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Elastodynamic Characterization of Imprinted Nanolines

Published online by Cambridge University Press:  01 February 2011

Ward L. Johnson
Affiliation:
wjohnson@boulder.nist.gov, National Institute of Standards and Technology, Materials Reliability Division, 325 Broadway, MS 853, Boulder, CO, 80305, United States, 303-497-5805, 303-497-5030
Colm M. Flannery
Affiliation:
flannery@boulder.nist.gov, National Institute of Standards and Technology, Materials Reliability Division, Boulder, CO, 80305, United States
Sudook A. Kim
Affiliation:
sak430@boulder.nist.gov, National Institute of Standards and Technology, Materials Reliability Division, Boulder, CO, 80305, United States
Roy Geiss
Affiliation:
Geiss@boulder.nist.gov, National Institute of Standards and Technology, Materials Reliability Division, Boulder, CO, 80305, United States
Paul R. Heyliger
Affiliation:
prh@engr.colostate.edu, Colorado State University, Department of Civil Engineering, Fort Collins, CO, 80523, United States
Chris L. Soles
Affiliation:
csoles@nist.gov, National Institute of Standards and Technology, Polymers Division, Gaithersburg, MD, 20899, United States
Walter Hu
Affiliation:
walter.hu@utdallas.edu, University of Michigan, Department of Electrical Engineering and Computer Science, Ann Arbor, MI, 48109, United States
Stella W. Pang
Affiliation:
pang@umich.edu, University of Michigan, Department of Electrical Engineering and Computer Science, Ann Arbor, MI, 48109, United States
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Abstract

The advancement of imprint lithography as a method for fabricating nanostructures is impeded by a lack of effective tools for characterizing mechanical properties and geometry at the nanoscale. In this report, we describe the development of methods for determining elastic moduli and cross sectional dimensions of imprinted nanolines from Brillouin light scattering (BLS) measurements using finite-element (FE) and Farnell-Adler models for the vibrational modes. An array of parallel nanoimprinted lines of polymethyl methacrylate (PMMA) with widths of ∼65 nm and heights of ∼140 nm served as a model specimen. Several acoustic modes were observed with BLS in the low-gigahertz frequency range, and the forms of the vibrational displacements were identified through correlation with calculations using measured bulk-PMMA moduli and density as input. The acoustic modes include several flexural, Rayleigh-like, and Sezawa-like modes. Fitting of Farnell-Adler calculations to the measured dispersion curves was explored as a means of extracting elastic moduli and nanoline dimensions from the data. Some values obtained from this inversion analysis were unrealistic, which suggests that geometric approximations in the model introduce significant systematic errors. In forward calculations, the frequencies determined with the FE method are found to more closely match measured frequencies. This suggests that the FE approach may be more accurate for inversion analysis. Initial estimates of uncertainties in the FE calculations support this conclusion.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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