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Segregation of Copper in Dilute Aluminum - Copper Alloys for Interconnects

Published online by Cambridge University Press:  22 February 2011

D.A. Smith ,
M.B. Small  and
A.J. Garratt-Reed
D.A. Smith
Affiliation:
IBM Research T.J. Watson Research Center, Yorktown Heights NY 10598 Now at Stevens Institute of Technology, Castle Point on the Hudson, Hoboken, NJ 07030
M.B. Small
Affiliation:
Now consultant at 12 Creighton Lane, Scarborough, NJ 10510
A.J. Garratt-Reed
Affiliation:
Massachusetts Institute of Technology Department of Materials Science & Engineering, 13-1020
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Abstract

It is well known that the resistance to electromigration of aluminum-based interconnects is enhanced by alloying with copper. The mechanism is thought to involve the segregation of copper to the grain boundaries. The copper concentration at grain boundaries has been measured in well annealed alloys, with the compositions A1-0.5wt% Cu and AI-2wt%Cu using a VG HB5 STEM. The grain structure was stabilized by an anneal at 673K for one hour and the grain boundaries were loaded with copper by an anneal for 90 hours at 503K. It was found that the copper concentration varied from boundary to boundary. With the assumption that the copper was concentrated in a single layer the saturation concentration of copper was found to be in the range 0.025 to 0.25. This corresponds to an enhancement of the copper concentration relative to that in the grain interiors by a factor in the range between 3 and 30. The higher value approaches the copper concentration which would correspond to a monolayer of theta phase. Extensive surface segregation, amounting to a monolayer equivalent was also detected.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 338: Symposium – Materials Reliability in Microelectronics IV , 1994 , 313
Copyright
Copyright © Materials Research Society 1994

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References

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