Abstract: One of the urgent research topics in Cu interconnection for ULSI is to fabricate suitable barrier to prevent Cu diffusion.In this paper,Ta-N thin-films were fabricated by DC magnetron reactive sputtering in N₂/Ar ambient with different N₂ flow ratio,then Cu/Ta-N/substrate multi-structures were prepared without broken the vacuum,some specimens were rapid thermally treated（RTA） in N₂ ambient.Alpha-Step IQ Profiler,four-point probe sheet resistance measurer,atomic force microscope（AFM）,scanning electron microscope（SEM） and X-ray diffraction（XRD） were used to characterize the surface morphology and structure of the specimens.The research indicates that with the N₂ flow ratio increasing,the deposition rate decreases,the surface tends to become smooth and the thermal stability and diffusion barrier property are improved,while the sheet resistance increases.Ta-N barrier（100nm thickness）can effectively against Cu diffusion after 600℃ annealing for 5 minutes with the N₂ flow ratio of 0.3,Cu can diffuse through the barrier and react with Si after annealing at higher temperature.