Formation of Highly Ordered Silicon Nanowires by a High-Speed Deep Etching

We report the formation of highly ordered vertical silicon nanowires using a hydrogen-assisted deep reactive ion etching technique. Nanosphere lithography with 460- and 300-nm polystyrenes is employed to realize the etching mask for fabrication of sub-50-nm patterns. SiNWs can be achieved consequently with a top-down process using vertical etching of silicon where the underetching can be limited to 10 nm. By means of a patterned mesh-like structure, we have improved the arrangement order of the nanospheres and nanorods. The etching is performed using three gases of O₂, H₂, and SF₆ in two subsequences of etching and passivation, and in a low plasma density capacitive coupled RIE system. This process is capable of etching high aspect ratio nanometric features with high etching rate. Values for aspect ratio around 100 for sub-100-nm SiNW with etching rate of 0.8 μm/min are achieved. Applying proper process parameter can result in conical tip nanorods, which have the potential for large-scale fabrication of nanowire emitter arrays.