MICRODISPERSE IRON SILICIDE STRUCTURES PRODUCED BY IMPLANTATION OF IRON IONS IN SILICON

Iron implanted and subsequently annealed n-type Si(lll) was studied by conversion electron Mossbauer spectroscopy for phase analysis and Aug er electron spectroscopy for sputter depth profiling and element mappi ng. During implantation (200 keV, 3 x 10(17)cm(-2), 350 degrees C) a m ixture of beta- and alpha-FeSi2 is firmed and after the subsequent ann ealing (900 degrees C for 18 h and 1150 degrees C for 1 h) a complete transition to the beta- and the alpha-phase can be detected. The as-im planted profile has Gaussian shape and is broadening during annealing at 900 degrees C to a plateau-like profile and shows only a slight bro adening and depth depending fluctuations of the iron concentration aft er the 1150 degrees C annealing. With scanning Anger electron spectros copy the lateral iron and silicon distribution were investigated and s how for the sample annealed at 900 degrees C large separated beta-FeSi 2 precipitates which grow due to the process of Ostwald ripening. At 1 150 degrees C additionally coalescence of the precipitates occur and a wide extended penetration alpha-FeSi2 network structure is formed.