Fabrication of short and thin silicon cantilevers for AFM with SOI wafers

Thin and short cantilevers possess both a low force constant and a high resonance frequency, thus are highly desirable for atomic force microscope (AFM) imaging and force measurement. In this work, small silicon (Si) cantilevers integrating with a Si tip were fabricated from silicon-on-oxide (SOI) wafers that were used for reducing the variation of thickness of the cantilevers. Our fabrication process provided SOI chips containing 40 silicon cantilevers integrating with an ultra-sharp Si tip. We showed that the resolution of images obtained with these tips was much higher than those obtained with the commercial tips, while the force constants were much less, that is, more suitable for imaging soft samples. The availability of such SOI chips greatly facilitates large scale modification of the surfaces of the silicon cantilever tips with a monolayer of oligo(ethylene glycol) derivatives that resist the non-specific interactions with proteins, rendering them most suitable for imaging and measurement of biological samples.