Advances in extreme ultraviolet (EUV) photolithography require the development of next-generation resists that allow high-volume nanomanufacturing with a single nanometer patterning resolution. Organotin-based photoresists have demonstrated nanopatterning with high resolution, high sensitivity, and low-line edge roughness. However, very little is known regarding the detailed reaction mechanisms that lead to radiation-induced solubility transitions. In this study, we investigate the interaction of soft X-ray radiation with organotin clusters to better understand radiation-induced chemistries associated with EUV lithography. Butyltin Keggin clusters (β-NaSn13) were used as a model organotin photoresist, and characterization was performed using ambient-pressure X-ray photoelectron spectroscopy. The changes in relative atomic concentrations and associated chemical states in β-NaSn13 resists were evaluated after exposure to radiation for a range of ambient conditions and photon energies. A significant reduction in the C 1s signal versus exposure time was observed, which corresponds to the radiation-induced homolytic cleavage of the butyltin bond in the β-NaSn13 clusters. To improve the resist sensitivity, we evaluated the effect of oxygen partial pressure during radiation exposures. We found that both photon energy and oxygen partial pressure had a strong influence on the butyl group desorption rate. These studies advance the understanding of radiation-induced processes in β-NaSn13 photoresists and provide mechanistic insights for EUV photolithography.
Keywords: APXPS; EUV lithography; XAS; nanocluster; organotin-based photoresist.