Evanescent-wave interference lithography enabled by guided-mode-resonance field transfer

초록

We propose a guided-mode-resonance (GMR) approach to evanescent-wave interference lithography that overcomes the severe depth of field and proximity limitations of conventional near-field methods. The scheme consists of a resonant dielectric grating and a photoresist layer separated by a low-index buffer medium, where phase-matched evanescent coupling transfers resonantly enhanced standing-wave fields from the grating to the photoresist. Using rigorous coupled-wave analysis, we design a UV-compatible structure comprising HfO2 grating ridges, a commercial photoresist layer, and a transparent immersion-oil spacer. An example device supports two coupled GMR states near 365 nm that generate subwavelength interference fringes with a period of 120 nm, corresponding to approximately lambda/3. Enhanced field localization in the photoresist produces peak intensities of similar to 600 & times; the incident intensity while maintaining fringe visibility of similar to 0.999. The resonances remain robust for practical incidence-angle and grating-photoresist spacing variations, including a 1-& micro;m separation compatible with conventional lithographic processing. The large resonant enhancement can reduce exposure times by nearly three orders of magnitude or equivalently lower required laser power. These results establish guided-mode-resonance field transfer as a potential route toward high-resolution, low-power evanescent-wave interference lithography using all-dielectric structures.

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