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Fracture Toughness of Silicon and Thin Film Micro-structures by Wedge Indentation

Published online by Cambridge University Press:  15 February 2011

M.P. de Boer
Affiliation:
Dept of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455
He Huang
Affiliation:
Dept of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455
J.C. Nelson
Affiliation:
Dept of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455
Z.P. Jiang
Affiliation:
Dept of Electrical Engineering, University of Minnesota, Minneapolis, MN 55455
W.W. Gerberich
Affiliation:
Dept of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455
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Abstract

Silicon rooftop structures 30 µm high and of 1 µm linewidth were fabricated in a microelectronics facility using anistropic KOH etching. Aluminum-1% silicon was sputter-deposited to investigate the effects of a ductile thin film on the fracture toughness of a brittle material. The rooftop structures were indented by a Knoop indenter purposely placed off-center so that the indenter was wedge-shaped. Deformation and cracks were photographed by SEM. Crack threshold load per unit width are reported for normal cracks, running perpendicular to the roofline. Fracture toughness is calculated by first order approximation and finite element modeling using SEM measurements of the length of normal cracks. Without a thin film, values for silicon are in reasonable agreement with the literature. With a thin film of only 600 Å, fracture toughness is increased by 45%. Cracks nearly parallel to the roofline also appeared at higher load values. Characteristics of both types of cracks are discussed.

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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References

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