Deep-UV microsphere projection lithography

Alireza Bonakdar, Mohsen Rezaei, Robert L. Brown, Vala Fathipour, Eric Dexheimer, Sung Jun Jang, Hooman Mohseni*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

In this Letter, we present a single-exposure deep-UV projection lithography at 254-nm wavelength that produces nanopatterns in a scalable area with a feature size of 80 nm. In this method, a macroscopic lens projects a pixelated optical mask on a monolayer of hexagonally arranged microspheres that reside on the Fourier plane and image the mask's pattern into a photoresist film. Our macroscopic lens shrinks the size of the mask by providing an imaging magnification of ∼1.86 × 104, while enhancing the exposure power. On the other hand, microsphere lens produces a sub-diffraction limit focal point - a so-called photonic nanojet - based on the near-surface focusing effect, which ensures an excellent patterning accuracy against the presence of surface roughness. Ray-optics simulation is utilized to design the bulk optics part of the lithography system, while a wave-optics simulation is implemented to simulate the optical properties of the exposed regions beneath the microspheres. We characterize the lithography performance in terms of the proximity effect, lens aberration, and interference effect due to refractive index mismatch between photoresist and substrate.

Original languageEnglish (US)
Pages (from-to)2537-2540
Number of pages4
JournalOptics Letters
Volume40
Issue number11
DOIs
StatePublished - Jun 1 2015

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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