DFT modeling of atomic layer deposition of Ru interconnect metal for EUV scaling

Density functional theory (DFT) simulations have been applied to understand the surface reaction mechanisms for the selective deposition of Ru metal for use in vias or interconnects. Ruthenium-ALD with bis-(ethylcyclopentadienyl)-ruthenium [Ru(EtCp)(2)] and O-2 as reactants shows promising surface selectivity but necessitates activation steps for desorption of ligands to complete each ALD cycle. DFT modeling of Ru(EtCp)(2) on Ru surfaces reveals that ALD processes are limited by the strong aromatic-ring interaction with the metallic surface. Introduction of atomic H as a nonoxidizing co-reactant gas in place of O-2 can overcome these barriers by saturation of the Cp pi-bonds, weakening the bonds to the metallic Ru surface. This study aims to provide a comprehensive understanding of leveraging ligand-surface, surface-hydrogen, and ligand-hydrogen interactions to achieve oxygen-free ALD with the Ru(EtCp)(2) precursor at moderate to low temperatures.