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MoS2 for Enhanced Electrical Performance of Ultrathin Copper Films
journal contribution
posted on 2019-07-22, 17:33 authored by Tingting Shen, Daniel Valencia, Qingxiao Wang, Kuang-Chung Wang, Michael Povolotskyi, Moon J. Kim, Gerhard Klimeck, Zhihong Chen, Joerg AppenzellerCopper 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 ≈ 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.