Achieving nanometer-scale, controllable pattern shifts in x-ray lithography using an assembly-tilting technique

摘要

In x-ray lithography the finite gap between the mask and substrate, and the highly directional nature of the short wavelength radiation, enable one to shift the entire mask image by tilting the mask-substrate assembly relative to the axis of illumination. The amount of image shift depends on the mask-substrate gap and the tilt angle, and it can be calculated by simple geometry. The shift can be into any azimuthal direction. The experimental results are consistent with the calculated shift. In our experiments we typically used gaps of 3μm and tilts of 5.7° (0.1 rad) to achieve a shift of the order of 300 nm. There are a number of advantages and new lithography features that can be accessed using the assembly-tilting technique. For example, various double-exposure schemes, some of which are designed to achieve extremely fine lines or unique patterns, are easily accomplished by the assembly-tilting technique. Moreover, if a mask and substrate contain appropriate alignment marks, viewed optically at normal incidence, and a small misalignment is measured, this can be corrected by tilting the entire assembly rather than by moving the mask relative to the substrate.