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Microstructural Mechanism of Electromigration Failure In Narrow Interconnects

Published online by Cambridge University Press:  21 February 2011

Choongun Kim
Affiliation:
Center for Advanced Materials, Lawrence Berkeley Laboratory and Department of Materials Science, University of California, Berkeley
S. I. Selister
Affiliation:
Center for Advanced Materials, Lawrence Berkeley Laboratory and Department of Materials Science, University of California, Berkeley
J. W. Morris Jr.
Affiliation:
Center for Advanced Materials, Lawrence Berkeley Laboratory and Department of Materials Science, University of California, Berkeley
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Abstract

Microstructural studies of electromigration failure were performed on A1-2Cu-1Si interconnects with 1.3 μm width. The lines were tested to failure under controlled conditions after pre-aging for various times at three different temperatures. Examination of the microstructure of the failure sites suggests that the lines fail at the bamboo grains that terminate the longest polygranular segments in the line. Transgranular slit voids form after Cu has been swept from the grain that fails. Hence, pre-aging lines to create a more stable distribution of Cu lengthens the time required to sweep Cu and significantly increases the time to failure. The optimal microstructure has a maximum intragranular density of stable θ precipitates. In this case transgranular slit failure is suppressed, and the bamboo grain fails by diffuse thinning to rupture.

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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