Abstract: This paper reports simulation and experimental details of a novel phase shifting technique based on interferometry. Phase shifting is one of the most promising techniques for future high density DRAM fabrication. Conventional phase shifting-masks, however, are difficult to fabricate as they require regions of different optical thickness. This new phase shifting technique does not require any phase shifting materials on the mask. A special interferometer and a mask that has both transmitting areas and reflective areas accomplish the required phase- shift at the image plane. Phase shifting effects are confirmed using both CCD camera analysis as well as photoresist response. The results of computer simulations of critical resolution and error tolerance for this new method as compared with the conventional phase shifting technique are also presented. !14
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