Overlay Error Correction via Offset Compensation
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Solution Overview
Problem
Current overlay measurement techniques in photolithographic processes for semiconductor manufacturing often result in measurement deviations, leading to overlay errors due to detection tool errors and differences in refractive indexes, which affect the accuracy of relative position measurements between successive layers.
Innovation Solution
A method that involves capturing overlay mark information from first and second mark patterns on different layers, calculating offset values to compensate for detection errors, and generating corrected deviation values to improve measurement accuracy by using these offset values to adjust the measured positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current overlay measurement techniques are used, then overlay measurement can be performed, but measurement precision deteriorates due to detection tool errors and refractive index differences
Solution Approach 1:
The patent introduces an intermediary calculation process that uses offset values derived from first mark patterns as a mediator to correct the positions of second mark patterns. This intermediary offset calculation eliminates the need to directly measure problematic second mark patterns, thereby removing the source of measurement errors while still enabling overlay measurement between layers.
Solution Approach 2:
The patent extracts and separates the problematic measurement elements (second mark patterns affected by refractive index differences and detection errors) from the reliable measurement elements (first mark patterns). By taking out the unreliable measurements and replacing them with calculated offset values from reliable measurements, the system achieves accurate overlay measurement without the harmful effects.
2Measurement precision
If overlay measurement is performed on successive layers, then relative position information can be obtained, but measurement precision deteriorates due to detection errors
Solution Approach 1:
The patent segments the overlay measurement process into distinct stages: measuring reliable first mark patterns to obtain offset values, then using these offset values to calculate positions of second mark patterns. This segmentation allows the system to perform measurements in a controlled sequence, reducing the impact of detection errors on final results.
Solution Approach 2:
The patent performs preliminary measurement of first mark patterns before measuring second mark patterns. The offset values obtained from this preliminary action are then used to correct subsequent measurements, ensuring that the most accurate reference data is established first to minimize error propagation.
Data Source
AI summary
A method of correcting an overlay error includes the following steps. First, an overlay mark disposed on a substrate is captured so as to generate overlay mark information. The overlay mark includes at least a pair of first mark patterns and at least a second mark pattern above the first mark patterns. Then, the overlay mark information is calculated to generate an offset value between two first mark patterns and to generate a shift value between the second mark pattern and one of the first mark patterns. Finally, the offset value is used to compensate the shift value so as to generate an amended shift value.