Multi-Step Laser EUV Light Generation Method
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Solution Overview
Problem
Current extreme ultraviolet (EUV) light generation methods face challenges in increasing output energy while maintaining conversion efficiency, as higher energy input leads to reduced efficiency, and increased repetition frequency disrupts droplet position stability, and the expansion of plasma affects etendue limits and debris accumulation on mirrors.
Innovation Solution
The method involves a multi-step process where a droplet is irradiated with first and second laser lights to create a deformed liquid and fragment jet target, which is then irradiated with a third laser light in a direction intersecting the second, allowing for efficient EUV light generation and debris suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher energy input is used to increase EUV light output energy, then productivity is improved, but conversion efficiency deteriorates
Solution Approach 1:
The patent divides the single high-energy laser irradiation process into multiple sequential laser irradiation steps. A droplet is first irradiated to create a deformed liquid target, then irradiated again to generate a fragment jet target, and finally irradiated a third time to produce EUV light. This segmentation allows each laser pulse to perform a specific function, accumulating the desired effect while avoiding the inefficiencies of single high-energy input.
Solution Approach 2:
The patent applies preliminary actions by creating the deformed liquid target and fragment jet target before the final EUV light generation. These preparatory steps modify the target material's structure and state, making it more susceptible to efficient EUV generation in the final irradiation step, thereby improving overall conversion efficiency.
2Productivity
If increased repetition frequency is used to enhance EUV light output per unit time, then productivity is improved, but droplet position stability deteriorates
Solution Approach 1:
The patent segments the droplet processing into distinct temporal stages with multiple laser irradiations. This segmentation allows sufficient time for each processing step to complete while maintaining droplet stability, enabling higher repetition frequencies without compromising position stability.
3Productivity
If plasma expansion is allowed to increase EUV light generation, then productivity is improved, but etendue limits and debris accumulation on mirrors worsen
Solution Approach 1:
The patent segments the irradiation process into multiple controlled steps, with the final EUV-generating irradiation occurring after the target has been pre-conditioned. This results in a more contained and controlled plasma expansion that generates sufficient EUV light while minimizing debris ejection and accumulation on mirrors.
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 approach enhances EUV light output energy per unit time without lowering conversion efficiency, stabilizes droplet position, and reduces debris accumulation on mirrors, improving overall EUV light generation efficiency and system stability.
Implementation Method 1
irradiating the droplet with first laser light to generate a deformed liquid target
Implementation Method 2
irradiating the deformed liquid target with second laser light to generate a fragment jet target
Implementation Method 3
irradiating at least a part of the fragment jet target with third laser light that propagates in a direction intersecting a propagation direction of the second laser light
Data Source
AI summary
An extreme ultraviolet light generation method according to one aspect of the present disclosure includes outputting a droplet to a first laser light irradiation region that is a region different from a plasma generation region, irradiating the droplet that reaches the first laser light irradiation region with first laser light to generate a deformed liquid target, irradiating the deformed liquid target that reaches a second laser light irradiation region that is a region different from the plasma generation region with second laser light to generate a fragment jet target, and irradiating at least a part of the fragment jet target that reaches the plasma generation region with third laser light that propagates in a direction intersecting a propagation direction of the second laser light.