Abstract:This letter reports the formation of a reacted layer between Cu film and barrierless Si substrate during annealing. The Cu films with a minor WN phase are deposited by reactive cosputtering of Cu and W in an Ar/N2 mixture gas. After annealing at 530 °C for 1 h, a ∼ 200-nm-thick reacted layer formed at the Cu(WN)/Si interface acts as a barrier to protect the film from extensive interactions with Si. X-ray diffraction, focused ion beam, and transmission electron microscopy results confirm the presence of this layer and show this layer is mainly composed of Cu2WO4, Cu3Si, and Si2N2O. Leakage current and resistivity evaluations reveal the superior thermal reliability of Cu with a dilute amount of WN at the temperatures up to 530 °C, suggesting its potential application in the advanced barrierless metallization.