Polymer-Bound Photo-Acid Generator for Low-LWR EUV Resists
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Solution Overview
Problem
Existing resist compositions face challenges in achieving high sensitivity, resolution, and low line width roughness (LWR) while maintaining etching resistance and pattern stability during fine pattern formation in photolithography, particularly in EUV lithography.
Innovation Solution
Development of an onium-salt-type monomer and monomeric photo-acid generator with a specific structure that includes an aromatic ring substituted with a polymerizable group and iodine atom, bonded with a fluorosulfonate anion and acid-labile group, forming a polymer-bound photo-acid generator for a chemically-amplified resist composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amount of acid generator is increased to enhance sensitivity, then sensitivity is improved, but acid diffusion distance is increased leading to degraded LWR and CDU
Solution Approach 1:
The patent combines the acid generator function with the polymer backbone by incorporating onium salt groups directly into the polymer structure. This creates a polymer-bound acid generator where the acid-generating moieties are covalently attached to the polymer chain, preventing premature diffusion while maintaining high sensitivity through increased acid generator density.
Solution Approach 2:
The acid generator is pre-bound to the polymer structure before exposure, positioning it exactly where acid is needed. This preliminary positioning ensures that upon exposure, acid is generated in-situ with minimal diffusion distance, thereby achieving high sensitivity without compromising LWR and CDU.
2Volume of moving object
If the resist film is made thinner to comply with miniaturization progress, then miniaturization capability is improved, but LWR becomes greater
Solution Approach 1:
The patent changes the chemical composition parameters of the resist by incorporating fluorinated onium salt groups with specific molecular structures (formula 1) that provide optimal balance between film thickness reduction and LWR control. The fluorine substitution and specific onium salt structure modify the acid diffusion characteristics and polymer properties to maintain low LWR in thinner films.
3Productivity
If iodine atoms are introduced to improve EUV absorption, then lithography performance is improved, but organic solvent solubility decreases causing precipitation
Solution Approach 1:
The patent applies local quality by strategically placing fluorine atoms at specific positions in the onium salt structure (R1-R6 groups in formula 1) while maintaining iodine atoms for EUV absorption. The fluorine substitution at specific locations improves solubility without compromising the iodine's EUV absorption capability, creating a locally optimized structure that balances both requirements.
Solution Approach 2:
The patent creates a composite molecular structure combining iodine atoms (for EUV absorption) with fluorinated onium salt groups (for solubility enhancement). This composite structure integrates two different functional elements - the iodine component for photolithography performance and the fluorinated component for solubility - into a single molecule that achieves both objectives simultaneously.
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 exhibits high solvent solubility, sensitivity, and contrast, improving lithography performance with reduced acid diffusion, enhancing line width roughness and critical dimension uniformity, and providing excellent etching resistance.
Implementation Method 1
Iodine atoms very greatly absorb EUV having a wavelength of 13.5 nm, and an effect that secondary electrons are generated from iodine atoms during exposure is observed.
Implementation Method 2
The so-called polymer-bound acid generator is capable of generating a polymer-type sulfonic acid upon exposure and characterized by a very short distance of acid diffusion.
Implementation Method 3
The acid-labile group contained in the anion has a structure where an aromatic hydroxy group is protected, and a deprotection reaction progresses along with the generation of the acid.
Data Source
AI summary
An onium-salt-type monomer is represented by the formula (a), where “n1” is 0 or 1, “n2” is 1 to 4, “n3” is 0 to 2, “n4” is 0 to 4; RA is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group; RAL is an acid-labile group; R1 is a halogen atom, a nitro group, a cyano group; LA and LB are each a single bond, an ester bond; XL is a single bond or a hydrocarbylene group; Q1 and Q2 are each a hydrogen atom, a fluorine atom, or a fluorinated saturated hydrocarbyl group; Q3 and Q4 are each a fluorine atom or a fluorinated saturated hydrocarbyl group; and Z+ is an onium cation.