Paper AS+BI+MI+NS+SA+SS-WeM12
Evaluating the Benefits of Cs Cluster Analysis in ToF-SIMS and Cs/Xe Co-sputtering for Depth Profiling Layered Thin Films

Wednesday, November 1, 2017, 11:40 am, Room 13

Depth profiling with Cs to create MCs⁺ clusters can produce semi-quantitative results by greatly reducing the matrix effects observed in common M⁺ analysis. Additionally, alkali metal clusters enhance negative ion detection in the form of positive Cs clusters, such as MCs⁺ and MCs₂⁺. In his review article, Wittmaack¹ discussed the many ways that Cs is used in SIMS analyses to provide this enhancement which includes using Cs as the sputtering species and/or analytical probe and using directed Cs vapor. Unfortunately, high Cs surface concentrations can lead to suppression of Cs cluster formation. Xenon and Cs can be co-sputtered in a ToF-SIMS system to adjust the relative amounts of Cs and Xe in the co-sputtered beam to control Cs surface concentration and optimize Cs cluster formation². Cs/Xe co-sputtered depth profiling has been shown to work well in materials systems such as Au thin film on Si³ and Pd-Rh thin film⁴.

The present paper discusses the use of Cs/Xe co-sputtering to investigate an Au/Pd/Ni electroplated layered system. Gold and to some extent Pd have low positive ionization yields, so typical ToF-SIMS data from these metals can be difficult to interpret. However, Cs/Xe co-sputtering has been found to generate high yield MCs⁺ clusters in Au and Pd, thus enabling this analysis. This Au/Pd/Ni metal stack were analyzed in a pristine (as received) condition, after accelerated aging and after exposure to a (very high temperature) solder reflow process. The elemental and molecular sensitivities as well as quantitative results stemming from this analysis will be investigated. The manner whereby these results support the use of Au/Pd/Ni stack in an engineering application will be shown. In particular, interlayer diffusion, trace contaminants and interfacial contamination will be examined. Comparisons will be made to Auger and XRF to assess quantitation and sensitivity and to illustrate the advantage of this SIMS technique.

1) K. Wittmaack, Surface Science Reports, 68 (2013) 108-230.

2) E. Niehus, T. Grehl, in: J.C. Vickerman, D. Briggs (Eds.), ToF-SIMS, IMPublications, Chichester, West Sussex, UK, 2001, p. 753.

3) J. Brison and L. Houssiau, Surf. Interface Anal. 2006; 38: 1715-1719.

4) J. Brison, R. Hubert, S. Lucas and L. Houssiau, Surf. Interface Anal. 2006; 38: 1654-1657.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.