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Reservoir effect and the role of low current density regions on electromigration lifetimes in copper interconnects

Published online by Cambridge University Press:  03 March 2011

Z.H. Gan ,
W. Shao ,
S.G. Mhaisalkar ,
Z. Chen ,
Hongyu Li ,
K.N. Tu  and
A.M. Gusak
Z.H. Gan*
Affiliation:
School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798
W. Shao
Affiliation:
School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798
S.G. Mhaisalkar
Affiliation:
School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798
Z. Chen
Affiliation:
School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798
Hongyu Li
Affiliation:
Institute of Microelectronics, Singapore 117685
K.N. Tu
Affiliation:
Department of Materials Science and Engineering, University of California—Los Angeles, Los Angeles, California 90095-1595
A.M. Gusak
Affiliation:
Cherkasy National University, Cherkasy 18017, Ukraine
*
a) Address all correspondence to this author. e-mail: EZHgan@yahoo.com.sg
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Abstract

Electromigration (EM) in copper dual-damascene interconnects with extensions(also described as overhang regions or reservoirs) in the upper metal (M2) were investigated. It was found that as the extension length increases from 0 to 60 nm, the median-time-to-failure increased from 50 to 140 h, representing a ∼200% improvement in lifetimes. However, further increment of the extension length from 60 to 120 nm did not result in any significant improvement in EM lifetimes. Based on calculations of current densities in the reservoir regions and recently reported nucleation, void movement, and agglomeration-based EM phenomena, it is proposed that there is a critical extension length beyond which increasing extension lengths will not lead to longer EM lifetimes.

Keywords

CuElectromigrationScanning electron microscopy (SEM)
Type
Articles
Information
Journal of Materials Research , Volume 21 , Issue 9 , September 2006 , pp. 2241 - 2245
Copyright
Copyright © Materials Research Society 2006

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References

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