Lithography Alignment Mark Asymmetry Mode Identification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current alignment sensors in lithographic apparatuses face challenges in accurately measuring alignment marks due to imperfections that result in wavelength/polarization-dependent variations, requiring multiple illumination conditions for correction, which is not always efficient.
Innovation Solution
A method to identify dominant asymmetry modes in alignment marks by obtaining alignment data under various conditions, determining orthogonal components, and using sensitivity metrics to identify dominant modes, allowing for improved measurement accuracy without the need for arbitrary user selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple illumination conditions are used to correct wavelength/polarization dependent variations, then measurement accuracy is improved, but measurement time and process complexity increase
Solution Approach 1:
The patent extracts and identifies only the dominant asymmetry modes from the complete set of possible asymmetry modes. By performing modal analysis to determine which modes contribute most significantly to measurement variations, the system focuses correction efforts only on these dominant modes rather than addressing all possible modes, thereby reducing the number of illumination conditions required while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the approach from using multiple illumination conditions to using modal analysis parameters. Instead of varying illumination conditions extensively, the system transforms the problem into identifying dominant modes through mathematical analysis of alignment data, then applies correction based on these identified modes, reducing the need for multiple illumination measurements.
2Measurement precision
If multiple illumination conditions are used to correct asymmetry, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential information needed for correction by identifying only the dominant asymmetry modes. This extraction process simplifies the measurement system by focusing on the most significant modes rather than requiring complex multi-illumination setups to address all possible asymmetry sources.
Solution Approach 2:
The patent transforms the complex multi-illumination correction problem into a parameter-based modal analysis approach. By changing from an illumination-condition-based correction method to a mode-based correction method, the system reduces device complexity while maintaining measurement precision.
3Ease of operation
If arbitrary user selection of asymmetry modes is used, then device operation is simple, but measurement accuracy deteriorates
Solution Approach 1:
The patent implements feedback through automated modal analysis that objectively determines dominant asymmetry modes based on alignment data. The system provides feedback on which modes are dominant and applies corrections based on this analysis, eliminating the need for arbitrary user selection while maintaining ease of operation through automation.
Solution Approach 2:
The system performs self-service by automatically identifying dominant asymmetry modes through modal analysis without requiring user intervention or arbitrary selection. The alignment sensor and processing system work together to autonomously determine which modes to correct, improving measurement accuracy while keeping operation simple.
Data Source
AI summary
A method of identifying one or more dominant asymmetry modes relating to asymmetry in an alignment mark, the method includes obtaining alignment data relating to measurement of alignment marks on at least one substrate using a plurality of alignment conditions; identifying one or more dominant orthogonal components of the alignment data, the one or more dominant orthogonal components including a number of orthogonal components which together sufficiently describes variance in the alignment data; and determining an asymmetry mode as dominant if it corresponds to an expected asymmetry mode shape which best matches one of the one or more dominant orthogonal components. Alternatively, the method includes, for each known asymmetric mode: determining a sensitivity metric; and determining an asymmetry mode as dominant if the sensitivity metric is above a sensitivity threshold.