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 and robust technique which allows very high aspect ratio structures to be etched on n-type <;100> substrates. For example, arrays of hundreds of narrow (10μm) and long (85mm) trenches can be etched completely through a 650μm 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 10nm-30nm in order to achieve uniform etching.