Abstract—CoW (chip on wafer) Cu-Cu low temperature <200°C process is developed for 3D IC stacking application. The CoW process includes chip tacking and global bonding. The bottleneck and challenges are (1) preventing chip shifting during global bonding, (2) Cu height uniformity, (3) reducing bonding temperature and force. A 3D IC with high density I/O test vehicle is designed and demonstrated the low temperature Cu-Cu interconnects application. C2W bonding approach is used for the 3D IC stack bonding method and is found suitable for devices with TSV structure. A novel approach by using Sn electroless plating solution as temperature tacking agent achieved good CoW bonding. It is found that no chip shifting in global bonding. At same time, the bonding force is also reduced from 800N/chip to 100N/chip with bonding temperature at 200°C. Final cross section of bonded sample showed good joint without void.
 

Index Terms—CoW bonding, Cu-Cu, High density I/O, DRAM

Cite: Ling Xie, Sunil Wickramanayaka, Jerry Aw Jie Li, Daniel Ismael Cereno, and Yong Liang Ye, "A Novel Method of CoW Bonding for High Density Ultra-Fine Pitch IC Stacking Application," International Journal of Mechanical Engineering and Robotics Research, Vol. 5, No. 4, pp. 276-279, October 2016. DOI: 10.18178/ijmerr.5.4.276-279