Abstract: An optical characterization method of repeat units forming a diffraction structure, each repeat unit including a geometric pattern produced, at least in part, using a porous material, the method including: determining the geometric parameters of the patterns; performing a scatterometric acquisition using an optical measurement system of the experimental optical response of the diffraction structure placed in a chamber at a given pressure, a presence of an adsorbable gaseous substance in the chamber causing condensation of the adsorbable gaseous substance in a part of open pores of the patterns; and determining a theoretical optical response of the diffraction structure from the determined geometric parameters and by adjusting an optical index of the material of an area of each of the patterns, in which the adsorbable gaseous substance has condensed, to make a difference between the experimental response and the theoretical response less than or equal to a given threshold.

Abstract: A method for the optical characterisation of repeat units repeated in a regular manner so as to form a diffraction structure, each repeat unit including at least one geometric pattern, each of the patterns being produced, at least in part, using a porous material. The method includes determining the geometric parameters of the patterns and performing a scatterometric acquisition of the experimental optical response of the diffraction structure placed in a chamber at a given pressure, the presence of an adsorbable gaseous substance in the chamber causing condensation of the adsorbable gaseous substance in at least one part of open pores of the patterns of the structure.