Enhancement of pattern quality in maskless plasmonic lithography via spatial loss modulation

Abstract

Plasmonic lithography, which uses the evanescent electromagnetic (EM) fields to generate image beyond the diffraction limit, has been successfully demonstrated as an alternative lithographic technology for creating sub-10 nm patterns. However, the obtained photoresist pattern contour in general exhibits a very poor fidelity due to the near-field optical proximity effect (OPE), which is far below the minimum requirement for nanofabrication. Understanding the near-field OPE formation mechanism is important to minimize its impact on nanodevice fabrication and improve its lithographic performance. In this work, a point-spread function (PSF) generated by a plasmonic bowtie-shaped nanoaperture (BNA) is employed to quantify the photon-beam deposited energy in the near-field patterning process. The achievable resolution of plasmonic lithography has successfully been enhanced to approximately 4 nm with numerical simulations. A field enhancement factor (F) as a function of gap size is defined to quantitatively evaluate the strong near-field enhancement effect excited by a plasmonic BNA, which also reveals that the high enhancement of the evanescent field is due to the strong resonant coupling between the plasmonic waveguide and the surface plasmon waves (SPWs). However, based on an investigation of the physical origin of the near-field OPE, and the theoretical calculations and simulation results indicate that the evanescent-field-induced rapid loss of high-k information is one of the main optical contributors to the near-field OPE. Furthermore, an analytic formula is introduced to quantitatively analyze the effect of the rapidly decaying feature of the evanescent field on the final exposure pattern profile. Notably, a fast and effective optimization method based on the compensation principle of the exposure dose is proposed to reduce the pattern distortion by modulating the exposure map with dose leveling. The proposed pattern quality enhancement method can open new possibilities in the manufacture of nanostructures with ultrahigh pattern quality via plasmonic lithography, which would find potentially promising applications in high density optical storage, biosensors, and plasmonic nanofocusing.

An elliptical nanoantenna array plasmonic metasurface for efficient solar energy harvesting

“…24,86 Growing nanofabrication methods are increasingly used to create operational nanostructures with nanoscale dimensions. 87–89 Maskless techniques like focused ion beam (FIB) 90 and electron beam lithography (EBL) 61,91 offer high resolution, while masked technologies like nanoimprint lithography 3 offer fast throughputs and scalability to large-area substrates. Recent experimental works demonstrate that TiN/GaN is grown by molecular beam epitaxy, 59 and electron beam lithography is used to prepare TiN 54 and GaN 92 nanostructure arrays for various applications.…”

Spatial modulation of scalable nanostructures by combining maskless plasmonic lithography and grayscale-patterned strategy

“…Moreover, previous works have shown that the assist sub-pixel can relax the shape complexity of the PSF and then play a role in compensating the feature error induced by the decaying characteristics of the evanescent field. 32,34 However, the obtained pattern features of the grayscale values really depend on many factors, primarily the aerial image intensity for each grayscale value, the photoresist contrast, the development time, and the initial PR thickness. Unfortunately, accurate general theoretical formulas for describing the nonlinear relationships between them are lacking.…”

“… 33 The final pattern accuracy has also been effectively improved to over 90% using near-field optical proximity correction (OPC) methods on the basis of the evanescent nature of the SPWs. 32,34 Additionally, patterns with large aspect ratios have been achieved using a hybrid plasmonic waveguide exposure system to amplify the plasmonic optical evanescent field in the photoresist (PR) layer. 35 Almost all of the previously reported results show that the decay characteristics of the SPWs critically affect the final pattern features in plasmonic lithography, but their corresponding relation has not yet been intensively studied.…”

In-plane radiation pattern generated by large particles in dielectric substrates

“…This results in challenging fabrication processes that do not necessarily scale up to large areas well. To date, the fabrication process of these devices is restricted to photolithography with ultraviolet wavelengths [16], and electron beam/ion beam lithography [17]. Both techniques pose important limitations for larger scale access, so new ways must be found to fabricate and control the in-plane emitters.…”