Electromigration-Induced Plasticity: Texture Correlation and Implications for Reliability Assessment
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Plastic behavior has previously been observed in metallic interconnects undergoing high-current-density electromigration (EM) loading. In this study of Cu interconnects, using the synchrotron technique of white-beam x-ray microdiffraction, we have further found preliminary evidence of a texture correlation. In lines with strong (111) textures, the extent of plastic deformation is found to be relatively large compared with that of weaker textures. We suggest that this strong (111) texture may lead to an extra path of mass transport in addition to the dominant interface diffusion in Cu EM. When this extra mass transport begins to affect the overall transport process, the effective diffusivity, D eff, of the EM process is expected to deviate from that of interface diffusion only. This would have fundamental implications. We have some preliminary observations that this might be the case, and report its implications for EM lifetime assessment herein.
KeywordsElectromigration copper interconnects texture plasticity reliability dislocations x-ray microdiffraction
The authors would like to thank Advanced Micro Devices (AMD) for generous support and for fabricating the samples in the study. Bryan Tracy of Spansion provided the FIB images in Fig. 1. One of the authors (A.S.B.) would like to thank John M. Ennals, the the AMD/SRC Program Manager at AMD, for the opportunity of a Summer Internship Program in 2006. Both A.S.B. and W.D.N. gratefully acknowledge support by the US Department of Energy, Office of Basic Energy Sciences through Grant No. DE-FG02-04ER46163. The Advanced Light Source (ALS) is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No.␣DE-AC02-05CH11231 at the Ernest Orlando Lawrence Berkeley National Laboratory (LBNL).
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