The resolution limits of conventional optical lithography reflect the low-pass spatial-frequency [numerical aperture (NA) /λ] filter characteristics of the imaging system. Imaging interferometric lithography extends the resolution of optical lithography to the spatial-frequency limits of optics (2/λ) . Off-axis illumination downshifts the high-frequency components of the mask pattern. An interferometric beam at the wafer upshifts these frequency components back to their original spatial frequencies following the lens. 2× reduction imaging interferometric lithography experiments demonstrate a continuous frequency coverage up to ~3N.A./λ with a consequent threefold resolution enhancement.
© 1999 Optical Society of America
(070.0070) Fourier optics and signal processing : Fourier optics and signal processing
(110.0110) Imaging systems : Imaging systems
(110.5220) Imaging systems : Photolithography
(220.3740) Optical design and fabrication : Lithography
Xiaolan Chen and S. R. J. Brueck, "Imaging interferometric lithography: approaching the resolution limits of optics," Opt. Lett. 24, 124-126 (1999)