Sub-150 nm, high-aspect-ratio features using near-field phase-shifting contact lithography

Abstract

Large-area patterning of ∼50 nm structures on flexible substrates using near-field 193 nm radiation J.

Electromagnetic modeling of near-field phase-shifting contact lithography with broadband ultraviolet illumination

“…Several near-field imaging techniques yielding sub-wavelength resolution have been recently reported [1]- [7]. In particular, near-field phase-shifting contact lithography has been demonstrated to extend the resolution of contact aligners to less than 200 nm by using single-layer photoresists with high aspect ratios [7,8]. The aerial image generated by NFPSCL was suggested to be due to a combination of near-field and phase-shifting effects [4].…”

Enhancement of near-field phase-shifting contact lithography by immersion technique

“…By putting a chromeless phase-shifting mask on top of the photoresist layer, aerial images are resolved at the phase edges, thus implying the phaseshifting effect of NFPSCL. By contrast, the near-field effect rarely appears itself in the NFPSCL process because features can be resolved quite uniformly even in a very thick photoresist layer [1]. The pioneers who were involved in the study of NFPSCL explained this lithographical phenomenon only from the experimental perspective, which resulted in an improper claim of near-field effect in the lithography [3,4].…”

“…It was found both experimentally and theoretically that better resolution can be obtained in NFPSCL by using broadband UV illumination rather than monochromatic UV illumination [1,5,6]. Unfortunately, with broadband UV illumination, the feature resolution is highly sensitive to the thickness of the phase-shifting mask, a characteristic that may undermine the commercial implementation of NFPSCL.…”

“…Near-field phase-shifting contact lithography (NFPSCL) has recently attracted research interest because of its demonstrated capability of generating sub-wavelength and high-aspect-ratio photoresist features by using a broadband ultraviolet (UV) illumination source and a conventional mask aligner [1][2][3][4]. Optical filtering and projection lens were removed from the mask aligner, producing certain results several years ago, which suggested that NFPSCL could be a convenient and inexpensive method for patterning substrates [1].…”

“…Optical filtering and projection lens were removed from the mask aligner, producing certain results several years ago, which suggested that NFPSCL could be a convenient and inexpensive method for patterning substrates [1]. By putting a chromeless phase-shifting mask on top of the photoresist layer, aerial images are resolved at the phase edges, thus implying the phaseshifting effect of NFPSCL.…”