Microtech2010 2010

Silicon Nanostructure Fabrication by Direct FIB Writing and TMAH Wet Chemical Etching

P. Sievilä, N. Chekurov, I. Tittonen
Aalto University, FI

Keywords: focused ion beam, FIB, TMAH, wet etching, nanofabrication


The development of nanotechnology based devices requires rapid prototyping methods that can be applied in combination with well-known clean room processing techniques. We show that focused ion beam (FIB) Ga+-ion implantation can be used to create a mask for fabrication of silicon nanostructures by IC-compatible, anisotropic tetramethylammonium hydroxide (TMAH) wet etching. The FIB writing is fast compared with direct milling of 3D structures, since only a thin (ca. 50 nm) surface layer needs to be modified. The dependence of the masking capability on the FIB implanted dose has been determined, and the threshold dose for observable etching resistance has been measured to be 2 × 10^13 ions/cm2. A high selectivity of at least 2000:1 between the implanted and non-implanted areas has been obtained. The suitability of the process for nanoscale device manufacturing has been characterized by fabricating various types of nanostructures including gratings with the resolution of 20 lines/µm, freestanding beams and bridges with the narrowest features being only 25 nm wide, and high aspect ratio (1:50) nanochannels separated by very thin, nearly vertical sidewalls. The prospective applications of the fabrication method include e.g. cantilever sensors and integrated optical components with subwavelength features.
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