Application of ETV-ICPMS in semiconductor process control

Submicron semiconductor manufacturing requires ultra-clean processes and materials to achieve high product yields. It is demonstrated that electrothermal evaporation (ETV) in a graphite furnace coupled with ICPMS offers a new possibility for a fast simultaneous analysis of eight elements with detection limits below 0.2 ng/g in conc. hydrofluoric acid and buffered oxide etch (ammonium fluoride/hydrogen fluoride mixture). ETV-ICPMS also comprises significant improvements in the analysis of metal contamination on silicon wafer surfaces with respect to currently used methods. The contaminants on the surface are usually analyzed by total reflexion X-ray fluorescence spectrometry (TXRF) or dissolved by HF vapour (vapour phase decomposition; VPD) or a mixture of hydrofluoric acid and hydrogen peroxide (droplet surface etching, DSE) and analyzed by GFAA or TXRF. ETV-ICPMS combines the advantages of both analytical methods: the multielemental advantage of TXRF and the possibility to analyze light elements like Al, Mg, Na which may not be analyzed by TXRF. With VPD/DSE-ETV-ICPMS detection limits between 0.2 and 2×10⁹ atoms cm^?2 on a 6″ wafer have been achieved in a simultaneous analysis of eight elements. The main advantage of ETV-ICPMS versus conventional ICPMS in both applications — chemical and surface analysis — is its capability to analyze Fe in the sub-ng/g range. As Fe is one of the most important impurities in semiconductor manufacturing ETV-ICPMS is much more useful for semiconductor applications than low-resolution ICPMS. For the present application potassium iodide was used as a modifier. It enhances the sensitivity by a factor of 3–4 and improves the reproducibility significantly.