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Strength-porosity relationship of nanoporous MSSQ films characterised by Brillouin Light Scattering and Surface Acoustic Wave Spectroscopy

Published online by Cambridge University Press:  01 February 2011

C.M. Flannery
Affiliation:
Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin, Germany currently at National Institute of Standards & Technology, 325 Broadway, Boulder CO, USA
T. Wittkowski
Affiliation:
Fachbereich Physik, Universität Kaiserslautern, Erwin Schrödinger Str. 56, D-67663 Germany
K. Jung
Affiliation:
Fachbereich Physik, Universität Kaiserslautern, Erwin Schrödinger Str. 56, D-67663 Germany
B. Hillebrands
Affiliation:
Fachbereich Physik, Universität Kaiserslautern, Erwin Schrödinger Str. 56, D-67663 Germany
M.R. Baklanov
Affiliation:
XPEQT at IMEC, Leuven, B-3001, Belgium
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Abstract

Nanoporous Methylsilsesquioxane films are a leading candidate for low dielectric constant (low-κ) materials for microelectronic interconnect. Mechanical strength reduces rapidly with lower κ (increasing porosity) however, and there is a lack of techniques to characterize these properties in the κ∼2 range. This work reports application of surface acoustic wave spectroscopy and Brillouin light scattering to characterization of density/porosity and Young's modulus values of a range of Methylsilsesquioxane films from different manufacturers. We show that the results are validated by independent measurements and that nanoindentation measurements consistently overestimate stiffness. The behaviour of 3 sets of films show different stiffness-porosity relationships, the initially stiffer materials declining more rapidly with increasing porosity than the softer materials. This has important consequences for stiffness properties in the κ<2 region.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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