Structurally tunable colorless ionic-type negative-tone photosensitive polyimides with high transparency for i-line photopatterning

With the rapid development of related fields in the semiconductor industry, photosensitive polymers have become an important fundamental material that restricts the manufacturing and quality of integrated circuits and chips. Among various materials, photosensitive polyimides (PSPIs), as a potential alternative to traditional photosensitive materials, have attracted much attention due to their excellent comprehensive performance and the ability to directly serve as a component of micro-nano structures of semiconductor devices. However, traditional polyimide-based photosensitive materials usually exhibit intense yellowing phenomenon due to the formation of charge transfer complexes (CTCs), which adversely affects the sensitivity, resolution and contrast of the photosensitive patterns. With the expanding demand for colorless and highly transparent application fields, how to effectively reduce the CTCs effect while maintaining the photosensitive activity has become an urgent issue to be addressed. Herein, by adopting the strategy of adjusting the diamine structures, there prepared three kinds of polyamic acid precursors by incorporating highly electronegative elements, disrupting the continuous conjugated structures, or introducing cycloaliphatic groups. Subsequently, 2-(dimethylamino)ethyl methacrylate was post-polymerization modified as photosensitive group through the ionic interaction between the carboxyl groups and the tertiary amines. A series of highly transparent polyimides could be finally obtained after thermal imidization. These PSPIs with the ability to be cured under 365 nm ultraviolet light exhibited potential to be processed into striped patterns with a resolution of 10 μm, while maintaining a visible light transmittance of approximately 90%. These high-performance PSPIs are expected to be further applied to various scenarios such as electronic displays, advanced packaging materials, micro-optical devices and so on in the future.