The effect of UV-O-3 treatment on the nucleation behavior of ruthenium (Ru) film on low-k dielectrics was investigated. A continuous Ru film was not formed on the as-deposited or N-2-annealed low-k layer, but after the UV-O-3 treatment, full coverage with a continuous Ru layer was obtained. The microstructure and Ru/low-k interface were studied using transmission electron microscopy, specular X-ray reflectivity, and Auger electron spectroscopy. The enhanced nucleation behavior of Ru may be due to the increased chemisorption probability of the Ru precursor on the low-k film surface, which comes from a modified oxygen-based dense layer (SiOx). (c) 2007 The Electrochemical Society.