Background: Inorganic resists show promising performances in extreme ultraviolet (EUV) lithography. Yet, there is a need for understanding the exact chemical mechanisms induced by EUV light on these materials. Aim: To gain knowledge on the EUV chemistry of inorganic resists, we investigate hybrid inorganic-organic molecular compounds, metal oxoclusters (MOCs). Their molecular nature allows for the monitoring of specific structural changes by means of spectroscopy and thus for the elucidation of the mechanisms behind pattern formation. Approach: We compare the sensitivity of MOCs based on Zr and Hf, and methacrylate ligands as EUV resists. The chemical and structural changes causing the solubility switch were investigated by ex situ x-ray spectroscopy, infrared spectroscopy, ultraviolet-visible spectroscopy, and grazing incidence x-ray scattering. Results: Higher sensitivity was detected for the Hf-based material, in line with its higher absorptivity. A small fraction of the carboxylate ligands is lost at doses that yield solubility contrast, whereas aggregation of the inorganic clusters was not observed. Conclusions: These results provide evidence that, although the mechanism of solubility switch in these materials starts with decarboxylation reactions, it mainly proceeds through cross linking of the organic shells instead of aggregation of the inorganic clusters.

The amount of absorbed light in thin photoresist films is a key parameter in photolithographic processing, but its experimental measurement is not straightforward. The optical absorption of metal oxide-based thin photoresist films for extreme ultraviolet (EUV) lithography was measured using an established methodology based on synchrotron light. Three types of materials were investigated: tin cage molecules, zirconium oxoclusters, and hafnium oxoclusters. The tin-containing compound was demonstrated to have optical absorption up to three times higher than conventional organic-based photoresists have. The absorptivity of the zirconium oxocluster was comparable to that of organic polymer-based photoresists, owing to the low absorption cross section of zirconium at EUV. The hafnium-containing resist shows about twice as high absorptivity as an organic photoresist, owing to the significantly higher absorbance of hafnium. From the chemical composition and crystal structure, the density of the spin-coated films was determined. Using the density of the films and the tabulated data for atomic cross section at EUV, the expected absorptivity of these resists was calculated and discussed in comparison to the experimental results. The agreement between measured and expected absorption was fairly good with some substantial discrepancies due to differences in the actual film density or to thickness inhomogeneity due to the spin coating. The developed method here enables the accurate measurement of the EUV absorption of the photoresists and can contribute to the further development of EUV resists and more accurate lithographic modeling.

A general, one-step patterning technique for colloidal quantum dots by direct optical or e-beam lithography. Photons (5.5–91.9 eV) and electrons (3 eV–50 kV) crosslink and immobilize QDs down to tens of nm while preserving the luminescent properties.

Tin-oxo cage materials are of interest for use as photoresists for EUV (Extreme-Ultraviolet) lithography (13.5 nm, 92 eV), owing to their large absorption cross section for EUV light. In this work we exposed an n-butyl tin-oxo cage dication in the gas phase to photons in the energy range 4-14 eV to explore its fundamental photoreactivity. At all energies above the onset of electronic absorption at ~5 eV (~250 nm) cleavage of tin-carbon bonds was observed. With photon energies >12 eV (<103 nm) photoionization can occur, leading to 3+ ions. Besides the higher charge promotion, butyl chain loss without electron ejection (leading to 2+ fragments) still occurs.

A fluorinated ligand in an extreme ultraviolet hybrid photoresist yields C–F bond dissociation upon exposure, thus enhancing its overall sensitivity.

The experimental measurement of the time-dependent absorption of photoresists at extreme ultraviolet wavelength is of great interest for the modeling of the lithographic process. So far, several technical challenges have made the accurate determination of the linear absorption coefficient and the Dill parameters nontrivial. In this work, we use a dedicated equipment and synchrotron light source to experimentally measure the transmittance of thin layers of photoresists on transparent silicon nitride membranes, and their thickness was measured with the spectroscopic ellipsometry. The absorption of negative tone photocondensed metal oxide photoresists based on Sn cage structures, and of Zr and Hf oxoclusters was measured and compared to the estimated values. It was found that tin based materials absorb considerably more light than conventional chemically amplified resists based on organic polymer. Hafnium-based materials have about twice absorption, while zirconium based are basically comparable to organic resists. Furthermore, the exposure kinetics of several chemically amplified resists with varying photoacid concentration and backbone polymer was studied. The rate of bleaching, described by the Dill parameter C, was measured and conclusions are drawn based on the specific resist formulation.

Photoresist materials are being optimized for the recently introduced Extreme Ultraviolet (EUV) photolithographic technology. Organometallic compounds are potential candidates for replacing the ubiquitous polymer-based chemically amplified resists. Tin (Sn) has...

Metal‐containing molecular hybrid compounds, such as metal oxoclusters (MOCs), are promising materials for extreme ultraviolet (EUV) lithography. The solubility, processability, and reactivity towards EUV photons in these compounds are mostly determined by the composition of their organic shells. Therefore, gaining molecular control on the composition of the shell is crucial to tune their lithographic performance of sensitivity, resolution, and line‐edge roughness. In this work, a new method to prepare MOCs that feature two types of carboxylate ligands is presented. In this method, amine‐functionalized resins are used for the purification step. By using this protocol, Ti‐ and Zr‐based MOCs with mixed‐ligands organic shells were synthesized. The new compounds showed clear differences in the processability and sensitivity as EUV resists compared to their analogues featuring only one type of ligand. The results validate this new synthetic approach for the preparation of custom‐made EUV resists towards better lithographic performance.