Abstract: The Cu thin films were deposited on P-Si（100） substrates by magnetron sputtering at room temperature.The interface reaction and diffusion of Cu/SiO₂/Si（100） systems were studied at different temperatures by X-ray diffraction（XRD） and Rutherford backscattering（RBS）.The results showed that onset temperature of interdiffusion was 350 ℃ for the Cu/SiO₂/Si（100） systems.With the increase of temperature,the interdiffusion was more apparent.There were no copper silicides formed at annealing temperature of 450 ℃ for the Cu/SiO₂/Si（100） systemms.The onset temperature of silicification was 500 ℃,which was lower than that of other literatures reported.