Conceptual Design Optimization of Capacitive Pressure Sensors Via Finite Element Analysis With the Use of Anisotropic Behavior of Silicon ⟨111⟩ Crystal: Summary of Design Optimization Approaches

Abstract

Abstract. In the world of micro-mechanical design of micro-sensors, there has not been much substantial consideration given to the actual mechanical or structural aspect of the designs. Hence, most of the currently available designs are challenged to linearize the “nonlinear” sensor's output by the utilization of electronic circuitry. In this research work, a micro-pressure diaphragm which possesses linear pressure–deflection behavior is designed via the use of finite element method (FEM) optimization techniques. The diaphragm is modeled as a silicon (111) plane, which possesses plane isotropic properties. A circular center boss section is added to the diaphragm, and optimization is carried out to achieve an optimum diaphragm geometry that would allow for flat or rigid deflection of this boss section under the applied surface pressure loadings. In addition, the approximate closed-form deflection solutions are developed using the anisotropic thin plate theory, and the diaphragm deflection behavior of the FEM optimized design is compared with this thin plate theory model. This diaphragm design is proposed to be used as the top electrode plate of a capacitive pressure sensor, where linear pressure–capacitance change behavior would become present. This pressure diaphragm has a pressure range of 0–206,843 Pa (30 psi) with a pressure resolution of 689.5 Pa (0.1 psi). This design conceptualization is a definite preliminary work needed for carrying out a fabrication effort to build this capacitive pressure sensor. Once such a device is fabricated, a comparison of the results between the measurement data from this analysis versus the measurement data from the fabricated device will be published.