Platinum gettering in silicon by phosphorus

The gettering capture of certain metallic impurities (especially Au) is known to be associated with enhanced solubility in the presence of high concentration phosphorus. Platinum is a metal whose diffusion characteristics closely resemble that of gold. It is likewise a deep acceptor in n-type silicon. One might therefore expect its gettering behavior also to be similar. Experiments described here show this not the case. Platinum was indeed found to be gettered effectively by phosphorus though on nonsubstitutional sites at the sample surface. This is explained to be a supersaturation of silicon self-interstitials induced by the diffusion of phosphorus which kicks platinum onto high mobility, low solubility interstitial sites. The possible relevance of this solubility supression mechanism for Au gettering is discussed.