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.
Microelectromechanical Systems, Journal of
Volume 10, Issue 3, Sep 2001 Page(s):336 - 346
Digital Object Identifier 10.1109/84.946779
Summary: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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