Formation of silicon nanograss and microstructures on silicon using deep reactive ion etching

A hydrogen-assisted reactive ion etching method for the silicon nanograss formation in desirable shapes and locations is reported. By controlling the etching parameters of this process, one can achieve grass-free high aspect ratio vertical structures on silicon substrates or arrive at grass-full structures in pre-designed features and in desired places. Using this method vertical or spaghetti-like Si nanograss with a height of 2-3--m and width of 30-100-nm is realised. The effect of SF₆ as a critical parameter on the nanograss formation has been studied relating the grass density and width to pressure and power. Inclusion of grass onto the silicon surface changes its wetting parameter to make it hydrophilic and oleophilic. The resonance frequency of silicon membranes with the addition of nanograss has shown a significant drop because of an improved surface adhesion to oil, owing to increasing the effective mass of the membrane.