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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...

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.

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.