Iron gettering mechanisms in silicon

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Abstract
Boron implantation into silicon offers a unique system for studying the gettering mechanisms of Fe. Using deep level transient spectroscopy to monitor the remaining Fe in the gettered region and secondary‐ion‐mass spectroscopy to measure the concentration of Fe redistributed to the B region, we show that the gettering mechanisms can be quantitatively described. A combination of Fermi‐level‐induced Fe+ charge‐state stabilization and Fe+–B− pairing acts to lower the free energy of Fe in p+ regions. This can lead to Fe partition coefficients as high as 106 at a p+/p interface at temperatures below ≊400 °C. The dynamic response of the system is diffusion limited during the cooling cycle. B gettering is more effective than gettering produced by Si implantation damage and more effective than trapping by a neutral impurity such as C. These mechanisms also make a large contribution to the effective gettering of Fe by p/p+ epitaxial silicon wafers. The Fermi‐level/pairing gettering mechanism is also expected to operate for Cr and Mn.