Low Temperature Two-Step Atomic Layer Deposition of Tantalum Nitride for Cu Diffusion Barrier

Abstract

A cubic delta-TaN thin film with an electrical resistivity of 400 mu Omega cm was successfully obtained by suppressing the formation of Ta(3)N(5) using two-step atomic layer deposition independent of NH(3) dosage. The deposition cycle involved two chemical reaction steps: The formation of elemental tantalum (Ta) by reducing tantalum pentafluoride (TaF(5)) with hydrogen plasma and the subsequent nitridation of the preformed Ta with NH(3) at 200-350 degrees C. The microstructure of the preformed Ta was beta-Ta phase with an electrical resistivity of 220 mu Omega cm, which was formed without regard to the deposition temperature. At a deposition temperature of less than 250 degrees C, cubic delta-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 degrees C, the resistivity of Ta-N-based thin film increased abruptly as the NH(3) dosage exceeded 16.08 x 10(19) molecules/cm(3) due to the formation of Ta(3)N(5). (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3223989] All rights reserved.