Experimental evaluation of phase contrast lithography

Phase contrast lithography (PCL) using an annular-phase-only filter on a pupil plane of a projection optics was evaluated experimentally for lines and spaces and hole patterns. A g -line exposure tool was fabricated so that a spatial frequency filter can be inserted in the pupil of the projection optics for a feasibility study. Using a common annular-phase-only filter, depth of focus (DOF) was 40% and 14% better than that without the filter for 0.6 µ m lines and spaces and 0.6 µ m hole patterns, respectively. In addition, it was confirmed that combination of PCL with low contrast imaging process is more effective in DOF enhancement.