A novel fine pitch TSV interconnection method using NCF with Zn nano-particles

Non-conductive film (NCF) with Zn nano-particles is an effective solution for fine-pitch Cu-pillar/Sn-Ag hybrid bump interconnection in terms of manufacturing process and interfacial reliability. In this study, NCFs with Zn nano-particles of different acidity, viscosity, and curing speed were formulated, and diffused Zn contents in the Cu pillar/Sn-Ag hybrid bumps were measured after 3D TSV chip-stack bonding. Amount of Zn diffusion into the Cu pillar/Sn-Ag bumps increased as the acidity of resin increased, as the viscosity of resin decreased, as the curing speed of resin decreased, and as the bonding temperature increased. Diffusion of Zn nano-particles into the Cu pillar/Sn-Ag bumps are maximized when the resin viscosity became lowered and the solder oxide layer was removed. To analyze the effect of Zn on IMC reduction, NCFs with 0 wt%, 1 wt%, 5 wt%, and 10 wt% of Zn nano-particles were bonded on the test vehicles, and aged at 150°C up to 500 hours. NCF with 10wt% Zn nano-particle showed remarkable suppression in Cu₆Sn₅ and (Cu, Ni)₆Sn₅ IMC compared to NCFs with 0 wt%, 1 wt%, and 5 wt% of Zn nano-particles. However, in terms of Cu₃Sn IMC suppression, which is the most critical goal of this experiment NCFs with 1 wt%, 5wt%, and 10wt% showed an equal amount of IMC suppression. As a result, it was successfully demonstrated that the suppression of Cu-Sn IMCs was achieved by the addition of Zn nano-particles in the NCFs resulting an enhanced reliability performance in the Cu/Sn-Ag hybrid bumps bonding in 3D TSV interconnection.