Effects of sputtering induced artifacts on the determination of diffusion coefficient: Application to Ni/Cu system

Abstract

The influence of the deformation of the measured depth profile as compared to the originals, on the determination of diffusion coefficient was evaluated in depth profiling. Based on Fick's second law, the original simulation depth profiles were obtained. By application of the mixing-roughness-information depth model, the influences of sputtering induced artifacts on the original depth profiles could be predicted and, as a result, we could investigate the effects of those artifacts on the determination of the diffusion coefficient. Firstly, a numerical simulation was applied to evaluate the effects of those sputtering induced artifacts on the determination of the diffusion coefficient. Subsequently, an experiment was performed to obtain the diffusion coefficient in a Ni–Cu system and the influences of the sputtering induced artifacts on the measured diffusion coefficient were estimated according to the previous simulation results. The simulation results showed that, for roughness less than 10 nm, and mixing length or information depth less than 4 nm, the effects of sputtering induced artifacts on the determination of the diffusion coefficient could be ignored. In addition, Cu(100 nm)/Ni(100 nm)/SiOx/Si(100) thin films were synthesized using electron-beam evaporation and then annealed at different temperatures under vacuum. The samples were characterized by time-of-flight secondary ion mass spectrometry depth profiling. The effects of sputtering induced artifacts on the depth profiles of the Ni/Cu films were very small since the roughness and mixing length are very small. The measured diffusion coefficient agrees well with the results of others.