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Proceedings Paper

Analysis of material properties for MEMS using interferometric measurements
Author(s): Conor O'Mahony; Martin Hill; Alan Mathewson
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Paper Abstract

As the scope and depth of research into microelectromechanical systems increases, the issue of mechanical characterisation has emerged as a major consideration in device design. It is now common to include a set of test structures on a MEMS wafer for extraction of thin film material properties (in particular, residual stress and Young's modulus). These structures usually consist of micromachined beams and strain gauges, and measurement techniques include tensile testing, electromechanical characterisation, SEM imaging, and Raman spectroscopy. However, some of these tests are destructive and difficult to carry out at wafer scale. This work uses electrostatic actuation to pull fixed-fixed beams towards the substrate, and a white-light interferometer to record the beam deflection profile. Finite-element simulation software is employed to model this deflection, and to estimate the material properties which minimise the difference between the measured and simulated profiles. The test is non-destructive, suitable for wafer-level characterisation, and the structures involved require less die space than other methods. We have developed a 1.5mm surface micromachining process for the fabrication of composite and monolayer structures with applications in relay switching, optical imaging and radio-frequency components. This work presents results obtained using interferometric analysis for both monolayer (titanium) and composite (SiOx - metal) thin films fabricated with this process.

Paper Details

Date Published: 27 August 2003
PDF: 11 pages
Proc. SPIE 4876, Opto-Ireland 2002: Optics and Photonics Technologies and Applications, (27 August 2003); doi: 10.1117/12.463655
Show Author Affiliations
Conor O'Mahony, National Microelectronics Research Ctr. (Ireland)
Martin Hill, Cork Institute of Technology (Ireland)
Alan Mathewson, National Microelectronics Research Ctr. (Ireland)

Published in SPIE Proceedings Vol. 4876:
Opto-Ireland 2002: Optics and Photonics Technologies and Applications
Vincent Toal; Norman Douglas McMillan; Gerard M. O'Connor; Eon O'Mongain; Austin F. Duke; John F. Donegan; James A. McLaughlin; Brian D. MacCraith; Werner J. Blau, Editor(s)

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