Fabrication of an ultrasharp and high-aspect-ratio microprobe with a silicon-on-insulator wafer for scanning force microscopy

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Abstract
A microprobe having an ultrasharp and high-aspect-ratio stylus was made using a directly bonded silicon-on-insulator (SOI) wafer. The stylus and cantilever were made of 8 μm-thick (100)-Si film and 2 μm-thick dioxide film of the SOI wafer with sufficient reproducibility. The cantilever is 100 μm in length, 20 μm in width, and 1.6 μm in thickness; the stylus is 7 μm in height with an aspect ratio exceeding 2. The stylus was formed first by reactive ion etching and sharpened by orientation dependent etching with KOH solution. The apex of the stylus is 10 nm in radius of curvature. The present microprobe was found adequate for atomic force microscopy (AFM) measurement with spatial resolution better than 10 nm in noncontact-mode topographic imaging. The mode of fabrication, mechanical properties of the microprobe, and results of AFM measurement are discussed.