Chemically Amplified Resist Composition for EUV Lithography
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Solution Overview
Problem
Current chemically amplified resist compositions face challenges in controlling acid diffusion, leading to issues such as line edge roughness (LER) and critical dimension uniformity (CDU) during the formation of patterns with high resolution and small feature sizes, particularly in EUV and EB lithography processes.
Innovation Solution
Incorporating a sulfonium salt or iodonium salt with specific structures into the resist composition to generate acids with controlled diffusion, combined with a base polymer that increases solubility in alkaline developers, and optionally using a quencher to further regulate acid diffusion and improve pattern fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acid-decomposable protective groups requiring low activation energy (e.g., acetal groups) are used to increase resist sensitivity, then sensitivity is improved, but acid diffusion occurs in unexposed regions leading to increased LER and degraded CDU
Solution Approach 1:
A base polymer with basic functional groups (e.g., carboxylic acid groups) is introduced as an intermediary substance between the acid generator and the protective group. This base polymer locally neutralizes diffused acid through acid-base reactions, preventing unwanted deprotection in unexposed regions while allowing the desired deprotection in exposed regions, thus resolving the contradiction between sensitivity and pattern precision
Solution Approach 2:
The chemical environment parameters are changed by introducing a base polymer that modifies the local pH conditions. The base polymer creates a chemical gradient where exposed regions maintain acidity for deprotection while unexposed regions become basic to suppress deprotection, thereby controlling acid diffusion effects and improving LER and CDU
2Measurement precision
If conventional acid generators are used to achieve high sensitivity, then sensitivity is improved, but acid diffusion cannot be fully controlled leading to pattern profile degradation
Solution Approach 1:
The base polymer acts as a chemical intermediary that modulates acid diffusion by providing local neutralization. It creates a controlled chemical environment that limits acid migration distance, thereby maintaining sharp pattern edges and rectangular profiles while preserving the high sensitivity enabled by conventional acid generators
Solution Approach 2:
The harmful effect of acid diffusion is extracted and neutralized by the base polymer, which selectively removes excess acid from unexposed regions through acid-base reactions. This separation of functions allows the acid generator to focus on sensitivity while the base polymer handles diffusion control
3Measurement precision
If resist compositions are optimized for high resolution, then resolution is improved, but pattern rectangularity and fidelity deteriorate on substrates with chromium compound surfaces
Solution Approach 1:
The base polymer serves as a protective intermediary layer between the resist pattern and the chromium compound substrate. It prevents direct interaction between the resist and the chromium surface that would otherwise cause profile degradation, thereby maintaining both high resolution and good pattern rectangularity on challenging substrates
Solution Approach 2:
The base polymer provides preliminary protection against the harmful effects of the chromium substrate surface before the pattern formation process completes. By pre-establishing a protective chemical environment, it prevents profile degradation and maintains pattern fidelity throughout the development process
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 solution effectively reduces LER and enhances the rectangularity and fidelity of patterns, ensuring high resolution and consistent pattern formation even on substrates with challenging surface materials like chromium compounds.
Implementation Method 1
Upon exposure to high-energy radiation, the acid-decomposable protective group is deprotected by the catalysis of an acid generated from a photoacid generator
Implementation Method 2
the acid-decomposable protective group is deprotected by the catalysis of an acid generated from a photoacid generator so that the polymer may turn soluble in alkaline developer
Implementation Method 3
a base polymer containing a polymer which is decomposed under the action of acid to increase its solubility in alkaline developer
Implementation Method 4
a quencher which suppresses an action of the acid
Data Source
AI summary
A chemically amplified positive resist composition is provided comprising (A) an acid generator containing a specific sulfonium salt and/or a specific iodonium salt and (B) a base polymer containing a specific polymer which is decomposed under the action of acid to increase its solubility in alkaline developer. The resist composition exhibits a high resolution during pattern formation and forms a pattern with improved LER, rectangularity and fidelity.