Selective self-assembled monolayer coating to enable Cu-to-Cu connection in dual damascene vias

In order to enable an oxide-free Cu-to-Cu bonding in a (dual) damascene process, 3-aminopropyltrimethoxysilane- and decanethiol-derived self-assembled monolayers are selectively deposited in a dielectric-Cu based metal-insulator-metal (MIM) capacitor used as a test vehicle, which represents a dual damascene architecture environment. A two-steps SAM coating sequence is investigated for this purpose. In a first step, a ''sacrificial'' SHSAM is deposited on the Cu areas at the bottom of the vias. In a second step, a ''barrier'' NH"2SAM is deposited on the dielectric areas in the field region and via's sidewalls. This deposition sequence followed by the selective thermal ablation of the ''sacrificial'' SAM vs. the ''barrier'' SAM, enable an oxide-free Cu-to-Cu connection at via's bottom. The differential in thermal stability between the amino and thiol SAMs has been studied by water contact angle and cyclic voltammetry. While the sacrificial SAM is selectively desorbed by thermal ablation already at ~200^oC, the barrier SAM on the dielectric sidewall and field regions withstands a thermal budget as high as ~350^oC. The substrate-selective SAMs depositions are revealed by XPS chemical characterization on the Cu and dielectric areas of the MIM structures supported by the SEM visualization of the Au nanoparticles that selectively decorate the NH"2 functionalities of the barrier SAM.