The influence of rapid thermal annealing thermal donor formation, and hydrogen on the precipitation of oxygen was studied by infrared analyses. We concluded that the oxygen loss during the subsequent precipitation Steps is not directly correlated with the quantity of thermal donors formed. Our study supports rather that thermal donors are made of self-interstitial agglomerates. However, a 450 degrees C treatment and a prior rapid thermal annealing enhances the precipitation of oxygen, through a path which does not lead,to platelets. Indeed spherical precipitates evidenced by infrared analyses are formed early at low temperature, during the thermal treatment at 750 degrees C. They may grow from aggregates, formed at 450 degrees C, and we think that they are made of oxygen atoms and vacancies. The growth of these aggregates occurs as the temperature of the thermal treatments increases and is enhanced by a prior rapid thermal anneal. Finally, a retardation of the precipitation due to hydrogen introduced during a pretreatment was observed in specific conditions.