ArF Resist Composition for Liquid Immersion Lithography

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Solution Overview

Problem

Current resist compositions for ArF lithography face challenges such as high Line Edge Roughness, residue after development, and reduced etching resistance, especially when used in liquid immersion lithography, due to swelling during development and degradation of pattern profiles.

Innovation Solution

A resist composition comprising a polymer with specific repeating units, including a sulfonium salt with a polymerizable unsaturated bond and a lactone adhesion group, which reduces swelling and enhances etching resistance, and is insoluble in water to prevent pattern deformation during liquid immersion exposure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional polymers (polyhydroxystyrene or polymers with highly hydrophobic alicyclic groups) are used for ArF lithography, then transparency and etching resistance are improved, but swelling during development occurs leading to high Line Edge Roughness and pattern deformation

Engineering Contradiction:

Improvetransparency and etching resistanceVSAvoidLine Edge Roughness and pattern deformation

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent uses a copolymer combining naphthalene ring units (for transparency and etching resistance) with phenolic hydroxyl groups (for controlled alkali solubility). This composite structure at the molecular level allows the material to simultaneously achieve low swelling during development while maintaining high transparency and etching resistance, resolving the contradiction between reliability and manufacturing precision

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies the chemical parameters of the polymer by introducing specific functional groups (naphthalene rings with phenolic hydroxyls) that have balanced properties: the naphthalene ring provides transparency at 193nm and etching resistance, while the phenolic hydroxyl group provides moderate alkali solubility to prevent excessive swelling. This parameter optimization resolves the contradiction between transparency/etching resistance and pattern fidelity

Inventive Principle:

Principle #35Parameter changes

2Strength

If polymers with highly hydrophobic alicyclic groups are used to enhance etching resistance, then etching resistance is improved, but swelling at the time of development increases due to strong acidity

Engineering Contradiction:

Improveetching resistanceVSAvoidswelling during development

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by positioning specific functional groups at specific locations in the polymer structure: naphthalene rings provide local etching resistance and transparency, while phenolic hydroxyl groups provide localized moderate alkali solubility. This spatial distribution of different functional properties within the polymer chain allows simultaneous achievement of high etching resistance and controlled swelling behavior

Inventive Principle:

Principle #3Local quality

3Measurement precision

If conventional resist compositions are used for liquid immersion lithography, then high NA and resolution are achieved, but residue after development increases and pattern profiles degrade

Engineering Contradiction:

ImproveresolutionVSAvoidresidue after development and pattern profile integrity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent employs a water-soluble polymer design that is specifically optimized for liquid immersion processing. The polymer is formulated to be completely removable by water-based developers without leaving residue, even though it provides the necessary functionality during exposure and development. This disposable approach ensures clean pattern profiles after development while maintaining high resolution during the lithography process

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 resist composition achieves high sensitivity, reduced Line Edge Roughness, and excellent etching resistance, enabling precise ultra-fine processing and maintaining pattern integrity during liquid immersion lithography.

Implementation Method 1

a polymer including repeating units represented by general formulae (a) and (b)... a sulfonium salt with a polymerizable unsaturated bond

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

acid-catalyzed chemically amplified positive resist composition... upon exposure to a high energy beam

Methodology Applied

Scientific EffectChemical amplification:

Data Source

PatentUS7629106B2Resist composition and patterning process using the same

Publication Date: 2009.12.08 SHIN ETSU CHEMICAL CO LTD

AI summary

There is disclosed a resist composition which shows high sensitivity and high resolution on exposure to high energy beam, provides reduced Line Edge Roughness because swelling at the time of development is reduced, provides minor amounts of residue after development, has excellent dry etching resistance, and can also be used suitably for the liquid immersion lithography; and a patterning process using the resist composition. There can be provided a resist composition which comprises, at least, a polymer including repeating units represented by the following general formulae (a) and (b).