REACTION OF IRON AND SILICON DURING ION-IMPLANTATION

Using energy-loss spectroscopy, energy dispersive x-ray analysis, electron diffraction, and He+-ion channeling the reaction of Fe during implantation into Si(111) has been investigated at various target temperatures and implantation doses. In samples implanted at 275-degrees-C with 2.8 X 10(17) Fe+ cm-2 a continuous alpha-FeSi2 layer accompanied by alpha-phase precipitates is formed. At 450-degrees-C Fe agglomerates mostly in a-phase precipitates with only a few being beta-FeSi2. At 350-degrees-C 1 X 10(17) Fe+ cm-2 produce precipitates electronically close to FeSi2 but crystallographically poorly defined. At 4 X 10(17) Fe+ cm-2 a beta-FeSi2 layer is formed at the surface and a 20-nm-thick alpha-FeSi2 one followed by alpha-FeSi2 precipitates deeper in the volume. Channeling reveals a minimum yield decreasing with dose indicating improved alpha-phase crystal quality. A sharp increase at 3.3 X 10(17) cm-2 indicates an alpha-beta phase transition. FeSi has not been detected. Precipitates of well defined silicide phases are formed already during implantation. Dose and temperature have a profound influence on the phase formed.