The resolution limit for two-dimensional crossed-grating patterns created by projecting mask objects by using a coherent beam has been investigated. We consider first two conventional mask types, a binary-amplitude mask and a two-level phase-shifting mask, in analyzing relationships between a diffraction-beam configuration and an image-intensity distribution. Then we derive, as a mask that overcomes the resolution limit of the conventional ones, a four-level phase-shifting structure with which the minimum image period can be reduced to √2/2 times that of the two-level phase-shifting mask.
© 2003 Optical Society of America
(070.2580) Fourier optics and signal processing : Paraxial wave optics
(110.2960) Imaging systems : Image analysis
(110.3960) Imaging systems : Microlithography
(110.5220) Imaging systems : Photolithography
(350.5730) Other areas of optics : Resolution
Yasuyuki Unno, "Resolution Limit for Two-Dimensional Crossed-Grating Patterns Projected by a Coherent Beam," Appl. Opt. 42, 3259-3267 (2003)