Towards femtosecond laser ablation ionization mass spectrometric approaches for chemical depth-profiling analysis of lead-free Sn solder bumps with minimized side-wall contributions

Abstract

Sn solder bumps on Cu pillars and the quantification of incorporated organic impurities are of urgent interest to the microchip industry. In this report, the fundamentals of laser–matter interaction using femtosecond laser ablation ionization mass spectrometry (fs-LIMS) are described, including studies on the ablation rate of a dual layer system Sn/Cu as well as on three different laser ablation approaches that (i) address the highly different material properties of Sn and Cu and (ii) allow for a significant reduction of side-wall contributions, which is a crucial prerequisite for chemical depth profiling.