Is ultra shallow analysis possible using SIMS?

The use of secondary ion mass spectrometry (SIMS) to analyse ultra shallow dopant profiles is now becoming routine. However, interpretation of the data is not straight forward and the conventional method of effectively multiplying intensity and ion dose (time) axes by calibration constants to "quantify" the data is certain to produce serious inaccuracies. We demonstrate that for oxygen primary beams, analysis of silicon at normal incidence without oxygen flooding is currently the only analytical condition which leads to quantifiable, accurate profiles, and show that depth resolution better than I nm can be obtained from within 0.5 nm of the surface using sub-keV primary beams