Electromigration in multilevel interconnects with polymeric low-k interlevel dielectrics

The impact of low-k dielectrics on the reliability of advanced Cu interconnects is of growing importance. As a first step to understanding this impact, we have investigated the effect of two types of polymeric low-k materials on the electromigration (EM) behavior of multilevel Al(Cu) interconnects. The two polymers used as interlevel dielectrics in this work are a fluorinated polyimide and a poly(aryl) ether. Joule heating experiments and microstructural analysis were both conducted on Al(Cu) to ensure that there were no significant microstructural or thermal differences between the polymer samples and their oxide counterparts. The resulting EM behavior can then be directly attributed to differences in the mechanical properties of the low-k and oxide interlevel dielectrics. We have observed that the low-k samples had a higher steady-state drift rate and did not reach saturation, resulting in shorter EM lifetimes. These results indicate that the short length is greatly modified with the incorporation of me...