Near-Field Distribution in Light-Coupling Masks for Contact Lithography

We discuss the potential and limitations of light-coupling masks for high-resolution subwavelength optical lithography. Using a three-dimensional fully-vectorial numerical approach based on Green's tensor technique, the near-field distribution of the electric field in the photoresist is calculated. We study the dependence of the illuminating light and the angle of incidence on polarization. Furthermore, we investigate the replication of structures of various sizes and separations. It is predicted that the formation of features in the 60-nm range is possible using light with a 248-nm wavelength. However, with decreasing separation among the features, crosstalk limits the ultimate resolution.