Atomic Layer Deposited Highly Conductive Niobium Carbide Thin Films as Next-Generation Diffusion Barriers for Cu and Ru Interconnects

Abstract

Achieving precise thickness control and producing noncorrosive byproducts are critical for developing effective semiconductor diffusion barrier. Although atomic layer deposition (ALD) is widely employed for conformal thin films, its application to niobium carbide (NbC) remains underexplored. This study presents the plasma-enhanced ALD (PEALD) of highly conductive NbCx films using a novel metal-organic Nb precursor and H-2 plasma. By optimizing deposition conditions, oxygen incorporation was minimized (similar to 5 at.%), which strengthened Nb-C bonding and lowered resistivity to below 100 mu Omega-cm. Density functional theory (DFT) calculations confirmed that residual O-2 and H2O promote oxygen incorporation, whereas increased plasma power and temperature facilitate Nb-O bond dissociation and generate carbon sources, resulting in carbon-rich, highly conductive NbCx films. Finally, the ultrathin NbCx (2.6 nm) film functioned as both a diffusion barrier and adhesion layer, suppressing Cu diffusion up to 500 degrees C and Ru diffusion up to 900 degrees C, and concurrently enhancing interfacial adhesion in both Cu and Ru metallization.