Lithography Overlay Correction Using Pre-Exposure Substrate Grouping
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Solution Overview
Problem
Current lithographic processes face challenges in accurately measuring and correcting for overlay and alignment errors, particularly in high-volume manufacturing, where performing full overlay measurements on each substrate is time-consuming and affects throughput.
Innovation Solution
A method and system that determine process corrections for lithographic processes by assigning substrates to groups based on pre-exposure parameter data and applying corrections using post-exposure metrology data, enabling dynamic updating of groups and corrections for improved run-to-run control strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full overlay measurements are performed on each substrate, then measurement precision is improved, but productivity deteriorates due to time consumption
Solution Approach 1:
The patent segments substrates into different groups based on pre-exposure parameter data characteristics. Instead of treating each substrate individually for measurements, substrates with similar characteristics are grouped together, allowing representative measurements to be applied to multiple substrates simultaneously, thus improving throughput while maintaining measurement accuracy.
Solution Approach 2:
The patent performs preliminary classification of substrates into groups based on pre-exposure parameter data before actual overlay measurements are taken. This preliminary action allows the system to predict which substrates will require measurements and which can use group-averaged corrections, reducing the total number of measurements needed and improving productivity.
2Productivity
If group-based corrections are applied, then productivity is improved by reducing measurement time, but measurement precision deteriorates due to averaging effects
Solution Approach 1:
The patent applies local quality by providing different correction approaches for different substrate groups. Substrates in groups with high variability receive individual or representative measurements, while substrates in groups with low variability use group-averaged corrections. This ensures that measurement precision is maintained where needed while productivity is improved where possible.
Solution Approach 2:
The patent dynamically adjusts the correction strategy based on parameters such as group variability, substrate characteristics, and process conditions. By changing parameters like the threshold for group assignment and the criteria for selecting representative substrates, the system optimizes the balance between productivity and measurement precision for different manufacturing scenarios.
3Measurement precision
If extensive historical tracking is implemented, then measurement precision is improved through better data analysis, but device complexity increases
Solution Approach 1:
The patent extracts only the essential pre-exposure parameter data that is most relevant for substrate classification and correction, rather than tracking all possible historical parameters. This extraction of critical data elements reduces the complexity of the data tracking system while maintaining sufficient measurement precision for effective overlay correction.
4Measurement precision
If offline measurements are performed, then measurement precision is improved through comprehensive analysis, but productivity deteriorates due to processing time
Solution Approach 1:
The patent performs preliminary classification and grouping of substrates using pre-exposure parameter data available before the lithographic exposure process. This preliminary action enables the system to prepare correction strategies in advance, allowing measurements and corrections to be applied during or immediately after exposure rather than requiring extensive offline analysis, thus maintaining both precision and productivity.
Data Source
AI summary
A method of determining a correction for a process parameter related to a lithographic process, wherein the lithographic process includes a plurality of runs during each one of which a pattern is applied to one or more substrates. The method of determining includes obtaining pre-exposure metrology data describing a property of a substrate; obtaining post-exposure metrology data comprising one or more measurements of the process parameter having been performed on one or more previously exposed substrates; assigning, based on the pre-exposure metrology data, a group membership status from one or more groups to the substrate; and determining the correction for the process parameter based on the group membership status and the post-exposure metrology data.