Comparison of Silicon and Silicon-Dioxide Sputtering by a Focused Ion Beam

The focused-ion-beam method is used to modify the surface and form of structures on substrates of almost any material. The significance of silicon and silicon dioxide for modern nanotechnologies calls for comparative analysis of their sputtering by the focused-ion-beam method under identical experimental conditions. In this work, the processes of the sputtering of single-crystal silicon and thermal silicon dioxide are compared. Cross sections of depressions of two types, with a low and high aspect ratio, are studied by scanning electron microscopy. It is established that, in both materials, the depressions of both types have almost the same shape, despite significant differences in the physical properties of silicon and silicon dioxide. Structure formation is simulated by the level-set method using known experimental dependences of the sputtering yields. To take into account sputtering by reflected ions, their angular and energy distributions are calculated using the Monte Carlo method. These dependences and the rates of sputtering of silicon and silicon dioxide by reflected ions established on their basis are almost identical, which indicates the similarity of the sputtering mechanisms for these materials. Superposition of the calculated profiles of the formed depressions onto their cross-sectional images makes it possible to establish that the simulation adequately describes the shape of the resulting structures with a low aspect ratio for both materials. For the structures with a high aspect ratio, satisfactory agreement between the simulation results and experimental data is established for the single-crystal silicon sample; for depressions in silicon dioxide, the discrepancy in the depth of the calculated and experimental profiles is ~10%.