Electromigration simulation of Cu pillar interconnect microstructure of 3D packaging

While the size of electronic devices continues to decrease and the I/O number per chip keeps increasing, the size and pitch of solder bumps are required to be as small as possible. This case gives rise to great concerns on their quality and reliability. As a 3D integration alternative to solder bumps, Cu-pillars have been proposed due to their better electromigration-resistance and other performance. In this paper, the electromigration simulation of a new Cu-Sn-Ni-Cu interconnection microstructure is carried out. An electric-thermal-mechanical model of the Cu-Sn-Ni-Cu interconnect microstructures is developed by ANSYS software. The diameter of Cu-Sn-Ni-Cu column is 10 μm and its height is 5 μm. The distributions of temperature, current density and effective stress are calculated based on the current density, temperature gradient and stress distribution. Influence of the ambient temperature, applied current density and the diameter of Cu-Sn-Ni-Cu interconnect column on the driving force of atomic migration are investigated. The migration force is used to predict the position where the migration is most likely to occur.