Simulation of Material Sputtering and Gallium Implantation during Focused Ion Beam Irradiation of a Silicon Substrate

Revealing the regularities of interaction of accelerated ions with an irradiated material based on the Monte Carlo simulation contributes to the efficient application of focused ion beam technique in modern nanotechnologies. The correctness of the calculation results depends on the model chosen and the parameters determining the surface binding energy (SBE) of sputtered atoms. In this work, the SBE has been determined within the discrete-continuous model, which makes it possible to consider the formation of gallium precipitates during irradiation of a silicon substrate with gallium ions. To compare the simulation results with the experimental data on material sputtering by a focused ion beam, two types of rectangular boxes have been prepared. The structures of the first type were formed at the same dose, close to 5 x 10(17) cm(-2) (corresponding to the steady-state sputtering regime), at accelerating voltages of 8, 16, and 30 kV. The structures of the second type were formed at an ion energy of 30 keV and doses of 2.5 x 10(16), 5 x 10(16), and 1 x 10(17) cm-2. The box cross sections were investigated by transmission electron microscopy. The sputtering yield and depth distribution profiles of gallium atoms, calculated in the SDTrimSP 5.07 software package, were compared with the experimental data using the R factor. Two sets of values have been established for the variable parameters: the SBE of gallium atoms and the alpha(1) parameter of the discrete-continuous model. The first set describes the experimental data with acceptable accuracy for a small number of implanted gallium atoms, which is implemented for low ion doses, as well as for a beam energy of 8 keV and a dose of 5 x 10(17) cm(-2). The second set is optimal for describing the ion beam interaction with the substrate at ion energies of 16 and 30 keV under steady sputtering conditions.