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Silk protein is being increasingly introduced as a prospective material for biomedical devices. However, a limited locus to intervene in nature-oriented silk protein makes it challenging to implement on-demand functions to silk. Here, we report how polymorphic transitions are related with molecular structures of artificially synthesized silk protein and design principles to construct a green-lithographic and high-performative protein resist. The repetition number and ratio of two major building blocks in synthesized silk protein are essential to determine the size and content of β-sheet crystallites, and radicals resulting from tyrosine cleavages by the 193 nm laser irradiation induce the β-sheet to α-helix transition. Synthesized silk is designed to exclusively comprise homogeneous building blocks and exhibit high crystallization and tyrosine-richness, thus constituting an excellent basis for developing a high-performance deep-UV photoresist. Additionally, our findings can be conjugated to design an electron-beam resist governed by the different irradiation-protein interaction mechanisms. All synthesis and lithography processes are fully water-based, promising green lithography. Using the engineered silk, a nanopatterned planar color filter showing the reduced angle dependence can be obtained. Our study provides insights into the industrial scale production of silk protein with on-demand functions.

In extreme ultraviolet lithography (EUVL), the non-uniformity of patterned surface roughness of contact holes results in pattern failures such as bridging or missing holes, which affects production yield. In this study, we propose a multiscale model for reproducing 10–35 nm contact hole patterns based on the photo-chemical reactions in a photoresist (PR). To determine the heterogeneous spatial distribution of the resist components at the mesoscopic level, we employed a coarse-graining (CG) strategy for the PR. Additionally, we constructed a statistical model to obtain the novel acid/base distributions using existing MD data. The chemical reaction kinetics were reproduced via the finite difference method (FDM). We predicted resulting hole-patterned surfaces according to the target hole size. The variability in interfacial surface roughness among the holes, which is quantified by local critical dimension uniformity (LCDU), increased with decreasing target hole size, which is consistent with experimental reports. By investigating the photochemistry in the PR at the molecular level, we confirmed that the decrease in the chemical gradient due to the increase in relative acid diffusivity to hole size caused the LCDU and hole-failure probability trends. The diffusivity control enhanced this interpretation further, resulting in mitigation of CD variability in the 10 nm contact holes.

In extreme ultraviolet lithography (EUVL), a photoacid generator (PAG) blended photoresist (PR) is used to transfer the blueprint from the mask to the wafer. The photoacids are predominantly activated by photo-triggered secondary electron attachment in EUVL, which is distinct from the direct electron excitation of PAG in conventional deep ultraviolet resists. However, uncontrolled acid dispersion causes excessive deprotection and serious damage to the residual pattern. A quencher base compound was introduced in the PR to confine the acid diffusion, but the molecular level description of the acid ↔ quencher interaction and the resulting influence on the pattern image remains elusive. We examine the quencher effect that neutralizes the acid and impedes the deprotection in the masked region, leading to the enhancement of the line edge roughness (LER) of the pattern. In addition, we investigated the loading effect of the quencher and predicted the optimal concentration of the quencher for the best LER, consistent with experimental reports. The LER optimum along the quencher concentration is interpreted by the reciprocal relationship between the acid-blocking effect at the line edge of the pattern (positive) and the acid trapping behavior in the exposure domain (negative). The variations in the deprotection homogeneity clearly demonstrate the negative impact of the acid trap phenomenon on the chemical reaction according to the quencher's loading. In multiscale modeling, PAG dissociation energy curve calculated from density functional theory (DFT) is applied to molecular dynamics (MD) simulation to reproduce the indirect photochemical activation in EUVL. The sequential multiscale framework (DFT-MD-finite difference method) also reproduces acid/base diffusion, neutralization, deprotection kinetics, and pattern morphology in EUV resist at the molecular level.

A photoresist (PR) that can be fabricated in sub-10 nm patterns with the introduction of extreme ultraviolet lithography (EUVL) is a key requirement for transistor downsizing. To produce such ultra...

Extreme ultraviolet (EUV) lithography is one of the most promising techniques in the semiconductor industry to enhance resolution, line edge roughness (LER) and sensitivity of chemically amplified resist (CAR) pattern. Post exposure bake (PEB) process, a major process in EUV lithography, has been studied by experimental approach, but they are confronted by time-consuming tasks for massive combinatorial research. Also, theoretical models have been reported to explain fundamental mechanism of the process, but the single-scale simulation studies show obvious limitations for accurate prediction of photo-chemical reactions in photoresist (PR) matrix and the resulting morphology of line pattern. In order to settle the problem, a multiscale model (density functional theory (DFT)-molecular dynamics (MD)-finite difference method (FDM) integration) was developed to simulate chemical reactions including PAG dissociation, acid diffusion, and deprotection of photoresist in our previous study, which is based on two-components system (PAG and PR). Herein, we propose the multiscale model for three molecular components consisting of PAG, PR, and photo-decomposable quencher (PDQ) which is widely used for fine PR pattern fabrication by neutralizing acid in unexposed region of the resist. The newly constructed model reflects more realistic acid diffusion and chemical reactions on PEB process. This achievement will be helpful to identify critical design parameters and suggest optimized design materials in EUV lithography process.

