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Effect of Ambient Conditions on Radiation-Induced Chemistries of a Nanocluster Organotin Photoresist for Next-Generation EUV Nanolithography
journal contribution
posted on 2020-03-04, 23:13 authored by J. Trey Diulus, Ryan T. Frederick, Danielle C. Hutchison, Igor Lyubinetsky, Rafik Addou, May Nyman, Gregory S. HermanSolution-based
organometallic nanoclusters are unique nanoscale
precursors due to the ability to precisely control their size, shape,
structure, and assembly. The interaction of extreme ultraviolet (EUV)
or X-ray photons with these organometallic nanoclusters can result
in processes that can lead to a change in solubility. This makes these
materials prime candidates for next-generation photoresists for EUV
nanolithography. In this study, we investigate the interaction of
X-ray radiation with a charge neutral, sodium templated, butyl-tin
Keggin (β-NaSn13) nanocluster. This nanocluster is
used as a model EUV photoresist to better understand the radiation
induced solubility transition. Ambient pressure X-ray photoelectron
spectroscopy (AP-XPS) was used to characterize the β-NaSn13 thin films, where Sn 3d, O 1s, and C 1s core levels were
measured under a range of ambient conditions, including ultrahigh
vacuum and 1 mbar of oxygen, water, methanol, or nitrogen. A photon
dose array was obtained for each ambient condition to determine their
effect on the photon induced chemistries which result in the solubility
transition. The resulting contrast curves indicate that an oxygen
ambient significantly reduces the required photon dose for the solubility
transition relative to UHV, while all other ambients increase the
required photon dose for the solubility transition relative to UHV.
We performed in situ XPS after postexposure annealing β-NaSn13 thin films in multiple ambients to study the chemistry that
occurs after a postexposure bake (PEB). The β-NaSn13 thin films retained a significant amount of aliphatic carbon following
the PEB in all the ambients we studied. On the basis of our studies,
we propose that the solubility transition for β-NaSn13 thin films occurs through radical hydrogen abstraction and radical–radical
coupling reactions. These studies further improve the understanding
of photon induced chemistries in a β-NaSn13 model
resist and provide mechanistic insights for EUV lithography processing
with organometallic nanomaterials.
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Keywords
photon dose arrayNext-Generation EUV Nanolithography Solution-based organometallic nanoclustersXPSpostexposure annealing β- NaSn 13PEBUHVsolubility transitionNanocluster Organotin PhotoresistAP-XPSmodel EUV photoresistphoton doseβ- NaSn 13ambientfilmEUV lithography processingAmbient pressure X-ray photoelectron spectroscopyβ- NaSn 13 model
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