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The effect of porogen loading on the stiffness and fracture energy of brittle organosilicates

Published online by Cambridge University Press:  31 January 2011

Han Li ,
Youbo Lin ,
Ting Y. Tsui  and
Joost J. Vlassak
Han Li
Affiliation:
School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
Youbo Lin
Affiliation:
School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
Ting Y. Tsui
Affiliation:
Chemical Engineering Department, University of Waterloo, Nanotechnology Institute, Waterloo, Ontario N2L 3G1, Canada
Joost J. Vlassak*
Affiliation:
School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
*
a) Address all correspondence to this author. e-mail: vlassak@esag.deas.harvard.edu
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Abstract

Integrating porous low-permittivity dielectrics into Cu metallization is one of the strategies to reduce power consumption, signal propagation delays, and crosstalk between interconnects for the next generation of integrated circuits. The porosity and pore structure of these low-k dielectric materials, however, also affect other important material properties in addition to the dielectric constant. In this paper, we investigate the impact of porogen loading on the stiffness and cohesive fracture energy of a series of porous organosilicate glass (OSG) thin films using nanoindentation and the double-cantilever beam (DCB) technique. The OSG films were deposited by plasma-enhanced chemical vapor deposition (PECVD) and had a porosity in the range of 7−45%. We show that the degree of porogen loading during the deposition process changes both the network structure and the porosity of the dielectric, and we resolve the contributions of both effects to the stiffness and fracture energy of the films. The experimental results for stiffness are compared with micromechanical models and finite element calculations. It is demonstrated that the stiffness of the OSG films depends sensitively on their porosity and that considerable improvements in stiffness may be obtained through further optimization of the pore microstructure. The cohesive fracture energy of the films decreases linearly with increasing porosity, consistent with a simple planar through-pore fracture mechanism.

Keywords

Elastic propertiesFracturePorosity
Type
Articles
Information
Journal of Materials Research , Volume 24 , Issue 1 , January 2009 , pp. 107 - 116
Copyright
Copyright © Materials Research Society 2009

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