IRON AND ITS DETRIMENTAL IMPACT ON THE NUCLEATION AND GROWTH OF OXYGEN PRECIPITATES DURING INTERNAL GETTERING PROCESSES

The detrimental impact of iron on the nucleation and precipitation of interstitial oxygen (O(i)) has recently been reported from this laboratory and interpreted in terms of the different thermodynamical behavior of iron silicides (FeSi(x)) and iron silicate (Fe2SiO4). By varying the nucleation time of oxygen precipitation and adjusting different initial iron concentrations ([Fe]i) in CZ silicon wafers we have found a threshold concentration of iron (about 1 . 10(11) atom/cm3) above which the precipitation was impeded. Estimates, based on migrating interstitial oxygen (O(i)) and iron (Fe(i)) gave a threshold level of iron in the range of 1 . 10(10) atom/cm3 to 1 . 10(11) atom/cm3. Scanning electron microscope (SEM) pictures provided compelling evidences that iron is retarding oxygen precipitation.