Abstract. We report on the extreme ultraviolet (EUV) patterning performance of tin-oxo cages. These cage molecules were already known to function as a negative tone photoresist for EUV radiation, but in this work, we significantly optimized their performance. Our results show that sensitivity and resolution are only meaningful photoresist parameters if the process conditions are optimized. We focus on contrast curves of the materials using large area EUV exposures and patterning of the cages using EUV interference lithography. It is shown that baking steps, such as postexposure baking, can significantly affect both the sensitivity and contrast in the open-frame experiments as well as the patterning experiments. A layer thickness increase reduced the necessary dose to induce a solubility change but decreased the patterning quality. The patterning experiments were affected by minor changes in processing conditions such as an increased rinsing time. In addition, we show that the anions of the cage can influence the sensitivity and quality of the patterning, probably through their effect on physical properties of the materials.
The
outbreak of SARS-CoV-2 has emphasized the value of point-of-care
diagnostics, as well as reliable and cost-effective serological antibody
tests, to monitor the viral spread and contain pandemics and endemics.
Here, we present a three-dimensional (3D) nanofluidic device for rapid
and multiplexed detection of viral antibodies. The device is made
from poly(methyl methacrylate) and contains 3D fluidic channels with
nanoscale topography variations on the millimeter length scale, enabled
by combining gray-scale e-beam lithography and nanoimprint lithography.
It works with capillary pumps only and does not require a complex
microfluidic setup and pumps, which hinder the widespread usage of
micro- and nanofluidic devices. The device is designed to size dependently
immobilize particles from a multiparticle mixture at predefined positions
in nanochannels, resulting in distinct trapping lines. We show that
it can be used as an on-chip fluorescence-linked immunosorbent assay
for highly specific and sensitive multiplexed detection of serological
antibodies against different viral proteins. Further test flexibility
is demonstrated by on-bead color multiplexing for simultaneous detection
of IgG and IgM antibodies in convalescent human serum. The particle
sorting is further leveraged to enable concurrent detection of anti-spike
(SARS-CoV-2) and anti-hemagglutinin (influenza A) antibodies. The
device’s applications can be further extended to detect a large
variety of diseases simultaneously in a reliable and straightforward
manner.
A new class of negative-tone resist materials has been developed for electron beam and extreme ultraviolet lithography. The resist is based on heterometallic rings. From initial electron beam lithography studies, the resist performance demonstrated a resolution of 40-nm pitch but at the expense of a low sensitivity. To improve the sensitivity, we incorporated HgCl 2 and HgI 2 into the resist molecular design. This dramatically improved the resist sensitivity while maintaining high resolution. This improvement was demonstrated using electron beam and extreme ultraviolet lithography.
We report on the fabrication and characterization of high-resolution gratings with high efficiency in the extreme ultraviolet (EUV) and soft x-ray ranges using spin-on-carbon (SOC) underlayers. We demonstrate the fabrication of diffraction gratings down to 20 nm half-pitch (HP) on Si3N4 membranes with a bilayer of hydrogen silsesquioxane (HSQ) and spin-on-carbon and show their performance as a grating mask for extreme ultraviolet interference lithography (EUV-IL). High-resolution patterning of HSQ is possible only for thin films due to pattern collapse. The combination of this high-resolution resist with SOC circumvents this problem and enables the fabrication of high aspect ratio nanostructures. Rigorous coupled-wave analysis shows that the bilayer gratings exhibit higher diffraction efficiency than what is feasible with a grating made of HSQ. We also demonstrate a simple and accurate method to experimentally measure the diffraction efficiency of high-resolution gratings by measuring the relative ratio of the dose-to-clear curves of the photoresist. The measured diffraction efficiencies are in good agreement with the theoretically predicted values. Furthermore, we verify our calculations and measurements by printing line/space patterns in chemically amplified resists down to 10 nm HP with both HSQ and bilayer grating masks using EUV-IL. The improved diffraction efficiency of the bilayers is expected to have applications not only in gratings for interference lithography, but also in Fresnel zone plates and gratings for spectroscopy in the EUV and soft x-ray ranges.
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