Metrology Illumination Profiling for Edge-Effect Correction
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Solution Overview
Problem
Overfilled metrology methods in lithographic processes are susceptible to edge effects, which affect the accuracy of measurements due to brighter or less bright regions along the edges of measurement targets, particularly as target sizes decrease.
Innovation Solution
A metrology method that involves obtaining measurement data using multiple illumination profiles, determining parameter of interest values and deviations for each profile, establishing a relationship between these values, and correcting the parameter of interest or selecting a preferred illumination profile to minimize measurement deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If overfilled metrology is used to enable smaller targets and simultaneous acquisition of multiple sub-targets, then measurement capability and productivity are improved, but edge effects increase and measurement precision deteriorates
Solution Approach 1:
The patent segments the illumination into multiple distinct profiles (e.g., central, left, right, top, bottom) and measures each sub-target separately with its corresponding illumination profile. This segmentation isolates the region of interest from the edge effects, allowing accurate measurement of small targets while maintaining the benefits of overfilled metrology.
Solution Approach 2:
The patent applies different illumination profiles to different regions of the target. Each sub-target receives illumination optimized for its specific location, with the illumination profile tailored to minimize edge effects in that particular region. This local quality approach ensures that each measurement is optimized for its specific spatial context.
2Measurement precision
If multiple illumination profiles are used to mitigate edge effects, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal measurement system that can handle multiple target configurations and illumination conditions through a single integrated approach. The same metrology apparatus measures all sub-targets with different illumination profiles, eliminating the need for separate measurement systems for each target type and reducing overall device complexity.
Solution Approach 2:
The patent performs preliminary characterization of edge effects by measuring known reference targets with multiple illumination profiles before measuring actual device targets. This preliminary action allows the system to pre-determine correction factors and optimal illumination profiles, reducing the complexity of real-time measurements and enabling automated correction processes.
Data Source
AI summary
Disclosed is a metrology method. The method comprises obtaining measurement data relating to measurement of at least one target using two or more different illumination profiles; and a respective parameter of interest value for a parameter of interest for each of said two or more different illumination profiles. The method described determining, from said measurement data, a respective measurement parameter deviation value for each of said two or more different illumination profiles, said measurement parameter deviation value describing a deviation in a measurement parameter with respect to a measurement parameter value attributed to a region of interest of said target or a sub-target thereof; determining a relationship for the target between the parameter of interest values and the measurement parameter deviation values; and determining one or both of a corrected parameter of interest value and a preferred illumination profile from said relationship.