Reactive deposition of cobalt using bis(2,2,6,6-tetramethyl-3,5-heptanedionato) cobalt(II) from supercritical carbon dioxide

Cobalt depositions from supercritical carbon dioxide (scCO₂) were conducted on various surfaces including the native oxide surface of silicon wafers, tantalum nitride (TaN), carbon, and copper in a cold-wall reactor using bis(2,2,6,6-tetramethyl-3,5-heptanedionato) cobalt(II) as the precursor. Deposition onto TaN barrier layers at temperature above 300°C yielded high purity cobalt films as determined by X-ray photoelectron spectroscopy with grain sizes of 200 nm or less. The volume resistivities, of about 200 nm thick films estimated from the surface resistivities, were about 2.5 times higher than that of the literature value of pure cobalt. Cobalt films could also be deposited on both carbon and copper surfaces with morphologies that varied depending on the amount of precursor loaded. Moreover, the cobalt film protected copper surface from oxidation in solution and also improved its resistance to oxidation in air as demonstrated respectively by cyclic voltammetry and X-ray photoelectron spectroscopy depth profiles.