Abstract: A method is provided for patterning a wafer comprising at least one substrate for the manufacture of an integrated circuit. The method comprises: etching at least one portion of the substrate with a reactive gas plasma to obtain an optical emission signal, resulting from the products of the reaction between the plasma and the substrate and having a predetermined spectral fingerprint; carrying on the etching of the substrate up to a predetermined end point; and monitoring the spectral fingerprint of the optical emission signal to detect the etching end point. The method comprises the further insertion of an inert gas in the plasma to obtain an increase in the intensity of the optical emission signal.