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Microstructural Control of Internal Electromigration Failure in Narrow Al-Cu-Si Lines

Published online by Cambridge University Press:  15 February 2011

J.W. Morris Jr.
Affiliation:
Center for Advanced Materials, Lawrence Berkeley Laboratory Department of Materials Science, University of California, Berkeley
C. Kim
Affiliation:
Center for Advanced Materials, Lawrence Berkeley Laboratory Department of Materials Science, University of California, Berkeley
S.H. Kang
Affiliation:
Center for Advanced Materials, Lawrence Berkeley Laboratory Department of Materials Science, University of California, Berkeley
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Abstract

Al-Cu lines of submicron width ordinarily have quasi-bamboo microstructures that contain both bamboo grains and polygranular segments. The usual mechanism of internal electro-migration failure in such lines involves the formation of a transgranular void across a bamboo grain at the upstream end of a long, polygranular segment. The voiding is preceded by the depletion of Cu from both the polygranular segment and the upstream bamboo grain. At least three metallurgical mechanisms are available to inhibit this failure mechanism and improve the useful lifetime of the line. First, the line can be annealed after patterning to break up long polygranular segments. Second, the line can be aged at relatively low temperature to stabilize the distribution of Cu and retard its depletion from polygranular segments. Third, the line can be subjected to reverse currents to restore the distribution of Cu and provide a Cu reservoir. Each of these methods has been demonstrated in the laboratory environment.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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References

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