Gold- and Silver-Nanoparticle-Assisted Etching of p-Si and n-Si: A Discussion of Etching Behavior Based on Polarization Curves

Abstract

Metal-assisted etching (metal-assisted chemical etching) is increasingly recognized as a crucial method for fabricating silicon (Si) nanostructures. This process involves the dissolution of Si both directly beneath metal catalysts (local etching) and at locations away from them (remote etching). We previously investigated general corrosion, a kind of remote etching, in metal-particle-assisted etching of moderately-doped n-Si and explained its mechanism in platinum-assisted etching where a sponge-like porous layer was observable on the top surface of Si, which dissolves spontaneously. However, general corrosion caused by gold (Au)-assisted etching has not been explained yet, as the soluble layer was not clearly observed. It is also difficult to explain why general corrosion was suppressed in silver (Ag)-assisted etching under the conditions we examined. In this work, we estimated the depth of general corrosion caused by Au- and Ag-nanoparticle-assisted etching of moderately-doped p-Si and n-Si based on the etched structures and mass loss of substrate. We also discussed etching behavior based on polarization curves of bare Si, metal-deposited Si, and metal wires. This work provides insights into the underlying mechanism of remote etching and proposes a potential strategy to mitigate it.