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

Abstract

Molybdenum nitride (MoN x ), 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 MoN x 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 MoN x films. With increasing H2/N2 ratios, the MoN x films crystallized from the amorphous to the cubic Mo2N phase, and the composition also approximated the stoichiometry of Mo2N (Mo/N approximate to 2). The work function, dominantly affected by the crystal structure, was 4.7-4.8 eV for the cubic Mo2N-phase MoN x films and was higher (5.18 eV) for the amorphous-phase MoN x films. Due to the higher crystallinity and fewer impurities, the resistivity of the MoN x thin films having a higher H2/N2 ratio was lower, and the resistivity-size effect was alleviated. The 10%-MoN x films maintained a low resistivity of 120-170 mu Omega<middle dot>cm even at 4 nm. The diffusion-barrier ability decreased as the H2/N2 ratio increased; however, all MoN x films were stable as a Cu diffusion barrier without deterioration within the thermal budget range of 550 degrees C for the back-end-of-line (BEOL) process. Therefore, MoN x thin films grown by ALD are promising for various nanoscale electronic applications, such as diffusion barriers, interconnects, and metal gates.