Self-Catalyzed, Low-Temperature Atomic Layer Deposition of Ruthenium Metal Using Zero-Valent Ru(DMBD)(CO)₃ and Water

Ruthenium (Ru) films are deposited using atomic layer deposition (ALD), promoted by a self-catalytic reaction mechanism. Using zero-valent, η4-2,3-dimethylbutadiene Ruthenium tricarbonyl (Ru(DMBD)(CO)3) and H2O, Ru films are deposited at a rate of 0.1 nm/cycle. The temperature for steady deposition lies between 160 and 210 °C. Film structure and composition are confirmed via X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The room-temperature electrical resistivity of 10 nm Ru films is found to be 39 μΩ·cm. In situ quadrupole mass spectrometry and density functional theory are used to understand ALD surface reactions. The ligand, dimethylbutadiene dissociatively desorbs on the surface. On the other hand, the carbonyl ligand is catalyzed by the Ru center. This leads to the water gas shift reaction, forming CO2 and H2. Modulating deposition temperature affects these two ligand dissociation reactions. This in turn affects nucleation, growth, and hence, Ru film properties. Self-catalyzed reactions provide a pathway for low-temperature ALD with milder co-reactants.