Fiducial Pattern Alignment Using Model Matching and Center Refinement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional photolithography techniques face challenges in accurately identifying and aligning fiducial patterns due to manufacturing variations and imperfections in fiducial markings, such as laser-drilled holes, which affect precise positioning during substrate exposure.
Innovation Solution
A method involving model matching and shaping techniques is employed to identify individual fiducial markings, using normalized cross-correlation and median circle fit algorithms to refine the center position, thereby improving alignment robustness and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment techniques are used to identify fiducial patterns, then the alignment process is simple and fast, but the precision and robustness of alignment are reduced due to manufacturing variations and imperfections in fiducial markings
Solution Approach 1:
The alignment process is divided into multiple stages: initial template matching to locate fiducial markings, followed by gradient magnitude optimization to precisely determine center positions. This segmentation allows each stage to focus on specific aspects of the problem, improving overall precision without requiring a completely complex system redesign.
Solution Approach 2:
The patent applies preliminary template matching to obtain rough center positions of fiducial markings before performing the more computationally intensive gradient magnitude optimization. This preliminary action reduces the search space and provides a good initial estimate, making the subsequent precision optimization more efficient and manageable.
2Measurement precision
If template matching is used to locate fiducial markings, then the process is computationally efficient, but the accuracy of center position determination is reduced due to manufacturing variations
Solution Approach 1:
Template matching is used as a preliminary step to obtain rough center positions of fiducial markings. This initial estimation is computationally efficient and provides a good starting point for the subsequent gradient magnitude optimization, reducing the computational burden of achieving high precision.
Solution Approach 2:
The patent replaces simple template matching with gradient magnitude optimization to determine the true center positions of fiducial markings. This substitution uses image gradient information rather than direct template correlation, providing more accurate center detection that is robust to manufacturing variations and imperfections in the fiducial markings.
Data Source
AI summary
A photolithography machine with an alignment system is described. The photolithography machine can identify a fiducial pattern provided on a substrate and use the location of the fiducial pattern to align the substrate before exposure. The fiducial pattern can include a plurality of fiducial markings arranged in a specified pattern. A model matching technique can be applied to match the respective individual fiducial markings. A shaping technique can then be used to identify the fiducial pattern based on the matched fiducial markings.