RESOLUTION ENHANCEMENT OF HOLE PATTERNS IN SYNCHROTRON-RADIATION LITHOGRAPHY

This paper analyzes the influence of Fresnel diffraction on the patterning characteristics of isolated hole patterns in synchrotron radiation lithography by comparing Fresnel diffraction simulation extended to 2-dimensional patterns and pattern replication experiments with mask contrast as a parameter. It is possible to replicate hole patterns down to 0.1 mum at a large proximity gap of 30 mum by keeping the mask contrast at 2.5-7. However, the exposure latitude for fine patterns below 0.1 mum diminishes abruptly. It also becomes clear that the phase-shifting mask which we previously proposed offers the possibility of replicating ultra-fine hole patterns (< 0.1 mum) with a large exposure latitude at the 30-mum proximity gap. Moreover, by using an X-ray mask with a circular absorber pattern instead of the conventional square pattern, it should be possible to solve the problem of pattern deformation and improve the exposure latitude.