COALESCENCE OF BURIED COSI2 LAYERS FORMED BY MESOTAXY IN SI(111)

Evolution and microstructure of buried CoSi2 layers formed by 100-keV Co+ implantation at 350-degrees-C into Si(111) are systematically studied in this work. Implant doses ranged from 1 x 10(16) to 1.6 x 10(17) cm-2. Three types of CoSi2 precipitates are observed during the mesotaxial process: A type (fully aligned with the host lattice), B0 type (twinned on the (111) plane parallel to the surface), and B1,2,3 type (twinned on one of the three {111} planes inclined to the surface). The fraction (probability of occurrence) of each type varies with both the implantation and annealing conditions. The critical dose required to form a continuous layer after 600 + 1000-degrees-C annealing is found to be the same, almost-equal-to 1.1 x 10(17) cm-2, in both (111) and (001) substrates, despite pronounced differences in precipitate morphology. Formation of a continuous, twinned (B0 type), buried layer after 600 + 1000-degrees-C annealing is shown to be possible in (111) samples implanted at the critical dose.