Batch Fabrication of Sharpened Silicon Nitride Tips

A novel sharpening technique for silicon nitride protrusions is reported. A silicon-rich nitride film, which contains more silicon than a stoichiometric silicon nitride film, shows low film stress and has been applied to micro mechanical devices. We found that the edge of the silicon nitride pattern on the silicon wafer became thinner and tapered by thermal oxidation, followed by the removal of the oxidized layer. By applying this technique for sharpening the apex of a beak-like cantilever of silicon nitride, the tip of the acute-angle triangular plate portion of the cantilever terminated into one and was sharpened with a radius of curvature of 17 nm. The small cantilevers integrated with the sharp protrusions for high speed atomic force microscopy in water were batch fabricated. The technique is useful for the fabrication of small cantilevers when low cost is required.