Determining optical influence of mask layer of lithographic mask involves measuring geometric dimensions of first and second test structures and determining phase shift and/or absorption of mask layer by comparing them

摘要

The method involves illuminating a test substrate (20) using a mask (10) with first mask areas (1) in which the mask layer (5) is cut out and second areas (2) in which it is present and making test structures (11,12) in the substrate. First test structures (11) are formed that are illuminated by respective first mask areas. Second test structures (12) are formed whose positions are shaded by a second mask area and that exist through constructive interference of electromagnetic radiation (16) matching the mask layer. Geometric dimensions of the first and second test structures are measured and the phase shift and/or absorption of the mask layer determined by comparing them.