PERFORMANCE OF DIPOLE ILLUMINATION COMBINED WITH PUPIL FILTER

The pupil filtering technique has been proposed as an effective method in the field of optics. In this work, pupil filtering is applied to a n optical lithography system. We theoretically analyze partially coher ent imaging, and not only the pupil filter but one combined with other optical elements, is suggested. Through these two methods, the follow ing results are obtained: 1) twofold enhancement of depth of focus (DO F) and resolution limit improved to 0.26 mu m (i-line, 0.60 NA) for li nes and spaces, using the pupil filter combined with oblique illuminat ion, i.e.; dipole illumination; 2) twofold enhancement of DOF for hole , using the pupil filter assisted by a mask, i.e., shifterless halfton e mask. In this paper, several calculations and experimental results o f using an i-line stepper with pupil filtering are presented and the p otential for pupil filtering in optical lithography is discussed.