Exploring the Potential of Fly Cutting for Polymer Planarization in Cu/PDMS Hybrid Bonding

3D packaging technology has been rapidly advancing to meet the demands of high-performance computing, and the importance of hybrid bonding is increasingly emphasized. Cu/polymer hybrid bonding offers advantages such as flexibility and simplified processing. This study explores the feasibility of applying fly cutting for co-planarizing Cu/PDMS in hybrid bonding. Experimental results show that fly cutting achieves an extremely low roughness of less than 1 nm on Cu surfaces and a roughness of approximately 6–7 nm on PDMS surfaces. However, achieving optimal planarization for soft polymers like PDMS remains a significant challenge. This study demonstrates the potential and limitations of fly cutting for Cu/polymer hybrid bonding and provides insights into future research directions aimed at process optimization.