Characterisation and modelling of degradation mechanisms in RF MEMS capacitive switches during hold-down operation

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dc.check.embargoformatNot applicableen
dc.check.infoNo embargo requireden
dc.check.opt-outNoen
dc.check.reasonNo embargo requireden
dc.check.typeNo Embargo Required
dc.contributor.advisorDuane, Russellen
dc.contributor.advisorOlszewski, Zbigniewen
dc.contributor.authorRyan, Cormac
dc.contributor.funderScience Foundation Irelanden
dc.contributor.funder
dc.contributor.funderEuropean Space Agencyen
dc.date.accessioned2017-02-16T09:49:36Z
dc.date.available2017-02-16T09:49:36Z
dc.date.issued2016
dc.date.submitted2016
dc.description.abstractRF MEMS switches represent an attractive alternative technology to current mechanical (e.g. coaxial and waveguide) and solid-state (e.g. PIN diode and FET transistor) RF switch technologies. The materials and fabrication techniques used in MEMS manufacture enable mechanically moveable devices with high RF performance to be fabricated on a miniature scale. However, the operation of these devices is affected by several mechanical and electrical reliability concerns which limit device lifetimes and have so far prevented the widespread adoption and commercialisation of RF MEMS. While a significant amount of research and development on RF MEMS reliability has been performed in recent years, the degradation mechanisms responsible for these reliability concerns are still poorly understood. This is due to the multi-physical nature of MEMS switches where multiple mechanical and electrical degradation mechanisms can simultaneously affect device behaviour with no clear way of distinguishing between their individual effects. As such, little progress has been made in proposing solutions to these reliability concerns. While some RF MEMS switches have recently been commercialised, their success has come at the expense of decreased performance due to design changes necessarily imposed to prevent device failure. However, more high performance switches could be developed if the mechanisms responsible for reliability problems could be understood and solved. The work of this thesis is focussed on the isolation and study of individual reliability mechanisms in RF MEMS capacitive switches. A bipolar hold-down technique is used to minimise the effects of dielectric charging and allow mechanical degradation to be studied in isolation in aluminium-based capacitive switches. An investigation of mechanical degradation leads to the identification of grain boundary sliding as the physical process responsible for the decreased mechanical performance of a switch. An alternative material for the switch movable electrode is investigated and shown to be mechanically robust. The effects of dielectric charging are isolated from mechanical degradation using mechanically robust switches. The isolated investigation of dielectric charging leads to the identification of two major charging mechanisms which take place at the bulk and surface of the dielectric, respectively. The exchange of charge from interface traps is identified as the physical mechanism responsible for bulk dielectric charging. An investigation of surface dielectric charging reveals how this reliability concern depends on the structure and design of a switch. Finally, electrical and material means of minimising dielectric charging are investigated. The findings and results presented in this thesis represent a significant contribution to the state-of the- art understanding of RF MEMS capacitive switch reliability. By implementing the design changes and material solutions proposed in this work, the performance and lifetime of RF MEMS capacitive switches can be greatly improved.en
dc.description.sponsorshipScience Foundation Ireland (SFI Grant 10/RFP/ECE2883)en
dc.description.statusNot peer revieweden
dc.description.versionAccepted Version
dc.format.mimetypeapplication/pdfen
dc.identifier.citationRyan, C. 2016. Characterisation and modelling of degradation mechanisms in RF MEMS capacitive switches during hold-down operation. PhD Thesis, University College Cork.en
dc.identifier.endpage170en
dc.identifier.urihttps://hdl.handle.net/10468/3644
dc.language.isoenen
dc.publisherUniversity College Corken
dc.rights© 2016, Cormac Ryan.en
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/3.0/en
dc.subjectRF MEMSen
dc.subjectReliabilityen
dc.subjectViscoelasticityen
dc.subjectViscoplasticityen
dc.subjectCreepen
dc.subjectAluminiumen
dc.subjectTitaniumen
dc.subjectSILCen
dc.subjectTrappingen
dc.subjectDetrappingen
dc.subjectSymmetricen
dc.subjectAmphotericen
dc.subjectCapacitive switchesen
dc.subjectMechanical degradationen
dc.subjectDielectric chargingen
dc.subjectBulk chargingen
dc.subjectSurface chargingen
dc.subjectSilicon dioxideen
dc.subjectStress-induced leakage currenten
dc.subjectBorder trapsen
dc.subjectInterface statesen
dc.subjectC-V shiften
dc.subjectC-V narrowingen
dc.thesis.opt-outfalse
dc.titleCharacterisation and modelling of degradation mechanisms in RF MEMS capacitive switches during hold-down operationen
dc.typeDoctoral thesisen
dc.type.qualificationlevelDoctoral Degree (Structured)en
dc.type.qualificationnamePhD (Science)en
ucc.workflow.supervisorzbigniew.olszewski@ucc.ie
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