Fluorine-Containing Resist Composition for EUV Lithography

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Solution Overview

Problem

EUV lithography faces challenges with defects in mask blanks and low light intensity due to high strength pellicles, leading to increased defect occurrence and risk of pattern collapse and residue formation in microelectronic device manufacturing, particularly at the 5-nm node scale.

Innovation Solution

A resist composition incorporating an ammonium salt and fluorine-containing polymer with specific repeat units is developed, which segregates on the resist film surface to enhance light absorption, control acid diffusion, and improve solubility in alkaline developers, preventing nano-bridging, pattern collapse, and residue formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high strength pellicle is used to protect mask, then mask protection is improved, but light intensity is reduced and defect risk increases

Engineering Contradiction:

Improvemask protectionVSAvoidlight intensity

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The fluorine-containing polymer acts as an intermediary layer on the resist film surface that enhances EUV light absorption and sensitivity without requiring a high-strength pellicle on the mask. This mediator approach allows the resist itself to compensate for light intensity issues rather than relying on mask protection that would further reduce light transmission

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameters of the resist film by incorporating fluorine-containing polymers with specific repeat units (CF3, CF2, CHF2 groups). This compositional change increases EUV absorption coefficient and sensitivity, allowing effective patterning with available light intensity while eliminating the need for high-strength pellicles

Inventive Principle:

Principle #35Parameter changes

2Productivity

If pattern rule is reduced for higher integration density, then integration density is improved, but defect occurrence probability increases

Engineering Contradiction:

Improveintegration densityVSAvoiddefect occurrence

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The fluorine-containing polymer segregates to the surface of the resist film, creating a localized region with enhanced EUV absorption and modified chemical properties. This local concentration of fluorine groups at the film surface provides improved sensitivity and defect control precisely where light absorption occurs, without affecting the bulk resist properties

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The resist composition is formulated as a composite material combining base polymer with fluorine-containing polymer additive (0.1-10 wt%). This composite structure leverages the complementary properties of both materials: the base polymer provides structural integrity while the fluorine-containing polymer enhances EUV absorption and surface properties, achieving high integration density with reduced defects

Inventive Principle:

Principle #40Composite materials

3Use of energy by moving object

If iodine atoms are introduced for sensitizing effect, then sensitivity is improved, but solubility in alkaline developer is reduced causing residues

Engineering Contradiction:

ImprovesensitivityVSAvoidresidue formation

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The invention uses fluorine-containing groups (CF3, CF2, CHF2) as temporary sensitizing agents that perform their function during exposure and then are completely removed during development. These fluorine-containing segments act as disposable sensitivity enhancers that dissolve cleanly in alkaline developer, leaving no residues, unlike persistent iodine atoms

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention converts the typically harmful effect of fluorine (low solubility in water) into a beneficial temporary state during exposure by using fluorine-containing groups that provide high EUV absorption. After exposure, the fluorine-containing segments are designed to be removable, transforming the solubility issue into a controlled development process that eliminates residues

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Reliability

If fluorine-containing polymer is added to improve water repellency, then water repellency is improved, but acid diffusion control and sensitivity are limitative

Engineering Contradiction:

Improvewater repellencyVSAvoidsensitizing effect

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The invention creates local quality differentiation by having fluorine-containing groups concentrate at the resist film surface through segregation. This surface localization provides enhanced water repellency where needed while the fluorine groups also provide the sensitizing effect at the light absorption interface. The specific molecular structure with CF3, CF2, and CHF2 groups optimizes both surface properties and EUV absorption

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the chemical parameters of the fluorine-containing polymer by specifying particular repeat units with different fluorine compositions (CF3, CF2, CHF2). This parameter optimization balances water repellency (from fluorine content) with EUV absorption (from specific fluorine configurations) and solubility characteristics, overcoming the limitations of conventional fluorinated polymers

Inventive Principle:

Principle #35Parameter changes

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, reduces defects, and improves pattern rectangularity and uniformity, ensuring reliable microelectronic device manufacturing at the 5-nm node scale by preventing nano-bridging and pattern collapse while maintaining high sensitivity.

Implementation Method 1

Iodine atoms have remarkably high absorption of EUV and thus achieve a sensitizing effect... The fluorine-containing polymer additive which segregates on the surface of a resist film to improve water repellency

Methodology Applied

Scientific EffectEUV absorption: Absorption (EM radiation)

Implementation Method 2

This is effective for suppressing acid diffusion on the resist film surface and improving the rectangularity of a resist pattern as developed

Methodology Applied

Scientific EffectAcid diffusion: Diffusion

Implementation Method 3

a base polymer having iodine introduced therein has a low dissolution rate in alkaline developer, which indicates a lowering of sensitivity and causes residues to be left in space regions of resist patterns

Methodology Applied

Scientific EffectSolubility: Solvation

Data Source

PatentUS11835860B2Resist composition and patterning process

Publication Date: 2023.12.05 SHIN ETSU CHEMICAL CO LTD

AI summary

A resist composition comprising an ammonium salt and fluorine-containing polymer comprising repeat units AU having an ammonium salt structure of an iodized or brominated phenol compound and repeat units FU-1 having a trifluoromethylalcohol group and/or repeat units FU-2 having a fluorinated hydrocarbyl group offers a high sensitivity and is unsusceptible to nano-bridging, pattern collapse or residue formation, independent of whether it is of positive or negative tone.