MoS for Enhanced Electrical Performance of Ultrathin Copper Films

Copper nanowires are widely used as on-chip interconnects due to their superior conductivity. However, with aggressive Cu interconnect scaling, surface scattering of electrons drastically increases the electrical resistivity. In this work, we have studied the electrical performance of Cu thin films deposited on different materials. By comparing the thickness dependence of Cu films' resistivity on MoS and SiO, we have demonstrated that MoS can be used to enhance the electrical performance of ultrathin Cu films due to improved specular surface scattering by up to 40%. By fitting the experimental data with the theoretical Fuchs-Sondheimer (FS) model, we have determined the specularity parameter at the Cu/MoS interface to be ≈ 0.4 at room temperature. Furthermore, first principle calculations based on density functional theory (DFT) indicate that the localized density of states (LDOS) at the Cu/amorphous SiO interface is larger than the LDOS at the Cu/MoS interface, which is believed to be responsible for the higher resistivity in the Cu thin films that are deposited on SiO substrates. Our results suggest that MoS may serve as a performance enhancer for future generations of Cu interconnects.