The formation process of a dislocation cluster outside the oxidation-induced stacking fault (OSF) -ring region during Czochralski (CZ) silicon crystal growth was investigated using a quenching and in situ annealing technique. Dislocation clusters were determined to be interstitial type from inside-outside contrast analysis of the transmission electron microscope (TEM) image. From the quenching experiment, the clustering temperature of dislocations which were formed by supersaturated self-interstitials and/or small dislocation loops was found to be about 1000 degrees C during growth. Furthermore, the characteristic axitial distribution of dislocation size was observed in the halted crystal. This could be explained by the change in concentration of supersaturated self-interstitials and the clustering of dislocations due to the enhancement of diffusion of point defects.