Effects of Contact Roughness and Trapped Free Space on Characteristics of RF-MEMS Capacitive Shunt Switches

Dielectric surface roughness and top electrode metal asperities tend to affect both the lifetime reliability and the frequency response of radio frequency microelectromechanical systems (RF-MEMS) capacitive shunt switches. The downstate (OFF) capacitance of these switches is considerably affected by...

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Bibliographic Details
Published inCanadian journal of electrical and computer engineering Vol. 39; no. 2; pp. 132 - 140
Main Authors Ghaffari Nejad, Ali, Yavand Hasani, Javad
Format Journal Article
LanguageEnglish
Published IEEE Canada 01.03.2016
Subjects
Bypasses
Capacitance
Contact
Contacts
Dielectrics
Electrodes
Exact solutions
Irregularities
Mathematical analysis
Mathematical models
Microswitches
Rough surfaces
Roughness
Surface roughness
Switches
surface irregularities
roughness parameters
self-affine fractals
Radio frequency microelectromechanical systems (RF-MEMS)
shunt switch
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Summary:Dielectric surface roughness and top electrode metal asperities tend to affect both the lifetime reliability and the frequency response of radio frequency microelectromechanical systems (RF-MEMS) capacitive shunt switches. The downstate (OFF) capacitance of these switches is considerably affected by the interface irregularities and the free space trapped between the contacting surfaces of a MEMS switch. Attempts have been made to develop models to describe the effects of interface roughness and the trapped free space, yet no comprehensive model, including closed form analytical equations, still exists. A very large body of research has been conducted in physics to model the types of surface fluctuations and interface irregularities between two contacting media. Among these models, the self-affine fractals can be used to describe different growth and deposition techniques, such as sputtering, thermal evaporation, and molecular bean epitaxy. Based on this concept, in this paper, we developed a model that incorporates the effects of contact roughness and free space into classic equations describing the electromechanical behavior of a capacitive MEMS switch. The resulting closed form equations can properly predict the electrostatic and mechanical characteristics of a typical RF-MEMS switch. Measurement and test results from the reported works are used to confirm the validity of the model.
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ISSN:0840-8688
2694-1783
DOI:10.1109/CJECE.2015.2510700