GROWTH-KINETICS OF IRON SILICIDES FABRICATED BY SOLID-PHASE EPITAXY OR ION-BEAM SYNTHESIS

The growth kinetics of the sequential formation of FeSi and beta-FeSi2 layers on (111) Si during solid phase epitaxy were investigated over a wide range of temperatures. Surface layers of beta-FeSi2 were produced by evaporation of Fe onto (111) Si substrates and subsequent rapid thermal annealing. The composition and the thickness of the growing layers were determined by Rutherford backscattering spectroscopy. The phases were identified by X-ray diffraction. First, the FeSi phase forms in the temperature range 500-625-degrees-C. The thickness of the FeSi layer increases with the square root of time, which is indicative of diffusion-limited growth of the silicide layer. An activation energy of 1.36 +/- 0.25 eV was deduced. The formation of beta-FeSi2 layers was found to be nucleation controlled with an approximate activation energy of 2.6 +/- 0.5 eV. In addition, the coarsening of FeSi2 Precipitates in (111) Si during the formation of buried FeSi2 layers was studied using ion beam synthesis and thermal annealing. The estimated activation energy for the coarsening process was 3.63 +/- 0.33 eV, which is consistent with Ostwald ripening.