Wettability Patterning

microfabrication applications, it is widely used to transfer the designed patterns from an etching mask to the substrate. When the sample is immersed into the etching bath, the etchant only contacts and reacts with the substrate surfaces where are uncovered by the etching mask. The suitable materials for the mask can be polymers or other materials such as photoresist, SU-8,SiO2 andSi3N4, which feature much lower etching rate in the selected etchant in contrast to the substrate material. Wet etchants fall into two broad categories: isotropic etchants and anisotropic etchants. Isotropic etchants attack the material being etched at the same rate in all directions. Anisotropic etchants attack some single-crystal materials (typically silicon) at different etch rates depending on the crystallographic orientation of the substrate, so there is more control of the shapes being produced. Wet etching is the most common processing in semiconductor industry and MEMS applications.