Chemically Amplified Resist Composition for EUV Lithography

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Solution Overview

Problem

Current chemically amplified resist compositions face challenges in achieving high resolution and reduced Line Edge Roughness (LER) and Critical Dimension Uniformity (CDU) while being sensitive to inspection light of short wavelengths, leading to defects and poor dimensional uniformity in pattern formation, especially for advanced miniaturization and microfabrication processes.

Innovation Solution

A chemically amplified positive resist composition incorporating an onium salt compound with a specific phenoxide anion, combined with a base polymer and a photoacid generator, where the onium salt compound effectively controls acid diffusion, enhances solubility, and reduces LER and CDU, ensuring the resist pattern is not absorptive to short-wavelength inspection light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional photoacid generators are used to achieve high sensitivity, then exposure sensitivity is improved, but acid diffusion increases leading to poor resolution and high LER

Engineering Contradiction:

Improveexposure sensitivityVSAvoidresolution and LER

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent introduces an onium salt compound as an intermediary substance between the photoacid generator and the polymer. This onium salt acts as a mediator that modulates acid diffusion: it initially allows acid generation for sensitivity but then suppresses excessive diffusion through acid-base interaction, thereby resolving the contradiction between sensitivity and precision

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical parameters of the resist system by incorporating specific onium salt compounds with controlled basicity. This parameter change allows dynamic control of acid diffusion behavior - the onium salt can accept protons to form non-diffusible species, thereby adjusting the effective diffusion length parameter to achieve both sensitivity and precision

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If acid diffusion is suppressed to improve resolution, then LER is reduced, but sensitivity and exposure margin deteriorate

Engineering Contradiction:

Improveresolution and LERVSAvoidsensitivity

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The onium salt compound is pre-incorporated into the resist composition before exposure. Upon exposure, it performs preliminary acid diffusion control by immediately interacting with generated protons, creating a buffer effect that maintains sensitivity while preventing excessive diffusion from the outset

Inventive Principle:

Principle #10Preliminary action

3Productivity

If conventional resist compositions are used for advanced miniaturization, then pattern formation is achieved, but dimensional uniformity (CDU) deteriorates due to acid diffusion

Engineering Contradiction:

Improvepattern formation capabilityVSAvoidCDU

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The onium salt compound creates local quality differentiation in the resist system: in exposed regions, it forms acid-base complexes that locally suppress diffusion, while in unexposed regions, the onium salt remains available to prevent stray acid diffusion. This local control mechanism improves CDU by ensuring uniform pattern dimensions across the entire patterned area

Inventive Principle:

Principle #3Local quality

4Productivity

If high acid strength photoacid generators are used to improve sensitivity, then exposure sensitivity is enhanced, but acid diffusion distance increases leading to poor resolution

Engineering Contradiction:

Improveexposure sensitivityVSAvoidacid diffusion distance

Core Design Contradiction:

ProductivityVSLength of stationary object

Solution Approach 1:

The patent converts the harmful effect of strong acid diffusion into a beneficial effect by using the onium salt compound. The strong acid generated by the photoacid generator first reacts with the onium salt to form a weaker, non-diffusible acid salt, thereby converting the harmful diffusion property into a useful acid-base neutralization reaction that enhances sensitivity without the penalty of excessive diffusion

Inventive Principle:

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

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 resolution, improved LER and CDU, and minimizes defects, allowing for effective inspection with short-wavelength light, making it suitable for advanced micropatterning technologies like EUV or EB lithography.

Implementation Method 1

a base polymer containing a polymer comprising repeat units having the formula (B1) and adapted to be decomposed under the action of acid to increase its solubility in alkaline developer

Methodology Applied

Scientific EffectPhotoacid generation: Photodissociation

Implementation Method 2

an onium salt compound having a specific phenoxide anion... which effectively controls acid diffusion

Methodology Applied

Scientific EffectAcid diffusion control: Absorption (physical)

Data Source

PatentEP4270108A1Chemically amplified positive resist composition and resist pattern forming process

Publication Date: 2023.11.01 SHIN ETSU CHEMICAL CO LTD

Figure 1

AI summary

A chemically amplified positive resist composition is provided comprising (A) an acid diffusion-controlling agent in the form of an onium salt compound having a specific phenoxide anion, (B) a polymer comprising specific repeat units and adapted to be decomposed under the action of acid to increase its solubility in alkaline developer, and (C) a photoacid generator. A resist pattern with a high resolution, reduced LER, and improved CDU is formed. Because of minimal defects, the resist pattern can be inspected with light of short wavelength 300-400 nm.