FORMATION OF COBALT SILICIDE IN CO+ IMPLANTED SI(111)

The microstructural variation of CoSi2 buried layers formed by 100 keV Co+ implantation at 350-degrees-C into Si (111) is systematically studied. The critical dose d(c) of Co+ implantation at 100 keV required to form a continuous CoSi2 buried layer after annealing is the same in both Si (111) and (001), almost-equal-to 1.1 x 10(17) cm-2, corresponding to a threshold peak concentration of 18.5 at. % Co. In addition, we observe continuous buried layers consisting of both A-(fully aligned) and B-(twinned) CoSi2 grains in the (111) samples implanted at doses almost-equal-to d(c). The relative fractions of A and B are found to vary with the implanted doses, current densities of the ion beam, and annealing conditions with the B fractions varying from 0% to 100%. Continuous A-type layers are formed only in the samples implanted to doses greater-than-or-equal-to 1.6 X 10(17) cm-2.