Mechanistic Atomic Hydrogen Chemistry for Ruthenium Deposition: From Ligand Elimination to Area-Selective Patterning

Atomic layer deposition (ALD) of ruthenium (Ru) has been extensively investigated for semiconductor applications due to the numerous advantages of Ru. However, conventional Ru ALD has primarily relied on combustion reactions using oxygen-based reactants for the removal of ligands. This approach poses significant challenges, such as the formation of undesirable interfacial oxide layers and oxygen diffusion into the Ru layer. While reduction-based Ru ALD using H₂ has been studied as a potential solution, it typically requires a high thermal budget to overcome the formidable energy barrier for H₂ dissociation on the ligands of the adsorbed precursor. In this study, we applied a dissociated reactant such as atomic hydrogen to circumvent the energy barrier for H₂ dissociation. By bypassing the energy-intensive H₂ dissociation step, this method fundamentally lowers the reduction energy barrier, enabling the growth of high-purity metallic Ru films with a low resistivity of 23.7 μΩ·cm at a significantly reduced temperature of 100 °C. Furthermore, this ALD process using dissociated species was successfully extended to area-selective deposition. We investigated the interaction between the inhibitor and dissociated species. It was found that this species could partially remove the inhibitor layer, which was effectively addressed by introducing a strategic redosing process to improve selectivity. The reactivity and reaction pathways of dissociated species were systematically elucidated through theoretical analyses, including density functional theory, molecular dynamics, and Monte Carlo simulations.