EUV Light Source Optical Path Layout for Debris Mitigation
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Solution Overview
Problem
EUV light sources suffer from contamination of optical elements due to debris generated from target materials like xenon, tin, or lithium, leading to reduced EUV light output, despite existing methods that introduce inert gas to mitigate debris, which still result in EUV light absorption and insufficient debris removal.
Innovation Solution
A light source apparatus with a design that includes an exhaust case and optical-path covers to separate the exhaust space from the optical path, using purge gas to direct flow and maintain a high vacuum state, reducing EUV light absorption and enhancing debris removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If inert gas is introduced near the optical path to mitigate debris, then debris removal is improved, but EUV light absorption increases and contamination is not sufficiently reduced
Solution Approach 1:
The patent divides the chamber into distinct regions: a first chamber for target material processing and a second chamber for optical element placement, separated by a window. This segmentation allows inert gas to be introduced only in the first chamber where debris is generated, preventing gas interference with EUV light transmission to optical elements in the second chamber while still providing debris mitigation.
Solution Approach 2:
The window structure serves as an intermediary between the first chamber (where inert gas is introduced) and the second chamber (where optical elements are located). It allows EUV light to pass through from the target material region to the optical elements while blocking the passage of inert gas, thus mediating between debris removal needs and light transmission requirements.
2Object-generated harmful factors
If purge gas is introduced into the optical path, then debris is removed, but EUV light transmission is reduced due to gas absorption
Solution Approach 1:
The optical path is segmented into two separate chambers: the first chamber where purge gas flows to remove debris from target material, and the second chamber where optical elements are protected from gas exposure. This segmentation enables debris removal in the target region while maintaining a clean environment for EUV light transmission in the optical region.
Solution Approach 2:
The window acts as an intermediary that separates the gas-filled first chamber from the vacuum-maintained second chamber. It allows EUV light to pass through to reach optical elements while preventing purge gas from entering the optical path, thus eliminating gas absorption of EUV light while maintaining effective debris removal.
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 apparatus effectively maintains a high vacuum state for EUV light transmission, minimizing absorption and contamination, thereby mitigating the decrease in EUV light output and improving debris removal efficiency.
Implementation Method 1
purge gas introduced through an intake port formed in the optical-path cover is injected from the one end of the optical-path cover toward the target material and discharged through the exhaust port via the exhaust space
Implementation Method 2
a filter disposed at the other end of the optical-path cover or inside the optical-path cover, and the filter being configured to let the EUV light pass therethrough
Implementation Method 3
a collector mirror configured to reflect the generated EUV light
Implementation Method 4
a target material capable of generating EUV light together with plasma when irradiated with laser light
Implementation Method 5
when irradiated with laser light
Data Source
AI summary
A light source apparatus according to an embodiment includes: a target material capable of generating EUV light when being irradiated with laser light; a collector mirror configured to reflect the EUV light; an exhaust case including an outer cover disposed between the target material and the collector mirror, and an exhaust port communicating with an exhaust space formed on a target material side of the outer cover; a cylindrical optical-path cover a diameter of an opening another end being larger than that of an opening at one end; and a filter that is disposed at the other end of the optical-path cover or inside thereof, and configured to let the EUV light pass therethrough.