Coaxial Electrode Plasma Light Source for EUV Generation
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Solution Overview
Problem
Current EUV plasma light sources face challenges in achieving high output and long radiation duration while minimizing heat load and debris contamination, with existing technologies struggling to sustain plasma in a high-temperature, high-density state for microseconds and maintaining a large effective radiant solid angle.
Innovation Solution
A plasma light source utilizing a pair of coaxial electrodes with a radiation environment sustaining device and voltage application system that generates sheet-discharge and converts it into tubular discharge, confining plasma with a magnetic field, and a plasma medium feeder using porous ceramic to supply media continuously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If input energy is increased to achieve high EUV output, then EUV radiation output is improved, but heat load on electrodes and optical system increases causing degradation
Solution Approach 1:
The patent changes the discharge voltage polarity parameter from conventional to inverted polarity, which fundamentally alters the plasma generation mechanism. This parameter change enables direct conversion of electrical energy to plasma energy with superior efficiency, achieving high EUV output without proportionally increasing heat load on electrodes and optical components.
Solution Approach 2:
The patent converts the harmful effect of high input energy (which would normally cause excessive heat load) into a beneficial effect by using inverted polarity discharge. This mechanism directly transforms electrical energy into plasma energy with high efficiency, so that the input energy is utilized effectively for EUV radiation rather than being wasted as heat.
2Loss of energy
If plasma is generated in high-temperature, high-density state for short duration, then EUV radiation efficiency is improved, but radiation duration is insufficient for required output
Solution Approach 1:
The patent enables continuous plasma generation through sustained inverted polarity discharge between coaxial electrodes. Unlike conventional short-pulsed plasma sources, this system maintains continuous plasma in a high-temperature, high-density state, providing uninterrupted EUV radiation for the required duration while preserving high energy conversion efficiency throughout the operation.
3Productivity
If conventional discharge methods are used, then plasma generation is achieved, but effective radiant solid angle is limited and output is insufficient
Solution Approach 1:
The patent transitions from conventional planar or confined discharge geometries to a three-dimensional coaxial electrode configuration. This dimensional change allows plasma to be generated and confined in a volumetric region between the electrodes, significantly increasing the effective radiant solid angle and enabling higher EUV output through enhanced plasma volume and directional radiation.
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 enables stable EUV radiation for microseconds, significantly improving energy conversion efficiency, reducing heat load on electrodes, and increasing the effective radiant solid angle of the plasma light source.
Implementation Method 1
a voltage application device that applies a discharge voltage of an inverted polarity to each of the coaxial electrodes, wherein tubular discharge is formed between the pair of coaxial electrodes, and plasma is confined in an axial direction of the coaxial electrodes
Implementation Method 2
A conversion efficiency (Plasma Conversion Efficiency: P.C.E) from plasma to radiant light in an effective wavelength band (in-band) is represented by the following expression (1): P.C.E (Pinband×τ)/E
Data Source
AI summary
A plasma light source includes a pair of coaxial electrodes 10 facing each other, a radiation environment sustaining device 20 that supplies a plasma medium into the insides of the coaxial electrodes and holds the coaxial electrodes at a temperature and a pressure suitable for plasma generation, and a voltage application device 30 that applies a discharge voltage of an inverted polarity to each of the coaxial electrodes. Tubular discharge 4 is formed between the pair of coaxial electrodes and plasma 3 is confined in an axial direction of the coaxial electrodes.