Investigation on the Growth Initiation of Ru Thin Films by Atomic Layer Deposition

Ru thin films were grown on Au, Pt, TiN, TiO 2, and SiO 2 substrates by atomic layer deposition using 2,4-(dimethylpentadienyl)(ethylcyclopentadienyl)Ru (DER) dissolved in ethylcyclohexane at a concentration of 0.2 M as the Ru precursor and O 2 as the reactant. There was a long incubation time for Ru film deposition on TiN and SiO 2 due to the weak interaction between DER and the covalent bonds in TiN and SiO 2 . On the other hand, the Ru films on TiO 2 exhibited a shorter incubation time. There was a negligible incubation time for Ru film deposition on Au and Pt due to the strong interactions between the DER precursor and metallic surfaces, resulting in a smooth surface morphology and strong c -axis texture. A continuous Ru film, not an island-shaped film, was formed on Au, which does not catalytically dissociate molecular oxygen, even at a film thickness of 1 nm. Therefore, the initial growth of Ru thin films was determined by the adsorption of the metal precursor not the catalytic dissociation of molecular oxygen.