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

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.

Trace element analysis on Si wafer surfaces by TXRF at the ID32 ESRF undulator beamline

“…Therefore SR-TXRF might become an important R&D and process-control tool for semiconductor applications. Detection limits in the 10 fg range for medium-Z elements have been reported by several groups using bending magnets or wigglers at second-generation synchrotron radiation sources (Wobrauschek et al, 1995;Pianetta et al, 1995). A wideenergy band-pass approach based on multilayer monochromators and, in most cases, focusing optical elements has been used in order to increase the photon¯ux onto the sample.…”

Recent advances and perspectives in synchrotron radiation TXRF

“…This facility features clean wafer handling and automated data acquisition making routine analytical measurements possible. The sensitivity that can routinely be achieved for Cu is about 8 E7 atoms/cm 2 for a standard 1000-second count time as determined from Fe, Ni and Zn standards [1,2,3,4]. This is about a factor of 50 better than what can be achieved with conventional laboratory TXRF using a rotating anode.…”

Synchrotron radiation induced TXRF

“…15 The main goal was to optimize the setup for Si wafer surface characterization. LD's of 1 Â 10 8 atoms cm À2 have been achieved using a double ML-monochromator and a Teflon-filter 16,17 to prevent saturation of the detector.…”