Improvement of Phase-Shifter Edge Line Mask Method

Two kinds of improved phase-shifter edge line (PEL) masks have been developed for critical dimension control. One new mask consists of a chrome line and partially overlapped shifter film. In this mask, exposed pattern sizes are controlled by adjusting the chrome linewidth. It has been found that a set of repeated fine-chrome lines (“blind”) acts as a uniform light attenuator. The other new mask (“blind PEL mask”) has been devised by combining the “blind” and shifter pattern. These new masks make it possible to delineate different-sized fine patterns (≥0.2 µm) at the same exposure dose. With the “blind PEL-mask”, unnecessary shifter edge patterns can be eliminated by only one-time exposure.