High aspect ratio submicron silicon pillars fabricated by photoassisted electrochemical etching and oxidation

Abstract

A technique for fabricating submicron free-standing silicon pillars has been developed. The silicon pillars have a high packing density, and aspect ratios over 50:1 can easily be achieved. Photoassisted electrochemical etching in hydrofluoric acid is used to etch deep macropores in n-type silicon wafers which have been patterned by standard photolithography. The regular macropores can be used for fabricating photonic band-gap structures. The bulk silicon remaining between the close-packed macropores is oxidized. Free-standing pillars are then formed by subsequently wet etching the silicon dioxide. The pillars are the initial structures for forming quantum wires using further oxidation and etch steps.