Thioxanthone Acid Generators for EUV Photoresist
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Solution Overview
Problem
Current photoresist compositions for EUV Lithography face challenges in achieving highly resolved fine features with low linewidth roughness and sufficient sensitivity for wafer throughput.
Innovation Solution
Development of new acid generator compounds comprising a cyclic sulfonium salt covalently linked with an acid-labile moiety, particularly thioxanthone derivatives, which exhibit favorable electrochemical reduction potentials and enhanced photospeeds upon EUV radiation exposure, are integrated into photoresist compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing photoresist compositions are used for EUV lithography, then current manufacturing processes can be maintained, but highly resolved fine features with low linewidth roughness and sufficient sensitivity cannot be achieved
Solution Approach 1:
The patent modifies the chemical structure of acid generator compounds by introducing a cyclic sulfonium salt core with covalently attached acid-labile groups and hydroxyl groups at specific positions. This structural parameter change enables the compound to generate acid more efficiently upon EUV exposure, thereby improving both resolution and sensitivity simultaneously
Solution Approach 2:
The acid generator compound combines multiple functional moieties into a single composite structure: the cyclic sulfonium salt provides the acid-generating capability, while the covalently linked acid-labile groups provide the resolution-enhancing function. This composite approach allows both sensitivity and linewidth roughness performance to be optimized together
2Productivity
If photoresist compositions are optimized for high sensitivity, then wafer throughput is improved, but resolution and linewidth roughness deteriorate
Solution Approach 1:
The patent optimizes the electrochemical reduction potential of the acid generator by adjusting the substitution patterns on the cyclic sulfonium salt core. This parameter change enables the compound to have appropriate sensitivity for high wafer throughput while maintaining the resolution performance needed for fine feature fabrication
Solution Approach 2:
The patent places specific functional groups at defined positions on the cyclic sulfonium salt structure. The hydroxyl groups at positions 4 and 7, along with the acid-labile groups, create local functional zones that independently contribute to sensitivity and resolution, allowing both productivity and precision to be optimized
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
These compounds improve lithographic performance by providing enhanced contrast and resolution, enabling the formation of submicron features with reduced linewidth roughness and increased sensitivity, thus addressing the limitations of existing EUV photoresist materials.
Implementation Method 1
acid generator compounds that comprise a cyclic sulfonium salt with a covalently linked acid-labile moiety... exhibit favorable electrochemical reduction potentials (e.g., ≧−2.0 V vs. Ag/AgCl) and comparatively enhanced photospeeds upon exposure to EUV radiation
Data Source
AI summary
Acid generator compounds are provided that are particularly useful as a photoresist composition component. Acid generator compounds of the invention comprise 1) a cyclic sulfonium salt and 2) a covalently linked photoacid-labile group. In one aspect, thioxanthone acid generator compounds are particularly preferred, including acid generator compounds that comprise (i) a thioxanthone moiety; and (ii) one or more covalently linked acid labile-groups.