Thermal atomic layer deposition of metallic Ru using H2O as a reactant

Thin Ruthenium (Ru) films were deposited on native SiO₂ on Si substrate by thermal atomic layer deposition (ALD) using dicarbonyl-bis(5-methyl-2,4-hexanediketonato)Ru(II) precursor with O₂ and H₂O as reactant. In the case of the O₂ process, increase in the O₂ pulse led to oxidation of the film into RuO₂. In contrast, purely metallic Ru thin film without significant oxidation was formed using H₂O, even with extended H₂O pulse. Using H₂O, growth rate of ~0.75 Å/cycle and electrical resistivity of ~18 μΩcm for metallic Ru were obtained at temperatures as low as 250 °C. Through density functional theory (DFT) calculations, it is shown that adsorption of the Ru precursor would spontaneously occur on metallic Ru surface. Ru ALD using H₂O reactant is performed on SiO₂ powder to successfully form Ru@SiO₂ core-shell structure, demonstrating applicability of this process to substrates with morphological complexity, which often require extended exposures of reactants.