Near field x-ray lithography simulations for printing fine bridges

Abstract

By using the near field in proximity x-ray lithography (PXL), a technique is demonstrated that extends beyond a resolution of 25 nm print feature size for dense lines. ‘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 the mask and wafer, and ‘demagnification ’ is achieved in a selectable range, 1×–9×. The 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 kept compact at the mask. Since the mask–wafer gap scales as the square of the mask feature size, the 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, virtua