EUV Light Generator Stray Light Suppression via Focused Optical Path
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Solution Overview
Problem
EUV light generating devices face challenges in accurately measuring the position, velocity, and trajectory of targets due to stray light interference, which affects the precision of target measurement and control in the plasma generation process.
Innovation Solution
The positions of the light source unit and light receiving unit are strategically disposed within the chamber to ensure that at least one of their optical paths passes through the first focus and is included between the first and second limit surfaces, minimizing stray light capture by positioning the illumination light path within the second region and the reflected light path within the first region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light source unit and light receiving unit are disposed to illuminate and measure the target in the plasma generation region, then measurement capability is achieved, but stray light interference increases
Solution Approach 1:
The patent applies dimensional separation by dividing the chamber into multiple regions (first region, second region, third region) along the optical axis. The light source unit is positioned in the second region, the plasma generation region in the first region, and the light receiving unit in the third region. This spatial arrangement ensures that the optical path passes through the first focus point and remains confined between the first and second limit surfaces, effectively separating the measurement optical path from stray light sources.
Solution Approach 2:
The patent introduces the first focus point as an intermediary element in the optical path. By positioning both the light source unit and light receiving unit to share this common focus point, the system creates a defined optical pathway that can be precisely controlled and separated from other light paths, thereby reducing stray light interference while maintaining measurement capability.
2Adaptability or versatility
If the optical path is expanded to allow flexible positioning of light source and receiver, then system adaptability improves, but stray light control becomes difficult
Solution Approach 1:
The patent segments the optical system into distinct functional regions: a first region containing the plasma generation zone, a second region containing the light source unit, and a third region containing the light receiving unit. Each region is spatially separated and controlled independently. The optical path is further segmented by defining specific boundaries (first and second limit surfaces) that confine the light trajectory, allowing flexible yet controlled positioning.
Solution Approach 2:
The patent utilizes the optical axis dimension to achieve adaptability while maintaining control. By positioning components at different locations along the optical axis (light source in second region, receiver in third region, plasma generation in first region) and confining the optical path between specific limit surfaces, the system achieves flexible configuration without compromising stray light control.
3Measurement precision
If the light source unit and light receiving unit share a common focus point, then optical path precision improves, but system complexity increases
Solution Approach 1:
The patent merges the optical paths of the light source unit and light receiving unit by making them share a common first focus point. This consolidation simplifies the overall optical system configuration while maintaining high precision, as both units are aligned to the same focal point rather than requiring separate focus adjustments.
Solution Approach 2:
The first focus point serves as a shared intermediary that simplifies alignment. By designing both the light source unit and light receiving unit to converge at this common focus point, the system reduces the complexity of optical path configuration while achieving high measurement precision through unified focal alignment.
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 effectively suppresses stray light, allowing for high-accuracy measurement and control of the target in the plasma generation region, reducing errors in target position, velocity, and trajectory determination.
Implementation Method 1
The focusing mirror is configured to reflect the extreme ultraviolet light, generated in the generation region, by a reflection surface, and focus the light at a predetermined focal point farther from the reflection surface than the generation region
Implementation Method 2
The reflection surface of the focusing mirror may be formed in a spheroidal face that defines a first focus at the generation region and a second focus at the predetermined focal point
Data Source
AI summary
An extreme ultraviolet (EUV) light generator includes a generation region where a target generates EUV light, a mirror that focuses the EUV light, an illumination light source, and a light receiver to receive reflected light from the target. A reflection surface of the mirror defines first and second focuses at the generation region and a mirror focal point, respectively. A line segment that links a reflection surface outer peripheral edge and the first focus is rotated about an axis through the first and second focuses to form a first limit surface. The line segment and an extended line on the outer peripheral side rotated about the axis forms a second limit surface. At least one of an illumination light optical path and a reflected light optical path from the light source and the light receiver, respectively, passes through the first focus and extends between the first and second limit surfaces.