High Electromigration Lifetimes of Nanotwinned Cu Redistribution Lines

In this paper, we measured the electromigration lifetimes for nanotwinned copper (nt-Cu) and regular copper redistribution lines (RDLs) for 3D-ICs packaging. The width of the RDLs is 10μm in width and 5μm in thickness, and the lines were coated by polyimide. The average lifetime of the nt-Cu RDL copper line is 445 hours to reach 1.2 times of its initial resistance. However, it takes 160 hours to reach the same resistance increase for regular copper RDL line. The nt-Cu has better EM lifetime than regular copper.