Confined IMCs for low temperature and high throughput D2W bonding

In this paper an integration flow is introduced for IMC insertion bonding, enabling stacking microbumps with 10um and below pitches. Confined CoSn3 pre-IMC bumps inside the cavities prevent lateral IMC growth and provide mechanical connection between Sn and sharp IMC grains during low temperature TCB process and improve the alignment. Electrical yield of 95% is obtained for single bumps connection of 20, 10 and 7um pitch bumps.