EUV Photolithography Mask Laser Treatment for CD Control

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Solution Overview

Problem

Existing methods for treating EUV photolithography masks with multilayer systems face challenges such as collateral damage, multilayer system compaction, and registration impact, leading to reduced reproducibility and accuracy in critical dimension control, especially when using backside illumination.

Innovation Solution

A method involving two distinct pulsed laser irradiations with different δR/δREG ratios is employed to treat the multilayer system, allowing for precise control of reflectivity changes and registration changes, minimizing compaction and registration impact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If backside illumination is used to treat the multilayer system, then immunity to absorber pattern load is achieved, but high intensity-related unwanted side effects occur including multilayer system compaction and registration impact

Engineering Contradiction:

Improveimmunity to absorber pattern loadVSAvoidmultilayer system compaction and registration impact

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The illumination is segmented into two distinct wavelength components: a first wavelength (e.g., 193 nm) that provides immunity to absorber pattern load, and a second wavelength (e.g., 248 nm) that compensates for the compaction and registration effects. This segmentation allows each wavelength to address specific problems independently while working together to achieve overall process optimization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The illumination source uses a composite approach by combining two different wavelength sources (dual-wavelength illumination). This composite illumination strategy leverages the complementary properties of each wavelength: the first wavelength for pattern-load immunity and the second wavelength for effect compensation, thereby resolving the technical contradiction between reliability and harmful factors.

Inventive Principle:

Principle #40Composite materials

2Device complexity

If single wavelength illumination is used, then process simplicity is maintained, but inability to simultaneously optimize δR and δREG occurs

Engineering Contradiction:

Improveillumination system simplicityVSAvoidsimultaneous optimization of δR and δREG

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The illumination system is designed with multi-functionality by incorporating two wavelength sources that serve different purposes: one wavelength optimizes reflectivity change (δR) while the other optimizes registration change (δREG). This universal illumination approach allows a single system to achieve multiple optimization goals that would be impossible with a single wavelength, thereby improving manufacturing precision without excessive complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Manufacturing precision

If frontside illumination is used, then direct treatment of multilayer system is achieved, but reflectivity suppression and absorber pattern influence occur

Engineering Contradiction:

Improvedirect multilayer system treatmentVSAvoidreflectivity suppression and absorber pattern attenuation

Core Design Contradiction:

Manufacturing precisionVSLoss of energy

Solution Approach 1:

The treatment process is segmented into two illumination steps using different wavelengths. The first wavelength (193 nm) provides pattern-load immunity from the backside, while the second wavelength (248 nm) applies frontside illumination to directly treat the multilayer system. This segmentation allows direct treatment benefits to be achieved without suffering from the full burden of absorber pattern attenuation, as the two wavelengths complement each other's advantages.

Inventive Principle:

Principle #1Segmentation

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 achieves better resolution and overall quality of EUV photolithography masks by optimizing δR and δREG simultaneously, reducing compaction and registration effects, and enabling higher precision in critical dimension uniformity.

Implementation Method 1

providing a first pulsed laser irradiation with at least one first pulse parameter and providing a second pulsed laser irradiation with at least one second pulse parameter

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

directing the first irradiation and the second irradiation into and/or onto the multilayer system, wherein the first irradiation and the second irradiation differ in a reflectivity change (δR)/registration change (δREG) ratio induced in the EUV photolithography mask

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentEP4636477A1EUV CD control by modification of ml reflectivity using laser treatment

Publication Date: 2025.10.22 CARL ZEISS SMS GMBH

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AI summary

A method for treating a multilayer system of an extreme ultraviolet photolithography mask, the method comprises providing a first pulsed laser irradiation with at least one first pulse parameter, providing a second pulsed laser irradiation with at least one second pulse parameter, and directing the first pulsed laser irradiation and the second pulsed laser irradiation into and/or onto the multilayer system, wherein the first pulsed laser irradiation and the second pulsed laser irradiation differ in a refelctivity change (δR) / registration change (δREG) ratio induced in the EUV photolithography mask.