Effect of the H2/N2 Ratio on Molybdenum Nitride Thin Films Deposited by Plasma-Enhanced Atomic Layer Deposition: Applications for Next-Generation Interconnects

Molybdenum nitride (MoNx), exhibiting low resistivity, diffusion-barrier ability, and high and tunable work function, is a promising next-generation conductive material for nanoscale electronic applications. Herein, atomic layer deposition (ALD) of MoNx thin films was achieved using (MeCp)Mo(CO)2(NO) and H2/N2 plasma, and the effect of the H2/N2 ratio on the properties of the films was confirmed. Regardless of the H2/N2 ratio, uniform and continuous thin films were deposited within the first few cycles without an incubation period. Varying the H2/N2 ratio of the reactant affected the composition and crystallinity of the MoNx films. With increasing H2/N2 ratios, the MoNx films crystallized from the amorphous to the cubic Mo2N phase, and the composition also approximated the stoichiometry of Mo2N (Mo/N ≈ 2). The work function, dominantly affected by the crystal structure, was 4.7–4.8 eV for the cubic Mo2N-phase MoNx films and was higher (5.18 eV) for the amorphous-phase MoNx films. Due to the higher crystallinity and fewer impurities, the resistivity of the MoNx thin films having a higher H2/N2 ratio was lower, and the resistivity–size effect was alleviated. The 10%-MoNx films maintained a low resistivity of 120–170 μΩ·cm even at 4 nm. The diffusion-barrier ability decreased as the H2/N2 ratio increased; however, all MoNx films were stable as a Cu diffusion barrier without deterioration within the thermal budget range of 550 °C for the back-end-of-line (BEOL) process. Therefore, MoNx thin films grown by ALD are promising for various nanoscale electronic applications, such as diffusion barriers, interconnects, and metal gates.