EUV Lamp Conversion Efficiency via Local Gas Dilution
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Solution Overview
Problem
The conversion efficiency of existing EUV and soft X-ray lamps is low due to high radiation absorption and emission outside the desired wavelength range, limiting their effectiveness in applications like optical lithography.
Innovation Solution
A method and apparatus that locally supply a gas with lower mass elements to the discharge space to reduce the density of evaporated liquid material, specifically using a nozzle to direct the gas to the discharge space or the liquid material, thereby increasing the plasma temperature and enhancing radiation output at desired wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If metal vapor is produced from a metal melt in the discharge space, then the plasma can be generated and EUV radiation can be emitted, but the conversion efficiency of electrical energy into EUV radiation is low due to high radiation absorption and emission outside the desired wavelength range
Solution Approach 1:
The patent applies local quality by introducing a gas with lower mass elements (such as helium or neon) specifically into the discharge space where the plasma is generated. This creates a localized region with optimized composition that reduces radiation absorption and improves conversion efficiency, while the rest of the system maintains its original metal vapor generation process.
Solution Approach 2:
The patent changes the compositional parameter of the gaseous medium by adding lighter elements from a supplied gas to the evaporated metal vapor. This parameter change reduces the average mass number of the plasma constituents, which decreases radiation absorption and shifts emission toward the desired EUV wavelength range, thereby improving conversion efficiency from electrical energy to radiation.
2Loss of energy
If the density of evaporated liquid material in the discharge space is high, then sufficient plasma can be formed, but radiation absorption increases and conversion efficiency decreases
Solution Approach 1:
The supplied gas with lower mass elements acts as an intermediary substance that modifies the plasma environment. These lighter gas atoms intermediate between the heavy metal vapor atoms and the radiation field, reducing the absorption cross-section and facilitating more efficient energy conversion to EUV radiation.
3Loss of energy
If a gas is supplied to the discharge space to reduce density of evaporated material, then conversion efficiency increases, but the gas may diffuse to optical components and cause contamination
Solution Approach 1:
The gas supply is localized to the discharge space region where plasma generation occurs. By confining the gas introduction to this specific local area, the patent achieves the beneficial density reduction for improved efficiency while preventing widespread diffusion to optical components that would cause contamination.
Solution Approach 2:
The patent segments the system into distinct functional zones: a discharge space where gas is supplied to improve plasma efficiency, and separate regions containing optical components that are protected from gas contamination. This spatial segmentation allows the harmful effect of gas diffusion to be avoided while maintaining the beneficial effect in the plasma region.
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 increases the conversion efficiency of EUV and soft X-ray lamps by reducing radiation losses and enhancing plasma temperature, as demonstrated by a 10% increase in efficiency from 2.0 to 2.3% in experiments using tin as the liquid material and oxygen as the supplied gas.
Implementation Method 1
an energy beam evaporates at least part of the liquid material, thereby producing a gaseous medium
Implementation Method 2
a discharge plasma emitting EUV radiation and/or soft X-rays is generated in a gaseous medium
Implementation Method 3
a gas composed of chemical elements having a lower mass number than chemical elements of the liquid material is supplied locally, through at least one nozzle, in a directed manner to the discharge space and/or to the liquid material
Data Source
AI summary
The present invention relates to a method of increasing the conversion efficiency of an EUV and/or soft X-ray lamp, in which a discharge plasma (8) emitting EUV radiation or soft X-rays is generated in a gaseous medium formed by an evaporated liquid material in a discharge space, said liquid material being provided on a surface in the discharge space and being at least partially evaporated by an energy beam (9). The invention also refers to a corresponding apparatus for producing EUV radiation and/or soft X-rays. In the method, a gas (11) composed of chemical elements having a lower mass number than chemical elements of the liquid material is supplied through at least one nozzle (10) in a directed manner to the discharge space and/or to the liquid material on a supply path to the discharge space in order to reduce the density of the evaporated liquid material in the discharge space. With the present method and corresponding apparatus the conversion efficiency of the lamp is increased.