Effects on micropyramid and nanoneedle structures for superhydrophobicity on Si surface

This study proposes a method for increasing hydrophobicity using a reactive ion etching (RIE) system. The aim was to study and optimize a surface with hierarchical structures. The effects of micropyramid and nanoneedle structures were investigated for improving superhydrophobicity on the Si surface. To investigate the effects of nanoneedle structures for hydrophobicity, RIE parameters such as the gas ratio, gas pressure, and process time were changed. To compare the contact angles with varying parameters, polytetrafluoroethylene (PTFE) was coated to eliminate oxidation effects on the Si surface. The optimized process conditions for the superhydrophobic surface were saw damage removal for 40 min and RIE for 20 min with O₂/SF₆ = 33%/67%. In the optimized process, the contact angles for the micropyramid, PTFE coating on the micropyramid, micropyramid and nanoneedle, and PTFE coating on the micropyramid and nanoneedle samples were 102.8°, 132.5°, 142.8°, and 171.7°, respectively.