Three-Dimensional Nanofabrication Utilizing Selective Etching of Silicon Induced by Focused Ion Beam Irradiation

A simple process of fabricating a three-dimensional nanostructure on a silicon surface was investigated in this study. The silicon surface area irradiated by focused ion beam (FIB) was selectively etched in HF, whereas the non-irradiated area was scarcely etched, and consequently, a concave nanostructure was fabricated on the irradiated area. To control the depth of the nanostructure, the depth dependence on ion irradiation parameters was investigated. As a result, it was found that the depth of the irradiated area can be controlled by changing ion irradiation parameters, such as dose and ion energy. Under a low-dose condition, the irradiated area was scarcely etched, due to the formation of an amorphous layer on the interior of silicon. Subsequently, it was etched in KOH to evaluate the mechanism of this phenomenon. In addition, the surface roughness dependence on ion irradiation parameters was investigated. Finally, three-dimensional nanostructures were fabricated on the basis of these results, suggesting that this method is a novel three-dimensional nanofabrication method