Feasibility study on ultrafine-pitch Cu-Cu bonding using directed self-assembly (DSA)

A feasibility study was carried out for self-formation of metal wiring between LSI chips containing ultrafine-pitch Cu landing pads by employing a new concept of directed self-assembly (DSA) phenomena. Preliminary results suggest that it is highly feasible to electrically interconnect two LSI chips having Cu landing pads at 3μm pitch interval. Electrical contact between the flip-chip bonded dies was self-formed by dispersed Sn nano-dots in PS-b-PMMA (2:1) copolymer mixture after vacuum annealing at 280 °C.