The mechanism of iron gettering in boron-doped silicon

High-energy B implantation was used to introduce gettering layers into float-zone Si wafers contaminated with 2X10(14) Fe/cm(3). Secondary ion mass spectrometry shows that about 5% of the Fe contamination is collected at the 4 mu m deep peak of a 4x10(14)/cm(2), 3.3 MeV B implant after annealing at 1000 degrees C for 1 h. Deep level transient spectroscopy demonstrates that increasing the gettering B dose from 4X10(12) to 4X10(14)/cm(2) reduces the Fe concentration from 3X10(12) to below similar to 10(10)/cm(3) in the 1-3 mu m deep region from the surface, indicating very efficient gettering. Measurements of the Fe depth profile imply that the depletion of Fe near the gettering layer occurs upon cooling down from 1000 degrees C. The gettering behavior can be qualitatively understood in terms of a Fermi-level-enhanced pairing reaction between Fe and B. (C) 1996 American Institute of Physics.