EUV Radiation Feedback Device for Free Electron Laser Thermal Load Reduction
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Solution Overview
Problem
Free electron lasers (FELs) used in projection exposure systems are large and pose radioactivity disposal challenges due to the electron beam, necessitating a reduction in radiation source size and thermal load while maintaining high EUV power and beam quality.
Innovation Solution
A device that couples out and recouples a portion of the emitted EUV radiation back into the FEL, utilizing grazing incidence mirrors and diffractive optical elements to reduce source size, thermal load, and enhance beam quality, with a self-seeding mechanism for mode-matched seed pulse recoupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a free electron laser is used as a radiation source for projection exposure systems, then high EUV power and beam quality can be achieved, but the radiation source size becomes very large and radioactivity disposal becomes problematic
Solution Approach 1:
The patent extracts the essential function of generating EUV radiation by using a compact laser plasma source instead of a large free electron laser. The radiation source is reduced to a small interaction region where a laser beam focuses on a liquid metal target, extracting only the necessary radiation generation capability while eliminating the large accelerator infrastructure
Solution Approach 2:
The patent introduces a liquid metal jet as an intermediary medium between the laser beam and the radiation generation process. The liquid metal target serves as a mediator that converts laser energy into EUV radiation through plasma formation, enabling a compact source design while maintaining high power output
2Manufacturing precision
If a free electron laser is used to generate EUV radiation, then high beam quality can be achieved, but thermal load on optical components increases
Solution Approach 1:
The patent extracts only the necessary EUV radiation generation from the laser plasma interaction, allowing for better control of thermal conditions. By using a liquid metal jet that continuously flows, the heat is carried away by the moving target material, reducing thermal load on stationary optical components
Solution Approach 2:
The patent changes the physical state and motion parameters of the target material by using a flowing liquid metal jet instead of a static solid target. This dynamic target approach allows the target to absorb and transport thermal energy away from the interaction region, reducing thermal load on optics while maintaining the plasma conditions necessary for high beam quality
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 significantly reduces the radiation source size, minimizes thermal load on optical components, and maintains high EUV power and beam quality, enabling efficient operation and reduced radioactivity disposal issues.
Implementation Method 1
the at least one optical component for coupling out electromagnetic radiation from the beam path and/or the at least one optical component for coupling electromagnetic radiation into the laser source each have a mirror for grazing incidence (GI mirror; grazing incidence mirror)
Implementation Method 2
A diffractive optical element is used in particular to decouple electromagnetic radiation from the beam path
Data Source
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AI summary
An FEL (35) comprises a feedback device (36) for feeding back emitted illumination radiation (5).