Windowless Plasma Source for Broadband VUV Radiation
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Solution Overview
Problem
Current laser-sustained plasma (LSP) radiation sources face challenges due to the short lifetime of transmissive optics under high pressure and temperature conditions, particularly when generating broadband radiation below 190 nm, as they require high-pressure gas chambers and transmissive windows that are prone to damage.
Innovation Solution
The system employs a chamber with a target material source delivering a stream of target material in a non-gaseous form, such as a liquid or solid, to generate plasma, using reflective collection optics to transmit broadband radiation through a windowless aperture, eliminating the need for high-pressure gas chambers and transmissive windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high pressure (30-200 atm) is applied to generate high density plasma, then plasma density is improved, but transmissive optics lifetime deteriorates due to high pressure, high temperature and radiation damage
Solution Approach 1:
The patent extracts the harmful high-pressure environment from the optical path by using a windowless plasma source design. The plasma is generated in a high-pressure chamber, but the radiation is extracted through a windowless aperture, eliminating transmissive optics that would otherwise be damaged by high pressure, temperature, and radiation below 190 nm.
Solution Approach 2:
The patent introduces a windowless aperture as an intermediary between the high-pressure plasma chamber and the external optical system. This aperture allows radiation to pass without requiring transmissive windows that would be damaged by the harsh plasma environment, thus protecting the optical system while maintaining high plasma density.
2Illumination intensity
If transmissive windows are used to transmit broadband radiation below 190 nm, then radiation transmission is improved, but optics reliability deteriorates due to exposure to high pressure, high temperature and radiation
Solution Approach 1:
The patent removes transmissive windows from the system entirely by using a windowless aperture design. The broadband radiation below 190 nm is transmitted through the windowless aperture directly without passing through any transmissive optical elements, eliminating the reliability issues associated with window damage from high pressure, temperature, and radiation exposure.
Solution Approach 2:
The windowless aperture serves as a simple, replaceable opening that does not require maintenance like transmissive windows. If the aperture needs to be replaced, it can be done easily without affecting the entire optical system, making the system more reliable and easier to maintain.
3Power
If high pressure gas chamber is used to sustain plasma, then plasma generation is improved, but device complexity increases due to required transmissive windows and pressure containment structures
Solution Approach 1:
The patent extracts the plasma generation function from the optical path by using a windowless chamber design. The high-pressure plasma is generated in a sealed chamber, but the radiation is extracted through a simple windowless aperture, eliminating the need for complex transmissive window assemblies and pressure containment structures with optical ports.
Solution Approach 2:
The patent replaces the mechanical transmissive window system with a windowless aperture design. This substitution eliminates the need for complex mechanical pressure containment structures that must accommodate optical windows, simplifying the overall device architecture while maintaining effective plasma generation.
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 stabilizes plasma generation, extends the lifetime of optics, and enables efficient collection of high-density broadband radiation, including VUV and DUV, with reduced mechanical complexity and maintenance costs.
Implementation Method 1
generate broadband radiation via formation of a plasma by excitation of the target material
Implementation Method 2
pump radiation from the pump source is sufficient to generate broadband radiation via formation of a plasma
Implementation Method 3
the one or more focusing optical elements are configured to focus the pump radiation into the plasma-forming region
Implementation Method 4
the one or more reflective collection optical elements are configured to collect a portion of the broadband radiation from the plasma
Data Source
AI summary
A system for generating broadband radiation is disclosed. The system includes a target material source configured to deliver one or more of a liquid or solid state target material to a plasma-forming region of a chamber. The system further includes a pump source configured to generate pump radiation to excite the target material in the plasma forming region of the chamber to generate broadband radiation. The system is further configured to transmit at least a portion of the broadband radiation generated in the plasma-forming region of the chamber out of the chamber through a windowless aperture.