a method of producing etched structures in substrates by anisotropic plasma etching , wherein an essentially isotropic etching operation and side wall passivation are performed separately and in alternation , with the substrate being a polymer , a metal or a multicomponent system , and portions of the side wall passivation layer applied during passivation of the side wall are transferred to the exposed side surfaces of the side wall during the subsequent etching operations , so the entire method is anisotropic as a whole .