Effect of Ambient Conditions on Radiation-Induced Chemistries of a Nanocluster Organotin Photoresist for Next-Generation EUV Nanolithography

Abstract

Solution-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 nextgeneration 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-NaSn 13 ) 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-NaSn 13 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-NaSn 13 thin films in multiple ambients to study the chemistry that occurs after a postexposure bake (PEB). The β-NaSn 13 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-NaSn 13 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-NaSn 13 model resist and provide mechanistic insights for EUV lithography processing with organometallic nanomaterials.

Organoiodine Functionality Bearing Resists for Electron-Beam and Helium Ion Beam Lithography: Complex and Sub-16 nm Patterning

“…There have been many different ways to improve resist performance through structure engineering. Among several approaches that have been adopted by different research groups across the globe to improve resist performance in terms of sensitivity and resolution, incorporation of inorganics or organohalo-functionality into resist architecture has been very successful. − Integration of inorganics into a resist network has helped in improving resolution, etch resistance, and sensitivity. , In recent times, metal–organic materials (both molecular and macromolecular) have been found to be quite promising resist systems in the current scenario of advanced IC technology. − Similarly, incorporation of halogens into the resist matrix has been very successful in developing high performance resists with improved properties. To mention a few, Wilson and co-workers reported the positive impact of the inclusion of fluorinated functionality in resist architecture on the backbone-scission efficiency and sensitivity .…”

Molecular bixbyite-like In12-oxo clusters with tunable functionalization sites for lithography patterning applications

“…Nanoscale patterning enables ongoing miniaturization in dense integrated circuit technology to meet expectations predicted by the Moore's law, 15,16 and extreme ultraviolet (EUV) lithography as promising next-generation lithography technology requires metal-containing patterning materials of large absorption cross-section characteristics for more efficient utilization of EUV photons. [17][18][19] To date, a small amount of metal complexes of Sn, [20][21][22][23] Sb, 24 Hf, 25 Zr, 26 Ti, 27 Zn, 28 Pt and Pd 29 have set foot into this field. Interestingly, in terms of practical application, the cage-like Sn-oxo cluster is exclusively available in realizing EUV lithography in industry, which indicate that metal-oxo clusters as the patterning material do have significant potential in nanolithography.…”

Non-alkyl tin-oxo clusters as new-type patterning materials for nanolithography

“…Because alkyltin-oxo clusters dominate the known TOCs, the present research on TOC lithography mainly focuses on two organotin complexes of butyl-Sn 12 and butyl-tin Keggin (β-NaSn 13 ). The influence of counter ions [18], process condition [19], and environmental factors [20][21] on the patterning performance of these two alkyltin-oxo clusters has been studied in detail. However, from the perspective of structural chemistry, the relatively stable terminated Sn-C bond of this kind of organotin-oxo clusters greatly limits their surface modification [22][23].…”