Effect of Ag3Sn: Effective suppression of thermomigration-induced Cu dissolution in micro-scale Pb-free interconnects

Dissolution of Cu under bumping metallization (UBM) and decomposition of Cu6Sn5 intermetallic compounds (IMC) induced by a temperature gradient are serious reliability issues in newly-developed three-dimensional integrated circuits (3D IC) packaging. Based on the experimental observation, both Ag3Sn particles and plates are found to exhibit the ability to inhibit the dissolution of Cu at the hot end and the abnormal accumulation of IMCs at the cold end. The finding in this study suggests that Ag3Sn could be an effective diffusion barrier to retard the thermomigration of Cu in micro-scale interconnects.