两侧下拉电极MEMS压控电容的分析和优化

Analysis and optimization of a side pull-down electrodes controlled MEMS varactor

基于能量法对两侧下拉电极控制(SPEC)的MEMS(微机电系统)压控电容进行了分析和优化。使用数值迭代方法计算了压控电容可动极板的挠度试解函数,得到了试解函数形状在不同驱动电压下的曲线。计算结果与有限元仿真所得结果一致。在此基础上,给出了基于铝材料的两侧下拉电极MEMS压控电容的优化过程,得到了优化结果。对于初始应力5 MPa,杨式模量70 GPa,极板厚度1.5μm,极板间距1μm,总长度为600μm的铝材料压控电容,控制电极采用70μm的优化长度,可以实现变化比率为2∶1电容变化比率。结果表明采用(SPEC)结构的压控电容,能有效地减小或避免静电微机械结构特有的“崩塌”效应,获得较大的电容调节范围。

The analysis and optimization of a SPEC (Side pull-down electrodes controlled) MEMS (Micro-electro-mechanical system) varactor-with energy method is presented. A two-step iterative calculation is used to generate the trial displacement function under different control voltages. The calculated displacement as a function of control voltage is verified by FEA (Finite element analysis) simulation with good accuracy. Based on the established method, the geometric parameters of SPEC varactors with aluminum as structure materials are optimized. For a SPEC varactor with an initial aluminum membrane stress of 5 MPa, with young module 70 GPa, plate thickness 1.5 μm, gap 1 μm and total length of the suspended plate 600 μm, the optimized length of side controlling electrodes should be 70 μm, which can achieve a tuning rate of 2 : 1. The calculation shows that SPEC MEMS varactor, compared with the conventional two-plate MEMS varactors, can greatly extend the tuning rate of MEMS varactors by reducing or avoiding the pull-in effect.