Low-Temperature Co-hydroxylated Cu/SiO₂ Hybrid Bonding Strategy for a Memory-Centric Chip Architecture

Cu/SiO₂ hybrid bonding with planarized dielectric and isolated metal connections can realize ultradense interconnects (e.g., ≤1 μm) by eliminating the microbumps and underfill through the direct bonding of Cu-Cu and SiO₂-SiO₂. However, the low-temperature bonding of Cu-Cu (oxide-free surface) and SiO₂-SiO₂ (hydroxylated surface) is difficult to be compatible in a mechanism. We circumvent this contradiction by constructing a co-hydroxylated functional surface on a Cu/SiO₂ hybrid platform. By combining and optimizing the protocol of Ar/O₂ plasma activation and formic acid solution immersion, an -OH active layer was successfully established on the Cu and SiO₂ surfaces simultaneously, and the increased total surface area provided more adsorption sites for hydroxyl groups. A Cu-Cu interface with sufficient atom diffusion, substantial grain growth, and fewer microvoids was obtained at 200 °C. Notably, the carbon-related interlayer that may degrade the interfacial performance could be effectively inhibited across the optimized SiO₂-SiO₂ interface even if organic acid was introduced in the protocol. This low-temperature Cu/SiO₂ hybrid bonding via a co-hydroxylated strategy may inspire the development of a memory-centric chip architecture and functional integrated circuits delivering a monolithic-like performance in the future hyperscaling era.