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FEASIBILITY OF IN SITU TXRF

Synchrotron radiation based total external reflection x-ray fluorescence spectroscopy (TXRF) is now being routinely used at the Stanford Synchr otron Radiation Laboratory (SSRL) to carry out industrially relevant measurements. For transition elements on Si wafer surfaces, detection limits of 8x10 7 atoms/cm 2 that correspond to 1 impurity atom among 30 million substrate atoms have proven more than adequate for the studies undertaken to date. New studies, which aim to develop a better understanding of the kinetics of metal deposition during Si wafer cleaning processes, are being pursued. By using a sample cell with a water delivery system that has been custom designed, silicon samples can be analyzed directly beneath a water layer (in situ TXRF). Initial results measuring silicon samples with known Cu concentrations are presented. Due to the increased scatter and background from the water layer along with the attenuation of fluorescence signals, minimum detection limits for the in situ TXRF setup increased to 8x10 10 atoms/cm 2 , in close agreement to predicted values extracted from modeling calculations.