Iterative Image Shifting for Sub-Pixel Position Determination
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Solution Overview
Problem
Existing methods for determining the position of a structure on a carrier relative to a reference point lack precision, particularly in lithographic mask applications.
Innovation Solution
An iterative method that shifts both structures within a superimposed image until the image distance is below a predetermined maximum value, allowing for sub-pixel accuracy and precise position determination, using a measurement apparatus with a recording device and positioning system to achieve high precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional position determination methods are used, then the measurement process is simple, but the measurement precision is insufficient
Solution Approach 1:
The patent applies dynamics by implementing an iterative shifting process where the recorded structure is dynamically adjusted relative to the reference structure. The measurement process transitions from a static comparison to a dynamic iterative approach, continuously refining the position determination through multiple shifting steps until convergence is achieved, thereby improving precision without requiring complex additional hardware
Solution Approach 2:
The patent implements feedback by using the determined image distance from each iteration as input for the next iteration. The measured position information feeds back into the shifting process, allowing the system to continuously refine and improve its measurement accuracy. This feedback mechanism enables sub-pixel precision by iteratively adjusting the shift amount based on previous measurement results
2Measurement precision
If higher precision position determination is achieved through iterative methods, then measurement precision improves, but measurement time increases
Solution Approach 1:
The patent applies partial action by implementing a convergence criterion that stops the iterative process when the image distance falls below a predetermined threshold. Rather than performing an excessive number of iterations, the method performs only the necessary number of iterations required to achieve the desired precision level, thereby optimizing the balance between measurement time and precision
Solution Approach 2:
The patent changes the parameter of shift amount iteratively, starting with larger shifts and progressively reducing the shift amount as convergence approaches. This parameter change strategy allows the method to quickly approach the solution in early iterations and then refine the position in later iterations, reducing total measurement time while maintaining high precision
Data Source
AI summary
A method is provided for determining the position of a structure on a carrier, relative to a reference point of the carrier, said method comprising the steps of: a) providing an image including a reference structure; b) recording an image of the structure on the carrier by means of a recording device, with a known recording position relative to the reference points; c) superimposing the two images to form one superimposed image; d) determining the image distance of the two structures in the superimposed image; e) shifting the two structures in the superimposed image relative to one another, depending on the determined image distance; f) checking whether the determined image distance is below a predetermined maximum value; wherein, if the image distance is below the maximum value, the method is continued in step g), and, if the image distance is not below the maximum value, steps d)-f) are repeated, taking into account the determined image distance/distances: g) determining the position of the structure relative to the reference point, on the basis of the recording position in step b) and of the image distance/image distances determined in step(s) d).