Effect of Layout Variation on Stress Migration in Dual Damascene Copper Interconnects

Abstract

The effect of layout variation on stress migration (SM) in Cu damascene interconnects was investigated in detail. In an extrusion pattern in which narrow lines are connected to a wide line, the failure rate decreases as the narrow line becomes longer and wider. It was found that there is a maximum failure rate between 150 and 200 °C for all test patterns. The results for the SM failure rate showed that the initial rate of increase of SM failure for the extrusion pattern is much larger than that for the conventional wide pattern. The effect of the narrow linewidth on the SM failure rate cannot be understood by considering the previous diffusion mechanism. Based on these results, the dependence of vacancy diffusion path and SM failure mechanism on the layout variation is discussed.