Substrate Stress Measurement via Feature Position Differences
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Solution Overview
Problem
In lithographic processes, accurately measuring stress in substrates is challenging, especially when the substrate remains flat after processing, making it difficult to predict and correct in-plane distortions, which affects overlay performance and yields in sub-micron semiconductor devices.
Innovation Solution
A method and system for determining stress in substrates by measuring position differences between features within a single exposure image field, calculating local stress and in-plane distortion, and using this data to generate corrections for subsequent patterning steps, thereby improving overlay accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stress measurement is performed by measuring substrate shape (e.g., slope), then stress can be determined in some cases, but this method is not always possible when processing results in a flat substrate
Solution Approach 1:
The patent changes the measurement parameter from substrate shape (slope) to feature position difference. This allows stress measurement to be performed regardless of whether the substrate is flat or curved, as the position difference between features remains a valid indicator of stress even when the substrate surface is flat after processing.
2Manufacturing precision
If extensive measurement operations and advanced alignment models are used to correct non-linear distortions, then overlay accuracy can be improved, but process complexity increases
Solution Approach 1:
The patent extracts the stress measurement capability from complex substrate shape analysis and advanced alignment models. By using a simplified approach that measures only the position difference between features within a single exposure field, it obtains stress information without requiring extensive measurement operations or complex computational models.
3Loss of information
If local stress determination is performed for each measured position difference, then stress distribution can be mapped, but measurement and calculation time increases
Solution Approach 1:
The patent segments the substrate into multiple measurement locations, with each location represented by a feature pair within a single exposure field. By performing local stress determination at each segmented location and compiling the results, it creates a complete stress distribution map efficiently without requiring exhaustive measurement of the entire substrate at once.
Data Source
AI summary
A method and control system for determining stress in a substrate. The method includes determining a measured position difference between a measured position of at least one first feature and a measured position of at least one second feature which have been applied on a substrate, and determining local stress in the substrate from the measured position difference.