Theoretical study of point defects on transport properties in metallic interconnections

During the line width reduction, electron scattering caused by various defects in metal interconnects increases dramatically, which causes leakage or short circuit problems in the device, reducing device performance and reliability. Point defects are one of the important factors. Here, using density functional theory and non-equilibrium Green's function methods, we systematically study the effects of point defects on the transport properties of metals Al, Cu, Ag, Ir, Rh, and Ru, namely vacancy defects and interstitial doping of C atom. The results show that the conductivity of all systems decreases compared to perfect systems, because defects cause unnecessary electron scattering. Since the orbital hybridization of the C atom with the Al, Cu and Ag atoms is stronger than that metals Ir, Rh and Ru, the doping of C atom significantly reduces the conductivity of metals Al, Cu and Ag compared to vacancy defects. In contrast, vacancy defects have a greater impact than doping on the transport properties of metals Ir, Rh and Ru, which is mainly attributed to the larger charge transfer of the host atoms around the vacancies caused by lattice distortion. In addition, metal Rh exhibits excellent conductivity in all systems. Therefore, in order to optimize the transport properties of interconnect metals, our work points out that the doping of impurity atoms should be avoided for metals Al, Cu and Ag, while the presence of vacancy defects should be avoided for metals Ir, Rh and Ru, and Rh may be an excellent candidate material for future metal interconnects.