Electromigration measurements in thin-film IPD and eWLB interconnections

In this paper we describe measurements of electromigration failure times in the metal traces of silicon Integrated Passive Devices (IPDs) and in the redistribution layers of embedded Wafer-Level BGA (eWLB) structures, for both aluminum and copper traces, and for via connections between the two metal layers. The results of the test are used to determine the coefficients of Black´s Equation, which is then used to find the extrapolated lifetimes. Maximum current density design guidelines are derived from these results to ensure device reliability in worst-case operation. Some minor differences are observed between these results and similar results for interconnections in conventional ICs. These differences probably arise from the larger conductor cross section and the softer organic dielectrics in IPDs and eWLB packages.