My. Jung et al., Fabrication of a nanosize metal aperture for a near field scanning opticalmicroscopy sensor using photoresist removal and sputtering techniques, J VAC SCI A, 18(4), 2000, pp. 1333-1337
Micromachining of a nanoscale Si3N4 tip for near field scanning optical mic
roscopy (NSOM) and scanning force microscopy (SFM) has been described. The
tapered optical metal-coated fiber is generally used to provide a subwavele
ngth sized aperture on the tip. Several micromachining methods have been pe
rformed in order to have a metal aperture with a radius less than lambda/2.
Apertures provided with less than lambda/2 and hollow tips would provide a
suitable probe for both NSOM and SFM. A Si3N4 tip coated with a thin metal
film will meet these requirements. The Si tip has been initially fabricate
d using reactive ion etching. The SiO2 etch masks with 10 and 2 mu m were p
atterned followed by Si etching. The etched Si post was at least 3 mu m tal
l and the radii of the tips were found to be 30 and 10 nm depending on the
fabrication methods. A Si3N4 thin film was deposited on the fabricated Si t
ip using a low pressure chemical vapor deposition technique in order to pro
vide a capability for an atomic force microscope. A 30 or 60 nm Cr metal fi
lm was deposited using an electron beam evaporator. The thick photoresist (
PR) film was coated using a two-stage method in order to cover the tall Si
tip. The PR film was carefully etched to have a metal aperture size with le
ss than lambda/2. The removal of the Cr metal at the top of the Si tip has
been performed using a Ne sputtering technique. The radius of the sputtered
tip has been observed to be similar to 80 nm after 2 h sputter etching. (C
) 2000 American Vacuum Society. [S0734-2101(00)17804-2].