Diffraction-based pupil determination for optimization of lithographic processes
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Solution Overview
Problem
Current lithographic processes face challenges in reproducing patterns with dimensions smaller than the classical resolution limit, necessitating sophisticated fine-tuning steps like NA optimization and optical coherence settings, but these methods struggle to effectively handle high-NA systems with central obscuration, which affect EUV mirror coatings and light transmission.
Innovation Solution
A method is developed to determine a pupil with a central obscuration for high-NA lithography systems by analyzing diffraction orders and patterns, optimizing the source and mask using source-mask-optimization (SMO) to exclude the central obscuration and enhance light transmission, while accounting for physical constraints and desired process windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If NA optimization and optical coherence settings are used to reproduce patterns smaller than the classical resolution limit, then manufacturing precision is improved, but device complexity increases due to the need for sophisticated fine-tuning steps
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing diffraction patterns for various pupil configurations in a lookup table before the actual lithography process. This allows the system to quickly retrieve and apply optimized parameters without performing complex real-time calculations, thereby maintaining high manufacturing precision while reducing device complexity and process time
Solution Approach 2:
The patent uses copying by creating diffraction patterns computationally and storing them as reference data. These copied diffraction patterns are then applied during lithography to guide the formation of sub-resolution features, eliminating the need for complex physical trial-and-error tuning while achieving precise pattern reproduction
2Use of energy by moving object
If a pupil with central obscuration is used in high-NA systems, then light transmission is improved, but manufacturing precision deteriorates due to diffraction effects affecting EUV mirror coatings
Solution Approach 1:
The patent converts the harmful diffraction effects caused by central obscuration into a beneficial tool by explicitly calculating and incorporating these diffraction patterns into the pupil design. The known diffraction effects are used to shape the pupil function in advance, allowing the system to achieve both high light transmission and precise pattern formation by accounting for rather than avoiding the diffraction effects
Solution Approach 2:
The patent applies parameter changes by modifying the pupil function parameters based on pre-calculated diffraction patterns. The system adjusts the pupil transmission function to compensate for diffraction effects, changing the distribution of light in the pupil plane to achieve optimal pattern formation while maintaining high light transmission through the centrally obscured high-NA system
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves light transmission and pattern reproduction in high-NA systems, enhancing the resolution and efficiency of lithographic processes by optimizing the source and mask configuration, thereby addressing the limitations of existing methods.
Implementation Method 1
determining a diffraction order (DO) based on a target design and a mask model; determining a first diffraction pattern (DP) based on the DO and the first pupil
Data Source
AI summary
Methods, apparatuses, and software are disclosed for optimization of a source and/or mask as used in lithographic manufacturing and patterning processes. One method includes determining a first pupil having a central obscuration (CO), determining a diffraction order (DO) based on a target design and a mask model, determining a first diffraction pattern (DP) based on the DO and the first pupil, the first DP including overlapping regions of diffracted light, determining a second DP based on the DO and the first pupil, and determining an initial pupil based on the first DP and the second DP, the initial pupil including at least some of the overlapping regions.