EUV Reflector Substrate With Parallel Coolant Channels

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Solution Overview

Problem

Current multilayer reflectors for EUV radiation in lithographic apparatuses suffer from low reflectivity and significant radiation absorption, leading to localized heating and deformation, which causes imaging errors as they are unable to efficiently manage heat transfer due to their design and operational environment.

Innovation Solution

Incorporating a reflector substrate with parallel coolant channels that allow coolant to flow in contact with the reflective surface, enhancing heat transfer and reducing temperature rise without inducing vibrations, by using materials with low thermal expansion and optimizing coolant channel spacing and configuration for uniform temperature profiles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a multilayer reflector is used for EUV radiation, then reflectivity is improved through constructive interference, but radiation absorption increases causing localized heating and temperature rise

Engineering Contradiction:

ImprovereflectivityVSAvoidtemperature rise

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The reflector substrate is segmented into multiple regions with coolant channels distributed throughout, allowing localized heat removal from different areas of the reflector where radiation absorption occurs

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A coolant fluid is introduced as an intermediary substance that flows through channels in the reflector substrate, absorbing heat through thermal conduction and carrying it away from the radiation absorption regions

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If coolant channels are added to the reflector substrate, then heat transfer capacity is improved, but device complexity increases

Engineering Contradiction:

Improveheat transfer capacityVSAvoiddevice complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The coolant channels are merged directly into the reflector substrate structure, combining the cooling function with the existing reflector component rather than adding a separate cooling system

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The reflector substrate serves multiple functions: it provides the structural base for the multilayer reflector, contains the coolant channels for heat removal, and supports the reflective surface, eliminating the need for separate cooling components

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Manufacturing precision

If the beam cross-section is small, then imaging precision for smaller features is improved, but localized heating causes surface deformation

Engineering Contradiction:

Improveimaging precisionVSAvoidsurface deformation

Core Design Contradiction:

Manufacturing precisionVSShape

Solution Approach 1:

Coolant channels are strategically positioned to target the specific regions where the beam impacts the reflector, providing localized cooling exactly where heat generation occurs during high-precision imaging

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent replaces passive mechanical cooling methods with an active fluid-based thermal management system that can precisely control heat removal in response to beam position and intensity

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 solution effectively reduces thermal deformation and maintains image precision by enhancing heat transfer capacity while minimizing vibrations, allowing for increased throughput and smaller feature imaging without surface distortion.

Implementation Method 1

coolant flows in parallel through the coolant channels and in contact with the reflector substrate

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Implementation Method 2

coolant flows in parallel through the coolant channels

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 3

Each period, consisting of a high refractive index layer and a low refractive index layer, has a thickness equal to half the wavelength (λ/2) of the radiation to be reflected so that there is constructive interference between the radiation reflected at the high to low refractive index boundaries

Methodology Applied

Scientific EffectConstructive interference: Interference

Implementation Method 4

These functions have to be performed using reflectors (i.e. mirrors)

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 5

polishing the reflective surface while a pressurised fluid is provided to the coolant channels

Methodology Applied

Scientific EffectPressure: Pressure Increase

Data Source

PatentUS10955595B2Multilayer reflector, method of manufacturing a multilayer reflector and lithographic apparatus

Publication Date: 2021.03.23 ASML NETHERLANDS BV

AI summary

A reflector for EUV radiation, the reflector comprising a reflector substrate and a reflective surface, the reflector substrate having a plurality of coolant channels formed therein, the coolant channels being substantially straight, substantially parallel to each other and substantially parallel to the reflective surface and configured so that coolant flows in parallel through the coolant channels and in contact with the reflector substrate.