RBS, SY-XRF, INAA and ICP-IDMS of antimony implanted in silicon – A multi-method approach to characterize and certify a reference material

Abstract

A layer of Sb atoms, implanted with an energy of 400 keV and a nominal dose of 5×10 16 atoms/cm 2 into a high purity silicon wafer, was certified for its areal density (atoms/cm 2) using Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA) and inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) and for its isotope ratio using INAA and ICP-IDMS. Excellent agreement between the results of the different independent methods was found. In the present work, the measurements of the homogeneity of the areal density of Sb, previously determined with RBS in spots having 1 mm diameter, are improved with synchrotron X-ray fluorescence analysis: Higher precision in even smaller sample spots allows to estimate a reduced inhomogeneity of the whole batch of samples of the order of only 0.4%. Thus the uncertainty of the certified value can further be reduced. Down to fractions of a chip with 0.3×0.4 mm 2 area, the areal density is now certified as (4.81±0.06)×10 16 Sb atoms/cm 2, where the expanded uncertainty 0.06 (coverage factor k=2) corresponds to only 1.2%. The relative merits of the different analytical methods are discussed.