AUGER-ELECTRON SPECTROSCOPY AND SECONDARY ION MASS-SPECTROMETRY DEPTH PROFILING WITH SAMPLE ROTATION

Recently, there has been a rapid increase in the application of multilayered structured materials, as opposed to bulk materials, in many areas of technological development. Accurate characterization of the structure and composition of advanced multilayers such as superlattices, quantum wells, contacts, and coatings is important for materials and device fabrication technology. Surface analysis techniques including Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy, and secondary ion mass spectrometry (SIMS) in conjunction with ion beam sputtering (sputter depth profiling) are at present the most widely used methods for characterization of modern multilayer thin film materials and devices. Ion-beam-induced surface topography, however, can limit depth resolution, and with SIMS, can also cause changes in the secondary ion yield. These changes are due to the high sensitivity of secondary ion yield to the local angle of incidence on sputter-roughened surfaces. Degradation of depth resolution and changes in secondary ion yields during sputter depth profiling have often limited studies of thin film interdiffusion, segregation, oxidation at interfaces, and impurity effects. Much theoretical and experimental work has been carried out to try to improve depth resolution including the use of low ion beam energy, high angle of incidence, and two ion guns. Recent studies of AES and SIMS with sample rotation have shown that depth resolution can be improved substantially and that constant secondary ion yields in SIMS can be achieved. We will first provide an overview of the studies made by various groups to improve depth resolution of metal multilayers using AES with rotation. Next we will review recent investigations of SIMS using sample rotation including studies of the effects of sample rotation on O2+ ion-beam-induced topography, secondary ion yield, and the depth resolution of electronic, metallurgical and dielectric materials. The results presented demonstrate that SIMS with sample rotation provides constant secondary ion yield, and depth-independent depth resolution because sample rotation prevents ion-beam-induced roughness and reduces the effect of the inhomogeneity of low energy ion beams.