Study of electron-scattering mechanism in nanoscale Cu interconnects

This paper presents a study of electron scattering in damascene-processed Cu interconnects. To understand the leading electron-scattering mechanism responsible for the size effect, Cu interconnects with varying physical widths, 80–750 nm, were made, and their resistivity characterized as a function of temperature, ranging from liquid He temperature (4.2 K) to 500 K. The resulting data suggest that surface scattering, contrary to expectations, was not the primary cause of the size effect observed in this investigation. Surface scattering was found to weaken with decreasing line width. Further analysis leads to the conclusion that a substantial fraction of the size effect originates from impurity content scaling inversely with width in these samples.