Atomic layer deposition of TaN and Ta3N5 using pentakis(dimethylamino)tantalum and either ammonia or monomethylhydrazine

TaNx thin films were grown at temperatures ranging from 200 to 375 °C using atomic layer deposition (ALD). Pentakis(dimethylamino)tantalum (PDMAT) was used as a tantalum source with either ammonia or monomethylhydrazine (MMH) as a nitrogen co-reactant. Self-limiting behaviour was observed for both ammonia and MMH processes, with growth rates of 0.6 and 0.4 Å/cycle, respectively at 300 °C. Films deposited using ammonia were found to have a mono-nitride stoichiometry with resistivities as low as 70 mΩ cm. In contrast, films deposited using MMH were found to be nitrogen rich Ta3N5 with high resistivities. A Quartz Crystal Microbalance (QCM) was used to measure mass gain and loss during the cyclic ALD processes and the data was used in combination with medium energy ion scattering (MEIS) to elucidate the PDMAT absorption mechanisms.

► Thermal atomic layer deposition was used to deposit conductive TaN and semi-insulating Ta3N5. ► Growth conditions have been optimised. ► Films display undetectable oxygen and carbon incorporation. ► Films exhibit the lowest resistivity value reported using thermal ALD. ► In-situ quartz crystal microbalance measurements were employed to elucidate the chemisorption mechanism during the cyclic process.