EUV Gas Discharge Source with Narrow Intermediate Space
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Solution Overview
Problem
Existing gas discharge sources have a restricted solid angle of radiation emission due to the shadow effect caused by the electrode arrangement, limiting the spread of generated radiation to less than 2π sr, which is desirable for various applications.
Innovation Solution
The gas discharge source features a design with an intermediate space between electrode bodies, reduced to less than 5 mm outside the discharge area, which can be a free gap or filled with insulating material, allowing operation on the left-hand branch of the Paschen curve, preventing flashover and enabling radiation emission in a 2π sr or larger solid angle by reducing shadow effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrode disks are arranged in a vacuum system with narrow interspace to enable high voltage operation, then gas discharge can be triggered effectively, but the solid angle of radiation emission is restricted due to shadow effects from the electrode arrangement
Solution Approach 1:
The electrode system is segmented into a rotating cathode disk and a stationary anode, with the cathode rotating to continuously expose fresh target material. This segmentation allows the discharge to occur at specific locations while radiation can emit in multiple directions, resolving the contradiction between reliable discharge triggering and broad radiation emission angle.
Solution Approach 2:
The cathode is made rotatable to dynamically bring fresh target material into the discharge zone continuously. This dynamic operation ensures consistent discharge reliability while the rotating motion allows radiation to be emitted in various directions, increasing the effective solid angle without compromising the discharge triggering reliability.
2Duration of action of stationary object
If electrode disks rotate through liquid metal reservoirs to provide continuous target material supply, then wear of base material is reduced, but the structure becomes more complex requiring precise alignment and control
Solution Approach 1:
The rotating cathode disk automatically supplies fresh target material to the discharge zone through its rotation through the liquid metal reservoir. This self-service mechanism continuously regenerates the electrode surface without requiring external intervention, extending electrode durability while the simple rotational motion avoids complex structural requirements.
Solution Approach 2:
The system continuously discards the evaporated target material from the discharge zone and recovers it through the liquid metal reservoir, which replenishes the cathode surface. This cycle extends the operational life of the electrode base material while maintaining a relatively simple rotational structure rather than complex multi-component systems.
3Power
If laser beam is focused onto radial outer surface of rotating electrode disk to evaporate target material, then plasma generation is efficient, but the electrode surface is subjected to high thermal load requiring effective cooling
Solution Approach 1:
The continuous rotation of the cathode disk through the liquid metal reservoir provides continuous cooling action on the electrode surface. This continuous motion ensures that heat is constantly dissipated from the laser-irradiated areas, allowing high-power laser operation for efficient plasma generation while preventing thermal accumulation that would require complex cooling systems.
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 design enhances the solid angle of radiation emission, reducing shadow effects and allowing efficient generation and distribution of EUV or soft X-radiation without the need for intricate electrode arrangements, maintaining low wear and efficient energy dissipation.
Implementation Method 1
a laser for emitting a laser beam that is focussed, within a discharge area, onto the radial outer surface of the electrode disk to evaporate target material from the liquid film
Implementation Method 2
a laser for emitting a laser beam that is focussed, within a discharge area, onto the radial outer surface of the electrode disk to evaporate target material from the liquid film
Implementation Method 3
a plasma is generated in an electrode system by means of a pulsed current, which plasma, in the case of a suitable choice of a target material in the discharge area, can be a source of EUV radiation or of soft X-radiation
Implementation Method 4
a plasma is generated in an electrode system by means of a pulsed current
Implementation Method 5
as a result of the rotation of the electrode disks through the metal melt, there is a close thermal contact, enabling the disks heated by the gas discharge to efficiently dissipate energy to the melt
Implementation Method 6
As the electric resistance between the electrode disks and the metal melt is very low, very high currents can be transmitted via the melt to the electrode disks
Data Source
AI summary
The present invention relates to a gas discharge source, for generating EUV radiation and/or soft X-radiation, comprising at least two electrode bodies (110,120), of which a first electrode body (110) comprises a rotatably mounted electrode disk (100). The source further comprises a rotary drive (130) for the electrode disk, a device for applying a liquid film of a target material (140) onto a radial outer surface of the electrode disk (100), and a laser that is focussed, within a discharge area (240), onto the radial outer surface of the electrode disk (100) to evaporate target material. The source is characterized by an intermediate space (160) is formed between the electrode bodies, which intermediate space has a reduced width of <5 mm outside the discharge area (240), which is smaller than the intermediate space in the discharge area. The source enables the generated radiation to be emitted in a simple manner through a larger solid angle, without being shadowed by the electrodes.