Interferometry of actuated microcantilevers to determine materialproperties and test structure nonidealities in MEMS
Jensen, B.D.
de Boer, M.P.
Masters, N.D.
Bitsie, F.
LaVan, D.A.
Dept. of Mech. Eng., Michigan Univ., Ann Arbor, MI ;
This paper appears in: Microelectromechanical Systems, Journal of
Publication Date: Sep 2001
Volume: 10,
Issue: 3
On page(s): 336-346
ISSN: 1057-7157
References Cited: 35
CODEN: JMIYET
INSPEC Accession Number: 7053927
Digital Object Identifier: 10.1109/84.946779
Current Version Published: 2002-08-07
Abstract
By integrating interferometric deflection data from
electrostatically actuated microcantilevers with a numerical finite
difference model, we have developed a step-by-step procedure to
determine values of Young's modulus while simultaneously quantifying
nonidealities. The central concept in the methodology is that
nonidealities affect the long-range deflections of the beams, which can
be determined to near nanometer accuracy. Beam take-off angle, curvature
and support post compliance are systematically determined. Young's
modulus is then the only unknown parameter, and is directly found. We
find an average value of Young's modulus for polycrystalline silicon of
164.3 GPa and a standard deviation of 3.2 GPa (±2%), reflecting
data from three different support post designs. Systematic errors were
assessed and may alter the average value by ±5%. An independent
estimate from grain orientation measurements yielded 163.4-164.4 GPa
(the Voigt and Reuss bounds), in agreement with the step-by-step
procedure. Other features of the test procedure include that it is
rapid, nondestructive, verifiable and requires only a small area on the
test chip
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