Novel fabrication method of the tiny aperture tip on silicon cantilever for near field scanning optical microscopy

In this paper we present a novel fabrication method of a miniature aperture on a Si cantilever for Near field Scanning Optical Microscopy (NSOM). The Si cantilever with a SiO₂ pyramidal tip was microfabricated in a batch process. The silicon was thermally oxidized at low temperature (1050 °C). Due to the effect of locally compressive intrinsic stress within the oxide on the solubility of oxygen, the thermal silicon oxide at the bottom of the pyramidal etch pit is thinner. Thus, a tiny aperture can be created by partly etching the SiO₂ in buffered HF solution. Using the etching method aperture size ranging from 150 nm to 500 nm have been experimental realized. By optimizing the SiO₂ etching time, sub 100 nm size apertures are feasible using the fabrication method. The fabricated probe was mounted to an Atomic Force Microscope (AFM) head. The AFM in contact mode and corresponding NSOM images of Au patterns on Si wafer were simultaneously recorded.