Sulfonium Salt Polymer Resist for Low-LER Patterning
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Solution Overview
Problem
Existing chemically amplified resist compositions face issues with acid diffusion leading to line edge roughness (LER) and critical dimension uniformity (CDU) degradation, poor etch resistance, and pattern collapse during miniaturization in semiconductor manufacturing, particularly in ArF excimer laser lithography and electron beam (EB) lithography.
Innovation Solution
A sulfonium salt monomer generating an acid with controlled diffusion and strength, incorporated into a polymer with aromatic sulfonic acid anions, forming a chemically amplified resist composition that enhances etch resistance and solvent solubility, reducing LER and improving pattern resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acid diffusion is not controlled, then deprotection reaction can occur in unexposed regions, but line edge roughness (LER) and critical dimension uniformity (CDU) are degraded
Solution Approach 1:
The patent introduces a specific sulfonium salt compound as an intermediary substance that mediates between the acid generation and deprotection processes. This compound has a molecular structure designed to control acid diffusion while maintaining effective deprotection in exposed regions, preventing unwanted reactions in unexposed areas and thereby improving both reliability and manufacturing precision
Solution Approach 2:
The patent modifies the chemical parameters of the acid generator by using a specific sulfonium salt compound with controlled molecular structure. This changes the diffusion characteristics and reactivity parameters of the generated acid, allowing precise control over the deprotection reaction to achieve sharp pattern edges and uniform critical dimensions
2Strength
If polymer with aromatic structure is used for KrF lithography, then high etching resistance is achieved, but strong absorption at 200 nm prevents use in ArF lithography
Solution Approach 1:
The patent applies local quality by incorporating aromatic structures with specific local chemical modifications (sulfonium salt groups) that provide etching resistance at needed locations while maintaining overall transparency at the ArF wavelength. The aromatic rings provide structural stability and etch resistance, while the sulfonium groups control the optical and chemical properties locally
3Productivity
If low activation energy protective groups are used, then high sensitivity resist film is obtained, but deprotection reaction occurs in unexposed regions causing LER and CDU degradation
Solution Approach 1:
The sulfonium salt compound acts as an intermediary that bridges the gap between high sensitivity and precision. It enables the use of low activation energy protective groups while controlling the acid diffusion to prevent premature deprotection, thus maintaining both high sensitivity and manufacturing precision
Solution Approach 2:
The patent changes the reactivity parameters by selecting protective groups with low activation energy while simultaneously controlling the acid generation and diffusion parameters through the sulfonium salt structure. This parameter optimization allows high sensitivity without sacrificing pattern fidelity
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 composition achieves high contrast, reduced LER, improved etch resistance, and solvent solubility, enabling the formation of small-size patterns with enhanced resolution and stability during development and etching steps.
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
Implementation Method 3
Since acid diffusion has a significant impact on the sensitivity and resolution of a chemically amplified resist composition, many studies are made on the acid diffusion problem
Data Source
AI summary
A sulfonium salt monomer containing an aromatic sulfonic acid anion having a vinyl-substituted aromatic ring generates an acid having an adequate acid strength and reduced diffusion distance. A chemically amplified positive resist composition comprising a polymer comprising repeat units derived from the monomer exhibits etch resistance and organic solvent solubility.