Non-conductive film with Zn-nanoparticles (Zn-NCF) for 40 μm pitch Cu-pillar/Sn–Ag bump interconnection

Abstract

Non-conductive film with Zn nano-particles (Zn-NCF) is an effective solution for fine-pitch Cu-pillar/Sn–Ag 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 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 effects of Zn-NCF on IMC reduction, IMC height depending on aging time was measured and corresponding activation energies for IMC growth were calculated. For the evaluation of joint reliabilities, test vehicles were bonded using NCFs with 0wt%, 1wt%, 5wt%, and 10wt% of Zn nano-particles and aged at 150°C up to 500h. NCF with 10wt% Zn nano-particle showed remarkable suppression in Cu6Sn5 and (Cu,Ni)6Sn5 IMC compared to NCFs with 0wt%, 1wt%, and 5wt% of Zn nano-particles. However, in terms of Cu3Sn IMC suppression, which is the most critical goal of this experiment NCFs with 1wt%, 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 bumps bonding in 3D TSV interconnection.