EUV Light Source Return Light Blocking Unit
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Solution Overview
Problem
The existing EUV light source devices face inefficiencies in EUV generation due to unstable operation of the second laser source caused by return light from the first laser beam, leading to fluctuations in the timing of the second laser beam emission and reduced EUV generation efficiency.
Innovation Solution
Incorporating a return light blocking unit, such as an optical isolator, to prevent return light from reaching the second energy beam emitting unit, ensuring stable operation and optimal timing of the second energy beam emission, thereby stabilizing EUV light generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the first laser beam is emitted to vaporize the raw material, then the discharge is triggered between two electrodes, but the reflected first laser beam (return light) may be incident to the second laser source causing unstable laser oscillation
Solution Approach 1:
The patent extracts and removes the harmful return light from the optical path by introducing a return light blocking unit (optical isolator) that blocks the reflected first laser beam from reaching the second laser source, thereby preventing unstable laser oscillation while maintaining the vaporization and discharge process
Solution Approach 2:
The patent introduces an optical isolator as an intermediary component between the first laser source and the second laser source. This intermediary blocks the harmful return light while allowing the optical path to remain functional for the intended laser beam transmission
2Productivity
If the timing of the second laser beam is optimized for EUV generation, then EUV radiation efficiency is maximized, but any shift in timing due to unstable laser oscillation causes efficiency drop
Solution Approach 1:
The patent removes the source of timing instability by blocking the return light that causes unstable laser oscillation in the second laser source, thereby ensuring consistent and precise timing for EUV generation
Solution Approach 2:
The patent implements a feedback mechanism where the timing of the second laser beam is controlled based on the timing of the first laser beam and the discharge timing, ensuring that the second laser beam is emitted at the optimal moment for EUV generation while compensating for any timing variations
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
The solution effectively suppresses unstable operation of the second energy beam emitting unit, ensuring efficient and stable EUV light emission by maintaining precise timing of the energy beams, enhancing EUV generation efficiency.
Implementation Method 1
a first laser source that irradiates a raw material, which is delivered onto an electrode, with a first laser beam, to vaporize the raw material thereby triggering the discharge between two electrodes
Implementation Method 2
a second laser source that, after irradiating the raw material with the first laser beam and before triggering the discharge between the two discharge electrodes, irradiates the raw material on the discharge electrode in that region which is irradiated with the first laser beam, with a second laser beam to further vaporize the raw material
Implementation Method 3
applies a high voltage across a pair of electrodes, which are supplied with a discharge gas containing an extreme ultraviolet light emission seed, to generate high-density and high-temperature plasma upon electric discharge
Implementation Method 4
The timing of emitting the second laser beam is decided from optimal timing that is obtained in advance by experiments conducted on the basis of the distance between the two electrodes and pulse power, which is applied to between the two electrodes. However, if the laser oscillation of the second laser source becomes unstable, then the timing of emitting the second laser beam shifts from the optimal timing
Data Source
AI summary
An extreme ultraviolet light source device that can stably and efficiently provide EUV emission. The EUV light source device includes a first laser source that irradiates a high-temperature plasma raw material with a laser beam, and a second laser source that, after the high-temperature plasma raw material is irradiated with the laser beam and before effective extreme ultraviolet light is emitted, irradiates the raw material in that region which is irradiated with the laser beam, with a second laser beam. The EUV light source device also includes a return light blocking unit that prevents return light of the laser beam, which is emitted from the first laser source, from reaching a light emission opening of the second laser source.