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A Statistical Characterization of Electromigration-Induced Open Failures in 2-Level Metal Structures

Published online by Cambridge University Press:  15 February 2011

H. Kahn  and
C. V. Thompson
H. Kahn
Affiliation:
Massachusetts Institute of Technology, Department of Materials Science and Engineering, Cambridge, MA 02139
C. V. Thompson
Affiliation:
Massachusetts Institute of Technology, Department of Materials Science and Engineering, Cambridge, MA 02139
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Abstract

A new electromigration test structure has been designed and fabricated which allows statistical characterization of current-induced open failures at vias, under varying current flow geometries. Results for a 2-level Al-Cu metallization system with W-filled 1.0 μm vias reveal no differences in via lifetimes for parallel, anti-parallel, or perpendicular current flows. However, a factor of 7 improvement in the total average via resistance produces an order of magnitude improvement in lifetimes. Line reliability remains superior to the reliability of the vias, indicating that the vias are the “weak links” in the system.

A model for evaluating temperature and current density effects which incorporates the atomic flux equation has been developed and used to make reliability predictions for extrapolations to operating conditions. The model suggests that the median time to failure of a 2-level ietal structure with an average via resistance of two ohms will be 2.7×1017 hours for operating conditions of 2×105 A/cm2 and 125°C.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 225: Symposium G – Materials Reliability Issues in Microelectronics , 1991 , 15
Copyright
Copyright © Materials Research Society 1991

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References

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