Nanolithography in the Evanescent Near Field

Abstract

New applications in microscopy and nanofabrication have emerged from recent advances in the optical near field. This paper reviews the implications of using evanescently decaying components in the near field of a photomask as a lithography tool for the fabrication of nanoscale structures. Patterning at resolution below the diffraction limit for projection optical lithography has been demonstrated using such evanescent near-field optical lithography (ENFOL) with broadband illumination (365–600 nm). Line widths of 50 nm and gratings with 140 nm period have been achieved. Ultrathin photoresist layers in conjunction with conformable photomasks are employed and both additive and subtractive pattern transfer processes have been developed. Full electromagnetic field simulations of the exposure process show that a high-contrast image is present within the resist layer, and that the exposure is dominated by one polarization for the grating structures studied. These reveal the potential of ENFOL in achieving feature sizes smaller than λ/20.