Abstract
Copper with a high density of nanoscale twins has attracted extensive research attention in the last decade due to its excellent mechanical strength and decent electrical conductivity. Nanotwinned Cu is considered as a candidate of interconnect material in nanoelectronic devices. However, the oxidation behavior of nanotwinned Cu has to be evaluated for process integration considerations. In this study, the oxidation kinetics of Cu films was investigated by in-situ resistivity measurement at different temperatures. In this study, we deposited Cu films on a Si substrate by e-gun evaporation and oxidized Cu films at 200°C in air to observe the oxidation behavior. The different densities of nanotwinned Cu films were deposited by different deposition rate and deposition temperature. Using TEM analysis, the Cu films with high deposition rate had high densities of nanotwinned structure. The observation of oxidation morphology by AFM showed that Cu films with high deposition rate had lower roughness. The XRD analysis revealed that the Cu oxides were found to be Cu2O. Besides, the SEM observation indicated the Cu films with high deposition rate had small and uniformly distributed oxides. The oxidation rate of Cu films was determined by in-situ resistivity measurement at different temperature. It showed that the higher deposition rate had the lower oxidation rate. In addition, when nanotwinned structure was introduced into Cu films, the primary oxidation mechanism would be diffusion control. Therefore, nanotwinned Cu films could reduce oxidation rate effectively.