MEMS电容型器件边缘效应研究

Research on fringing effect of MEMS capacitive devices

MEMS电容型器件在工作过程中,其电容通常情况下为非正对的极板,边缘效应不容忽视。为解决此问题,基于保角映射变换和复变函数相关理论,通过继承传统模型并加以修正,得出电容极板在非正对情况下的边缘效应模型。经过与有限元仿真、传统Heerens模型、Huang模型的对比,表明当电容极板从正对到完全移开的过程中,本文模型与有限元仿真的误差在10%~20%之间,优于传统Heerens模型与Huang模型。进一步,根据本文模型,当极板重合度低于40%时,边缘效应呈快速增长,此时其电容值可用本文模型进行计算。以上结论均得到了MEMS阵列电容数字式实验验证。研究对电容型MEMS器件的设计与性能分析具参考作用。

In the working process of MEMS capacitive devices,the capacitor plates are usually not in the very opposite position but in an inclined position,which will induce the fringing field effect and cannot be ignored.Based on conformal mapping transformation and complex function correlation theory,the fringing effect model is proposed by inheriting the traditional models and modifying them.Compared with the traditional Heerens’and Huang’s model,the proposed model is better because the error between the proposed model and the finite element simulation,which is from 10%to 20%when the capacitor plate is moved from perfectly aligned to completely misaligned,is less than that between the traditional Heerens’s and Huang’s model.Furthermore,according to the proposed model,when the plate coincidence degree is lower than 40%,the fringing effect increases rapidly.As a result,the proposed model should be applied to correct the capacitance.All above are verified by a digital experiment concerned with MEMS differential capacitor array.The research is helpful for the design and performance analysis of capacitive MEMS devices.