EUV Target Measurement Apparatus with Movable Sensor
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Solution Overview
Problem
Current extreme ultraviolet (EUV) light generation systems face challenges in accurately measuring and positioning targets due to measurement impossible regions caused by uneven light, dust, and pixel variations, leading to unstable EUV light energy and inaccurate measurements.
Innovation Solution
A target measuring apparatus and EUV light generation system that includes an image capturing unit, a moving unit, and a control unit to capture images of targets, move the image capturing unit to avoid measurement impossible regions, and update the coordinate system information, ensuring accurate target parameter measurement and stable EUV light generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the image capturing unit is fixed in position, then the device complexity is reduced, but measurement precision deteriorates due to measurement impossible regions caused by uneven light, dust, and pixel variations
Solution Approach 1:
The image capturing unit is made movable instead of fixed, allowing dynamic repositioning to avoid measurement impossible regions. The moving unit enables the image capturing unit to change its position based on the detected target position and the distribution of measurement impossible regions, thereby achieving accurate measurements while maintaining relatively simple device structure.
2Measurement precision
If the image capturing unit is moved to avoid measurement impossible regions, then measurement precision is improved, but device complexity increases due to the addition of moving unit and coordinate system update mechanisms
Solution Approach 1:
A feedback mechanism is implemented where the control unit receives information about measurement impossible regions and target positions, determines optimal image capturing positions, and controls the moving unit to position the image capturing unit accordingly. This automated feedback loop improves measurement precision while managing device complexity through intelligent control rather than purely mechanical solutions.
Solution Approach 2:
The patent replaces complex mechanical positioning systems with a combination of image processing and coordinate system transformations. Instead of requiring precise mechanical positioning hardware, the system uses software-based coordinate updates to track and compensate for the movement of the image capturing unit, thereby reducing mechanical complexity while maintaining measurement precision.
3Measurement precision
If the image capturing unit moves during target output, then measurement precision is improved by avoiding measurement impossible regions, but productivity decreases due to the time required for movement and coordinate updates
Solution Approach 1:
The system performs preliminary determination of the optimal image capturing position before actual image capture. The control unit calculates the appropriate position based on target output position and measurement impossible region distribution in advance, allowing the moving unit to pre-position the image capturing unit, thereby minimizing delays and maintaining high measurement speed while ensuring precision.
Solution Approach 2:
The system maintains continuous operation by coordinating the movement of the image capturing unit with the target output process. The control unit continuously updates the image capturing position based on real-time target position information, ensuring that the image capturing unit is always positioned optimally without interrupting the measurement workflow, thus maintaining both precision and productivity.
Data Source
AI summary
A target measuring apparatus includes: an image capturing unit configured to capture a picture image of a target output from a target supply unit; a moving unit configured to move at least a part of the image capturing unit; and a control unit configured to perform a first process of updating information on a coordinate system in the picture image based on an amount of movement of the image capturing unit by the moving unit, and a second process of measuring a parameter of the target based on the image captured by the image capturing unit and the information on the coordinate system. Updating the information on the coordinate system can calibrate a deviation of a measurement result of the target due to movement of the image capturing unit.