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

Reaction of Ru-3(CO)(12) with 6 eq. of beta-diketone ligands (hfac) H, (tmhd) H, (acac) H and (tfac) H at 160 - 170 degreesC 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 beta-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 degreesC - 450 degreesC under an H-2 atmosphere or at temperatures of 275 degreesC - 400 degreesC using a 2% mixture of O-2 in argon as carrier gas. For deposition carried out using complex ( 1) and under 100% O-2 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.