High-aspect-ratio structure fabrication on (110)-oriented silicon surfaces using tribo-nanolithography.

This study investigated methods of fabricating high-aspect-ratio structures on a silicon surface using a combination of tribo-nanolithography and wet chemical etching. Tribo-nanolithography forms an amorphous phase on a single-crystal silicon surface that has an etch resistance against potassium hydroxide so that a protruding structure can be fabricated by wet chemical etching. To fabricate high-aspect-ratio structures, (110)-oriented silicon was used, and the effect of machining parameters on the structure shape was investigated. The results showed that a structure with vertical side walls could be fabricated by machining along the (112) direction. The etch resistance against potassium hydroxide depended on the normal load and number of repetitions, and the width and the maximum height were functions of these conditions. The aspect ratio of the structure increased with the etch time as long as the amorphous phase was maintained. A sub-micrometer-scale high-aspect-ratio structure was fabricated based on these results, demonstrating the possibility of using this simple and effective method.