Interferometry of actuated microcantilevers to determine material properties and test structure nonidealities in MEMS

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...

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Bibliographic Details
Published in:Journal of microelectromechanical systems 2001-09, Vol.10 (3), p.336-346
Main Authors: Jensen, B.D., de Boer, M.P., Masters, N.D., Bitsie, F., LaVan, D.A.
Format: Article
Language:English
Subjects:
Applied sciences
Beams (structural)
Crystal orientation
Curvature
Deflection
Elastic moduli
Exact sciences and technology
Finite difference method
Fluid dynamics
Fundamental areas of phenomenology (including applications)
Industrial metrology. Testing
Instrumentation for fluid dynamics
Interferometry
Laboratories
Material properties
Materials testing
Mathematical analysis
Mathematical models
Mechanical engineering. Machine design
Mechanical factors
Microelectromechanical systems
Micromechanical devices
Modulus of elasticity
Nondestructive testing
Physics
Polysilicon
Precision engineering, watch making
Silicon
Standard deviation
Statistical methods
Substrates
Thin films
Transistors
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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 (/spl plusmn/2%), reflecting data from three different support post designs. Systematic errors were assessed and may alter the average value by /spl plusmn/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.
ISSN:1057-7157
1941-0158
DOI:10.1109/84.946779