Design and simulation of a high-sensitivity MEMS capacitive pressure sensor

Abstract

A MEMS capacitive pressure sensor is a device used to measure changes in capacitance resulting from pressure-induced deformations in a diaphragm. In this paper, the designed sensor was simulated using Finite Element Analysis (FEA) simulation tools, which began with the visualisation of the layout using Blueprint. Then, by utilising the IntelliFab, the fabrication processes are defined, and subsequently, the 3D model of the sensor is generated in FabSim. The 3D model has gone through the preprocessing steps that included boundary conditions setup, materials properties setting, and loads application on the sensor’s diaphragm. The first MEMS capacitive pressure sensor design uses a square-shaped Si diaphragm with dimensions of 150 µm × 150 µm and a thickness of 1 µm. It is separated by a 2 µm air gap and sandwiched between two Mo electrodes, each 1 µm thick. This design achieves a resonance frequency of 947.702 kHz, with a maximum Z-displacement of 7.88×10–17µm under a static pressure of 20 MPa. At an applied pressure of 1 MPa, the maximum capacitance value reaches 95.89 fF. The overall sensitivity of this design is 31.861 fF/MPa. The second design incorporates 200 µm-long beams attached to the square-shaped Si diaphragm. This configuration achieves a resonance frequency of 13.526 kHz, with a maximum Z–displacement of 0.244 µm under a static pressure of 20 MPa. At an applied pressure of 4 × 10–4 MPa, the maximum capacitance value reaches 1.129 pF. The sensitivity of this design is 2.505 × 106 fF/MPa.