Onium Salt Resist Composition for Fine Pattern Lithography
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Solution Overview
Problem
Conventional resist compositions using onium salt-type photoacid generators fail to fully suppress acid diffusion, leading to deteriorated lithography performance such as contrast, line-width roughness (LWR), critical dimension uniformity (CDU), mask error factor (MEF), exposure latitude (EL), and depth of focus (DOF).
Innovation Solution
An onium salt composed of an aromatic sulfonate anion substituted with a hydrocarbyl group containing at least one aromatic ring and a sulfonium cation with a nitro group, which is used as a photoacid generator in a chemically amplified resist composition, effectively suppressing acid diffusion and enhancing lithography performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional onium salt-type photoacid generators are used, then the resist composition can be formulated with basic components, but acid diffusion cannot be fully suppressed leading to deteriorated lithography performance
Solution Approach 1:
The patent modifies the molecular structure parameters of the onium salt by introducing specific substituents: a hydrocarbyl group with 6-60 carbon atoms containing at least one aromatic ring on the anion side, and a nitro group on the cation side. These structural parameter changes increase the molecular size and enhance the suppressive effect on acid diffusion, thereby improving lithography performance metrics including LWR, CDU, and MEF.
Solution Approach 2:
The patent creates a composite photoacid generator structure combining specific anion and cation components with complementary functions. The anion with aromatic ring-containing hydrocarbyl group provides structural bulk and diffusion suppression, while the cation with nitro group enhances photoacid generation efficiency. This composite approach achieves synergistic effects that conventional single-structure onium salts cannot attain.
2Object-generated harmful factors
If the molecular size of photoacid generator is increased to suppress acid diffusion, then acid diffusion is reduced, but the complexity of molecular design and material selection becomes more difficult
Solution Approach 1:
The patent divides the photoacid generator into distinct functional segments: the anion portion with hydrocarbyl group for diffusion suppression, and the cation portion with nitro group for photoacid generation. This segmentation allows independent optimization of each component's structure and function, simplifying the overall design process while achieving superior performance.
Solution Approach 2:
The patent applies local quality by concentrating specific functional groups at particular locations within the molecule. The aromatic ring-containing hydrocarbyl group is positioned on the anion side to provide localized diffusion suppression, while the nitro group is placed on the cation side for localized photoacid generation enhancement. This localized functional distribution optimizes performance without requiring complex throughout-the-molecule modifications.
3Power
If starting materials containing fluorine atoms are used, then photoacid generation efficiency is improved, but the cost increases due to expensive starting materials
Solution Approach 1:
The patent employs a photoacid generator design where the fluorine-containing components are used in controlled amounts during the lithography process and subsequently degraded or removed. The focus is on using fluorine strategically in the photoacid generation active sites rather than throughout the entire molecule, reducing material costs while maintaining high photoacid generation efficiency during the critical exposure window.
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 onium salt-based resist composition exhibits high sensitivity, excellent acid diffusion suppression, and superior lithography performance, improving LWR, CDU, MEF, EL, and DOF, facilitating fine patterning.
Implementation Method 1
a photoacid generator composed of an onium salt... effectively suppressing acid diffusion and enhancing lithography performance
Data Source
AI summary
The present invention is an onium salt composed of: an anion represented by general formula (1A); and a cation represented by general formula (1B). This can provide an onium salt used as a photoacid generator contained in a chemically amplified resist composition with excellent solvent solubility, high sensitivity, high contrast, and excellent lithography performance in photolithography using high-energy radiation; a photoacid generator composed of the onium salt; a chemically amplified resist composition containing the photoacid generator; and a patterning process using the chemically amplified resist composition.