Directly Photopatternable Polythiophene as Dual-Tone Photoresist

Recent Advances in Metal-Oxide-Based Photoresists for EUV Lithography

Extreme ultraviolet lithography (EUVL) is a leading technology in semiconductor manufacturing, enabling the creation of high-resolution patterns essential for advanced microelectronics. This review highlights recent progress in inorganic metal-oxide-based photoresists, with a focus on their applications in EUVL. The unique properties of zinc-based, tin-oxygen, and IVB group inorganic photoresists are examined, showcasing their enhanced chemical reactivity and precise patterning capabilities. Key advancements include the development of zinc oxide and tin oxide nanoparticles, which demonstrate significant improvements in photon absorption and solubility under extreme ultraviolet exposure. Additionally, the review delves into the photochemical reactions of tin-oxygen clusters and the influence of various ligands on film density and cross-linking. The findings suggest that these inorganic photoresists not only improve photolithographic performance but also hold potential for broader applications, such as pyroelectric infrared sensors and 3D printing. Future research directions are outlined, including the optimization of process parameters, the exploration of new ligand and metal combinations, and the evaluation of the environmental benefits of inorganic photoresists over traditional organic ones. These advancements are poised to further enhance the resolution and patterning capabilities required for next-generation semiconductor devices.

Photoswitchable Solubility of Fullerene-Doped Polymer Thin Films

Controlling polymer film solubility is of fundamental and practical interest and is typically achieved by synthetically modifying the polymer structure to insert reactive groups. Here, we demonstrate that the addition of fullerenes or its derivatives (C₆₀ or phenyl-C61-butyric acid methyl ester, PCBM) to polymers, followed by ultraviolet (UV) illumination can change the film solubility. Contrary to most synthetic polymers, which dissolve in organic solvents but not in water, the fullerene-doped polymer films (such as polystyrene) can dissolve in water yet remain stable in organic solvents. This photoswitchable solubility effect is not observed in either film constituents individually and is derived from a synergy of photochemistries. First, polymer photooxidation generates macroradicals which cross-link with radical-scavenging PCBM, thereby contributing to the films' insolubility in organic solvents. Second, light exposure enhances polymer photooxidation in the presence of PCBM via the singlet oxygen pathway. This results in polymer backbone scission and formation of photooxidized products which can form hydrogen bonds with water, both contributing to water solubility. Nevertheless, the illuminated doped polymer thin films are mechanically robust, exhibiting significantly increased modulus and density compared to their pristine counterpart, such that they can remain intact even upon sonication in conventional organic solvents. We further demonstrate the application of this solubility-switching effect in dual tone photolithography, via a facile, economical, and environmentally benign solution-processing route made possible by the photoactive nature of polymer-PCBM thin films.

Universal three-dimensional crosslinker for all-photopatterned electronics

All-solution processing of large-area organic electronics requires multiple steps of patterning and stacking of various device components. Here, we report the fabrication of highly integrated arrays of polymer thin-film transistors and logic gates entirely through a series of solution processes. The fabrication is done using a three-dimensional crosslinker in tetrahedral geometry containing four photocrosslinkable azide moieties, referred to as 4Bx. 4Bx can be mixed with a variety of solution-processable electronic materials (polymer semiconductors, polymer insulators, and metal nanoparticles) and generate crosslinked network under exposure to UV. Fully crosslinked network film can be formed even at an unprecedentedly small loading, which enables preserving the inherent electrical and structural characteristics of host material. Because the crosslinked electronic component layers are strongly resistant to chemical solvents, micropatterning the layers at high resolution as well as stacking the layers on top of each other by series of solution processing steps is possible.

To enable the large-area manufacture of solution-processed organic electronics, direct photocrosslinking processes has emerged as a promising technology solution. Here, the authors report an efficient universal crosslinking agent for micropatterning of stacked multi-layered organic electronics.