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Bottom-up Modeling of the Elastic Properties of Organosilicate Glasses and their Relation to Composition and Network Defects

Published online by Cambridge University Press:  24 March 2011

Jan M. Knaup*
Affiliation:
Department of Physics, Harvard University, Cambridge MA 02138, USA Institute of Materials Science, Ecole polytechnique fédérale de Lausanne, CH-1015 Lausanne, Switzerland
Han Li
Affiliation:
School of Engineering and Applied Sciences, Harvard University. Cambridge MA 02138, USA
Joost J. Vlassak
Affiliation:
School of Engineering and Applied Sciences, Harvard University. Cambridge MA 02138, USA
Efthimios Kaxiras
Affiliation:
Department of Physics, Harvard University, Cambridge MA 02138, USA Institute of Materials Science, Ecole polytechnique fédérale de Lausanne, CH-1015 Lausanne, Switzerland School of Engineering and Applied Sciences, Harvard University. Cambridge MA 02138, USA
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Abstract

Organosilicate glasses (OSG), also known as SiCOH or carbon-doped oxide are used as low-k inter-metal dielectrics for integrated circuits. The material must fulfill two conflicting requirements: It has to have low density to reduce the dielectric constant and be mechanically stable enough to withstand mechanical stress during subsequent production steps. Experimental advances in improving their mechanical and electrical properties have not yet been theoretically examined at the ab initio level, due to the relatively large model sizes necessary for amorphous materials. We employ the density-functional based tight-binding (DFTB) method to achieve an accurate description of OSG properties at different compositions. We analyze the influence of composition and topological defects on the density and bulk modulus of non-porous OSG. We find that the dependence of density and stiffness on chemical composition is of different nature. This difference is traced to a transition between different mechanisms of elastic deformation in silica glass and in silicon hydrocarbide, which is also the reason for different sensitivity to topological defects in the two materials.

Type
Research Article
Copyright
Copyright © Materials Research Society 2011

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Footnotes

now at IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598, USA

References

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