Metal-Assisted Etching of High-Aspect-Ratio Structures for Solar Cell Applications: Controlling the Porosity of Au Thin Films

Metal-assisted etching can be used to etch high-aspect-ratio structures in silicon (Si) wafers. Using Au as catalytic metal, we have developed a simple robust technique that allows very high aspect ratio structures to be etched on n-type <1 0 0> substrates. For example, arrays of hundreds of narrow (10 μm) and long (85 mm) trenches can be etched completely through a 650-μm-thick wafer in order to harvest silicon for solar cells using the SLIVER technique. We have developed a method for controlling the porosity of deposited Au films with thicknesses of 10-30 nm in order to achieve uniform etching.