It was recalled that rapidly pulled Czochralski crystals usually contained large octahedral vacancy agglomerates. These voids (D defects) degraded the integrity of thin gate oxides by causing time zero dielectric breakdown. Upon annealing the wafers at temperatures above 1100C, the gate oxide integrity was clearly improved. It was shown, using light-scattering topography and transmission electron microscopy, that the vacancy agglomerates could be filled with SiO2, by internal oxidation. This occurred via the diffusion of interstitial O to the voids, which could be regarded as being internal surfaces. They therefore became less detrimental to thin gate oxides because they now consisted of SiO2 itself. However, they were still present in an octahedral geometry, and could be detected using Brewster and infra-red light-scattering tomography.

G.Kissinger, G.Morgenstern, J.Vanhellemont, D.Gräf, U.Lambert, H.Richter: Applied Physics Letters, 1998, 72[2], 223-5