Abstract
For the past several years, fabrication of fast and reliable metal interconnections for high-performance devices has been associated with the defect-free Cu superconformal electrodeposition (superfilling) in damascene structure using organic additives, which were made up of mercapto-group accelerator and polymer-halide complex suppressors. Therefore, highly incomprehensible additive chemistry and deterioration in film quality by additives, i.e., degradation of electrical properties, crystallographic orientation, and grain growth rate are unavoidable. In this study, microcontact printing (micro CP) using nm-thick self-assembled monolayers (SAMs) of 1-decanethiol on a flat poly(dimethylsiloxane) stamp was used to form trench-selective Cu superconformal filling on damascene structure. This is a novel approach free from complications originated from organic additives. SAMs transferred on the top surface of (111)-oriented Cu trench entrance (structure of 70 nm Cu/10 nm TiN/15 nm Ti/Si, single damascene, line width of 500 nm, aspect ratio of 2.5) by micro CP served as a barrier for deposition current transfer. Below a certain potential that was not yet dominated by the tunneling current, SAMs on the Cu surface could successfully suppress current flow through the interface of Cu/H2SO4 electrolyte and inhibit deposition. When the micro CP was applied to a damascene structure, deposits of void/seam-free and bumps indicative of superconformal filling were obtained, which was a match for the three-additive system. Surface diffusion of 1-decanethiol molecules, an important factor in the shape of the deposits, was strongly dependent on contact time.
