Modeling, design and fabrication of a triple-layered capacitive pressure sensor

A novel triple-layered capacitive pressure sensor (TCPS) is presented. It consists of a polysilicon/nitride/polysilicon composite-membrane sandwich structure, and was fabricated by surface micromachining technology. The operation principle of TCPS is based on the combination of variations of the capacitor area and distance of electrodes with the applied pressure. A load-deflection model for the triple-layered composite-membrane is derived by the improved energy method for the analysis and design optimization of TCPS, which is in good agreement with finite element analysis performed by ANSYS™. Test results show the sensitivity of the device is about 40 fF/Torr (1 Torr = 133.32 Pa = 1 mm Hg) and the nonlinearity is about 0.32%. The pressure sensor described here has a full scale pressure range of 110 kPa. A sensor structure array with 10×10 cells was fabricated and the side length of each cell is 100 μm.