FABRICATION AND RAMAN-SCATTERING STUDIES OF ONE-DIMENSIONAL NANOMETER STRUCTURES IN (110) SILICON

A simple technique for fabricating large fields of uniform nm scale Si structures is reported. This technique makes use of the highly anisotropic etching rates of KOH:H2O solution (40 wt. %) in Si (400:200:1 = [110]:[100]:[111]). A large field of uniform sub-mum thick walls, along the [112] direction, is generated on a (110) Si sample coated with Si3N4 and photoresist films, by standard interferometric lithography techniques. The developed photoresist grating pattern is transferred into the Si3N4 layer by isotropic CF4 plasma etching. Finally, the nitride layer serves as an etch mask for the anisotropic chemical etch. Arrays of Si walls with pitch of 0.34 mum, sharp (110)-{111} corners, depths of 2.0 mum, and wall widths below SEM resolution limits are reported. The Raman scattering spectra of these structures shows shifted, asymmetrical line shapes; simple model calculations based on size-effect-induced relaxation of the usual DELTAk=0 momentum selection rule provide estimated wallwidths less-than-or-equal-to 10 nm.