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Constraint Effects on Cohesive Failures in Low-k Dielectric Thin Films

Published online by Cambridge University Press:  01 February 2011

Ting Y. Tsui
Affiliation:
Silicon Technology Development, Texas Instruments Inc, Dallas, TX 75246, U.S.A. Division of Engineering and Applied Sciences, Harvard University, Cambridge MA 02138
Andrew J. McKerrow
Affiliation:
Silicon Technology Development, Texas Instruments Inc, Dallas, TX 75246, U.S.A. Division of Engineering and Applied Sciences, Harvard University, Cambridge MA 02138
Joost J. Vlassak
Affiliation:
Silicon Technology Development, Texas Instruments Inc, Dallas, TX 75246, U.S.A. Division of Engineering and Applied Sciences, Harvard University, Cambridge MA 02138
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Abstract

One of the most common forms of cohesive failure observed in brittle thin films subjected to a tensile residual stress is channel cracking, a fracture mode in which through-film cracks propagate in the film. The crack growth rate depends on intrinsic film properties, residual stress, the presence of reactive species in the environment, and the precise film stack. In this paper, we investigate the effect of various buffer layers sandwiched between a brittle carbon-doped-silicate (CDS) film and a silicon substrate on channel cracking of the CDS film. The results show that channel cracking is enhanced if the buffer layer is more compliant than the silicon substrate. Crack velocity increases with increasing buffer layer thickness and decreasing buffer layer stiffness. This is caused by a reduction of the constraint imposed by the substrate on the film and a commensurate increase in energy release rate. The degree of constraint is characterized experimentally as a function of buffer layer thickness and stiffness, and compared to the results of a simple shear lag model that was proposed previously.

Type
Research Article
Copyright
Copyright © Materials Research Society 2005

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