Photoacid Generators for EUV Lithography
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Solution Overview
Problem
Current EUV lithography technologies face challenges with slow photospeed and low resist sensitivity due to inadequate absorption of EUV photons by traditional photoacid generators (PAGs), leading to increased line edge roughness and outgassing issues.
Innovation Solution
Development of novel PAGs with optimized EUV photoabsorption characteristics, where the cation (P+) has high EUV photoabsorption cross-sections and the anion (A−) has low EUV photoabsorption cross-sections, or vice versa, to enhance acid generation efficiency and resist sensitivity, along with the use of a small amount of base quencher to improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional PAGs are used in EUV lithography, then the resist formulation is simple and well-established, but the photospeed is slow and resist sensitivity is low due to inadequate absorption of EUV photons
Solution Approach 1:
The patent applies parameter changes by modifying the atomic composition of PAG molecules, specifically selecting atoms with high EUV photoabsorption cross-sections (such as iodine, selenium, sulfur) to replace traditional atoms in PAG structures. This changes the absorption characteristics of PAGs at EUV wavelengths, enabling significantly improved photospeed and resist sensitivity while maintaining formulation simplicity
Solution Approach 2:
The patent employs composite materials by creating PAGs with optimized atomic combinations - combining cations with high EUV absorption cross-sections (containing I, Se, or S atoms) with appropriate anions. This composite approach at the molecular level achieves superior EUV photon absorption efficiency, resolving the contradiction between photospeed and resist sensitivity
2Productivity
If traditional PAGs with high fluorine content anions are used, then the acid generation is efficient, but line edge roughness increases and outgassing issues occur
Solution Approach 1:
The patent applies local quality by differentiating the functional requirements of PAG components: the cation is designed with high EUV absorption cross-section for photon capture, while the anion is selected with lower fluorine content to reduce outgassing and line edge roughness. This localized optimization of different molecular regions resolves the contradiction between acid generation efficiency and harmful effects
Solution Approach 2:
The patent changes the parameter of anion composition by reducing fluorine content compared to traditional perfluorinated anions. This parameter modification maintains adequate acid generation efficiency while significantly reducing outgassing and line edge roughness, resolving the harmful side effects of conventional high-fluorine PAGs
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The optimized PAGs significantly increase EUV photospeed and reduce line edge roughness and outgassing, achieving better resist performance and image quality compared to conventional PAGs.
Implementation Method 1
the absorption of EUV light is characterized by photoabsorption cross-sections that depend on the atomic composition of the compound
Implementation Method 2
PAGs are non-acidic molecules that absorb photons and subsequently form acid via a photochemical decomposition
Data Source
AI summary
A photoacid generator P+ A− comprises (a) an antenna group P+ comprising atoms with high EUV photoabsorption cross-sections according to FIG. 1 and A− anions; or (b) an antenna group P+ and A− comprising anions with low photoabsorption cross-sections for EUV; or (c) an antenna group P+, comprising atoms with high EUV photoabsorption cross-sections according to FIG. 1 and A− comprising anions with low photoabsorption cross-sections for EUV. Novel compounds comprise DTFPIO PFBuS, and DTBPIO CN5.