Lithographic Pupil Image Delta Analysis for Dose Contribution
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Solution Overview
Problem
Current methods for determining the contribution of a processing apparatus to the fingerprint of a parameter across a substrate are time-consuming, computationally extensive, and prone to inaccuracies, particularly in achieving critical dimension uniformity in semiconductor fabrication.
Innovation Solution
A method involving the creation of delta images from pupil images with different dose sensitivities, determining the rate of change in response to dose variations, and using this information to calculate the contribution as effective dose values, which can be used to generate an effective dose map and pure process map for improved calibration and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional metrology methods are used to determine the combined fingerprint by measuring parameters in the post-processed substrate and comparing to libraries of functions, then measurement capability is provided, but the process is time-consuming, computationally extensive, and prone to inaccuracies
Solution Approach 1:
The patent applies preliminary action by measuring the fingerprint during the lithographic exposure process itself, rather than waiting for post-processing steps to complete. The system captures pupil images at multiple dose levels during exposure and processes this data in real-time to determine the contribution of the lithographic apparatus to the fingerprint, eliminating the need for time-consuming post-processing measurements and comparisons.
Solution Approach 2:
The patent uses copying by creating a digital representation (pupil image) of the exposure process parameters and using this copy to determine the fingerprint contribution. Instead of physically measuring the final substrate parameters after all processing steps, the system creates and analyzes a digital copy of the exposure data, which is much faster and more accurate.
2Measurement precision
If conventional metrology methods are used to determine the combined fingerprint, then measurement capability is provided, but the process is computationally extensive
Solution Approach 1:
The patent applies the extraction principle by isolating and analyzing only the relevant information from the exposure process - specifically the pupil images at different dose levels - rather than processing the entire complex dataset of post-processed substrate measurements. By extracting and focusing on the critical exposure parameters during the lithographic process itself, the computational burden is significantly reduced while maintaining measurement accuracy.
Solution Approach 2:
The patent segments the fingerprint determination process into separate contributions from different processing steps, specifically isolating the lithographic apparatus contribution from other process steps. This segmentation allows for targeted analysis of the exposure process parameters without needing to re-analyze the entire complex fabrication process, reducing overall computational complexity.
3Measurement precision
If conventional metrology methods are used to determine the combined fingerprint, then measurement capability is provided, but significant inaccuracies occur
Solution Approach 1:
The patent implements feedback by continuously monitoring and analyzing the pupil images during the lithographic exposure process and using this real-time information to determine the fingerprint contribution. The system compares the actual exposure data with expected values and provides immediate feedback on deviations, allowing for more accurate and reliable measurement compared to post-processing methods that rely on indirect comparisons to library functions.
Solution Approach 2:
The patent applies preliminary action by determining the fingerprint contribution during the exposure process itself, before other processing steps occur. This timing ensures that the measurement reflects the actual exposure conditions without being affected by subsequent process variations, thereby improving both accuracy and reliability of the measurement.
Data Source
AI summary
A method for determining a contribution of a processing apparatus to a fingerprint of a parameter across a substrate, the method including: obtaining a delta image which relates to a difference between a first pupil image associated with inspection of a first feature on the substrate and a second pupil image associated with inspection of a second feature on the substrate, wherein the first and second features have different dose sensitivities; determining a rate of change of the difference in response to a variation of a dose used to form the first and second features; selecting a plurality of pixels within the delta image having a rate of change above a predetermined threshold; and determining the contribution using the determined rate of change and the delta image restricted to the plurality of pixels.