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The Electromigration and Failure Behaviour in Layered Tungsten Via Structures

Published online by Cambridge University Press:  15 February 2011

L.J. Elliott
Affiliation:
Digital Equipment Corporation, 77 Reed Rd., Hudson, MA. 01749
T. Spooner
Affiliation:
Digital Equipment Corporation, 77 Reed Rd., Hudson, MA. 01749
J.H. Rose
Affiliation:
Digital Equipment Corporation, 77 Reed Rd., Hudson, MA. 01749
R. Shuman
Affiliation:
Digital Equipment Corporation, 77 Reed Rd., Hudson, MA. 01749
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Abstract

This work investigated the electromigration and failure behaviour of layered tungsten vias. It has long been recognized that the flux divergence caused by the tungsten-aluminum interface is an area of high reliability risk. In an attempt to lower this risk, several process experiments were initiated. The thickness (500Å, 800Å, and 1200Å), composition (TiN and Ti), and etch and rinse rates of the underlaying layers of the tungsten plugs were varied. Test structures consisting of a chain of eight M1 to M2 vias were placed on electromigration testing. Their variability in lifetimes, resistance vs. time characteristics and failure behaviour is reported. The fail sites were characterized using TEM analysis and FIB cross-sections. Based on these results process improvements for improved reliability were developed.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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References

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