Deposition of Ru and RuO2 thin films employing dicarbonyl bis-diketonate ruthenium complexes as CVD source reagents

Abstract

Reaction of Ru3(CO)12 with 6 eq. of β-diketone ligands (hfac)H, (tmhd)H, (acac)H and (tfac)H at 160–170 °C in a hydrocarbon solvent (pentane or hexane) affords the diketonate complexes [Ru(CO)2(hfac)2] (1), [Ru(CO)2(tmhd)2] (2), [Ru(CO)2(acac)2] (3) and [Ru(CO)2(tfac)2] (4) in high yields. These ruthenium complexes were characterized by spectroscopic methods; a single crystal X-ray diffraction study was carried out on one isomer of the tfac complex (4a), revealing an octahedral coordination geometry with two CO ligands located at cis-positions and with the CF3 groups of the β-diketonate ligands trans to the CO ligands. Thermogravimetric analysis of complex (1) showed an enhanced volatility compared to the parent acac complex (3), attributed to the CF3 group reducing intermolecular attraction. Employing complexes (1) and (2) as CVD source reagents, ruthenium thin films can be deposited at temperatures of 350 °C–450 °C under an H2 atmosphere or at temperatures of 275 °C–400 °C using a 2% mixture of O2 in argon as carrier gas. For deposition carried out using complex (1) and under 100% O2 atmosphere, RuO2 thin films with a preferred (200) orientation were obtained. The as-deposited thin films were characterized by surface and physical analytical techniques, such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD) and four-point probe measurement.