Different Chemical Mechanical Polishing (CMP) slurries are used to obtain single-damascene Cu-wires with different surface fluctuations as well as pre-existing surface-defects in the lines with rougher surface.The presence of such pre-existing defects strongly increases the rate of early failures up to almost 100%

reduces electromigration lifetime rapidly to the level of early failures

and changes the multimodal failure distribution into monomodal.The activation energy (0.74±0.02 eV) for the failure mechanism associated with these pre-existing defects confirms a dominant surface diffusion.We show how a Weakest Link Approximation analysis can be applied to single lines by dividing the lines into relevant segments and assigning different failure mechanisms to the various segments.The analysis confirms that

although surface-defects are not the fastest early failure mechanism

the 1-magnitude higher surface-defect-density in the rougher lines is responsible for the observed high early-failure rate and poor reliability performance.