Optical Hollow Waveguide Purging With Reverse Gas Flow

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Solution Overview

Problem

Existing optical hollow waveguide assemblies face challenges in maintaining reliability and compact design while effectively purging contaminants, particularly in extreme ultraviolet (EUV) environments, which can compromise the integrity of the waveguide cavity and illumination optics units.

Innovation Solution

A novel optical hollow waveguide assembly design that generates a continuous purge gas flow from the waveguide output to the input, eliminating the need for additional connectors and openings, and utilizes a purge gas flow direction counter to the illumination light propagation to effectively clean the waveguide cavity, using hydrogen gas to generate free charge carriers that remove contaminants.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If purge gas is supplied from the waveguide input to the waveguide output, then the waveguide cavity can be purged, but additional purge gas connectors and openings are required which complicate the main body structure and reduce manufacturing precision

Engineering Contradiction:

Improvepurging reliabilityVSAvoidwaveguide cavity manufacturing precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional purging direction by supplying purge gas from the waveguide output to the waveguide input instead of the usual input-to-output direction. This reversal eliminates the need for additional purge gas connectors at the input end, simplifying the main body structure and enabling more precise manufacturing of the waveguide cavity while maintaining effective purging functionality

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If additional purge gas connectors and waveguide openings are added, then purging functionality is improved, but the device complexity and installation space requirements increase

Engineering Contradiction:

Improvecontaminant removal effectivenessVSAvoidhollow waveguide assembly complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

By reversing the purge gas flow direction to enter at the output and exit at the input, the patent eliminates the need for additional purge gas connectors and waveguide openings, thereby reducing device complexity while maintaining effective contaminant removal through the waveguide cavity

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The waveguide output serves a dual function: as the exit for illumination light and as the entry point for purge gas. This multi-functionality reduces the need for separate dedicated purge gas connectors, simplifying the overall assembly structure

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Device complexity

If the waveguide cavity is not effectively purged, then the structure remains simple, but contaminations from the EUV source compromise the integrity of the waveguide cavity

Engineering Contradiction:

Improvewaveguide assembly structureVSAvoidwaveguide cavity integrity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The reversed purging direction creates an effective gas flow that pushes contaminants away from the waveguide cavity walls and toward the input end, where they can be evacuated without requiring additional structural complexity, thereby maintaining both simple structure and cavity integrity

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent establishes an inert hydrogen gas atmosphere within the waveguide cavity to protect against contaminations from the EUV source. The continuous flow of hydrogen gas from output to input maintains this protective environment while keeping the structural design simple

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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 design ensures reliable purging and maintains the integrity of the waveguide cavity, allowing for homogeneous illumination light transmission, while optimizing the use of installation space and reducing mechanical stress on components.

Implementation Method 1

The waveguide cavity is purged by the purge gas against the flow

Methodology Applied

Scientific EffectPurging:

Implementation Method 2

The hydrogen gas can then interact with the illumination light supplied to the waveguide cavity, in particular the deep ultraviolet (DUV) light or the EUV light, whereby free charge carriers arise which remove the contaminations

Methodology Applied

Scientific EffectPhotoionization: Photoionisation

Data Source

PatentUS20260029573A1Optical hollow waveguide assembly, illumination optics unit and inspection apparatus

Publication Date: 2026.01.29 CARL ZEISS SMT GMBH

AI summary

An optical hollow waveguide assembly comprises an optical hollow waveguide for guiding illumination light, having a main body having a continuous waveguide cavity having a waveguide input and a waveguide output, wherein a waveguide cavity inner wall of the waveguide cavity is designed to be highly reflective for the illumination light at least under grazing incidence. The hollow waveguide assembly furthermore comprises a waveguide purging device for purging the waveguide cavity with a purge gas, comprising a purge gas connector and at least one nozzle disposed fluidically downstream of the purge gas connector in order to supply the purge gas, at least indirectly, to the waveguide output, in order to generate a purge gas flow from the waveguide output to the waveguide input.