to advantageous characteristics of the process: [0070] the mask is composed of an electrically conductive material such as a metal, especially a noble metal such as Au, Ag, Pt or Pd, a metal alloy, a conductive oxide such as obtained by doping, especially SnO2:F, SnO2:In and similar oxides, a ceramic or a polymer; [0071] the mask is used in contact with the layer to be etched; we mention in this r