Metal-assisted chemical vertical etching of Si: Effect of catalyst morphology and oxidant concentration

Deep vertical etching of Si using hydrogen peroxide as oxidant and Au as catalyst has been studied in terms of relative reactant concentrations and catalyst morphology. The concentrations of hydrogen peroxide and hydrofluoric acid are highly important and the ratio of the same can be varied to achieve isotropic to highly anisotropic vertical etching. Catalyst morphology and positioning of the substrate was also seen to affect vertical etch profiles, with high catalyst deposition rates and horizontal placement of the sample giving deep etching without defects.