In one aspect, the present invention is a technique of, and a
system and sensor for measuring, inspecting, characterizing and / or evaluating optical lithographic equipment, methods, and / or materials used therewith, for example, photomasks. In one embodiment, the
system, sensor and technique measures, collects and / or detects an
aerial image (or portion thereof) produced or generated by the interaction between the
photomask and lithographic equipment. An
image sensor unit may measure, collect, sense and / or detect the
aerial image in situ—that is, the
aerial image at the
wafer plane produced, in part, by a production-type
photomask (i.e., a
wafer having integrated circuits formed during the
integrated circuit fabrication process) and / or by associated lithographic equipment used, or to be used, to manufacture of integrated circuits. A
processing unit, coupled to the
image sensor unit, may measure the critical dimensions of features of the
photomask, using data which is representative of the intensity of light sampled by the
image sensor unit, to control at least one operating parameter of the lithographic equipment.