EUV Plasma Emission Center Stabilization via Pulsed Cooling
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Solution Overview
Problem
In EUV lithography, the stability of the plasma emission center is compromised due to thermal expansion of electrodes during pulsed operation, leading to shifting of the EUV hot spot, which affects imaging quality.
Innovation Solution
The method involves applying at least two consecutive pulses of energy, such as laser pulses, with controlled time delays and pulse energies to stabilize the plasma emission center, using real-time monitoring and feedback control to maintain the position within a few tens of micrometers, compensating for electrode expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pulsed electrical discharges are used to generate EUV radiation, then productivity is improved, but the position of the plasma emission center becomes unstable due to thermal expansion of electrodes
Solution Approach 1:
The patent applies preliminary cooling to the electrode surface before each pulsed discharge to compensate for anticipated thermal expansion. By pre-cooling the electrode surface in the region where plasma will be generated, the system counteracts the thermal expansion that would otherwise cause the plasma emission center to shift, thereby maintaining position stability while enabling high-productivity pulsed operation
Solution Approach 2:
The patent implements a feedback control system that monitors the position of the plasma emission center and adjusts the cooling power applied to the electrode surface accordingly. When the emission center shifts due to thermal expansion, the feedback system increases cooling in the affected region to restore the plasma to its correct position, enabling stable operation during continuous pulsed discharge cycles
2Productivity
If electrode wheel is operated in pulsed mode, then productivity is improved, but thermal expansion causes continuous movement of plasma position
Solution Approach 1:
The system applies preliminary cooling to the electrode surface before each pulsed discharge cycle to pre-compensate for thermal expansion. This anticipatory cooling maintains the electrode surface temperature and plasma emission center position within acceptable tolerances throughout the pulsed operation sequence, ensuring consistent imaging quality while maintaining high productivity
Solution Approach 2:
The patent dynamically adjusts the cooling power parameter applied to the electrode surface based on the discharge cycle phase and measured plasma position. By varying the cooling power in response to thermal conditions, the system maintains plasma position stability throughout continuous pulsed operation, ensuring reliable imaging quality while sustaining high productivity
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 effectively stabilizes the plasma emission center over multiple discharges, ensuring consistent EUV radiation production and maintaining imaging quality by adjusting the time delay and pulse energy based on measured dependencies.
Implementation Method 1
a gaseous medium is produced at least partly from a liquid material, which is applied to one or several surface(s) moving in said discharge space and is at least partially evaporated by one or several pulsed energy beam(s)
Implementation Method 2
a plasma is ignited in a gaseous medium between at least two electrodes in a discharge space, said plasma emitting said radiation that is to be generated
Implementation Method 3
a plasma is ignited in a gaseous medium between at least two electrodes in a discharge space, said plasma emitting said radiation that is to be generated
Data Source
Figure 1
Figure 2~3
AI summary
The present invention relates to a method and device for generating optical radiation (18), in particular EUV radiation or soft x-rays, by means of electrically operated discharges. A plasma (15) is ignited in a gaseous medium between at least two electrodes (1, 2), wherein said gaseous medium is produced at least partly from a liquid material (6), which is applied to one or several surface (s) moving i the discharge space and is at least partially evaporated by one or several pulsed energy beam(s) (9). At least two consecutive pulses (16) are applied withi a time interval of each electrical discharge onto said surface (s). The delay between and/or the pulse energy of said consecutive pulses is controlled to stabilize the position of an emission center of the plasma (15).