Jianghao Zhan

Directed self-assembly (DSA) of polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA) has garnered substantial interest for semiconductor manufacturing, particularly for fabricating contact holes and vias. However, its application is limited by the low etch selectivity between the PS and PMMA domains. Here, we report an acid-responsive block copolymer, PS-N=CH-PMMA, incorporating a Schiff base (-N=CH-) linkage between the two blocks to impart acid sensitivity. The copolymer is synthesized via aldehyde-terminated PMMA (PMMA-CHO) precursors and is fully compatible with conventional thermal annealing workflows used for PS-b-PMMA. Uniform thin films with vertically oriented cylindrical domains were obtained, which could be directly converted into high-fidelity PS masks through acetic acid immersion without UV exposure. Graphoepitaxial DSA in 193i pre-patterned templates produced shrink-hole patterns with reduced critical dimension (CD) and improved local CD uniformity (LCDU). The shrink-hole CD was tunable by varying PMMA-CHO molecular weights. XPS confirmed selective cleavage of Schiff base linkages at the PS/PMMA interface under acidic conditions, while Ohta–Kawasaki simulations indicated interfacial wetting asymmetry governs etch fidelity and residual layer formation. Pattern transfer into TEOS layers was achieved with minimal CD loss. Overall, the acid-cleavable BCP enables scalable, high-fidelity nanopatterning with improved etch contrast, tunable process windows, and seamless integration into existing PS-b-PMMA lithography platforms.

Graphoepitaxial directed self-assembly (DSA) of block copolymers (BCPs) has emerged as a promising strategy for sub-30 nm line spacing patterning in semiconductor nanofabrication. Among the available BCP systems, polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA) has been extensively utilized due to its well-characterized phase behavior and compatibility with standard lithographic processes. However, achieving a high-fidelity pattern with PS-b-PMMA remains challenging, owing to its limited etch contrast and reliance on UV-assisted degradation for PMMA removal. In this study, we report the synthesis of an acid-cleavable lamellar BCP, PS-N=CH-PMMA, incorporating a dynamic Schiff base (-N=CH-) linkage at the junction. This functional design enables UV-free wet etching, allowing selective removal of PMMA domains using glacial acetic acid. The synthesized copolymers retain the self-assembly characteristics of PS-b-PMMA and form vertically aligned lamellar nanostructures, with domain spacings tunable from 36.1 to 40.2 nm by varying the PMMA block length. When confined within 193i-defined trench templates with a critical dimension (CD) of 55 nm (trench width), these materials produced well-ordered one-space-per-trench patterns with interline spacings tunable from 15 to 25 nm, demonstrating significant line spacing shrinkage relative to the original template CD. SEM and FIB-TEM analyses confirmed that PS-N=CH-PMMA exhibits markedly improved vertical etch profiles and reduced PMMA residue compared to PS-b-PMMA, even without UV exposure. Furthermore, Ohta–Kawasaki simulations revealed that trench sidewall angle critically influences PS distribution and residual morphology. Collectively, this work demonstrates the potential of dynamic covalent chemistry to enhance the wet development fidelity of BCP lithography and offers a thermally compatible, UV-free strategy for sub-30 nm nanopatterning.

Polyurethane nanomicelle is a promising functional drug delivery system. In this work, the polyurethane (P3-PU) was synthesized from PLGA₁₂₀₀-PEG₁₄₅₀-PLGA₁₂₀₀ (P3, a thermosensitive and biodegradable triblock copolymer) and L-lysine ester diisocyanate (LDI). Then, reactive benzaldehyde was further imported to terminate P3-PU to obtain benzaldehyde modified polyurethane (P3-PUDA). The micelles, temperature-sensitive P3-PU nanomicelle and P3-PUDA nanomicelle, were systematically investigated, including the size, stability, temperature sensitivity, drug loading and release behavior, cytotoxic on human hepatocytes (L02), and inhibitory effect on human hepatocellular carcinoma cells (HepG2). The results show the thermosensitive behavior of the micelles can be adjusted by the terminal group. The polyurethane micelles with a uniform size between 20 nm and 30 nm showed excellent stability and good biocompatibility to L02 cells. Besides, in vitro experiments showed that Dox-loaded P3-PUDA micelles exhibited faster and higher release rate at 37 °C and better inhibitory effect on HepG2 than the Dox-loaded P3-PU micelles. Moreover, the achieved benzaldehyde modified polyurethanes also provides various possibilities to adjust further to enlarge its applications. Therefore, the polyurethane micelles will have great potential in the field of drug carriers. Graphical abstract