Friction-induced selective etching on silicon by TMAH solution.

Friction-induced selective etching provides a new thought direction in the field of nanotechnology with high resolution, low cost, flexibility and site control. In this work, it was found that the scratched area on a silicon surface can play a role as a mask against etching in tetramethyl ammonium hydroxide (TMAH) solution, resulting in the formation of protrusive hillocks. Friction-induced selective etching was found to depend on the temperature and etching time. The hillock height initially increased with the temperature or etching time, and then the hillock disappeared due to the mask etching off. In contrast, the applied normal load for scratching on silicon had little effect on the hillock height produced by selective etching in TMAH solution. Further analysis showed that crystal distortions or crystal amorphization could act as a mask against selective etching on silicon. Through control tip traces for scratching, different patterns can be produced on the silicon surface by friction-induced selective etching in TMAH solution. These results can enrich the fundamental aspects of scanning probe microscope (SPM)-based nanolithography, and provide an alternative method to produce nanostructures for various applications.