Fabrication Of Ultrahigh-Density Nano-Pyramid Arrays (Npas) On (100) Silicon Wafer Using Scanning Probe Lithography And Anisotropic Wet Etching

Convex and concave nano-pyramid Arrays (NPAs) with an areal bit density of 258 Gbits/in2 has been demonstrated by means of scanning probe lithography (SPL) and wet ecthing on the (100) silicon wafer. We investigated the use of a contact-mode atomic force microscope (AFM) in the generation of oxide patterns on silicon (100) surfaces. Subsequently, utilizing oxide patterns as Si etching masks, the Si substrate was dipped in aqueous KOH solution, where un-oxidized regions are selectively etched by aqueous KOH orientation-dependent etching (ODE). Using this simple process, 20nm convex NPAs with 100nm pitch can be fabricated successfully. Similarly, about 2nm concave NPAs with 100nm were obtained after the oxidized samples were dipped in acqueous HF solution, the oxide regions were selectively etched away. To demonstarte the capability of this technology, the ascii codes were written on silicon and the data storage density more than 10 times of current optical recording has been achieved. We also demonstrated that the minimum size of the pyramids and the minimum pitch could be easily controlled by the apex size of the pyramid, that is, the size of the oxidized region by AFM-based field-induced oxidation. The results indicated that this technique has potentials to provide a pathway to the higher densities that will be needed in the decades ahead.