Wet-chemical Cu Cleaning for Fine-Pitch Hybrid Bonding

Abstract

Cu/SiCN hybrid bonding is an essential technology for the further increase of IO densities in 3D integration and chiplets. The yield of the hybrid bonding relies on the surface fabrication steps. CMP is the primary contributor to the surface topography, where the acceptable recess amount on the Cu pad is 3 nm at below 200 nm pitch. Furthermore, the impact on the Cu pad recess during the post-CMP clean is not negligible at such a finer-pitch hybrid bonding. This study focuses on the post-CMP cleaning process, evaluating functional water compared to formulated chemical cleaners. Functional water is known as equivalent wet cleaning performance while preventing Cu recess as formulated post-Cu cleaner. Furthermore, it was shown that optimized functional water can effectively remove slurry abrasives and particles from the Cu surface. In addition, the impact of functional water in the DIW rinse before bonding was investigated.