Quantification of metal contaminants on GaAs with time-of-flight secondary ion mass spectrometry

Abstract

We have shown that small concentrations of metal atoms on UV/ozonized GaAs wafer surfaces can be quantitatively determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS). As standard reference materials, we produced defined submonolayer concentrations of Ca, Mg, Al, Cu, Zn, Si, Ni, Cr, Co, and Fe on the wafer surface by sputter deposition from different single- and multielement targets. The concentrations of the elements with m>27 u involved in these calculations were verified independently by total reflection x-ray fluorescence spectroscopy. For all ten metals, a linear relation exists between the relative metal signal Me+/71Ga+ and the surface concentration of the metal. By this relation we established TOF-SIMS sensitivity factors for these metals on UV/ozonized GaAs. The detection limits for almost all elements are in the order of 109 atoms/cm2.