Analysis of phase defect effect on contact hole pattern using a programmed phase defect in EUVL mask

Influence of phase defect on printed images of mask pattern was experimentally investigated by printing contact hole (CH) pattern of hp 32 nm on wafer. And the experimental results were compared with the simulation results. A test mask prepared for this experiment contained programmed phase defects of 92 nm ~ 34.8 nm in width and of around 0.68 nm ~ 1.65 nm in depth. The defects were arrayed in a way such that the pitch of the array would differ from the pitch of the absorber contact hole pitch. Therefore, the phase defects were placed at different positions relative to those of the CH patterns. Mask patterns were printed on wafer using an exposure tool NXE3100 with a numerical aperture (NA) of 0.25 and a reduction of 4X. To evaluate the printed patterns affected by the phase defects, circular illumination was employed. The incident angle of mask illumination chief ray was 6 degrees. The printed CH patterns were measured by SEM. An influence of resolution limit of the resist pattern did seem to appear in this experiment, to be a quantitative difference between the simulation and experimental results, the relative location dependence was quite noticeable and the effect of a phase defect was mitigated by covering the defect with an absorber pattern.