Lithography Substrate Rotational Shift Measurement
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Solution Overview
Problem
In lithography processes, especially for substrates with FOWLP where individual chips are arranged, the rotational shift error between the notch and the average lattice of chips leads to alignment marks falling outside the field of view, causing detection errors due to stray light from wide-area illumination, which existing techniques struggle to adequately address without significantly impacting throughput.
Innovation Solution
A measurement method that captures a first image while rotating the substrate to isolate stray light, a second image with the substrate still to capture the scribe line, and a third image by correcting the second image with the first, allowing for accurate determination of the scribe line position and rotational shift amount, thereby reducing stray light influence without requiring pre-optimized corrected images for each substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wide-area illumination such as bar illumination is used to detect the scribe line accurately in a wide field of view, then the detection accuracy is improved, but stray light enters the scope and causes detection error
Solution Approach 1:
The patent captures an image of the scribe line before the actual measurement process. This preliminary image is then used to calculate a correction value that compensates for stray light effects during the subsequent measurement, thereby maintaining detection accuracy without requiring complex real-time stray light elimination
Solution Approach 2:
The patent uses the captured scribe line image to calculate a correction value that is fed back into the measurement system. This correction value is applied to compensate for stray light interference in subsequent measurements, creating a feedback loop that maintains measurement accuracy despite the presence of stray light
2Measurement precision
If the field of view of the alignment scope is expanded to bring the alignment mark into the field of view, then the alignment mark can be detected, but the stroke of the substrate stage in the rotational direction may lack when the rotational amount is large
Solution Approach 1:
The patent performs preliminary detection of the scribe line and calculation of the correction value before the substrate transfer process. This allows the alignment mark to be pre-positioned within the field of view through rotational correction, eliminating the need for large rotational strokes during actual transfer and reducing transfer time
Solution Approach 2:
The patent changes the rotational position parameter of the substrate based on the detected scribe line position and calculated correction value. By adjusting this parameter in advance, the alignment mark is positioned optimally within the field of view, reducing the required rotational stroke during substrate transfer and improving productivity
3Object-affected harmful factors
If a representative corrected image is obtained in advance to reduce stray light influence, then the stray light effect is reduced, but the influence changes for each difference in material or orientation making it insufficient
Solution Approach 1:
The patent makes the system self-adaptive by capturing the scribe line image and calculating the correction value specific to each substrate's actual conditions. This self-service approach allows the system to automatically adjust to different substrate materials and orientations without requiring pre-optimized corrected images for each variant
Solution Approach 2:
The patent dynamically changes the correction value parameter based on the actual substrate conditions detected during measurement. Instead of using a fixed representative corrected image, the system calculates a unique correction value for each substrate based on its specific material properties and orientation, thereby adapting to variations while maintaining stray light reduction
4Object-affected harmful factors
If corrected images are obtained for each lot or for each substrate to reduce stray light influence, then the stray light effect is sufficiently reduced, but the time required to obtain the corrected images is not realistic from the viewpoint of throughput
Solution Approach 1:
The patent performs the image capture and correction value calculation as a preliminary action during the existing measurement process. By integrating this preliminary action into the standard measurement workflow rather than adding it as a separate step, the system obtains substrate-specific correction values without significantly increasing total processing time, thereby maintaining high throughput
Solution Approach 2:
The patent merges the stray light correction process with the existing scribe line detection and measurement process. Instead of obtaining corrected images as a separate preliminary step, the system combines image capture, scribe line detection, and correction value calculation into a single integrated measurement workflow, thereby reducing total processing time and maintaining high throughput
Data Source
AI summary
The present invention provides a measurement method of measuring a rotational shift amount of pattern regions arranged on a substrate with respect to a reference portion provided at an outer edge of the substrate, including obtaining a first image by capturing a target region including a target object on the substrate during detecting a position of the reference portion while rotating the substrate, obtaining a second image by capturing the target object in a state in which the substrate remains still, obtaining a third image indicating a difference between the first image and the second image by correcting the second image with the first image, and obtaining a position of the target object based on the third image and obtaining the rotational shift amount of the pattern regions with respect to the reference portion based on the obtained position of the target object.