Chip-to-wafer Polymer Hybrid Bonding for Low-Temperature Process

ABSTRACT For avoiding device damage from thermal budget, polymer hybrid bonding technology has been developed with a novel low-temperature curable polyimide. All process flow of the hybrid bonding has been done at or lower than 250°C. Special technique of Cu protrusion on hybrid bonding surface has been demonstrated by CMP optimization due to CTE mismatch between polyimide and Cu. The Cu protrusion technique has worked well electrical connection for Cu to Cu bonding each hybrid bonding surface. No voids at an interface between polymers after direct bonding are observed due to insensitive particles from dicing process. Sufficient rates of chemical mechanical polishing (CMP) with alkaline slurry for formation of bonding surface are obtained. Furthermore, polyimide-to-polyimide bonding mechanisms were investigated from the chemical and physical aspects of the material, respectively. Cu migration test with the novel polyimide shows good result even after high temperature high humidity test.