The development of highly sensitive resists containing tin, which has a large extreme ultraviolet (EUV) absorption cross section, has recently attracted considerable attention in EUV lithography. The effective utilization of secondary electrons is required for the development of high-performance resists. It is important to design resist materials on the basis of the mechanism of radiation chemical reactions. In this study, the radiation-induced reactions of tetraphenyltin (TPSn), triphenylsulfonium triflate (TPS-Tf), and the copolymer of triphenyl(4-vinylphenyl) stannane (TPSnSt) and 4-methacryloxyphenyldiphenylsulfonium triflate (MAPDPS-Tf) were investigated by electron pulse radiolysis and -radiolysis in controlled reaction systems. The decomposed products were analyzed by high-performance liquid chromatography (HPLC). The G values of decomposed products were determined. For the copolymer, the holes generated by ionizing radiations moved to Sn units and electrons moved to TPS-Tf units. The tin complex side chain decomposed, producing benzene after hole transfer.

Since 2019, the extreme ultraviolet lithography (EUVL) has been applied to the high-volume production of devices. For further scaling, high-numerical aperture (NA) tool and resist materials applicable to high-NA EUVL are required. However, there are no resists applicable to high-NA EUVL. These days, resist materials containing Sn whose EUV absorption cross section is particularly high are attracting much attention. In this research, radiation-induced reaction mechanisms of Sncomplex- side-chain polymers were investigated to obtain the guidelines of material design.