Electromigration-induced strain relaxation in Cu conductor lines


Strain evolution in 0.45-μm-thick, 2-μm-wide, and 100-μm-long Cu conductor lines with a passivation layer has been investigated using synchrotron x-ray microdiffraction. A moderate electromigration-current density of 2.2 × 105 A/cm2 was used to minimize Joule heating in the Cu conductor lines. After 120 h of current flowing in the Cu lines at 270 °C, measurements show strain relaxation and homogenization occurring in the Cu lines with current flowing, but not in Cu conductor lines without current. Stronger interaction between electrons with Cu atoms in areas with higher strains was proposed to explain the observation.

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The authors of this study thank Dr. C-K. Hu at the IBM T.J. Watson Research Center for useful guidance and for providing the Cu conductor line samples. Dr. W. Liu from Argonne National Laboratory provided valuable assistance with the synchrotron x-ray microdiffraction measurements and data analysis.

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Zhang, H., Cargill, G. Electromigration-induced strain relaxation in Cu conductor lines. Journal of Materials Research 26, 498–502 (2011). https://doi.org/10.1557/jmr.2011.2

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