Atomic Layer Deposition of Molybdenum Carbide and Substrate-dependent Reduction to Metallic Molybdenum

Abstract

Atomic layer deposition (ALD) is an essential technique for depositing thin films with uniform thickness on 3D nanostructures, and it is actively being investigated for applications in metal interconnects. In this work, we deposited Mo2C thin films using the newly synthesized molybdenum bis(tert-butylimido)(cyclopentadienyl)chloride (MoNICCa) and developed a phase transformation process to convert them into metallic Mo. The MoNICCa precursor enables self-limiting reactions, allowing precise control of film thickness based on the number of cycles, and facilitates the formation of uniform thin films suitable for ALD. Using MoNICCa, metal Mo thin films with over 90 % atomic concentration were successfully obtained through post-deposition annealing. To investigate substrate effects, three types of substrates - Si, TiN/SiO2, and SiO2 - were employed to explore the effect of oxygen interaction between the deposited film and the substrate. Significant differences were observed depending on the substrate, and we found that oxygen in the thin film plays a role in removing carbon from molybdenum carbide. This study proposes MoNICCa as a viable alternative to conventional solid-state Mo precursors and further demonstrates that substrate interactions can be utilized to remove carbon from transition metal carbides.