EUV Light Source Focus Alignment via Wavefront Feedback
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Solution Overview
Problem
In extreme ultraviolet light source systems, achieving precise alignment of the focus of the light source with the target material is challenging, affecting the efficiency of EUV light generation due to variations in the size and orientation of the detected image of the reflected laser beam with the target focal plane position.
Innovation Solution
An extreme ultraviolet light system comprising a light source, steering system, detection system, wavefront modification system, and controller that steers and focuses the amplified light beam, modifies the wavefront of the reflected laser beam based on the detected image, and adjusts the focal plane position relative to the target material to ensure optimal alignment and EUV light production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focus of the light source is manually aligned with the target material, then the alignment can be adjusted, but the precision and stability of the focal plane position cannot be maintained under varying operating conditions
Solution Approach 1:
The system uses a detection system to monitor the reflected laser beam and provides feedback to a controller, which automatically adjusts the focal plane position. This closed-loop feedback mechanism maintains precise alignment stability despite variations in operating conditions, resolving the contradiction between manual adjustability and operational stability.
Solution Approach 2:
The system performs self-alignment by automatically detecting the reflected laser beam characteristics and adjusting its own focal plane position without external intervention. This self-service capability ensures continuous precision maintenance, overcoming the limitation of manual alignment drift.
2Device complexity
If the focal plane position is fixed, then the system structure is simple, but the conversion efficiency of drive laser input power to EUV power decreases due to misalignment
Solution Approach 1:
The feedback mechanism automatically optimizes the focal plane position to maximize conversion efficiency, ensuring the system operates at peak performance without requiring complex manual intervention. The automated adjustment compensates for drift and maintains optimal energy conversion despite the added control system complexity.
Solution Approach 2:
The system dynamically changes the focal plane position parameter based on detected beam characteristics to maintain optimal conversion efficiency. This adaptive parameter adjustment ensures high energy conversion efficiency without requiring permanently complex mechanical structures.
3Measurement precision
If automated detection and adjustment systems are implemented, then alignment precision is improved, but the device complexity increases
Solution Approach 1:
The detection system serves multiple functions: it detects the reflected laser beam, determines focal plane position, and provides feedback for adjustment. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity while maintaining high alignment precision.
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 solution enables precise alignment of the light source with the target material, enhancing the conversion efficiency of the drive laser input power to EUV power and improving the stability and efficiency of EUV light generation.
Implementation Method 1
detecting an image of a laser beam reflected from at least a portion of the target material
Implementation Method 2
The wavefront modification system is in the path of the reflected laser beam and between the target location and the detection system and is configured to modify the wavefront of the reflected laser beam as a function of a target focal plane position along the propagation direction
Implementation Method 3
The light source produces an amplified light beam traveling along a propagation direction and the steering system steers and focuses the amplified light beam to a focal plane near a target location
Implementation Method 4
converting a material into a plasma state that has an element, for example, xenon, lithium, or tin, with an emission line in the EUV range. In one such method, often termed laser produced plasma ('LPP'), the required plasma can be produced by irradiating a target material
Data Source
AI summary
An extreme ultraviolet light system includes a steering system that steers and focuses an amplified light beam traveling along a propagation direction to a focal plane near a target location within an extreme ultraviolet light chamber, a detection system including at least one detector positioned to detect an image of a laser beam reflected from at least a portion of a target material within the chamber, a wavefront modification system in the path of the reflected laser beam and between the target location and the detection system, and a controller. The wavefront modification system is configured to modify the wavefront of the reflected laser beam as a function of a target focal plane position along the propagation direction. The controller includes logic for adjusting a location of the focal plane of the amplified light beam relative to the target material based on the detected image of the reflected laser beam.