EUV Lithography Filament Cleaning Arrangement

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Solution Overview

Problem

Existing EUV lithography apparatuses face challenges in effectively cleaning reflective optical elements, particularly collector mirrors, due to contamination by target materials and chemical compounds, which reduces reflectivity and lifetime, and existing cleaning methods are inadequate for non-nested mirrors or those with single optically effective surfaces.

Innovation Solution

Arranging at least one filament in direct proximity to the optically effective surface of the reflective optical element, with careful selection of thickness and positioning to minimize optical influence in the far field of the EUV radiation, ensuring effective cleaning while maintaining optical performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If filaments are arranged on the rear side of nested mirror shells, then cleaning effect is achieved, but this approach is not suitable for non-nested mirrors or mirrors with single optically effective surfaces

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidapplicability to different mirror types

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

Instead of placing filaments on the rear side of nested mirror shells as in prior art, the invention inverts the approach by positioning filaments in direct proximity to the optically effective surface of non-nested mirrors. This reversal of the cleaning mechanism placement enables effective cleaning for mirror types that were previously incompatible with rear-side filament arrangements.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If filaments are positioned close to the optically effective surface, then cleaning effect is significantly improved, but optical influence of the filaments increases

Engineering Contradiction:

Improvecleaning effectVSAvoidoptical influence

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention applies local quality by carefully selecting the thickness and positioning of filaments placed near the optically effective surface. The filaments are designed with specific dimensional characteristics (e.g., thickness less than 3 mm, preferably less than 1 mm) and strategic positioning to maximize cleaning effectiveness at the surface while minimizing their optical influence in the far field of reflected EUV radiation.

Inventive Principle:

Principle #3Local quality

3Reliability

If filament thickness is increased, then cleaning coverage is improved, but optical influence in the far field increases

Engineering Contradiction:

Improvecleaning coverageVSAvoidoptical influence in far field

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention utilizes parameter changes by optimizing the thickness parameter of the filaments. The filament thickness is controlled within specific ranges (less than 3 mm, preferably less than 2 mm, more preferably less than 1 mm) to achieve an optimal balance between sufficient cleaning coverage and minimal optical influence on the reflected EUV radiation in the far field.

Inventive Principle:

Principle #35Parameter changes

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

Significantly improves the cleaning effect on reflective optical elements by positioning filaments close to the surface, reducing optical and thermal influences, and maintaining wavefront specifications required for EUV lithography, thus enhancing the reflectivity and longevity of the optical elements.

Implementation Method 1

a filament arrangement for producing a reagent that cleans the optically effective surface, wherein the filament arrangement comprises at least one filament configured as a glow or heating element

Methodology Applied

Scientific EffectGlow discharge: Electric Glow Discharge

Implementation Method 2

at least one filament configured as a glow or heating element

Methodology Applied

Scientific EffectThermal heating: Heating

Implementation Method 3

a reflective optical element having an optically effective surface configured to reflect incident EUV radiation

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS11231658B2Arrangement for an EUV lithography apparatus

Publication Date: 2022.01.25 CARL ZEISS SMT GMBH

AI summary

An arrangement for an EUV lithography apparatus includes a reflective optical element (60) having an optically effective surface (62) configured to reflect incident EUV radiation, and a filament arrangement (65) configured to produce a reagent that cleans the optically effective surface (62). The filament arrangement (65) has at least one filament (66) configured as a glow or heating element. The at least one filament (66) is arranged along the optically effective surface (62) of the reflective optical element (60) wherein a thickness and/or positioning of the at least one filament (66) are/is chosen so as to minimize an optical influence of the at least one filament (66) in the far field of the EUV radiation reflected by the optically effective surface (62).