EUV Laser Focusing Layout for Common Target Irradiation
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Solution Overview
Problem
Existing focusing devices for generating extreme ultraviolet (EUV) radiation in lithography suffer from reduced efficiency due to laser beams being focused at different positions in the target region from different directions, leading to ineffective irradiation of the target material.
Innovation Solution
A focusing device with a first and second focusing element for each laser beam, aligned approximately parallel or congruent with the optical axis of a reflective optical element, ensuring effective irradiation of a moving target material by aligning the image planes perpendicularly to the reflective optical element's axis, allowing for efficient EUV radiation generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If laser beams are focused onto the target material at different positions from different directions, then the target material can be irradiated from multiple angles, but the irradiation efficiency is reduced and the EUV radiation generation becomes less effective
Solution Approach 1:
The patent merges multiple laser beams into a common focal region on the target material. By aligning the optical axes of multiple focusing elements to be substantially parallel or congruent with the optical axis of the reflective optical element, the laser beams are focused at the same or substantially the same position, creating a unified irradiation zone that maximizes EUV radiation generation efficiency while maintaining multi-beam capability
Solution Approach 2:
The patent introduces asymmetry in the optical configuration by aligning optical axes parallel to the reflective optical element's axis rather than using symmetric convergence from multiple directions. This asymmetric arrangement ensures that all laser beams focus at the same position on the target material, eliminating the efficiency loss associated with distributed focal points while still allowing multiple beams to contribute to EUV generation
2Manufacturing precision
If optical axes of focusing elements are aligned parallel or congruently with the reflective optical element's axis, then the image planes are aligned perpendicularly to the optical axis enabling effective irradiation, but the configuration becomes more constrained
Solution Approach 1:
The patent creates an equipotential optical configuration where all optical axes are aligned parallel or congruently with the reflective optical element's axis. This establishes a uniform reference frame that simplifies the alignment of image planes perpendicular to the optical axis, ensuring that all focusing elements operate at the same optical potential and produce consistent focal positions on the target material
Solution Approach 2:
The patent designs the optical system with universal alignment characteristics where the parallel/congruent optical axis configuration serves multiple functions simultaneously: it aligns image planes perpendicular to the optical axis, ensures common focal positioning for multiple laser beams, and maintains compatibility with the reflective optical element. This universal configuration reduces the number of separate alignment requirements while achieving multiple precision goals
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
This configuration enables more efficient and distortion-free irradiation of the target material, improving the generation of EUV radiation by ensuring the laser beams are effectively superimposed and aligned with the target material's trajectory, thereby enhancing the overall irradiation process.
Implementation Method 1
a first focusing element for focusing a first laser beam onto the target material at a first position in the target region, a second focusing element for focusing a second laser beam onto the target material at a second position in the target region
Implementation Method 2
a reflective optical element for reflecting the EUV radiation generated by the target material
Data Source
AI summary
A focusing device for focusing at least two laser beams onto a moving target material in a target region for generating extreme ultraviolet (EUV) radiation is provided. The focusing device includes a first focusing element for focusing a first laser beam onto the target material at a first position in the target region, a second focusing element for focusing a second laser beam onto the target material at a second position in the target region, and a reflective optical element for reflecting the EUV radiation generated by the target material. An optical axis of the first focusing element and/or an optical axis of the second focusing element are aligned approximately parallel or congruently with respect to an optical axis of the reflective optical element.