Trace contamination measurements using heavy ion backscattering spectrometry
Heavy Ion Backscattering Spectrometry (HIBS) is a tool for measuring surface contamination at levels much lower than previously achievable with ion beam analyses. Many areas of materials research and development require very low levels of impurities, with advanced microelectronics as the best example. HIBS uses low-energy, heavy ions for analysis, taking advantage of the increased backscattering yield which can be obtained from high Z ion beams at low energy. Background due to increased yield from the substrate is eliminated by a thin carbon foil as part of the detector, with a thickness chosen to range out ions scattered from the substrate and allow only ions scattered from impurities heavier than the substrate to reach the detector. The authors research system, using 150-200 keV N{sup +} beams and a single time-of-flight detector optimized for large solid angle, has achieved a sensitivity ranging from {approximately}5{times}l0{sup 10} atoms/cm{sup 2} for Fe to {approximately}1{times}10{sup 9} atoms/cm{sup 2} for Au on Si, without preconcentration. A stand-alone HIBS prototype which the authors have developed for SEMATECH is expected to reach detection limits of {approximately}5{times}10{sup 9} atoms/cm{sup 2} for Fe and {approximately}1{times}10{sup 8} atoms/cm{sup 2} for Au on Si. In this paper they discuss in detail the factors which affect sensitivity for HIBS.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 10116606
- Report Number(s):
- SAND--94-1737C; CONF-941144--47; ON: DE95005419
- Country of Publication:
- United States
- Language:
- English
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