PROXIMITY EFFECT ON PATTERNING CHARACTERISTICS OF HOLE PATTERNS IN SYNCHROTRON-RADIATION LITHOGRAPHY

This paper reports the results of analyzing the proximity effect on the patterning characteristics for plural neighboring hole patterns in synchrotron radiation lithography. Fresnel diffraction simulation was used and pattern replication experiments were performed with pattern pitch, proximity gap, and mask contrast as parameters. Even when the pattern pitch (hole:space) is 1:1, pattern sizes down to 0.2 mu m can be replicated with a large dose margin under a large proximity gap condition up to 40 mu m, irrespective of the mask contrast. A low-contrast (2.5) mask has an advantage over the conventional-contrast (7) mask in that it allows the use of a larger proximity gap when replicating hole patterns with a size of 0.1-0.2 mu m. Moreover, the phase-shifting mask we previously proposed improves the exposure latitude and widens the proximity gap, so that it is possible to use a 20-mu m gap to replicate 0.1-mu m hole patterns for a pitch of 1:1 and to use a 30-mu m gap for a pitch of 1:2.