Improved yield and reliability in aluminum interconnects through fluorine incorporation

It is argued that the substantial reduction in hillock formation with F (fluorine) incorporation (relative to Cu incorporation) is predominantly due to the reactive nature of the F. The highly electronegative fluorine forms a much stronger chemical bond than aluminum with itself or aluminum with Cu, which acquires its beneficial effects from forming Cu precipitates at grain boundaries. Due to the significant improvement in hillock formation behavior with these very small F incorporations, it seems that electromigration and stress-induced voiding could also be reduced by a similar technique. Test data leading to these conclusions are presented