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

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 NbC<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> films using a novel metal-organic Nb precursor and H₂ plasma. By optimizing deposition conditions, oxygen incorporation was minimized (~5 at.%), which strengthened Nb– C bonding and lowered resistivity to below 100 μΩ-cm. Density functional theory (DFT) calculations confirmed that residual O₂ 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 NbC<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> films. Finally, the ultrathin NbC<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> (2.6 nm) film functioned as both a diffusion barrier and adhesion layer, suppressing Cu diffusion up to 500 °C and Ru diffusion up to 900 °C, and concurrently enhancing interfacial adhesion in both Cu and Ru metallization.