Lithography Stage Mark Positioning for Fast Readout
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Solution Overview
Problem
Current lithography processes are inefficient in measuring the position of alignment marks due to the need to read out data from the entire image sensing region, which prolongs the measurement time.
Innovation Solution
A lithography apparatus that moves a stage to position the substrate such that the image of the alignment mark is closer to the starting row of data readout, allowing sequential row-based data processing and reducing unnecessary data transfer, thereby shortening the measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If data from the entire image sensing region is read out to measure the alignment mark position, then measurement accuracy is maintained, but measurement time increases
Solution Approach 1:
The patent extracts only the necessary data from the image sensing region for alignment mark measurement. By determining the specific region containing the alignment mark and reading out only that portion rather than the entire image sensing region, the system reduces data transfer time while maintaining measurement accuracy. This is achieved by calculating the alignment mark position based on the readout data from the extracted region.
Solution Approach 2:
The patent performs preliminary actions by pre-determining the region where the alignment mark is located before data readout. The system calculates the expected position of the alignment mark and uses this information to define the readout region in advance, allowing the data readout to start immediately without waiting for entire region data transfer.
2Stability of the object's composition
If the alignment mark is positioned at the center of the image sensing region, then measurement stability is improved, but data readout time increases due to distance from the readout starting point
Solution Approach 1:
The patent applies local quality by optimizing the position of the alignment mark within the image sensing region. Instead of always positioning the alignment mark at the center, the system adjusts its position to be closer to the readout starting point (e.g., upper left corner), thereby reducing the distance data must be transferred while maintaining sufficient measurement stability through appropriate positioning.
Solution Approach 2:
The patent changes the dimensional consideration from center-based positioning to corner-based positioning optimization. By considering the readout starting point as the reference (typically upper left corner in image sensors), the system repositions the alignment mark in the vertical dimension to minimize the row distance, thereby reducing readout time while maintaining measurement capability.
Data Source
AI summary
A lithography apparatus includes: a stage configured to hold a substrate on which a mark is formed; an image sensor having an image sensing region; a processor configured to read out data concerning an image of the mark on a row basis to obtain a position of the mark; and a controller configured to position the substrate based on the position of the mark. When the processor obtains a position of a first mark on a first substrate, the controller moves the stage with respect to the image sensor such that an image of the first mark is formed closer to a row, from which the processor starts readout of the data, than an image of a second mark on a second substrate on which the pattern has been formed prior to the first substrate.