Foreign Object Detection on Inspection Stages Using Thermal Correction
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Solution Overview
Problem
Existing foreign object detection methods on inspection stages are inadequate in accurately identifying and removing particles that can damage wafers during the inspection process, leading to potential wafer damage and process disruptions.
Innovation Solution
A method and apparatus that utilize a controller to capture reference and inspection images of the stage surface, comparing position information to detect foreign objects based on brightness differences and size thresholds, with functions for particle detection, foreign object determination, and recovery to prevent wafer damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If brightness difference detection is used to identify foreign objects, then detection sensitivity is improved, but false detection increases due to thermal expansion effects
Solution Approach 1:
The patent applies parameter changes by introducing a correction value that compensates for thermal expansion effects. The system calculates a corrected position by adjusting the detected position information with this correction value, thereby eliminating false detections caused by thermal expansion while maintaining high detection sensitivity for actual foreign objects.
Solution Approach 2:
The patent implements feedback by using the correction value derived from reference position information to adjust subsequent position measurements. This feedback mechanism continuously compensates for thermal expansion effects, ensuring accurate foreign object detection even under varying thermal conditions.
2Measurement precision
If position information comparison is used to detect foreign objects, then detection precision is improved, but processing time increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values based on reference position information before actual foreign object detection. This allows the system to quickly adjust position measurements during inspection without performing complex calculations in real-time, thereby reducing processing time while maintaining high precision.
3Measurement precision
If thermal expansion correction is applied to position data, then measurement accuracy is improved, but system complexity increases
Solution Approach 1:
The patent uses an intermediary approach by introducing a correction value as a mediator between the raw position information and the final corrected position. This correction value acts as a simple adjustment factor that bridges the thermal expansion effect and the measurement system, providing accurate compensation without significantly increasing system complexity.
Data Source
AI summary
A method of detecting a foreign object on a stage according to one aspect of the present disclosure includes acquiring first position information of a first pattern included in a first image in a reference state of a surface of the stage capable of attracting an object to be inspected; acquiring second position information of a second pattern included in a second image of the surface, the second image being obtained after obtaining the first image; and detecting one or more foreign objects on the surface by comparing the first position information and the second position information.