A Soft Lithographic Approach to the Fabrication of Single Crystalline Silicon Nanostructures with Well-Defined Dimensions and Shapes

Abstract

A procedure was developed for large-scale fabrication of nanometer-sized structures of single crystalline silicon with well-defined dimensions and shapes. Near-field optical lithography was used to define the nanostructures in a thin film of positive-tone photoresist with an elastomeric phase mask. The nanostructures were then transferred into the underlying silicon-on-insulator (SOI) substrate through a reactive ion etching (RIE) process. With this method, we can routinely generate silicon nanostructures ~130 nm in lateral dimension. They can be supported on the surface of a solid substrate as a patterned array, or released into a freestanding form. The lateral dimension of these silicon structures could be further reduced to as small as ~40 nm using stress-limited oxidation at elevated temperatures. The flexibility of this approach was demonstrated by fabricating nanoscale wires, rods, rings, and interconnected triangles of silicon. Using a two-step exposure method, the silicon nanowires can be precisely “cut” into silicon nanorods with specific lengths.