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Hexaarylbiimidazole-based polyurethane positive photoresists for UV lithography
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  • Peng-Fei Luo,
  • Shi-Li Xiang,
  • Ying-Yi Ren,
  • Ling-Yan Peng,
  • Jun-Dan Huang,
  • Pan Hong,
  • Qi Yu,
  • Chong Li,
  • Ming-qiang Zhu
Peng-Fei Luo
Huazhong University of Science and Technology
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Shi-Li Xiang
Huazhong University of Science and Technology
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Ying-Yi Ren
Huazhong University of Science and Technology
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Ling-Yan Peng
Huazhong University of Science and Technology
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Jun-Dan Huang
Huazhong University of Science and Technology
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Pan Hong
Huazhong University of Science and Technology
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Qi Yu
Huazhong University of Science and Technology
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Ming-qiang Zhu
Huazhong University of Science and Technology

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Abstract

Photochromic hexaarylbiimidazoles (HABIs) enable reversible transformation between HABI and triphenylimidazole radicals (TPIRs) upon UV light irradiation, which have been applied in photo-patterning, super-resolution imaging, photoinduced self-healing materials and photomechanical hydrogels. Here, we designed and prepared a novel kind of polyurethane (PU) photoresist based on photo-cleavable HABI cross-linkers (HABI-PU), linear PU backbone and additive tert-butylhydroquinone (TBHQ) radical quencher. Upon UV light irradiation, the C-N bond inside HABI unit is broken, causing the transformation of HABI into two TPIRs which are subsequently quenched by TBHQ. Therefore, the cross-linking points of HABI-PU in UV irradiation area were broken, forming flexible PU polymer chains with declined molecular weight, which can be dissolved in developer. HABI-PU films show excellent photosensitivity as a positive photoresist in photolithography. The reaction mechanism between HABI and TBHQ was studied by UV-vis absorption spectra, electron paramagnetic resonance (EPR), mass spectra and nuclear magnetic resonance spectra. The lithographic patterns were characterized through metallurgical microscope and scanning electron microscope with a resolution at about 5 µm.