Design And Analysis Of Electrostatic Microrelay With Low Threshold Voltage In MEMS

The threshold voltage of the electrostatic microrelay, as a key parameter, effects its practice application directly, and the threshold voltage of all present electrostatic microrelays are not compatible with the working voltage(5V) of normal electronic circuit. There are two types of driven models of electrostatic microrelay that is vertical driven and lateral driven model, and almost all researches are focused on the vertical-driven model while less in the lateral-driven. In this paper, some typical electrostatic microrelays and their performance parameters are introduced firstly. Then, a novel electrostatic microrelay with parallel-comb driven structure that fabricated by dual polysilicon foundry process is proposed for the first time, and the theory model of threshold voltage is also given. To verify the theory model, we simulated the structure using a coupled electrostatic-mechanical CoSolveEM simulation of Coventor software. It has been approved by theory analyse and simulation result, that the electrostatic microrelay is more suitable for practice application than all previous reports, since its driven voltage is compatible with the working voltage of electronic circuit.This dissertation is supported by the following project: project of 'Basic Research of electrostatic microrelay with low threshold voltage that compatible with CMOS' supported by key project of natural science research of Department of Education of Anhui Province of China (2006KJ026A). The main work and achievement are as follows:1. The character of electrostatic-structural coupled field for a 3-D comb structure was discussed, in order to explore the electrostatic-structural coupled field effect which can be very complicated in the motion of micro comb—drive structure, driven by electrostatic force. The effect of the coupling in the driving forces of the comb structure was simulated and analyzed using finite element method (FEM) .The model of the capacitance of the comb structure is also given.2. we will present a novel electrostatic microrelay with parallel-comb driven structure and its fabrication process. By optimizing the structure of the design, A 5V threshold voltage of the microrelay, depending upon geometrical parameter choices, can be achieved.3. Improving the design of the electrostatic microrelay with lateral contact that fabricated by dual polysilicon foundry process. With multi-level trapezium shaped comb electrostatic driven, a 5V threshold voltage and greater actuating force of several hundredμN which is essential for a reliable microrelay, depending on the geometrical parameter choices of the microrelay, can be achieved.