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Thermal Oxidation of Cu Interconnects Capped with CoWP

Published online by Cambridge University Press:  01 February 2011

J. Gambino ,
S. Smith ,
S. Mongeon ,
D. Meatyard ,
F. Chen  and
P. DeHaven
J. Gambino
Affiliation:
IBM Microelectronics, 1000 River Street, Essex Junction, VT, 05452
S. Smith
Affiliation:
IBM Microelectronics, 1000 River Street, Essex Junction, VT, 05452
S. Mongeon
Affiliation:
IBM Microelectronics, 1000 River Street, Essex Junction, VT, 05452
D. Meatyard
Affiliation:
IBM Microelectronics, 1000 River Street, Essex Junction, VT, 05452
F. Chen
Affiliation:
IBM Microelectronics, 1000 River Street, Essex Junction, VT, 05452
P. DeHaven
Affiliation:
IBM Microelectronics, 1000 River Street, Essex Junction, VT, 05452
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Abstract

The thermal oxidation of Cu interconnects, at 350°C in air, has been studied as a function of thickness of a CoWP capping layer. For thin CoWP layers (25 nm), a thick oxide layer (200 nm) is formed which is mainly composed of Cu20. For thick CoWP layers (50 nm), the oxide layer is much thinner (36 nm) and is mainly composed of CoO. For both CoWP thicknesses, depletion of the underlying Cu is often observed after oxidation and whisker growth is often observed on the surface. The results are consistent with an oxidation mechanism where metal is the dominant diffusing species. For thin CoWP layers, Cu diffuses more quickly to the surface than Co, and therefore mainly Cu oxides are formed. For thick CoWP layers, the Cu diffusion to the surface is greatly reduced, and as a result, mainly Co oxides are formed. These results indicate that CoWP is not a good barrier for thermal oxidation, so high temperature exposure to oxidizing ambients must be minimized during processing of integrated circuits where CoWP is used instead of a dielectric barrier.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 863: Symposium B – Materials, Technology and Reliability of Advanced Interconnects , 2005 , B6.11
Copyright
Copyright © Materials Research Society 2005

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