Nano-ridge fabrication by local oxidation of silicon edges with silicon nitride as a mask

A method to fabricate nano-ridges over a full wafer is presented. The fabrication method uses local oxidation of silicon, with silicon nitride as a mask, and wet anisotropic etching of silicon. The realized structures are 7-20 nm wide, 40-100 nm high and centimeters long. All dimensions are easily adjustable by varying the oxidation time, the wet etching time and the mask geometry, respectively. As an additional advantage, the method features a spatial frequency doubling effect. This can be helpful in realizing higher feature densities than would be possible using conventional lithography.