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It has been shown using SIMS profiling that, by means of low energy ion implantation into crystalline and amorphous silicon, doping profiles with depths around 30 nm can be reproducibly produced. The deposition of a cap layer onto the silicon surface considerably improves the depth resolution of the SIMS apparatus in the case of extremely shallow doping layers. Fifty nanometre thick Au/Ge cap layers were applied successfully for the accurate measurement of the trailing course of the boron distribution. For future measurements of the course of reaction, a silicon cap layer is necessary to avoid or minimize the change of the sputter rate and the secondary ion yield in the interface region to the boron implanted silicon. A comparison with the measured boron distributions showed good agreement with simulations in the case of implantation into amorphous material.