Surface Topography Control for Polymer/Cu Hybrid Bonding

Enormous challenges remain for solder micro-bump bonding to achieve the interconnect pitches below 10 μm, which is required for advanced chiplet integration. Therefore, the application of die-to-wafer Cu-dielectric hybrid bonding has been developed; however, the integration scheme has not yet matured. The biggest obstacles are the yield-loss due to particle residues. To overcome these challenges, polymer/Cu hybrid bonding is being developed. Compared to inorganic dielectric materials such as SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and SiCN, optimization of CMP conditions has not been fully investigated. In this study, we propose a two-step polymer/Cu planarization process. The zeta potential and removal rate of the polymer were assessed. It turns out that alumina base slurry has a higher polymer removal rate than usual silica base slurry. These fundamental evaluations provide insight into improving polymer/Cu planarization.