Hybrid bonding of Cu/Sn microbump and adhesive with silica filler for 3D interconnection of single micron pitch

This paper describes hybrid bonding technology of Cu/Sn microbumps and adhesive with silica filler for three-dimensional (3D) interconnection of single-micron pitch. We fabricated bonding structure composed of 8-μm pitch Cu/Sn bumps and uncured adhesive with by using combination process of resin-chemical mechanical polishing (CMP) and O₂/CHF₃ plasma etching. Adhesive with silica filler is conventionally used for reduction of mechanical stress around microbumps by lowering CTE of underfill. With the bonding structure, the Cu/Sn microbumps and the adhesive were simultaneously bonded in N₂ atmospheric pressure after surface treatment of Ar/H₂ plasma irradiation. Results of scanning electron microscope (SEM) and scanning ion microscope (SIM) analyses show that Sn of microbumps was properly wetted on Cu film without resin and silica filler trapping. The adhesive was also bonded on Cu film in 6-μm gap between chips. The shear strength was 17.85 MPa. Therefore, proposed method is highly effective for hybrid bonding of single-micron pitch aimed at future ultra-high density 3D interconnection.