高阻硅上RF-MEMS共面波导设计及测量研究

Design and measurement of RF-MEMS CPW on HRS

设计并实现了基于高阻硅RF MEMS(射频微机电系统)共面波导传输线(CWP), 并测量和分析了不同偏压下的特征阻抗值。利用部分电容法和保角变换法得到的分析公式确定了特征阻抗为50Ω的共面波导的几何结构尺寸,采用MEMS准平面加工工艺在高阻硅衬底上实现了2.5μm厚的金共面波导结构。在施加不同直流偏压的情况下对所设计的共面波导进行了S参数测量。计算了Winkel多项式中所有系数的具体表达式,运用该多项式获得了共面波导的特征阻抗,并与传统的特征阻抗提取方法进行了结果比较。实验数据表明,在中心信号线上施加的直流偏压对S参数的影响很小,而对共面波导特征阻抗的影响较为明显,当施加的直流偏压从0 V变为38 V时,特征阻抗的实部会增加,变化幅度小于1.2Ω,虚部会减小,变化幅度小于0.8Ω。

This paper presents the design of RF-MEMS(radio-frequency micro-electro-mechanical system) coplanar-waveguide (CPW) on high resistivity silicon (HRS) and its measurement under different bias-voltage are presented. The dimension of the CPW is designed with partial-capacitance method and conformal mapping method. The designed CPW transmission line is realized on 3 inches HRS wafer with a resistivity of 1000 Ω&middotcm. The substrate and metal layer are insulated by 0.8 μm silicon dioxide layer formed by oxygenation. 2.5 μm thick electroplated gold is selected as the material of metal layer. The width of the central signal line is 196 μm and the gap between signal line and ground line is 120 μm. The S-parameters measurement of the designed CPW is performed with 0 V and 38 V bias on the central signal line by HP 8722ES network analyzer. The characteristic impedance of designed CPW is extracted using Winkel's method, and the necessary specific polynomial is also given. The extracted parameters show that the influence of bias-voltage on characteristic impedance is observable. When the bias-voltage on central signal line is transformed from 0 V to 38 V, the change of the real part of the characteristic impedance is about 1.2 Ω, while the image part change is about 0.8 Ω.