Design And Process Study Of RF MEMS Cantilever Switch

Radio frequency Micro Electro Mechanical System(RF MEMS)is one of MEMS is an important application field of MEMS technology,and it also becomes a hot spot with the arrival of 5G network in MEMS domain.Compared with traditional PIN and MOSFET solid state switches,RF MEMS switch a lot of the advantages such as: small size,low power consumption,very low insertion loss,high isolation and low cost,so it has a good application prospect in RF front-end components of phased array radar,satellite communication,test instrument and portable wireless communication systems.Combined with the research background and the research status,this paper will select RF MEMS cantilever beam contact switch as the research object based on silicon 4rsubstrate,successively explores the factors of affecting the switch pull-down voltage,proposes two methods to design lower pull-down voltage,and studies the key process parameters of the switch fabrication on the silicon substrate.The main works are as follows:1.Firstly,this paper introduces the mechanical model of RF MEMS switch,the working principle of RF MEMS contact switch and the main mechanical performance indexes.Then,by establishing a simplified model of the contact switch,the formula of the pull-down voltage of the switch is derived.Finally,the switch dynamic response time is studied,the switch time is obtained by using the COMSOL tool,and the switching speed under different bias voltages are compared.2.After that,the electromechanical simulation of RF MEMS contact switch is carried out.Firstly,the influence of switch sizes on pull-down voltage are studied based on the traditional one-line cantilever beam model,and the results are compared with the pull-down voltage value which are calculated by theoretical formula.Then,the influence on the pull-down voltage by changing the cantilever beam structures are studied,according to the thinking of increasing driving area and designing cantilever beam with a low elastic coefficient,on the basis of one-line cantilever beam,the cross,the trident,crab pliers type and fold type four kinds of structure are put forward.Moreover,the four kinds of structure above-mentioned are verified by simulation,the simulation value of pull-down voltage are 7.2V,5.6V,3.8V,3.6V that corresponds to the above-mentioned structure severally(while the pull-down voltage of one-line cantilever is 9.1V),which can indeed achieve lower pull-down voltage.Finally,the design method of lower pull-down voltage and its advantages and disadvantages have a contrastive analysis.3.This paper also focuses on the key process of fabricating the cantilever switch,under the condition of existing equipment in the laboratory,some key technology,such as: thermal oxidation,electron beam evaporation,lithography,PECVD coating,dry etching and the release technique of sacrifice layer are studied respectively,for each step,a large number of comparison experiments are repeated to obtain better experimental parameters,and on the basis of these experimental data,finally a reasonable process flow is developed and makes the switch successfully,test result displays pull-down voltage of the switch is 19.5 V.