Substrate Edge Positioning Correction in Lithography
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Solution Overview
Problem
Lithographic apparatuses face challenges in accurately positioning substrates near the edge due to unreliable level sensor measurements, leading to defocus and unusable dies, as existing methods like global level contour-based solutions often result in significant errors.
Innovation Solution
A method that involves performing height measurements of the substrate to generate height data, using predetermined correction heights to compute corrected height data, and positioning the substrate based on this corrected data, which includes using additional height data from areas outside the target portion to improve accuracy near the edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If level sensor measurements are used near the substrate edge, then more height data is available for positioning, but the measurement reliability deteriorates due to beams falling outside or in invalid edge areas
Solution Approach 1:
The patent introduces an intermediary computational process that takes unreliable level sensor measurements from edge areas and combines them with reliable measurements from inner areas through interpolation and extrapolation algorithms. This intermediary processing step transforms the unreliable edge data into corrected height information that can be used for accurate positioning, effectively mediating between the quantity of available data and its reliability.
Solution Approach 2:
The system implements feedback by using the known good measurements from inner substrate areas to correct and validate the measurements from edge areas. The corrected height data from inner regions provides feedback that helps identify and compensate for measurement errors in edge regions, improving overall measurement reliability while utilizing all available data.
2Device complexity
If global level contour-based solutions are used for edge positioning, then a simplified approach is provided, but the positioning precision deteriorates due to significant errors up to hundreds of nanometers
Solution Approach 1:
The patent applies local quality by differentiating between inner and edge areas of the substrate, applying different processing strategies to each. Inner areas use direct level sensor measurements while edge areas use corrected data derived from interpolation and extrapolation. This localized approach ensures that each region receives the appropriate level of processing to achieve the required positioning precision.
Solution Approach 2:
The system performs preliminary computational actions by pre-calculating correction factors and interpolation models from reliable inner area measurements before using them to correct edge area measurements. This preliminary processing prepares the data in advance, enabling accurate edge positioning without requiring complex real-time calculations during the actual positioning operation.
3Manufacturing precision
If corrected height data from areas outside the target portion is used, then positioning accuracy near the edge is improved, but the computational complexity increases
Solution Approach 1:
The patent segments the substrate into distinct regions (inner areas with reliable measurements and edge areas requiring correction) and applies different processing methods to each segment. This segmentation allows the system to manage computational complexity by focusing intensive processing only where needed (at the edges) while using simpler methods in the well-behaved inner regions.
Solution Approach 2:
The system applies partial correction by using only the necessary amount of computational processing to achieve the required accuracy. Rather than applying complex corrections to the entire substrate, the method selectively applies interpolation and extrapolation only to edge areas where level sensor measurements are unreliable, avoiding unnecessary computational overhead in regions where simple measurements suffice.
Data Source
AI summary
A method is provided for positioning at least one target portion of a substrate with respect to a focal plane of a projection system. The method comprises performing height measurements of at least part of the substrate to generate height data, using predetermined correction heights to compute corrected height data for the height data. The method further comprises positioning the target portion of the substrate with respect to the focal plane of the projection system at least partially based on the corrected height data.