Soft X-Ray Lithography for High-Aspect Ratio Sub-Micrometer Structures

Soft x-ray lithography is a promising micro-nano fabrication process for patterning of ultra-precise, low and high aspect ratio micro- and nanostructures [1-5]. Research presented in this paper builds upon a new negative-tone, epoxy-based x-ray resist, mr-X, which offers comparable contrast to PMMA (> 3) at a factor of 20x higher sensitivity [6]. Using a 1 mu m thick SiN membrane mask with a similar to 1 mu m thick Au absorber, patterns were transferred into 10 mu m thick resist using the soft exposure mode at the BESSY II WLS beamline. With typical exposure times of a few minutes very precise grating and filter structures can be fabricated with dimensions down to about 500nm.