Phase defect printability analyses: dependence of defect type and EUV exposure condition

Phase defect printability and imaging characteristics were investigated by using aerial image simulation to clarify the phase defect impact on patterns depending on defect types, and on exposure conditions. In particular, the difference between the impacts caused by the same size bump phase defect and pit phase defect on 28 nm ~ 16 nm L&S projected patterns were investigated by calculating line width variations. Aerial images of phase defects in an absence of any absorber pattern were also calculated, and the image intensity losses of the two types of defects were compared. For a dipole illumination with 0.25 NA (numerical aperture) the pit phase defect impact was found to be stronger than the bump phase defect impact, when the two defect widths were less than 70% of the half-pitch of L&S patterns on the mask. This occurrence was not foreseen by the defect image calculation. On the other hand, for circular illumination with 0.33 NA, the bump defect impact was found to be stronger than the pit phase defect impact, which was consistent with the defect image calculation results. The contribution of dipole illumination in lowering the phase defect impact was confirmed for both bump and pit phase defects.