Growth of conformal TiN thin film with low resistivity and impurity via hollow cathode plasma atomic layer deposition

Copper has been used as an interconnect material in integrated semiconductor devices because of its excellent conductivity, mechanical strength, and electromigration resistance. Introducing a diffusion barrier layer using transition metals such as Ti, Ta, W, Mo, and their nitrides can effectively prevent copper diffusion into the transistor region. TiN is widely used as the diffusion barrier. Plasma-enhanced atomic layer deposition (PEALD), which uses plasma to activate molecular reactions, can be used to fabricate high-quality thin films at lower temperatures than thermal atomic layer deposition. However, its high electrical resistivity and poor step coverage are disadvantageous for its adoption in highly scaled three-dimensional structures. In this study, TiN thin films were fabricated using PEALD with a hollow cathode plasma (HCP) source. The fabricated TiN exhibited a high density (5.29 g/cm³), which was very close to the theoretical density of TiN. Moreover, it has low electrical resistivity (132 μΩ cm) and excellent step coverage (>98%) in a trench pattern with a high aspect ratio of 32:1. These results suggest the possible application of the PEALD of TiN films using HCP sources in semiconductor device manufacturing.