Proximity correction and resolution enhancement of plasmonic lens lithography far beyond the near field diffraction limit

Abstract

Near-field optical imaging methods have been suffering from the issue of a near field diffraction limit, i.e.imaging resolution and fidelity depend strongly on the distance away from objects, which occurs due to the great decay effect of evanescent waves. Recently, plasmonic cavity lens with off-axis light illumination was proposed as a method for going beyond the near field diffraction limit for imaging dense nanoline patterns. In this paper, this investigation was further extended to more general cases for isolated and discrete line patterns, by enhancing the resolution and correcting the proximity effect with assistant peripheral groove structures. Experiment results demonstrate that the width of single, double and multiple line patterns is well controlled and the uniformity is significantly improved in lithography with a 365 nm light wavelength and 120 nm working distance, being approximately ten times the air distance defined by the near field diffraction limit. The methods are believed to find applications in nanolithography, high density optical storage, scanning probe microscopy and so forth.

Plasmonic Lithography: Recent Progress

“…Progress in the past few years of plasmonic lithography has reached a bottleneck, with transfer of many of the methods into production or manufacturing being hindered by limitations such as the extreme sensitivity of plasmonic effects to nanoscale surface roughness or the requirements for near‐field mask‐resist contact. Many researchers focus their attention on characterizing and perfecting existing superlens lithography processes regarding silver surface roughness and proximity correction due to object–image distance . Claims about potentials to fabricate nanostructures on the order of sub‐10 nm had been made for reducing exposure wavelength from blue—near UV (g/h/i line at 442/405/365 nm) to industrial mainstream 193 nm deep UV light.…”

“…Further refinement of image fidelity has also been proposed and demonstrated, for example, using a proximity‐effect correction method developed by adding peripheral grooves in the mask under off‐axis exposures . As can be seen from Figure , the off‐axis illumination providing higher momentum (due to higher NA) of excitation allows the high spatial frequency information to be transmitted further than for normal incidence, replicating the fine details in the mask.…”

“…Improving imaging quality from a–c) under normal incidence to d–f) under off‐axis incidence, and g–i) with peripheral grooves assisting fine resolution around the edges of patterning. Reproduced with permission under a Creative Commons 3.0 licence . Copyright 2017, The Royal Society of Chemistry.…”

Quantitative analysis and modeling of line edge roughness in near-field lithography: toward high pattern quality in nanofabrication

“…Near-field lithography (NFL) is a sub-diffraction-limited nanopatterning technology by exploiting surface plasmon polaritons (SPPs) and the diffracted field such as quasi-spherical waves (QSWs) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. These waves are excited by an incident light and confined in the horizontal plane and the perpendicular direction through strong near-field coupling via evanescent photons.…”

“…The advances in nanoscale feature-size controllability and scalability allow NFL to be used for 1-to 2.5-dimensional surface nanofabrication [2,3,6,15]. Furthermore, optical proximity correction methods have also been proposed to achieve high pattern fidelity control by adjusting the proximity effects caused by evanescent waves [16][17][18]. However, the previously reported experimental results suffer from a critical issue in terms of line edge roughness (LER) even over a small patterning area, which can limit the applications of NFL [2,3,6,16,19,20].…”