Ultra trace analysis and electrical characterization of Cu diffusion through thin quasi-amorphous Ta-N-O barriers

Besides the advantages of Cu-based metallization systems, like lower electrical resistivity and higher electromigration resistance, they have one major drawback-Cu is a fast diffuser into Si and SiO
₂
. Hence, a diffusion or drift barrier is necessary between Cu and Si or SiO
₂
respectively, in order to prevent deterioration of the devices. Many refractory metals and their compounds have been studied, with Ta-based diffusion barriers being among the most promising. Unfortunately, most of these barriers are polycrystalline and provide inadequate protection because they contain grain boundaries that may serve as active diffusion paths for Cu. Depositing an amorphous-like film even very thin (<50 nm) barriers can be used without any danger for the integrity of future ULSI devices. This work focuses on the microanalytical and electrical characterization of 5 to 50 nm thin quasi-amorphous Ta-N-O diffusion barriers in the Cu/Si contact system.