Rotating Liquid-Target Light Source With Electric-Field Plasma Boost

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Solution Overview

Problem

Current light source apparatuses for generating EUV light and X-rays, such as LPP-type systems, face challenges in achieving high luminous efficiency and stable operation due to complex configurations and difficulties in maintaining a stable supply of liquid EUV raw materials.

Innovation Solution

A light source apparatus that includes a rotation body, a raw material supply section, and an electric field applying section, where the electric field applying section is set to a potential different from the liquid raw material, applied to the plasma generation area to enhance the luminous efficiency of the plasma generated by an energy beam.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If LPP method light source apparatus is used to avoid debris and simplify configuration, then device complexity is reduced, but it becomes difficult to stably drop and supply tin droplets, making it difficult to stably generate EUV light

Engineering Contradiction:
Improveconfiguration complexityVSAvoidstability of EUV light generation
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent replaces the mechanical droplet ejection system with an electric field-based plasma generation system. Instead of mechanically dropping tin droplets onto a target, the invention uses an electric field to generate plasma from tin vapor, which is then irradiated by a laser beam. This substitution eliminates the mechanical complexity of droplet ejection while maintaining stable EUV light generation through controlled plasma formation.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state and delivery method of the tin raw material. Instead of supplying tin as liquid droplets, the system vaporizes tin and uses an electric field to generate plasma from the tin vapor. This parameter change from liquid droplet to vapor-phase plasma enables stable EUV generation without the mechanical issues of droplet ejection, while also allowing for easier material supply and more consistent plasma formation.

Inventive Principle:
Principle #35Parameter changes

2Productivity

If DPP or LDP method light source apparatus is used to generate plasma through discharge, then EUV light can be generated, but debris caused by EUV raw materials is likely to occur

Engineering Contradiction:
ImproveEUV light generationVSAvoiddebris generation
Core Design Contradiction:
ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the harmful debris generation aspect from the plasma generation process. By using a laser-irradiated plasma approach instead of electrode discharge, the system eliminates the debris that would otherwise be generated from electrode erosion and material deposition during discharge-based plasma generation. This extraction of the harmful element allows for clean EUV light generation without compromising productivity.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent converts the potential harm of material deposition and debris generation into a benefit by using vapor-phase tin that is directly converted to plasma without involving electrodes. The tin vapor serves as a clean raw material that, when converted to plasma via laser irradiation, generates EUV light without producing the harmful debris associated with electrode-based discharge methods. The material that would otherwise be harmful is transformed into a beneficial plasma source.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

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 apparatus improves the luminous efficiency of the plasma, allowing for increased radiation intensity and stability in EUV light and X-ray generation, making it suitable for applications like lithography and inspection systems.

Implementation Method 1

an electric field applying section which applies an electric field to a plasma generation area in which plasma is to be generated by irradiation of the energy beam

Methodology Applied
Scientific EffectElectric field: Electric Field

Implementation Method 2

a laser beam irradiating section which irradiates the liquid raw material supplied to the rotation body with a laser beam

Methodology Applied
Scientific EffectLaser irradiation: Laser

Implementation Method 3

plasma is to be generated by irradiation of the energy beam

Methodology Applied
Scientific EffectPlasma generation: Plasma

Implementation Method 4

a rotation body supplied with the liquid raw material, the rotation body rotating about a rotation axis

Methodology Applied
Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP4255122A1Light source apparatus
Publication Date: 2023.10.04 USHIO INC
  • EP4255122A1 patent drawingFigure 1
  • EP4255122A1 patent drawingFigure 2~3
  • EP4255122A1 patent drawingFigure 4~5

AI summary

A light source apparatus (1), in which an energy beam (EB) transforms a liquid raw material into plasma (P) to extract radiation (R), includes a rotation body (22), a raw material supply section, and an electric field applying section (50). The rotation body (22) is disposed at a position onto which the energy beam (EB) is incident. The raw material supply section supplies the liquid raw material to the rotation body (22). The electric field applying section (50) is set to a potential different from a potential of the liquid raw material that has been supplied to the rotation body (22), and applies an electric field to a plasma generation area (21) in which plasma (P) is to be generated by irradiation of the energy beam (EB).