Electromechanical Modelling and Analysis of RF MEMS Switch for mm-wave Application

This paper presents the design, simulation, and analysis of two fundamental configurations aimed at implementing capacitive MEMS switches in a shunt arrangement. The objective of this systematic electromechanical modeling approach is to create MEMS switches with a low actuation voltage while preserving their RF and dynamic performance, especially for mmwave applications. The switch's dynamic performance was analyzed utilizing COMSOL Multiphysics software, while the radio frequency (RF) properties were acquired through the employment of the HFSS software. The structure of Design 1, without flexure, results in a spring constant of 1.57 N/m and a resonant frequency of 54 kHz. Conversely, Design 2, incorporating a Fixed-Fixed flexure, demonstrates a spring constant of 0.80 N/m and a resonant frequency of 38 kHz, accomplished through meticulous adjustment of the thickness-to-length ratio. Both designs employ Aluminium as the material for the beam, with specifications of 260 μm for length, 100 μm for breadth, and 0.5 μm for thickness. Taking into account the influence of squeeze film, a finalized gap of 1.9 μm between the upper electrode and dielectric layer leads to a pull-in voltage of 7 V for Design 1 and 4.4 V for Design 2, respectively. A thorough investigation of incorporating 60 holes, each measuring 64 μm² (8µm x 8µm), in the beam membrane of Design 2 has been conducted. The inclusion of these holes reduces the pull-in voltage to 4 V and the switching time to 28 μs. Additionally, it effectively mitigates most of the stress experienced by the structure. Finally, the addition of a dielectric layer measuring 0.1 μm, utilizing Si3N4 as the dielectric material, further justifies the optimized structure of Design 2 as suitable for operating throughout the frequency range of 15 to 40 GHz.