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12 May 2005 Super diffraction lithography (SDL): fine random line pattern formation by single-exposure with binary mask
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A novel RET named Super Diffraction Lithography (SDL), which enables 90~80 nm random line by single exposure in KrF wavelength, has been developed. A pair of bright lines, which sandwiches binary or Atten-PSM line and is surrounded by attenuating non-phase-shifting (Atten-NPS) area, is formed on a mask. The Atten-NPS area of the mask is composed with a small pad array whose pitch is finer than the resolution limit of projection optics. Then, this mask can be fabricated with a single layer patterning. When this mask is illuminated by an obliquely incident light with a specific incident angle, very sharp dark line image is formed at center of the bright lines. Because the outside of the pair is Atten-NPS area, image intensity for this area can become much higher than a slice level of the central dark line image, resulting in no resist pattern at the outside of the pair. By application of a sub-resolution assist feature (SRAF) for semi-dense pattern, fine line can be imaged throughout pattern pitch. Then, utilizing SDL, very fine random line can be formed by SINGLE EXPOSURE of SIMPLE STRUCTURE MASK. In KrF exposure at NA=0.82, 90 nm line with pitch of down to 240 nm can be achieved by a binary mask. Using 6% transmission Atten-PSM, 80 nm becomes possible. Moreover, 50 nm isolated line becomes feasible in KrF exposure by application of high transmission Atten-PSM. We believe that SDL is the most cost-effective and easily applicable RET for gate pattern formation in advanced logic devices.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
S. Nakao, J. Abe, A. Nakae, A. Imai, K. Narimatsu, and K. Suko "Super diffraction lithography (SDL): fine random line pattern formation by single-exposure with binary mask", Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005);

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