SYNTHESIS OF BETA-FESI2 AND ALPHA-FESI2 PHASES BY FE ION-IMPLANTATION INTO SI USING METAL VAPOR VACUUM-ARC ION-SOURCE

High-current Fe ion implantation technique was employed to synthesize Fe-silicide layers on Si wafers, using a newly constructed metal vapor vacuum arc ion source. The Fe ions were extracted at a voltage of 40 kV with a varying ion current density from 65 to 152 muA/cm2 and a nominal ion dose varied from 3 X 10(17) to 3 X 10(18) Fe/cm2. At a fixed nominal dose of 4 X 10(17) Pe/cm2, a semiconducting beta-FeSi2 layer gradually grew on Si with increasing ion current density and a qualified beta-FeSi2 layer with a relative sharp interface was obtained, when the ion current densities exceeded 115 muA/cm2. While implanting at a fixed ion current density of 152 muA/cm2 with varying ion dose, the beta-FeSi2 phase began to form first at a nominal dose of 3 X 10(17) Fe/cm2, and eventually transformed into a metallic alpha-FeSi2 phase when the nominal dose reached 3 X 10(18) Fe/cm2. Further information of the formation of Fe disilicides was obtained by comparing the postannealing results of some of the implanted wafers with those observed immediately after implantation. Tle formation mechanism of the Fe disilicides is discussed in terms of the beam heating effect, which in turn resulted in a simultaneous thermal annealing during Fe ion implantation.