Formation of cobalt silicide in Co+ implanted Si(111)

Abstract

The microstructural variation of CoSi₂ buried layers formed by 100 keV Co⁺ implantation at 350 °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), ≊1.1×10¹⁷ 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 ≊ 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 ≥1.6×10¹⁷ cm⁻².