METHOD OF DETERMINING STRAY RADIATION FOR EVALUATING QUICKLY STRAY RADIATION CONDITION AND LITHOGRAPHIC PROJECTION APPARATUS

摘要

PURPOSE: A method of determining stray radiation and a lithographic projection apparatus are provided to evaluate quickly the presence of the stray radiation by in-situ. CONSTITUTION: A lithographic projection apparatus includes a projection system(Ex,lL) with NA(Numerical Aperture). A projection beam of radiation is provided. The radiation has a predetermined wavelength(λ). The projection beam is patterned according to a pattern with a feature. The patterned beam is projected on an image plane to form an image of the feature. A detector with a detector aperture is arranged in a path of the projection beam. The detector aperture is arranged to a position coincident with the image plane. An expanded region is covered with the image of feature. The expanded region is obtained by a notional dilatation over a distance of at least λ/NA in the detector aperture. Detected intensity of radiation is measured. A coefficient for representing a stray radiation condition of the projection system is calculated based on the measure radiation intensity.