Conformal ruthenium films are of interest to the microelectronics industry for a number of applications including electrodes for dynamic random access memory (DRAM) and conducting diffusion barrier layers for copper interconnects in integrated circuits. Many processes either require or would benefit from highly conformal and controllable depositions in complex geometries with high aspect ratios. Supercritical fluid deposition (SFD) enables the rapid, efficient and conformal deposition of device quality conformal metal films in high aspect ratio features which is due to high fluid phase precursor concentrations enabled by the supercritical fluid (SCF), which can be orders of magnitude higher then precursor concentrations typical of chemical vapor deposition. The combination of high precursor concentration and favorable transport properties in SCFs allows for this. Here we report that conformal Ru films can be deposited from CO₂. The kinetics of deposition via the hydrogen assisted reduction of bis(2,2,6,6-tetramethyl heptane-3,5-dionato)(1,5-cyclooctadiene) ruthenium, (Ru(tmhd)₂cod) are studied in order to elucidate a reaction rate and reaction mechanism. The activation energy is found to be 45.3 kJ/mol between 513 K – 553 K. The reaction is first order with respect to precursor concentration at low concentrations and zero order at higher concentrations. Growth occurs at apparent 2^nd order with respect to hydrogen concentration and zero order at higher concentrations. In addition, the effect of reaction byproducts on the growth of the film is studied. Both the tetramethyl heptanedionato, TMHD, and cyclooctadiene, COD, ligands have a reaction order of -1 with respect to the growth rate. Cyclooctane, COA, is found to have negligible negative effects on growth rate. Finally, the deposition rate is independent of pressure (CO₂ density) at pressures between 140 bar – 200 bar, indicating that desorption of reaction byproducts is not rate controlling. A reaction mechanism is proposed based on a Langmuir – Hinshelwood kinetic model.

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