All-wet encapsulation and electroless superfilling process for the fabrication of self-assembled-monolayer encapsulated copper interconnects with enhanced electromigration reliability

Abstract The continued downscaling of integrated circuits has brought into focus the development of new molecularly thick barrier/capping materials and novel fabrication processes for Cu interconnects with gradually diminished lateral dimensions. Here, an all-wet encapsulation/electroless superfilling process is developed for the first time to lay an amino-based self-assembled monolayer (SAM) all around nanoscaled Cu interconnects embedded in SiO2. Under bias stressing (8.0 × 108–1.6 × 109 A/cm2), premature failure of otherwise identical but bare Cu interconnects occurs within a few seconds. However, SAM-encapsulated Cu interconnects are extremely EM resistant with lifetimes on the order of 103 s under the same rigorous bias stressing. The strengthening mechanism is elucidated experimentally from imaging observations of electric-field induced Cu diffusion routes and theoretically from the prediction of the Black’s equation in terms of EM-induced failure modes.