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This work describes recent progress in implementation and applications of synchrotron radiation total reflection x-ray fluorescence (SR-TXRF) to measure trace metals on wafer surfaces. To date, we have achieved state-of-the-art transition metal sensitivity of 3×108 atoms/cm2 (˜3fg) for 1000 sec. counting time for impurities which have an monolayer-like distribution on the surface and <1fg for droplet-like impurities. Recent instrumentation breakthroughs include reduction of detector parasitic backgrounds (particularly Cu) to below our present detection limit, 150 and 200mm whole-wafer handling, wafer-mapping capability and a cleanroom mini-environment. With these upgrades, measurements were made of wafers from various steps in the integrated circuit fabrication process. These results demonstrate that synchtron radiation brings TXRF into a new and useful regime. Further developments are underway to increase throughput and access for broader application.

Synchrotron-based total-reflection x-ray fluorescence(SR-TXRF) has been developed as a leading technique for measuring wafer cleanliness. It holds advantages over other techniques in that it is non-destructive and allows mapping of the surface. The highest sensitivity observed thus far is 3x108 atoms/cm 2 (-3fg) for 1000 second count time. Several applications of SR-TXRF are presented which take advantage of the energy tunability of the synchrotron source or the mapping capability.

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