Immersion Lithography Cleaning Tool Sonic Shielding

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Solution Overview

Problem

Immersion lithographic apparatuses face challenges in effectively cleaning the liquid confinement system, leading to contamination and unpredictable effects due to turbulence and debris in the liquid, which can interfere with imaging and damage components.

Innovation Solution

A cleaning tool is introduced, comprising a sonic transducer, a reservoir to hold liquid, and a barrier to shield sonic waves, allowing for effective cleaning of the liquid confinement system without damaging optical elements by preventing sonic waves from reaching the final element through the aperture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a liquid confinement system is used to provide localized liquid supply between the final element and substrate, then imaging precision is improved, but cleaning difficulty increases due to confined space and sensitivity to debris

Engineering Contradiction:

Improveimaging precisionVSAvoidcleaning difficulty

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent extracts the cleaning function from the main lithographic apparatus by introducing a separate cleaning tool with a sonic transducer. This dedicated cleaning device can access the confined space of the liquid confinement system without interfering with the imaging operation, effectively separating the cleaning function from the imaging function.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces mechanical cleaning methods (which would require physical access and contact with delicate components) with sonic vibration-based cleaning. The sonic transducer generates vibrations that propagate through the liquid to dislodge particles, eliminating the need for mechanical contact with the confined liquid space and optical elements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If sonic waves are used to clean the liquid confinement system, then cleaning effectiveness is improved, but optical elements may be damaged by sonic waves reaching through the aperture

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidoptical element damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a liquid medium as an intermediary between the sonic transducer and the optical elements. The liquid confines the sonic waves within the liquid confinement system, allowing effective cleaning while preventing sonic energy from reaching and damaging the optical elements through the aperture.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies sonic vibration locally within the liquid confinement space where particles need to be removed. The sonic transducer is positioned to direct vibrations only into the liquid volume that requires cleaning, while the liquid confinement structure and aperture geometry ensure that sonic energy does not propagate to regions where optical elements are located.

Inventive Principle:

Principle #3Local quality

3Area of stationary object

If liquid is supplied in a bath configuration, then coverage area is improved, but turbulence and debris effects increase leading to unpredictable imaging

Engineering Contradiction:

Improveliquid coverage areaVSAvoidimaging predictability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent segments the liquid supply into a confined, localized volume between the final element and substrate, rather than using a large open bath. This segmentation of the liquid space reduces the overall volume of liquid that can become turbulent, thereby improving imaging predictability while still providing adequate coverage of the exposure area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The liquid confinement system acts as a flexible boundary that contains the liquid in a thin film or confined layer between the final element and substrate. This confinement structure restricts liquid movement and turbulence while maintaining sufficient liquid presence for effective imaging, resolving the contradiction between coverage area and imaging reliability.

Inventive Principle:

Principle #30Flexible shells and thin films

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 solution enables efficient removal of particles and debris from the liquid confinement system, reducing contamination and maintaining the integrity of the optical elements, thereby improving the cleanliness and reliability of the lithographic apparatus.

Implementation Method 1

a sonic transducer; a reservoir configured to hold liquid between the sonic transducer and the surface to be cleaned

Methodology Applied

Scientific EffectSonic wave: Ultrasound

Implementation Method 2

a barrier positioned in the reservoir under the aperture to form, in use, a shield to sonic waves

Methodology Applied

Scientific EffectSonic wave shielding: Acoustic Absorption

Data Source

PatentUS7841352B2Cleaning device, a lithographic apparatus and a lithographic apparatus cleaning method

Publication Date: 2010.11.30 ASML NETHERLANDS BV

AI summary

A cleaning tool to clean a surface of a liquid confinement system of an immersion lithographic apparatus is disclosed, the liquid confinement system having an aperture to allow passage of a beam of radiation therethrough of an immersion lithographic apparatus. The cleaning tool includes a sonic transducer, a reservoir configured to hold liquid between the sonic transducer and the surface to be cleaned, and a barrier positioned in the reservoir under the aperture to form, in use, a shield to sonic waves.