ArF Resist Composition for Immersion Lithography Leaching Control
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Solution Overview
Problem
Current ArF immersion lithography resist compositions face challenges with pattern profile degradation, depth of focus (DOF), and line width roughness (LWR) due to leaching of photoacid generators and sulfonium salts, which affect resolution and contamination of exposure tools.
Innovation Solution
A positive resist composition comprising a resin with acid labile groups, a mixture of sulfonium salts, and a solvent, which enhances alkali solubility and improves DOF and LWR by forming a protective film that prevents leaching and maintains pattern rectangularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective film is formed to prevent leaching, then leaching is restrained, but pattern profile is degraded (top-loss occurs)
Solution Approach 1:
The patent removes the protective film from the resist film surface, extracting the element that was causing top-loss while maintaining leaching prevention through alternative means (resist composition modification). This resolves the contradiction by eliminating the harmful effect of the protective film on pattern profile while preserving its protective function through chemical modification of the resist material itself.
Solution Approach 2:
The patent changes the chemical parameters of the resist composition by incorporating specific compounds (sulfonium salt, phosphonium salt, or quaternary ammonium salt) that modify the leaching behavior and pattern formation characteristics. This allows achieving both leaching prevention and good pattern profile without relying on a protective film that causes top-loss.
2Ease of manufacture
If sulfonium salt of nonafluoro-n-butanesulfonate is used in resist composition, then sensitivity and dry etching resistance are adjusted, but DOF performance and retention performance are insufficient
Solution Approach 1:
The patent creates a composite resist composition by combining the base resin with specific compounds (sulfonium salt, phosphonium salt, or quaternary ammonium salt) in defined ratios. This composite material achieves both the desired sensitivity and dry etching resistance while simultaneously improving DOF performance and retention performance, resolving the insufficiency of the single-component system.
Solution Approach 2:
The patent optimizes the concentration parameters of the sulfonium salt, phosphonium salt, or quaternary ammonium salt in the resist composition. By adjusting these parameters within specific ranges, the composition achieves balanced performance in sensitivity, dry etching resistance, DOF performance, and retention performance simultaneously.
3Reliability
If the ratio of acid-dissociable group of adamantyl structure is increased, then retention performance is secured, but removal performance and LWR are degraded
Solution Approach 1:
The patent introduces compounds with specific local chemical structures (sulfonium salt, phosphonium salt, or quaternary ammonium salt) that have different acid-dissociable group characteristics. These local modifications create regions with enhanced retention performance while maintaining overall removal performance and LWR through the balanced composition design.
4Manufacturing precision
If the ratio of acid-dissociable group of cyclopentyl or cyclohexyl structure is increased, then removal performance is secured, but retention performance and pattern profile are degraded
Solution Approach 1:
The patent incorporates compounds with specific local chemical structures (sulfonium salt, phosphonium salt, or quaternary ammonium salt) that provide localized retention enhancement. This allows maintaining good removal performance through the base resin composition while adding localized retention capability where needed, avoiding the pattern profile degradation associated with high ratios of cyclopentyl or cyclohexyl structures.
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 resist composition achieves high resolution and improved DOF and LWR, minimizing pattern profile degradation and contamination, enabling precise micropatterning with enhanced performance for both grouped and isolated patterns.
Implementation Method 1
a photoacid generator in the resist composition, an acid generated therefrom upon exposure
Implementation Method 2
Since water has a refractive index of 1.44 at 193 nm, pattern formation is possible even using a lens with NA of 1.0 or greater
Implementation Method 3
forming a protective film for restraining leaching
Implementation Method 4
a resin comprising acid labile group-containing recurring units so that the resin may increase its alkali solubility under the action of acid
Data Source
AI summary
A positive resist composition is provided comprising (A) a resin comprising recurring units having adamantane ring and recurring units having cyclopentyl so that the resin may increase its alkali solubility under the action of acid, (B) a mixture of sulfonium salts, and (C) a solvent. By coating the resist composition as a resist film, forming a protective film thereon, and effecting immersion lithography, a pattern of good profile is formed at a high resolution.