Sulfonium Salt Monomer Resist for High-Sensitivity Low-LWR Patterning

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Solution Overview

Problem

Existing chemically amplified resist compositions face challenges in achieving high sensitivity, resolution, and lithography properties such as exposure tolerance, line width roughness (LWR), critical dimension uniformity (CDU), and depth of focus (DOF) due to issues like acid diffusion and solvent solubility of iodine-containing photoacid generators.

Innovation Solution

A sulfonium salt monomer with a nitro group and aromatic sulfonate anion is used to create a polymer with improved lithography properties, enhancing sensitivity and resolution through the use of polymers containing repeat units derived from this monomer in a chemically amplified resist composition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the amount of acid generator is increased to enhance sensitivity, then sensitivity is improved, but the acid diffusion distance is also increased which degrades LWR and CDU

Engineering Contradiction:

ImprovesensitivityVSAvoidLWR

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The acid generator is segmented into two functional parts: a polymeric acid generator component attached to the polymer backbone that provides localized acid generation, and a small molecule acid generator component that enhances sensitivity. This segmentation allows the polymeric part to control acid diffusion distance while the small molecule part boosts sensitivity, resolving the contradiction between sensitivity and LWR.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The resist composition uses a composite acid generator system combining polymeric acid generator units (attached to polymer backbone) and small molecule acid generator units (free in composition). This composite approach leverages the advantages of both types: polymeric units provide short acid diffusion distance for low LWR, while small molecule units provide high sensitivity, simultaneously achieving both improved sensitivity and maintained LWR/CDU.

Inventive Principle:

Principle #40Composite materials

2Volume of moving object

If the film thickness is reduced to comply with size reduction progress, then integration density is improved, but LWR becomes greater which degrades pattern quality

Engineering Contradiction:

Improvefilm thicknessVSAvoidLWR

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The invention changes the chemical parameters of the resist system by introducing specific polymeric acid generator units with controlled acid diffusion characteristics. This parameter change allows thin film formation (reducing film thickness) while maintaining low LWR through the localized acid generation capability of the polymeric units, thus resolving the contradiction between film thickness reduction and LWR control.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If iodine atoms are introduced to improve EUV absorption and lithography properties, then sensitivity is improved, but solvent solubility decreases causing precipitation concerns

Engineering Contradiction:

Improvelithography propertiesVSAvoidsolvent solubility

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

Iodine atoms are introduced locally at specific positions in the polymeric acid generator units rather than throughout the entire resist system. This localized introduction of iodine provides enhanced EUV absorption and improved lithography properties while minimizing the overall impact on solvent solubility, as the iodine-containing units are distributed as discrete functional groups within the polymer structure rather than as bulk additives.

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

The composition achieves high sensitivity, improved lithography properties, and high contrast with reduced line width roughness and enhanced critical dimension uniformity, suitable for photolithography using high-energy radiation.

Implementation Method 1

a sulfonium salt monomer having a nitro group and an aromatic sulfonate anion

Methodology Applied

Scientific EffectPhotoacid generation: Photodissociation

Implementation Method 2

The so-called polymer-bound acid generator is capable of generating a polymeric sulfonic acid upon exposure and characterized by a very short distance of acid diffusion

Methodology Applied

Scientific EffectAcid diffusion suppression: Diffusion Barrier

Implementation Method 3

iodine atoms are highly absorptive to EUV of wavelength 13.5 nm, and thus generate secondary electrons upon light exposure

Methodology Applied

Scientific EffectEUV absorption: Absorption (EM radiation)

Data Source

PatentUS20260044077A1Sulfonium salt monomer, polymer, chemically amplified resist composition, and pattern forming process

Publication Date: 2026.02.12 SHIN ETSU CHEMICAL CO LTD

AI summary

A sulfonium salt monomer having the formula (A). The sulfonium salt monomer can be used for a chemically amplified resist composition having a high solvent solubility, a high sensitivity, and a high contrast, and being improved in lithography properties such as EL, LWR, CDU, and DOF, particularly when processed by photolithography using high-energy radiation such as KrF excimer laser, ArF excimer laser, an electron beam (EB), or EUV.