Plasma and CO2 Snow Cleaning for EUV Tin Deposits

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Solution Overview

Problem

Existing methods for cleaning metallic contaminants from EUV lithography apparatus, such as tin deposits, are inefficient, pose safety hazards, and risk damage to the collectors, requiring lengthy downtime and significant expertise, while carbon dioxide snow cleaning is sub-optimal for thick or firmly adhered contaminants.

Innovation Solution

A method combining atmospheric plasma oxidation and carbon dioxide snow cleaning, with controlled nozzle distance, angle, and rotation, to oxidize and remove metallic contaminants, using multiple cycles and additional cleaning techniques like ultrasonic acid cleaning to enhance efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If carbon dioxide snow cleaning is used, then cleaning speed is improved, but cleaning effectiveness on thick and firmly adhered contaminants deteriorates

Engineering Contradiction:

Improvecleaning speedVSAvoidcleaning effectiveness

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent combines carbon dioxide snow cleaning with atmospheric plasma oxidation to create a hybrid cleaning system. The plasma oxidation step pre-treats thick and firmly adhered metallic contaminants by oxidizing them, making them more susceptible to removal by the subsequent carbon dioxide snow cleaning, thereby achieving both high cleaning speed and high cleaning effectiveness

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The atmospheric plasma oxidation is performed as a preliminary step before carbon dioxide snow cleaning. This preliminary oxidation action converts difficult-to-remove metallic contaminants into more easily removable oxidized forms, enabling the fast carbon dioxide snow cleaning to effectively remove even thick and firmly adhered contaminants

Inventive Principle:

Principle #10Preliminary action

2Reliability

If manual cleaning methods are used, then cleaning effectiveness is improved, but cleaning time and expertise requirements increase

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidcleaning time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The cleaning system is designed to automatically perform both plasma oxidation and carbon dioxide snow cleaning without requiring manual intervention or specialized expertise. The automated sequential process eliminates the need for skilled operators while maintaining high cleaning effectiveness and reducing cleaning time to minutes

Inventive Principle:

Principle #25Self-service

3Reliability

If hydrogen radicals are used to clean tin, then cleaning effectiveness is improved, but safety hazards increase

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidsafety hazards

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the dangerous hydrogen radical method with atmospheric plasma oxidation using air or oxygen, which are safe and readily available. The plasma oxidation effectively converts metallic contaminants to oxidized forms without the safety hazards of hydrogen gas, maintaining cleaning effectiveness while eliminating ignition risks

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The carbon dioxide snow cleaning operates in an inert carbon dioxide atmosphere, which is non-flammable and safe. This replaces the hazardous hydrogen radical environment with a safe inert atmosphere, eliminating safety hazards while maintaining high cleaning effectiveness

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 method significantly enhances the speed and effectiveness of removing thick and firmly adhered metallic contaminants, reducing downtime and maintaining collector integrity, achieving up to 10-100 times faster cleaning than previous techniques.

Implementation Method 1

a first portion of the gas stream passes over the contaminant and oxidises the contaminant

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

passing a stream of carbon dioxide towards the surface to clean at least a portion of the oxidised contaminant from the surface

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 3

providing a stream of gas which substantially surrounds the stream of carbon dioxide, accelerating the stream of carbon dioxide towards the surface

Methodology Applied

Scientific EffectMomentum transfer: Impact Force

Data Source

PatentEP3707560B1Method for cleaning

Publication Date: 2025.12.31 ASML NETHERLANDS BV

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AI summary

A method of cleaning a surface to remove a contaminant therefrom, the method comprising the steps of oxidizing at least a portion of the contaminant and passing a stream of carbon dioxide snow over the contaminant. An apparatus for cleaning a surface, the apparatus comprising at least one carbon dioxide snow outlet, and at least one plasma outlet, and a cleaning head comprising at least one carbon dioxide snow outlet and at least one plasma outlet are also disclosed.