Effect of Metal Oxide Deposition on the Sensitivity and Resolution of E-Beam Photoresist

Organic-inorganic hybrid resists offer a solution to the issue of low sensitivity in organic photoresists like poly(methyl methacrylate) (PMMA). In this study, an organic-inorganic hybrid resist (PMMA-Al₂O₃) with high sensitivity and resolution was prepared by depositing metal oxides into PMMA using sequential infiltration synthesis (SIS). PMMA-Al₂O₃ was prepared by precisely controlling the number of SIS cycles (<23) in various atomic layer deposition (ALD) processes to facilitate the growth of metal oxides within PMMA pores. The impact of different metal oxide contents and distributions on the sensitivity and resolution of electron beam exposure was investigated. Numerical simulations of the deposit formation within the PMMA pores were performed by solving the pore-scale ALD governing equations fed by the reactor-scale boundary conditions. The gradual pore constriction with SIS cycles was predicted and validated by the experimental charaterizations. The results demonstrated that PMMA-Al₂O₃ was prepared using 20 SIS cycles, which corresponds to the numerically predicted occurrence of the pore blockage at the upper region of the PMMA layer, exhibiting optimal electron beam (e-beam) resolution while enabling line exposure with a width of 50 nm. While the corresponding sensitivity was lower than those of the samples prepared using 5 and 10 SIS cycles, the degradation of the PMMA structure was affected under exposure. The pattern transfer results showed that the line width was well retained for 20 cycles of deposition because of the high etching resistance of Al₂O₃. This research is expected to provide an effective approach to developing next-generation high-performance photoresists.