EUV Pitch Splitting with Solubility-Tuned Overcoat Layers

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

EUV lithography faces challenges with increasing costs, lower throughput, and the difficulty of identifying suitable polymers for crosslinkable overcoat layers due to chemistry mismatches with EUV resists, rendering 193i pitch-splitting processes unsuitable.

Innovation Solution

Development of overcoat layer compositions for EUV pitch-splitting processes using specific solvents and polymers that do not mix with EUV resist, combined with thermal or photoacid generators to modify mandrel portions, enabling reduced feature sizes through controlled solubility changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If 193i pitch-splitting processes are used, then feature size reduction is achieved, but chemistry mismatches with EUV resists make the process unsuitable for EUV lithography

Engineering Contradiction:

Improvefeature sizeVSAvoidcompatibility with EUV resist

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the chemical parameters of the overcoat layer by selecting specific polymers (polycarbonate, polyacrylate, polymethacrylate) and solvents (isoamyl ether, isobutyl isobutyrate) that are compatible with EUV resist chemistry. This allows the pitch-splitting process to be adapted for EUV lithography while maintaining feature size reduction capability.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If EUV lithography is used, then throughput is improved, but difficulty in identifying suitable polymers for overcoat layers increases

Engineering Contradiction:

ImprovethroughputVSAvoidpolymer selection

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent identifies polymers with multiple functional units that can serve different purposes: hydrophobic units (n-butyl, t-butyl) provide solubility control, while aromatic units (styrene, hydroxystyrene) provide etch resistance. This multi-functionality simplifies the manufacturing process by using a single polymer to achieve multiple objectives.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent uses copolymers containing different constitutional units (e.g., n-butyl methacrylate and styrene) to combine properties of different materials. This composite approach allows tuning of solubility and etch resistance by adjusting the ratio of different units, making the material selection process more systematic and easier.

Inventive Principle:

Principle #40Composite materials

3Strength

If crosslinkable overcoat layers are used, then etch resistance is improved, but chemistry mismatches with EUV resists occur

Engineering Contradiction:

Improveetch resistanceVSAvoidcompatibility with EUV resist

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent achieves etch resistance through local chemical groups (aromatic units like styrene and hydroxystyrene) embedded within the polymer chain, rather than requiring crosslinking chemistry that would conflict with EUV resist. This local modification allows the overcoat to have high etch resistance while remaining compatible with EUV resist processing.

Inventive Principle:

Principle #3Local quality

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

Enables smaller feature fabrication with improved throughput and reduced aspect ratios, facilitating efficient pattern transfer to underlying layers using EUV lithography.

Implementation Method 1

baking the substrate to cause the thermal acid generator to generate a solubility-changing agent

Methodology Applied

Scientific EffectThermal energy conversion: Thermolysis

Implementation Method 2

the solubility-changing agent to diffuse into the mandrel to form a first mandrel portion and a second mandrel portion with different solubility

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS20260029717A1Pitch splitting for EUV imaging

Publication Date: 2026.01.29 TOKYO ELECTRON LTD

AI summary

A method of patterning a substrate includes forming a mandrel over the substrate, the mandrel including an extreme ultraviolet (EUV) resist, and depositing a first overcoat layer over the mandrel from a first solution, the first solution including a first solvent, a first polymer, and an agent generator or an acid. The method further includes selectively removing the first overcoat layer leaving a first mandrel portion surrounded by a second mandrel portion, the second mandrel portion being formed by modifying an outer portion of the mandrel by the first overcoat layer. The method further includes depositing a second overcoat layer over the second mandrel portion from a second solution, the second overcoat layer being separated from the first mandrel portion by the second mandrel portion, the second solution including a second solvent, and a second polymer. And the method further includes forming a second mandrel along a sidewall of the first mandrel portion by selectively removing the second mandrel portion relative to the first mandrel portion.