The improved photosensitivity of photosensitive polyimides containing o‐nitrobenzyl ether groups induced by the addition of photoacid generator. Issue 4 (18th January 2021)

• Record Type: Journal Article
• Authors: Song, Gwang‐Sik; Heo, Youn‐Jung; Baek, Jeong Ju; Lee, Hyosun; Bae, Geun Yeol; Choi, Kyung Ho; Koh, Won‐Gun; Shin, Gyojic
• Is Part Of: Journal of polymer science. Volume 59:Issue 4(2021)
• Page Start: 340
• Page End: 352
• Publication Date: 2021-01-18
• Subjects: micropatterning -- photoacid generator -- photosensitive polymers -- polyimide -- positive photoresist; Polymers -- Periodicals; Polymerization -- Periodicals; Polymerization; Polymers; Periodicals; 547.7
• DOI: 10.1002/pol.20200851
• Languages: English
• ISSNs: 2642-4150

Abstract

Abstract: In this article, photosensitive polyimides (PSPIs) with photosensitive groups, o ‐nitrobenzyl ether groups (Nb), were successfully synthesized based on 2, 2′‐dihydroxy benzophenone‐3, 3′, 4, 4′‐tetracarboxylic dianhydride and on diamine containing ethylene glycol chains (ODA). Also, a series of polyimide (PI), ODA‐1‐PI, ODA‐3‐PI, and ODA‐5‐PI with a number of ethylene glycol chains of 1, 3, and 5 were prepared to investigate the relationship between structure and solubility. Interestingly, ODA‐5‐PI, which possesses a large number of ethylene glycols, exhibited the most excellent solubility. Therefore, due to the good solubility of ODA‐5‐PI in organic solvents and alkaline solutions, a PSPI, poly(1, 4‐phenyleneoxy‐3, 6, 9, 12, 15‐pentaoxaoctane‐1, 4‐phenylene‐2, 2′‐di[2‐nitrobenzyloxy]benzophenone‐3, 3′, 4, 4′‐tetracarboxdiimide), named ODA‐5‐PSPI, was synthesized by linking Nb, which is a photosensitive group. Aiming at producing positive tone patterns, the synthesized ODA‐5‐PSPI was exposed to UV irradiation and then to a post‐exposure bake. Afterward, it was developed using a 2.38 wt% tetramethylammonium hydroxide solution. Furthermore, a photoacid generator (PAG) was additionally incorporated for a micropatterning process. Notably, in the presence of the PAG, the photocleavage of ODA‐5‐PSPI occurred not only by the intramolecular rearrangement of Nb but also by its hydrolysis reaction. As a result, due to the synergistic effect of photocleavage, the micropatterning of ODA‐5‐PSPI with PAG could be clearly obtained with less energy (2.0 J/cm 2 ) compared with that without PAG (3.6 J/cm 2 ). Therefore, through the addition of PAG, the photosensitivity was improved by 45%. Abstract : A series of photosensitive polyimides (PSPI) are synthesized, and their photosensitivities are improved by adding PAG. Through the incorporation of PAG, acid‐catalyzed ether cleavage as well as intramolecular rearrangement, which is a conventional photoreaction, occur simultaneously. Due to the synergistic effect of intramolecular rearrangement and acid‐catalyzed cleavage, the photosensitivity is improved by 45%.