Investigation of Low Temperature Cu Pillar Eutectic Bonding for 3D Chip Stacking Technology

In this study, a chip level Cu pillar to In/Sn pad thermocompression bonding (TCB) structure was investigated. After reaching the target bonding force and the melting point of the pad, the In/Sn pad was in its liquid phase for a short time and then quickly diffused into the Cu pillar, which demonstrates that Cu-solder bonding with low bonding temperature (150 °C) and short bonding time (1 min) can be realized in atmospheric environment. These bonding results with good electrical performance and bonding quality show the potential of this chip level stacking process.