Lithography Process Corrections Using Metrology-Based Wafer Grouping
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Solution Overview
Problem
Current lithographic processes face challenges in accurately measuring and correcting overlay and alignment residuals, which are difficult to trace back to their root causes, leading to inefficiencies in run-to-run control strategies and reduced throughput due to the need for extensive measurement operations and time-consuming correction implementation.
Innovation Solution
A method that determines process corrections for lithographic processes by assigning substrates to groups based on pre-exposure metrology data using a trained classifier, allowing for specific corrections to be applied dynamically based on post-exposure metrology data, thereby optimizing run-to-run control strategies and improving overlay performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If full overlay measurement is performed on each substrate to take advantage of wafer level control, then manufacturing precision is improved, but productivity deteriorates due to prohibitive time and throughput loss
Solution Approach 1:
The patent segments substrates into different groups based on pre-exposure metrology data characteristics. Instead of treating each substrate individually with full measurement, substrates are divided into groups (e.g., first group with first characteristics, second group with second characteristics), allowing differential correction strategies that maintain precision while reducing overall measurement burden and improving throughput.
2Manufacturing precision
If extensive measurement operations are performed to achieve accurate overlay and alignment residuals, then manufacturing precision is improved, but loss of time increases due to time-consuming correction implementation
Solution Approach 1:
The patent performs preliminary classification of substrates into groups based on pre-exposure metrology data before the actual exposure and measurement processes. By pre-grouping substrates according to their characteristics, the system prepares correction strategies in advance, reducing the time needed for correction implementation while maintaining accurate overlay and alignment residual measurements.
Solution Approach 2:
The patent implements a feedback mechanism where post-exposure metrology data is used to validate and refine the group-based correction strategies. The system continuously learns from measurement results and adjusts corrections for subsequent substrates, improving precision over time while reducing the need for extensive repeated measurements.
3Manufacturing precision
If per-substrate corrections are implemented to achieve high accuracy, then manufacturing precision is improved, but device complexity increases due to the need for individual substrate analysis and correction management
Solution Approach 1:
The patent reduces complexity by segmenting substrates into a limited number of groups based on key characteristics from pre-exposure metrology data. Instead of managing individual corrections for each substrate, the system applies group-based corrections, significantly simplifying the correction management process while maintaining high precision through targeted group-specific adjustments.
Data Source
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AI summary
Disclosed is a method of determining a correction for a process parameter related to a lithographic process on a substrate and associated apparatuses. The lithographic process comprises a plurality of runs during each one of which a pattern is applied to one or more substrates. The method comprises obtaining pre-exposure metrology data describing a property of the 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 to the substrate, a group membership status from a one or more groups, based on said pre-exposure metrology data; and determining the correction for the process parameter based on said group membership status and said post-exposure metrology data.