Abstract Controlling and preventing Cu oxidation is crucial for improving the performance and reliability of Cu–Cu bonding. Ni-B films were selectively deposited on Cu films to block the Cu oxidation. The resistivity changes of the Cu films in N₂ and O₂ ambient were measured by using a four-point probe in the in situ temperature-dependent resistance measurements at the temperature from room temperature to 400 °C. The resistivity changes of the 100 nm thick Cu films without Ni-B increased rapidly at a higher temperature (284 °C) in the O₂ ambiance. The change of resistivity-increase of 100 nm thick Cu with ∼50 nm thick Ni-B (top) film was lower than the Cu films without Ni-B films due to the blocking diffusion of O₂ atoms by the Ni-B films. The resistivity-change and oxidation barrier properties were studied using scanning electron microscopy, FIB, transmission electron microscopy, EDX, and secondary ion mass spectroscopy tools. The proposed article will be helpful for the upcoming advancement in Cu–Cu bonding using selected-area deposition.