MoS2 for Enhanced Electrical Performance of Ultrathin Copper Films
TT Shen and D Valencia and QX Wang and KC Wang and M Povolotskyi and MJ Kim and G Klimeck and ZH Chen and J Appenzeller, ACS APPLIED MATERIALS & INTERFACES, 11, 28345-28351 (2019).
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 MoS2 and SiO2, we have demonstrated that MoS2 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/MoS2 interface to be p approximate to 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 SiO2 interface is larger than the LDOS at the Cu/MoS2 interface, which is believed to be responsible for the higher resistivity in the Cu thin films that are deposited on SiO2 substrates. Our results suggest that MoS2 may serve as a performance enhancer for future generations of Cu interconnects.
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