Shuangqing Wang

A series of nonchemically amplified resists based on dibenzothiophenium-functionalized polystyrene (PSSDx, x is the loading ratio of the sulfonium, x = 0.5, 0.7, 1.0) were designed and prepared. The lithographic performance of PSSDx resists was evaluated by electron beam lithography (EBL). The PSSD0.7 resist exhibited superior resolution (20 nm) compared with PSSD0.5 (25 nm) and PSSD1.0 (22 nm) resists under the same EBL processing conditions. By reducing the film thickness to 25 nm, the PSSD0.7 resist resolved the 18, 16, and 15 nm L/S patterns at doses of 1200–1500 μC cm–2 with LERs of 3.0–3.3 nm, demonstrating a superior comprehensive performance to the previously reported triphenylsulfonium-based PSTS0.7 model resist (18 nm L/S at 2400 μC cm–2). The PSSD0.7 resist was further investigated by extreme ultraviolet lithography (EUVL), achieving an impressive 14 nm pattern with a line edge roughness (LER) of 3.0 nm at an exposure dose of 148 mJ cm–2. The quartz crystal microbalance (QCM) analyzer confirms that the solubility behavior of PSSD0.7 and PSTS0.7 model resist films is not the main reason for the difference in sensitivity. The calculation and photochemical kinetics study suggest that the significantly reduced bond energy and the enhanced efficiency and rate of the photochemical reaction with the dibenzothiophenium group play a key role in the excellent lithographic performances of the PSSD0.7 resist.

Aryl sulfonate ester modified polystyrene with different substituents (X-SEPS, X = H-, MeO-, and CN-) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The excellent thermal stability and film-forming capability of these three polymers suggest that they can satisfy the lithography process and are candidates for resist materials. The comparative electron beam lithography (EBL) demonstrates that the three (H-SEPS, MeO-SEPS and CN-SEPS) resists exhibit different EBL performances. The calculation of the bond energies for model compounds suggests that the influence of substituent groups on the bond energy is not the main reason for their differences in sensitivity. A fully automated dissipative quartz crystal microbalance (QCM) analyzer confirms that the influence of the substituent groups on the solubility behavior of the resist films in developers leads to different photolithographic performances. H-SEPS resist exhibits a better comprehensive performance than that of MeO-SEPS and CN-SEPS resists, achieving an 18 nm line/space (L/S) pattern and a 10 nm line/4 space (L/4S) semi-dense pattern by EBL at doses of 3200 and 2800 μC cm^-2, respectively. Further extreme ultraviolet lithography (EUVL) demonstrates the capability of H-SEPS resist to form 22 nm half-pitch (HP) patterns. The detailed study of the photochemical reaction and patterning mechanism suggests that the decomposition of sulfonate ester groups into polar sulfonic acid groups, along with a rearrangement, leads to a solubility switch of resist films in the developer.

Electron beam lithography (EBL) and extreme ultraviolet lithography (EUVL) have been continuously improved and applied in semiconductor and biomedical device manufacturing. With the development of biomedical nanodevices, the demand for biodegradable, and environmentally friendly materials is growing. Some biocompatible photoresists have been reported, and their sensitivity, resolution, and line edge roughness need to be further improved. In this work, porphyrin derivatives (H₂TP‐4Epoxy and CuTP‐4Epoxy) are introduced for EBL and EUVL. Owing to their smaller sizes and higher EUV absorptivity compared to traditional polymer photoresists, CuTP‐4Epoxy shows good resolution and etch resistance. As a result of EBL studies, 18 nm line/space patterns have been achieved at a dose of 1014 µC cm⁻². Meanwhile, 20 nm dense patterns are also achieved using EUVL at a dose of 88.8 mJ cm⁻², revealing the great potential of this approach for high resolution patterning. Etching experiments show an etch selectivity for silicon of 11.7, significantly higher than some of commercial photoresists. Biocompatibility experiments show that metalloporphyrin photoresist have potential applications in the fabrication of chips that are biocompatible with living organisms. This work demonstrates the structural advantages of porphyrin derivatives as high‐resolution biocompatible photoresist materials, inspiring future exploration of metalloporphyrin materials for advanced lithography and biocompatible nanodevices.

A non-chemically amplified molecular resist based on γ-hydroxy carboxylate and triphenylsulfonium groups was developed for EBL and EUVL, resolving 22 and 20 nm patterns at low exposure doses of 160 μC cm ⁻² and 13.3 mJ cm ⁻² , respectively.

Novel t-butyloxycarbonyl-protected molecular glass photoresists with pyrene as the core (Pyr-8Boc and Pyr-4Boc) were designed and synthesized. The thermal stability and film-forming ability were measured to assess their applicability for lithography. Pyr-Boc (Pyr-8Boc and Pyr-4Boc) photoresists were evaluated by high-resolution electron beam lithography (EBL), acting as chemically amplified resists. Pyr-4Boc showed a better lithography performance, achieving 25 nm line/space patterns at the dose of 50 μC/cm². Under SF₆/O₂ plasma, the etch selectivity of the Pyr-4Boc photoresist to silicon was 12.3, which is twice that of the commercially available poly(methyl methacrylate) photoresist (950 k). The lithography mechanism of EBL was further investigated. Theoretical calculations of HOMO/LUMO orbital energies, cyclic voltammetry, and fluorescence quenching experiments were conducted to confirm the electron-transfer reactions between the Pyr-Boc and photoacid generator. The study provides an option of high sensitivity and etch-resistant photoresist for EBL.

A non-chemically amplified resist (n-CAR) based on iodonium functionalized polystyrene (PSNA _0.4 ) was developed for extreme ultraviolet lithography, achieving 22 nm L/S patterns at a dose of 90.8 mJ cm ⁻² , underscoring its high sensitivity for n-CARs.