Suppressed silicide formation in FePt thin films by nitrogen addition

Abstract

FePt and FePtN thin films have been prepared on silicon substrates by the relatively new deposition technique known as High Target Utilization Sputtering. Films were annealed post-deposition at temperatures up to 800°C in order to induce the high-anisotropy L10 phase. The FePt films initially showed an improvement in magnetic properties with annealing temperature, but for annealing above around 400°C the magnetic properties deteriorated markedly. The magnetic properties of the FePtN films, however, continued to improve with increasing annealing temperature, right up to the maximum temperature applied of 800°C. Analysis by X-ray diffraction revealed the formation of iron and platinum silicides in FePt films above 400°C, but that such silicides are absent from the FePtN at all annealing temperatures except 800°C. This behavior is attributed to the nitrogen in FePtN films reacting preferentially with the silicon in the substrate to form silicon nitride, thus suppressing the formation of platinum and iron silicides. Thus, by introducing nitrogen during the deposition of FePt films on Si substrates the formation of deleterious silicides appears to be suppressed during thermal treatment, thereby offering protection against silicon pollution.