Laser Beam Controlling Device for EUV Light Generation
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Solution Overview
Problem
In extreme ultraviolet (EUV) light generation systems, the wavefront of the laser beam fluctuates due to heated optical elements, leading to unstable EUV light output, and existing wavefront adjustment methods fail to maintain coincident wavefronts of the laser and guide laser beams post-diffraction, resulting in undesired wavefronts when the laser beam is restarted.
Innovation Solution
A laser beam controlling device with a guide laser device, wavefront adjusters, and a controller that combines and adjusts the wavefronts of the laser and guide laser beams using a beam combiner and monitor, ensuring alignment even after optical element heating and diffraction effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wavefront adjustment is performed using existing methods, then initial wavefront alignment is achieved, but wavefront coincidence is lost after optical element heating and diffraction effects occur
Solution Approach 1:
The system performs preliminary wavefront adjustment using a guide laser beam before the main laser beam operation. The guide laser beam wavefront adjuster pre-aligns the optical path, and the beam combiner merges it with the main laser beam. This preliminary action ensures that when the main laser operates after heating, the wavefronts remain coincident despite thermal effects.
Solution Approach 2:
The beam monitor continuously detects the wavefront coincidence between the guide laser beam and main laser beam. The controller uses this feedback information to dynamically adjust the wavefront adjusters, maintaining alignment stability even when heating causes drift. This closed-loop feedback system resolves the contradiction between initial precision and ongoing stability.
2Productivity
If the laser beam is restarted after heating optical elements, then operation continues, but wavefront fluctuation occurs leading to unstable EUV output
Solution Approach 1:
The guide laser beam acts as an intermediary reference beam that is combined with the main laser beam using the beam combiner. This intermediary allows continuous monitoring of wavefront coincidence via the beam monitor, enabling real-time corrections that maintain EUV output stability during restarts and continuous operation.
Solution Approach 2:
The system dynamically changes the parameters of the wavefront adjusters based on real-time detection. When the laser is restarted or during operation, the controller modifies the adjuster parameters to compensate for thermal drift and maintain wavefront coincidence, ensuring stable EUV generation despite parameter changes in the optical path.
3Measurement precision
If guide laser beam is used for wavefront reference, then alignment accuracy improves, but system complexity increases due to additional optical components
Solution Approach 1:
The beam combiner merges the guide laser beam and main laser beam into a single optical path. This merging allows the system to use the simple guide laser for precise wavefront reference while maintaining the main laser's functionality. The combination achieves high precision without requiring separate complex measurement systems.
Solution Approach 2:
The guide laser beam serves multiple functions: it provides a wavefront reference, enables alignment monitoring via the beam monitor, and acts as a probe for detecting optical path changes. This multi-functionality reduces the need for additional dedicated components, balancing precision requirements with system complexity.
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
Stabilizes the wavefront of the laser beam, maintaining desired focus and output stability by continuously adjusting the wavefronts of both beams, even during restarts, thus enhancing the precision and reliability of EUV light generation.
Implementation Method 1
a beam combiner configured to adjust a travel direction of a laser beam outputted from a laser system and a travel direction of the guide laser beam outputted from the guide laser beam wavefront adjuster to coincide with each other
Implementation Method 2
a guide laser beam wavefront adjuster provided in a beam path of the guide laser beam outputted from the guide laser device
Implementation Method 3
a beam monitor provided in a beam path of both the laser beam outputted from the both beam wavefront adjuster and the guide laser beam outputted from the both beam wavefront adjuster
Data Source
AI summary
A laser beam controlling device may include: a guide laser device; a guide laser beam wavefront adjuster provided in a beam path of the guide laser beam outputted from the guide laser device; a beam combiner configured to adjust travel directions of a laser beam outputted from a laser system and the guide laser beam outputted from the guide laser beam wavefront adjuster to coincide with each other, a both beam wavefront adjuster provided in a beam path of both the laser beam and the guide laser beam outputted from the beam combiner, a beam monitor provided in a beam path of both the laser beam and the guide laser beam outputted from the both beam wavefront adjuster, and a controller configured to control the guide laser beam wavefront adjuster and the both beam wavefront adjuster based on detection results at the beam monitor with respect to both the laser beam and the guide laser beam.