DFT Study on CO2- and H2O-Enhanced Solubility Contrast in Tin-Oxo Cage Photoresists
Fang-Ling Yang1, Zong-Biao Ye1, Dongxu Yang2
1Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, No. 24 South Section 1, Yihuan Road, Chengdu 610065, People's Republic of China.
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The tin-oxo cage is a promising photoresist due to tin's large extreme ultraviolet (EUV) photon cross-section and small size. CO2 and H2O play a crucial role in increasing the solubility contrast of tin-oxo cages in deep ultraviolet (DUV) and EUV lithography. However, the internal reaction mechanisms remain largely unknown. This work systematically investigated the cleavage of carbon-tin bonds in tin-oxo cages by density functional theory (DFT) upon diverse irradiation (DUV and EUV). Subsequently, the interactions of the resulting intermediates with CO2/H2O (or their hybrid) were examined, revealing that hydroxyl compounds (from the dissociation of H2O) serve as pivotal precursors to trigger new cross-linking reactions (forming Sn-O-Sn and Sn-OCO-Sn products) and enhance the solubility switch. These theoretical results provide insight into the atomic-scale mechanisms of small molecules improving photoresist properties, offering new perspectives for the design and optimization of novel photoresist materials.
