Laser Beam Direction Control for EUV Light Generation
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Solution Overview
Problem
Existing EUV light generating systems face challenges in accurately adjusting the position and angle of CO2 laser beams due to overlapping periods of burst signal emission and image acquisition, leading to incorrect feedback control and potential misalignment of the laser beam within the EUV light generating apparatus.
Innovation Solution
A laser device configuration including a light source for burst operation, an optical sensor to acquire cross-sectional images, an image processor to output beam-related information, and a controller to adjust the beam traveling direction based on this information, ensuring overlap between image acquisition and emission periods to prevent incorrect feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the optical sensor acquires cross-sectional images during burst signal emission periods, then the image acquisition efficiency is improved, but the feedback control accuracy deteriorates due to overlapping periods causing incorrect beam position detection
Solution Approach 1:
The system performs preliminary separation of the image acquisition period from the burst signal emission period. The controller is configured to acquire cross-sectional images during periods that do not overlap with burst signal emission, ensuring accurate beam position detection before the beam is emitted. This preliminary action prevents the harmful overlap effect while maintaining efficient operation cycles.
Solution Approach 2:
The operational cycle is segmented into distinct non-overlapping phases: an image acquisition phase where the optical sensor detects the laser beam position, and a burst emission phase where the laser beam is generated and directed. This segmentation eliminates the overlap problem by creating clear temporal boundaries between measurement and action phases.
2Speed
If the image acquisition period overlaps with the burst signal emission period, then the system operation speed is improved, but the feedback control reliability deteriorates leading to incorrect beam adjustment
Solution Approach 1:
The system performs preliminary beam position measurement during the image acquisition period before the burst signal emission begins. By acquiring cross-sectional images and determining beam position in advance, the system ensures reliable feedback control information is available before the high-power beam is emitted, preventing any reliability issues from overlapping operations.
Solution Approach 2:
The system employs periodic alternating phases of image acquisition and burst emission. Each complete cycle consists of a non-overlapping image acquisition period followed by a burst emission period, creating a rhythmic operational pattern that maintains both speed and reliability through regular, predictable timing sequences.
3Manufacturing precision
If the laser beam is emitted in burst operation with frequent adjustments, then the beam alignment accuracy is improved, but the system complexity increases due to coordinated control of multiple components
Solution Approach 1:
The system implements a feedback control mechanism where the optical sensor detects the actual laser beam position during image acquisition, compares it with the desired position, and the controller adjusts the beam direction based on this feedback information. This closed-loop feedback enables high beam alignment accuracy while managing complexity through intelligent control algorithms that coordinate the light source and beam direction adjuster based on real-time measurements.
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 configuration reduces the likelihood of the CO2 laser beam being entered into the EUV light generating apparatus from an incorrect position, enhancing the accuracy of beam alignment and reducing errors in feedback control.
Implementation Method 1
an optical sensor configured to acquire a cross sectional image of the laser beam during a certain period for every certain cycle
Implementation Method 2
a beam traveling direction adjuster configured to adjust a traveling direction of the laser beam
Data Source
AI summary
A laser device may include a light source configured to emit a laser beam in burst operation, an optical sensor configured to acquire a cross sectional image of the laser beam during a certain period for every certain cycle, an image processor configured to receive an input of an image signal of the cross sectional image outputted from the optical sensor and output beam relating information about the laser beam, a beam traveling direction adjuster configured to adjust a traveling direction of the laser beam, and a controller configured to control the beam traveling direction adjuster based on the beam relating information when at least a part of a period in which the optical sensor acquires the cross sectional image is overlapped with a period in which the light source emits a laser beam.