The effect of metal thickness on electromigration-induced extrusion shorts in submicron technology

Various lifetimes and competing failure modes, i.e., extrusion-shorts and void-opens, were found for W via-stud chains with a layered refractory AlCu interconnect. The goal was to specify the reliability scaling trends of multilevel interconnections with respect to interconnect thickness. Interconnection thickness, interconnection current density, and temperature were found to influence W via-stud lifetime and electromigration failure mode. Selectivity between void-open failure and extrusion-short failure was achieved by changing the interconnection thickness or interconnection current density. Contrary to the results obtained with Al, the location of failures along the layered refractory AlCu metal interconnection suggests that the maximum stress gradient generated by electromigration is away from the end of the interconnection.>