Fabrication of complex curved three-dimensional silicon microstructures using ion irradiation

Abstract

We have developed a process to fabricate arbitrary-shaped, three-dimensional microstructures in 0.4 cm p-type silicon using focused high-energy proton beam irradiation, followed by electrochemical anodization. This has enabled us to produce free-standing complex microstructures such as arrays or long wires, grids, wheels, vertically stacked wires and wires which can be controllably bent upward and downward in the vertical plane. The two most important factors which determine the wire cross-section dimensions and depth are the irradiation ion fluence and energy. We can controllably vary the width of wires from 1 to 5 νm by varying the fluence of 1 MeV protons and the depth of wires from 2 to 15 νm by varying the proton energy. By using a combination of multiple energy proton irradiation over a range of 2001000 keV, and gray-scale masks, different ion penetration depths and multilevel free-standing three-dimensional silicon structures can be obtained in a single etch step. © 2012 IOP Publishing Ltd.