ELECTROMAGNETIC STUDY OF THE DIFFRACTION OF LIGHT BY A MASK USED IN PHOTOLITHOGRAPHY

A mask used in photolithography is modelized by a periodic collection of perfectly conducting metallic strips, which are supposed to be infi nitely thin and lie on the plane surface of a glass medium. A rigorous electromagnetic study of this model is developed for both TE and TM p olarizations. It allows computing diffracted efficiencies and drawing the field maps obtained below the mask illuminated by a plane wave. Th e predictions obtained by this new method developed for this very spec ial grating are compared with those obtained from previously developed grating theories, valid for gratings with finite groove depth.