Atomic layer deposition of Ru thin films using (2,4-dimethyloxopentadienyl)(ethylcyclopentadienyl)Ru and the effect of ammonia treatment during the deposition†
In this study, ruthenium (Ru) thin films were grown on Ta2O5, Si, Ru, and Pt substrates (Ta2O5, Ru, and Pt are thin films, and Si is a bulk wafer) through atomic layer deposition (ALD) using (2,4-dimethyloxopentadienyl)(ethylcyclopentadienyl)Ru [Rudense®] and oxygen as the Ru precursor and the reactant, respectively, at substrate temperatures ranging from 250 °C to 270 °C and ALD chamber pressures ranging from 0.5 Torr to 2.5 Torr. The Ru films showed a high growth rate of 0.83 Å cy−1 except on Pt substrates and negligible incubation cycles. Ru metallic phases were confirmed via resistivity and crystalline structure analyses. A different preferred crystalline orientation of the Ru films was obtained on Pt substrates as compared to other substrates, which resulted in lower growth rates. A smooth and uniform surface was obtained at low thickness; however, the surface morphology abruptly deteriorated as the thickness of the Ru films increased on the Ta2O5 and Si substrates, which was not the case for metallic substrates. Ammonia (NH3) treatment was adopted to enhance the surface morphology of the Ru films by suppressing excessive growth of the RuOx layer, where the adsorbed nitrogen atoms inhibited excessive chemical adsorption of the precursor molecules. The surface roughness and the number of protrusions decreased with appropriate NH3 treatment, while the structural and chemical properties of the metallic Ru films remained unaffected.