Antimony was implanted into silicon, followed by a rapid thermal annealing step to recrystallize the substrate. Post-activation annealings were made at 800 and 900 °C with increasing time, to study the deactivation of antimony using a combination of SIMS, MEIS and TEM analyses. It was found that the antimony profile does not broaden for moderate thermal budgets. However, during thermal treatments, antimony atoms continuously move towards the surface. There, they pile-up in non-substitutional positions and form precipitates. It was also confirmed that this phenomenon happens after solid phase epitaxy. Possible explanations are discussed.