Hexaarylbiimidazole-based polyurethane positive photoresists for UV lithography
Authorea (Authorea)(2022)
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.
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Key words
polyurethane,positive photoresists,uv,hexaarylbiimidazole-based
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