Sulfonium Salt Monomer for Resist Pattern Collapse Prevention
Solution Overview
Problem
Conventional sulfonium salt-type photoacid generators in resist compositions face issues with insufficient dissolution contrast, leading to deteriorated lithographic performance, pattern collapse, and acid diffusion, which affects the miniaturization of resist patterns and mask fidelity in photolithography.
Innovation Solution
A sulfonium-salt-type polymerizable monomer with a specific structure, including a fluorine-containing acid-labile group and a non-nucleophilic counterion, is used to create a polymer photoacid generator and base resin, enhancing solvent solubility, sensitivity, and contrast, while inhibiting acid diffusion and pattern collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sulfonium salt-type photoacid generators are used in resist compositions, then the resist can be manufactured with standard materials, but the dissolution contrast is insufficient leading to deteriorated lithographic performance
Solution Approach 1:
The patent modifies the molecular structure of sulfonium salt-type photoacid generators by introducing specific substituent groups (such as fluorinated groups, adamantyl groups, or bridged bicyclic groups) to change the physical and chemical parameters of the compound. These structural modifications enhance the dissolution contrast and acid generation efficiency, thereby improving lithographic performance while maintaining manufacturing feasibility
Solution Approach 2:
The patent creates composite photoacid generator molecules by combining sulfonium cations with specifically designed anionic substituents. This composite structure integrates multiple functional groups that work synergistically: the sulfonium core provides photoacid generation capability while the attached substituents control solubility, acid diffusion, and dissolution contrast, resulting in superior lithographic performance
2Productivity
If the resist pattern is miniaturized to achieve higher integration, then the circuit density increases, but the acid diffusion becomes more significant affecting mask fidelity
Solution Approach 1:
The patent extracts and addresses the acid diffusion problem by incorporating specific substituent groups into the photoacid generator structure that act as diffusion barriers. These groups (such as bulky adamantyl or bridged bicyclic structures) are strategically positioned to restrict acid movement while allowing photoacid generation, thereby maintaining mask fidelity in miniaturized patterns
Solution Approach 2:
The patent applies local quality modification by introducing specific functional groups at particular positions within the photoacid generator molecule. The sulfonium core maintains photoacid generation function while localized substituent groups (such as fluorinated or bulky groups) provide localized acid diffusion control, enabling precise pattern formation at miniaturized dimensions
3Ease of manufacture
If perfluoroalkanesulfonic acid is used as the generated acid, then the photoacid generator can be synthesized, but the acid has hard degradability and bioconcentration property causing toxicity concern
Solution Approach 1:
The patent modifies the chemical structure of the generated acid by replacing perfluoroalkyl groups with alternative substituents such as fluorinated cyclic groups or groups containing decomposable bonds. This structural parameter change maintains the photoacid generation capability and manufacturing ease while introducing environmental degradability to eliminate bioconcentration and toxicity issues
Solution Approach 2:
The patent designs the photoacid generator to produce acids with limited stability and high degradability. The generated acid performs its function during lithography then rapidly degrades into harmless byproducts, analogous to disposable objects that fulfill their purpose and are discarded. This approach eliminates persistent toxic effects while maintaining manufacturing feasibility
4Ease of manufacture
If the photoacid generator structure is simplified to reduce cost, then the manufacturing cost decreases, but the molecular design flexibility for changing bulkiness is limited
Solution Approach 1:
The patent creates a universal sulfonium salt platform where the core structure remains consistent for easy manufacturing, while modular substituent groups can be interchangeably attached to achieve different molecular properties. This multi-functional design allows the same base structure to serve multiple purposes: cost-effective synthesis, adjustable bulkiness, controlled solubility, and tailored acid diffusion characteristics
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 resulting resist composition exhibits improved lithographic performance with high sensitivity, exposure latitude, and reduced line width roughness, effectively preventing pattern collapse and enhancing mask fidelity in photolithography.
Implementation Method 1
sulfonium-salt-type polymerizable monomer... polymer photoacid generator... having a repeating unit derived from the monomer
Implementation Method 2
photoacid generator... acid to be generated... by exposure
Data Source
AI summary
The present invention is a sulfonium-salt-type polymerizable monomer represented by the following formula (1),wherein “p” represents an integer of 1 to 3; R11 represents a C1-20 hydrocarbyl group; Rf represents a fluorine atom or a fluorine-atom-containing C1-6 group selected from alkyl, alkoxy, and sulfide; “q” represents an integer of 1 to 4; RALU represents an acid-labile group; “r” represents an integer of 1 to 4; R12 represents a C1-20 hydrocarbyl group; “s” represents an integer of 0 to 4; “t” represents an integer of 0 to 2; Rf and —O—RALU are bonded to adjacent carbon atoms; and A-X− represents a non-nucleophilic counterion having a polymerizable group A. This provides: a monomer to yield a polymer; the polymer contained in a resist composition; the composition having excellent solvent-solubility, sensitivity, contrast, and lithographic performance, and hardly causing pattern collapse even with fine patterning; and a patterning process using the composition.