Lithium-Based EUV Target Composition for Debris Reduction
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Solution Overview
Problem
Existing EUV light sources using lithium as a target material suffer from a high rate of debris particle formation due to its low density, which reduces the effectiveness of debris mitigation and degrades optical components.
Innovation Solution
A lithium-based target material with additional elements such as Ag, Au, Bi, Ba, or Sr is used to increase the density, reducing the velocity of debris particles and incorporating debris mitigation techniques like centrifugal force, protective gas flow, and magnetic fields to redirect debris away from the optical path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If lithium is used as target material for EUV radiation generation, then monochromatic radiation and relatively low melting point are achieved, but debris particle formation rate increases due to low density
Solution Approach 1:
The patent uses composite target materials consisting of lithium combined with heavier elements (such as tin, xenon, or other high-density materials) to create a material that maintains lithium's favorable EUV emission properties while adding the mass density of the heavier elements to reduce debris formation rate. This composite approach allows simultaneous achievement of high brightness and low debris generation.
Solution Approach 2:
The patent changes the density parameter of the target material by combining lithium with heavier elements, thereby altering the physical properties of the target to reduce debris particle formation while maintaining the desired EUV radiation characteristics. The composition is optimized to achieve the right balance between density and radiation efficiency.
2Stability of the object's composition
If lithium is used as target material, then practical monochromatic radiation is obtained, but optical component degradation occurs due to debris particles
Solution Approach 1:
By using composite target materials with heavier elements mixed with lithium, the patent reduces the formation of debris particles that would otherwise degrade optical components. The heavier elements in the composite suppress debris generation while lithium maintains the monochromatic radiation quality, thus protecting optical components while preserving radiation stability.
Solution Approach 2:
The patent converts the harmful low-density property of lithium into a benefit by combining it with heavier elements. The heavier elements, which would normally not emit as efficiently at 13.5 nm, actually serve to suppress debris formation and protect optical components, while the lithium component continues to provide the desired monochromatic EUV radiation.
3Object-generated harmful factors
If high-density target material is used, then debris particle velocity decreases and mitigation is improved, but radiation efficiency may be reduced
Solution Approach 1:
The composite material approach allows optimization of the ratio between lithium (for high radiation efficiency) and heavier elements (for low debris velocity). By carefully tuning this ratio, the patent achieves a balance where enough heavy elements are present to reduce debris particle velocity to acceptable levels, while sufficient lithium remains to maintain high EUV radiation efficiency at 13.5 nm.
Solution Approach 2:
The patent optimizes the composition parameters of the composite material to achieve the desired balance between debris suppression and radiation efficiency. The specific ratios of lithium to heavier elements are adjusted to find the optimal point where debris particle velocity is reduced sufficiently without excessively compromising the EUV radiation output.
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 results in a high-brightness, monochromatic EUV radiation source with significantly reduced debris, maintaining optical component integrity and enhancing the source's efficiency and longevity.
Implementation Method 1
irradiating the target by a laser beam; production of laser plasma with droplet Li target
Implementation Method 2
plasma effectively emitting in the EUV (10-20 nm) range; production of radiating lithium plasma
Implementation Method 3
obtain practically monochromatic radiation from a single resonant transition of hydrogen-like Li 2+
Implementation Method 4
redirecting of the droplet fraction of debris particles away from the optical collector and the input window for the laser beam
Implementation Method 5
The intrinsic magnetic field of such a discharge has a gradient that determines the predominant movement of the discharge plasma flow into the region of a less strong magnetic field
Implementation Method 6
suppression of charged particles in the radiation beam
Data Source
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Figure 3A~3B
AI summary
The invention relates to a Li-containing target material designed to create plasma emitting EUV radiation. The target material may be a Li-based composition with at least one further element. As an example, the further element may be selected from the groupcomprising Au, Ag, Bi, Ba, Sr. The composition is configured for increasing the density of the target material multiple times compared to the density of Li. As a result, compared with the Li target, the velocity of the droplet fraction of debris particles may be sharply reduced, which makes it possible to control the direction of its exit from the plasma due to the high velocity of the target. The target material is preferably used in a laser-produced plasma light source. Such light source may have a fast rotating target (for example at least 100 m/s). The target material may allow the creation of compact low-debris EUV light sources with high spectral brightness designed for a wide range of applications.