Cyclic Sulfonium Acid Generator for EUV Resist LWR

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Solution Overview

Problem

As feature sizes in microelectronic devices decrease, image blurs due to acid diffusion become a significant issue, leading to a tradeoff between sensitivity and line width roughness (LWR) or critical dimension uniformity (CDU) in EUV resist materials.

Innovation Solution

The use of a sulfonium or iodonium salt containing a sulfone anion with a straight linkage of two iodized or brominated aromatic groups as an acid generator, which directly excites the acid generator upon radiation exposure, minimizing the influence of secondary electron diffusion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If acid diffusion is reduced by lowering PEB temperature, then LWR or CDU is improved, but sensitivity becomes lower

Engineering Contradiction:

ImproveLWRVSAvoidsensitivity

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent changes the chemical structure of the acid generator from conventional onium salts to cyclic sulfonium salts with specific structural features (formula 1), which fundamentally alters the acid generation mechanism. This structural parameter change enables direct EUV photon absorption and eliminates the need for thermal diffusion, thereby resolving the tradeoff between LWR and sensitivity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the thermal diffusion mechanism (mechanical/thermal process) with a direct photochemical acid generation mechanism. By using cyclic sulfonium salts that directly absorb EUV photons to generate acids without requiring thermal energy, the invention substitutes the thermal field with a direct optical-to-chemical energy conversion process, eliminating acid diffusion and resolving the sensitivity-LWR contradiction

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If acid diffusion is reduced by adding more quencher, then LWR or CDU is improved, but sensitivity becomes lower

Engineering Contradiction:

ImproveCDUVSAvoidsensitivity

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent extracts and eliminates the acid diffusion step from the conventional chemically amplified resist mechanism. By using cyclic sulfonium salts that generate acids directly at the absorption site without diffusion, the invention removes the need for quenchers to control acid spread, thereby improving CDU without sacrificing sensitivity

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention replaces the chemical quenching mechanism with a direct photochemical acid generation mechanism. Instead of using quenchers to chemically neutralize diffusing acids, the cyclic sulfonium salt structure enables direct EUV-to-acid conversion without thermal diffusion, eliminating the need for quenchers and resolving the CDU-sensitivity tradeoff

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If feature size is reduced for higher integration density, then resolution is improved, but image blurs due to acid diffusion become more significant

Engineering Contradiction:

ImproveresolutionVSAvoidimage blurs

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the fundamental parameter of acid generation from thermal diffusion-based to direct photochemical conversion. The cyclic sulfonium salt structure (formula 1) with specific molecular geometry enables direct EUV photon absorption and immediate acid generation at the absorption site, eliminating acid diffusion and preventing image blurs even at reduced feature sizes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention substitutes the thermal diffusion process with direct photochemical acid generation. By using cyclic sulfonium salts that convert EUV photons directly into acids without requiring thermal energy or diffusion, the patent eliminates the harmful acid diffusion effect that causes image blurs, enabling higher resolution at smaller feature sizes

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach results in a resist composition with high sensitivity, improved LWR or CDU, high contrast, high resolution, and a wide process margin, independent of whether it is a positive or negative tone resist.

Implementation Method 1

an acid is generated by exposure to high-energy radiation such as EB or EUV. Upon EB or EUV exposure, a polymer is ionized to generate secondary electrons whose energy is transferred to the acid generator to generate an acid

Methodology Applied

Scientific EffectPhotoionization: Photoionisation

Implementation Method 2

secondary electrons whose energy is transferred to the acid generator to generate an acid as they diffuse

Methodology Applied

Scientific EffectElectron diffusion: Diffusion

Data Source

PatentUS20250102912A1Resist composition and pattern forming process

Publication Date: 2025.03.27 SHIN ETSU CHEMICAL CO LTD

AI summary

The resist composition comprises an onium salt of sulfonic acid which has a linkage of two iodized or brominated aromatic groups as the acid generator. The resist composition offers a high sensitivity, reduced LWR and improved CDU independent of whether it is of positive or negative tone. A pattern can be formed by using the resist composition.