Secondary Ion Mass Spectrometry (SIMS) is frequently used in the characterization of thin films, coatings, diffusion processes, materials composition and in the analysis of implants. The SIMS technique has been continuously developed for more than 30 years. One of the main drivers was semiconductor technology. Standard implants in Si like B, As and P, implanted with a few keV to MeV energy are routinely measured with high precision. But nowadays with implant energies of 500 eV and below, when ultra shallow structures are examined, the desired information is in the first few nm to some tens of nm. This has a great impact on the analytical requirements and quantification procedures. Some of these aspects will be examined in this contribution.