CURRICULUM VITAE OF OXIDE PRECIPITATES: FROM NUCLEATION DURING CRYSTAL GROWTH TO THEIR FINAL DESTINATION IN PROCESSED WAFERS

摘要

Grown-in oxide precipitate nucleation during crystal cooling is strongly influenced by the residual vacancy concentration remaining after vacancy agglomeration. The lower the cooling rate of the crystal, the more vacancies are absorbed by D-defects before oxide precipitate nucleation. This results in smaller grown-in oxide precipitate nuclei because nucleation is retarded. D-defects are assumed to be the main vacancy annihilation centers. Based on a first order approximation model, an effective vacancy lifetime was determined from the experimental data. Two mechanisms for the formation of larger oxide precipitate nuclei in a ring wafer, being the potential stacking fault nuclei, are demonstrated. The critical role of the thermal history related grown-in precipitate nuclei of the starting wafer and their evolution during subsequent device processing is established. The appropriate choice of the processing conditions can reduce the density of denuded zone defects by up to three orders of magnitude and increase the generation lifetime in the active device region by one order of magnitude.