<title>Quarter-micrometer lithography system with oblique illumination and pupil filter</title>

Abstract

Oblique illumination, one of the super-resolution techniques, is very attractive because of its simple structure as well as its high effectiveness for super-resolution. This technique, however, has some defects such as dependence of pattern size, nonuniformity among line patterns and the resolution limit that it has naturally. In this work, we theoretically analyze partially coherent imaging and verify the usefulness of pupil filtering for overcoming those defects. Pupil filtering can demonstrate the potential of the oblique illumination technique. In particular, dipole illumination combined with pupil filter, which has two different transmittance parts, works effectively, which extends DOF for both fine and large patterns. Resolution limit of oblique illumination is also modified. Several calculations and experimental results, using an i-line stepper with this combined technique, are shown and a potential of pupil filtering in various super-resolution techniques is discussed.