Uniform precipitation of oxygen in large diameter wafers

In the present stage of development, 300 mm crystals often contain a transi tion from vacancy-rich to interstitial-rich. Due to this radially varying c oncentration of intrinsic point defects, the radial size distribution of gr own-in oxide precipitate nuclei is also inhomogeneous in these wafers. In o rder to achieve a radially uniform bulk defect density for internal getteri ng, a slow temperature ramp induced growth of all grown-in oxide precipitat e nuclei is the appropriate procedure to overcome problems resulting from t he inhomogeneous size distribution of grown-in nuclei. This approach is bas ed on the observation that in contrast to the nuclei size distribution, the nuclei density distribution is homogeneous over the wafer, independent of the dominant intrinsic point defect. (C) 1999 Elsevier Science BN. All righ ts reserved.