Reactive Deposition of Conformal Ruthenium Films from Supercritical Carbon Dioxide

High-purity Ru films were deposited from supercritical carbon dioxide onto the native oxide of Si wafers and onto Ta films supported on Si wafers using a batch, cold wall deposition reactor. Ru(0) and Ru(II) precursors were effective at substrate temperatures between 175 and 300 °C and pressures between 20 and 25 MPa. Hydrogen-assisted deposition of Ru from triruthenium dodecacarbonyl (Ru 3 (CO) 12 ), tris(2,2,6,6-tetramethyl-heptane-3,5-dionato)ruthenium (Ru(tmhd) 3 ), and bis(2,2,6,6-tetramethyl heptane-3,5-dionato)(1,5-cyclooctadiene)ruthenium (Ru(tmhd) 2 cod) proceeded readily to yield highly reflective thin films with resistivities as low as 22 μΩ-cm for a 33 nm thick film. H 2 -assisted depositions using ruthenocene were not successful on oxide surfaces at temperatures up to 300 °C, but proceeded readily on Au. Thermal depositions from (Ru 3 (CO) 12 ) yielded reflective, but highly resistive, films. Excellent step coverage of high-purity films was achieved within 200 nm × 300 nm trenches on patterned tantalum-coated surfaces and within 2 μm × 30 μm and 300 nm × 1.2 μm via structures on etched silicon wafers by H 2 -assisted deposition using Ru 3 (CO) 12 and Ru(tmhd) 2 cod, respectively. Analysis by X-ray diffraction and X-ray photoelectron spectroscopy indicated that the films were polycrystalline and free of oxygen contamination.