The Influence of Focused Ion Beam Scanning Strategy on the Silicon Sputtering Process During the Formation of Micro- and Nanostructures

To form micro- and nanostructures on substrates made of various materials, the focused ion beam method is used. The essence of the method is that a narrow probe of gallium ions moves along the surface of the sample and, stopping at certain points, locally removes the material by sputtering it. The characteristics of the sputtering process using the focused ion beam (FIB) method depend significantly on the chosen strategy for scanning the ion beam over the sample. In this work, standard multi-pass and line-by-line scanning strategies were used to determine the characteristics of the milling process. The studies of the manufactured rectangular boxes with lateral dimensions from 100 nm to 20 µm and depth from 30 to 700 nm were carried out using transmission electron microscopy and X-ray microanalysis. It was found that the transition from multi-pass movements of the ion beam to line-by-line scanning makes it possible to reduce the concentration of implanted gallium from 25 to 20 at % under conditions of smooth milling of the sample material and from 45 to 6 at % when the edge milling process is employed. Using large-sized recesses as an example, it was demonstrated that the use of a line-by-line scanning strategy allows for an approximately 6-fold increase in the effective sputtering yield of the material by an ion beam and a reduction in the thickness of the amorphized layer of the irradiated silicon substrate by approximately 25%. It is shown that a decrease in the concentration of implanted gallium atoms during edge milling occurs during thermal annealing of the structures. The application of the proposed approach will allow the formation of micro- and nanostructures with a low content of gallium atoms in the near-surface region.