Catalyst feature independent metal-assisted chemical etching of silicon

We demonstrate metal-assisted chemical etching of Si substrates with consistent etching rates for a wide range of metal catalysts of dots and stripes in meshes and solid arrays. The governing mechanism switched from in-plane to out-of-plane mass transport with metal catalysts, which resulted in highly anisotropic chemical etching in-position of micron-scale metal catalyst. Dramatic changes in etch rates and surface topologies were interpreted as resulting from diffusivity of the reactants and byproducts through the nanoholes in the metal catalyst. Experimentally verified out-of-plane mass transport extends the capability of metal-assisted chemical etching to the fabrication of nano- and micron-scale three-dimensional semiconductors.