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 techniques¹ for future DRAM fabrication. In recent years, many phase shifting methods have been proposed to extend the resolution limit and the contrast of the image of patterns. These techniques, however, have several problems. The phase shifting elements on the mask need precise placement and exact thickness in order to achieve the desired amount of phase shifting. Further adjustment becomes impossible once the masks are fabricated. As a result, the manufacturing cost of phase shifting masks is high, and yields are at present quite low. This has slowed the introduction of the phase shift technique into the production line.

© 1994 Optical Society of America