Ta₂O₅/SiO₂ multilayered thin film on Si as a proposed new reference material for SIMS depth profiling

A delta oxide multilayered thin film is proposed as a new reference material for SIMS depth profiling. This material is composed of seven thick Ta₂O₅ layers of 18 nm separated by 1 nm SiO₂ delta layers. The surface of the thin film was very flat and all the interfaces were sharp according to atomic force microscopy (AFM) and transmission electron microscopy (TEM). In SIMS depth profiling, the dynamic range of the Si⁺ ion signal at the SiO₂ layer was large enough to define the depth resolution. The surface topographic development after ion beam sputtering was negligible under various sputtering conditions, as observed by AFM. This was well correlated with the result that there is no significant deterioration of SIMS interface resolution with sputter depth. This reference material can be useful in SIMS depth profiling analysis to optimize the experimental parameters for a better depth resolution and to calibrate the sputtering rate.