Ultra low energy Boron ion implants in silicon analyzed by not-oxydizing O2+ bombardment and synchrotron radiation grazing incidence x-ray fluorescence

Former results on B ultra shallow junction (USJ) characterization by SIMS revealed that collecting B+ positive ions under oxidizing conditions, like normal O2+ ion bombardment or oblique incidence O2+ beam with 'oxygen flooding', is effective in terms of detection limit, dosimetry accuracy and depth resolution. However, the profile shape at the surface and/or at the native SiO2/ Si interface is strongly influenced by artefacts resulting in a B peak at the surface. In recent years, a not-oxidizing approach (analysis in vacuum under oblique incidence beam), once corrected for the variation of ion yield, resulted more accurate in revealing the profile shape at surface and at the (native) SiO2/ Si interface. The drawback of the approach is the rapid roughness formation on the SIMS crater bottom with a consequent rapid variation of sputtering yield. In this work a not-oxidizing approach (either a 0.5 or 0.3 keV impact energy O2+ beam with ~70° incidence) is improved by rotating the sample during sputtering to reduce the roughness formation and applied to characterize ultra low energy B implants in Si. 11B implants in (100) silicon with implant energy between 0.2 and 3.0 keV and implanted dose between 1E14 and 5E15 cm-2 were analyzed. A uniformly B doped Si sample was analyzed varying O2 leak pressure in order to identify the species more sensitive to the actual state of oxidation and the relation of the sensitivity factors with the degree of oxidation. Atomic force microscopy was applied to investigate the development of roughness on the SIMS crater. The resulting quantified B profiles were cross-checked with results of (soft x-ray) synchrotron radiation grazing incidence x-ray fluorescence (SR-GIXRF) obtained at the radiometry laboratory of the Physikalisch-Technische Bundesanstalt at Bessy II within the EC financed ANNA project (contract n. 026134(RII3)).