Chemical Mechanical Polishing of Plasma‐Modified Cu/Polymer Interfaces for Advanced Hybrid Bonding

Abstract Hybrid bonding, referring to direct bonding between metal and insulator layers, has become a key technology for next‐generation semiconductor packaging, enabling high‐density interconnects, fast signal transmission, and a compact form factor. Polymer dielectrics such as benzocyclobutene (BCB) provide excellent insulation and adhesion but pose challenges for chemical mechanical polishing (CMP) due to their viscoelasticity. Here, a CMP‐compatible strategy based on argon (Ar) plasma modification of BCB is proposed to enable effective planarization of Cu/BCB hybrid bonding interfaces. Ar plasma treatment increases surface hardness and brittleness of half‐cured BCB and increases hydrophilicity. The resulting wrinkle structures improve the flow of abrasive particles and slurry, enabling a plowing‐dominant removal mechanism for precision planarization. Modified BCB shows a removal rate of up to 17.3 nm s ⁻¹ , over five times higher than untreated BCB, while Cu surface roughness is reduced from 51.4 to 3.0 nm. A time‐dependent dishing model is developed to elucidate dishing mechanism and to control dishing geometry precisely. Using this model, a BCB dishing depth of 230 nm is achieved, supporting void‐free and reliable hybrid bonding. Overall, this study presents a simple yet practical approach to CMP of soft polymer dielectrics and offers a promising solution to advanced heterogeneous integration technologies.