Depth profiles of a shallow implanted layer in a Si wafer determined by different methods of thin-layer analysis

Several different methods of thin-layer analysis have been applied to depth profiling of the same sample on the nanometer scale: two variants of Monte Carlo simulations, X-ray photoelectron spectrometry (XPS) with sputtering, sputtered neutrals mass spectrometry (SNMS), grazing-incidence X-ray fluorescence (GI-XRF), Rutherford backscattering (RBS) and a newly developed method, i.e. a combination of wet-chemical etching and total-reflection X-ray fluorescence (TXRF). Depth profiles were recorded for a silicon wafer implanted with Co ions at a dose of 1017 cm−2. For a detailed comparison, the results were expressed as basic quantities in SI units: the depth in m or nm and the concentration in mole mole−1. The depth profiles were shown to differ significantly. Characteristic parameters, e.g. the maximum, the respective depth, the width and the dose or area of the profiles differ by a factor up to 3, the offset of the profiles (surface value at depth zero) even differs by more than one order of magnitude. The reason for such discrepancies were mainly found in an unsuitable calibration leading to high systematic errors. However, RBS and the new variant of TXRF showed reasonable, consistent profiles and a good correspondence which could be verified statistically after an estimation of their uncertainties.