Laser Optical Gas Purge Using Inert Low-Pressure Flow

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Solution Overview

Problem

Ozone created from oxygen in the presence of a laser beam can be detrimental to optical components in laser sources used in lithographic apparatuses.

Innovation Solution

A gas purge system that supplies a gas, such as nitrogen or helium, into the optical system at a pressure less than atmospheric pressure to remove oxygen and reduce thermal lensing effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If oxygen is present in the optical path of the laser beam, then the laser source can operate with atmospheric composition gas, but ozone is created from oxygen in the presence of the laser beam which is detrimental to optical components

Engineering Contradiction:

Improveatmospheric composition gasVSAvoidozone formation

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent replaces oxygen-containing atmospheric gas with an inert gas (such as nitrogen or helium) in the optical path of the laser source. This inert atmosphere prevents the formation of ozone by eliminating the oxygen that would otherwise react with the laser beam to create harmful ozone molecules, while still allowing the laser source to operate with a gas-filled environment.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

2Ease of operation

If gas is supplied at atmospheric pressure, then the gas purge system is simple to operate, but thermal lensing effects occur which affect laser beam stability

Engineering Contradiction:

Improvegas supply pressureVSAvoidlaser beam divergence

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent changes the pressure parameter of the gas supply from atmospheric pressure to a reduced pressure (e.g., vacuum or partial vacuum conditions). This parameter change reduces the gas density in the optical path, thereby minimizing thermal lensing effects caused by gas heating from the laser beam, and improving the stability of laser beam divergence and duty cycle performance.

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

The gas purge system effectively reduces ozone formation, minimizes thermal lensing, and improves the stability of laser beam divergence and duty cycle performance.

Implementation Method 1

Ozone (O3) created from oxygen (O2) in the presence of the laser beam can be detrimental to optical components in the laser source

Methodology Applied

Scientific EffectOzone formation from oxygen in presence of laser beam: Photo-oxidation

Implementation Method 2

supplies a gas, such as nitrogen or helium, into the optical system at a pressure less than atmospheric pressure to remove oxygen and reduce thermal lensing effects

Methodology Applied

Scientific EffectThermal lensing:

Data Source

PatentUS20250189905A1Gas purge systems for a laser source

Publication Date: 2025.06.12 CYMER INC

AI summary

A laser source includes a laser chamber configured to generate a first laser beam. The laser source further includes an optical system coupled to the laser chamber and configured to receive the first laser beam and output an output laser beam. The laser source also includes a gas purge system. According to some aspects, the gas purge system is configured to supply a nitrogen gas into the optical system at a pressure less than atmospheric pressure. According to some aspects, the gas purge system is configured to supply a helium gas into the optical system.