Abstract
The evolution of grain structures and microstructures in Cu/Sn–3.5Ag/Cu-xZn (x=0 or 15 wt%) TLP bonding before and after aging were investigated. Cu-Sn intermetallic compounds (IMCs) with a strong [001] orientation rapidly form from the Cu pads and cause impingement in TLP bond, allowing cracks to easily propagate. During aging, the Cu 6 Sn 5 becomes one layer with a homogeneous structure, thick Cu 3 Sn layers form, and Kirkendall voids occur at bonding interfaces, causing degradation of bonding strength. This study demonstrates that doping Zn into one of the Cu substrates efficiently retains the multi-orientation structure of Cu-Sn IMCs and suppresses the formation of Cu 3 Sn during lone-time aging. The Cu/Sn–3.5Ag/Cu–15Zn TLP bonding is potentially useful in strengthening the interconnections for novel 3D-IC technologies.