First-principles evaluation of Janus TiMC MXenes as Cu interconnect barrier layers.

With the continuous reduction of the Cu interconnect critical dimension (CD) and the rise in interconnect resistance, the traditional TaN diffusion barrier faces severe challenges in the scaling-down process, and developing new materials as replacements is of vital importance. In this work, we systematically studied the structural stabilities and electronic properties of two-dimensional Janus MXenes (TiMC, M represents transition metals) as diffusion barrier layers based on first-principles calculations. Phonon dispersion and ab initio molecular dynamics (AIMD) simulations confirm the kinetic and thermal stability of most TiMC structures at 300 K. Electronic property analyses reveal a metallic character with strong anisotropy in conductivity induced by the breaking of symmetry along the out-of-plane direction. The Cu-TiMC-Cu models are built to evaluate the transport properties of electrons within the Cu interconnect structure and can exhibit a maximum current of 54.72 µA at a 0.5 V bias, exceeding that of Cu-TaN-Cu. In the TiMC-Cu electrode structure, a maximum current of 49.26 µA can be reached at a 0.5 V bias, exceeding that of Cu-TaN. These findings indicate that by composing proper Janus structures, MXenes can outperform the traditional TaN barrier in electronic transport, which provides a theoretical basis for the design of low-resistance interconnect structures.