Segregation of Copper in Dilute Aluminum - Copper Alloys for Interconnects

Autor: David Smith, A.J. Garratt-Reed, M. B. Small
Rok vydání: 1994
Předmět:
Zdroj: MRS Proceedings. 338
ISSN: 1946-4274
0272-9172
DOI: 10.1557/proc-338-313
Popis: 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.
Databáze: OpenAIRE
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