The role of the organic shell in hybrid molecular materials for EUV lithography

Abstract

As EUV lithography is being introduced into the market, the need for resists that can satisfy the exigent requirements of sensitivity, resolution, and line-edge roughness requires the development of guidelines for new generations of materials. In this work, we aim for gaining more understanding on the contribution of the organic components in inorganic-organic hybrid molecular resists to their sensitivity. A method to investigate the effect of specific functionalities on the sensitivity of metal oxo clusters is presented, which consists in the "doping" of the methacrylate shell through the introduction of fluorinated, iodinated and extended aromatic ligands. By introducing each of these functionalities in small ratios to the methacrylate ligand (1:11 and 2:10) the main chemical properties of the materials (solubility and molecular packing in the thin film) are expected to be unaltered. Our investigations show that the sensitivity is enhanced in the presence of halogens and drastically decreased when extended aromatic compounds are introduced. The trends are uncorrelated with the absorptivity estimated for each material, which seems to indicate that the doping functionalities might interfere with the cross-linking of the methacrylate ligands or introduce new chemical pathways. Our results indicate that specific organic functionalities can be used to tune the reactivity of hybrid compounds for EUV light by introducing them in doping amounts, thus preserving the processability of the initial material.

Stability studies on a sensitive EUV photoresist based on zinc metal oxoclusters

“…17 These performance targets require research on new materials that incorporate elements with high EUV photon absorption cross-sections and, at the same time, are composed of small units consistent with future resolutions targets. 13,[18][19][20] Metal oxoclusters are hybrid molecular compounds 10,21 and hold great potential as resist platforms for EUV lithography applications. By choosing the right metalcomponent, they can meet the desired properties for EUV photon absorption while offering intrinsically small and homogeneous size (monodisperse) due to their molecular nature.…”

“…The organic ligands surrounding the inorganic EUV-absorbing core are envisioned as the main factor defining the solubility properties. 21 In addition, the organic ligands play a major role in the reactivity of the material. The organic shell is thus responsible for the switching of the solubility properties of the material upon EUV exposure, which enables patterning.…”

Fluorine-Rich Zinc Oxoclusters as Extreme Ultraviolet Photoresists: Chemical Reactions and Lithography Performance

“…Previous studies have shown that introduction of a – CF 3 group at the α position decreases the rate of radical homopolymerization of the TFMA unit. , Different molecular packing of the oxoclusters in Zn­(TFMA) compared to its analogue Zn­(MA)­(TFA) or a reduced ratio of the solubility rates of the unexposed and exposed regions in the developer of choice can also contribute toward this observed decrease in the sensitivity. Therefore, incorporation of more fluorine does not always directly translate into better EUVL performance of the photoresist, in contrast to the previous reported studies. , Further, contrast curve studies demonstrated that postexposure bake (PEB) applied at 120 °C/30 s under ambient conditions led to a further slight decrease in the sensitivity (also see section ). Spectroscopic studies to identify the chemical changes induced by PEB in the oxocluster were also carried out, and are discussed in section .…”

“…Therefore, incorporation of more fluorine does not always directly translate into better EUVL performance of the photoresist, in contrast to the previous reported studies. 23,40 Further, contrast curve studies demonstrated that postexposure bake (PEB) applied at 120 °C/30 s under ambient conditions led to a further slight decrease in the sensitivity (also see section 3.4). Spectroscopic studies to identify the chemical changes induced by PEB in the oxocluster were also carried out, and are discussed in section 3.7.…”

“…Hence, its incorporation, along with the metals, in the resist material has the potential to increase the EUV absorbance. Moreover, some studies have demonstrated an overall enhanced EUV lithography performance upon the incorporation of fluorine in the photoresist material. ,− …”