Phosphorus Diffusion Gettering of Metallic Impurities in Silicon: Mechanisms beyond Segregation

This paper summarises current understanding of phosphorus diffusion gettering (PDG) of metal impurities in silicon. One mechanism that is generally operative is the enhanced solubility of substitutionally dissolved metal species at high P-doping levels due to the Fermi-level effect and pair formation with electrically active phosphorus. For those impurities which are predominantly dissolved on substitutional sites also in intrinsic silicon, an additional gettering effect results from the self-interstitial super-saturation in the intrinsic bulk with respect to the highly P-doped area. Experimental results for cobalt and platinum in silicon lead to the conclusion that silicide formation in the highly P-doped area close to SiP precipitates or directly at the interface to the phosphor-us silica glass (PSG) is a very effective mechanism beyond segregation. The role of electrically inactive phosphorus, self-interstitial injection and PSG growth in this regime is highlighted.