Significant improvement in depth resolution of Cr/Ni interfaces by secondary ion mass spectrometry profiling under normal O₂⁺ ion bombardment

Depth resolution in secondary ion mass spectrometry profiling of Cr/Ni multilayered thin films was studied as a function of ion beam incidence angle. As the incidence angle from the surface normal increased from 30°to 80°, the depth resolution improved as generally observed. However, between incidence angles of 20°and 30°, the depth profiling resolution improved abruptly and significantly. The best depth resolution of about 6 nm was obtained for normal incident O₂⁺ ion beams for all the Cr/Ni interfaces of depth down to 500 nm. It was found that the observed variation of depth resolution was very well related to the surface topographic development, which was very sensitive to the incidence angle of the ion beam.