Low Temperature and Fine Pitch Nanocrystalline Cu/SiCN Wafer-to-Wafer Hybrid Bonding

The fine-pitch wafer-to-wafer hybrid bonding technique allows for high integration density in high-memory bandwidth packaging. This paper demonstrates the nanocrystalline copper (nc-Cu) /SiCN wafer-to-wafer hybrid bonding process. The nc-Cu material can be filled using either an electrochemical deposition or physical vapor deposition facility, with an average grain size of approximately 80 nm. Additionally, a nearly 200 nm thick SiCN layer was deposited on a SiO2 layer as a dielectric bonding layer on the 12-inch wafer. chemical mechanical polishing as essential for polishing the nc-Cu and SiCN layers to increase bonding performance, achieving a roughness Ra of 0.44 nm and dishing of 1.78 nm. The hybrid bonding process was completed using a 2.5 mu m fine-pitch nc-Cu/SiCN hybrid structure, which significantly reduced the bonding temperature to 200 oC. The highly (111)-preferred orientation of the nc-Cu pads proved to be a promising bonding material for low-temperature bonding. Overall, this study achieved nearly 80% of a good bonding interface without large voids. In conclusion, this study successfully achieved low-temperature and fine-pitch nc-Cu/SiCN wafer-to-wafer hybrid bonding at 200 oC. This extraordinary interconnection technology is expected to benefit future trends in advanced packaging.