Nucleation and growth mechanisms of the bulk microdefects in oxygen controlled silicon substrate wafers heavily doped with boron and antimony were studied following pre- and postepitaxial enhanced precipitation annealing at various temperatures. It was observed that “grown-in” microdefects in both dopant species are nucleated by a similar mechanism during the crystal growth cooling period. Microdefect growth behavior appears, however, to be different, probably due to differing effects of the dopant species. It was also observed that the pre- and postepitaxial annealing as well as the epitaxial deposition processes have a strong impact on the growth of the bulk microdefects. Based upon this study, generic growth characteristics of the bulk microdefects of both P+ and N+ materials are established and a growth kinetics model is proposed.