Fluorine-Containing Polymer Top Coat for Lithography Water Repellency
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Solution Overview
Problem
Current photolithography processes face challenges in achieving high resolution and water repellency for resist films, particularly in liquid immersion lithography, due to issues like pattern shape changes and film swelling, which affect the formation of rectangular cross-section resist patterns.
Innovation Solution
A fluorine-containing polymer with specific repeating units is introduced to enhance water repellency, allowing for the formation of a top coat film that improves surface water repellency and maintains adequate developer solubility, enabling the creation of clear rectangular cross-section resist patterns in liquid immersion lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine-containing polymers are used to improve water repellency of resist film, then water repellency and receding contact angle are improved, but developer solubility may deteriorate
Solution Approach 1:
The patent applies local quality by introducing fluorine atoms specifically at the α-position of the ester group in the polymer repeating unit, rather than uniformly throughout the entire polymer structure. This localized fluorine substitution provides water repellency at the critical interface region while preserving the bulk polymer's developer solubility. The fluorine-containing group is positioned strategically to interact with water molecules at the film surface, while the rest of the polymer backbone maintains compatibility with the developer solution.
Solution Approach 2:
The patent employs composite materials by combining fluorine-containing monomer units with non-fluorinated polymer backbone structures. The resulting copolymer integrates hydrophobic fluorine-containing segments (providing water repellency) with hydrophilic or neutral polymer chains (maintaining developer solubility). This composite structure allows simultaneous achievement of both water repellency and developer solubility by balancing the properties of different molecular segments within the same polymer chain.
2Manufacturing precision
If liquid immersion lithography is used to achieve finer patterning, then resolution is improved, but pattern shape changes and film swelling occur due to dissolution of acid and amine compounds into water
Solution Approach 1:
The patent applies preliminary anti-action by pre-modifying the resist polymer structure with fluorine atoms at the α-position of ester groups before the lithography process. This structural modification creates inherent resistance to water penetration and dissolution, preventing the harmful dissolution of acid and amine compounds into the immersion water. The fluorine substitution proactively counteracts the dissolution tendency, maintaining pattern shape stability throughout the exposure and development processes.
Solution Approach 2:
The patent utilizes parameter changes by modifying the chemical composition parameter of the polymer repeating unit - specifically introducing fluorine atoms at the α-position of the ester group. This compositional parameter change fundamentally alters the polymer's interaction with water, reducing its hydrophilicity and preventing dissolution. The fluorine substitution changes the chemical properties of the resist material to be compatible with liquid immersion lithography while maintaining pattern fidelity.
3Adaptability or versatility
If conventional resins (novolac, polyvinylphenol) are used in resist compositions, then process compatibility is maintained, but light absorption is too high for 193 nm and shorter wavelengths
Solution Approach 1:
The patent applies parameter changes by fundamentally altering the chemical composition of the resist polymer - transitioning from conventional carbon-hydrogen-oxygen based resins (novolac, polyvinylphenol) to fluorine-containing polymer structures. The introduction of fluorine atoms at the α-position of ester groups changes the optical parameters of the material, specifically reducing light absorption at 193 nm and shorter wavelengths. This compositional parameter change enables high light transmission while maintaining polymer processability and resist functionality.
Solution Approach 2:
The patent employs composite materials by creating fluorine-containing copolymers that integrate low-absorption fluorinated segments with polymer backbone structures providing good processability. The composite structure combines the optical advantages of fluorine-containing compounds (high transmission at deep UV wavelengths) with the processing advantages of conventional polymer systems, achieving both high light transmission and process compatibility.
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 fluorine-containing polymer significantly improves water repellency and receding contact angle, ensuring clear rectangular cross-section resist patterns and stable top coat film formation, enhancing stepper throughput without dissolving resist film components.
Implementation Method 1
the fluorine-containing polymer significantly improves water repellency and receding contact angle
Data Source
AI summary
A fluorine-containing polymer of the present invention contains a repeating unit (a) of the general formula (2) and has a mass-average molecular weight of 1,000 to 1,000,000. This polymer is suitably used in a resist composition for pattern formation by high energy ray radiation of 300 nm or less wavelength or electron beam radiation or a top coat composition for liquid immersion lithography and is characterized as having high water repellency, notably high receding contact angle.In the formula, R1 represents a polymerizable double bond-containing group; R2 represents a fluorine atom or a fluorine-containing alkyl group; R8 represents a substituted or unsubstituted alkyl group or the like; and W1 represents a single bond, a substituted or unsubstituted methylene group or the like.