EUV Mask Capping Layer Ion-Assisted Deposition

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Solution Overview

Problem

The durability of extreme ultraviolet (EUV) masks in EUV lithography is a challenge, as they are prone to pattern placement shifts and have limited throughput due to their susceptibility to oxidation and chemical etchants.

Innovation Solution

The development of ion-assisted deposition processes for forming an amorphous capping layer over the reflective multilayer stack of EUV masks, which reduces intermixing and diffusion, resulting in a more durable and stronger capping layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional capping layer is formed over the reflective multilayer stack, then the mask can be manufactured, but the capping layer is susceptible to oxidation and chemical etchants, reducing durability

Engineering Contradiction:

Improvedurability of capping layerVSAvoidsusceptibility to oxidation and chemical etchants

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the structural parameters of the capping layer by forming an amorphous structure through ion-assisted deposition. This amorphous structure has different physical and chemical properties compared to crystalline structures, resulting in enhanced resistance to oxidation and chemical etchants while maintaining manufacturing feasibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure by combining the amorphous capping layer with the reflective multilayer stack through ion-assisted deposition. The ion assistance during deposition creates a composite material system where the capping layer and underlying stack are intimately bonded with reduced intermixing, improving overall durability and chemical resistance

Inventive Principle:

Principle #40Composite materials

2Duration of action of stationary object

If the capping layer has a crystalline structure, then it can be formed easily, but it has more grain boundaries that increase oxygen diffusion and reduce longevity

Engineering Contradiction:

Improvelongevity of EUV maskVSAvoidease of forming capping layer

Core Design Contradiction:

Duration of action of stationary objectVSEase of manufacture

Solution Approach 1:

The patent changes the structural state parameter of the capping layer from crystalline to amorphous through ion-assisted deposition. This parameter change eliminates grain boundaries while the ion assistance during deposition ensures proper adhesion and density, achieving both enhanced longevity and manufacturing feasibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces conventional deposition mechanisms with ion-assisted deposition. The ion assistance provides kinetic energy and directional control during deposition, enabling the formation of dense amorphous structures without requiring post-deposition thermal processing or other complex mechanical interventions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If traditional deposition processes are used, then the manufacturing process is simple, but the capping layer has intermixing and diffusion that reduce its strength and durability

Engineering Contradiction:

Improvestrength of capping layerVSAvoidcomplexity of deposition process

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent replaces traditional thermal or physical vapor deposition with ion-assisted deposition. This substitution uses ion bombardment during deposition to control atomic arrangement, eliminate intermixing, and create a dense, strong capping layer structure that would be difficult to achieve with simpler processes

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

The amorphous capping layer formed by the ion-assisted processes is denser with fewer grain boundaries, making it more durable and resistant to oxygen diffusion, thereby improving the longevity and throughput of EUV masks.

Implementation Method 1

The capping layer is formed by an ion-assisted ion beam deposition or an ion-assisted sputtering process

Methodology Applied

Scientific EffectIon beam deposition: Physical Vapour Deposition

Implementation Method 2

The capping layer is formed by an ion-assisted ion beam deposition or an ion-assisted sputtering process

Methodology Applied

Scientific EffectSputtering: Sputtering

Implementation Method 3

The amorphous capping layer is denser with fewer grain boundaries, making it more durable and resistant to oxygen diffusion

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS12265322B2EUV mask blank and method of making EUV mask blank

Publication Date: 2025.04.01 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An extreme ultraviolet mask including a substrate, a reflective multilayer stack on the substrate and a capping layer on the reflective multilayer stack is provided. The reflective multilayer stack is treated prior to formation of the capping layer on the reflective multilayer stack. The capping layer is formed by an ion-assisted ion beam deposition or an ion-assisted sputtering process.