Kinetics of the ruthenium thin film deposition from supercritical carbon dioxide by the hydrogen reduction of Ru(tmhd)2cod

The kinetics of ruthenium thin film deposition via the hydrogen assisted reduction of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)(1,5-cyclooctadiene)ruthenium(II) [Ru(tmhd)2cod] in supercritical carbon dioxide was studied. Deposition temperature was varied from 240 °C to 280 °C and the apparent activation energy was determined to be 45.3 kJ/mol. Deposition rates up to 30 nm/min were attained. The growth rate dependence on precursor concentration between 0 and 0.2 wt.% in CO2 was studied at 260 °C using excess hydrogen. The results indicated first order deposition kinetics with respect to precursor at concentrations lower than 0.06 wt.% and zero order dependence at concentrations above 0.06 wt.%. The ability to access regimes of zero order growth kinetics is advantageous for conformal depositions in high aspect ratio features. Growth rate was second order with respect to hydrogen at concentrations less than 0.26 wt.% and zero order at higher concentrations. The reaction byproducts, cyclooctadiene and cyclooctene, both had negative first order effects on growth rate while cyclooctane had a small negative impact on film growth rate. The effect of reaction pressure on the growth rate was studied at a constant reaction temperature of 260 °C and pressures between 159 bar and 200 bar and found to have no significant effect on the growth rate.