Electroless chemical etching of silicon in aqueous NH4F/AgNO3/HNO3 solution

One-step metal-assisted electroless chemical etching of silicon substrate was investigated. The etching was performed in aqueous NH4F/AgNO3/HNO3 solution at room temperature. The effect of several etching parameters on the morphology of etched layer was studied namely: silicon type, doping level and crystallographic orientation. It is shown that the morphology depends strongly on etching parameters. The reflectivity of the nanostructured layers was examined by reflectance spectroscopy and was found to depend on silicon resistivity. Indeed, the lowest average value of reflectance (a few percent) in the range 250–800 nm was obtained for 5–10 Ω cm p-Si(1 0 0), 0.001–0.003 Ω cm n++-Si(1 0 0) and 5–10 Ω cm n-Si(1 0 0). Finally, the dissolution mechanism of silicon by Ag-assisted electroless etching is discussed.