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

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dc.contributor.advisor Duane, Russell en
dc.contributor.advisor Olszewski, Zbigniew en
dc.contributor.author Ryan, Cormac
dc.date.accessioned 2017-02-16T09:49:36Z
dc.date.available 2017-02-16T09:49:36Z
dc.date.issued 2016
dc.date.submitted 2016
dc.identifier.citation Ryan, 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.endpage 170 en
dc.identifier.uri http://hdl.handle.net/10468/3644
dc.description.abstract RF 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.sponsorship Science Foundation Ireland (SFI Grant 10/RFP/ECE2883) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2016, Cormac Ryan. en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/ en
dc.subject RF MEMS en
dc.subject Reliability en
dc.subject Viscoelasticity en
dc.subject Viscoplasticity en
dc.subject Creep en
dc.subject Aluminium en
dc.subject Titanium en
dc.subject SILC en
dc.subject Trapping en
dc.subject Detrapping en
dc.subject Symmetric en
dc.subject Amphoteric en
dc.subject Capacitive switches en
dc.subject Mechanical degradation en
dc.subject Dielectric charging en
dc.subject Bulk charging en
dc.subject Surface charging en
dc.subject Silicon dioxide en
dc.subject Stress-induced leakage current en
dc.subject Border traps en
dc.subject Interface states en
dc.subject C-V shift en
dc.subject C-V narrowing en
dc.title Characterisation and modelling of degradation mechanisms in RF MEMS capacitive switches during hold-down operation en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral Degree (Structured) en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text available en
dc.check.info No embargo required en
dc.description.version Accepted Version
dc.contributor.funder Science Foundation Ireland en
dc.contributor.funder
dc.contributor.funder European Space Agency en
dc.description.status Not peer reviewed en
dc.internal.school Tyndall National Institute en
dc.check.type No Embargo Required
dc.check.reason No embargo required en
dc.check.opt-out No en
dc.thesis.opt-out false
dc.check.embargoformat Not applicable en
ucc.workflow.supervisor zbigniew.olszewski@ucc.ie
dc.internal.conferring Spring 2017 en


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