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Effectiveness and Reliability of Metal Diffusion Barriers for Copper Interconnects

Published online by Cambridge University Press:  15 February 2011

G. Bai ,
S. Wittenbrock ,
V. Ochoa ,
R. Villasol ,
C. Chiang ,
T. Marieb ,
D. Gardner ,
C. Mu ,
D. Fraser  and
M. Bohr
G. Bai
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
S. Wittenbrock
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
V. Ochoa
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
R. Villasol
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
C. Chiang
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
T. Marieb
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
D. Gardner
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
C. Mu
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
D. Fraser
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
M. Bohr
Affiliation:
Intel Corporation, Santa Clara, CA 95052.
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Abstract

Cu has two advantages over Al for sub-quarter micron interconnect application: (1) higher conductivity and (2) improved electromigration reliability. However, Cu diffuses quickly in SiO2and Si, and must be encapsulated. Polycrystalline films of Physical Vapor Deposition (PVD) Ta, W, Mo, TiN, and Metal-Organo Chemical Vapor Deposition (MOCVD) TiN and Ti-Si-N have been evaluated as Cu diffusion barriers using electrically biased-thermal-stressing tests. Barrier effectiveness of these thin films were correlated with their physical properties from Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), Secondary Electron Microscopy (SEM), and Auger Electron Spectroscopy (AES) analysis. The barrier failure is dominated by “micro-defects” in the barrier film that serve as easy pathways for Cu diffusion. An ideal barrier system should be free of such micro-defects (e.g., amorphous Ti-Si-N and annealed Ta). The median-time-to-failure (MTTF) of a Ta barrier (30 nm) has been measured at different bias electrical fields and stressing temperatures, and the extrapolated MTTF of such a barrier is > 100 year at an operating condition of 200C and 0.1 MV/cm.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 403: Symposium I – Polycrystalline Thin Films: Structure, Texture, Properties and Applications II , 1995 , 501
Copyright
Copyright © Materials Research Society 1996

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References

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