A PHENOMENOLOGICAL THEORY OF ION-BEAM SYNTHESIS OF TERNARY COMPOUND IN SILICON

model for the annealing stage of ion-beam synthesis of a buried layer of a ternary phase in silicon coimplanted with a relatively low dose o f chemically active ions is presented. Physically, the system under in vestigation is a mixture of precipitates of two binary phases which ar e formed in the subsurface region of silicon as a result of chemical r eaction between each implanted impurity and matrix atoms. During annea ling, the precipitates of each binary phase function as alternative si nks for the solutes. Therefore, the ensemble of new phase inclusions i s regarded as a superposition of precipitate pairs. Each pair involves the nuclei of both binary phases. The incorporation of an impurity at om into a binary phase inclusion is assumed to be controlled by the co rresponding kinetic parameter. During annealing, binary phase inclusio ns play the role of seeds for ternary phase formation. Mathematically, the redistribution and chemical segregation of implanted species are described by a set of diffusion equations. The sink terms of the equat ions have been derived in the two-particle approximation which reflect s the competitive growth of two phases. Generally, this set of equatio ns is solved numerically; however, two assumptions allow the analytic solution: there are (i) chemical segregation of the reagent is a predo minant mechanism of phase formation; (ii) the phases formed have a con stant chemical composition. The model is successfully applied to the d escription of silicon oxynitride synthesis by silicon implantation wit h a substoichiometric dose of oxygen and nitrogen ions. The computer s imulation showed that nitrogen atoms, collected on the oxide surface, change the interface mechanism of oxide growth into that of bulk diffu sion, which eventually facilitates the ternary phase formation. (C) 19 96 American Institute of Physics.