The Effect of Chemical Composition on Porous Etching for Epi and Lift-off Wafer Process

Epi and lift-off process can create single crystalline silicon wafers without kerf-loss. There are three steps in epi and lift-off process: porous layer formation, epitaxial growth, and exfoliation. The porous layer is created by electrochemical etching in hydrofluoric acid solution. The ethanol is usually added into the etching solution to enhance the contact between substrate surface and solution. Because the ethanol is volatile, the ethanol content inside the etching solution is adjusted to stabilize the solution composition in this study. A relatively solvent, isopropanol, was also used to replace the ethanol to control evaporation rate of the solution.