.987 for conventional sensor, where for pressure range 0–1.0 MPa these values are 0.997 and 0.983, respectively. The quantitative comparison of the linearity factors for the two design show a notable improvement in the linearity of the C-P response providing nearly a constant sensitivity over the pressure range of 0.2 to 1.0 MPa.