Polyenergy ion beam synthesis of buried oxynitride layer in silicon

Abstract

The efficiency of silicon oxynitride synthesis in silicon crystals implanted with substoichiometric doses of oxygen and nitrogen ions is investigated both experimentally and theoretically. Si crystals are implanted with oxygen and nitrogen ions with doses of 1.5 and 4.5×10 17 cm −2 , respectively, at fixed oxygen ion energy of 150 keV and nitrogen ion energies varied from 80 to 180 keV. The samples annealed at 1200 ∘C for 2 h were analysed by secondary ion mass spectroscopy (SIMS). Theoretically, a `diffusion-alternative sinks' model is applied to the annealing stage of ion beam synthesis of a buried layer of a new phase in solids. It is shown that the maximum of the ternary phase production is attained when nitrogen ions are implanted deeper than oxygen ions. An explanation of this fact is given in terms of that (i) the segregation of oxygen and nitrogen species on the surface of oxide nuclei removes the kinetic restriction of nuclei growth, characteristic of oxide growth, at the expense of only oxygen atoms, and (ii) the higher the implantation energy the smoother the shape of ion range distribution in the target, which, in its turn, causes the predominance of the impurity sink over the impurity diffusion.