Investigation of the Effect of Thermal-Induced Atomic Motion on the Conductance of Copper Thin Films

Abstract: Decrease in the size of integrated circuits (IC) and metal interconnects raise resistivity due the amplification of electron scattering effects, which decreases the efficiency of chiplets. While previous studies have investigated the electron scattering due to a roughened surface, the effect of thermal induced atomic motion on the roughened surface remains unclear. To address this gap, we investigated electron transport in pristine and roughened Cu thin films by performing \textit{ab initio} molecular dynamics (AIMD) trajectories over 20~ps at temperatures of 218~K, 300~K, and 540~K on Cu thin film models, and then calculating the electron transport properties of the resulting snapshots at 100-fs intervals for the last 10~ps using the non-equilibrium Green's function formalism in combination with density functional theory (NEGF-DFT). As expected, higher temperatures induce larger atomic displacement from their equilibrium positions and increase atomic layer separation. We also find that increase in temperature results in increased resistance (lower conductance) for the pristine film, but less so for the roughened thin film where the surface roughness itself is the main source of resistance. This study provides insights into how pristine and roughened Cu thin films behave under thermal conditions, helping researchers design better treatments to mitigate thermal effects in ICs and their metal interconnects.