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 behavior 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 sub 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 deg 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 deg C and protect the Si wafer from Cu indiffusion.