Ultralow Resistivity of Copper Nanofilms Enhanced by Cubic Boron Nitride Coherent Interface

The continuous miniaturization of microelectronic interconnects is encountering fundamental limitations due to the increasing resistance-capacitance delay and reliability degradation. Here, we synthesized epitaxial copper/cubic boron nitride (Cu/c-BN) nanofilms with coherent interface. The results demonstrated that the c-BN exhibited exceptional potential in reducing the electrical resistivity of Cu interconnects while enhancing their stability. Owing to the coherent interface and low interfacial electron density of states in Cu/c-BN, c-BN can optimize surface electron scattering in Cu films. Cu/c-BN interfaces display low surface electron scattering, with an exceptionally high surface electron scattering coefficient of 0.67. At a thickness of 2.5 nm, the resistivity of Cu/c-BN is reduced by ∼32.7%, compared to the traditional Cu/barrier multilayers (e.g., Cu/TaN). In addition, due to the high bonding strength and stability, c-BN exhibited high diffusion activation energy (1.39 eV) at 2.5 nm, suggesting its potential as a promising diffusional barrier candidate for sub-3 nm microelectronic interconnection applications.