Study of Ta–Si–N thin films for use as barrier layer in copper metallizations

This work focuses on the deposition process, microanalytical characterization and barrier behaviour of 10–100-nm thick sputtered Ta–Si and Ta–Si–N films. Pure Ta–Si films were found to be already nanocrystalline. The addition of N 2 leads to a further grain fining resulting in amorphous films with excellent thermal stability. According to microanalytical investigations, Ta–Si barriers between Cu and Si with a thickness of only 10 nm are not stable at 600°C. Copper silicides are formed due to intensive Cu diffusion throughout the barrier. In contrast, 10-nm thick nitrogen-rich Ta–Si–N barriers remain thermally stable during annealing at 600°C and protect the Si wafer from Cu indiffusion.