Preparation and characterization of ruthenium films via an electroless deposition route

A metallic Ru film was prepared by an electroless deposition method, followed by hydrogen reduction treatment. The electroless deposition formulation produced a solid film on a Cu-coated Si substrate at 40 °C preactivated by PdCl2 solution. Chemicals including K2RuCl5·xH2O, NaNO2, NaOH, and NaClO were mixed in a proper ratio that enabled heterogeneous nucleation and film growth. Results from X-ray photoelectron spectroscopy (XPS) on the as-deposited films confirmed the presence of RuOx and Ru, while X-ray diffraction (XRD) pattern suggested an amorphous nature. Planar images from a scanning electron microscope revealed a rather smooth surface at thickness less than 250 nm. Above that formation of surface crack and partial detachment from the substrate were observed. After hydrogen reduction at 200 °C for 2 h, we obtained a metallic Ru film, as confirmed by XPS and XRD. In addition, the surface roughness was increased due to the formation of pinholes that was caused by the volume contraction associated with RuOx reduction to Ru.