Low temperature ALD of Rutheium using H2O as co-reactant

For those of you who were not surprised when Helsinki University published their Ru ALD processing using air as co-reactant please behold - Ruthenium ALD using H2O as co-reactant!

Self-catalyzed, Low-temperature Atomic Layer Deposition of Ruthenium Metal Using Zero-valent, Ru(DMBD)(CO)3 and Water

 
Zhengning Gao, Duy Le, Asim Khaniya, Charles L. Dezelah, Jacob Woodruff, Ravindra K. Kanjolia, William E Kaden, Talat S. Rahman, and Parag Banerjee
Chem. Mater., Just Accepted Manuscript
DOI: 10.1021/acs.chemmater.8b04456

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 the rate of 0.1 nm/cycle. The temperature for steady deposition lies between 160 ○C and 210 ○C. Film structure and composition is 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 ab initio 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.