Low temperature two-step atomic layer deposition of tantalum nitride for cu diffusion barrier

A cubic δ-TaN thin film with an electrical resistivity of 400 μΩ cm was successfully obtained by suppressing the formation of Ta ₃N₅ using two-step atomic layer deposition independent of NH₃ dosage. The deposition cycle involved two chemical reaction steps: The formation of elemental tantalum (Ta) by reducing tantalum pentafluoride (TaF₅) with hydrogen plasma and the subsequent nitridation of the preformed Ta with NH₃ at 200-350°C. The microstructure of the preformed Ta was Β-Ta phase with an electrical resistivity of 220 μΩ cm, which was formed without regard to the deposition temperature. At a deposition temperature of less than 250°C, cubic δ-TaN with a Ta/N ratio of 1 was achieved independent of the NH ₃ dosage. However, at a deposition temperature of greater than 300°C, the resistivity of Ta-N-based thin film increased abruptly as the NH₃ dosage exceeded 16.08× 10¹⁹ molecules/ cm ³ due to the formation of Ta₃N₅.