Proceedings Article | 16 June 2003
KEYWORDS: Photomasks, Near field, Semiconducting wafers, Printing, Lithography, Near field diffraction, X-ray lithography, X-rays, Physics, Manufacturing
By using the Near Field in Proximity X-ray Lithography (PXL), the technique is demonstrated that extends beyond a resolution of 25 nm print featuer size with 2:1 pitch to line width. "Demagnification by bias" of clear mask features is positively used in Fresnel diffraction together with multiple exposures of sharp peaks. Exposures are performed without lenses or mirrors between mask and wafer, and the "demagnification" is achieved in the selectable range 1X to 9X. Pitch is kept small by multiple, stepped exposures of sharp, intense, image peaks followed by single development. Low pitch nested lines are demonstrated. The optical field is kep compact at the mask. Since the mask-wafer gap scales as the square of the mask feature size, mask feature sizes and mask-wafer gaps are comparatively large. Because the features are themselves larger, the masks are more easily manufactured. Meanwhile exposure times, for development levels high on sharp peaks, are short, and there are further benefits including defect reduction. Many devices, including batches of microprocessors, have been demonstrated previously by traditional 1X PXL which is the most mature of the Next Generation Lithographies and which is now further extended. For 2D Near field patterning, temporal and spatial incoherence at the Critical Condition are used to show, not only that peculiarities in the aerial pattern, such as "ripple" and "bright spots", can be virtually eliminated, but also that there is an optimum demagnification, around 3X, in the Fresnel diffraction, where the contrast is highest. At this demagnification, patterns of various dimensions can be printed using various and appropriate demagnifications.
