Fabrication of sub-10nm Si-tip array coated with Si3N4 thin film for potential NSOM and liquid metal ion source applications

A nanosize Si tip array for various purposes has been fabricated on the n-t ype (100) low resistive (0.05 ohm-cm) Si wafers using electron beam direct writing method. The Si pillars with diameter less than 0.1 mu m can be pote ntially utilized for a near field optical microscope tip or a liquid metal ion source application. SiO2 layers with different thicknesses of 500nm and 1.5 mu m were initially thermally grown and followed by the fabrication of the 500nm dot array pattern with an electron beam(EB) resist SAL60. The ox ide etch-mask layers with two different thicknesses of 500nm and 1.5 mu m w ere patterned with a magnetic field enhanced reactive ion etcher. The 500nm EB resist layer (SAL601) was used as an etch-mask for pattern formation du ring oxide etching. The complete removal of the EB resist and the erosion o f the 1.5 mu m thick oxide dot-patterns resulted from the similar to 270 se cond etching period was observed. On the other hand, no erosion of the oxid e mask with the EB resist remaining was found after 90 sec. oxide etching b y scanning electron microscope. The two step RIE processes on the sample wi th a 500nm oxide etch mask were carried out with an isotropic SF6 etching f ollowed by the anisotropic (Cl-2 + He) etching in order to fabricate tall S i-pillar arrays with similar to 4 mu m height.. Finally, the 35nm Si3N4 coa ted Si-tip array using a low pressure chemical vapor deposition (LPCVD) was fabricated. The LPCVD Si3N4 coated Si-tip array will be micromachined into sub-100nm metal aperture for the potential near field optical sensor or in to a sub-10nm Si or Si3N4 aperture for liquid metal ion source.