The gettering of transition metals by Internal Gettering (IQ) is an important tool for the management of metal contamination in IC processing. But unlike most external gettering systems, IG systems must be "set up" in a silicon wafer via a controlled precipitation of dissolved interstitial oxygen in the wafer during heat treatments. This paper addresses the question of the threshold to effective IG as the oxygen in the system goes from an essentially fully dissolved state to varying degrees of precipitation. The central step in the transition to an efficient gettering system is a morphological transformation of a growing oxygen cluster from an unstrained state to a strained platelet. Experimental data of the transformation rates as a function of nuclei site density and oxygen concentration are given. The dependence of the transformation rate has been successfully modeled and the time to create efficient IG systems as a function of site density, temperature and oxygen concentration is calculated.
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