Abstract
Ta-N thin films were deposited on the n type Si(100) substrate by reactive sputtering for potential application of the diffusion barrier layers in Ultra-large-scale integration (ULSI). Barrier films performance is affected by various deposited parameters in the sputtering system, including flow rate of reactive gas, working distance and RF power density. The electrical resistivity of the tantalum nitride films increases with incorporated nitrogen atoms and gradually rises to around 500 □□-cm as the nitrogen in the film increases to 50%. When the concentration of nitrogen is beyond 50 at%, the resistivity rises rather sharply. X-ray diffraction analysis demonstrates that the microstructure of the as-deposited Ta2N film exhibits amorphous or nanocrystal. Besides, the cross-sectional view of SEM image of as-deposited Ta2N film also reveals amorphous or nanocrystal structure. The microstructure of the as-deposited Ta and TaN shows a column structure. Five assemblies of Cu/Ta/Si, Cu/Ta2N/Si, Cu/Ta2N/SiO2, Cu/TaN/Si and Cu/TaN/SiO2 were annealed in the temperature range 500-800oC. Several characterization methods were employed to evaluate the capability Ta-N related systems of the diffusion barrier. All the results indicate that Ta2N acts as a better candidate of the diffusion barrier material than others to resist the diffusion of copper. In addition, the presence of Diffusion barrier layers also influences the preferred-orientation of copper interconnection. Among the underlying layers introduced in this study, Ta2N films tend to enhance the preferred-orientation of Cu(111) better than Ta and TaN films.