QUANTIFICATION OF METAL CONTAMINANTS ON GAAS WITH TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRY

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 mat erials, we produced defined submonolayer concentrations of Ca, Mg, Al, Cu, Zn, Si, Ni, Cr, Co, and Fe on the wafer surface by sputter deposi tion from different single-and multielement targets. The concentration s of the elements with m>27 u involved in these calculations were veri fied independently by total reflection x-ray fluorescence spectroscopy . For all ten metals, a linear relation exists between the relative me tal signal Me+/Ga-71(+) and the surface concentration of the metal. By this relation we established TOF-SIMS sensitivity factors for these m etals on UV/ozonized GaAs. The detection limits for almost all element s are in the order of 10(9) atoms/cm(2). (C) 1998 American Vacuum Soci ety.