A Research On Multilayer MEMS Micro Fabrication Technology Based On Organic Thin Film Substrate

A Frequency selective surface(FSS)is a kind of infinite planar structure arranged by innumerable identical basic unit of structure periodically.As a spatial filter,a FSS can transmit and reflect electromagnetic wave in corresponding frequency band.With such a property,the FSS has a great application prospect in microwave field such as microwave radiometer and radome.The purpose of this paper is to study the simulation design and MEMS fabrication of FSS in the millimetric wave band.To meet the strict requirement of quasi-optical feed network system,the insertion loss and reflection loss of FSS in corresponding band must be low.Meanwhile,the isolation of FSS in rejection band must be higher than an ideal value.Therefore,a multilayer FSS based on organic thin film substrate has been designed and fabricated in this paper.This paper mainly researches the following contents:1)The application of organic thin film materials in the design and fabrication of FSS in electromagnetic field is researched through reviewing corresponding articles,then PET thin films are choosen as substrates.The insertion loss in the millimetric wave band and the compatibility to conduct a MEMS fabrication are two main factors to determine the substrate material from so many organic thin film materials including PI,PMMA,PET and PTFE.2)A 183 GHz/118 GHz FSS based on multilayer metallic microstructure is designed in this part to meet the requirement to be loaded on a geo-stationary orbit satellite.The basic unit structure is determined at first.Then the transmission performance of the FSS under different period,line width,thickness of metal layer,thin film thickness and numbers of FSS layers are analyzed through the CST MWS software.Simulation results demonstrate that the insertion loss at 183 GHz of FSS would be less than 0.3 d B,meanwhile,the reflection loss of FSS at 118 GHz would be less than 0.3 d B when the substrate thickness is 100 ?m and the layers of Cu is 8.Meanwhile,the isolation at 118 GHz would be better than 22 d B.The design requirements of low insertion and reflection loss and high isolation are achieved after a parameter optimization.3)The MEMS micro-fabrication of FSS is studied in this part.In order to make a micro metal structure on the organic thin film substrate,the MEMS processing technology has been improved.As a result,the FSS samples are fabricated successfully.4)The transmission performance of the FSS samples are detected in this part with the help of antenna near field test system.The measurement result shows that the transimission performance of FSS samples is worse than the simulation result slightly.