Photoresist (PR) nanopatterning using extreme-ultraviolet-lithography (EUVL) drives significant advances in integrated-circuit downsizing; however, sub-10 nm nodes severely suffer from collapse in the rinsing process (structural rigidity ↓, capillary force ↑ in denser line patterns). To mitigate collapse, we propose a new type of photoresist, hybrid material, with delicate polymer microstructure across the exposure boundary; a blend of linear chains for exposed domain and crosslinked network for masked area. This hybrid system is synthesized in a computational model through exposure-bake-curing process that generates a steep chemical gradient at the exposure boundary of polymer and triggers selective crosslinking reaction on the protected functional groups. The crosslinked structure is formed exclusively for the protection group-rich unexposed region; thus, the chemical joints tightly anchor the masked chains in aqueous solution, leading to nanoscale smoothing on the interfacial surface. Moreover, chemical linkage on the residual chains contributes to force delivery on the polymer matrix under macroscopic strain. Among the candidate materials, the hybrid resist incorporating a bicyclic crosslinker exhibits the best load transfer efficiency (E 101.4% ↑) and uniform interfacial surface (roughness 26.4% ↓), which significantly alleviates mechanical deformation and extends the critical aspect ratio of the pattern over the neat system.

Semiconductor manufacturing industry has reduced the size of wafer for enhanced productivity and performance, and Extreme Ultraviolet (EUV) light source is considered as a promising solution for downsizing. A series of EUV lithography procedures contain complex photo-chemical reaction on photoresist, and it causes technical difficulties on constructing theoretical framework which facilitates rigorous investigation of underlying mechanism. Thus, we formulated finite difference method (FDM) model of post exposure bake (PEB) process on positive chemically amplified resist (CAR), and it involved acid diffusion coupled-deprotection reaction. The model is based on Fick’s second law and first-order chemical reaction rate law for diffusion and deprotection, respectively. Two kinetic parameters, diffusion coefficient of acid and rate constant of deprotection, which were obtained by experiment and atomic scale simulation were applied to the model. As a result, we obtained time evolutional protecting ratio of each functional group in resist monomer which can be used to predict resulting polymer morphology after overall chemical reactions. This achievement will be the cornerstone of multiscale modeling which provides fundamental understanding on important factors for EUV performance and rational design of the next-generation photoresist.

Diarylethene is one of the photo-responsive materials that show rapid and reversible changes in their color/electrochemical properties and macroscopic deformations in the crystalline phase by light irradiation. Photoisomerization is the main cause of the photo reactivity of diarylethene, and we established a statistical model based on the density matrix formalism, which predicts quantitative isomerization progress as a population term. The model reflects photo-switching properties of the target molecule, which were characterized by first principle calculations, and external stimulus factors (light irradiation conditions and temperature). By merging light penetration physics with the model, we derived light penetration depth dependent isomerization progress to theoretically investigate photodeformation of single crystal. The model well reproduced in-plane shear deformation under ultraviolet light irradiation which would provide guideline for photoactuator design. In addition, the statistical model addressed crucial findings (primary stimuli and molecular design parameter for increasing the isomerization rate, external stimuli enhancing fluorescence performance) itself.

For decades, downsizing has been a key issue for high performance and low cost of semiconductor, and extreme ultraviolet lithography is one of the promising candidates to achieve the goal. As a predominant process in extreme ultraviolet lithography on determining resolution and sensitivity, post exposure bake has been mainly studied by experimental groups, but development of its photoresist is at the breaking point because of the lack of unveiled mechanism during the process. Herein, we provide theoretical approach to investigate underlying mechanism on the post exposure bake process in chemically amplified resist, and it covers three important reactions during the process: acid generation by photo-acid generator dissociation, acid diffusion, and deprotection. Density functional theory calculation (quantum mechanical simulation) was conducted to quantitatively predict activation energy and probability of the chemical reactions, and they were applied to molecular dynamics simulation for constructing reliable computational model. Then, overall chemical reactions were simulated in the molecular dynamics unit cell, and final configuration of the photoresist was used to predict the line edge roughness. The presented multiscale model unifies the phenomena of both quantum and atomic scales during the post exposure bake process, and it will be helpful to understand critical factors affecting the performance of the resulting photoresist and design the next-generation material.