Comparison of Tantalum Nitride Films for Different NH3/H2/Ar Reactant States in Two-Step Atomic Layer Deposition

Abstract

A two-step atomic layer deposition (ALD) process, applying either thermal or plasma-assisted Ta nitridation with a NH3/H2/Ar gas mixture, was conducted to discern the formation conditions of the cubic-TaN phase versus those of the Ta3N5 phase at an extremely low deposition temperature of 200 °C. Metallic cubic-TaN films with an electrical resistivity of 400 µΩ cm were successfully grown by thermal nitridation at 200 °C, while the incorporation of the Ta3N5 phase in TaN films could not be suppressed in the plasma nitridation process owing to large amounts of reactive radicals inherent to plasma nitridation. The dielectric Ta3N5 phase led to a significant increase in electrical resistivity, up to approximately 2500 µΩ cm. The relative concentration of cubic TaN and Ta3N5 phases was precisely controlled by changes in the nitridation time and the NH3 flow rate during the plasma-assisted nitridation process.