Comparison of Tantalum Nitride Films for Different NH3/H-2/Ar Reactant States in Two-Step Atomic Layer Deposition

Abstract

A two-step atomic layer deposition (ALD) process, applying either thermal or plasma assited Ta nitridation with a NH3/H-2/Ar gas mixture was conducted to discern the formation conditions of the cubic-TaN phase versus those of the Ta3N5 phase at an extremly low deposition, temperature of 200 degrees C. Metallic cubic-TaN films with an electrical resistivity of 400 mu Omega cm were successfully grown by thermal nitridation at 200 degrees 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 mu Omega cm. The relative concentration of cubic TaN and Ta3N5 phase was precisely controlled by changes in the nitridation time and the NH3 flow rate during the plasma-assisted nitridation process. (C) 2009 The Japan Society of Applied Physics