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Electromigration-Induced Plastic Deformation in Cu Damascene Interconnect Lines as Revealed by Synchrotron X-Ray Microdiffraction

Published online by Cambridge University Press:  01 February 2011

Arief Budiman ,
N. Tamura ,
B. C. Valek ,
K. Gadre ,
J. Maiz ,
R. Spolenak ,
J. R. Patel  and
W. D. Nix
Arief Budiman
Affiliation:
suriadi@stanford.edu, Stanford University, Materials Science & Engineering, 416 Escondido Mall, Peterson Building #550, Room 554G, Stanford, CA, 94305, United States
N. Tamura
Affiliation:
ntamura@lbl.gov, Advanced Light Source (ALS), Ernest Orlando Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA, 94720, United States
B. C. Valek
Affiliation:
bcvalek@lbl.gov, Advanced Light Source (ALS), Ernest Orlando Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA, 94720, United States
K. Gadre
Affiliation:
kaustubh.s.gadre@intel.com, Intel Corporation, Hillsboro, OR, 97124, United States
J. Maiz
Affiliation:
jose.maiz@intel.com, Intel Corporation, Hillsboro, OR, 97124, United States
R. Spolenak
Affiliation:
ralph.spolenak@mat.ethz.ch, Department of Materials, ETH Zurich, Zürich, N/A, CH-8093, Switzerland
J. R. Patel
Affiliation:
jpatel@slac.stanford.edu, Stanford University, Dept. of Materials Science & Engineering, Stanford, CA, 94305, United States
W. D. Nix
Affiliation:
nix@stanford.edu, Stanford University, Dept. of Materials Science & Engineering, Stanford, CA, 94305, United States
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Abstract

The Scanning X-Ray Submicron Diffraction (μ-SXRD) technique using focused synchrotron radiation white beam developed in the Beamline 7.3.3 at the ALS Berkeley Lab has been used to study the microstructural evolution at granular level of Cu polycrystalline lines during electromigration. Plastic deformation was observed in damascene Cu interconnect test structures during this in situ electromigration experiment and before the onset of visible microstructural damage (voiding, hillock formation). We show here that the extent of this electromigration-induced plasticity is dependent on the line width. In wide lines, plastic deformation manifests itself as grain bending and the formation of subgrain structures, while only grain rotation is observed in the narrower lines. The analysis of the Laue reflections allow for the determination of the geometrically necessary dislocation density in individual grains as well as for the misorientation angles between small angle boundaries generated by polygonization. The deformation geometry leads us to conclude that dislocations introduced by plastic flow lie predominantly in the direction of electron flow and may provide additional easy paths for the transport of point defects. Furthermore, we observe that the rotation axis of this plastic deformation coincides with one of the <112> line directions of the known slip systems for FCC crystal, and that it is always very close (within a few degrees) to the direction of the electron flow. This finding suggests a correlation of the proximity of certain <112> line directions to the direction of electron flow with the occurrence of plastic behavior. One important practical implication of this particular finding is that the grain texture of the line might thus play an important role in giving higher resistance towards early plastic response of the Cu line upon the electromigration loading.

Keywords

electromigrationCux-ray diffraction (XRD)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 914: Symposium F – Materials, Technology and Reliability of Low-k Dielectrics and Copper Interconnects , 2006 , 0914-F06-05
Copyright
Copyright © Materials Research Society 2006

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