An analytical model for linewidth-dependent electromigration lifetime in VLSI interconnects

An analytical model for linewidth-dependent electromigration lifetime is proposed. Agreement between the model prediction and experimental data is excellent. The application of this model to design rule definition versus linewidth is discussed. As the linewidth of VLSI metallization interconnects continues to scale down, the reliability performance becomes an increasingly important issue. It has been found experimentally for various metallization systems that the electromigration MTTF (mean time to failure) decreases as the linewidth is reduced but apparently levels off and increases when the linewidth becomes comparable to or less than the average grain size of the metal. It is argued that this increase in the MTTF, however, does not necessarily imply a better reliability performance since the associated standard deviation has also been observed to increase with decreasing linewidth. Understanding this effect and its resultant scaling law on design rules is important in using narrow-linewidth metallization systems beneficially