Onium Salt Acid Diffusion Controller for Lithography
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Solution Overview
Problem
As LSIs continue to miniaturize, acid diffusion in resist materials becomes a significant issue for achieving high sensitivity and resolution, particularly in deep ultraviolet and EUV lithography, leading to challenges in maintaining pattern integrity and uniformity, with existing solutions either compromising sensitivity or causing pattern collapse during alkaline development.
Innovation Solution
A novel onium salt with a specific structure, represented by general formula (1), is introduced as an acid diffusion controller, which improves sensitivity, resolution, and critical dimension uniformity while preventing pattern collapse by effectively controlling acid diffusion and enhancing solvent solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid diffusion is suppressed by reducing temperature and/or time of post-exposure bake, then resolution is improved, but sensitivity and contrast are significantly reduced
Solution Approach 1:
The patent introduces a quencher compound as an intermediary substance that mediates between the acid generator and the resist film. This quencher selectively quenches acid diffusion while allowing the acid generator to maintain its sensitivity-enhancing function, thus resolving the contradiction between resolution improvement and sensitivity maintenance
Solution Approach 2:
The patent applies local quality by creating different functional zones within the resist film: regions with high acid concentration for sensitivity enhancement and regions with quenched acid diffusion for resolution improvement. The quencher compound creates localized acid sinks that prevent bulk diffusion while preserving local reactivity
2Manufacturing precision
If a sulfonium salt or iodonium salt generating sulfonic acid without fluorine is used as quencher, then acid diffusion is controlled, but the quencher undergoes ion exchange with fluorine-substituted sulfonic acid, reducing effectiveness
Solution Approach 1:
The patent changes the chemical parameter of the quencher by selecting sulfonium salts or iodonium salts that generate carboxylic acid instead of sulfonic acid. This parameter change prevents ion exchange reactions with fluorine-substituted sulfonic acid, ensuring stable and effective acid diffusion control throughout the resist film
Solution Approach 2:
The patent converts the potential harm of ion exchange reactions into a benefit by deliberately choosing quencher compounds that are resistant to ion exchange. The carboxylic acid-generating quenchers remain stable in the resist film environment, turning what would be a reactive instability into a stable, long-lasting quenching effect
3Manufacturing precision
If sulfonium salts with multiple hydroxy groups in aromatic ring are used, then acid diffusion is controlled, but solvent solubility decreases and precipitation occurs
Solution Approach 1:
The patent changes the chemical structure parameter of the quencher by selecting compounds with fewer hydroxy groups and appropriate aromatic ring substitutions. This parameter change maintains acid diffusion control capability while significantly improving solvent solubility and preventing precipitation during resist film formation and development
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 novel onium salt effectively reduces line width roughness and critical dimension uniformity, preventing pattern collapse during alkaline development, and maintains high sensitivity and resolution in lithography processes, making it suitable for both positive and negative resist types.
Implementation Method 1
the sulfonium salt or iodonium salt that generates the sulfonic acid not having fluorine substituted at a position undergoes ion exchange with the sulfonic acid having fluorine substituted at a position
Implementation Method 2
a deprotection reaction progresses by the use of a photo-acid generator that generates a sulfonic acid having a fluorine atom substituted at a position
Data Source
AI summary
The present invention is an onium salt represented by the following general formula (1), where n1 represents an integer of 0 or 1; n2 represents an integer of 0 to 3; R1a represents a hydrocarbyl group having 1 to 20 carbon atoms and optionally containing a heteroatom; n3 represents an integer of 0 to 3; R1b represents a hydrocarbyl group having 1 to 36 carbon atoms and optionally containing a heteroatom; XA represents a carbonyl group that forms an amide bond together with an adjacent —NH or represents a sulfonyl group that forms a sulfonamide bond together with the adjacent —NH; n4 represents an integer of 1 or 2; and Z+ represents an onium cation. This provides: a resist composition in lithography that has high sensitivity and excellent resolution, can improve LWR and CDU, and can also suppress collapse of a resist pattern; and a novel onium salt to be used in the resist composition.