MoN _<i>x</i> Nanoscale-Thick Films Using BTBMMo and Ammonia in Plasma-Enhanced ALD for Cu Diffusion Barriers in High-Aspect-Ratio Nanohole 3D Interconnects

As 3D interconnects continue to scale down, atomic layer deposition (ALD) has emerged as a key technique for depositing ultrathin films with excellent conformality and precise thickness control, playing an increasingly critical role in ensuring device reliability and performance in advanced integration schemes. In this study, we developed a plasma-enhanced atomic layer deposition (PEALD) process for nanoscale molybdenum nitride (MoNx) thin films using a precursor combination of bis(tert-butylimido)bis(dimethylamido)molybdenum and ammonia plasma. This combination enabled a higher growth rate and a wider ALD temperature window at lower temperatures compared to previously studied Mo precursors, yielding MoNx films with atomically smooth surfaces, nearly stoichiometric composition, and a very low carbon impurity concentration. Finally, we demonstrated that the MoNx films grown by this process function as effective Cu diffusion barriers at ∼10 nm thickness, particularly suitable for nanoscale 3D device architectures, as evidenced by excellent conformality and structural integrity within high-aspect-ratio nanohole structures and thermal stability up to 600 °C.