Impact of Deformation of the Edges of Two Complementary Patterns on Electron Beam Projection Lithography Mask Making

摘要

In Electron Beam Projection Lithography (EPL), one of the issues is how to reduce the critical dimension (CD) error observed at the boundary of two complementary patterns when being stitched together to form one smooth line. This paper is concerned about edge deformation of the two lines to reduce the CD error. Among several forms, a pair of concave- and convex-three-up-step edges was formed for 580-nm-wide lines with 80-nm-wide steps on a 2-μm-thick Si membrane and a pair of concave- and convex-two-up-step edges was formed for 330-nm-wide lines with 75-nm-wide steps. Our choices of the shapes of deformed edges are presented based on the degree of difficulties of making finer features on masks. The first choice is a pair of concave- and convex-one-step edges. Two EPL data conversion systems, SX-GIGA/EPLON of Seiko Instruments Inc. and PATACON-6600 of Nippon Control System Corp., are introduced. They are found to automatically yield required stitching correction patterns. Their flexibility in stitching correction enough to cope with customers' requests makes them useful and practical.