Demonstration of high electromigration resistance of enhanced sub-2 micron-scale Cu redistribution layer for advanced fine-pitch packaging

Downsizing the Cu signal traces in the redistribution layer is an effective approach to increasing the number of signal I/O lines and thereby greatly increasing signal processing performance between logic and memory chips in advanced fine-pitch packaging. Downsized Cu traces, however, are vulnerable to current stress, which degrades electromigration resistance. This is a serious problem in advanced fine-pitch packaging. In a conventional redistribution layer, the Cu traces are completely covered with an organic dielectric. Weak adhesion force between the traces and the dielectric accelerates electromigration, in addition to causing current stress. Thus, interfacial modification of the Cu traces is critical to enhancing electromigration resistance. In this report, we introduce a new type of redistribution layer structure in which the Cu traces are completely covered with inorganic dielectrics. This structure increases electromigration resistance as much as 10,000 times that of Cu traces in a conventional redistribution layer.