Total reflection x-ray fluorescence spectroscopy using synchrotron radiation for wafer surface trace impurity analysis (invited)

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Abstract
Trace impurity analysis is essential for the development of competitive silicon circuit technologies. Current best methods for chemically identifying and quantifying surface and near-surface impurities include grazing incidence x-ray fluorescence techniques using rotating anode x-ray sources. To date, this method falls short of what is needed for future process generations. However, the work described here demonstrates that with the use of synchrotron radiation, total reflection x-ray fluorescence methods can be extended to meet projected needs of the silicon circuit industry until, at least, the year 2000. The present results represent over an order of magnitude improvement in detection limit over what has been reported previously. A double multilayer monochromator on a high flux wiggler beam line resulted in a detection limit for Ni of 3×108 atoms/cm2. This is to be compared with a detection limit of 5×109 atoms/cm2 obtained with a rotating anode system. This is due to the greatly improved signal to background in the case of the synchrotron. Furthermore, there is a path to improving the synchrotron case to reach a detection limit of 5×107 atoms/cm2.

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