Semiconductor Overlay Measurement Using Center-of-Symmetry Localization
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Solution Overview
Problem
Current overlay measurement techniques in semiconductor fabrication are unreliable due to reliance on indirect methods using overlay targets and image segmentation, which are prone to errors and require complex design, and lack precision in measuring actual device features.
Innovation Solution
A computerized system that determines overlay measurement by acquiring images of semiconductor layers, identifying symmetric sub-structures, localizing centers of symmetry (COS) for each layer, and calculating the difference between these COS to measure overlay accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If indirect overlay measurement methods using overlay targets and image segmentation are used, then the measurement process can be implemented, but the measurement accuracy and reliability deteriorate due to errors and complex design requirements
Solution Approach 1:
The patent extracts and removes the overlay target structures from the measurement process, transitioning from indirect measurement using separate targets to direct measurement of actual device features. This eliminates the need for complex target design and segmentation processes while improving measurement accuracy.
Solution Approach 2:
The patent inverts the traditional measurement approach by measuring actual device features directly instead of using indirect overlay targets. This reversal of the measurement paradigm simplifies the process and improves reliability by eliminating intermediate steps that introduce errors.
2Reliability
If indirect overlay measurement methods are used, then the measurement can be performed, but the reliability deteriorates due to being prone to errors
Solution Approach 1:
The patent enables the actual device features to serve themselves as the measurement reference, eliminating the need for separate overlay targets. The device structures provide their own symmetry centers for direct overlay measurement, improving both reliability and accuracy by removing error-prone intermediate steps.
3Ease of operation
If complex image segmentation and overlay target design are used, then overlay measurement can be achieved, but the ease of operation deteriorates due to complex procedures
Solution Approach 1:
The patent removes the complex overlay target design and image segmentation steps from the measurement process, achieving direct measurement of device features. This simplification maintains high precision by measuring actual structures rather than indirect targets.
Data Source
AI summary
There is provided a system and method of determining an overlay measurement between a first layer and a second layer of a specimen. The method includes acquiring a first image of a first structure on the first layer and a second image of a second structure on the second layer, obtaining one or more first regions of interest (ROIs) enclosing part of the first structure and one or more second ROIs enclosing part of the second structure, determining one or more first sets of symmetric sub-structures based on the first ROIs and one or more second sets of symmetric sub-structures based on the second ROIs, localizing a first center of symmetry (COS) based on a COS identified for each first set, and localizing a second COS based on a COS identified for each second set, and determining the overlay measurement based on the first COS and the second COS.