Phase shifting masks in Displacement Talbot Lithography for printing nano-grids and periodic motifs

• We designed clear phase shift masks for use with Displacement Talbot Lithography.
• Simulated images show high-contrast and practically unlimited depth of focus.
• High-fidelity square and triangular motifs printed uniformly in photoresists films.
• Printed patterns are not feasible with conventional proximity or Talbot lithography.
• Method suitable for production of patterned growth substrates and photonic structures.

High-resolution periodic structures with geometric shapes such as squares or triangles cannot be readily produced with low-cost photolithography methods like interference or proximity photolithography. We present a method for robust printing of such patterns with Displacement Talbot Lithography (DTL) using phase shifting masks. This combination effectively yields high-contrast images that extend to large distances from the mask. It therefore enables uniform images to be printed over large, non-flat substrates without loss of resolution. Phase masks with several different motifs have been designed, fabricated and tested using DTL exposures. High-fidelity grid and island type structures with square and triangular motifs and sub-micron feature sizes were printed into different types of photoresists using wafer–mask gaps on the order of 100 μm. The experimental results show good agreement with calculated image intensity distributions. The method is suitable for low-cost production of high-quality patterned growth substrates and photonic structures among other applications.

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