Effects and dependencies of the absorption on the

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effects and dependencies of the absorption on the adsorbate orientation will require further investigation. vs. TXRF-NEXAFS [222] has also been em- ployed to investigate the chemical state of nitrogen compounds in aerosols. The aerosol samples of different size fractions were deposited on 30 × 30 mm 2 large silicon wafer surfaces in relatively narrow (100 µ m to 300 µ m) lines by means of a May impactor. The TXRF detection limits for nitrogen being in the upper fg range enable analysis of aerosol samples taken during 10-minute intervals with acceptable accuracy. The applicability of the technique to real aerosol samples has been used to compare nitrogen oxidation state in sub- urban and rural aerosols. For example, A reference spectrum of ammonium sulfate at the N K-edge contains a typical multiplet of π resonances between 400.0 eV and 401.5 eV. The N K-edge NEXAFS spectra of the nano-sized aerosol fractions showed multiplet π resonances similar to that of ammonium sulfate. Both the first TXRF irradiation chamber and the novel (T)XRF in- strumentation for analyzing contamination and depositions on 200 mm and 300 mm silicon wafer surfaces offer off-line reference measurements to assess wafer cleaning procedures and multi-layered systems on wafers, the latter also in a completely reference-free XRF mode [144]. The various experimental
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Methodological Developments and Applications 553 investigations demonstrate the promising prospects of this new instrument in soft X-ray TXRF analysis for ultra-trace contamination of light elements and their speciation by combing NEXAFS with TXRF. Further investiga- tions will also focus on various kinds of contamination such as surface clusters and particles, intentionally deposited aerosols as well as on a reliable analysis of nano-layered materials on wafers exploring the transition regime between TXRF and XRF in the soft X-ray range. Acknowledgments The construction and operation of the (T)XRF instrumentation for 200 mm and 300 mm wafers has been possible by the dedication of Rolf Fliegauf as well as the work of Jan Weser and Michael Bock. Recent experiments and quantitation improvements were performed by Michael Kolbe and by Matthias M¨uller. Special thanks are due to Gerhard Ulm for his support in all of these activities. 7.3.11 Conclusion and Outlook In a well-balanced system of highly motivated, well-trained personnel, and automated equipment, pure reagents and bulk media, cleanrooms and inte- grated data management, TXRF can and must contribute to quality assurance and process stability, support, and canalize creative engineering by continuous learning about materials and processes. TXRF has the advantage of controlled one-point calibration, a linear dynamic range of three orders of magnitude, high grade of automation in operation and data management, high up-time, and a simple control of data plausibility.
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  • Spring '14
  • MichaelDudley

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