Investigation of correlative parameters to evaluate EUV lithographic performance of PMMA

Solubility Change Behavior of Fluoroalkyl Ether-Tagged Dendritic Hexaphenol under Extreme UV Exposure

This study focuses on the discovery of a single-component molecular resist for extreme ultraviolet (EUV) lithography by employing the ionizing radiation-induced decomposition of carbon-fluorine chemical bonds. The target material, DHP-L6, was synthesized by bonding perfluoroalkyl ether moieties to amorphous dendritic hexaphenol (DHP) with a high glass transition temperature. Upon exposure to EUV and electron beam irradiation, DHP-L6 films exhibited a decreasing solubility in fluorous developer media, resulting in negative-tone images. The underlying chemical mechanisms were elucidated by Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy, and nanoindentation experiments. These analyses highlighted the possible electron-induced decomposition of C-F bonds in DHP-L6, leading to molecular network formation via recombination of the resulting C-centered radicals. Subsequent high-resolution lithographic patterning under EUV irradiation showed that DHP-L6 could create stencil patterns with a line width of 26 nm at an exposure dose of 110 mJ cm-2. These results confirm that single-component small molecular compounds with fluoroalkyl moieties can be employed as patterning materials under ionizing radiation. Nonetheless, additional research is required to reduce the relatively high exposure energy for high-resolution patterning and to enhance the line-edge roughness of the produced stencil.

Fabrication of large-area photonic crystal-modified X-ray scintillator imager for optical coding imaging

The limited pattern area of periodic nanostructures limits the development of practical devices. This study introduces an X-ray interference lithography (XIL) stitching technique to fabricate a large-area (1.5 cm × 1.5 cm) two-dimensional photonic crystal (PhC) on the YAG: Ce scintillator, which functions as an encoder in a high numerical aperture optical encoding imaging system to effectively capture high-frequency information. An X-ray imaging experiment revealed a substantial 7.64 dB improvement in the signal-to-noise ratio (SNR) across a large field of view (2.6 mm × 2.6 mm) and achieved comparable or superior image quality with half the exposure dose. These findings have significant implications for advancing practical applications of X-ray imaging.

Electron Energy Loss Processes in Methyl Methacrylate: Excitation and Bond Breaking

Details of electron-induced chemistry of methyl methacrylate (MMA) upon complexation are revealed by combining gas-phase 2D electron energy loss spectroscopy with electron attachment spectroscopy of isolated MMA and its clusters. We show that even though isolated MMA does not form stable parent anions, it efficiently thermalizes the incident electrons via intramolecular vibrational redistribution, leading to autodetachment of slow electrons. This autodetachment channel is reduced in clusters due to intermolecular energy transfer and stabilization of parent molecular anions. Bond breaking via dissociative electron attachment leads to an extensive range of anion products. The dominant OCH₃^- channel is accessible via core-excited resonances with threshold above 5 eV, despite the estimated thermodynamic threshold below 3 eV. This changes in clusters, where M_nOCH₃^- anions are observed in a lower-lying resonance due to neutral dissociation of the ¹(n, π*) state and electron self-scavenging. The present findings have implications for electron-induced chemistry in lithography with poly(methyl methacrylate).

Near-field infrared nanoscopic study of EUV- and e-beam-exposed hydrogen silsesquioxane photoresist

This article presents a technique of scattering-type scanning near-field optical microscopy (s-SNOM) based on scanning probe microscopy as a nanoscale-resolution chemical visualization technique of the structural changes in photoresist thin films. Chemical investigations were conducted in the nanometer regime by highly concentrated near-field infrared on the sharp apex of the metal-coated atomic force microscopy (AFM) tip. When s-SNOM was applied along with Fourier transform infrared spectroscopy to characterize the extreme UV- and electron-beam (e-beam)-exposed hydrogen silsesquioxane films, line and space patterns of half-pitch 100, 200, 300, and 500 nm could be successfully visualized prior to pattern development in the chemical solutions. The linewidth and line edge roughness values of the exposed domains obtained by s-SNOM were comparable to those extracted from the AFM and scanning electron microscopy images after development. The chemical analysis capabilities provided by s-SNOM provide new analytical opportunities that are not possible with traditional e-beam-based photoresist measurement, thus allowing information to be obtained without interference from non-photoreaction processes such as wet development.