Phosphorus diffusion gettering of platinum in silicon: Formation of near-surface precipitates

Various techniques of transmission electron microscopy as well as secondary ion mass spectroscopy have been used to study phosphorus diffusion gettering of platinum in silicon under conditions of high phosphorus concentrations. PtSi precipitates have been observed directly beneath the interface between silicon and the phosphorus silica glass formed on top of the wafers. Gettering at 920 degreesC leads to the formation of isolated PtSi particles adjacent to SIP precipitates whereas an almost closed silicide film is observed at 1100 degreesC in the absence of SiP precipitates. For the latter conditions we observe a broad band of extrinsic faulted loops which establish a supersaturation of silicon self-interstitials in the highly phosphorus doped layer. The results support previous modeling of the precipitation mode of phosphorus diffusion gettering which assumes that local currents of silicon self-interstitials may lead to silicide precipitate formation.