Nanomachining of (110)-oriented silicon by scanning probe lithography and anisotropic wet etching

We have demonstrated that silicon nanostructures with high aspect ratios, having $\text{∼400\hspace{0.05em}}\mathrm{nm}$ structural height and $\text{∼55\hspace{0.05em}}\mathrm{nm}$ lateral dimension, may be fabricated by scanning probe lithography and aqueous KOH orientation-dependent etching on the H-passivated (110) Si wafer. The high spatial resolution of fabricated features is achieved by using the atomic force microscope based nano-oxidation process in ambient. Due to the large (110)/(111) anisotropic ratio of etch rate and the large ${\mathrm{Si/SiO}}_{\mathrm{2}}$ etch selectivity at a relatively low etching temperature and an optimal KOH concentration, high-aspect-ratio gratings with (111)-oriented structural sidewalls as well as hexagonal etch pit structures determined by the terminal etch geometry can be obtained.